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TABLE OF CONTENTS
INDEX TO FINANCIAL STATEMENTS

As filed with the Securities and Exchange Commission on July 22, 2013

Registration No. 333-189109

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

Amendment No. 3
to

FORM S-1
REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

Athlon Energy Inc.
(Exact name of registrant as specified in its charter)

Delaware
(State or other jurisdiction of
incorporation or organization) 1311
(Primary Standard Industrial
Classification Code Number) 46-2549833
(I.R.S. Employer
Identification Number)

420 Throckmorton Street, Suite 1200
Fort Worth, Texas 76102
(817) 984-8200
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

Robert C. Reeves
President and Chief Executive Officer
420 Throckmorton Street, Suite 1200
Fort Worth, Texas 76102
(817) 984-8200
(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:
Sean T. Wheeler Divakar Gupta Latham & Watkins LLP 811 Main Street, Suite 3700 Houston, Texas 77002 (713) 546-5400	Gerald M. Spedale Jason A. Rocha Baker Botts L.L.P. 910 Louisiana Street Houston, Texas 77002 (713) 229-1234

          Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this Registration Statement.

          If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box: o

          If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

          If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

          If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. o

          Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of "large accelerated filer," "accelerated filer" and "smaller reporting company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer o Accelerated filer o Non-accelerated filer ý
(Do not check if a
smaller reporting company) Smaller reporting company o

CALCULATION OF REGISTRATION FEE

Title of Each Class of Securities to Be Registered	Amount to be Registered(1)	Proposed Maximum Offering Price per Share(2)	Proposed Maximum Aggregate Offering Price(1)(2)	Amount of Registration Fee
Common Common Stock, par value $0.01 per share	18,157,895	$20.00	$363,157,900	$49,535(3)

(1)

Estimated pursuant to Rule 457(a) under the Securities Act of 1933, as amended. Includes 2,368,421 additional shares of common stock that the underwriters have the option to purchase.

(2)

Estimated solely for the purpose of calculating the registration fee pursuant to Rule 457(a) under the Securities Act of 1933, as amended.

(3)

The Registrant previously paid $47,058 of the total registration fee in connection with prior filings of this Registration Statement. Concurrently with the filing of this Amendment No. 3 to the Registration Statement, the Registrant has transmitted $2,477, representing the additional filing fee payable with respect to the $18,157,900 increase in the proposed maximum aggregate offering price set forth herein.

          The registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933 or until this Registration Statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

The information in this prospectus is not complete and may be changed. We and the selling stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state or other jurisdiction where the offer or sale is not permitted.

Subject to Completion, dated July 22, 2013

PROSPECTUS

15,789,474 Shares

Athlon Energy Inc.

Common Stock
$      per share

        This is the initial public offering of our common stock. We are selling 15,789,474 shares of our common stock. We expect the initial public offering price to be between $18.00 and $20.00 per share.

        The selling stockholders named in this prospectus have granted the underwriters an option to purchase up to 2,368,421 additional shares of common stock to cover over-allotments. We will not receive any of the proceeds from the sale of the shares by the selling stockholders.

        We have been approved to list our common stock on the New York Stock Exchange under the symbol "ATHL."

        Investing in our common stock involves risks. See "Risk Factors" beginning on page 18.

        We are an emerging growth company as that term is used in the Jumpstart Our Business Startups Act of 2012, and as such, we have elected to take advantage of certain reduced public company reporting requirements for this prospectus and future filings. See "Risk Factors" and "Prospectus Summary—Emerging Growth Company Status."

        Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

	Per Share	Total
Initial Public Offering Price	$	$
Underwriting Discounts and Commissions(1)	$	$
Proceeds to Athlon Energy Inc. (before expenses)	$	$

(1)

Please read "Underwriting (Conflicts of Interest)" for a description of all underwriting compensation payable in connection with this offering.

        The underwriters expect to deliver the shares to purchasers on or about                        , 2013 through the book-entry facilities of The Depository Trust Company.

Citigroup		Goldman, Sachs & Co.
BofA Merrill Lynch	UBS Investment Bank	Wells Fargo Securities

Barclays Credit Suisse RBC Capital Markets

Scotiabank / Howard Weil Tudor, Pickering, Holt & Co.

Apollo Global Securities CIBC Credit Agricole CIB FBR

Lebenthal Capital Markets Mitsubishi UFJ Securities Simmons & Company
 International Stephens Inc.

                        , 2013

TABLE OF CONTENTS

Prospectus Summary	1
The Offering	10
Summary Consolidated Financial, Reserve and Operating Data	12
Risk Factors	18
Cautionary Note Regarding Forward-Looking Statements	49
Use of Proceeds	51
Dividend Policy	51
Capitalization	52
Dilution	53
Selected Historical Consolidated Financial Data	54
Management's Discussion and Analysis of Financial Condition and Results of Operations	55
Business	82
Management	106
Certain Relationships and Related Party Transactions	124
Corporate Reorganization	130
Principal and Selling Stockholders	132
Description of Capital Stock	134
Shares Eligible for Future Sale	141
Material U.S. Federal Income Tax Consequences to Non-U.S. Holders	143
Underwriting (Conflicts of Interest)	147
Legal Matters	155
Experts	155
Where You Can Find More Information	155
Glossary	G-1
Index to Financial Statements	F-1

You should rely only on the information contained in this prospectus and any free writing prospectus prepared by or on behalf of us or to which we have referred you. Neither we nor the underwriters have authorized anyone to provide you with information different from that contained in this prospectus and any free writing prospectus. We are offering to sell shares of common stock and seeking offers to buy shares of common stock only in jurisdictions where offers and sales are permitted. The information in this prospectus is accurate only as of the date of this prospectus, regardless of the time of delivery of this prospectus or any sale of the common stock.

Industry and Market Data

        The market data and certain other statistical information used throughout this prospectus are based on independent industry publications, government publications or other published independent sources. Some data is also based on our good faith estimates. Although we believe these third-party sources are reliable, neither we nor the underwriters have independently verified the information and cannot guarantee its accuracy and completeness. The industry in which we operate is subject to a high degree of uncertainty and risk due to a variety of factors, including those described in the section entitled "Risk Factors." These and other factors could cause results to differ materially from those expressed in these publications.

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PROSPECTUS SUMMARY

This summary provides a brief overview of information contained elsewhere in this prospectus. Because it is abbreviated, this summary does not contain all of the information that you should consider before investing in our common stock. You should read the entire prospectus carefully before making an investment decision, including the information presented under the headings "Risk Factors," "Cautionary Note Regarding Forward-Looking Statements" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the historical consolidated financial statements and the related notes thereto appearing elsewhere in this prospectus. We have provided definitions for certain terms used in this prospectus in the "Glossary" appearing elsewhere in this prospectus. References to our estimated proved reserves and PV-10 are derived from our proved reserve reports prepared by Cawley, Gillespie & Associates, Inc.

In this prospectus, unless the context otherwise requires, the terms "we," "us," "our" and "Athlon" refer to Athlon Holdings LP and its subsidiaries before the completion of our corporate reorganization in April 2013 and Athlon Energy Inc. and its subsidiaries as of the completion of our corporate reorganization and thereafter. Please read "Corporate Reorganization." Unless otherwise indicated, the information contained in this prospectus assumes that the underwriters do not exercise their option to purchase additional shares from Apollo and that the New Holdings Units subject to the terms of the exchange agreement are not exchanged for shares of our common stock. The information throughout this prospectus assumes and gives effect to a 65.459 for 1 stock split that will be effected as of the effective date of the registration statement of which this prospectus forms a part.

Overview

        We are an independent exploration and production company focused on the acquisition, development and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. The Permian Basin spans portions of Texas and New Mexico and is composed of three primary sub-basins: the Delaware Basin, the Central Basin Platform and the Midland Basin. All of our properties are located in the Midland Basin. Our drilling activity is currently focused on the low-risk vertical development of stacked pay zones, including the Spraberry, Wolfcamp, Cline, Strawn, Atoka and Mississippian formations, which we refer to collectively as the Wolfberry play. We are a returns-focused organization and have targeted the Wolfberry play in the Midland Basin because of its favorable operating environment, consistent reservoir quality across multiple target horizons, long-lived reserve characteristics and high drilling success rates.

        We were founded in August 2010 by a group of former executives from Encore Acquisition Company following its acquisition by Denbury Resources, Inc. With an average of approximately 20 years of industry experience and over 10 years of history working together, our founding management has a proven track record of working as a team to acquire, develop and exploit oil and natural gas reserves in the Permian Basin as well as other resource plays in North America.

        Our acreage position was 124,925 gross (98,348 net) acres at May 31, 2013, which we group into three primary areas based on geographic location within the Midland Basin: Howard, Midland & Other and Glasscock. From the time we began operations in January 2011 through May 31, 2013, we have operated up to eight vertical drilling rigs simultaneously and have drilled 230 gross operated vertical Wolfberry wells with a 99% success rate across all three areas. This activity has allowed us to identify and de-risk our multi-year inventory of 4,902 gross (3,857 net) vertical drilling locations, while also identifying 1,079 gross (931 net) horizontal drilling locations in specific areas based on geophysical and technical data. As we continue to expand our vertical drilling activity to our undeveloped acreage, we expect to identify additional horizontal drilling locations.

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        The following table summarizes our leasehold position and identified net drilling locations by primary geographic area as of May 31, 2013:

					Identified Drilling Locations1
					Vertical
	Acreage
					Net 40-acre2		Net 20-acre		Net Total		Drilling Inventory3 (years)		Net Horizontal4
	Gross		Net
Howard		69,661		51,556		1,140		1,291		2,431		37		403
Midland & Other		36,694		33,709		390		414		804		20		316
Glasscock		18,570		13,083		267		355		622		24		212
Total		124,925		98,348		1,797		2,060		3,857		30		931

¹

Represents locations specifically identified by management based on evaluation of applicable geologic, engineering and production data. The drilling locations on which we actually drill wells will ultimately depend on the availability of capital, regulatory approvals, oil and natural gas prices, costs, actual drilling results and other factors.

²

Includes 597 gross (560 net) locations booked as proved undeveloped locations in our proved reserve report as of December 31, 2012.

³

Based on our 2013 drilling program on a gross basis.

⁴

Includes horizontal drilling locations targeting Wolfcamp A, Wolfcamp B, Wolfcamp C, Cline and Mississippian intervals, which comprise 311 gross (272 net), 357 gross (317 net), 133 gross (125 net), 227 gross (193 net) and 51 gross (24 net) locations, respectively.

        Since our inception, we have completed two significant acquisitions and seven bolt-on acquisitions. At the time of each acquisition, based on internal engineering estimates, these properties collectively contributed approximately 3,600 BOE/D of production and approximately 43 MMBOE of proved reserves. We have significantly grown production and proved reserves on the properties we acquired through the successful execution of our low-risk vertical drilling program. From the time we began operations in January 2011 through May 31, 2013, we have drilled 230 gross operated vertical Wolfberry wells on our properties with a 99% success rate and grown our production to 11,957 BOE/D for June 2013.

        In 2012, our development capital was approximately $276 million and we drilled a total of 133 gross (124 net) vertical Wolfberry wells. In 2013, we plan to invest $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells. We currently operate seven vertical drilling rigs on our properties and have operated between five and eight vertical drilling rigs since October 2011. We expect to take delivery of our first horizontal rig in the third quarter of 2013 and our second horizontal rig in the second quarter of 2014.

        Our estimate of proved reserves is prepared by Cawley, Gillespie & Associates, Inc. ("CG&A"), our independent petroleum engineers. As of December 31, 2012, we had 86 MMBOE of proved reserves, which were 58% oil, 22% NGLs and 20% natural gas and 30% proved developed. As of December 31, 2012, the PV-10 of our proved reserves was approximately $867 million, 59% of which was attributed to proved developed reserves. Our proved undeveloped reserves, or PUDs, are composed of 597 gross (560 net) potential vertical drilling locations. The following table provides

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information regarding our proved reserves and production by area as of December 31, 2012, except as otherwise noted below:

	Estimated Total Proved Reserves
														Average Net Daily Production3 (BOE/D)
	Oil (MMBbls)		NGLs (MMBbls)		Natural Gas (Bcf)		Total (MMBOE)		% Liquids1			PV-102 (in millions)				R/P Ratio (years)
Howard		20.2		7.3		36.3		33.5		82	%	$	365.4		4,392		20.9
Midland & Other		17.6		8.3		44.7		33.3		78	%		337.0		5,702		16.0
Glasscock		11.6		3.7		22.7		19.2		80	%		164.2		1,863		28.2
Total		49.4		19.3		103.7		86.0		80	%	$	866.6		11,957		19.7

¹

Includes both oil and NGLs.

²

PV-10 is a non-GAAP financial measure. Standardized Measure is the closest GAAP measure and our Standardized Measure was $850.9 million at December 31, 2012. For additional information about PV-10 and how it differs from the Standardized Measure, please read "Summary Consolidated Financial, Reserve and Operating Data—Non-GAAP Financial Measures."

³

During June 2013, inclusive of oil production of 6,895 Bbls/D in total.

Our Business Strategy

        We maintain a disciplined and analytical approach to investing in which we seek to direct capital in a manner that will maximize our rates of return as we develop our extensive resource base. Key elements of our strategy are:

•

Grow reserves, production and cash flow with our multi-year inventory of low-risk vertical drilling locations.  We have considerable experience managing large scale drilling programs and intend to efficiently develop our acreage position to maximize the value of our resource base. During 2012, we invested $276 million of development capital, drilled 133 gross (124 net) vertical Wolfberry wells and grew production by 4,204 BOE/D, or 93%, from 4,506 BOE/D in the fourth quarter of 2011 to 8,710 BOE/D in the fourth quarter of 2012. We also increased proved reserves by 40 MMBOE, or 86%, from 46 MMBOE at December 31, 2011 to 86 MMBOE at December 31, 2012. In 2013, we plan to invest approximately $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells in order to continue to grow our production and reserves.

•

Continuously improve capital and operating efficiency.  We continuously focus on optimizing the development of our resource base by seeking ways to maximize our recovery per well relative to the cost incurred and to minimize our operating cost per BOE produced. We apply an analytical approach to track and monitor the effectiveness of our drilling and completion techniques and service providers. Additionally, we seek to build infrastructure that allows us to achieve economies of scale and reduce operating costs. Specifically, we have:

•

achieved first six-month average daily production volumes on our operated wells in Howard County that outperformed average industry vertical well results by 102% since 2010, based on data from the Texas Railroad Commission;

•

achieved first six-month average daily production volumes on our operated wells in Midland County that outperformed average industry vertical well results by 68% since 2010, based on data from the Texas Railroad Commission;

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•

reduced average development costs per gross well in our Midland & Other area from $2.4 million in the first quarter of 2012 to $2.1 million in the first quarter of 2013, an improvement of 9%;

•

reduced average development costs per gross well in our Howard and Glasscock areas from $2.0 million in the first quarter of 2012 to $1.8 million in the first quarter of 2013, an improvement of 12%;

•

reduced the time from spud to rig release in our Howard and Glasscock areas from 16 days in the fourth quarter of 2011 to 8 days in the first quarter of 2013, an improvement of 50%; and

•

reduced LOE from $13.82 per BOE for 2011 to $9.89 per BOE for 2012, an improvement of 28%.

•

Balance capital allocation between our lower risk vertical drilling program and horizontal development opportunities.  We have historically focused on optimizing our vertical drilling and completion techniques across our acreage position. Vertical drilling involves less operational, financial and other risk than horizontal drilling, and we view our vertical development drilling program as "low risk" because the drilling locations were selected based on our extensive delineation drilling and production history in the area and well-established industry activity surrounding our acreage. Many operators in the Midland Basin are actively drilling horizontal wells, which is more expensive than drilling vertical Wolfberry wells but potentially recovers disproportionately more hydrocarbons per well. We monitor industry horizontal drilling activity and intend to utilize the knowledge gained from the increase in industry horizontal drilling in the Midland Basin. In the second half of 2013, we intend to supplement our vertical drilling with horizontal drilling in circumstances where we believe that horizontal drilling should offer competitive rates of return.

•

Evaluate and pursue oil-weighted acquisitions where we can add value through our technical expertise and knowledge of the basin.  We have significant experience acquiring and developing oil-weighted properties in the Permian Basin, and we expect to continue to selectively acquire additional properties in the Permian Basin that meet our rate-of-return objectives. Since our formation, we have completed two significant acquisitions and seven bolt-on acquisitions that have given us a unique and highly attractive acreage position, underpinned by strong baseline production and proved reserves. We believe our experience as a leading operator and our infrastructure footprint in the Permian Basin provide us with a competitive advantage in successfully executing and integrating acquisitions.

•

Maintain a disciplined, growth-oriented financial strategy.  We intend to fund our growth predominantly with internally generated cash flows while maintaining ample liquidity and access to capital markets. Substantially all of our lease terms allow us to allocate capital among projects in a manner that optimizes both costs and returns, resulting in a highly efficient drilling program. In addition, these terms allow us to adjust our capital spending depending on commodity prices and market conditions. We expect our cash flows from operating activities, availability under our credit agreement and the net proceeds of this offering to be sufficient to fund our capital expenditures and other obligations necessary to execute our business plan in 2013. Furthermore, we plan to hedge a significant portion of our expected production in order to stabilize our cash flows and maintain liquidity, allowing us to sustain a consistent drilling program, thereby preserving operational efficiencies that help us achieve our targeted rates of return.

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Our Competitive Strengths

        We have a number of competitive strengths that we believe will help us to successfully execute our business strategies, including:

•

High caliber management team with substantial technical and operational expertise.  Our founding management team has an average of approximately 20 years of industry experience and over 10 years of history working together with a proven track record of value creation at publicly traded oil and natural gas companies, including Encore Acquisition Company, XTO Energy Inc., Apache Corporation and Anadarko Petroleum Corporation. As of May 31, 2013, we had 23 engineering, land and geosciences technical personnel in our Fort Worth and Midland offices, with personnel experienced in both conventional and unconventional drilling operations. We believe our management and technical team is one of our principal competitive strengths due to our team's industry experience and history of working together in the identification, execution and integration of acquisitions, cost efficient management of profitable, large scale drilling programs and disciplined allocation of capital focused on rates of return.

•

High quality asset base with significant oil exposure in the Midland Basin.  Our acreage is concentrated in Howard, Midland and Glasscock counties, which are some of the most active counties in the Midland Basin. Since 2010, more vertical wells have been drilled in each of Howard and Glasscock counties than any other county in the Midland Basin, and Midland County has been the fifth most active county, based on data from the Texas Railroad Commission. Of the 9,242 vertical wells drilled in the Midland Basin since 2010, 1,579 (17%) have been drilled in Howard County, 1,255 (14%) have been drilled in Glasscock County and 714 (8%) have been drilled in Midland county. Furthermore, we have intentionally focused on crude oil and liquids opportunities to benefit from the relative disparity between oil and natural gas prices on an energy-equivalent basis, which has persisted over the last several years and which we expect to continue in the future. Approximately 58% and 22% of our proved reserves were oil and NGLs, respectively, as of December 31, 2012.

•

De-risked Midland Basin acreage position with multi-year vertical drilling inventory.  Since our management team commenced our development program in January 2011 through May 31, 2013, we have drilled 230 gross operated vertical Wolfberry wells across our leasehold position with a 99% success rate. Based on our extensive analysis of geophysical and technical data gained as a result of our vertical drilling program and from offset operator activity, as of May 31, 2013, we have identified 2,298 gross (1,797 net) vertical drilling locations on 40-acre spacing and an additional 2,604 gross (2,060 net) vertical drilling locations on 20-acre spacing across our leasehold, all of which target crude oil and NGLs as the primary objectives across stacked pay zones. Together, these 4,902 gross (3,857 net) identified drilling locations represent over 30 years of drilling inventory based on our expected 2013 drilling program. We view this drilling inventory as de-risked because the drilling locations were selected based on our extensive delineation drilling and production history in the area and well-established industry activity surrounding our acreage.

•

Extensive horizontal development potential.  Operators have drilled hundreds of horizontal wells in the Wolfcamp, Cline and Mississippian formations in the Midland Basin, including numerous horizontal wells offsetting our acreage, and are continuing to accelerate horizontal drilling activity. Multiple Wolfcamp formations are prevalent across our entire leasehold position, and the Cline and Mississippian formations are present across portions of our leasehold position. Based on vertical well control information from our operations and the operations of offset operators, we have initially identified 311 gross (272 net) horizontal drilling locations in the Wolfcamp A formation, 357 gross (317 net) horizontal drilling locations in the Wolfcamp B formation, 133 gross (125 net) horizontal drilling locations in the Wolfcamp C formation,

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227 gross (193 net) horizontal drilling locations in the Cline formation and 51 gross (24 net) horizontal drilling locations in the Mississippian formation. In addition, the subsurface data we have collected from our vertical drilling program also supports the potential for additional horizontal drilling in other formations, including the Strawn and Atoka formations. As we continue to expand our vertical drilling activity to our undeveloped acreage, we expect to identify additional horizontal drilling locations. Our vertical drilling has been designed to preserve these future horizontal drilling opportunities and optimize hydrocarbon recovery rates on our acreage. Beginning in the second half of 2013, we intend to supplement our vertical drilling with horizontal drilling in circumstances where we believe that horizontal drilling should offer competitive rates of return.

•

Large, concentrated acreage position with significant operational control.  Substantially all of our acreage is located in three counties in the Midland Basin. Our properties are characterized by large, contiguous acreage blocks, which has enabled us to implement more efficient and cost-effective operating practices and to capture economies of scale, including our installation of centralized production and fluid handling facilities, lowering of rig mobilization times and procurement of better vendor services. We seek to operate our properties so that we can continue to implement these efficient operating practices and control all aspects of our development program, including the selection of specific drilling locations, the timing of the development and the drilling and completion techniques used to efficiently develop our significant resource base. As of December 31, 2012, we operated approximately 99% of our proved reserves.

Recent Developments

Our Capital Restructuring Program

        In the first quarter of 2013, we commenced a plan to enhance our overall capital structure and liquidity, including the execution of our amended and restated credit agreement in March 2013 that extends the maturity date of our reserve based lending facility to 2018. On April 17, 2013, we issued $500 million of 7³/8% senior notes due 2021 and used most of the net proceeds from the offering to reduce the outstanding borrowings under our credit agreement and repay in full and terminate our former second lien term loan, thereby extending a large portion of our then-existing debt maturity to 2021. This offering represents a continuation of our plan, as we intend to apply the estimated proceeds of this offering to further reduce the outstanding borrowings under our credit agreement, provide additional liquidity for use in our drilling program and for general corporate purposes, including potential acquisitions.

Second Quarter 2013 Drilling and Production

        During the three months ended June 30, 2013, we continued to execute our drilling program, spudding 45 vertical Wolfberry wells, of which 20 are currently producing, 7 are currently being drilled and 18 are waiting to be completed. Our average daily production volumes during the second quarter of 2013 were 6.5 MBbls/D of oil, 12.8 MMcf/D of natural gas and 2.5 MBbls/D of NGLs, or 11.1 MBOE/D in total. This represents an increase of 12% above our average daily production volumes for the first quarter of 2013 and an increase of 68% above our average daily production volumes for the second quarter of 2012.

Hedge Portfolio

        Currently, we have oil swaps covering: 7,000 Bbls/D at a weighted-average price of $94.93 per Bbl for the remainder of 2013; 7,950 Bbls/D at a weighted-average price of $92.67 per Bbl for 2014; and

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1,300 Bbls/D at a weighted-average price of $93.18 per Bbl for 2015. We also have oil collars covering 150 Bbls/D for 2013 containing floors of $75.00 per Bbl and ceilings of $105.95 per Bbl.

2013 Capital Budget

        In 2013, we plan to invest $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells.

        In Howard, we plan to invest $155 million and drill 89 gross (82 net) wells. This includes 25 gross (23 net) PUD locations to be drilled through the Atoka/Mississippian formations at depths of approximately 9,900 feet. Our EURs per well for Howard PUD locations to be drilled through the Atoka/Mississippian formations average 141 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 64 gross (59 net) unproved locations through the Atoka/Mississippian formations.

        In Midland & Other, we plan to invest $95 million and drill 44 gross (42 net) wells. This includes 19 gross (19 net) PUD locations to be drilled through the Strawn/Atoka formations at depths of approximately 11,300 feet. Our EURs per well for Midland & Other PUD locations to be drilled through the Strawn/Atoka formations average 208 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 25 gross (23 net) unproved locations through the Strawn/Atoka formations.

        In Glasscock, we plan to invest $52 million and drill 29 gross (26 net) wells. This includes 8 gross (7 net) PUD locations to be drilled through the Atoka formation at depths of approximately 10,150 feet. Our EURs per well for Glasscock PUD locations to be drilled through the Atoka formation average 118 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 21 gross (19 net) unproved locations through the Atoka formation.

Risk Factors

        Investing in our common stock involves risks that include the speculative nature of oil and natural gas exploration, competition, volatile commodity prices and other material factors. For a discussion of these risks and other considerations that could negatively affect us, including risks related to this offering and our common stock, please read "Risk Factors" and "Cautionary Note Regarding Forward-Looking Statements."

Organizational Structure

        Athlon Energy Inc. is a holding company and its sole assets are controlling equity interests in Athlon Holdings LP and its subsidiaries. Athlon Energy Inc. operates and controls all of the business and affairs and consolidates the financial results of Athlon Holdings LP and its subsidiaries. Prior to our reorganization in April 2013, Apollo Investment Fund VII, L.P. and its parallel funds (the "Apollo Funds"), members of our management team and certain employees owned all of the Class A limited partner interests in Athlon Holdings LP and members of our management team and certain employees owned all of the Class B limited partner interests in Athlon Holdings LP. In the reorganization, the Apollo Funds entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Athlon Holdings LP for common stock of Athlon Energy Inc. The remaining holders of Class A limited partner interests in Athlon Holdings LP have not exchanged their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Athlon Holdings LP exchanged their interests for common stock of Athlon Energy Inc. Upon closing of this offering, the limited partnership agreement of Athlon Holdings LP will be amended and restated to, among other things, modify Athlon Holdings

7

LP's capital structure by replacing its different classes of interests with a single new class of units that we refer to as the "New Holdings Units." The members of our management team and certain employees that hold Class A limited partner interests of Athlon Holdings LP will own New Holdings Units and will enter into an exchange agreement under which (subject to the terms of the exchange agreement) they will have the right, under certain circumstances, to exchange their New Holdings Units for shares of common stock of Athlon Energy Inc. on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. All other New Holdings Units will be held by Athlon Energy Inc. Please read "Corporate Reorganization" and "Certain Relationships and Related Party Transactions—Exchange Agreement."

        The diagram below sets forth our simplified organizational structure after our corporate reorganization and this offering. This chart is provided for illustrative purposes only and does not represent all legal entities affiliated with us. The ownership percentages after this offering are based on an estimated valuation of Athlon using an assumed initial public offering price of $19.00 per share, the midpoint of the price range set forth on the cover page of this propsectus.

¹

The Apollo Funds and the public stockholders will hold 65.8% and 22.1% of our shares of common stock, respectively, if the underwriters exercise in full their option to purchase additional shares of common stock from the Apollo Funds.

²

Borrowing base of $320 million as of July 22, 2013.

³

Co-Issuer of our 7³/8% senior notes due 2021.

⁴

Guarantors of our credit agreement and 7³/8% senior notes due 2021.

8

Principal Stockholders

        Our principal stockholders are the Apollo Funds. The Apollo Funds are affiliates of Apollo Global Management, LLC (together with its subsidiaries, "Apollo").

        Apollo, founded in 1990, is a leading global alternative investment manager with offices in New York, Los Angeles, Houston, London, Frankfurt, Luxembourg, Singapore, Mumbai and Hong Kong. As of March 31, 2013, Apollo had assets under management of over $114 billion in private equity, credit-oriented capital markets and real estate funds invested across a core group of nine industries where Apollo has considerable knowledge and resources. Apollo's team of more than 250 seasoned investment professionals possesses a broad range of transactional, financial, managerial and investment skills, which has enabled the firm to deliver strong long-term investment performance throughout expansionary and recessionary economic cycles.

        Upon completion of this initial public offering and based on an estimated valuation of Athlon using an assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus), the Apollo Funds will beneficially own approximately 68.6% of our common stock (or approximately 65.8% if the underwriters' option to purchase additional shares of common stock from the Apollo Funds is exercised in full). We are also a party to certain other agreements with the Apollo Funds and certain of their affiliates. For a description of these agreements, please read "Certain Relationships and Related Party Transactions."

Corporate Information

        Our principal executive offices are located at 420 Throckmorton Street, Suite 1200, Fort Worth, Texas 76102, and our telephone number is (817) 984-8200. Our website is www.athlonenergy.com. We expect to make our periodic reports and other information filed with or furnished to the SEC available free of charge through our website as soon as reasonably practicable after those reports and other information are electronically filed with or furnished to the SEC. Information on our website or any other website is not incorporated by reference herein and does not constitute a part of this prospectus.

Emerging Growth Company Status

        We are an "emerging growth company" as defined in the Jumpstart Our Business Startups Act (the "JOBS Act"). For as long as we are an emerging growth company, unlike other public companies, we will not be required to:

•

provide an auditor's attestation report on management's assessment of the effectiveness of our system of internal control over financial reporting pursuant to Section 404 of the Sarbanes-Oxley Act of 2002 (the "Sarbanes-Oxley Act");

•

comply with any new requirements adopted by the Public Company Accounting Oversight Board, requiring mandatory audit firm rotation or a supplement to the auditor's report in which the auditor would be required to provide additional information about the audit and the financial statements of the issuer;

•

provide certain disclosure regarding executive compensation required of larger public companies; or

•

hold stockholder advisory votes on executive compensation.

        We will cease to be an emerging growth company upon the earliest of:

•

when we have $1.0 billion or more in annual revenues;

•

when we have at least $700 million in market value of our common equity securities held by non-affiliates as of any June 30;

•

when we issue more than $1.0 billion of non-convertible debt over a rolling three-year period; or

•

the last day of the fiscal year following the fifth anniversary of our initial public offering.

        As an emerging growth company, we can delay the adoption of certain accounting standards until those standards would otherwise apply to private companies. However, we have chosen to "opt out" of such extended transition period, and as a result, we will comply with new or revised accounting standards on the relevant dates on which adoption of such standards is required for non-emerging growth companies. This decision is irrevocable.

9

THE OFFERING

Common stock offered by Athlon Energy Inc.	15,789,474 shares.
Common stock to be outstanding after the offering	82,122,646 shares.
New Holdings Units to be outstanding after the offering	83,984,689 units (1,862,043 of which will be exchangeable for 1,862,043 shares of our common stock).
Over-allotment option	The underwriters have a 30-day option to purchase 2,368,421 shares of common stock from the Apollo Funds if the underwriters sell more than 15,789,474 shares in this offering.
Use of proceeds	We expect to receive approximately $278.5 million of net proceeds from the sale of the common stock offered by us, based upon the assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus), after deducting estimated underwriting discounts and commissions and estimated offering expenses. Each $1.00 decrease in the public offering price would decrease our net proceeds by approximately $14.9 million. We intend to use the net proceeds from this offering to purchase newly issued New Holdings Units from Athlon Holdings LP, which would subsequently use the net proceeds to repay outstanding indebtedness under our credit agreement, provide additional liquidity for use in our drilling program and for general corporate purposes, including potential acquisitions. We will not receive any proceeds from sales by the Apollo Funds, including pursuant to the underwriters' option to purchase additional shares of common stock.
	Affiliates of certain of the underwriters are lenders under our credit agreement and, accordingly, will receive a portion of the net proceeds from this offering. Please read "Use of Proceeds" and "Underwriting (Conflicts of Interest)."
Dividend policy	We do not anticipate paying any cash dividends on our common stock. In addition, our credit agreement and the indenture governing our senior notes place certain restrictions on our ability to pay cash dividends. Please read "Dividend Policy."
Risk factors	You should carefully read and consider the information beginning on page 18 of this prospectus set forth under the heading "Risk Factors" and all other information set forth in this prospectus before deciding to invest in our common stock.
Listing and trading symbol	We have been approved to list our common stock on the New York Stock Exchange ("NYSE") under the symbol "ATHL."

10

Conflicts of interest Apollo Global Securities, LLC is an affiliate of Apollo, our controlling stockholder. Since Apollo beneficially owns more than 10% of our outstanding common stock, a "conflict of interest" is deemed to exist under Rule 5121(f)(5)(B) of the Conduct Rules of the Financial Industry Regulatory Authority, or FINRA. In addition, if the Apollo Funds sell shares of common stock in this offering, the Apollo Funds, as selling stockholders, will likely receive more than 5% of the net proceeds of this offering, a "conflict of interest" also exists under Rule 5121(f)(5)(C)(ii). Accordingly, this offering will be made in compliance with the applicable provisions of Rule 5121. Since Apollo is not primarily responsible for managing this offering, the appointment of a "qualified independent underwriter" is not required pursuant to Rule 5121(a)(1). As such, any underwriter that has a conflict of interest pursuant to Rule 5121 will not confirm sales to accounts in which it exercises discretionary authority without the prior written consent of the customer. Please read "Underwriting (Conflicts of Interest)."

        The information above excludes 8,400,000 shares of common stock initially reserved for issuance under the Athlon Energy Inc. 2013 Incentive Award Plan (which amount may be increased each year in accordance with the terms of the plan).

        If the New Holdings Units subject to the terms of the exchange agreement were exchanged in full upon completion of this offering for shares of our common stock, there would be a total of 83,984,689 shares of our common stock outstanding, 18.8% of which would be owned by purchasers in this offering (assuming the option to purchase additional shares of common stock from the Apollo Funds is not exercised).

        If this offering is priced above the assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus) or if more than the number of shares set forth on the cover page of this prospectus are sold, then we may sell only such number of shares (the "threshold number") as is necessary to achieve gross proceeds from this offering to us of $300 million, and the Apollo Funds may sell a number of shares equal to the difference between the threshold number and the number of shares sold in this offering.

11

SUMMARY CONSOLIDATED FINANCIAL, RESERVE AND OPERATING DATA

        The following summary consolidated financial, reserve and operating data of Athlon Holdings LP, our accounting predecessor, should be read in conjunction with, and are qualified by reference to, "Selected Historical Consolidated Financial Data," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the consolidated financial statements and notes thereto included elsewhere in this prospectus.

        We derived the summary historical consolidated balance sheets data, statements of operations data and statements of cash flow data as of and for the years ended December 31, 2011 and 2012 of Athlon Holdings LP from the audited consolidated financial statements of Athlon Holdings LP, which are included elsewhere in this prospectus. We derived the summary historical consolidated balance sheet data as of March 31, 2013 and the historical consolidated statements of operations data and statements of cash flow data for the three months ended March 31, 2013 and 2012 of Athlon Holdings LP from the unaudited consolidated financial statements of Athlon Holdings LP, which are included elsewhere in this prospectus.

        The summary unaudited pro forma consolidated statements of operations data for the three months ended March 31, 2013 and for the year ended December 31, 2012 has been prepared to give pro forma effect to (i) our senior notes offering in April 2013, (ii) the reorganization transactions described under "Corporate Reorganization" and (iii) this offering and the application of the net proceeds from this offering as if they had been completed as of January 1, 2012. The summary unaudited pro forma consolidated balance sheet data as of March 31, 2013 has been prepared to give pro forma effect to these transactions as if they had been completed as of March 31, 2013. These data are subject and give effect to the assumptions and adjustments described in the notes accompanying the unaudited pro forma financial statements included elsewhere in this prospectus. The summary unaudited pro forma consolidated financial data are presented for informational purposes only and should not be considered indicative of actual results of operations that would have been achieved had the senior notes offering, the reorganization transactions and this offering been consummated on the dates indicated, and do not purport to be indicative of statements of financial position or results of operations as of any future date or for any future period.

12

Summary Consolidated Financial Data

						Historical Athlon Holdings LP
	Pro Forma Athlon Energy Inc.
						Three months ended March 31,						Year ended December 31,
	Three months ended March 31, 2013
			Year ended December 31, 2012
						2013			2012			2012			2011
	(unaudited)					(unaudited)
	(in thousands, except per share data)
Consolidated Statements of Operations Data:
Revenues:
Oil	$	45,659	$	128,081		$	45,659		$	27,433		$	128,081		$	51,193
Natural gas		3,367		8,415			3,367			1,448			8,415			3,521
NGLs		5,720		20,615			5,720			4,351			20,615			10,967
Total revenues		54,746		157,111			54,746			33,232			157,111			65,681
Expenses:
Production:
Lease operating		7,237		25,503			7,237			4,699			25,503			13,328
Production, severance and ad valorem taxes		3,694		10,438			3,694			2,350			10,438			4,727
Depletion, depreciation and amortization		18,053		54,456			18,053			9,614			54,456			19,747
General and administrative		3,282		9,678			3,282			2,597			9,678			7,724
Acquisition costs		57		876			57			—			876			9,519
Derivative fair value loss (gain)		6,849		(9,293	)		6,849			22,711			(9,293	)		7,959
Other operating		194		562			194			130			562			404
Total expenses		39,366		92,220			39,366			42,101			92,220			63,408
Operating income (loss)		15,380		64,891			15,380			(8,869	)		64,891			2,273
Interest expense		9,976		40,590			4,474			1,495			9,949			2,932
Income (loss) before income taxes		5,404		24,301			10,906			(10,364	)		54,942			(659	)
Income tax provision (benefit)		2,021		9,086			27			(364	)		1,928			470
Consolidated net income (loss)		3,383		15,215			10,879			(10,000	)		53,014			(1,129	)
Less: net income (loss) attributable to noncontrolling interest		118		529			—			—			—			—
Net income (loss) attributable to stockholders	$	3,265	$	14,686		$	10,879		$	(10,000	)	$	53,014		$	(1,129	)
Net income (loss) per common share:
Basic	$	0.05	$	0.22
Diluted	$	0.05	$	0.22
Weighted average common shares outstanding:
Basic		66,333		66,333
Diluted		68,195		68,195
Consolidated Statements of Cash Flows Data:
Cash provided by (used in):
Operating activities						$	30,397		$	20,723		$	95,302		$	18,872
Investing activities							(90,560	)		(58,498	)		(347,259	)		(465,475	)
Financing activities							54,671			12,982			228,798			471,627
Consolidated Balance Sheets Data (at period end):
Cash and cash equivalents	$	275,103				$	3,379					$	8,871		$	32,030
Total assets		1,197,926					916,535						852,298			561,823
Total debt		500,000					416,426						362,000			170,000
Total equity		612,848					433,330						420,877			327,452
Other Financial Data:
Adjusted EBITDA1	$	40,669	$	111,160		$	40,669		$	21,171		$	111,160		$	39,094
Development capital							71,791			49,241			276,182			89,232

¹

Adjusted EBITDA is a non-GAAP financial measure. For a definition of Adjusted EBITDA and a reconciliation to our most directly comparable financial measures calculated and presented in accordance with GAAP, please read "—Non-GAAP Financial Measures."

13

Summary Reserve Data

        The following table presents summary data with respect to our estimated net proved reserves as of the dates indicated. The reserve estimates presented in the table below are based on proved reserve reports prepared by CG&A, our independent petroleum engineers, in accordance with the rules and regulations of the SEC regarding oil and natural gas reserve reporting. For more information about our proved reserves as of December 31, 2012 and 2011, please read CG&A's proved reserve reports, which have been filed as exhibits to the registration statement of which this prospectus is a part.

	December 31,
	2012			2011
Reserves Data1:
Estimated proved reserves:
Oil (MBbls)		49,423			25,972
Natural gas (MMcf)		103,683			51,560
NGLs (MBbls)		19,275			11,549
Total estimated proved reserves (MBOE)		85,979			46,114
Proved developed reserves (MBOE)		25,698			13,496
% proved developed		30	%		29	%
Proved undeveloped reserves (MBOE)		60,281			32,618
PV-10 of proved reserves (in millions)2	$	866.6		$	591.4
Standardized Measure (in millions)3	$	850.9		$	581.2

¹

Our estimated proved reserves and related future net revenues, PV-10 and Standardized Measure were determined using index prices for oil and natural gas, without giving effect to commodity derivative contracts, and were held constant throughout the life of the properties. The unweighted arithmetic average first-day-of-the-month prices for the prior 12 months were $94.71 per Bbl for oil and $2.75 per Mcf for natural gas at December 31, 2012 and $96.19 per Bbl for oil and $4.11 per Mcf for natural gas at December 31, 2011. These prices were adjusted by lease for quality, transportation fees, historical geographic differentials, marketing bonuses or deductions and other factors affecting the price received at the wellhead.

²

PV-10 is a non-GAAP financial measure and generally differs significantly from Standardized Measure, the most directly comparable GAAP financial measure, because it does not include the effects of federal income taxes on future net revenues. As of December 31, 2012 and 2011, our accounting predecessor was a limited partnership not subject to federal income taxes. Accordingly, no provision for federal income taxes has been provided for in our Standardized Measure because taxable income was passed through to its partners. However, the PV-10 and the Standardized Measure differ as a result of the Texas margin tax. Had we been a Subchapter C Corporation subject to federal income taxation, our Standardized Measure would have been $602.5 million and $428.5 million as of December 31, 2012 and 2011, respectively, on a pro forma basis. Neither PV-10 nor Standardized Measure represents an estimate of the fair market value of our proved reserves. We and others in the industry use PV-10 as a measure to compare the relative size and value of proved reserves held by companies without regard to the specific tax characteristics of such entities. Please read "—Non-GAAP Financial Measures."

³

Standardized Measure represents the present value of estimated future cash inflows from proved reserves, less future development, production and income tax expenses, discounted at 10% per annum to reflect timing of future cash flows.

Non-GAAP Financial Measures

Adjusted EBITDA

        We include in this prospectus the non-GAAP financial measure Adjusted EBITDA. We provide a reconciliation of Adjusted EBITDA to its most directly comparable financial measures as calculated and presented in accordance with GAAP.

        We define Adjusted EBITDA as consolidated net income (loss):

Plus:

•

Interest expense;

•

Income tax provision;

•

Depreciation, depletion and amortization;

•

Acquisition costs;

•

Advisory fees;

14

•

Non-cash equity-based compensation expense;

•

Derivative fair value loss;

•

Net derivative settlements received adjusted for recovered premiums;

•

Accretion of discount on asset retirement obligations;

•

Impairment of oil and natural gas properties, if any; and

•

Other non-cash operating items.

Less:

•

Interest income;

•

Income tax benefit;

•

Derivative fair value gain; and

•

Net derivative settlements paid adjusted for recovered premiums.

        Adjusted EBITDA is used as a supplemental financial measure by management and by external users of our consolidated financial statements, such as investors, lenders under our credit agreement, commercial banks, research analysts and others, to assess:

•

the financial performance of our assets without regard to financing methods, capital structure or historical cost basis;

•

our operating performance and return on capital as compared to those of other companies in the upstream energy sector, without regard to financing or capital structure; and

•

the attractiveness of capital projects and acquisitions and the overall rates of return on alternative investment opportunities.

        The GAAP measures most directly comparable to Adjusted EBITDA are cash flows provided by operating activities and consolidated net income (loss). Adjusted EBITDA should not be considered as an alternative to cash flows provided by operating activities or consolidated net income (loss). Adjusted EBITDA may not be comparable to similar measures used by other companies. You should not consider Adjusted EBITDA in isolation or as a substitute for analysis of our results as reported under GAAP. Adjusted EBITDA has limitations as an analytical tool and should not be considered as an alternative to, or more meaningful than, performance measures calculated in accordance with GAAP. Some of these limitations are:

•

certain items excluded from Adjusted EBITDA are significant components in understanding and assessing a company's financial performance, such as a company's cost of capital and tax structure, as well as the historical costs of depreciable assets;

•

Adjusted EBITDA does not reflect our cash expenditures or future requirements for capital expenditures or contractual commitments;

•

Adjusted EBITDA does not reflect changes in, or cash requirements for, our working capital needs;

•

although depreciation, depletion and amortization are non-cash charges, the assets being depreciated, depleted and amortized will often have to be replaced in the future, and Adjusted EBITDA does not reflect any cash requirements for such replacements; and

•

our computation of Adjusted EBITDA may not be comparable to other similarly titled measures of other companies.

        Management compensates for the limitations of Adjusted EBITDA as an analytical tool by reviewing the comparable GAAP measures, understanding the differences between the measures and incorporating these data points into their decision-making process.

15

        The following table presents a reconciliation of Adjusted EBITDA to the GAAP financial measure of consolidated net income (loss):

							Historical Athlon Holdings LP
	Pro Forma Athlon Energy Inc.
							Three months ended March 31,						Year ended December 31,
	Three months ended March 31, 2013
				Year ended December 31, 2012
							2013			2012			2012			2011
	(in thousands)
Consolidated net income (loss)	$	3,383		$	15,215		$	10,879		$	(10,000	)	$	53,014		$	(1,129	)
Interest expense		9,976			40,590			4,474			1,495			9,949			2,932
Income tax provision (benefit)		2,021			9,086			27			(364	)		1,928			470
Depreciation, depletion and amortization		18,053			54,456			18,053			9,614			54,456			19,747
Acquisition costs		57			876			57			—			876			9,519
Advisory fees1		405			493			405			213			493			411
Non-cash equity-based compensation		48			152			48			58			152			106
Derivative fair value loss (gain)2		6,849			(9,293	)		6,849			22,711			(9,293	)		7,959
Net derivative settlements paid adjusted for recovered premiums3		(318	)		(1,074	)		(318	)		(2,698	)		(1,074	)		(2,734	)
Accretion4		149			478			149			106			478			344
Other non-cash operating items5		46			181			46			36			181			1,469
Adjusted EBITDA	$	40,669		$	111,160		$	40,669		$	21,171		$	111,160		$	39,094

¹

Represents the annual advisory fee paid to affiliates of Apollo pursuant to a Services Agreement. The Services Agreement will be terminated in connection with this offering. Please read "Certain Relationships and Related Party Transactions."

²

Represents total derivative loss (gain) reported in our consolidated statements of operations.

³

The purpose of this adjustment is to reflect derivative gains and losses on a cash basis in the period the derivative settled rather than the period the gain or loss was recognized for GAAP. It represents the net cash payments on derivative contracts for all commodity derivatives that were settled during the respective periods, excluding any portion representing a recovery of cost (i.e., premiums paid).

⁴

Represents the non-cash accretion of discount on asset retirement obligations.

⁵

Represents deferred rent expense and non-cash LOE.

        The following table presents a reconciliation of Adjusted EBITDA to the GAAP financial measure of cash flows provided by operating activities:

	Historical Athlon Holdings LP
	Three months ended March 31,						Year ended December 31,
	2013			2012			2012			2011
	(in thousands)
Adjusted EBITDA	$	40,669		$	21,171		$	111,160		$	39,094
Changes in operating assets and liabilities		(5,579	)		1,102			(5,639	)		(6,510	)
Acquisition costs		(57	)		—			(876	)		(9,519	)
Non-cash LOE		—			—			—			(1,159	)
Cash interest expense		(4,231	)		(1,337	)		(8,850	)		(2,623	)
Advisory fees1		(405	)		(213	)		(493	)		(411	)
Cash flows provided by operating activities	$	30,397		$	20,723		$	95,302		$	18,872

¹

Represents the annual advisory fee paid to affiliates of Apollo pursuant to a Services Agreement. The Services Agreement will be terminated in connection with this offering. Please read "Certain Relationships and Related Party Transactions."

16

PV-10

        PV-10 is a non-GAAP financial measure and is derived from Standardized Measure, which is the most directly comparable GAAP financial measure. PV-10 is equal to the Standardized Measure of discounted future net cash flows at the applicable date, before deducting future income taxes, discounted at 10%. We believe that the presentation of PV-10 is relevant and useful to investors because it presents the relative monetary significance of our properties regardless of tax structure. Further, investors may utilize the measure as a basis for comparison of the relative size and value of our proved reserves to other companies. We use this measure when assessing the potential return on investment related to our oil, natural gas and NGL properties. However, PV-10 is not equal to, nor a substitute for, the Standardized Measure of discounted future net cash flows. Our PV-10 and the Standardized Measure of discounted future net cash flows do not purport to present the fair value of our proved reserves. The following table provides a reconciliation of PV-10 to the GAAP financial measure of Standardized Measure as of December 31, 2012 and 2011:

	As of December 31,
	2012			2011
	(in millions)
PV-10 of proved reserves	$	866.6		$	591.4
Present value of future income tax discounted at 10%		(15.7	)		(10.2	)
Standardized Measure	$	850.9		$	581.2

Summary Operating Data

        The following table sets forth summary data with respect to our production results, average realized prices and certain expenses on a per BOE basis for the periods presented:

	Three months ended March 31,				Year ended December 31,
	2013		2012		2012		2011
Total production volumes:
Oil (MBbls)		542		276		1,457		556
Natural gas (MMcf)		1,030		534		3,163		1,017
NGLs (MBbls)		183		102		595		239
Combined (MBOE)		896		468		2,579		964
Average daily production volumes:
Oil (Bbls/D)		6,023		3,036		3,981		1,523
Natural gas (Mcf/D)		11,446		5,871		8,641		2,786
NGLs (Bbls/D)		2,028		1,125		1,625		654
Combined (BOE/D)		9,959		5,140		7,047		2,641
Average realized prices:
Oil ($/Bbl) (excluding impact of cash settled derivatives)	$	84.23	$	99.29	$	87.90	$	92.08
Oil ($/Bbl) (after impact of cash settled derivatives)		60.73		65.28		60.50		65.29
Natural gas ($/Mcf)		3.27		2.71		2.66		3.46
NGLs ($/Bbl)		31.34		42.48		34.65		45.96
Combined ($/BOE) (excluding impact of cash settled derivatives)		61.08		71.05		60.91		68.13
Combined ($/BOE) (after impact of cash settled derivatives)		83.65		89.53		87.16		87.16
Expenses (per BOE):
Lease operating	$	8.07	$	10.05	$	9.89	$	13.82
Production, severance and ad valorem taxes		4.12		5.03		4.05		4.90
Depletion, depreciation and amortization		20.14		20.55		21.11		20.48
General and administrative		3.73		5.55		3.75		8.01

17

RISK FACTORS

An investment in our common stock involves a high degree of risk. You should carefully consider the following risks and all of the other information contained in this prospectus before deciding to invest in our common stock. Our business, financial condition and results of operations could be materially and adversely affected by any of these risks. The risks described below are not the only ones facing us. Additional risks not presently known to us or which we consider immaterial also may adversely affect us.

Risks Related to the Oil and Natural Gas Industry and Our Business

Our business is difficult to evaluate because we have a limited operating history.

        Athlon Holdings LP was formed in July 2011 and became the sole owner of Athlon Energy LP, which began operating our first properties after acquiring them in January 2011. As a result, there is only limited historical financial and operating information available upon which to base your evaluation of our performance.

Drilling for and producing oil and natural gas are high-risk activities with many uncertainties that may result in a total loss of investment or otherwise adversely affect our business, financial condition or results of operations.

        Our drilling activities are subject to many risks. For example, we cannot assure you that wells drilled by us will be productive or that we will recover all or any portion of our investment in such wells. Drilling for oil and natural gas often involves unprofitable efforts, not only from dry holes but also from wells that are productive but do not produce sufficient oil or natural gas to return a profit at then-realized prices after deducting drilling, operating and other costs. The seismic data and other technologies we use do not allow us to know conclusively prior to drilling a well that oil or natural gas is present or that it can be produced economically. The costs of exploration, exploitation and development activities are subject to numerous uncertainties beyond our control, and increases in those costs can adversely affect the economics of a project. In addition, the application of new techniques for us such as horizontal drilling, which we have not previously employed, may make it more difficult to accurately estimate these costs. Further, our drilling and producing operations may be curtailed, delayed, canceled or otherwise negatively impacted as a result of other factors, including:

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unusual or unexpected geological formations;

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loss of drilling fluid circulation;

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title problems;

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facility or equipment malfunctions;

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unexpected operational events;

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shortages or delivery delays or increases in the cost of equipment and services;

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reductions in oil and natural gas prices;

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lack of proximity to and shortage of capacity of transportation facilities;

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the limited availability of financing at acceptable rates;

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delays imposed by or resulting from compliance with environmental and other governmental or regulatory requirements, which may include limitations on hydraulic fracturing or the discharge of greenhouse gases; and

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adverse weather conditions.

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        Any of these risks can cause substantial losses, including personal injury or loss of life, damage to or destruction of property, natural resources and equipment, pollution, environmental contamination or loss of wells and other regulatory penalties.

Our development and exploratory drilling efforts and our well operations may not be profitable or achieve our targeted returns.

        We have acquired significant amounts of unproved property in order to further our development efforts and expect to continue to undertake acquisitions in the future. Development and exploratory drilling and production activities are subject to many risks, including the risk that no commercially productive reservoirs will be discovered. We acquire unproved properties and lease undeveloped acreage that we believe will enhance our growth potential and increase our results of operations over time. However, we cannot assure you that all prospects will be economically viable or that we will not abandon our investments. Additionally, we cannot assure you that unproved property acquired by us or undeveloped acreage leased by us will be profitably developed, that wells drilled by us in prospects that we pursue will be productive or that we will recover all or any portion of our investment in such unproved property or wells.

We may have difficulty managing growth in our business, which could adversely affect our financial condition and results of operations.

        As a recently formed company, growth in accordance with our business plan, if achieved, could place a significant strain on our financial, technical, operational and management resources. As we expand our activities and increase the number of projects we are evaluating or in which we participate, there will be additional demands on our financial, technical, operational and management resources. The failure to continue to upgrade our technical, administrative, operating and financial control systems or the occurrences of unexpected expansion difficulties, including the failure to recruit and retain experienced managers, geologists, engineers and other professionals in the oil and natural gas industry, could have a material adverse effect on our business, financial condition and results of operations and our ability to timely execute our business plan.

As of May 31, 2013, approximately 45% of our net leasehold acreage is undeveloped, and that acreage may not ultimately be developed or become commercially productive, which could cause us to lose rights under our leases as well as have a material adverse effect on our reserves and future production and, therefore, our future cash flow and income.

        As of May 31, 2013, approximately 45% of our net leasehold acreage is undeveloped, or acreage on which wells have not been drilled or completed to a point that would permit the production of commercial quantities of hydrocarbons regardless of whether such acreage contains proved reserves. In addition, many of our oil and natural gas leases require us to drill wells that are commercially productive, and if we are unsuccessful in drilling such wells, we could lose our rights under such leases. Our reserves and future production and, therefore, our future cash flow and income are highly dependent on successfully developing our undeveloped leasehold acreage.

Our development and exploration operations require substantial capital and we may be unable to obtain needed capital or financing on satisfactory terms or at all, which could lead to a loss of properties and a decline in our reserves.

        The oil and natural gas industry is capital intensive. We make and expect to continue to make substantial capital expenditures in our business and operations for the exploration for and development, production and acquisition of reserves. In 2012, our total development capital was approximately $276 million and expenditures for leasehold interest and property acquisitions were approximately $81 million. Our 2013 development capital budget for drilling, completion and infrastructure, including investments in water disposal infrastructure and gathering line projects, is approximately $350 million.

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To date, we have financed capital expenditures primarily with funding from the Apollo Funds, our equity sponsor, borrowings under our credit agreement and cash flows from operations. Notwithstanding prior contributions to us by the Apollo Funds or their affiliates, you should not assume that any of them will provide any debt or equity funding to us in the future.

        In the near term, we intend to finance our capital expenditures with cash flows from operations and borrowings under our credit agreement. Our cash flows from operations and access to capital are subject to a number of variables, including:

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our proved reserves;

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the volume of hydrocarbons we are able to produce from existing wells;

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the prices at which our production is sold;

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the levels of our operating expenses; and

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our ability to acquire, locate and produce new reserves.

        We cannot assure you that our operations and other capital resources will provide cash in sufficient amounts to maintain planned or future levels of capital expenditures. Further, our actual capital expenditures in 2013 could exceed our budget. In the event our capital expenditure requirements at any time are greater than the amount of capital we have available, we could be required to seek additional sources of capital, which may include traditional reserve base borrowings, debt financing, joint ventures, production payment financings, sales of assets, private or public offerings of debt or equity securities or other means. Our ability to access the private and public debt or equity markets is dependent upon a number of factors outside our control, including oil and natural gas prices as well as economic conditions in the financial markets. We cannot assure you that we will be able to obtain debt or equity financing on terms favorable to us, or at all.

        Our business and operating results can be harmed by factors such as the availability, terms and cost of capital, increases in interest rates or a reduction in our credit rating. Changes in any one or more of these factors could cause our cost of doing business to increase, limit our access to capital, limit our ability to pursue acquisition opportunities, reduce our cash flows available for drilling and place us at a competitive disadvantage. In addition, our ability to access the private and public debt or equity markets is dependent upon a number of factors outside our control, including oil and natural gas prices as well as economic conditions in the financial markets. Continuing disruptions and volatility in the global financial markets may lead to an increase in interest rates or a contraction in credit availability impacting our ability to finance our operations. We cannot assure you that we will be able to obtain debt or equity financing on terms favorable to us, or at all.

        If we are unable to fund our capital requirements, we may be required to curtail our operations relating to the exploration and development of our prospects, which in turn could lead to a possible loss of properties and a decline in our reserves, or may be otherwise unable to implement our development plan, complete acquisitions or otherwise take advantage of business opportunities or respond to competitive pressures, any of which could have a material adverse effect on our production, revenues and results of operations. In addition, a delay in or the failure to complete proposed or future infrastructure projects could delay or eliminate potential efficiencies and related cost savings.

Our success depends on finding, developing or acquiring additional reserves. Unless we replace our oil and natural gas reserves, our reserves and production will decline, which would adversely affect our business, financial condition and results of operations.

        Our future oil and natural gas reserves and production, and therefore our cash flows and income, highly depend on our ability to find, develop or acquire additional reserves that are economically recoverable. Our proved reserves will generally decline as reserves are depleted, except to the extent that we conduct successful exploration or development activities or acquire properties containing

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proved reserves, or both. To increase reserves and production, we undertake development, exploration and other replacement activities or use third parties to accomplish these activities. We have made, and expect to make in the future, substantial capital expenditures in our business and operations for the development, production, exploration and acquisition of reserves. We may not have sufficient resources to undertake our exploration, development and production activities. In addition, the acquisition of reserves, our exploratory projects and other replacement activities may not result in significant additional reserves and we may not have success drilling productive wells at low finding and development costs. Furthermore, although our revenues may increase if prevailing commodity prices increase, our finding costs for additional reserves could also increase.

Our project areas, which are in various stages of development, may not yield oil or natural gas in commercially viable quantities.

        Our project areas are in various stages of development, ranging from project areas with current drilling or production activity to project areas that consist of recently acquired leasehold acreage or that have limited drilling or production history. From the time we began operations in January 2011 through May 31, 2013, we have drilled a total of 230 gross (220 net) wells and participated in an additional 8 gross (3 net) non-operated wells. In total, 216 gross (202 net) of these wells were completed as producing wells and 3 gross (3 net) wells were abandoned as dry holes. At May 31, 2013, 19 gross (19 net) wells were in various stages of completion. If the wells in the process of being completed do not produce sufficient revenues to return a profit or if we drill dry holes in the future, our business may be materially affected.

Our identified potential drilling locations, which are scheduled out over many years, are susceptible to uncertainties that could materially alter the occurrence or timing of their drilling.

        As of May 31, 2013, we had identified 2,298 gross (1,797 net) potential vertical drilling locations on our existing acreage based on 40-acre spacing and an additional 2,604 gross (2,060 net) potential vertical drilling locations based on 20-acre spacing. Only 597 gross (560 net) of these potential vertical drilling locations were attributed to PUDs in our December 31, 2012 reserve report. These drilling locations, including those without PUDs, represent a significant part of our growth strategy. Our ability to drill and develop these locations depends on a number of uncertainties, including the availability of capital, construction of infrastructure, inclement weather, regulatory changes and approvals, commodity prices, lease expirations, our ability to secure rights to drill at deeper formations, costs and drilling results.

        Further, our identified potential drilling locations are in various stages of evaluation, ranging from locations that are ready to drill to locations that will require substantial additional analysis of data. We cannot predict in advance of drilling and testing whether any particular drilling location will yield oil or natural gas reserves in sufficient quantities to recover drilling or completion costs or to be economically viable or whether wells drilled on 20-acre spacing will produce at the same rates as those on 40-acre spacing. The use of reliable technologies and the study of producing fields in the same area will not enable us to know conclusively prior to drilling whether oil or natural gas reserves will be present or, if present, whether oil or natural gas reserves will be present in sufficient quantities to be economically viable. Even if sufficient amounts of oil or natural gas reserves exist, we may damage the potentially productive hydrocarbon bearing formation or experience mechanical difficulties while drilling or completing the well, possibly resulting in a reduction in production from the well or abandonment of the well. If we drill dry holes in our current and future drilling locations, our drilling success rate may decline and materially harm our business. We cannot assure you that the analogies we draw from available data from other wells, more fully explored locations or producing fields will be applicable to our drilling locations. Further, initial production rates reported by us or other operators in the Permian Basin may not be indicative of future or long-term production rates.

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        Because of these uncertainties, we do not know if the potential drilling locations we have identified will ever be drilled or if we will be able to produce oil or natural gas reserves from these or any other potential drilling locations. As such, our actual drilling activities may materially differ from those presently identified, which could adversely affect our business, financial condition and results of operations.

The development of our PUDs may take longer and may require higher levels of capital expenditures than we anticipate and may not be economically viable.

        Approximately 70% of our total proved reserves at December 31, 2012 were PUDs and may not be ultimately developed or produced. Recovery of PUDs requires significant capital expenditures and successful drilling operations. The reserve data included in the independent petroleum engineering firm's proved reserve report assumes that substantial capital expenditures are required to develop such reserves. We cannot be certain that the estimated costs of the development of these reserves are accurate, that development will occur as scheduled or that the results of such development will be as estimated. Delays in the development of our reserves or increases in costs to drill and develop such reserves will reduce future net revenues of our estimated PUDs and may result in some projects becoming uneconomic. In addition, delays in the development of reserves could cause us to have to reclassify our proved reserves as PUDs.

Our acreage must be drilled before lease expiration, generally within three to five years, in order to hold the acreage by production. In a highly competitive market for acreage, failure to drill sufficient wells to hold acreage may result in a substantial lease renewal cost, or if renewal is not feasible, loss of our lease and prospective drilling opportunities.

        Leases on oil and natural gas properties typically have a term of three to five years, after which they expire unless, prior to expiration, production is established within the spacing units covering the undeveloped acres. As of May 31, 2013, we had leases representing 9,639 gross (7,653 net) acres scheduled to expire in 2013, 5,362 gross (4,257 net) acres scheduled to expire in 2014, 9,213 gross (7,363 net) acres scheduled to expire in 2015, 27,224 gross (21,049 net) acres scheduled to expire in 2016 and no net acres scheduled to expire in 2017. The cost to renew such leases may increase significantly, and we may not be able to renew such leases on commercially reasonable terms or at all. Moreover, many of our leases require lessor consent to pool, which may make it more difficult to hold our leases by production. Any reduction in our current drilling program, either through a reduction in capital expenditures or the unavailability of drilling rigs, could result in the loss of acreage through lease expirations. In addition, in order to hold our current leases scheduled to expire in 2014 and 2015, we will need to operate at least a three-rig program. We cannot assure you that we will have the liquidity to deploy these rigs when needed, or that commodity prices will warrant operating such a drilling program. Any such losses of leases could materially and adversely affect the growth of our asset base, cash flows and results of operations.

The unavailability, high cost or shortages of rigs, equipment, raw materials, supplies or personnel may restrict our operations.

        The oil and natural gas industry is cyclical, which can result in shortages of drilling rigs, equipment, raw materials (particularly sand and other proppants), supplies and personnel. When shortages occur, the costs and delivery times of rigs, equipment and supplies increase and demand for, and wage rates of, qualified drilling rig crews also rise with increases in demand for oil and natural gas. In accordance with customary industry practice, we rely on independent third-party service providers to provide most of the services necessary to drill new wells. If we are unable to secure a sufficient number of drilling rigs at reasonable costs, our financial condition and results of operations could suffer, and we may not be able to drill all of our acreage before our leases expire. In addition, we do not have long-term contracts securing the use of our existing rigs, and the operator of those rigs may choose to cease providing services to us. We are currently operating seven vertical drilling rigs across our

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properties and we expect to take delivery of our first horizontal rig in the third quarter of 2013 and our second horizontal rig in the second quarter of 2014. In 2014, we intend to expand to an eight-rig vertical drilling program. Shortages of drilling rigs, equipment, raw materials (particularly sand and other proppants), supplies, drilling rig crews and other personnel, trucking services, tubulars, fracking and completion services and production equipment, including equipment and personnel related to horizontal drilling activities, could delay or restrict our exploration and development operations, which in turn could impair our financial condition and results of operations.

The volatility of oil and natural gas prices due to factors beyond our control greatly affects our profitability.

        Our revenues, operating results, profitability, future rate of growth and the carrying value of our oil and natural gas properties depend primarily upon the prevailing commodity prices. Historically, oil and natural gas prices have been volatile and are subject to fluctuations in response to changes in supply and demand, market uncertainty and a variety of additional factors that are beyond our control, including:

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the regional, domestic and foreign supply of oil and natural gas;

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the level of commodity prices and expectations about future commodity prices;

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the level of global oil and natural gas exploration and production;

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localized supply and demand fundamentals, including the proximity and capacity of oil and natural gas pipelines and other transportation facilities, and other factors that result in differentials to benchmark prices from time to time;

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the cost of exploring for, developing, producing and transporting reserves;

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the price of foreign imports;

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political and economic conditions in oil producing countries;

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the ability of members of the Organization of Petroleum Exporting Countries to agree to and maintain oil price and production controls;

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speculative trading in crude oil and natural gas derivative contracts;

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the level of consumer product demand;

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weather conditions and other natural disasters;

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risks associated with operating drilling rigs;

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technological advances affecting exploration and production operations and overall energy consumption;

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domestic and foreign governmental regulations and taxes;

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the continued threat of terrorism and the impact of military and other action, including U.S. military operations in the Middle East;

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the price and availability of competitors' supplies of oil and natural gas and alternative fuels; and

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overall domestic and global economic conditions.

        These factors and the volatility of the energy markets make it extremely difficult to predict future oil and natural gas price movements with any certainty. For example, during the past five years, the NYMEX prompt month contract price for WTI has ranged from a low of $33.87 per Bbl in December 2008 to a high of $145.29 per Bbl in July 2008, and the Henry Hub prompt month contract price of natural gas has ranged from a low of $1.91 per MMBtu in April 2012 to a high of $13.58 per MMBtu

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in July 2008. During the first quarter of 2013, WTI prompt month contract ranged from $90.12 to $97.94 per Bbl and the Henry Hub prompt month contract price of natural gas ranged from $3.11 to $4.07 per MMBtu. During 2012, WTI prompt month contract ranged from $77.69 to $109.77 per Bbl and the Henry Hub prompt month contract price of natural gas ranged from $1.91 to $3.90 per MMBtu. On March 31, 2013, the WTI prompt month contract price for crude oil was $97.23 per Bbl and the Henry Hub prompt month contract price of natural gas was $4.02 per MMBtu. Any substantial decline in commodity prices will likely have a material adverse effect on our operations, financial condition and level of expenditures for the development of our reserves.

        As of December 31, 2012, NGLs comprised 22% of our estimated proved reserves and accounted for 23% of our 2012 production at an average price of $34.65 per Bbl, a 25% drop in average price from the prior year. Further, realized NGL prices have decreased principally due to significant supply. The terms of our sale contracts allow purchasers of our production to decline to purchase our produced ethane and instead pay dry natural gas prices for the ethane that we produce in the gas stream. NGLs are made up of ethane, propane, isobutane, normal butane and natural gasoline, all of which have different uses and different pricing characteristics. A further or extended decline in NGL prices could materially and adversely affect our future business, financial condition and results of operations.

        Substantially all of our production is sold to purchasers under contracts with market-based prices. Moreover, all of our oil contracts include the Midland-Cushing differential (the difference between Midland WTI and Cushing WTI), which widened in 2012 and in early 2013 due to difficulty transporting oil production from the Permian Basin to the Gulf Coast refineries as a result of lack of logistics and infrastructure. The Midland-Cushing differential has since narrowed. We may experience differentials to NYMEX in the future, which may be material. Lower oil, natural gas and NGL prices will reduce our cash flows and the present value of our reserves. If oil, natural gas and NGL prices deteriorate, we anticipate that the borrowing base under our credit agreement, which is revised periodically, may be reduced, which would negatively impact our borrowing ability. Additionally, prices could reduce our cash flows to a level that would require us to borrow to fund our current or future capital budgets. Lower oil, natural gas and NGL prices may also reduce the amount of oil, natural gas and NGLs that we can produce economically. Substantial decreases in oil, natural gas and NGL prices could render uneconomic a significant portion of our identified drilling locations. This may result in significant downward adjustments to our estimated proved reserves. If this occurs or if our production estimates change or our exploration or development results deteriorate, full cost accounting rules may require us to write down, as a non-cash charge to earnings, the carrying value of our oil and natural gas properties. As a result, a substantial or extended decline in oil, natural gas or NGL prices may materially and adversely affect our future business, financial condition, results of operations, liquidity or ability to finance planned capital expenditures.

We have entered into oil derivative contracts and may in the future enter into additional commodity derivative contracts for a portion of our production, which may result in future cash payments or prevent us from receiving the full benefit of increases in commodity prices.

        We use commodity derivative contracts to reduce price volatility associated with certain of our oil sales. Under these contracts, we receive a fixed price per Bbl of oil and pay a floating market price per Bbl of oil to the counterparty based on NYMEX WTI pricing. The fixed-price payment and the floating-price payment are offset, resulting in a net amount due to or from the counterparty. The extent of our commodity price exposure is related largely to the effectiveness and scope of our commodity derivative contracts. For example, some of the commodity derivative contracts we utilize are based on quoted market prices, which may differ significantly from the actual prices we realize in our operations for oil. In addition, our credit agreement limits the aggregate notional volume of commodities that can be covered under commodity derivative contracts we can enter into and, as a result, we will continue to have direct commodity price exposure on the unhedged portion of our production volumes. As of March 31, 2013, we have oil swaps covering: 6,000 Bbls/D at a weighted-

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average price of $94.66 per Bbl for 2013; 5,950 Bbls/D at a weighted-average price of $92.76 per Bbl for 2014; and 1,300 Bbls/D at a weighted-average price of $93.18 per Bbl for 2015. We also have oil collars covering 150 Bbls/D for 2013 containing floors of $75.00 per Bbl and ceilings of $105.95 per Bbl. Our policy has been to hedge a significant portion of our estimated oil production. However, our price hedging strategy and future hedging transactions will be determined at our discretion. We are not under an obligation to hedge a specific portion of our production. The prices at which we hedge our production in the future will be dependent upon commodity prices at the time we enter into these transactions, which may be substantially higher or lower than current commodity prices. Accordingly, our price hedging strategy may not protect us from significant declines in commodity prices received for our future production, whether due to declines in prices in general or to widening differentials we experience with respect to our products. Conversely, our hedging strategy may limit our ability to realize cash flows from commodity price increases. It is also possible that a substantially larger percentage of our future production will not be hedged as compared with the next few years, which would result in our revenues becoming more sensitive to commodity price changes.

        In addition, our actual future production may be significantly higher or lower than we estimate at the time we enter into commodity derivative contracts for such period. If the actual amount is higher than we estimate, we will have greater commodity price exposure than we intended. If the actual amount is lower than the notional amount of our commodity derivative contracts, we might be forced to satisfy all or a portion of our commodity derivative contracts without the benefit of the cash flow from our sale or purchase of the underlying physical commodity, substantially diminishing our liquidity. There may be a change in the expected differential between the underlying commodity price in the commodity derivative contract and the actual price received, which may result in payments to our derivative counterparty that are not offset by our receipt of payments for our production in the field. Accordingly, our earnings may fluctuate significantly as a result of changes in the fair value of our commodity derivative contracts.

Our commodity derivative contracts expose us to counterparty credit risk.

        Our commodity derivative contracts expose us to risk of financial loss if a counterparty fails to perform under a contract. Disruptions in the financial markets could lead to sudden decreases in a counterparty's liquidity, which could make them unable to perform under the terms of the contract and we may not be able to realize the benefit of the contract. We are unable to predict sudden changes in a counterparty's creditworthiness or ability to perform. Even if we do accurately predict sudden changes, our ability to negate the risk may be limited depending upon market conditions.

        During periods of declining commodity prices, our derivative contract receivable positions generally increase, which increases our counterparty credit exposure. If the creditworthiness of our counterparties deteriorates and results in their nonperformance, we could incur a significant loss with respect to our commodity derivative contracts.

The inability of one or more of our customers to meet their obligations may adversely affect our financial results.

        In addition to credit risk related to receivables from commodity derivative contracts, our principal exposure to credit risk is through receivables from purchasers of our oil and natural gas production. For 2012, three purchasers accounted for more than 10% of our revenues: Pecos Gathering & Marketing (43%); Occidental Petroleum Corporation (29%); and DCP Midstream (12%). This concentration of customers may impact our overall credit risk in that these entities may be similarly affected by changes in economic and other conditions. Current economic circumstances may further increase these risks. We do not require our customers to post collateral. The inability or failure of our significant customers to meet their obligations to us or their insolvency or liquidation may materially adversely affect our financial condition and results of operations.

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Our method of accounting for investments in oil and natural gas properties may result in impairment of asset value.

        We account for our oil and natural gas producing activities using the full cost method of accounting. Accordingly, all costs incurred in the acquisition, exploration and development of proved oil and natural gas properties, including the costs of abandoned properties, dry holes, geophysical costs and annual lease rentals are capitalized. We also capitalize direct operating costs for services performed with internally owned drilling and well servicing equipment. All general and administrative corporate costs unrelated to drilling activities are expensed as incurred. Sales or other dispositions of oil and natural gas properties are accounted for as adjustments to capitalized costs, with no gain or loss recorded unless the ratio of cost to proved reserves would significantly change. Depletion of evaluated oil and natural gas properties is computed on the units of production method based on proved reserves. The average depletion rate per BOE of production was $21.03 and $20.32 for 2012 and 2011, respectively. Total depletion expense for oil and natural gas properties was $54.2 million and $19.6 million for 2012 and 2011, respectively.

        The net capitalized costs of proved oil and natural gas properties are subject to a full cost ceiling limitation in which the costs are not allowed to exceed their related estimated future net revenues discounted at 10%. To the extent capitalized costs of evaluated oil and natural gas properties, net of accumulated depreciation, depletion, amortization and impairment exceed the discounted future net revenues of proved reserves, the excess capitalized costs are charged to expense.

        To date, we have not recorded any impairment on proved oil and natural gas properties. However, we may experience ceiling test write downs in the future. Please read "Management's Discussion and Analysis of Financial Condition and Results of Operations—Critical Accounting Policies and Estimates—Impairment" for a more detailed description of our method of accounting.

Our estimated reserves are based on many assumptions that may turn out to be inaccurate. Any significant inaccuracies in these reserve estimates or underlying assumptions will materially affect the quantities and present value of our proved reserves.

        Oil and natural gas reserve engineering is not an exact science and requires subjective estimates of underground accumulations of reserves and assumptions concerning future commodity prices, production levels, EURs and operating and development costs. As a result, estimated quantities of proved reserves, projections of future production rates and the timing of development expenditures may be incorrect. Our estimates of proved reserves and related valuations as of December 31, 2012 and 2011 are based on proved reserve reports prepared by CG&A, our independent petroleum engineers. CG&A conducted a well-by-well review of all our properties for the periods covered by its proved reserve reports using information provided by us. Over time, we may make material changes to proved reserve estimates taking into account the results of actual drilling, testing and production. Also, certain assumptions regarding future commodity prices, production levels and operating and development costs may prove incorrect. Any significant variance from these assumptions to actual figures could greatly affect our estimates of proved reserves, the economically recoverable quantities of reserves attributable to any particular group of properties, the classifications of reserves based on risk of recovery and estimates of the future net cash flows. A substantial portion of our reserve estimates are made without the benefit of a lengthy production history, which are less reliable than estimates based on a lengthy production history. Numerous changes over time to the assumptions on which our reserve estimates are based, as described above, often result in the actual quantities of reserves we ultimately recover being different from our estimates.

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        The estimates of proved reserves as of December 31, 2012 and 2011 included in this prospectus were prepared using an average price equal to the unweighted arithmetic average of hydrocarbon prices received on a field-by-field basis on the first day of each month within the 12 months ended December 31, 2012 and 2011, respectively, in accordance with GAAP. Reserve estimates do not include any value for probable or possible reserves that may exist, nor do they include any value for unproved acreage. The reserve estimates represent our net revenue interest in our properties.

        The timing of both our production and our incurrence of costs in connection with the development and production of reserves will affect the timing of actual future net cash flows from proved reserves.

SEC rules could limit our ability to book additional PUDs in the future.

        SEC rules require that, subject to limited exceptions, PUDs may only be booked if they relate to wells scheduled to be drilled within five years after the date of booking. This requirement has limited and may continue to limit our ability to book additional PUDs as we pursue our drilling program. Moreover, we may be required to write down our PUDs if we do not drill those wells within the required five-year timeframe.

The Standardized Measure of discounted future net cash flows from our proved reserves will not be the same as the current market value of our estimated oil and natural gas reserves.

        You should not assume that the Standardized Measure of discounted future net cash flows from our proved reserves is the current market value of our estimated oil and natural gas reserves. In accordance with SEC requirements in effect at December 31, 2012 and 2011, we based the discounted future net cash flows from our proved reserves on the 12-month first-day-of-the-month oil and natural gas average prices without giving effect to derivative transactions. Actual future net cash flows from our oil and natural gas properties will be affected by factors such as:

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actual prices we receive for oil and natural gas;

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actual cost of development and production expenditures;

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the amount and timing of actual production; and

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changes in governmental regulations or taxation.

        The timing of both our production and our incurrence of expenses in connection with the development and production of oil and natural gas properties will affect the timing and amount of actual future net revenues from proved reserves, and thus their actual present value. In addition, the 10% discount factor we use when calculating Standardized Measure may not be the most appropriate discount factor based on interest rates in effect from time to time and risks associated with us or the oil and natural gas industry in general. As a limited partnership, our predecessor was not subject to federal taxation. Accordingly, our Standardized Measure does not provide for federal corporate income taxes because taxable income was passed through to its partners. As a corporation, we will be treated as a taxable entity for federal income tax purposes and our future income taxes will be dependent on our future taxable income. Actual future prices and costs may differ materially from those used in the present value estimates included in this prospectus which could have a material effect on the value of our reserves.

All of our properties are located in the Permian Basin, making us vulnerable to risks associated with operating in one geographic area.

        All of our producing properties are located in the Permian Basin. As a result of this concentration, we may be disproportionately exposed to the impact of regional supply and demand factors, delays or interruptions of production from wells in this area caused by governmental regulation, processing or transportation capacity constraints, availability of equipment, facilities, personnel or services market

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limitations or interruption of the processing or transportation of crude oil, natural gas or NGLs. In addition, the effect of fluctuations on supply and demand may become more pronounced within specific geographic oil and natural gas producing areas such as the Permian Basin, which may cause these conditions to occur with greater frequency or magnify the effects of these conditions. Due to the concentrated nature of our portfolio of oil and natural gas properties, a number of our properties could experience any of the same conditions at the same time, resulting in a relatively greater impact on our results of operations than they might have on other companies that have a more diversified portfolio of properties. Such delays or interruptions could have a material adverse effect on our financial condition and results of operations.

We depend upon a limited number of significant purchasers for the sale of most of our production. The loss of one or more of these purchasers could, among other factors, limit our access to suitable markets for the hydrocarbons we produce.

        The availability of a ready market for any hydrocarbons we produce depends on numerous factors beyond the control of our management, including but not limited to the extent of domestic production and imports of oil, the proximity and capacity of natural gas pipelines, the availability of skilled labor, materials and equipment, the effect of state and federal regulation of oil and natural gas production and federal regulation of natural gas sold in interstate commerce. In addition, we depend upon a limited number of significant purchasers for the sale of most of our production, and our contracts with those customers typically are on a month-to-month basis. The loss of these customers could adversely affect our revenues and have a material adverse effect on our financial condition and results of operations. We cannot assure you that any of our customers will continue to do business with us or that we will continue to have ready access to suitable markets for our future production.

Our operations are substantially dependent on the availability of water. Restrictions on our ability to obtain water may have an adverse effect on our financial condition, results of operations and cash flows.

        Water is an essential component of deep shale oil and natural gas production during both the drilling and hydraulic fracturing processes. Historically, we have been able to purchase water from local land owners for use in our operations. According to the Lower Colorado River Authority, during 2011, Texas experienced the lowest inflows of water of any year in recorded history. As a result of this severe drought, some local water districts have begun restricting the use of water subject to their jurisdiction for hydraulic fracturing to protect local water supply. If we are unable to obtain water to use in our operations from local sources, we may be unable to economically produce our reserves, which could have an adverse effect on our financial condition, results of operations and cash flows.

We may face unanticipated water and other waste disposal costs.

        We may be subject to regulation that restricts our ability to discharge water produced as part of our natural gas production operations. Productive zones frequently contain water that must be removed in order for the natural gas to produce, and our ability to remove and dispose of sufficient quantities of water from the various zones will determine whether we can produce natural gas in commercial quantities. The produced water must be transported from the lease and injected into disposal wells. The availability of disposal wells with sufficient capacity to receive all of the water produced from our wells may affect our ability to produce our wells. Also, the cost to transport and dispose of that water, including the cost of complying with regulations concerning water disposal, may reduce our profitability.

        Where water produced from our projects fails to meet the quality requirements of applicable regulatory agencies, our wells produce water in excess of the applicable volumetric permit limits, the disposal wells fail to meet the requirements of all applicable regulatory agencies, or we are unable to secure access to disposal wells with sufficient capacity to accept all of the produced water, we may have

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to shut in wells, reduce drilling activities, or upgrade facilities for water handling or treatment. The costs to dispose of this produced water may increase if any of the following occur:

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we cannot obtain future permits from applicable regulatory agencies;

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water of lesser quality or requiring additional treatment is produced;

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our wells produce excess water;

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new laws and regulations require water to be disposed in a different manner; or

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costs to transport the produced water to the disposal wells increase.

Declining general economic, business or industry conditions may have a material adverse effect on our results of operations, liquidity and financial condition.

        Concerns over global economic conditions, energy costs, geopolitical issues, inflation, the availability and cost of credit, the European debt crisis and the United States financial market have contributed to increased economic uncertainty and diminished expectations for the global economy. In addition, continued hostilities in the Middle East and the occurrence or threat of terrorist attacks in the United States or other countries could adversely affect the global economy. These factors, combined with volatile commodity prices, declining business and consumer confidence and increased unemployment, have precipitated an economic slowdown and a recession. Concerns about global economic growth have had a significant adverse impact on global financial markets and commodity prices. If the economic climate in the United States or abroad deteriorates, worldwide demand for petroleum products could diminish, which could impact the price at which we can sell our production, affect the ability of our vendors, suppliers and customers to continue operations and ultimately adversely impact our results of operations, liquidity and financial condition.

We have incurred losses from operations during certain periods since our inception and may do so in the future.

        We incurred a net loss of $1.1 million for 2011, our first full year of operation, and we may incur net losses in the future. Our development of and participation in an increasingly larger number of drilling locations has required and will continue to require substantial capital expenditures. The uncertainty and risks described in this prospectus may impede our ability to economically find, develop and acquire reserves. As a result, we may not be able to sustain profitability or positive cash flows provided by operating activities in the future.

Part of our strategy involves drilling in existing or emerging shale plays using the latest available horizontal drilling and completion techniques, which involve risks and uncertainties in their application.

        Our operations involve utilizing the latest drilling and completion techniques as developed by us and our service providers. While horizontal drilling is a significant part of our growth strategy, we have not previously drilled a horizontal well and therefore are subject to increased risks associated with horizontal drilling as compared to companies that have experience in horizontal drilling activities.

        Risks that we face while drilling include, but are not limited to, failing to land our wellbore in the desired drilling zone, not staying in the desired drilling zone while drilling horizontally through the formation, not running our casing the entire length of the wellbore and not being able to run tools and other equipment consistently through the horizontal wellbore. Risks that we face while completing our wells include, but are not limited to, not being able to fracture stimulate the planned number of stages, not being able to run tools the entire length of the wellbore during completion operations and not successfully cleaning out the wellbore after completion of the final fracture stimulation stage. We expect to face many of these similar risks when we commence our horizontal drilling program. In

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addition, to the extent we engage in horizontal drilling, those activities may adversely affect our ability to successfully drill in one or more of our identified vertical drilling locations.

        Ultimately, the success of these drilling and completion techniques can only be evaluated over time as more wells are drilled and production profiles are established over a sufficiently long time period. If our drilling results are less than anticipated or we are unable to execute our drilling program because of capital constraints, lease expirations, access to gathering systems and/or commodity prices decline, the return on our investment in these areas may not be as attractive as we anticipate. Further, as a result of any of these developments we could incur material write-downs of our oil and natural gas properties and the value of our undeveloped acreage could decline in the future.

Our level of indebtedness may increase and reduce our financial flexibility.

        As of March 31, 2013, on a pro forma basis giving effect to our April 2013 senior notes offering and the application of the net proceeds therefrom, we would have had a total of $503.4 million in outstanding indebtedness and $264.1 million of borrowing capacity under our credit agreement. We may incur significant indebtedness in the future in order to make acquisitions or to develop our properties.

        Our level of indebtedness could affect our operations in several ways, including the following:

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a significant portion of our cash flows could be used to service our indebtedness;

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a high level of debt would increase our vulnerability to general adverse economic and industry conditions;

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the covenants contained in the agreements governing our outstanding indebtedness limit our ability to borrow additional funds, dispose of assets, pay dividends and make certain investments;

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a high level of debt may place us at a competitive disadvantage compared to our competitors that are less leveraged and therefore, may be able to take advantage of opportunities that our indebtedness would prevent us from pursuing;

•

our debt covenants may also affect our flexibility in planning for, and reacting to, changes in the economy and in our industry;

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a high level of debt may make it more likely that a reduction in our borrowing base following a periodic redetermination could require us to repay a portion of our then-outstanding bank borrowings; and

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a high level of debt may impair our ability to obtain additional financing in the future for working capital, capital expenditures, acquisitions, general corporate or other purposes.

        A high level of indebtedness increases the risk that we may default on our debt obligations. Our ability to meet our debt obligations and to reduce our level of indebtedness depends on our future performance. General economic conditions, commodity prices and financial, business and other factors affect our operations and our future performance. Many of these factors are beyond our control. We may not be able to generate sufficient cash flows to pay the interest on our debt and future working capital, borrowings or equity financing may not be available to pay or refinance such debt. Factors that will affect our ability to raise cash through an offering of our capital stock or a refinancing of our debt include financial market conditions, the value of our assets and our performance at the time we need capital.

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The agreements governing our indebtedness contain restrictive covenants that may limit our ability to respond to changes in market conditions or pursue business opportunities.

        Our credit agreement and the indenture governing our senior notes contain restrictive covenants that limit our ability to, among other things:

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incur additional indebtedness;

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create additional liens;

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sell assets;

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merge or consolidate with another entity;

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pay dividends or make other distributions;

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engage in transactions with affiliates; and

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enter into certain commodity derivative contracts.

        In addition, our credit agreement requires us to maintain certain financial ratios and tests. The requirement that we comply with these provisions may materially adversely affect our ability to react to changes in market conditions, take advantage of business opportunities we believe to be desirable, obtain future financing, fund needed capital expenditures or withstand a continuing or future downturn in our business.

If we are unable to comply with the restrictions and covenants in the agreements governing our indebtedness, there could be an event of default under the terms of such agreements, which could result in an acceleration of repayment.

        If we are unable to comply with the restrictions and covenants in our credit agreement or the indenture governing our senior notes, there could be an event of default. Our ability to comply with these restrictions and covenants, including meeting the financial ratios and tests under our credit agreement, may be affected by events beyond our control. As a result, we cannot assure that we will be able to comply with these restrictions and covenants or meet such financial ratios and tests. In the event of a default under our credit agreement or the indenture governing our senior notes, the lenders could terminate their commitments to lend or accelerate the loans and declare all amounts borrowed due and payable. If any of these events occur, our assets might not be sufficient to repay in full all of our outstanding indebtedness and we may be unable to find alternative financing. Even if we could obtain alternative financing, it might not be on terms that are favorable or acceptable to us. Additionally, we may not be able to amend our credit agreement or obtain needed waivers on satisfactory terms.

Our borrowings under our credit agreement expose us to interest rate risk.

        Our results of operations are exposed to interest rate risk associated with borrowings under our credit agreement, which bear interest at a rate elected by us that is based on the prime, LIBOR or federal funds rate plus margins ranging from 0.50% to 2.50% depending on the type of loan used and the amount of the loan outstanding in relation to the borrowing base. As of March 31, 2013, the weighted-average interest rate on outstanding borrowings under our credit agreement was approximately 2.5%. If interest rates increase, so will our interest costs, which may have a material adverse effect on our results of operations and financial condition.

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Any significant reduction in our borrowing base under our credit agreement as a result of the periodic borrowing base redeterminations or otherwise may negatively impact our ability to fund our operations.

        Under our credit agreement, which currently provides for a $320 million borrowing base, we are subject to collateral borrowing base redeterminations based on our proved reserves. Any significant reduction in our borrowing base as a result of such borrowing base redeterminations or otherwise may negatively impact our liquidity and our ability to fund our operations and, as a result, may have a material adverse effect on our financial condition, results of operations and cash flows.

We rely on a few key employees whose absence or loss could adversely affect our business.

        Many key responsibilities within our business have been assigned to a small number of employees. The loss of their services could adversely affect our business. In particular, the loss of the services of one or more members of our management team, including our Chief Executive Officer, Robert C. Reeves, could disrupt our operations. We have employment agreements with these executives which contain restrictions on competition with us in the event they cease to be employed by us. However, as a practical matter, such employment agreements may not assure the retention of our employees. Further, we do not maintain "key person" life insurance policies on any of our employees. As a result, we are not insured against any losses resulting from the death of our key employees.

Operating hazards and uninsured risks may result in substantial losses and could prevent us from realizing profits.

        Our operations are subject to all of the hazards and operating risks associated with drilling for and production of oil and natural gas, including the risk of fire, explosions, blowouts, surface cratering, uncontrollable flows of natural gas, oil and formation water, pipe or pipeline failures, abnormally pressured formations, casing collapses and environmental hazards such as oil spills, natural gas leaks, ruptures or discharges of toxic gases. In addition, our operations are subject to risks associated with hydraulic fracturing, including any mishandling, surface spillage or potential underground migration of fracturing fluids, including chemical additives. The occurrence of any of these events could result in substantial losses to us due to injury or loss of life, severe damage to or destruction of property, natural resources and equipment, pollution or other environmental damage, clean-up responsibilities, regulatory investigation and penalties, suspension of operations and repairs to resume operations.

        We endeavor to contractually allocate potential liabilities and risks between us and the parties that provide us with services and goods, which include pressure pumping and hydraulic fracturing, drilling and cementing services and tubular goods for surface, intermediate and production casing. Under our agreements with our vendors, to the extent responsibility for environmental liability is allocated between the parties, (1) our vendors generally assume all responsibility for control and removal of pollution or contamination which originates above the surface of the land and is directly associated with such vendors' equipment while in their control and (2) we generally assume the responsibility for control and removal of all other pollution or contamination which may occur during our operations, including pre-existing pollution and pollution which may result from fire, blowout, cratering, seepage or any other uncontrolled flow of oil, natural gas or other substances, as well as the use or disposition of all drilling fluids. In addition, we generally agree to indemnify our vendors for loss or destruction of vendor-owned property that occurs in the well hole or as a result of the use of equipment, certain corrosive fluids, additives, chemicals or proppants. However, despite this general allocation of risk, we might not succeed in enforcing such contractual allocation, might incur an unforeseen liability falling outside the scope of such allocation or may be required to enter into contractual arrangements with terms that vary from the above allocations of risk. As a result, we may incur substantial losses which could materially and adversely affect our financial condition and results of operations.

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        In accordance with what we believe to be customary industry practice, we maintain insurance against some, but not all, of our business risks. Our insurance may not be adequate to cover any losses or liabilities we may suffer. Also, insurance may no longer be available to us or, if it is, its availability may be at premium levels that do not justify its purchase. The occurrence of a significant uninsured claim, a claim in excess of the insurance coverage limits maintained by us or a claim at a time when we are not able to obtain liability insurance could have a material adverse effect on our ability to conduct normal business operations and on our financial condition, results of operations or cash flows. In addition, we may not be able to secure additional insurance or bonding that might be required by new governmental regulations. This may cause us to restrict our operations, which might severely impact our financial condition. We may also be liable for environmental damage caused by previous owners of properties purchased by us, which liabilities may not be covered by insurance.

        Since hydraulic fracturing activities are part of our operations, they are covered by our insurance against claims made for bodily injury, property damage and clean-up costs stemming from a sudden and accidental pollution event. However, we may not have coverage if we are unaware of the pollution event and unable to report the "occurrence" to our insurance company within the time frame required under our insurance policy. We have no coverage for gradual, long-term pollution events. In addition, these policies do not provide coverage for all liabilities, and we cannot assure you that the insurance coverage will be adequate to cover claims that may arise, or that we will be able to maintain adequate insurance at rates we consider reasonable. A loss not fully covered by insurance could have a material adverse effect on our financial condition, results of operations and cash flows. Please read "Business—Operational Hazards and Insurance" for a description of our insurance coverage.

Our failure to successfully identify, complete and integrate future acquisitions of properties or businesses could reduce our operating results and slow our growth.

        There is intense competition for acquisition opportunities in our industry and we may not be able to identify attractive acquisition opportunities. Even if we do identify attractive acquisition opportunities, we may not be able to complete the acquisition or do so on commercially acceptable terms. Competition for acquisitions may increase the cost of, or cause us to refrain from, completing acquisitions. Our ability to complete acquisitions is dependent upon, among other things, our ability to obtain debt and equity financing and, in some cases, regulatory approvals. Further, these acquisitions may be in geographic regions in which we do not currently operate, which could result in unforeseen operating difficulties and difficulties in coordinating geographically dispersed operations, personnel and facilities. In addition, if we enter into new geographic markets, we may be subject to additional and unfamiliar legal and regulatory requirements. Compliance with these regulatory requirements may impose substantial additional obligations on us and our management, cause us to expend additional time and resources in compliance activities and increase our exposure to penalties or fines for non-compliance with such additional legal requirements. Completed acquisitions could require us to invest further in operational, financial and management information systems and to attract, retain, motivate and effectively manage additional employees. The inability to effectively manage the integration of acquisitions could reduce our focus on subsequent acquisitions and current operations, which, in turn, could negatively impact our results of operations and growth. Our financial condition and results of operations may fluctuate significantly from period to period, based on whether or not significant acquisitions are completed in particular periods.

        Any acquisition involves potential risks, including, among other things:

•

the validity of our assumptions about estimated proved reserves, future production, commodity prices, revenues, capital expenditures, operating expenses and costs;

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an inability to obtain satisfactory title to the assets we acquire;

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•

a decrease in our liquidity by using a significant portion of our available cash or borrowing capacity to finance acquisitions;

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a significant increase in our interest expense or financial leverage if we incur additional debt to finance acquisitions;

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the assumption of unknown liabilities, losses or costs for which we obtain no or limited indemnity or other recourse;

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the diversion of management's attention from other business concerns;

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an inability to hire, train or retain qualified personnel to manage and operate our growing assets; and

•

the occurrence of other significant changes, such as impairment of oil and natural gas properties, goodwill or other intangible assets, asset devaluation or restructuring charges.

Properties we acquire may not produce as projected, and we may be unable to determine reserve potential, identify liabilities associated with the properties that we acquire or obtain protection from sellers against such liabilities.

        Acquiring oil and natural gas properties requires us to assess reservoir and infrastructure characteristics, including recoverable reserves, development and operating costs and potential environmental and other liabilities. Such assessments are inexact and inherently uncertain. In connection with the assessments, we perform a review of the subject properties, but such a review will not reveal all existing or potential problems. In the course of our due diligence, we may not inspect every well or pipeline. We cannot necessarily observe structural and environmental problems, such as pipe corrosion, when an inspection is made. We may not be able to obtain contractual indemnities from the seller for liabilities created prior to our purchase of the property. We may be required to assume the risk of the physical condition of the properties in addition to the risk that the properties may not perform in accordance with our expectations.

We may incur losses as a result of title defects in the properties in which we invest.

        It is our practice in acquiring oil and natural gas leases or interests not to incur the expense of retaining lawyers to examine the title to the mineral interest. Rather, we rely upon the judgment of oil and natural gas lease brokers or landmen who perform the fieldwork in examining records in the appropriate governmental office before attempting to acquire a lease in a specific mineral interest.

        Prior to the drilling of an oil or natural gas well, however, it is the normal practice in our industry for the person or company acting as the operator of the well to obtain a preliminary title review to ensure there are no obvious defects in title to the well. Frequently, as a result of such examinations, certain curative work must be done to correct defects in the marketability of the title, and such curative work entails expense. Our failure to cure any title defects may delay or prevent us from utilizing the associated mineral interest, which may adversely impact our ability in the future to increase production and reserves. Additionally, undeveloped acreage has greater risk of title defects than developed acreage. If there are any title defects or defects in assignment of leasehold rights in properties in which we hold an interest, we will suffer a financial loss.

Competition in the oil and natural gas industry is intense, which may adversely affect our ability to succeed.

        The oil and natural gas industry is intensely competitive, and we compete with other companies that have greater resources than us. Many of these companies not only explore for and produce oil and natural gas, but also carry on midstream and refining operations and market petroleum and other

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products on a regional, national or worldwide basis. These companies may be able to pay more for productive oil and natural gas properties and exploratory prospects or define, evaluate, bid for and purchase a greater number of properties and prospects than our financial or human resources permit. In addition, these companies may have a greater ability to continue exploration activities during periods of low oil and natural gas market prices. Our larger competitors may be able to absorb the burden of present and future federal, state, local and other laws and regulations more easily than we can, which would adversely affect our competitive position. Our ability to acquire additional properties and to discover reserves in the future will be dependent upon our ability to evaluate and select suitable properties and to consummate transactions in a highly competitive environment. In addition, because we have fewer financial and human resources than many companies in our industry, we may be at a disadvantage in bidding for exploratory prospects and producing reserves.

        The oil and natural gas industry is characterized by rapid and significant technological advancements and introductions of new products and services using new technologies. As others use or develop new technologies, we may be placed at a competitive disadvantage or competitive pressures may force us to implement those new technologies at substantial costs. In addition, other oil and natural gas companies may have greater financial, technical and personnel resources that allow them to enjoy technological advantages and may in the future allow them to implement new technologies before we can. We may not be able to respond to these competitive pressures and implement new technologies on a timely basis or at an acceptable cost. If one or more of the technologies we use now or in the future were to become obsolete or if we are unable to use the most advanced commercially available technology, our business, financial condition and results of operations could be materially adversely affected.

Our use of 2-D and 3-D seismic data is subject to interpretation and may not accurately identify the presence of oil and natural gas, which could adversely affect the results of our drilling operations.

        Even when properly used and interpreted, 2-D and 3-D seismic data and visualization techniques are only tools used to assist geoscientists in identifying subsurface structures and hydrocarbon indicators and do not enable the interpreter to know whether hydrocarbons are, in fact, present in those structures. In addition, the use of 3-D seismic and other advanced technologies requires greater predrilling expenditures than traditional drilling strategies, and we could incur losses as a result of such expenditures. As a result, our drilling activities may not be successful or economical.

Conservation measures and technological advances could reduce demand for oil and natural gas.

        Fuel conservation measures, alternative fuel requirements, increasing consumer demand for alternatives to oil and natural gas, technological advances in fuel economy and energy generation devices could reduce demand for oil and natural gas. The impact of the changing demand for oil and natural gas services and products may have a material adverse effect on our business, financial condition, results of operations and cash flows.

The marketability of our production is dependent upon transportation and other facilities, certain of which we do not control. When these facilities are unavailable, our operations can be interrupted and our revenues reduced.

        The marketability of our production depends in part upon the availability, proximity and capacity of transportation facilities owned by third parties. Our oil production is transported from the wellhead to our tank batteries by our gathering system. Our purchasers then transport the oil by truck to a pipeline for transportation. Our natural gas production is generally transported by our gathering lines from the wellhead to an interconnection point with the purchaser. We do not control these trucks and other third-party transportation facilities and our access to them may be limited or denied. Insufficient production from our wells to support the construction of pipeline facilities by our purchasers or a

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significant disruption in the availability of our or third-party transportation facilities or other production facilities could adversely impact our ability to deliver to market or produce our production and thereby cause a significant interruption in our operations.

        In the past we have been required to flare a portion of our natural gas production for a number of reasons, including the fact that (1) our well is not yet tied into the third-party gathering system, (2) the pressures on the third-party gathering system are too high to allow additional production from our well to be transported or (3) our production is prorated due to high demand on the third-party gathering system. During the first quarter of 2013, we flared an average of approximately 2.0 MMcf/D, or 331 BOE/D, of natural gas, which included both residue gas and NGL production. We expect to continue flaring approximately 3.0 MMcf/D to 4.0 MMcf/D until further improvements can be made to certain gathering systems near our wells. These improvements are scheduled to come on line in mid-2013, although we cannot guarantee that this will be the case.

        Also, the transfer of our oil, natural gas and NGLs on third-party pipelines may be curtailed or delayed if it does not meet the quality specifications of the pipeline owners. Our access to transportation options, including trucks owned by third parties, can also be affected by U.S. federal and state regulation of oil and natural gas production and transportation, general economic conditions and changes in supply and demand. If, in the future, we are unable, for any sustained period, to implement acceptable delivery or transportation arrangements or encounter production-related difficulties, we may be required to shut in or curtail production. Any such shut in or curtailment, or an inability to obtain favorable terms for delivery of our production, would adversely affect our financial condition and results of operations.

Our operations are subject to various governmental regulations which require compliance that can be burdensome and expensive.

        Our operations are subject to various federal, state and local governmental regulations that may be changed from time to time in response to economic and political conditions. Matters subject to regulation include discharge permits for drilling operations, drilling bonds, reports concerning operations, the spacing of wells, unitization and pooling of properties and taxation. From time to time, regulatory agencies have imposed price controls and limitations on production by restricting the rate of flow of oil and natural gas wells below actual production capacity to conserve supplies of oil and natural gas. In addition, the production, handling, storage, transportation, remediation, emission and disposal of oil and natural gas, by-products thereof and other substances and materials produced or used in connection with oil and natural gas operations are subject to regulation under federal, state and local laws and regulations, primarily relating to protection of human health and the environment. Failure to comply with these laws and regulations may result in the assessment of sanctions, including administrative, civil or criminal penalties, permit revocations, requirements for additional pollution controls and injunctions limiting or prohibiting some or all of our operations. Moreover, these laws and regulations have continually imposed increasingly strict requirements for water and air pollution control and solid waste management. Significant expenditures may be required to comply with governmental laws and regulations applicable to us. We believe the trend of more expansive and stricter environmental legislation and regulations will continue for the foreseeable future. Please read "Business—Regulation" for a description of the laws and regulations that affect us.

Federal and state legislative and regulatory initiatives relating to hydraulic fracturing could result in increased costs and additional operating restrictions or delays.

        Hydraulic fracturing is an important common practice that is used to stimulate production of hydrocarbons, particularly natural gas, from tight formations, including shales. The process involves the injection of water, sand and chemicals under pressure into formations to fracture the surrounding rock and stimulate production. The federal Safe Drinking Water Act (the "SDWA") regulates the

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underground injection of substances through the Underground Injection Control ("UIC") program. Hydraulic fracturing is generally exempt from regulation under the UIC program, and the hydraulic fracturing process is typically regulated by state oil and natural gas commissions. The Environmental Protection Agency (the "EPA") however, has recently taken the position that hydraulic fracturing with fluids containing diesel fuel is subject to regulation under the UIC program, specifically as "Class II" UIC wells. At the same time, the EPA has commenced a study of the potential environmental impacts of hydraulic fracturing activities, and a committee of the U.S. House of Representatives is also conducting an investigation of hydraulic fracturing practices. Moreover, the EPA commenced a study regarding the environmental effects of hydraulic fracturing activities. The EPA issued a Progress Report in December 2012 and a final draft is anticipated by 2014 for peer review and public comment. As part of these studies, both the EPA and the House committee have requested that certain companies provide them with information concerning the chemicals used in the hydraulic fracturing process. These studies, depending on their results, could spur initiatives to regulate hydraulic fracturing under the SDWA or otherwise. Legislation to amend the SDWA to repeal the exemption for hydraulic fracturing from the definition of "underground injection" and require federal permitting and regulatory control of hydraulic fracturing, as well as legislative proposals to require disclosure of the chemical constituents of the fluids used in the fracturing process, were proposed in recent sessions of Congress. The U.S. Congress continues to consider legislation to amend the SDWA.

        Federal agencies are also considering additional regulation of hydraulic fracturing. On October 20, 2011, the EPA announced its intention to propose federal Clean Water Act regulations by 2014 governing wastewater discharges from hydraulic fracturing and certain other natural gas operations.

        On August 16, 2012, the EPA published final regulations under the federal Clean Air Act, as amended, (the "CAA") that establish new air emission controls for oil and natural gas production and natural gas processing operations. Specifically, the EPA's rule package includes New Source Performance Standards to address emissions of sulfur dioxide and volatile organic compounds ("VOCs") and a separate set of emission standards to address hazardous air pollutants frequently associated with oil and natural gas production and processing activities. The final rule includes a 95% reduction in VOCs emitted by requiring the use of reduced emission completions or "green completions" on all hydraulically-fractured wells constructed or refractured after January 1, 2015. The rules also establish specific new requirements regarding emissions from compressors, controllers, dehydrators, storage tanks and other production equipment. The EPA received numerous requests for reconsideration of these rules from both industry and the environmental community, and court challenges to the rules were also filed. The EPA intends to issue revised rules in 2013 that are likely responsive to some of these requests. For example, on April 12, 2013, the EPA published a proposed amendment extending compliance dates for certain storage vessels. The final revised rules could require modifications to our operations or increase our capital and operating costs without being offset by increased product capture. At this point, we cannot predict the final regulatory requirements or the cost to comply with such requirements with any certainty. The U.S. Department of the Interior has also announced its intention to propose a new rule regulating hydraulic fracturing activities on federal lands, including requirements for disclosure, wellbore integrity and handling of flowback water.

        Several states, including Texas have adopted or are considering adopting regulations that could restrict or prohibit hydraulic fracturing in certain circumstances and/or require the disclosure of the composition of hydraulic fracturing fluids. The Texas Railroad Commission recently adopted rules and regulations requiring that the well operator disclose the list of chemical ingredients subject to the requirements of the federal Occupational Safety and Health Act ("OSHA") for disclosure on an internet website and also file the list of chemicals with the Texas Railroad Commission with the well completion report. The total volume of water used to hydraulically fracture a well must also be disclosed to the public and filed with the Texas Railroad Commission. We plan to use hydraulic fracturing extensively in connection with the development and production of certain of our oil and

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natural gas properties and any increased federal, state, local, foreign or international regulation of hydraulic fracturing could reduce the volume of reserves that we can economically recover, which could materially and adversely affect our revenues and results of operations.

        There has been increasing public controversy regarding hydraulic fracturing with regard to use of fracturing fluids, impacts on drinking water supplies, use of waters and the potential for impacts to surface water, groundwater and the environment generally. A number of lawsuits and enforcement actions have been initiated across the country implicating hydraulic fracturing practices. If new laws or regulations that significantly restrict hydraulic fracturing are adopted, such laws could make it more difficult or costly for us to perform fracturing to stimulate production from tight formations as well as make it easier for third parties opposing the hydraulic fracturing process to initiate legal proceedings based on allegations that specific chemicals used in the fracturing process could adversely affect groundwater. In addition, if hydraulic fracturing is further regulated at the federal or state level, our fracturing activities could become subject to additional permitting and financial assurance requirements, more stringent construction specifications, increased monitoring, reporting and recordkeeping obligations, plugging and abandonment requirements and also to attendant permitting delays and potential increases in costs. Such legislative changes could cause us to incur substantial compliance costs, and compliance or the consequences of any failure to comply by us could have a material adverse effect on our financial condition and results of operations. At this time, it is not possible to estimate the impact on our business of newly enacted or potential federal or state legislation governing hydraulic fracturing.

Our operations may be exposed to significant delays, costs and liabilities as a result of environmental, health and safety requirements applicable to our business activities.

        We may incur significant delays, costs and liabilities as a result of federal, state and local environmental, health and safety requirements applicable to our exploration, development and production activities. These laws and regulations may require us to obtain a variety of permits or other authorizations governing our air emissions, water discharges, waste disposal or other environmental impacts associated with drilling, producing and other operations; regulate the sourcing and disposal of water used in the drilling, fracturing and completion processes; limit or prohibit drilling activities in certain areas and on certain lands lying within wilderness, wetlands, frontier and other protected areas; require remedial action to prevent or mitigate pollution from former operations such as plugging abandoned wells or closing earthen pits; and/or impose substantial liabilities for spills, pollution or failure to comply with regulatory filings. In addition, these laws and regulations may restrict the rate of oil or natural gas production. These laws and regulations are complex, change frequently and have tended to become increasingly stringent over time. Failure to comply with these laws and regulations may result in the assessment of administrative, civil and criminal penalties, imposition of cleanup and site restoration costs and liens, the suspension or revocation of necessary permits, licenses and authorizations, the requirement that additional pollution controls be installed and, in some instances, issuance of orders or injunctions limiting or requiring discontinuation of certain operations.

        Under certain environmental laws that impose strict as well as joint and several liability, we may be required to remediate contaminated properties currently or formerly operated by us or facilities of third parties that received waste generated by our operations regardless of whether such contamination resulted from the conduct of others or from consequences of our own actions that were in compliance with all applicable laws at the time those actions were taken. In addition, claims for damages to persons or property, including natural resources, may result from the environmental, health and safety impacts of our operations. In addition, the risk of accidental spills or releases from our operations could expose us to significant liabilities under environmental laws. Moreover, public interest in the protection of the environment has increased dramatically in recent years. The trend of more expansive and stringent environmental legislation and regulations applied to the oil and natural gas industry could

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continue, resulting in increased costs of doing business and consequently affecting profitability. To the extent laws are enacted or other governmental action is taken that restricts drilling or imposes more stringent and costly operating, waste handling, disposal and cleanup requirements, our business, prospects, financial condition or results of operations could be materially adversely affected.

Restrictions on drilling activities intended to protect certain species of wildlife may adversely affect our ability to conduct drilling activities in some of the areas where we operate.

        Oil and natural gas operations in our operating areas can be adversely affected by seasonal or permanent restrictions on drilling activities designed to protect various wildlife. Seasonal restrictions may limit our ability to operate in protected areas and can intensify competition for drilling rigs, oilfield equipment, services, supplies and qualified personnel, which may lead to periodic shortages when drilling is allowed. These constraints and the resulting shortages or high costs could delay our operations and materially increase our operating and capital costs. Permanent restrictions imposed to protect endangered species could prohibit drilling in certain areas or require the implementation of expensive mitigation measures. The designation of previously unprotected species in areas where we operate as threatened or endangered could cause us to incur increased costs arising from species protection measures or could result in limitations on our exploration, development and production activities that could have an adverse impact on our ability to develop and produce our reserves.

The adoption of derivatives legislation by the U.S. Congress could have an adverse effect on our ability to use derivative instruments to reduce the effect of commodity price, interest rate and other risks associated with our business.

        The adoption of derivatives legislation by the U.S. Congress could have an adverse effect on our ability to use derivative instruments to reduce the effect of commodity price, interest rate and other risks associated with our business. The U.S. Congress adopted the Dodd-Frank Wall Street Reform and Consumer Protection Act (HR 4173), which, among other provisions, establishes federal oversight and regulation of the over-the-counter derivatives market and entities that participate in that market. The legislation was signed into law by the President on July 21, 2010, and required the Commodities Futures Trading Commission ("CFTC") and the SEC to promulgate rules and regulations implementing the legislation within 360 days from the date of enactment. In its rulemaking under the legislation, the CFTC proposed regulations to set position limits for certain futures and option contracts in the major energy markets and for swaps that are their economic equivalents. Certain bona fide hedging transactions or positions would be exempt from these position limits. Although the CFTC has promulgated numerous final rules based on its proposals, it is not possible at this time to predict when the CFTC will finalize its proposed regulations or the effect of such regulations on our business. The financial reform legislation may also require us to comply with margin requirements and with certain clearing and trade-execution requirements in connection with our existing or future derivative activities, although the application of those provisions to us is uncertain at this time. The financial reform legislation may also require the counterparties to our derivative instruments to spin off some of their derivatives activities to separate entities, which may not be as creditworthy as the current counterparties. This legislation and any new regulations could significantly increase the cost of derivative contracts (including through requirements to post collateral which could adversely affect our available liquidity), materially alter the terms of derivative contracts, reduce the availability of derivatives to protect against risks we encounter, reduce our ability to monetize or restructure our derivative contracts in existence at that time and increase our exposure to less creditworthy counterparties. If we reduce or change the way we use derivative instruments as a result of the legislation and regulations, our results of operations may become more volatile and our cash flows may be less predictable, which could adversely affect our ability to plan for and fund capital expenditures. Finally, the legislation was intended, in part, to reduce the volatility of oil and natural gas prices, which some legislators attributed to speculative trading in derivatives and commodity instruments related to

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oil and natural gas. Our revenues could therefore be adversely affected if a consequence of the legislation and regulations is to lower commodity prices. Any of these consequences could have a material adverse effect on our consolidated financial condition, results of operations or cash flows.

Proposed changes to U.S. tax laws, if adopted, could have an adverse effect on our business, financial condition, results of operations and cash flows.

        The U.S. President's Fiscal Year 2014 Budget Proposal includes provisions that would, if enacted, make significant changes to U.S. tax laws. These changes include, but are not limited to, eliminating the immediate deduction for intangible drilling and development costs, eliminating the deduction from income for domestic production activities relating to oil and natural gas exploration and development, repealing the percentage depletion allowance for oil and natural gas properties and extending the amortization period for certain geological and geophysical expenditures. These proposed changes in the U.S. tax laws, if adopted, or other similar changes that reduce or eliminate deductions currently available with respect to oil and natural gas exploration and development, could adversely affect our business, financial condition, results of operations and cash flows.

The adoption of climate change legislation by Congress could result in increased operating costs and reduced demand for the oil and natural gas we produce.

        Many nations have agreed to limit emissions of "greenhouse gases" ("GHGs") pursuant to the United Nations Framework Convention on Climate Change, also known as the "Kyoto Protocol." Methane, a primary component of natural gas, and carbon dioxide, a byproduct of the burning of oil, natural gas, and refined petroleum products, are GHGs regulated by the Kyoto Protocol. Although the United States is not participating in the Kyoto Protocol at this time, several states or geographic regions have adopted legislation and regulations to reduce emissions of GHGs. The EPA has adopted two sets of related rules, one of which purports to regulate emissions of GHGs from motor vehicles and the other of which regulates emissions of GHGs from certain large stationary sources of emissions such as power plants or industrial facilities. The EPA finalized the motor vehicle rule in April 2010 and it became effective in January 2011. The EPA adopted the stationary source rule, also known as the "Tailoring Rule," in May 2010, and it also became effective in January 2011. Additionally, in September 2009, the EPA issued a final rule requiring the reporting of GHG emissions from specified large GHG emission sources in the U.S., including NGLs fractionators and local natural gas/distribution companies, beginning in 2011 for emissions occurring in 2010. In November 2010, the EPA expanded its existing GHG reporting rule to include onshore and offshore oil and natural gas production and onshore processing, transmission, storage and distribution facilities, which may include certain of our facilities, beginning in 2012 for emissions occurring in 2011. In addition, the EPA has continued to adopt GHG regulations of other industries, such as the March 2012 proposed GHG rule restricting future development of coal-fired power plants. As a result of this continued regulatory focus, future GHG regulations of the oil and natural gas industry remain a possibility.

        In addition, the U.S. Congress has from time to time considered adopting legislation to reduce emissions of GHGs and almost one-half of the states have already taken legal measures to reduce emissions of GHGs primarily through the planned development of GHG emission inventories and/or regional GHG cap and trade programs. Although the U.S. Congress has not adopted such legislation at this time, it may do so in the future and many states continue to pursue regulations to reduce GHG emissions. Most of these cap and trade programs work by requiring major sources of emissions, such as electric power plants, or major producers of fuels, such as refineries and natural gas processing plants, to acquire and surrender emission allowances corresponding with their annual emissions of GHGs. The number of allowances available for purchase is reduced each year until the overall GHG emission reduction goal is achieved. As the number of GHG emission allowances declines each year, the cost or value of allowances is expected to escalate significantly.

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        Restrictions on GHG emissions that may be imposed in various states could adversely affect the oil and natural gas industry. While we are subject to certain federal GHG monitoring and reporting requirements, our operations are not adversely impacted by existing federal, state and local climate change initiatives and, at this time, it is not possible to accurately estimate how future laws or regulations addressing GHG emissions would impact our business.

        In addition, there has been public discussion that climate change may be associated with extreme weather conditions such as more intense hurricanes, thunderstorms, tornados and snow or ice storms, as well as rising sea levels. Another possible consequence of climate change is increased volatility in seasonal temperatures. Some studies indicate that climate change could cause some areas to experience temperatures substantially colder than their historical averages. Extreme weather conditions can interfere with our production and increase our costs and damage resulting from extreme weather may not be fully insured. However, at this time, we are unable to determine the extent to which climate change may lead to increased storm or weather hazards affecting our operations.

We will be subject to certain requirements of Section 404 of the Sarbanes-Oxley Act. If we are unable to timely comply with Section 404 or if the costs related to compliance are significant, our profitability, stock price, results of operations and financial condition could be materially adversely affected.

        We will be required to comply with certain provisions of Section 404 of the Sarbanes-Oxley Act as early as December 31, 2014. Section 404 requires that we document and test our internal control over financial reporting and issue management's assessment of our internal control over financial reporting. This section also requires that our independent registered public accounting firm opine on those internal controls upon becoming a large accelerated filer, as defined in the SEC rules, or otherwise ceasing to qualify as an emerging growth company under the JOBS Act. We are evaluating our existing controls against the standards adopted by the Committee of Sponsoring Organizations of the Treadway Commission. During the course of our ongoing evaluation and integration of the internal control over financial reporting, we may identify areas requiring improvement, and we may have to design enhanced processes and controls to address issues identified through this review. For example, we anticipate the need to hire additional administrative and accounting personnel to conduct our financial reporting.

        We believe that the out-of-pocket costs, diversion of management's attention from running the day-to-day operations and operational changes caused by the need to comply with the requirements of Section 404 of the Sarbanes-Oxley Act could be significant. If the time and costs associated with such compliance exceed our current expectations, our results of operations could be adversely affected.

        We cannot be certain at this time that we will be able to successfully complete the procedures, certification and attestation requirements of Section 404 or that we or our independent registered public accounting firm will not identify material weaknesses in our internal control over financial reporting. If we fail to comply with the requirements of Section 404 or if we or our independent registered public accounting firm identify and report such material weaknesses, the accuracy and timeliness of the filing of our annual and quarterly reports may be materially adversely affected and could cause investors to lose confidence in our reported financial information, which could have a negative effect on the stock price of our common stock. In addition, a material weakness in the effectiveness of our internal control over financial reporting could result in an increased chance of fraud and the loss of customers, reduce our ability to obtain financing and require additional expenditures to comply with these requirements, each of which could have a material adverse effect on our business, results of operations and financial condition.

Loss of our information and computer systems could adversely affect our business.

        We are heavily dependent on our information systems and computer based programs, including our well operations information, seismic data, electronic data processing and accounting data. If any of such

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programs or systems were to fail or create erroneous information in our hardware or software network infrastructure, possible consequences include our loss of communication links, inability to find, produce, process and sell oil and natural gas and inability to automatically process commercial transactions or engage in similar automated or computerized business activities. Any such consequence could have a material adverse effect on our business.

A terrorist attack or armed conflict could harm our business.

        Terrorist activities, anti-terrorist efforts and other armed conflicts involving the United States or other countries may adversely affect the United States and global economies and could prevent us from meeting our financial and other obligations. If any of these events occur, the resulting political instability and societal disruption could reduce overall demand for oil and natural gas, potentially putting downward pressure on demand for our services and causing a reduction in our revenues. Oil and natural gas related facilities could be direct targets of terrorist attacks, and our operations could be adversely impacted if infrastructure integral to our customers' operations is destroyed or damaged. Costs for insurance and other security may increase as a result of these threats, and some insurance coverage may become more difficult to obtain, if available at all.

Risks Related to this Offering and Our Common Stock

Athlon Energy Inc.'s only material asset is its interest in Athlon Holdings LP, and Athlon Energy Inc. is accordingly dependent upon distributions from Athlon Holdings LP to pay taxes, make payments under the tax receivable agreement and pay dividends.

        Athlon Energy Inc. is a holding company and has no material assets other than its ownership of New Holdings Units in Athlon Holdings LP. Athlon Energy Inc. has no independent means of generating revenue. Athlon Energy Inc. intends to cause Athlon Holdings LP to make distributions to its unitholders, which include Athlon Energy Inc., members of our management team and certain employees, in an amount sufficient to cover all applicable taxes at assumed tax rates, payments under the tax receivable agreement and dividends, if any, declared by it. To the extent that Athlon Energy Inc. needs funds, and Athlon Holdings LP is restricted from making such distributions under applicable law or regulation or under the terms of its financing arrangements, or is otherwise unable to provide such funds, it could materially adversely affect our liquidity and financial condition.

        Athlon Holdings LP entered into an amended and restated credit agreement dated as of March 19, 2013, which we refer to as our credit agreement. In addition, Athlon Holdings LP entered into an indenture dated as of April 17, 2013 governing its 7³/8% senior notes due 2021. Each of these agreements includes a restricted payment covenant, which places certain restrictions on the ability of Athlon Holdings LP to make distributions to its unitholders, including Athlon Energy Inc.

Our largest stockholder controls a significant percentage of our common stock, and their interests may conflict with those of our other stockholders.

        Upon completion of this offering, assuming the Apollo Funds or their affiliates make no additional purchases of our common stock and based on an estimated valuation of Athlon using an assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus), the Apollo Funds will beneficially own in the aggregate approximately 68.6% of the combined voting power of our common stock (or approximately 65.8% if the underwriters option to purchase additional shares of common stock from the Apollo Funds is exercised in full). As a result, the Apollo Funds will be able to control matters requiring stockholder approval, including the election of directors, changes to our organizational documents and significant corporate transactions. This concentration of ownership makes it unlikely that any other holder or group of holders of our common stock will be able to affect the way we are managed or the direction of our business. In addition, the

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stockholders agreement that we will enter into in connection with this offering will provide that, except as otherwise required by applicable law, if the Apollo Funds hold: (a) at least 50% of our outstanding common stock, they will have the right to designate no fewer than that number of directors that would constitute a majority of our Board of Directors; (b) at least 30% but less than 50% of our outstanding common stock, they will have the right to designate up to three director nominees; (c) at least 20% but less than 30% of our outstanding common stock, they will have the right to designate up to two director nominees; and (d) at least 10% but less than 20% of our outstanding common stock, they will have the right to designate up to one director nominee. The agreement also provides that if the size of our Board of Directors is increased or decreased at any time to other than seven directors, Apollo's nomination rights will be proportionately increased or decreased, respectively, rounded up to the nearest whole number. In addition, the agreement provides that if the Apollo Funds hold at least 30% of our outstanding common stock, we will cause any committee of our Board of Directors to include in its membership at least one of the Apollo Funds nominees, except to the extent that such membership would violate applicable securities laws or stock exchange or stock market rules. The interests of the Apollo Funds with respect to matters potentially or actually involving or affecting us, such as future acquisitions, financings and other corporate opportunities and attempts to acquire us, may conflict with the interests of our other stockholders. Given this concentrated ownership, the Apollo Funds would have to approve any potential acquisition of us. In addition, certain of our directors are currently employees of Apollo. These directors' duties as employees of Apollo may conflict with their duties as our directors, and the resolution of these conflicts may not always be in our or your best interest.

We expect to be a "controlled company" within the meaning of the NYSE rules and, as a result, will qualify for, and intend to rely on, exemptions from certain corporate governance requirements.

        Upon the closing of this offering, the Apollo Funds will continue to control a majority of our voting common stock. As a result, we expect to qualify as a "controlled company" within the meaning of the NYSE corporate governance standards. Under the NYSE rules, a company of which more than 50% of the voting power for the election of directors is held by an individual, group or another company is a "controlled company" and may elect not to comply with certain NYSE corporate governance requirements, including:

•

the requirement that a majority of our Board of Directors consists of independent directors;

•

the requirement that we have a nominating and corporate governance committee that is composed entirely of independent directors with a written charter addressing the committee's purpose and responsibilities;

•

the requirement that we have a compensation committee that is composed entirely of independent directors with a written charter addressing the committee's purpose and responsibilities; and

•

the requirement for an annual performance evaluation of the nominating and corporate governance and compensation committees.

        Following this offering, we intend to utilize certain of these exemptions. As a result, we will not have a majority of independent directors nor will our nominating and corporate governance and compensation committees consist entirely of independent directors, and we will not be required to have an annual performance evaluation of the nominating and corporate governance and compensation committees. Please read "Management—Composition of Our Board of Directors." Accordingly, you will not have the same protections afforded to stockholders of companies that are subject to such corporate governance requirements.

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The corporate opportunity provisions in our amended and restated certificate of incorporation could enable the Apollo Funds, our equity sponsor, to benefit from corporate opportunities that might otherwise be available to us.

        Subject to the limitations of applicable law, our amended and restated certificate of incorporation, among other things:

•

permits us to enter into transactions with entities in which one or more of our officers or directors are financially or otherwise interested;

•

permits any of our stockholders, officers or directors to conduct business that competes with us and to make investments in any kind of property in which we may make investments; and

•

provides that if any director or officer of one of our affiliates who is also one of our officers or directors becomes aware of a potential business opportunity, transaction or other matter (other than one expressly offered to that director or officer in writing solely in his or her capacity as our director or officer), that director or officer will have no duty to communicate or offer that opportunity to us, and will be permitted to communicate or offer that opportunity to such affiliates and that director or officer will not be deemed to have (1) acted in a manner inconsistent with his or her fiduciary or other duties to us regarding the opportunity or (2) acted in bad faith or in a manner inconsistent with our best interests.

        As a result, the Apollo Funds or their affiliates may become aware, from time to time, of certain business opportunities, such as acquisition opportunities, and may direct such opportunities to other businesses in which they have invested, in which case we may not become aware of or otherwise have the ability to pursue such opportunity. Further, such businesses may choose to compete with us for these opportunities. As a result, our renouncing our interest and expectancy in any business opportunity that may be from time to time presented to the Apollo Funds and their affiliates could adversely impact our business or prospects if attractive business opportunities are procured by such parties for their own benefit rather than for ours. Please read "Description of Capital Stock."

We have engaged in transactions with our affiliates and expect to do so in the future. The terms of such transactions and the resolution of any conflicts that may arise may not always be in our or our stockholders' best interests.

        We have engaged in transactions and expect to continue to engage in transactions with affiliated companies, as described under the caption "Certain Relationships and Related Party Transactions." The resolution of any conflicts that may arise in connection with any related party transactions that we have entered into with the Apollo Funds or their affiliates, including pricing, duration or other terms of service, may not always be in our or our stockholders' best interests because the Apollo Funds may have the ability to influence the outcome of these conflicts. For a discussion of potential conflicts, please read "—Our largest stockholder controls a significant percentage of our common stock, and their interests may conflict with those of our other stockholders."

We will incur increased costs as a result of being a public company, which may significantly affect our financial condition.

        As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. We will incur costs associated with our public company reporting requirements. We also anticipate that we will incur costs associated with corporate governance requirements, including requirements under the Sarbanes-Oxley Act, as well as rules implemented by the SEC and the Financial Industry Regulatory Authority. We expect these rules and regulations to increase our legal and financial compliance costs and to make some activities more time-consuming and costly, particularly after we are no longer an "emerging growth company." We also expect these rules and regulations may make it more difficult and more expensive for us to obtain director and officer

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liability insurance and we may be required to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage. As a result, it may be more difficult for us to attract and retain qualified individuals to serve on our Board of Directors or as executive officers.

        We will remain an "emerging growth company" for up to five years. After we are no longer an "emerging growth company," we expect to incur significant additional expenses and devote substantial management effort toward ensuring compliance with those requirements applicable to companies that are not "emerging growth companies," including Section 404 of the Sarbanes-Oxley Act. Please read "—Risks Related to the Oil and Natural Gas Industry and Our Business—We will be subject to certain requirements of Section 404 of the Sarbanes-Oxley Act. If we are unable to timely comply with Section 404 or if the costs related to compliance are significant, our profitability, stock price, results of operations and financial condition could be materially adversely affected."

We are an "emerging growth company" and we cannot be certain if the reduced disclosure requirements applicable to emerging growth companies will make our common stock less attractive to investors.

        We are an "emerging growth company," as defined in the JOBS Act, and we intend to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies, including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act, reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder approval of any golden parachute payments not previously approved. We intend to take advantage of these reporting exemptions until we are no longer an "emerging growth company." We cannot predict if investors will find our common stock less attractive because we will rely on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be more volatile.

        We will remain an emerging growth company for up to five years, although we will lose that status sooner if we have more than $1.0 billion of revenues in a fiscal year, have more than $700 million in market value of our common stock held by non-affiliates as of any June 30 or issue more than $1.0 billion of non-convertible debt over a rolling three-year period.

        Under the JOBS Act, "emerging growth companies" can delay adopting new or revised accounting standards until such time as those standards apply to private companies. We have irrevocably elected not to avail ourselves of this exemption from new or revised accounting standards and, therefore, we will be subject to the same new or revised accounting standards as other public companies that are not "emerging growth companies."

        To the extent that we rely on any of the exemptions available to emerging growth companies, you will receive less information about our executive compensation and internal control over financial reporting than issuers that are not emerging growth companies. If some investors find our common stock to be less attractive as a result, there may be a less active trading market for our common stock and our stock price may be more volatile.

There has been no public market for our common stock and if the price of our common stock fluctuates significantly, your investment could lose value.

        Prior to this offering, there has been no public market for our common stock. Although we have been approved to list our common stock on the NYSE, we cannot assure you that an active public market will develop for our common stock or that our common stock will trade in the public market subsequent to this offering at or above the initial public offering price. If an active public market for

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our common stock does not develop, the stock price and liquidity of our common stock will be materially and adversely affected. If there is a thin trading market or "float" for our common stock, the market price for our common stock may fluctuate significantly more than the stock market as a whole. Without a large float, our common stock is less liquid than the stock of companies with broader public ownership and, as a result, the stock price of our common stock may be more volatile. In addition, in the absence of an active public trading market, investors may be unable to liquidate their investment in us. The initial offering price, which will be negotiated between us and the underwriters, may not be indicative of the stock price for our common stock after this offering. In addition, the stock market is subject to significant price and volume fluctuations, and the price of our common stock could fluctuate widely in response to several factors, including:

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our quarterly or annual operating results;

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changes in our earnings estimates;

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investment recommendations by securities analysts following our business or our industry;

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additions or departures of key personnel;

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changes in the business, earnings estimates or market perceptions of our competitors;

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our failure to achieve operating results consistent with securities analysts' projections;

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changes in industry, general market or economic conditions; and

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announcements of legislative or regulatory change.

        The stock market has experienced extreme price and volume fluctuations in recent years that have significantly affected the quoted prices of the securities of many companies, including companies in our industry. The changes often appear to occur without regard to specific operating performance. The price of our common stock could fluctuate based upon factors that have little or nothing to do with our company and these fluctuations could materially reduce our stock price.

Future sales of our common stock, or the perception that such future sales may occur, may cause our stock price to decline.

        Sales of substantial amounts of our common stock in the public market after this offering, or the perception that these sales may occur, could cause the market price of our common stock to decline. Please read "Shares Eligible for Future Sale." In addition, the sale of these shares could impair our ability to raise capital through the sale of additional common or preferred stock. After this offering, we will have 82,122,646 shares of common stock outstanding, excluding awards under the Athlon Energy Inc. 2013 Incentive Award Plan and New Holdings Units that are exchangeable for shares of our common stock. All of the shares sold in this offering, except for any shares purchased by our affiliates, will be freely tradable.

        The Apollo Funds and our directors and executive officers will be subject to agreements that limit their ability to sell our common stock held by them. These holders cannot sell or otherwise dispose of any shares for a period of at least 180 days after the date of this prospectus without the prior written approval of Citigroup Global Markets Inc. However, these lock-up agreements are subject to certain specific exceptions, including transfers of common stock as a bona fide gift or by will or intestate succession and transfers to such person's immediate family or to a trust or to an entity controlled by such holder, provided that the recipient of the shares agrees to be bound by the same restrictions on sales. In the event that one or more of our stockholders sells a substantial amount of our common stock in the public market, or the market perceives that such sales may occur, the price of our stock could decline.

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        As soon as practicable after this offering, we intend to file a registration statement with the SEC on Form S-8 providing for the registration of 8,400,000 shares of our common stock issued or reserved for issuance under the Athlon Energy Inc. 2013 Incentive Award Plan that we plan to adopt prior to the completion of this offering. Subject to the satisfaction of vesting conditions and the expiration of lock-up agreements, shares registered under our registration statement on Form S-8 will be available for resale immediately in the public market without restriction.

        We cannot predict the size of future issuances of shares of our common stock or the effect, if any, that future issuances and sales of shares of our common stock will have on the market price of our common stock. Sales of substantial amounts of our common stock (including shares issued in connection with an acquisition), or the perception that such sales could occur, may adversely affect prevailing market prices of our common stock.

The underwriters of this offering may waive or release parties to the lock-up agreements entered into in connection with this offering, which could adversely affect the price of our common stock.

        The Apollo Funds and our directors and executive officers have entered into lock-up agreements with respect to their common stock, pursuant to which they are subject to certain resale restrictions for a period of 180 days following the date of this prospectus. Citigroup Global Markets Inc., at any time and without notice, may release all or any portion of the common stock subject to the foregoing lock-up agreements. If the restrictions under the lock-up agreements are waived, then common stock will be available for sale into the public markets, which could cause the market price of our common stock to decline and impair our ability to raise capital.

If securities or industry analysts do not publish research or reports about our business, if they adversely change their recommendations regarding our common stock or if our operating results do not meet their expectations, our stock price could decline.

        The trading market for our common stock will be influenced by the research and reports that industry or securities analysts publish about us or our business. If one or more of these analysts cease coverage of our company or fail to publish reports on us regularly, we could lose visibility in the financial markets, which in turn could cause our stock price or trading volume to decline. Moreover, if one or more of the analysts who cover our company downgrades our common stock or if our operating results do not meet their expectations, our stock price could decline.

Purchasers in this offering will experience immediate dilution and will experience further dilution with the future exercise of stock options granted to certain of our executive officers under their respective employment agreements.

        The initial public offering price is substantially higher than the pro forma net tangible book value per share of our outstanding common stock. As a result, you will experience immediate and substantial dilution of approximately $11.54 per share, representing the difference between our net tangible book value per share as of March 31, 2013 after giving effect to this offering and an assumed initial public offering price of $19.00 per share (which is the midpoint of the price range set forth on the cover page of the prospectus). A $1.00 decrease in the assumed initial public offering price of $19.00 per share (which is the midpoint of the price range set forth on the cover page of this prospectus) would decrease our net tangible book value per share after giving effect to this offering by $0.18 per share, and decrease the dilution to new investors by $0.82 per share, assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. If the options granted to certain of our executive officers under their respective employment agreements are exercised in full, the investors in this offering will experience further dilution. Please read "Dilution."

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We may issue preferred stock whose terms could adversely affect the voting power or value of our common stock.

        Our amended and restated certificate of incorporation authorizes us to issue, without the approval of our stockholders, one or more classes or series of preferred stock having such designations, preferences, limitations and relative rights, including preferences over our common stock respecting dividends and distributions, as our Board of Directors may determine. The terms of one or more classes or series of preferred stock could adversely impact the voting power or value of our common stock. For example, we might grant holders of preferred stock the right to elect some number of our directors in all events or on the happening of specified events or the right to veto specified transactions. Similarly, the repurchase or redemption rights or liquidation preferences we might assign to holders of preferred stock could affect the residual value of the common stock.

Provisions in our amended and restated certificate of incorporation and amended and restated bylaws and Delaware law make it more difficult to effect a change in control of our company, which could adversely affect the price of our common stock.

        The existence of some provisions in our amended and restated certificate of incorporation and amended and restated bylaws and the DGCL could delay or prevent a change in control of our company, even if that change would be beneficial to our stockholders. Our amended and restated certificate of incorporation and amended and restated bylaws contain provisions that may make acquiring control of our company difficult, including:

•

a classified Board of Directors, so that only approximately one-third of our directors are elected each year;

•

provisions regulating the ability of our stockholders to nominate directors for election or to bring matters for action at annual meetings of our stockholders;

•

limitations on the ability of our stockholders to call a special meeting and act by written consent;

•

the ability of our Board of Directors to adopt, amend or repeal our bylaws;

•

the requirement that the affirmative vote of holders representing at least 66²/3% of the voting power of all outstanding shares of capital stock (or a majority of the voting power of all outstanding shares of capital stock if Apollo beneficially owns at least 33¹/3% of the voting power of all such outstanding shares and votes in favor of the proposed action) be obtained to amend our amended and restated bylaws, to remove directors or to amend our certificate of incorporation; and

•

the authorization given to our Board of Directors to issue and set the terms of preferred stock without the approval of our stockholders.

        These provisions also could discourage proxy contests and make it more difficult for you and other stockholders to elect directors and take other corporate actions. As a result, these provisions could make it more difficult for a third party to acquire us, even if doing so would benefit our stockholders, which may limit the price that investors are willing to pay in the future for our common stock.

We do not intend to pay cash dividends on our common stock in the foreseeable future, and therefore only appreciation of the price of our common stock will provide a return to our stockholders.

        We anticipate that we will retain all future earnings, if any, to finance the growth and development of our business. We do not intend to pay cash dividends in the foreseeable future. Any future determination as to the declaration and payment of cash dividends will be at the discretion of our Board of Directors and will depend upon our financial condition, results of operations, contractual restrictions, capital requirements, business prospects and other factors deemed relevant by our Board of Directors. In addition, the terms of our debt agreements prohibit us from paying dividends and making other distributions. As a result, only appreciation of the price of our common stock, which may not occur, will provide a return to our stockholders.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

        This prospectus contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933 (the "Securities Act") and Section 21E of the Securities and Exchange Act of 1934 (the "Exchange Act"). Forward-looking statements are subject to a number of risks and uncertainties, many of which are beyond our control. All statements, other than statements of historical fact included in this prospectus, are forward-looking statements. When used in this prospectus, the words "could," "should," "believe," "anticipate," "intend," "estimate," "expect," "may," "continue," "predict," "plan," "potential," "project," "forecast" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain such identifying words.

        Forward-looking statements may include statements about:

•

our business strategy;

•

our estimated reserves and the present value thereof;

•

our technology;

•

our cash flows and liquidity;

•

our financial strategy, budget, projections and future operating results;

•

realized commodity prices;

•

timing and amount of future production of reserves;

•

availability of drilling and production equipment;

•

availability of pipeline capacity;

•

availability of oilfield labor;

•

the amount, nature and timing of capital expenditures, including future development costs;

•

availability and terms of capital;

•

drilling of wells, including statements made about future horizontal drilling activities;

•

competition;

•

government regulations;

•

marketing of production;

•

exploitation or property acquisitions;

•

costs of exploiting and developing our properties and conducting other operations;

•

general economic and business conditions;

•

competition in the oil and natural gas industry;

•

effectiveness of our risk management activities;

•

environmental and other liabilities;

•

counterparty credit risk;

•

taxation of the oil and natural gas industry;

•

developments in other countries that produce oil and natural gas;

•

uncertainty regarding future operating results;

49

•

plans and objectives of management or our sponsors; and

•

plans, objectives, expectations and intentions contained in this prospectus that are not historical.

        All forward-looking statements speak only as of the date of this prospectus. You should not place undue reliance on these forward-looking statements. Although we believe that our plans, intentions and expectations reflected in or suggested by the forward-looking statements we make in this prospectus are reasonable, we can give no assurance that these plans, intentions or expectations will be achieved when anticipated or at all. We disclose important factors that could cause our actual results to differ materially from our expectations under "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" and elsewhere in this prospectus. These factors include, but are not limited to risks related to:

•

variations in the market demand for, and prices of, oil, natural gas and NGLs;

•

uncertainties about our estimated reserves;

•

the adequacy of our capital resources and liquidity including, but not limited to, access to additional borrowing capacity under our credit agreement;

•

general economic and business conditions;

•

risks associated with negative developments in the capital markets;

•

failure to realize expected value creation from property acquisitions;

•

uncertainties about our ability to replace reserves and economically develop our current reserves;

•

drilling results;

•

potential financial losses or earnings reductions from our commodity price risk management programs;

•

potential adoption of new governmental regulations;

•

the availability of capital on economic terms to fund our capital expenditures and acquisitions;

•

risks associated with our substantial indebtedness; and

•

our ability to satisfy future cash obligations and environmental costs.

        These cautionary statements qualify all forward-looking statements attributable to us or persons acting on our behalf.

        There are numerous uncertainties inherent in estimating quantities of proved reserves and in projecting future rates of production and timing of development expenditures. Oil and natural gas reserve engineering is and must be recognized as a subjective process of estimating underground accumulations of oil and natural gas that cannot be measured in any exact way, and estimates of other engineers might differ materially from those included herein. The accuracy of any reserve estimate is a function of the quality of available data and of engineering and geological interpretation, and estimates may justify revisions based on the results of drilling, testing and production activities. Accordingly, reserve estimates are often materially different from the quantities of oil and natural gas that are ultimately recovered.

50

USE OF PROCEEDS

        We expect the net proceeds from this offering to be approximately $278.5 million, assuming an initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus) and after deducting estimated underwriting discounts and commissions and estimated offering expenses of approximately $21.5 million, in the aggregate. Each $1.00 decrease in the public offering price would decrease our net proceeds by approximately $14.9 million.

        We intend to use the net proceeds of this offering, after deducting estimated underwriting discounts and comissions and estimated offering expenses, to purchase New Holdings Units from Athlon Holdings LP. The table below sets forth the anticipated use by Athlon Holdings LP of the net proceeds received by it as a result of our purchase of the New Holdings Units:

	Net Proceeds		Percentage of Net Proceeds
	(in thousands)
Reduce outstanding indebtedness under our credit agreement	$	72,000		26	%
Provide additional liquidity for use in our drilling program		206,500		74	%
Total	$	278,500		100	%

        Remaining net proceeds, if any, will be used for working capital and general corporate purposes, including potential acquisitions.

        As of July 22, 2013, we had $72 million of outstanding borrowings under our credit agreement. Our credit agreement matures on March 19, 2018 and bears interest at a variable rate, which was approximately 1.7% as of July 22, 2013. The borrowings to be repaid were incurred primarily to fund our acquisitions and development program. Amounts repaid under our credit agreement may be reborrowed at any time.

        We will not receive any proceeds from sales by the Apollo Funds, including pursuant to the underwriters' option to purchase additional shares of common stock.

        Affiliates of certain of the underwriters are lenders under our credit agreement and, accordingly, will receive a portion of the net proceeds from this offering. Please read "Underwriting (Conflicts of Interest)."

DIVIDEND POLICY

        We do not anticipate declaring or paying any cash dividends to holders of our common stock in the foreseeable future. We intend to retain future earnings, if any, to finance the expansion of our business. Our future dividend policy is within the discretion of our Board of Directors and will depend upon various factors, including our results of operations, financial condition, capital requirements and investment opportunities. In addition, our debt agreements restrict our ability to pay cash dividends to holders of our common stock.

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CAPITALIZATION

        The following table sets forth the cash and capitalization as of March 31, 2013 of:

•

Athlon Holdings LP; and

•

Athlon Energy Inc. on a pro forma as adjusted basis to give effect to (1) the reorganization transactions described under "Corporate Reorganization," (2) the offering by Athlon Holdings LP of $500 million of 7³/8% senior notes due 2021 in April 2013, and the application of the net proceeds thereof, and (3) the sale of shares of our common stock in this offering at an assumed initial public offering price of $19.00 per share (which is the midpoint of the price range set forth on the cover page of this prospectus), our receipt of an estimated $278.5 million of net proceeds from this offering after deducting estimated underwriting discounts and commissions and estimated offering expenses and the use of those net proceeds as described under the caption "Use of Proceeds."

        You should read the following table in conjunction with "Management's Discussion and Analysis of Financial Condition and Results of Operations" and our consolidated financial statements and related notes appearing elsewhere in this prospectus.

	As of March 31, 2013
	Athlon Holdings LP1 Actual		Athlon Energy Inc. Pro Forma As Adjusted1,2
	(in thousands)
Cash and cash equivalents	$	3,379	$	275,103
Debt:
Credit agreement3	$	291,426	$	—
Former second lien term loan agreement4		125,000		—
73/8% senior notes due 2021		—		500,000
Total debt		416,426		500,000
Partners' equity		433,330		—
Stockholders' equity:
Preferred stock, $0.01 per share; 50,000,000 shares authorized, no shares issued and outstanding (pro forma as adjusted)		—		—
Common stock, $0.01 par value; 500,000,000 shares authorized (pro forma as adjusted); 82,122,646 shares issued and outstanding (pro forma as adjusted)		—		821
Additional paid-in capital		—		625,371
Accumulated deficit5		—		(22,773	)
Total stockholders' equity		—		603,419
Noncontrolling interest		—		9,429
Total equity		433,330		612,848
Total capitalization	$	849,756	$	1,112,848

¹

Athlon Energy Inc. was incorporated on April 1, 2013 in Delaware as a holding company and will not conduct any material business operations prior to the completion of this offering. The data in this table has been derived from the historical consolidated financial statements and other financial information included in this prospectus which pertain to the assets, liabilities, revenues and expenses of Athlon Holdings LP, our accounting predecessor.

²

Each $1.00 decrease in the public offering price would decrease our net proceeds from this offering by approximately $14.9 million.

³

We used a portion of the net proceeds from the senior notes offering to repay approximately $288.3 million of outstanding borrowings under our credit agreement. As of July 22, 2013, we had $72 million of outstanding borrowings under our credit agreement.

⁴

We used a portion of the net proceeds from the senior notes offering to repay in full and terminate our former second lien term loan agreement.

⁵

Upon completion of our corporate reorganization, we will recognize deferred tax liabilities and assets for temporary differences between the historical cost basis and tax basis of our assets and liabilities. Based on estimates of those temporary differences as of March 31, 2013, a net deferred tax liability of approximately $19.0 million will be recognized with a corresponding charge to earnings.

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DILUTION

        Purchasers of our common stock in this offering will experience immediate and substantial dilution in the net tangible book value per share of the common stock for accounting purposes. Our net tangible book value (tangible assets less total liabilities) as of March 31, 2013, after giving pro forma effect to the transactions described under "Corporate Reorganization," and our senior notes offering, was approximately $336.5 million, or $5.07 per share of common stock. Pro forma net tangible book value per share is determined by dividing our pro forma net tangible book value by our shares of common stock that will be outstanding immediately prior to the closing of this offering, including giving effect to the reorganization transactions described under "Corporate Reorganization" and our senior notes offering. Assuming an initial public offering price of $19.00 per share (which is the midpoint of the price range set forth on the cover page of this prospectus), after giving effect to the sale of the shares in this offering and further assuming the receipt of the estimated net proceeds (after deducting estimated underwriting discounts and commissions and estimated offering expenses), our adjusted pro forma net tangible book value as of March 31, 2013 would have been approximately $612.8 million, or $7.46 per share. This represents an immediate increase in the net tangible book value of $2.39 per share to our existing stockholders and an immediate dilution to new investors purchasing shares in this offering of $11.54 per share, resulting from the difference between the offering price and the pro forma as adjusted net tangible book value after this offering. The following table illustrates the per share dilution to new investors purchasing shares in this offering:

Assumed initial public offering price per share			$	19.00
Pro forma net tangible book value per share as of March 31, 2013 (prior to this offering)	$	5.07
Increase per share attributable to new investors in the offering	$	2.39
As adjusted pro forma net tangible book value per share (after this offering)				7.46
Dilution in pro forma net tangible book value per share to new investors in this offering1			$	11.54

¹

If the initial public offering price were to decrease by $1.00 per share, then dilution in pro forma net tangible book value per share to new investors in this offering would equal $10.72.

        The following table sets forth, as of March 31, 2013, the number of shares of common stock held by our existing stockholders immediately prior to the closing of this offering, and by the new investors at the assumed initial public offering price of $19.00 per share (which is the midpoint of the price range set forth on the cover page of this prospectus), together with the total consideration paid and average price per share paid by each of these groups, before deducting estimated underwriting discounts and commissions and estimated offering expenses:

	Shares Purchased					Total Consideration
											Average Price Per Share
	Number		Percent			Amount		Percent
						(in millions)
Existing stockholders		66,333,172		80.8	%	$	361.9		54.7	%	$	5.46
New investors		15,789,474		19.2	%		300.0		45.3	%		19.00
Total		82,122,646		100.0	%	$	661.9		100.0	%		8.06

        The data in the table excludes 8,400,000 shares of common stock initially reserved for issuance under the Athlon Energy Inc. 2013 Incentive Award Plan (which amount may be increased each year in accordance with the terms of the plan).

        If the underwriters' option to purchase additional shares of common stock from the Apollo Funds is exercised in full, the number of shares held by new investors will be increased to 18,157,895, or approximately 22.1% of our outstanding shares of common stock.

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SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA

        The following selected consolidated balance sheets data, statements of operations data and statements of cash flows data as of and for the years ended December 31, 2012 and 2011 are derived from, and qualified by reference to, the audited consolidated financial statements of Athlon Holdings LP, our accounting predecessor, included elsewhere in this prospectus and should be read in conjunction with those financial statements and notes thereto as well as "Management's Discussion and Analysis of Financial Condition and Results of Operations." The following selected consolidated balance sheet data as of March 31, 2013 and the consolidated statements of operations data and statements of cash flow data for the three months ended March 31, 2013 and 2012 are derived from, and qualified by reference to, the unaudited consolidated financial statements of Athlon Holdings LP, our accounting predecessor, included elsewhere in this prospectus and should be read in conjunction with those financial statements and notes thereto as well as "Management's Discussion and Analysis of Financial Condition and Results of Operations." The financial information included in this prospectus may not be indicative of our future results of operations, financial position and cash flows.

	Three months ended March 31,						Year ended December 31,
	2013			2012			2012			2011
	(unaudited)
	(in thousands)
Consolidated Statements of Operations Data:
Revenues:
Oil	$	45,659		$	27,433		$	128,081		$	51,193
Natural gas		3,367			1,448			8,415			3,521
NGLs		5,720			4,351			20,615			10,967
Total revenues		54,746			33,232			157,111			65,681
Expenses:
Production:
Lease operating		7,237			4,699			25,503			13,328
Production, severance and ad valorem taxes		3,694			2,350			10,438			4,727
Depletion, depreciation and amortization		18,053			9,614			54,456			19,747
General and administrative		3,282			2,597			9,678			7,724
Acquisition costs		57			—			876			9,519
Derivative fair value loss (gain)		6,849			22,711			(9,293	)		7,959
Other operating		194			130			562			404
Total expenses		39,366			42,101			92,220			63,408
Operating income (loss)		15,380			(8,869	)		64,891			2,273
Interest expense		4,474			1,495			9,949			2,932
Income (loss) before income taxes		10,906			(10,364	)		54,942			(659	)
Income tax provision (benefit)		27			(364	)		1,928			470
Net income (loss)	$	10,879		$	(10,000	)	$	53,014		$	(1,129	)
Consolidated Statements of Cash Flows Data:
Cash provided by (used in):
Operating activities	$	30,397		$	20,723		$	95,302		$	18,872
Investing activities		(90,560	)		(58,498	)		(347,259	)		(465,475	)
Financing activities		54,671			12,982			228,798			471,627
Consolidated Balance Sheets Data (at period end):
Cash and cash equivalents	$	3,379					$	8,871		$	32,020
Total assets		916,535						852,298			561,823
Total debt		416,426						362,000			170,000
Partners' equity		433,330						420,877			327,452

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MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and related notes appearing elsewhere in this prospectus. The following discussion and analysis contains forward-looking statements, including, without limitation, statements relating to our plans, strategies, objectives, expectations, intentions and resources. Actual results could differ materially from those discussed in these forward-looking statements. We do not undertake to update, revise or correct any of the forward-looking information unless required to do so under federal securities laws. Readers are cautioned that such forward-looking statements should be read in conjunction with our disclosures under "Cautionary Note Regarding Forward-Looking Statements" and "Risk Factors" appearing elsewhere in this prospectus.

Overview

        We are an independent exploration and production company focused on the acquisition, development and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. The Permian Basin spans portions of Texas and New Mexico and consists of three primary sub-basins: the Delaware Basin, the Central Basin Platform and the Midland Basin. All of our properties are located in the Midland Basin. Our drilling activity is currently focused on the low-risk vertical development of stacked pay zones, including the Spraberry, Wolfcamp, Cline, Strawn, Atoka and Mississippian formations, which we refer to collectively as the Wolfberry play. We are a returns-focused organization and have targeted the Wolfberry play in the Midland Basin because of its favorable operating environment, consistent reservoir quality across multiple target horizons, long-lived reserve characteristics and high drilling success rates.

        We were founded in August 2010 by a group of executives from Encore Acquisition Company following its acquisition by Denbury Resources, Inc. With an average of approximately 20 years of industry experience and over 10 years of history working together, our founding management has a proven track record of working as a team to acquire, develop and exploit oil and natural gas reserves in the Permian Basin as well as other resource plays in North America.

        Our acreage position was 124,925 gross (98,348 net) acres at May 31, 2013, which we group into three primary areas based on geographic location within the Midland Basin: Howard, Midland & Other and Glasscock. From the time we began operations in January 2011 through May 31, 2013, we have operated up to eight vertical drilling rigs simultaneously and have drilled 230 gross vertical Wolfberry wells with a 99% success rate across all three areas. This activity has allowed us to identify and de-risk our multi-year inventory of 4,902 gross (3,857 net) vertical drilling locations, while also identifying 1,079 gross (931 net) horizontal drilling locations in specific areas based on the geophysical and technical data as of May 31, 2013. As we continue to expand our vertical drilling activity to our undeveloped acreage, we expect to identify additional horizontal drilling locations.

        As of December 31, 2012, we had 86 MMBOE of proved reserves. In addition, we have grown our production to 11,957 BOE/D for June 2013. As of December 31, 2012, our estimated proved reserves were approximately 58% oil, 22% NGLs and 20% natural gas and approximately 30% were proved developed reserves. Our PUDs include 597 gross (560 net) potential vertical drilling locations.

Our Acquisition History

        A significant portion of our historical growth has been achieved through acquisitions. Since our inception in August 2010, we have completed two significant acquisitions and seven bolt-on acquisitions. At the time of each acquisition, based on internal engineering estimates, these properties collectively contributed approximately 3,600 BOE/D of production and approximately 43 MMBOE of proved reserves.

55

        On January 6, 2011, we acquired certain oil and natural gas properties and related assets, consisting of 19,210 gross (18,833 net) acres in the Permian Basin in West Texas, from SandRidge Exploration and Production, LLC ("SandRidge," and when discussing the transaction, the "SandRidge acquisition") for $156.0 million in cash, which was financed through borrowings under our credit agreement and capital contributions from partners. The SandRidge properties included approximately 1,600 BOE/D of production and approximately 19.1 MMBOE of proved reserves at the time of acquisition based on internal reserve reports.

        On October 3, 2011, we acquired certain oil and natural gas properties and related assets, consisting of 41,044 gross (34,400 net) acres in the Permian Basin in West Texas, from Element Petroleum, LP ("Element," and when discussing the transaction, the "Element acquisition") for $253.2 million in cash, which was financed through borrowings under our credit agreement and capital contributions from partners. The Element properties included approximately 1,400 BOE/D of production and approximately 16.4 MMBOE of proved reserves at the time of acquisition based on internal reserve reports.

Factors That Significantly Affect Our Financial Condition and Results of Operations

        Our revenues, cash flow from operations and future growth depend substantially on factors beyond our control, such as economic, political and regulatory developments and competition from other sources of energy. Oil and natural gas prices have historically been volatile and may fluctuate widely in the future due to a variety of factors, including but not limited to, prevailing economic conditions, supply and demand of hydrocarbons in the marketplace, actions by speculators and geopolitical events such as wars or natural disasters. Sustained periods of low prices for oil, natural gas or NGLs could materially and adversely affect our financial condition, our results of operations, the quantities of oil and natural gas that we can economically produce and our ability to access capital.

        We use commodity derivative instruments, such as swaps, puts and collars to manage and reduce price volatility and other market risks associated with our oil production. These arrangements are structured to reduce our exposure to commodity price decreases, but they can also limit the benefit we might otherwise receive from commodity price increases. Our risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions. We elected not to designate our current portfolio of commodity derivative contracts as hedges. Therefore, changes in fair value of these derivative instruments are recognized in earnings. Please read "—Quantitative and Qualitative Disclosures About Market Risk" for additional discussion of our commodity derivative contracts.

        The prices we realize on the oil we produce are affected by the ability to transport crude oil to the Cushing, Oklahoma transport hub and the Gulf Coast refineries. Periodically, logistical and infrastructure constraints at the Cushing, Oklahoma transport hub have resulted in an oversupply of crude oil at Midland, Texas and thus lower prices for Midland WTI. These lower prices have adversely affected the prices we realize on oil sales and increased our differential to NYMEX WTI. However, several projects have recently been implemented and several more are underway to ease these transportation difficulties which we believe could reduce our differentials to NYMEX in the future. We have also entered into Midland-Cushing differential swaps for 2013 to mitigate the adverse effects of any further widening of the Midland-Cushing WTI differential (the difference between Midland WTI and Cushing WTI).

        Like all businesses engaged in the exploration and production of oil and natural gas, we face the challenge of natural production declines. As initial reservoir pressures are depleted, oil and natural gas production from a given well naturally decreases. Thus, an oil and natural gas exploration and production company depletes part of its asset base with each unit of oil or natural gas it produces. We attempt to overcome this natural decline by drilling to find additional reserves and acquiring more

56

reserves than we produce. Our future growth will depend on our ability to enhance production levels from our existing reserves and to continue to add reserves in excess of production in a cost effective manner. Our ability to make capital expenditures to increase production from our existing reserves and to add reserves through drilling is dependent on our capital resources and can be limited by many factors, including our ability to access capital in a cost-effective manner and to timely obtain drilling permits and regulatory approvals.

        As with our historical acquisitions, any future acquisitions could have a substantial impact on our financial condition and results of operations. In addition, funding future acquisitions may require us to incur additional indebtedness or issue additional equity.

        The volumes of oil and natural gas that we produce are driven by several factors, including:

•

success in drilling wells, including exploratory wells, and the recompletion of existing wells;

•

the amount of capital we invest in the leasing and development of our oil and natural gas properties;

•

facility or equipment availability and unexpected downtime;

•

delays imposed by or resulting from compliance with regulatory requirements; and

•

the rate at which production volumes on our wells naturally decline.

Factors That Significantly Affect Comparability of Our Financial Condition and Results of Operations

        Our historical financial condition and results of operations for the periods presented may not be comparable, either from period to period or going forward, for the following reasons:

        Corporate Reorganization.    The historical consolidated financial statements included in this prospectus are based on the financial statements of Athlon Holdings LP, our accounting predecessor, prior to the reorganization transactions as described under "Corporate Reorganization." As a result, the historical financial data may not give you an accurate indication of what our actual results would have been if the reorganization transactions had been completed at the beginning of the periods presented or what our future results of operations are likely to be.

        Public Company Expenses.    Upon completion of this offering, we expect to incur direct, incremental general and administrative ("G&A") expenses as a result of being a publicly traded company, including, but not limited to, costs associated with annual and quarterly reports to stockholders, tax return preparation, independent auditor fees, investor relations activities, registrar and transfer agent fees, incremental director and officer liability insurance costs and independent director compensation. We estimate these direct, incremental G&A expenses initially to total approximately $2.0 million per year. These direct, incremental G&A expenses are not included in our historical results of operations.

        Income Taxes.    Athlon Holdings LP, our accounting predecessor, is a limited partnership not subject to federal income taxes. Accordingly, no provision for federal income taxes has been provided for in our historical results of operations because taxable income was passed through to Athlon Holdings LP's partners. However, we are a corporation under the Internal Revenue Code, subject to federal income taxes at a statutory rate of 35% of pretax earnings.

        Increased Drilling Activity.    We began operations in January 2011 and gradually added operated vertical drilling rigs. We currently operate seven vertical drilling rigs on our properties, and we have operated between five and eight drilling rigs since October 2011. Our 2013 development capital budget is approximately $317 million, including $15 million for infrastructure, leasing and capitalized workovers, and we expect to drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest

57

$33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells. We expect to take delivery of our first horizontal rig in the third quarter of 2013 and our second horizontal rig in the second quarter of 2014. In 2014, we intend to expand to an eight-rig vertical drilling program. In addition, we intend to implement a horizontal drilling program in the second half of 2013 which we expect will significantly increase our capital expenditures in future periods. The ultimate amount of capital that we expend may fluctuate materially based on market conditions and our drilling results in each particular year.

        Element Acquisition.    On October 3, 2011, we acquired certain oil and natural gas properties and related assets, consisting of 41,044 gross (34,400 net) acres in the Element acquisition for $253.2 million in cash, which was financed through borrowings under our credit agreement and capital contributions from partners. Only three months of production from the Element properties is included in our results of operations for 2011.

        Financing Arrangements.    Through March 31, 2013, we had incurred $416.4 million of indebtedness, including $291.4 million under our credit agreement and $125 million under a second lien term loan agreement, which we refer to as our former second lien term loan. In April 2013, we issued $500 million in aggregate principal amount of 7³/8% senior notes due 2021. We used the proceeds of our senior notes offering to repay a portion of the amounts outstanding under our credit agreement, to repay in full and terminate our former second lien term loan, to make a $75 million distribution to Class A limited partners of Athlon Holdings LP and for general corporate purposes. Our senior notes bear interest at a rate significantly higher than the rates under our credit agreement which will result in higher interest expense in future periods as compared to our historical interest expense. In the future, we may incur additional indebtedness to fund our acquisition and development activities. Please read "—Capital Commitments, Capital Resources, and Liquidity—Liquidity" for additional discussion of our financing arrangements.

Sources of Our Revenues

        Our revenues are derived from the sale of oil, natural gas and NGLs within the continental United States and do not include the effects of derivatives. For 2012, oil and NGLs represented approximately 80% of our total production volumes. Our revenues may vary significantly from period to period as a result of changes in volumes of production sold or changes in commodity prices.

        NYMEX WTI and Henry Hub prompt month contract prices are widely-used benchmarks in the pricing of oil and natural gas. The following table provides the high and low prices for NYMEX WTI and Henry Hub prompt month contract prices and our differential to the average of those benchmark prices for the periods indicated:

	Three months ended March 31,						Year ended December 31,
	2013			2012			2012			2011
Oil
NYMEX WTI High	$	97.94		$	109.77		$	109.77		$	113.93
NYMEX WTI Low		90.12			96.36			77.69			75.67
Differential to Average NYMEX WTI		(10.11	)		(3.66	)		(6.29	)		(3.03	)
Natural Gas
NYMEX Henry Hub High		4.07			3.10			3.90			4.85
NYMEX Henry Hub Low		3.11			2.13			1.91			2.99
Differential to Average NYMEX Henry Hub		(0.07	)		(0.03	)		(0.13	)		(0.54	)

        We normally sell production to a relatively small number of customers. In 2012, three purchasers individually accounted for more than 10% of our revenues: Pecos Gathering & Marketing (43%);

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Occidental Petroleum Corporation (29%); and DCP Midstream (12%). If any significant customer decided to stop purchasing oil and natural gas from us, our revenues could decline and our operating results and financial condition could be harmed. However, based on the current demand for oil and natural gas, and the availability of other purchasers, we believe that the loss of any one or all of our significant customers would not have a material adverse effect on our financial condition and results of operations, as crude oil and natural gas are fungible products with well-established markets and numerous purchasers.

Principal Components of Our Cost Structure

        Lease Operating Expense.    LOE includes the daily costs incurred to bring crude oil and natural gas out of the ground and to the market, together with the daily costs incurred to maintain our producing properties. Such costs include field personnel compensation, utilities, maintenance and workover expenses related to our oil and natural gas properties.

        Production, Severance and Ad Valorem Taxes.    Production and severance taxes are paid on produced oil, natural gas and NGLs based on a percentage of revenues from production sold at fixed rates established by federal, state or local taxing authorities. In general, the production and severance taxes we pay correlate to the changes in oil and natural gas revenues. We are also subject to ad valorem taxes in the counties where our production is located. Ad valorem taxes are generally based on the valuation of our oil and natural gas properties and are assessed annually.

        Depreciation, Depletion and Amortization.    Depreciation, depletion and amortization ("DD&A") is the expensing of the capitalized costs incurred to acquire, explore and develop oil and natural gas. We use the full cost method of accounting for oil and natural gas activities. Please read "—Critical Accounting Policies and Estimates—Method of Accounting for Oil and Natural Gas Properties" for further discussion.

        General and Administrative Expense.    G&A expense consists of company overhead, including payroll and benefits for our corporate staff, costs of maintaining our headquarters, costs of managing our production and development operations, audit and other professional fees and legal compliance costs. Upon completion of this offering, G&A expense will also include public company expenses as described above under "—Factors That Significantly Affect Comparability of Our Financial Condition and Results of Operations—Public Company Expenses."

        Interest Expense.    We finance a portion of our working capital requirements, capital expenditures and acquisitions with borrowings under our credit agreement. As a result, we incur interest expense that is affected by both fluctuations in interest rates and our financing decisions. Interest incurred under our debt agreements, the amortization of deferred financing costs (including origination and amendment fees), commitment fees and annual agency fees are included in interest expense. Interest expense is net of capitalized interest on expenditures made in connection with exploration and development projects that are not subject to current amortization. Interest expense will also include interest incurred under our senior notes beginning April 2013 as described above under "—Factors That Significantly Affect Comparability of Our Financial Condition and Results of Operations—Financing Arrangements."

        Derivative Fair Value Loss (Gain).    We utilize commodity derivative contracts to reduce our exposure to fluctuations in the price of oil. We recognize gains and losses associated with our open commodity derivative contracts as commodity prices and the associated fair value of our commodity derivative contracts change. The commodity derivative contracts we have in place are not designated as hedges for accounting purposes. Consequently, these commodity derivative contracts are marked-to-market each quarter with fair value gains and losses recognized currently as a gain or loss in

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our results of operations. Cash flow is only impacted to the extent the actual settlements under the contracts result in making a payment to or receiving a payment from the counterparty.

How We Evaluate Our Operations

        In evaluating our financial results, we focus on the mix of our revenues from oil, natural gas and NGLs, the average realized price from sales of our production, our production margins and our net income. Below are highlights of our financial and operating results for the first quarter of 2013:

•

Our oil, natural gas and NGLs revenues increased 65% to $54.7 million in the first quarter of 2013 as compared to $33.2 million in the first quarter of 2012.

•

Our average daily production volumes increased 94% to 9,959 BOE/D in the first quarter of 2013 as compared to 5,140 BOE/D in the first quarter of 2012. Oil and NGLs represented approximately 81% of our total production volumes in the first quarter of 2013.

•

Our average realized oil price decreased 15% to $84.23 per Bbl in the first quarter of 2013 as compared to $99.29 per Bbl in the first quarter of 2012. Our average realized natural gas price increased 21% to $3.27 per Mcf in the first quarter of 2013 as compared to $2.71 per Mcf in the first quarter of 2012. Our average realized NGL price decreased 26% to $31.34 per Bbl in the first quarter of 2013 as compared to $42.48 per Bbl in the first quarter of 2012.

•

Our production margin increased 67% to $43.8 million in the first quarter of 2013 as compared to $26.2 million in the first quarter of 2012. Total wellhead revenues per BOE decreased by 14% and total production expenses per BOE decreased by 19%. On a per BOE basis, our production margin decreased 13% to $48.84 per BOE in the first quarter of 2013 as compared to $55.92 per BOE for the first quarter of 2012.

•

Our net income was $10.9 million as compared to a net loss of $10.0 million for the first quarter of 2012.

•

We invested $80.9 million in oil and natural gas activities, of which $71.8 million was invested in development and exploration activities, yielding 35 gross (34 net) productive wells, and $9.1 million was invested in acquisitions.

        We also evaluate our rates of return on invested capital in our wells. We believe the quality of our assets combined with the technical capabilities of our management team can generate attractive rates of return as we develop our extensive resource base. Additionally, by focusing on concentrated acreage positions, we can build and own centralized production infrastructure, including saltwater disposal facilities, which enable us to reduce reliance on outside service companies, minimize costs and increase our returns.

        We measure the expected return of our wells based on EUR and the related costs of acquisition, development and production. Based on estimates prepared by our independent reserve engineers, as of December 31, 2012, the wells we expect to drill in 2013 through the Atoka formation in Howard, Midland & Other and Glasscock areas have an average EUR of 141 MBOE (87 MBbls of oil, 150 MMcf of natural gas and 30 MBbls of NGLs), 208 MBOE (95 MBbls of oil, 318 MMcf of natural gas and 60 MBbls of NGLs) and 118 MBOE (73 MBbls of oil, 141 MMcf of natural gas and 22 MBbls of NGLs), respectively. Our average drilling and completion cost per vertical well drilled in the Howard, Midland & Other and Glasscock areas in the first quarter of 2013 was $1.8 million, $2.15 million and $1.8 million, respectively, with average 30-day initial production rates of approximately 130 BOE/D, 190 BOE/D and 100 BOE/D, respectively. Assuming a benchmark crude oil price of $94.71 per Bbl and natural gas price of $2.75 per Mcf, the PUD wells we expect to drill in 2013 in the Howard, Midland & Other and Glasscock areas are targeted to produce an average rate of return of 34%, 43% and 21%, respectively.

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Results of Operations

Comparison of Quarter Ended March 31, 2013 to Quarter Ended March 31, 2012

        Revenues.    The following table provides the components of our revenues for the periods indicated, as well as each period's respective production volumes and average prices:

	Three months ended March 31,				Increase / (Decrease)
	2013		2012		$			%
Revenues (in thousands):
Oil	$	45,659	$	27,433	$	18,226			66	%
Natural gas		3,367		1,448		1,919			133	%
NGLs		5,720		4,351		1,369			31	%
Total revenues	$	54,746	$	33,232	$	21,514			65	%
Average realized prices:
Oil ($/Bbl) (excluding impact of cash settled derivatives)	$	84.23	$	99.29	$	(15.06	)		-15	%
Oil ($/Bbl) (after impact of cash settled derivatives)	$	83.65	$	89.53	$	(5.88	)		-7	%
Natural gas ($/Mcf)	$	3.27	$	2.71	$	0.56			21	%
NGLs ($/Bbl)	$	31.34	$	42.48	$	(11.14	)		-26	%
Combined ($/BOE) (excluding impact of cash settled derivatives)	$	61.08	$	71.05	$	(9.97	)		-14	%
Combined ($/BOE) (after impact of cash settled derivatives)	$	60.73	$	65.28	$	(4.55	)		-7	%
Total production volumes:
Oil (MBbls)		542		276		266			96	%
Natural gas (MMcf)		1,030		534		496			93	%
NGLs (MBbls)		183		102		81			79	%
Combined (MBOE)		896		468		428			91	%
Average daily production volumes:
Oil (Bbls/D)		6,023		3,036		2,987			98	%
Natural gas (Mcf/D)		11,446		5,871		5,575			95	%
NGLs (Bbls/D)		2,028		1,125		903			80	%
Combined (BOE/D)		9,959		5,140		4,819			94	%

        The following table shows the relationship between our average oil and natural gas realized prices as a percentage of average NYMEX prices for the periods indicated. Management uses the realized price to NYMEX margin analysis to analyze trends in our oil and natural gas revenues.

	Three months ended March 31,
	2013			2012
Average realized oil price ($/Bbl)	$	84.23		$	99.29
Average NYMEX ($/Bbl)	$	94.34		$	102.95
Differential to NYMEX	$	(10.11	)	$	(3.66	)
Average realized oil price to NYMEX percentage		89	%		96	%
Average realized natural gas price ($/Mcf)	$	3.27		$	2.71
Average NYMEX ($/Mcf)	$	3.34		$	2.74
Differential to NYMEX	$	(0.07	)	$	(0.03	)
Average realized natural gas price to NYMEX percentage		98	%		99	%

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        Our average realized oil price as a percentage of the average NYMEX price was 89% for the first quarter of 2013 as compared to 96% for the first quarter of 2012. All of our oil contracts include the Midland-Cushing differential, which widened to a negative $7.78 per Bbl in the first quarter of 2013 as compared to a negative $1.51 per Bbl in the first quarter of 2012 primarily due to difficulty transporting oil from the Permian Basin to the Gulf Coast refineries due to lack of logistics and infrastructure. However, several projects have recently been implemented and several more are underway to ease these transportation difficulties which we believe will reduce our differentials to NYMEX in the future. We began to see a tightening of our oil differentials in March and have continued to see improvement into the second quarter of 2013 where the differential has decreased to a negative $0.18 per Bbl average for May 2013. Our average realized natural gas price as a percentage of the average NYMEX price remained stable at 98% for the first quarter of 2013 as compared to 99% for the first quarter of 2012.

        Oil revenues increased 66% from $27.4 million in the first quarter of 2012 to $45.7 million in the first quarter of 2013 as a result of an increase in our oil production volumes of 266 MBbls, partially offset by a $15.06 per Bbl decrease in our average realized oil price. Our higher oil production increased oil revenues by $26.4 million and was primarily the result of our development program in the Permian Basin. Our lower average realized oil price decreased oil revenues by $8.2 million and was primarily due to a lower average NYMEX price, which decreased from $102.95 per Bbl in the first quarter of 2012 to $94.34 per Bbl in the first quarter of 2013, and the widening of our oil differentials as previously discussed.

        Natural gas revenues increased 133% from $1.4 million in the first quarter of 2012 to $3.4 million in the first quarter of 2013 as a result of an increase in our natural gas production volumes of 496 MMcf and a $0.56 per Mcf increase in our average realized natural gas price. Our higher natural gas production increased natural gas revenues by $1.4 million and was primarily the result of our development program in the Permian Basin, partially offset by flaring a portion of our natural gas production as either (1) our well is not yet tied into the third-party gathering system, (2) the pressures on the third-party gathering system are too high to allow additional production from our well to be transported or (3) our production is prorated due to high demand on the third-party gathering system. During the first quarter of 2013, we flared an average of approximately 2.0 MMcf/D, or 331 BOE/D, of natural gas, which included both residue gas and NGL production. We expect to continue flaring approximately 3.0 MMcf/D to 4.0 MMcf/D until further improvements can be made to various gathering systems near our wells, which is scheduled to occur in mid-2013. Our higher average realized natural gas price increased natural gas revenues by $0.6 million and was primarily due to a higher average NYMEX price, which increased from $2.74 per Mcf in the first quarter of 2012 to $3.34 per Mcf in the first quarter of 2013.

        NGL revenues increased 31% from $4.4 million in the first quarter of 2012 to $5.7 million in the first quarter of 2013 as a result of an increase in our NGL production volumes of 81 MBbls, partially offset by an $11.14 per Bbl decrease in our average realized NGL price. Our higher NGL production increased NGL revenues by $3.4 million and was primarily the result of our development program in the Permian Basin, partially offset by flaring a portion of our natural gas as described above. Our lower average realized NGL price decreased NGL revenues by $2.0 million and was primarily due to increased supplies of NGLs from NGL-rich shales in the Permian Basin and other basins including the Eagle Ford and the Williston.

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        Expenses.    The following table summarizes our expenses for the periods indicated:

	Three months ended March 31,					Increase / (Decrease)
	2013		2012			$			%
Expenses (in thousands):
Production:
Lease operating	$	7,237	$	4,699		$	2,538			54	%
Production, severance and ad valorem taxes		3,694		2,350			1,344			57	%
Processing, gathering and overhead		45		24			21			88	%
Total production expenses		10,976		7,073			3,903			55	%
Other:
Depletion, depreciation and amortization		18,053		9,614			8,439			88	%
General and administrative		3,339		2,597			742			29	%
Derivative fair value loss		6,849		22,711			(15,862	)		-70	%
Accretion		149		106			43			41	%
Total operating		39,366		42,101			(2,735	)		-6	%
Interest		4,474		1,495			2,979			199	%
Income tax provision (benefit)		27		(364	)		391			-107	%
Total expenses	$	43,867	$	43,232		$	635			1	%
Expenses (per BOE):
Production:
Lease operating	$	8.07	$	10.05		$	(1.98	)		-20	%
Production, severance and ad valorem taxes		4.12		5.03			(0.91	)		-18	%
Processing, gathering and overhead		0.05		0.05			—			0	%
Total production expenses		12.24		15.13			(2.89	)		-19	%
Other:
Depletion, depreciation and amortization		20.14		20.55			(0.41	)		-2	%
General and administrative		3.73		5.55			(1.82	)		-33	%
Derivative fair value loss		7.64		48.55			(40.91	)		-84	%
Accretion		0.17		0.23			(0.06	)		-26	%
Total operating		43.92		90.01			(46.09	)		-51	%
Interest		4.99		3.20			1.79			56	%
Income tax provision (benefit)		0.03		(0.78	)		0.81			-104	%
Total expenses	$	48.94	$	92.43		$	(43.49	)		-47	%

        Production expenses.    Production expenses attributable to LOE increased 54% from $4.7 million in the first quarter of 2012 to $7.2 million in the first quarter of 2013 as a result of an increase in production volumes from wells drilled, which contributed $4.3 million of additional LOE, partially offset by a $1.98 decrease in the average per BOE rate, which reduced LOE by $1.8 million. The decrease in our average LOE per BOE rate was attributable to wells we successfully drilled and completed in 2012 and the first quarter of 2013 where we are experiencing economies of scale from our drilling program and from savings achieved through 2012 infrastructure projects that have resulted in material efficiencies in our field operations and, in particular, our disposal of water.

        Production expenses attributable to production, severance and ad valorem taxes increased 57% from $2.4 million in the first quarter of 2012 to $3.7 million in the first quarter of 2013 primarily due to higher wellhead revenues, which exclude the effects of commodity derivative contracts, resulting from increased production from our drilling activity. As a percentage of wellhead revenues, production,

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severance, and ad valorem taxes decreased to 6.7% in the first quarter of 2013 as compared to 7.1% in the first quarter of 2012 primarily due to (1) an increase in oil revenues as a percentage of our total revenues, which are taxed at a lower rate than natural gas and NGLs, and (2) an increase in the number of wells brought on production in the first quarter of 2013 as compared to the first quarter of 2012 as we continue to utilize more efficient drilling rigs and reduce our time from spud to rig release. Wells brought on production during the first quarter of 2013 contributed to our production, but will not have ad valorem taxes assessed until 2014.

        DD&A expense.    DD&A expense increased 88% from $9.6 million in the first quarter of 2012 to $18.1 million in the first quarter of 2013 primarily due to an increase in production volumes and an increase in our asset base subject to amortization as a result of our drilling activity in 2012 and the first quarter of 2013.

        G&A expense.    G&A expense increased 29% from $2.6 million in the first quarter of 2012 to $3.3 million in the first quarter of 2013 primarily due to higher payroll and payroll-related costs as we continued to add employees in order to manage our growing asset base.

        Derivative fair value loss.    During the first quarter of 2013, we recorded a $6.8 million derivative fair value loss as compared to a loss of $22.7 million in the first quarter of 2012. The change in our derivative fair value loss was a result of additional oil swaps and basis differential swaps entered into during the first quarter of 2013 and the decrease in the future commodity price outlook during the first quarter of 2013 as compared to the first quarter of 2012, which favorably impacted the fair values of our commodity derivative contracts.

        Interest expense.    Interest expense increased 199% from $1.5 million in the first quarter of 2012 to $4.5 million in the first quarter of 2013 primarily due to higher weighted-average outstanding borrowings under our credit agreement and the issuance of $125 million of debt under our former second lien term loan in September 2012. Our weighted-average outstanding borrowings under our credit agreement were $272.0 million for the first quarter of 2013 as compared to $169.4 million for the first quarter of 2012. Our weighted-average interest rate for total indebtedness was 4.6% for the first quarter of 2013 as compared to 3.5% for the first quarter of 2012. Our weighted-average outstanding borrowings increased in the first quarter of 2013 as compared to the first quarter of 2012 in order to fund our higher level of development and exploration activities during 2012 and the first quarter of 2013.

        The following table provides the components of our interest expense for the periods indicated:

	Three months ended March 31,
						Increase / (Decrease)
	2013			2012
	(in thousands)
Credit agreement	$	1,923		$	1,359	$	564
Former second lien term loan agreement		2,350			—		2,350
Other		243			136		107
Less: interest capitalized		(42	)		—		(42	)
Total	$	4,474		$	1,495	$	2,979

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Comparison of 2012 to 2011

        Revenues.    The following table provides the components of our revenues for the periods indicated, as well as each period's respective production volumes and average prices:

	Year ended December 31				Increase/(Decrease)
	2012		2011		$			%
Revenues (in thousands):
Oil	$	128,081	$	51,193	$	76,888			150	%
Natural gas		8,415		3,521		4,894			139	%
NGLs		20,615		10,967		9,648			88	%
Total revenues	$	157,111	$	65,681	$	91,430			139	%
Average realized prices:
Oil ($/Bbl) (excluding impact of cash settled derivatives)	$	87.90	$	92.08	$	(4.18	)		-5	%
Oil ($/Bbl) (after impact of cash settled derivatives)	$	87.16	$	87.16	$	—			0	%
Natural gas ($/Mcf)	$	2.66	$	3.46	$	(0.80	)		-23	%
NGLs ($/Bbl)	$	34.65	$	45.96	$	(11.31	)		-25	%
Combined ($/BOE) (excluding impact of cash settled derivatives)	$	60.91	$	68.13	$	(7.22	)		-11	%
Combined ($/BOE) (after impact of cash settled derivatives)	$	60.50	$	65.29	$	(4.79	)		-7	%
Total production volumes:
Oil (MBbls)		1,457		556		901			162	%
Natural gas (MMcf)		3,163		1,017		2,146			211	%
NGLs (MBbls)		595		239		356			149	%
Combined (MBOE)		2,579		964		1,615			168	%
Average daily production volumes:
Oil (Bbls/D)		3,981		1,523		2,458			161	%
Natural gas (Mcf/D)		8,641		2,786		5,855			210	%
NGLs (Bbls/D)		1,625		654		971			148	%
Combined (BOE/D)		7,047		2,641		4,406			167	%

        The following table shows the relationship between our average oil and natural gas realized prices as a percentage of average NYMEX prices for the periods indicated. Management uses the realized price to NYMEX margin analysis to analyze trends in our oil and natural gas revenues.

	Year ended December 31,
	2012			2011
Average realized oil price ($/Bbl)	$	87.90		$	92.08
Average NYMEX ($/Bbl)		94.19			95.11
Differential to NYMEX		(6.29	)		(3.03	)
Average realized oil price to NYMEX percentage		93	%		97	%
Average realized natural gas price ($/Mcf)	$	2.66		$	3.46
Average NYMEX ($/Mcf)		2.79			4.00
Differential to NYMEX		(0.13	)		(0.54	)
Average realized natural gas price to NYMEX percentage		95	%		87	%

        Our average realized oil price as a percentage of the average NYMEX price was 93% for 2012 as compared to 97% for 2011. All of our oil contracts include the Midland-Cushing differential, which widened in 2012 due to difficulty transporting oil production from the Permian Basin to the Gulf Coast refineries as a result of lack of logistics and infrastructure. However, several projects have recently been

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implemented and several more are underway to ease these transportation difficulties which we believe could reduce our differentials to NYMEX in the future. Our average realized natural gas price as a percentage of the average NYMEX price improved to 95% for 2012 as compared to 87% for 2011 as a result of a full year of production from the properties acquired from Element, which have a higher percentage of their natural gas contracts weighted to an index that trades closer to the average NYMEX price than the natural gas contracts related to the properties acquired from SandRidge.

        Oil revenues increased 150% from $51.2 million in 2011 to $128.1 million in 2012 as a result of an increase in our oil production volumes of 901 MBbls, partially offset by a $4.18 per Bbl decrease in our average realized oil price. Our higher oil production increased oil revenues by $83.0 million and was primarily the result of a full year of production from our Element acquisition in October 2011, as well as our development program in the Permian Basin. The properties initially acquired from Element contributed approximately 113 MBbls ($10.1 million in revenue) of additional oil production in 2012 as compared to 2011 while our development program contributed approximately 788 MBbls ($72.9 million in revenue) of additional oil production. Our lower average realized oil price decreased oil revenues by $6.1 million and was primarily due to a lower average NYMEX price, which decreased from $95.11 per Bbl in 2011 to $94.19 per Bbl in 2012, and the widening of our oil differentials as previously discussed.

        Natural gas revenues increased 139% from $3.5 million in 2011 to $8.4 million in 2012 as a result of an increase in our natural gas production volumes of 2,146 MMcf, partially offset by a $0.80 per Mcf decrease in our average realized natural gas price. Our higher natural gas production increased natural gas revenues by $7.4 million and was primarily the result of a full year of production from our Element acquisition in October 2011, as well as our development program in the Permian Basin. The properties initially acquired from Element contributed approximately 299 MMcf ($0.8 million in revenue) of additional natural gas production in 2012 as compared to 2011 while our development program contributed approximately 1,847 MMcf ($6.6 million in revenue) of additional natural gas production. Our lower average realized natural gas price decreased natural gas revenues by $2.5 million and was primarily due to a lower average NYMEX price, which decreased from $4.00 per Mcf in 2011 to $2.79 per Mcf in 2012, partially offset by the improvement in our natural gas differentials as previously discussed.

        NGL revenues increased 88% from $11.0 million in 2011 to $20.6 million in 2012 as a result of an increase in our NGL production volumes of 356 MBbls, partially offset by an $11.31 per Bbl decrease in our average realized NGL price. Our higher NGL production increased NGL revenues by $16.4 million and was primarily the result of a full year of production from our Element acquisition in October 2011, as well as our development program in the Permian Basin. The properties initially acquired from Element contributed approximately 50 MBbls ($1.5 million in revenue) of additional NGL production in 2012 as compared to 2011 while our development program contributed approximately 306 MBbls ($14.9 million in revenue) of additional NGL production. Our lower average realized NGL price decreased NGL revenues by $6.7 million and was primarily due to increased supplies of NGLs from NGL-rich shales in the Permian Basin and other basins including the Eagle Ford and the Williston.

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        Expenses.    The following table summarizes our expenses for the periods indicated:

	Year ended December 31,					Increase/(Decrease)
	2012			2011		$			%
Expenses (in thousands):
Production:
Lease operating	$	25,503		$	13,328	$	12,175			91	%
Production, severance and ad valorem taxes		10,438			4,727		5,711			121	%
Processing, gathering and overhead		84			60		24			40	%
Total production expenses		36,025			18,115		17,910			99	%
Other:
Depletion, depreciation and amortization		54,456			19,747		34,709			176	%
General and administrative		9,678			7,724		1,954			25	%
Acquisition costs		876			9,519		(8,643	)		-91	%
Derivative fair value loss (gain)		(9,293	)		7,959		(17,252	)		-217	%
Accretion		478			344		134			39	%
Total operating expenses		92,220			63,408		28,812			45	%
Interest		9,949			2,932		7,017			239	%
Income tax provision		1,928			470		1,458			310	%
Total expenses	$	104,097		$	66,810	$	37,287			56	%
Expenses (per BOE):
Production:
Lease operating	$	9.89		$	13.82	$	(3.93	)		-28	%
Production, severance and ad valorem taxes		4.05			4.90		(0.85	)		-17	%
Processing, gathering and overhead		0.03			0.06		(0.03	)		-50	%
Total production expenses		13.97			18.78		(4.81	)		-26	%
Other:
Depletion, depreciation and amortization		21.11			20.48		0.63			3	%
General and administrative		3.75			8.01		(4.26	)		-53	%
Acquisition costs		0.34			9.87		(9.53	)		-97	%
Derivative fair value loss (gain)		(3.60	)		8.26		(11.86	)		-144	%
Accretion		0.19			0.36		(0.17	)		-47	%
Total operating		35.76			65.76		(30.00	)		-46	%
Interest		3.86			3.04		0.82			27	%
Income tax provision		0.75			0.49		0.26			53	%
Total expenses	$	40.37		$	69.29	$	(28.92	)		-42	%

        Production expenses.    Production expenses attributable to LOE increased $12.2 million from $13.3 million in 2011 to $25.5 million in 2012 as a result of an increase in production volumes from drilled wells and a full year of LOE from our Element acquisition, which contributed $22.3 million of additional LOE, partially offset by a $3.93 decrease in the average per BOE rate, which reduced LOE by $10.1 million. The decrease in our average LOE per BOE rate was attributable to wells we successfully drilled and completed in 2012 where we are experiencing economies of scale from our drilling program and from savings achieved through 2012 infrastructure projects that have resulted in material efficiencies in our field operations and, in particular, our disposal of water.

        Production expenses attributable to production, severance and ad valorem taxes increased $5.7 million from $4.7 million in 2011 to $10.4 million in 2012 primarily due to higher wellhead

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revenues, which exclude the effects of commodity derivative contracts, resulting from increased production from our acquisitions and drilling activity. As a percentage of wellhead revenues, production, severance and ad valorem taxes decreased to 6.6% in 2012 as compared to 7.2% in 2011 primarily due to an increase in oil revenues as a percentage of our total revenues, which are taxed at a lower rate than natural gas and NGLs, and because wells drilled in 2012 that contributed to our 2012 production will not have ad valorem taxes assessed until 2013.

        DD&A expense.    DD&A expense increased $34.7 million from $19.7 million in 2011 to $54.5 million in 2012 primarily due to a full year of production from the properties acquired in our Element acquisition and an increase in our asset base subject to amortization as a result of our 2012 drilling activity.

        G&A expense.    G&A expense increased $2.0 million from $7.7 million in 2011 to $9.7 million in 2012 primarily due to higher payroll and payroll-related costs as we added additional employees to manage our growing asset base.

        Acquisition costs.    Acquisition costs decreased $8.6 million from $9.5 million in 2011 to $0.9 million in 2012. We are party to a Transaction Fee Agreement, dated August 23, 2010, which requires us to pay a fee to Apollo equal to 2% of the total equity contributed to us, as defined in the agreement, in exchange for consulting and advisory services provided by Apollo. Upon the closing of the SandRidge acquisition in January 2011, we incurred a transaction fee payable to Apollo of $2.3 million. Upon the closing of the Element acquisition in October 2011, we incurred a transaction fee payable to Apollo of $4.3 million. In addition, we incurred other transaction costs associated with those significant acquisitions in 2011.

        Derivative fair value loss (gain).    During 2012, we recorded a $9.3 million derivative fair value gain as compared to an $8.0 million derivative fair value loss in 2011. The change in our derivative fair value loss (gain) was a result of additional oil swaps entered into during 2012 and the decrease in the future commodity price outlook during 2012, which favorably impacted the fair values of our commodity derivative contracts.

        Interest expense.    Interest expense increased $7.0 million from $2.9 million in 2011 to $9.9 million in 2012 primarily due to higher weighted-average outstanding borrowings under our credit agreement and the issuance of $125 million of debt under our former second lien term loan in September 2012. Our weighted-average outstanding borrowings under credit agreements were $196.5 million for 2012 as compared to $78.4 million for 2011. Our weighted-average interest rate for total indebtedness was 4.3% for 2012 as compared to 3.8% for 2011. Our weighted-average outstanding borrowings increased in 2012 in order to fund the closing of the Element acquisition in October 2011 and our higher level of development and exploration activities during 2012.

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        The following table provides the components of our interest expense for the periods indicated:

	Year ended December 31,
						Increase/ (Decrease)
	2012			2011
	(in thousands)
Credit agreements	$	5,932		$	2,387	$	3,545
Former second lien term loan		3,081			—		3,081
Other		1,155			545		610
Less: interest capitalized		(219	)		—		(219	)
Total	$	9,949		$	2,932	$	7,017

Capital Commitments, Capital Resources, and Liquidity

Capital commitments

        Our primary uses of cash are:

•

Development and exploration of oil and natural gas properties;

•

Acquisitions of oil and natural gas properties;

•

Funding of working capital; and

•

Contractual obligations.

        Development and exploration of oil and natural gas properties.    The following table summarizes our costs incurred related to development and exploration activities for the periods indicated:

	Three months ended March 31,				Year ended December 31,
	2013		2012		2012		2011
	(in thousands)
Development	$	49,238	$	24,370	$	201,174	$	71,403
Exploration		22,553		24,871		75,008		17,829
Total	$	71,791	$	49,241	$	276,182	$	89,232

        Our development capital primarily relates to drilling development and infill wells, workovers of existing wells and field related facilities. Our exploration expenditures primarily relate to drilling exploratory wells, seismic costs, delay rentals and geological and geophysical costs.

        Our development capital for the first quarter of 2013 yielded 19 gross (19 net) productive wells and no dry holes. Our exploration capital for the first quarter of 2013 yielded 16 gross (15 net) productive wells and no dry holes. The level of our development and exploration activities in the first quarter of 2013 were higher than in the first quarter of 2012 primarily due to our utilization of more efficient vertical drilling rigs that have significantly reduced the time from spud to rig release allowing us to drill more wells.

        Our development capital for 2012 yielded 102 gross (94 net) productive wells and two gross (two net) dry holes. Our exploration capital for 2012 yielded 29 gross (28 net) productive wells and no dry holes. The level of our development and exploration activities in 2012 were higher than in 2011 due to the increase in our operated drilling rigs from three to six upon the closing of the Element acquisition in October 2011.

        In 2013, we plan to invest approximately $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry

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wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells. Our 2013 development capital consists of:

•

$335 million of drilling and completion capital;

•

$5 million for infrastructure and other non-drilling capital projects as well as workovers of existing wells; and

•

$10 million for expanding our leasehold position.

        Acquisitions of oil and natural gas properties.    The following table summarizes our costs incurred related to oil and natural gas property acquisitions for the periods indicated:

	Year ended December 31,
	2012		2011
	(in thousands)
Acquisitions of proved properties	$	42,122	$	287,400
Acquisitions of unproved properties		38,908		130,273
Total	$	81,030	$	417,673

        We did not have any significant acquisitions during either the first quarter of 2013 or the first quarter of 2012.

        In the fourth quarter of 2012, we acquired certain oil and natural gas properties and related assets in the Permian Basin from three different sellers totaling for $74.9 million in cash.

        In January 2011, we acquired certain oil and natural gas properties and related assets in the Permian Basin from SandRidge for $156.0 million in cash. In October 2011, we acquired certain oil and natural gas properties and related assets in the Permian Basin from Element for $253.2 million in cash.

        Funding of working capital.    As of March 31, 2013 and December 31, 2012, our working capital deficit (defined as total current assets less total current liabilities) was $20.0 million and $22.2 million, respectively. Through 2013, we expect to continue to have working capital deficits primarily due to amounts accrued related to our extensive development activities. We expect our cash flows from operating activities and availability under our credit agreement after application of the estimated net proceeds from this offering, as described under "Use of Proceeds," will be sufficient to fund our working capital needs, capital expenditures and other obligations for at least the next 12 months. We expect that our production volumes, commodity prices and differentials to NYMEX prices for our oil and natural gas production will be the largest variables affecting our working capital.

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        Contractual obligations.    The following table provides our contractual obligations and commitments as of December 31, 2012:

	Payments Due by Period
Contractual Obligations and Commitments	Total		2013		2014 - 2015		2016 - 2017		Thereafter
	(in thousands)
Credit agreement1	$	265,370	$	6,468	$	12,936	$	245,966	$	—
Former second lien term loan1		170,848		9,375		18,750		142,723		—
Development commitments2		39,483		39,483		—		—		—
Operating leases and commitments3		1,787		471		938		378		—
Asset retirement obligations4		29,405		—		—		—		29,405
Total	$	506,893	$	55,797	$	32,624	$	389,067	$	29,405

¹

Includes principal and projected interest payments. Please read "—Liquidity" for additional information regarding our long-term debt.

²

Represents authorized purchases for work in process related to our drilling activities.

³

Represents operating leases that have non-cancelable lease terms in excess of one year.

⁴

Represents the undiscounted future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal at the end of field life. Because these costs typically extend many years into the future, estimating these future costs requires management to make estimates and judgments that are subject to future revisions based upon numerous factors.

        The above table does not reflect our April 2013 senior notes offering and the application of the net proceeds therefrom.

        As of December 31, 2012, the fair value of our commodity derivative contracts, the ultimate settlement of which are unknown because they are subject to continuing market risk, was a net asset of $4.0 million. Please read "—Quantitative and Qualitative Disclosures about Market Risk" for additional information regarding our commodity derivative contracts.

        Off-balance sheet arrangements.    We have no investments in unconsolidated entities or persons that could materially affect our liquidity or the availability of capital resources. We do not have any off-balance sheet arrangements that have, or are reasonably likely to have, an effect on our financial condition or results of operations.

Capital resources

        The following table summarizes our cash flows for the periods indicated:

	Three months ended March 31,						Year ended December 31,
	2013			2012			2012			2011
	(in thousands)
Net cash provided by operating activities	$	30,397		$	20,723		$	95,302		$	18,872
Net cash used in investing activities		(90,560	)		(58,498	)		(347,259	)		(465,475	)
Net cash provided by financing activities		54,671			12,982			228,798			471,627
Net increase (decrease) in cash	$	(5,492	)	$	(24,793	)	$	(23,159	)	$	25,024

        Cash flows from operating activities.    Cash provided by operating activities increased $9.7 million from $20.7 million in the first quarter of 2012 to $30.4 million in the first quarter of 2013, primarily due to an increase in our production margin due to a 91% increase in production as a result of wells

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drilled, partially offset by increased expenses as a result of having more producing wells in the first quarter of 2013 as compared to the first quarter of 2012.

        Cash provided by operating activities increased $76.4 million from $18.9 million in 2011 to $95.3 million in 2012, primarily due to an increase in our production margin as a result of a full year of production from our Element acquisition and wells drilled, partially offset by increased expenses as a result of our increased drilling activities in 2012 as compared to 2011.

        Cash flows used in investing activities.    Cash used in investing activities increased $32.1 million from $58.5 million in the first quarter of 2012 to $90.6 million in the first quarter of 2013, primarily due to a $24.5 million increase in amounts paid to develop oil and natural gas properties as we utilized more efficient vertical drilling rigs that have significantly reduced the time from spud to rig release allowing us to drill and complete more wells over the same time period.

        Cash used in investing activities decreased $118.2 million from $465.5 million in 2011 to $347.3 million in 2012, primarily due to a $334.2 million decrease in amounts paid to acquire oil and natural gas properties, which in 2011 included our SandRidge and Element acquisitions, partially offset by a $208.8 million increase in amounts paid to develop oil and natural gas properties as we utilized at least six rigs for the majority of 2012. In January 2011, we terminated certain oil puts that were in place at December 31, 2010 and received net proceeds of $7.6 million, which are included in cash used in investing activities for 2011.

        Cash flows from financing activities.    Our cash flows from financing activities consist primarily of net proceeds from and payments on long-term debt and contributions from partners. We periodically draw on our credit agreement and seek funding from partners to fund acquisitions and other capital commitments.

        During the first quarter of 2013, we received net cash of $54.7 million from financing activities, including net borrowings of $54.4 million under our credit agreement, which were used primarily to finance the first quarter of 2013 development activities. Net borrowings increased the outstanding borrowings under our credit agreement from $237 million at December 31, 2012 to $291.4 million at March 31, 2013.

        During the first quarter of 2012, we received net cash of $13.0 million from financing activities, consisting primarily of net borrowings under our credit agreement.

        During 2012, we received net cash of $228.8 million from financing activities, including $122.9 million of net proceeds from the issuance of our former second lien term loan, which were used to replace outstanding borrowings under our credit agreement, net borrowings of $67 million under our credit agreement and $40.2 million of partner contributions, which were used primarily to finance 2012 acquisitions. Net borrowings increased the outstanding borrowings under our credit agreements from $170 million at December 31, 2011 to $237 million at December 31, 2012.

        During 2011, we received net cash of $471.6 million from financing activities, including net borrowings of $170 million under our credit agreement and $304.0 million of partner contributions.

Liquidity

        Our primary sources of liquidity historically have been internally generated cash flows, the borrowing capacity under our credit agreement and partner contributions, including from our equity sponsor, the Apollo Funds. Since we operate a majority of our wells, we also have the ability to adjust our capital expenditures. We may use other sources of capital, including the issuance of debt or equity securities, to fund acquisitions or maintain our financial flexibility. We believe that our internally generated cash flows and expected future availability under our credit agreement after giving effect to the issuance of the securities offered hereby and the application of the estimated net proceeds from

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this offering as described under "Use of Proceeds" will be sufficient to fund our operations and planned capital expenditures for at least the next 12 months. However, should commodity prices decline for an extended period of time or the capital/credit markets become constrained, the borrowing capacity under our credit agreement could be adversely affected. In the event of a reduction in the borrowing base under our credit agreement, we may be required to prepay some or all of our indebtedness, which would adversely affect our capital expenditure program. In addition, because wells funded in the next 12 months represent only a small percentage of our identified net drilling locations, we will be required to generate or raise multiples of this amount of capital to develop our entire inventory of identified drilling locations should we elect to do so.

        In 2013, we plan to invest approximately $350 million of development capital. The level of these and other future expenditures is largely discretionary, and the amount of funds devoted to any particular activity may increase or decrease significantly, depending on available opportunities, timing of projects and market conditions. We plan to finance our ongoing expenditures using internally generated cash flow and availability under our credit agreement.

        Internally generated cash flows.    Our internally generated cash flows, results of operations and financing for our operations are largely dependent on oil, natural gas and NGLs prices. During the first quarter of 2013, our average realized oil and NGLs prices decreased by 15% and 26%, respectively, as compared to the first quarter of 2012, while our average realized natural gas price increased by 21%. During 2012, our average realized oil, natural gas and NGLs prices decreased by 5%, 23% and 25%, respectively, as compared to 2011. Realized commodity prices fluctuate widely in response to changing market forces. If commodity prices decline or we experience a significant widening of our differentials to NYMEX prices, then our results of operations, cash flows from operations and borrowing base under our credit agreement may be adversely impacted. Prolonged periods of lower commodity prices or sustained wider differentials to NYMEX prices could cause us to not be in compliance with financial covenants under our credit agreement and thereby affect our liquidity. To offset reduced cash flows in a lower commodity price environment, we have established a portfolio of commodity derivative contracts consisting primarily of oil swaps that will provide stable cash flows on a portion of our oil production. As of March 31, 2013, our hedged oil volumes for 2013, 2014 and 2015 represent 99%, 96% and 21%, respectively, of our March 2013 oil production at weighted average prices of $94.18, $92.76 and $93.18, respectively. An increase in oil prices above the ceiling prices in our commodity derivative contracts limits cash inflows because we would be required to pay our counterparties for the difference between the market price for oil and the ceiling price of the commodity derivative contract resulting in a loss. Please read "—Quantitative and Qualitative Disclosures About Market Risk" for additional information regarding our commodity derivative contracts.

        Credit agreement.    We are a party to an amended and restated credit agreement dated March 19, 2013, which we refer to as our credit agreement, which matures on March 19, 2018. Our credit agreement provides for revolving credit loans to be made to us from time to time and letters of credit to be issued from time to time for the account of us or any of our restricted subsidiaries. The aggregate amount of the commitments of the lenders under our credit agreement is $1.0 billion. Availability under our credit agreement is subject to a borrowing base, which is redetermined semi-annually and upon requested special redeterminations.

        As of March 31, 2013, the borrowing base was $360 million and there were $291.4 million of outstanding borrowings, $68.6 million of borrowing capacity and no outstanding letters of credit under our credit agreement. In conjunction with the offering of our senior notes in April 2013 as discussed below, the borrowing base under our credit agreement was reduced to $267.5 million. We used a portion of the net proceeds from the offering of the senior notes to reduce the outstanding borrowings under our credit agreement. In May 2013, we amended our credit agreement to, among other things, increase the borrowing base to $320 million. As of July 22, 2013, there were $72 million of outstanding borrowings under our credit agreement.

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        Obligations under our credit agreement are secured by a first-priority security interest in substantially all of our proved reserves and in the equity interests of our operating subsidiaries. In addition, obligations under our credit agreement are guaranteed by our operating subsidiaries.

        Loans under our credit agreement are subject to varying rates of interest based on (1) outstanding borrowings in relation to the borrowing base and (2) whether the loan is a Eurodollar loan or a base rate loan. Eurodollar loans under our credit agreement bear interest at the Eurodollar rate plus the applicable margin indicated in the following table, and base rate loans under our credit agreement bear interest at the base rate plus the applicable margin indicated in the following table. We also incur a quarterly commitment fee on the unused portion of our credit agreement indicated in the following table:

Ratio of Outstanding Borrowings to Borrowing Base	Unused Commitment Fee			Applicable Margin for Eurodollar Loans			Applicable Margin for Base Rate Loans
Less than or equal to .30 to 1		0.375	%		0.50	%		1.50	%
Greater than .30 to 1 but less than or equal to .60 to 1		0.375	%		0.75	%		1.75	%
Greater than .60 to 1 but less than or equal to .80 to 1		0.50	%		1.00	%		2.00	%
Greater than .80 to 1 but less than or equal to .90 to 1		0.50	%		1.25	%		2.25	%
Greater than .90 to 1		0.50	%		1.50	%		2.50	%

        The "Eurodollar rate" for any interest period (either one, two, three or six months, as selected by us) is the rate equal to the LIBOR for deposits in dollars for a similar interest period. The "Base Rate" is calculated as the highest of: (1) the annual rate of interest announced by Bank of America, N.A. as its "prime rate"; (2) the federal funds effective rate plus 0.5%; or (3) except during a "LIBOR Unavailability Period," the Eurodollar rate (for dollar deposits for a one-month term) for such day plus 1.0%.

        Any outstanding letters of credit reduce the availability under our credit agreement. Borrowings under our credit agreement may be repaid from time to time without penalty.

        Our credit agreement contains customary covenants including, among others, the following:

•

a prohibition against incurring debt, subject to permitted exceptions;

•

a restriction on creating liens on our assets and the assets of our operating subsidiaries, subject to permitted exceptions;

•

restrictions on merging and selling assets outside the ordinary course of business;

•

restrictions on use of proceeds, investments, transactions with affiliates or change of principal business;

•

a requirement that we maintain a ratio of consolidated total debt to EBITDAX (as defined in our credit agreement and as presented under "Summary Consolidated Financial, Reserve and Operating Data—Non-GAAP Financial Measures—Adjusted EBITDA") of not more than 4.75 to 1.0 (which ratio changes to 4.5 to 1.0 beginning with the quarter ended June 30, 2014); and

•

a provision limiting commodity derivative contracts to a volume not exceeding 85% of projected production from proved reserves for a period not exceeding 66 months from the date the commodity derivative contract is entered into.

        Our credit agreement contains customary events of default, including our failure to comply with our financial ratios described above, which would permit the lenders to accelerate the debt if not cured within applicable grace periods. If an event of default occurs and is continuing, lenders with a majority of the aggregate commitments may require Bank of America, N.A. to declare all amounts outstanding

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under our credit agreement to be immediately due and payable, which would materially and adversely affect our financial condition and liquidity.

        Certain of the lenders underwriting our credit agreement are also counterparties to our commodity derivative contracts. Please read "—Quantitative and Qualitative Disclosures About Market Risk" for additional discussion.

        We expect to reduce outstanding borrowings under our credit agreement with a portion of the net proceeds from this offering.

        Senior notes.    In April 2013, we issued $500 million aggregate principal amount of 7³/8% senior notes due 2021. The net proceeds from the senior notes offering were used to repay a portion of the outstanding borrowings under our credit agreement, to repay in full and terminate our former second lien term loan, to make a $75 million distribution to Class A limited partners of Athlon Holdings LP and for general corporate purposes. The indenture governing the senior notes contains covenants, including, among other things, covenants that restrict our ability to:

•

make distributions, investments or other restricted payments if our fixed charge coverage ratio is less than 2.0 to 1.0;

•

incur additional indebtedness if our fixed charge coverage ratio would be less than 2.0 to 1.0; and

•

create liens, sell assets, consolidate or merge with any other person or engage in transactions with affiliates.

These covenants are subject to a number of important qualifications, limitations and exceptions. In addition, the indenture contains other customary terms, including certain events of default upon the occurrence of which the senior notes may be declared immediately due and payable.

        Under the indenture, starting on April 15, 2016, we will be able to redeem some or all of the senior notes at a premium that will decrease over time, plus accrued and unpaid interest to the date of redemption. Prior to April 15, 2016, we will be able, at our option, to redeem up to 35% of the aggregate principal amount of the senior notes at a price of 107.375% of the principal thereof, plus accrued and unpaid interest to the date of redemption, with an amount equal to the net proceeds from certain equity offerings. In addition, at our option, prior to April 15, 2016, we may redeem some or all of the senior notes at a redemption price equal to 100% of the principal amount of the senior notes, plus an "applicable premium," plus accrued and unpaid interest to the date of redemption. If a change of control occurs on or prior to July 15, 2014, we may redeem all, but not less than all, of the notes at 110% of the principal amount thereof plus accrued and unpaid interest to, but not including, the redemption date. Certain asset dispositions will be triggering events that may require us to repurchase all or any part of a noteholder's notes at a purchase price in cash equal to 101% of the principal amount thereof, plus accrued and unpaid interest, if any, to but excluding the date of repurchase. Interest on the senior notes is payable in cash semi-annually in arrears, commencing on October 15, 2013, through maturity.

        Capitalization.    At March 31, 2013, we had total assets of $916.5 million and total capitalization of $849.8 million, of which 51% was represented by equity and 49% by long-term debt. At December 31, 2012, we had total assets of $852.3 million and total capitalization of $782.9 million, of which 54% was represented by equity and 46% by long-term debt. The percentages of our capitalization represented by equity and long-term debt could vary in the future if debt or equity is used to finance capital projects or acquisitions.

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Changes in Prices

        Our revenues, the value of our assets and our ability to obtain bank loans or additional capital on attractive terms are affected by changes in commodity prices, which can fluctuate significantly. The following table provides our average realized prices for the periods indicated:

	Three months ended March 31,				Year ended December 31,
	2013		2012		2012		2011
Average realized prices:
Oil ($/Bbl) (excluding impact of cash settled derivatives)	$	84.23	$	99.29	$	87.90	$	92.08
Oil ($/Bbl) (after impact of cash settled derivatives)		83.65		89.53		87.16		87.16
Natural gas ($/Mcf)		3.27		2.71		2.66		3.46
NGLs ($/Bbl)		31.34		42.48		34.65		45.96
Combined ($/BOE) (excluding impact of cash settled derivatives)		61.08		71.05		60.91		68.13
Combined ($/BOE) (after impact of cash settled derivatives)		60.73		65.28		60.50		65.29

        Increases in commodity prices may be accompanied by or result in: (1) increased development costs, as the demand for drilling operations increases; (2) increased severance taxes, as we are subject to higher severance taxes due to the increased value of hydrocarbons extracted from our wells; and (3) increased LOE, such as electricity costs, as the demand for services related to the operation of our wells increases. Decreases in commodity prices can have the opposite impact of those listed above and can result in an impairment charge to our oil and natural gas properties.

Critical Accounting Policies and Estimates

        Preparing financial statements in accordance with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses and related disclosures. Estimates and assumptions are based on information available prior to financial statements being issued. Due to the nature of these estimates, new facts or circumstances may arise resulting in revised estimates which differ from these estimates. Management considers an accounting estimate to be critical if it requires assumptions that have a high degree of subjectivity and judgment to account for outcomes that are highly uncertain and the impact of these estimates and assumptions is material to our consolidated results of operations or financial condition. Management has identified the following critical accounting policies and estimates.

Oil and Natural Gas Reserves

        Our estimates of proved reserves are based on the quantities of oil and natural gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible from a given date forward from known reservoirs under existing economic conditions and operating methods. Our independent petroleum engineers, CG&A, prepare a reserve and economic evaluation of all of our properties on a well-by-well basis. The accuracy of reserve estimates is a function of the:

•

quality and quantity of available data;

•

interpretation of that data;

•

accuracy of various mandated economic assumptions; and

•

judgment of the independent reserve engineer.

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        Estimating reserves is subjective and actual quantities of oil and natural gas ultimately recovered can differ from estimates for many reasons. Future prices received for production and future production costs may vary, perhaps significantly, from the prices and costs assumed for purposes of calculating reserve estimates. We may not be able to develop proved reserves within the periods estimated. Actual production may not equal the estimated amounts used in the preparation of reserve projections. As these estimates change, calculated reserves change. Any change in reserves directly impacts our estimate of future cash flows from the property, the property's fair value and our DD&A rate.

        Our independent petroleum engineers, CG&A, estimate our proved reserves annually on December 31. This results in a new DD&A rate which we use for the preceding fourth quarter after adjusting for fourth quarter production. We internally estimate reserve additions and reclassifications of reserves from unproved to proved at the end of the first, second and third quarters for use in determining a DD&A rate for the respective quarter.

Method of Accounting for Oil and Natural Gas Properties

        We apply the provisions of the "Extractive Activities—Oil and Gas" topic of the Financial Accounting Standards Board's ("FASB") Accounting Standards Codification ("ASC"). We use the full cost method of accounting for our oil and natural gas properties. Under this method, costs directly associated with the acquisition, exploration and development of reserves are capitalized into a full cost pool. Capitalized costs are amortized using a unit-of-production method. Under this method, the provision for DD&A is computed at the end of each period by multiplying total production for the period by a depletion rate. The depletion rate is determined by dividing the total unamortized cost base plus future development costs by net equivalent proved reserves at the beginning of the period.

        Costs associated with unproved properties are excluded from the amortizable cost base until a determination has been made as to the existence of proved reserves. Unproved properties are reviewed at the end of each quarter to determine whether the costs incurred should be reclassified to the full cost pool and, thereby, subjected to amortization. The costs associated with unproved properties primarily consist of acquisition and leasehold costs as well as development costs for wells in progress for which a determination of the existence of proved reserves has not been made. These costs are transferred to the amortization base once a determination is made whether or not proved reserves can be assigned to the property, upon impairment of a lease or immediately upon determination that the well is unsuccessful. Costs of seismic data that cannot be directly associated to specific unproved properties are included in the full cost pool as incurred, otherwise, they are allocated to various unproved leaseholds and transferred to the amortization base with the associated leasehold costs on a specific project basis.

        Sales and abandonments of oil and natural gas properties being amortized are accounted for as adjustments to the full cost pool, with no gain or loss recognized, unless the adjustments would significantly alter the relationship between capitalized costs and proved reserves. A significant alteration would not ordinarily be expected to occur upon the sale of reserves involving less than 25% of the reserve quantities of a cost center.

        Natural gas volumes are converted to BOE at the rate of six Mcf of natural gas to one Bbl of oil. This convention is not an equivalent price basis and there may be a large difference in value between an equivalent volume of oil versus an equivalent volume of natural gas.

        We capitalize interest on expenditures made in connection with exploration and development projects that are not subject to current amortization. Interest is capitalized only for the period that activities are in progress to bring these projects to their intended use. Capitalized interest cannot exceed gross interest expense.

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Impairment

        Unevaluated properties are assessed periodically, at least annually, for possible impairment. Properties are assessed on an individual basis or as a group if properties are individually insignificant. The assessment includes consideration of various factors, including, but not limited to: intent to drill, remaining lease term, geological and geophysical evaluations, drilling results and economic viability of development if proved reserves are assigned. During any period in which these factors indicate impairment, the cumulative drilling costs incurred to date for such property and all or a portion of the associated leasehold costs are transferred to the full cost pool and become subject to amortization.

        Under the full cost method of accounting, total capitalized costs of oil and natural gas properties, net of accumulated DD&A, less related deferred income taxes may not exceed an amount equal to PV-10 plus the lower of cost or fair value of unevaluated properties, plus estimated salvage value, less the related tax effects (the "ceiling limitation"). A ceiling limitation is calculated at the end of each quarter. If total capitalized costs, net of accumulated DD&A, less related deferred income taxes are greater than the ceiling limitation, a write-down or impairment of the full cost pool is required. A write-down of the carrying value of the full cost pool is a non-cash charge that reduces earnings and impacts equity in the period of occurrence and typically results in lower DD&A expense in future periods. Once incurred, a write-down cannot be reversed at a later date.

        The ceiling limitation calculation is prepared using the 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves ("net wellhead prices"). If applicable, these net wellhead prices would be further adjusted to include the effects of any fixed price arrangements for the sale of oil and natural gas. We use commodity derivative contracts to mitigate the risk against the volatility of oil and natural gas prices. Commodity derivative contracts that qualify and are designated as cash flow hedges are included in estimated future cash flows. We have not designated any of our commodity derivative contracts as cash flow hedges and therefore have excluded commodity derivative contracts in estimating future cash flows. The future cash outflows associated with future development or abandonment of wells are included in the computation of the discounted present value of future net revenues for purposes of the ceiling limitation calculation.

Asset Retirement Obligations

        We apply the provisions of the "Asset Retirement and Environmental Obligations" topic of the ASC. We have obligations as a result of lease agreements and enacted laws to remove our equipment and restore land at the end of production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and land remediation. At the time a well is drilled or acquired, we record a separate liability for the estimated fair value of our asset retirement obligations, with an offsetting increase to the related oil and natural gas asset representing asset retirement costs. The cost of the related oil and natural gas asset, including the asset retirement cost, is included in our full cost pool. The estimated fair value of an asset retirement obligation is the present value of the expected future cash outflows required to satisfy the asset retirement obligations discounted at our credit-adjusted, risk-free interest rate at the time the liability is incurred. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.

        Inherent to the present-value calculation are numerous estimates, assumptions and judgments, including, but not limited to: the ultimate settlement amounts, inflation factors, credit-adjusted risk-free rates, timing of settlement and changes in the legal, regulatory, environmental and political environments. To the extent future revisions to these assumptions affect the present value of the abandonment liability, we make corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. These revisions result in prospective changes to DD&A expense and accretion of the discounted abandonment liability.

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Revenue Recognition

        Revenues from the sale of oil, natural gas and NGLs are recognized when they are realized or realizable and earned. Revenues are considered realized or realizable and earned when: (i) persuasive evidence of an arrangement exists; (ii) delivery has occurred or services have been rendered; (iii) the seller's price to the buyer is fixed or determinable; and (iv) collectability is reasonably assured. Because final settlement of our hydrocarbon sales can take up to two months, the estimated sales volumes and prices are estimated and accrued using information available at the time the revenue is recorded.

Derivatives

        We use various financial instruments for non-trading purposes to manage and reduce price volatility and other market risks associated with our oil production. These arrangements are structured to reduce our exposure to commodity price decreases, but they can also limit the benefit we might otherwise receive from commodity price increases. Our risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions.

        We apply the provisions of the "Derivatives and Hedging" topic of the ASC, which requires each derivative instrument to be recorded at fair value. If a derivative has not been designated as a hedge or does not otherwise qualify for hedge accounting, it must be adjusted to fair value through earnings. We elected not to designate our current portfolio of commodity derivative contracts as hedges. Therefore, changes in fair value of these derivative instruments are recognized in earnings.

        We enter into commodity derivative contracts for the purpose of economically hedging the price of our anticipated oil production even though we do not designate the derivatives as hedges for accounting purposes. We classify cash flows related to derivative contracts based on the nature and purpose of the derivative. As the derivative cash flows are considered an integral part of our oil and natural gas operations, they are classified as cash flows from operating activities in the consolidated statements of cash flows. During 2011 and 2012, we entered into commodity derivative contracts all of which were for the purpose of economically hedging our anticipated oil production.

        Cash flows relating to commodity derivative contracts that were entered into prior to us commencing oil and natural gas operations in January 2011 are classified as investing activities in the consolidated statements of cash flows.

        As required by GAAP, we utilize the most observable inputs available for the valuation technique used. The financial assets and liabilities are classified in their entirety based on the lowest level of input that is of significance to the fair value measurement. Our assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the financial assets and liabilities. Fair values of swaps are estimated using a combined income-based and market-based valuation methodology based upon forward commodity price curves obtained from independent pricing services. Our collars and puts are average value options. Settlement is determined by the average underlying price over a predetermined period of time. We use observable inputs in an option pricing valuation model to determine fair value such as: (1) current market and contractual prices for the underlying instruments; (2) quoted forward prices for oil and natural gas; (3) interest rates, such as a LIBOR curve for a term similar to the commodity derivative contract; and (4) appropriate volatilities.

        We adjust the valuations from the valuation model for nonperformance risk. For commodity derivative contracts which are in an asset position, we use the counterparty's credit default swap rating. For commodity derivative contracts which are in a liability position, we use the average credit default swap rating of our peer companies with similar credit profiles as currently we do not have our own credit default swap rating.

New Accounting Pronouncements

        In December 2011, the FASB issued ASU 2011-11, "Disclosures about Offsetting Assets and Liabilities" and in January 2013 issued ASU 2013-01, "Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities." These ASUs created new disclosure requirements regarding the nature

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of an entity's rights of setoff and related arrangements associated with its derivative instruments, repurchase agreements and securities lending transactions. Certain disclosures of the amounts of certain instruments subject to enforceable master netting arrangements are required, irrespective of whether the entity has elected to offset those instruments in the balance sheet. These ASUs were effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of these ASUs did not impact our financial condition, results of operations or liquidity.

Emerging Growth Company

        The JOBS Act permits an "emerging growth company" like us to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies. We have elected to "opt out" of this provision and, as a result, we will comply with new or revised accounting standards as required when they are adopted. This decision to opt out of the extended transition period is irrevocable.

Quantitative and Qualitative Disclosures About Market Risk

        The primary objective of the following information is to provide quantitative and qualitative information about our potential exposure to market risks. The term "market risk" refers to the risk of loss arising from adverse changes in oil and natural gas prices and interest rates. The disclosures are not meant to be precise indicators of exposure, but rather indicators of potential exposure. This information provides indicators of how we view and manage our ongoing market risk exposures. We do not enter into market risk sensitive instruments for speculative trading purposes.

Derivative policy

        Due to the volatility of commodity prices, we enter into various derivative instruments to manage and reduce our exposure to price changes. We primarily utilize WTI crude oil swaps that establish a fixed price for the production covered by the swaps. We also have employed WTI crude oil options (including puts and collars) to further mitigate our commodity price risk. All contracts are settled with cash and do not require the delivery of physical volumes to satisfy settlement. While this strategy may result in lower net cash inflows in times of higher oil prices than we would otherwise have, had we not utilized these instruments, management believes that the resulting reduced volatility of cash flow resulting from use of derivatives is beneficial.

Counterparties

        At March 31, 2013, we had committed 10% or greater (in terms of fair market value) of our oil derivative contracts in asset positions to the following counterparties:

Counterparty	Fair Market Value of Oil Derivative Contracts Committed
	(in thousands)
BNP Paribas	$	1,824

        We do not require collateral from our counterparties for entering into financial instruments, so in order to mitigate the credit risk of financial instruments, we enter into master netting agreements with certain counterparties. The master netting agreement is a standardized, bilateral contract between a given counterparty and us. Instead of treating each financial transaction between the counterparty and us separately, the master netting agreement enables the counterparty and us to aggregate all financial trades and treat them as a single agreement. This arrangement is intended to benefit us in two ways: (1) default by a counterparty under one financial trade can trigger rights to terminate all financial trades with such counterparty; and (2) netting of settlement amounts reduces our credit exposure to a given counterparty in the event of close-out.

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        The counterparties to our commodity derivative contracts are composed of six institutions, all of which are rated A- or better by Standard & Poor's and Baa2 or better by Moody's and five of which are lenders under our credit agreement.

Commodity price sensitivity

        Commodity prices are often subject to significant volatility due to many factors that are beyond our control, including but not limited to: prevailing economic conditions, supply and demand of hydrocarbons in the marketplace, actions by speculators and geopolitical events such as wars or natural disasters. We manage oil price risk with swaps, puts and collars. Swaps provide a fixed price for a notional amount of sales volumes. Puts provide a fixed floor price on a notional amount of sales volumes while allowing full price participation if the relevant index price closes above the floor price. Collars provide a floor price on a notional amount of sales volumes while allowing some additional price participation if the relevant index price closes above the floor price. This participation is limited by a ceiling price specified in the contract.

        The following table summarizes our open commodity derivative contracts as of March 31, 2013:

Period	Average Daily Floor Volume		Weighted- Average Floor Price		Average Daily Cap Volume		Weighted- Average Cap Price		Average Daily Swap Volume		Weighted- Average Swap Price		Asset (Liability) Fair Market Value
	(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(in thousands)
2013		150	$	75.00		150	$	105.95		6,000	$	94.66	$	(3,474	)
2014		—		—		—		—		5,950		92.76		130
2015		—		—		—		—		1,300		93.18		1,782
													$	(1,562	)

        We are also a party to Midland-Cushing basis differential swaps for 5,000 Bbls/D at $1.20/Bbl for April through December 2013. At March 31, 2013, the fair value of these contracts was a liability of approximately $1.2 million.

        As stated above under "—Critical Accounting Policies and Estimates—Derivatives," we elected not to designate our derivative contracts as hedges and therefore changes in fair value of these instruments are recognized in earnings. As of March 31, 2013, the fair market value of our oil derivative contracts was a net liability of $2.7 million. Based on our open commodity derivative positions at March 31, 2013, a 10% increase in NYMEX prices for oil would increase our net commodity derivative liability by approximately $12.5 million, while a 10% decrease in NYMEX prices for oil would change our net commodity derivative liability to a net commodity derivative asset of approximately $10.1 million.

Interest rate sensitivity

        At March 31, 2013, we had outstanding debt of $416.4 million, all of which is subject to floating market rates of interest that are linked to the Eurodollar rate. At this level of floating rate debt, if the Eurodollar rate increased 10%, we would incur an additional $1.7 million of interest expense per year, and if the Eurodollar rate decreased 10%, we would incur $1.7 million less.

Internal Controls and Procedures

        We are not currently required to comply with the SEC's rules implementing Section 404 of the Sarbanes Oxley Act, and are therefore not required to make a formal assessment of the effectiveness of our internal control over financial reporting for that purpose. Upon becoming a public company, we will be required to comply with the SEC's rules implementing Section 302 of the Sarbanes-Oxley Act, which will require our management to certify financial and other information in our quarterly and annual reports and provide an annual management report on the effectiveness of our internal control over financial reporting. We will not be required to make our first assessment of our internal control over financial reporting under Section 404 until the year following our first annual report required to be filed with the SEC.

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BUSINESS

General

        We are an independent exploration and production company focused on the acquisition, development and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. The Permian Basin spans portions of Texas and New Mexico and is composed of three primary sub-basins: the Delaware Basin, the Central Basin Platform and the Midland Basin. All of our properties are located in the Midland Basin. Our drilling activity is currently focused on the low-risk vertical development of stacked pay zones, including the Spraberry, Wolfcamp, Cline, Strawn, Atoka and Mississippian formations, which we refer to collectively as the Wolfberry play. We are a returns-focused organization and have targeted the Wolfberry play in the Midland Basin because of its favorable operating environment, consistent reservoir quality across multiple target horizons, long-lived reserve characteristics and high drilling success rates.

        We were founded in August 2010 by a group of former executives from Encore Acquisition Company following its acquisition by Denbury Resources, Inc. With an average of approximately 20 years of industry experience and over 10 years of history working together, our founding management has a proven track record of working as a team to acquire, develop and exploit oil and natural gas reserves in the Permian Basin as well as other resource plays in North America.

        Our acreage position was 124,925 gross (98,348 net) acres at May 31, 2013, which we group into three primary areas based on geographic location within the Midland Basin: Howard, Midland & Other and Glasscock. From the time we began operations in January 2011 through May 31, 2013, we have operated up to eight vertical drilling rigs simultaneously and have drilled 230 gross vertical Wolfberry wells with a 99% success rate across all three areas. This activity has allowed us to identify and de-risk our multi-year inventory of 4,902 gross (3,857 net) vertical drilling locations, while also identifying 1,079 gross (931 net) horizontal drilling locations in specific areas based on geophysical and technical data. As we continue to expand our vertical drilling activity to our undeveloped acreage, we expect to identify additional horizontal drilling locations.

        The following table summarizes our leasehold position and identified net drilling locations by primary geographic area as of May 31, 2013:

					Identified Drilling Locations1
					Vertical
	Acreage
					Net 40-acre2		Net 20-acre		Net Total		Drilling Inventory3 (years)		Net Horizontal4
	Gross		Net
Howard		69,661		51,556		1,140		1,291		2,431		37		403
Midland & Other		36,694		33,709		390		414		804		20		316
Glasscock		18,570		13,083		267		355		622		24		212
Total		124,925		98,348		1,797		2,060		3,857		30		931

¹

Represents locations specifically identified by management based on evaluation of applicable geologic, engineering and production data. The drilling locations on which we actually drill wells will ultimately depend on the availability of capital, regulatory approvals, oil and natural gas prices, costs, actual drilling results and other factors.

²

Includes 597 gross (560 net) locations booked as proved undeveloped locations in our proved reserve report as of December 31, 2012.

³

Based on our 2013 drilling program on a gross basis.

⁴

Includes horizontal drilling locations targeting Wolfcamp A, Wolfcamp B, Wolfcamp C, Cline and Mississippian intervals, which comprise 311 gross (272 net), 357 gross (317 net), 133 gross (125 net), 227 gross (193 net) and 51 gross (24 net) locations, respectively.

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        Since our inception, we have completed two significant acquisitions and seven bolt-on acquisitions. At the time of each acquisition, based on internal engineering estimates, these properties collectively contributed approximately 3,600 BOE/D of production and approximately 43 MMBOE of proved reserves. We have significantly grown production and proved reserves on the properties we acquired through the successful execution of our low-risk vertical drilling program. From the time we began operations in January 2011 through May 31, 2013, we have drilled 230 gross vertical Wolfberry wells on our properties with a 99% success rate and grown our production to 11,957 BOE/D for June 2013.

        In 2012, our development capital was approximately $276 million and we drilled a total of 133 gross (124 net) vertical Wolfberry wells. In 2013, we plan to invest $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells. We currently operate seven vertical drilling rigs on our properties and have operated between five and eight vertical drilling rigs since October 2011. We expect to take delivery of our first horizontal rig in the third quarter of 2013 and our second horizontal rig in the second quarter of 2014.

        Our estimate of proved reserves is prepared by CG&A, our independent petroleum engineers. As of December 31, 2012, we had 86 MMBOE of proved reserves, which were 58% oil, 22% NGLs and 20% natural gas and 30% proved developed. As of December 31, 2012, the PV-10 of our proved reserves was approximately $867 million, 59% of which was attributed to proved developed reserves. Our proved undeveloped reserves, or PUDs, are composed of 597 gross (560 net) potential vertical drilling locations. The following table provides information regarding our proved reserves and production by area as of December 31, 2012, except as otherwise noted below:

	Estimated Total Proved Reserves
														Average Net Daily Production3 (BOE/D)
	Oil (MMBbls)		NGLs (MMBbls)		Natural Gas (Bcf)		Total (MMBOE)		% Liquids1			PV-102 (in millions)				R/P Ratio (years)
Howard		20.2		7.3		36.3		33.5		82	%	$	365.4		4,392		20.9
Midland & Other		17.6		8.3		44.7		33.3		78	%		337.0		5,702		16.0
Glasscock		11.6		3.7		22.7		19.2		80	%		164.2		1,863		28.2
Total		49.4		19.3		103.7		86.0		80	%	$	866.6		11,957		19.7

¹

Includes both oil and NGLs.

²

PV-10 is a non-GAAP financial measure. Standarized Measure is the closest GAAP measure and our Standarized Measure was $850.9 million at December 31, 2012. For additional information about PV-10 and how it differs from the Standardized Measure, please read "Summary Consolidated Financial, Reserve and Operating Data—Non-GAAP Financial Measures."

³

During June 2013, inclusive of oil production of 6,895 Bbls/D in total.

Our Business Strategy

        We maintain a disciplined and analytical approach to investing in which we seek to direct capital in a manner that will maximize our rates of return as we develop our extensive resource base. Key elements of our strategy are:

•

Grow reserves, production and cash flow with our multi-year inventory of low-risk vertical drilling locations.  We have considerable experience managing large scale drilling programs and intend to efficiently develop our acreage position to maximize the value of our resource base. During 2012, we invested $276 million of development capital, drilled 133 gross (124 net) vertical Wolfberry wells and grew production by 4,204 BOE/D, or 93%, from 4,506 BOE/D in the fourth quarter of 2011 to 8,710 BOE/D in the fourth quarter of 2012. We also increased proved reserves by 40 MMBOE, or 86%, from 46 MMBOE at December 31, 2011 to 86 MMBOE at December 31, 2012. In 2013, we plan to invest approximately $317 million of development

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capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells in order to continue to grow our production and reserves.

•

Continuously improve capital and operating efficiency.  We continuously focus on optimizing the development of our resource base by seeking ways to maximize our recovery per well relative to the cost incurred and to minimize our operating cost per BOE produced. We apply an analytical approach to track and monitor the effectiveness of our drilling and completion techniques and service providers. Additionally, we seek to build infrastructure that allows us to achieve economies of scale and reduce operating costs. Specifically, we have:

•

achieved first six-month average daily production volumes on our operated wells in Howard County of 85 BOE/D, which represents outperformance by 102% of average industry vertical well results since 2010 of 42 BOE/D in Howard County, based on data from the Texas Railroad Commission;

•

achieved first six-month average daily production volumes on our operated wells in Midland County of 106 BOE/D, which represents outperformance by 68% of average industry vertical well results since 2010 of 63 BOE/D in Midland County, based on data from the Texas Railroad Commission;

•

reduced average development costs per gross well in our Midland & Other area from $2.4 million in the first quarter of 2012 to $2.1 million in the first quarter of 2013, an improvement of 9%;

•

reduced average development costs per gross well in our Howard and Glasscock areas from $2.0 million in the first quarter of 2012 to $1.8 million in the first quarter of 2013, an improvement of 12%;

•

reduced the time from spud to rig release in our Howard and Glasscock areas from 16 days in the fourth quarter of 2011 to 8 days in the first quarter of 2013, an improvement of 50%; and

•

reduced LOE from $13.82 per BOE for 2011 to $9.89 per BOE for 2012, an improvement of 28%.

•

Balance capital allocation between our lower risk vertical drilling program and horizontal development opportunities.  We have historically focused on optimizing our vertical drilling and completion techniques across our acreage position. Vertical drilling involves less operational, financial and other risk than horizontal drilling, and we view our extensive delineation vertical development drilling program as "low risk" because the drilling locations were selected based on our drilling and production history in the area and well-established industry activity surrounding our acreage. Many operators in the Midland Basin are actively drilling horizontal wells, which is more expensive than drilling vertical Wolfberry wells but potentially recovers disproportionately more hydrocarbons per well. We monitor industry horizontal drilling activity and intend to utilize the knowledge gained from the increase in industry horizontal drilling in the Midland Basin. In the second half of 2013, we intend to supplement our vertical drilling with horizontal drilling in circumstances where we believe that horizontal drilling should offer competitive rates of return.

•

Evaluate and pursue oil-weighted acquisitions where we can add value through our technical expertise and knowledge of the basin.  We have significant experience acquiring and developing oil-weighted properties in the Permian Basin, and we expect to continue to selectively acquire additional properties in the Permian Basin that meet our rate-of-return objectives. Since our formation, we have completed two significant acquisitions and seven bolt-on acquisitions that

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have given us a unique and highly attractive acreage position, underpinned by strong baseline production and proved reserves. We believe our experience as a leading operator and our infrastructure footprint in the Permian Basin provide us with a competitive advantage in successfully executing and integrating acquisitions.

•

Maintain a disciplined, growth-oriented financial strategy.  We intend to fund our growth predominantly with internally generated cash flows while maintaining ample liquidity and access to capital markets. Substantially all of our lease terms allow us to allocate capital among projects in a manner that optimizes both costs and returns, resulting in a highly efficient drilling program. In addition, these terms allow us to adjust our capital spending depending on commodity prices and market conditions. We expect our cash flows from operating activities, pro forma availability under our credit agreement and the net proceeds from this offering to be sufficient to fund our capital expenditures and other obligations necessary to execute our business plan in 2013. Furthermore, we plan to hedge a significant portion of our expected production in order to stabilize our cash flows and maintain liquidity, allowing us to sustain a consistent drilling program, thereby preserving operational efficiencies that help us achieve our targeted rates of return.

Our Competitive Strengths

        We have a number of competitive strengths that we believe will help us to successfully execute our business strategies, including:

•

High caliber management team with substantial technical and operational expertise.  Our founding management team has an average of approximately 20 years of industry experience and over 10 years of history working together with a proven track record of value creation at publicly traded oil and natural gas companies, including Encore Acquisition Company, XTO Energy Inc., Apache Corporation and Anadarko Petroleum Corporation. As of May 31, 2013, we had 23 engineering, land and geosciences technical personnel in our Fort Worth and Midland offices, with personnel experienced in both conventional and unconventional drilling operations. We believe our management and technical team is one of our principal competitive strengths due to our team's industry experience and history of working together in the identification, execution and integration of acquisitions, cost efficient management of profitable, large scale drilling programs and disciplined allocation of capital focused on rates of return.

•

High quality asset base with significant oil exposure in the Midland Basin.  Our acreage is concentrated in Howard, Midland and Glasscock counties, which are some of the most active counties in the Midland Basin. Since 2010, more vertical wells have been drilled in each of Howard and Glasscock counties than any other county in the Midland Basin, and Midland County has been the fifth most active county, based on data from the Texas Railroad Commission. Of the 9,242 vertical wells drilled in the Midland Basin since 2010, 1,579 (17%) have been drilled in Howard County, 1,255 (14%) have been drilled in Glasscock County and 714 (8%) have been drilled in Midland county. Furthermore, we have intentionally focused on crude oil and liquids opportunities to benefit from the relative disparity between oil and natural gas prices on an energy-equivalent basis, which has persisted over the last several years and which we expect to continue in the future. Approximately 58% and 22% of our proved reserves were oil and NGLs, respectively, as of December 31, 2012.

•

De-risked Midland Basin acreage position with multi-year vertical drilling inventory.  Since our management team commenced our development program in January 2011 through May 31, 2013, we have drilled 230 gross operated vertical Wolfberry wells across our leasehold position with a 99% success rate. Based on our extensive analysis of geophysical and technical data gained as a result of our vertical drilling program and from offset operator activity, as of

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May 31, 2013, we have identified 2,298 gross (1,797 net) vertical drilling locations on 40-acre spacing and an additional 2,604 gross (2,060 net) vertical drilling locations on 20-acre spacing across our leasehold, all of which target crude oil and NGLs as the primary objectives across stacked pay zones. Together, these 4,902 gross (3,857 net) identified drilling locations represent over 30 years of drilling inventory based on our expected 2013 drilling program. We view this drilling inventory as de-risked because the drilling locations were selected based on our extensive delineation drilling and production history in the area and well-established industry activity surrounding our acreage.

•

Extensive horizontal development potential.  Operators have drilled hundreds of horizontal wells in the Wolfcamp, Cline and Mississippian formations in the Midland Basin, including numerous horizontal wells offsetting our acreage, and are continuing to accelerate horizontal drilling activity. Multiple Wolfcamp formations are prevalent across our entire leasehold position, and the Cline and Mississippian formations are present across portions of our leasehold position. Based on vertical well control information from our operations and the operations of offset operators, we have initially identified 311 gross (272 net) horizontal drilling locations in the Wolfcamp A formation, 357 gross (317 net) horizontal drilling locations in the Wolfcamp B formation, 133 gross (125 net) horizontal drilling locations in the Wolfcamp C formation, 227 gross (193 net) horizontal drilling locations in the Cline formation and 51 gross (24 net) horizontal drilling locations in the Mississippian formation. In addition, the subsurface data we have collected from our vertical drilling program also supports the potential for additional horizontal drilling in other formations, including the Strawn and Atoka formations. As we continue to expand our vertical drilling activity to our undeveloped acreage, we expect to identify additional horizontal drilling locations. Our vertical drilling has been designed to preserve these future horizontal drilling opportunities and optimize hydrocarbon recovery rates on our acreage. Beginning in the second half of 2013, we intend to supplement our vertical drilling with horizontal drilling in circumstances where we believe that horizontal drilling should offer competitive rates of return.

•

Large, concentrated acreage position with significant operational control.  Substantially all of our acreage is located in three counties in the Midland Basin. Our properties are characterized by large, contiguous acreage blocks, which has enabled us to implement more efficient and cost-effective operating practices and to capture economies of scale, including our installation of centralized production and fluid handling facilities, lowering of rig mobilization times and procurement of better vendor services. We seek to operate our properties so that we can continue to implement these efficient operating practices and control all aspects of our development program, including the selection of specific drilling locations, the timing of the development and the drilling and completion techniques used to efficiently develop our significant resource base. As of December 31, 2012, we operated approximately 99% of our proved reserves.

Recent Developments

Our Capital Restructuring Program

        In the first quarter of 2013, we commenced a plan to enhance our overall capital structure and liquidity, including the execution of our amended and restated credit agreement in March 2013 that extends the maturity date of our reserve based lending facility to 2018. On April 17, 2013, we issued $500 million of 7³/8% senior notes due 2021 and used most of the net proceeds from the offering to reduce the outstanding borrowings under our credit agreement and repay in full and terminate our former second lien term loan, thereby extending a large portion of our then-existing debt maturity to 2021. This offering represents a continuation of our plan, as we intend to apply the estimated proceeds of this offering to further reduce the outstanding borrowings under our credit agreement, provide additional liquidity for use in our drilling program and for general corporate purposes, including potential acquisitions.

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Second Quarter 2013 Drilling and Production

        During the three months ended June 30, 2013, we continued to execute our drilling program, spudding 45 vertical Wolfberry wells, of which 20 are currently producing, 7 are currently being drilled and 18 are waiting to be completed. Our average daily production volumes during the second quarter of 2013 were 6.5 MBbls/D of oil, 12.8 MMcf/D of natural gas and 2.5 MBbls/D of NGLs, or 11.1 MBOE/D in total. This represents an increase of 12% above our averge daily production volumes for the first quarter of 2013 and an increase of 68% above our average daily production volumes for the second quarter of 2012.

Hedge Portfolio

        Currently, we have oil swaps covering: 7,000 Bbls/D at a weighted-average price of $94.93 per Bbl for the remainder of 2013; 7,950 Bbls/D at a weighted-average price of $92.67 per Bbl for 2014; and 1,300 Bbls/D at a weighted-average price of $93.18 per Bbl for 2015. We also have oil collars covering 150 Bbls/D for 2013 containing floors of $75.00 per Bbl and ceilings of $105.95 per Bbl.

2013 Capital Budget

        In 2013, we plan to invest $317 million of development capital, including $15 million for infrastructure, leasing and capitalized workovers, and drill 162 gross (150 net) vertical Wolfberry wells. We also plan to invest $33 million of development capital to drill 4 gross (4 net) horizontal Wolfcamp wells.

        In Howard, we plan to invest $155 million and drill 89 gross (82 net) wells. This includes 25 gross (23 net) PUD locations to be drilled through the Atoka/Mississippian formations at depths of approximately 9,900 feet. Our EURs per well for Howard PUD locations to be drilled through the Atoka/Mississippian formations average 141 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 64 gross (59 net) unproved locations through the Atoka/Mississippian formations.

        In Midland & Other, we plan to invest $95 million and drill 44 gross (42 net) wells. This includes 19 gross (19 net) PUD locations to be drilled through the Strawn/Atoka formations at depths of approximately 11,300 feet. Our EURs per well for Midland & Other PUD locations to be drilled through the Strawn/Atoka formations average 208 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 25 gross (23 net) unproved locations through the Strawn/Atoka formations.

        In Glasscock, we plan to invest $52 million and drill 29 gross (26 net) wells. This includes 8 gross (7 net) PUD locations to be drilled through the Atoka formation at depths of approximately 10,150 feet. Our EURs per well for Glasscock PUD locations to be drilled through the Atoka formation average 118 MBOE as estimated by CG&A in our proved reserve report as of December 31, 2012. In addition, we plan to drill 21 gross (19 net) unproved locations through the Atoka formation.

Our Acquisition History

        A significant portion of our historical growth has been achieved through acquisitions. Since our formation in August 2010, we have completed two significant acquisitions and seven bolt-on acquisitions that have given us a unique and highly attractive acreage positions, underpinned by strong baseline production and proved reserves. Our significant acquisitions were the Element acquisition and the SandRidge acquisition. In the Element acquisition, we acquired certain oil and natural gas properties and related assets in the Permian Basin from Element Petroleum, LP in October 2011 for $253.2 million in cash. The Element properties included approximately 1,400 BOE/D of production and approximately 16.4 MMBOE of proved reserves at the time of acquisition based on internal reserve

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reports. In the SandRidge acquisition, we acquired certain oil and natural gas properties and related assets in the Permian Basin from SandRidge Exploration and Production, LLC in January 2011 for $156.0 million in cash. The SandRidge properties included approximately 1,600 BOE/D of production and approximately 19.1 MMBOE of proved reserves at the time of acquisition based on internal reserve reports. As a result of these acquisitions and our continued operations, the PV-10 of our proved reserves totaled approximately $866.6 million as of December 31, 2012.

Our Properties and Core Project Areas

        The following table summarizes certain operating information of our properties:

													Estimated Net Proved Reserves4
			Identified Drilling Locations1,2,3				2013 Budget3												Average Net Daily Production (BOE/D)5
	Net Acreage2						Gross Wells		Net Wells		Capex (in millions)				Average WI/NRI	% Developed
Area			Gross		Net								MMBOE
Howard		51,556		3,318		2,431		89		82	$	155		33.5	92%/71%		26	%		4,392
Midland & Other		33,709		887		804		44		42		95		33.3	93%/71%		35	%		5,702
Glasscock		13,083		697		622		29		26		52		19.2	95%/73%		27	%		1,863
Total		98,348		4,902		3,857		162		150	$	302		86.0	93%/72%		30	%		11,957

¹

Reflects locations specifically identified by management based on our evaluation of applicable geologic and engineering data. These identified potential drilling locations do not include any potential horizontal drilling locations. The drilling locations on which we actually drill wells will ultimately depend on the availability of capital, regulatory approvals, oil and natural gas prices, costs, actual drilling results and other factors.

²

As of May 31, 2013.

³

Excludes 4 gross (4 net) horizontal Wolfcamp wells and $33 million estimated capital to drill such wells.

⁴

As of December 31, 2012.

⁵

During June 2013, inclusive of oil production of 6,895 Bbls/D in total.

        The Permian Basin, which includes the Delaware Basin, the Central Basin Platform and the Midland Basin, is characterized by an extensive production history, mature infrastructure, long reserve life, multiple producing horizons and enhanced recovery potential. Based on data from the Texas Railroad Commission and the New Mexico Oil Conservation Division, current total production from the Permian Basin is approximately 2 MMBOE/D, of which 60% is oil. As of March 15, 2013, there were 478 total rigs operating in the Permian Basin, making it the most active basin in the United States. According to a report by the Energy Information Administration in August 2012, the Permian Basin is the largest oil producing basin in the United States and contains approximately 23% of the oil reserves in the United States. These reserves are found in multiple proven oil and liquids-rich natural gas producing stratigraphic horizons, which we refer to as stacked pay zones. These multiple stacked pay zones can accommodate multiple completions in a single wellbore with the potential for both vertical and horizontal drilling.

        Our properties are located within the Midland Basin in areas with approximately 3,000 feet to 4,000 feet of stacked pay zones. Our vertical drilling program is targeting the Spraberry, Wolfcamp, Cline, Strawn, Atoka and Mississippian formations. As we continue to develop our inventory of identified vertical drilling locations, we expect to significantly expand our horizontal inventory based upon the information we learn about the formations underlying our leaseholds. In 2012, drilling activity in the Midland Basin continued to show a trend toward horizontal development. Based on data from the Texas Railroad Commission, of the 3,555 wells drilled in the Midland Basin in 2012, 18% were horizontal compared to 10% in 2011. A significant portion of the vertical drilling activity in the Midland Basin targets the Wolfberry Play due to the low-risk nature of the resources available in the play. Companies currently active in the Midland Basin include Apache Corporation, Pioneer Natural

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Resources Company, EOG Resources, Inc., Concho Resources Inc., Energen Corporation and Laredo Petroleum Holdings, Inc.

        Howard.    As of May 31, 2013, we had 69,661 gross (51,556 net) acres and an inventory of 1,577 gross (1,140 net) identified vertical drilling locations on 40-acre spacing and an additional 1,741 gross (1,291 net) identified vertical drilling locations on 20-acre spacing. We are currently operating four rigs in this area and intend to invest $155 million in 2013 and drill 89 gross (82 net) vertical Wolfberry wells. Based upon the 112 gross (105 net) wells we have drilled from the time we began operations in January 2011 through May 31, 2013, we have identified 511 gross (403 net) horizontal drilling locations consisting of 148 gross (121 net) Wolfcamp A locations, 174 gross (145 net) Wolfcamp B locations, 26 gross (25 net) Wolfcamp C locations, 112 gross (88 net) Cline locations and 51 gross (24 net) Mississippian locations. We intend to drill 2 horizontal Wolfcamp A wells in the first half of 2014.

        Midland & Other.    As of May 31, 2013, we had 36,694 gross (33,709 net) acres and an inventory of 424 gross (390 net) identified vertical drilling locations on 40-acre spacing and an additional 463 gross (414 net) identified vertical drilling locations on 20-acre spacing. We are currently operating two rigs in this area and intend to spend $95 million in 2013 and drill 44 gross (42 net) vertical Wolfberry wells. Based upon the 67 gross (67 net) wells we have drilled from the time we began operations in January 2011 through May 31, 2013, we have identified 336 gross (316 net) horizontal drilling locations consisting of 109 gross (102 net) Wolfcamp A locations, 125 gross (118 net) Wolfcamp B locations, 49 gross (48 net) Wolfcamp C locations and 53 gross (48 net) Cline locations. We intend to drill 2 horizontal Wolfcamp B wells in the third quarter of 2013 and 2 horizontal Wolfcamp B wells in the first quarter of 2014.

        Glasscock.    As of May 31, 2013, we had 18,570 gross (13,083) net acres and an inventory of 297 gross (267 net) identified vertical drilling locations on 40-acre spacing and an additional 400 gross (355 net) identified vertical drilling locations on 20-acre spacing. We are currently operating one rig in this area and intend to spend $52 million in 2013 and drill 29 gross (26 net) vertical Wolfberry wells. Based upon the 51 gross (49 net) wells we have drilled from the time we began operations in January 2011 through May 31, 2013, we have identified 232 gross (212 net) horizontal drilling locations consisting of 54 gross (49 net) Wolfcamp A locations, 58 gross (53 net) Wolfcamp B locations, 58 gross (53 net) Wolfcamp C locations and 62 gross (57 net) Cline locations. We intend to drill 2 horizontal Wolfcamp A wells in the fourth quarter of 2013.

        Production Status.    In June 2013, net production was 358,724 BOE, or an average of 11,957 BOE/D, of which 81% was oil and NGLs and 19% was natural gas. During 2012, our average daily net production was 7,047 BOE/D, of which 80% was from oil and NGLs and 20% was from natural gas.

        Facilities.    Our oil and natural gas processing facilities are typical of those found in the Permian Basin. Our facilities located at well locations include field gathering systems, storage tank batteries, saltwater disposal systems, oil/gas/water separation equipment and pumping units. We own three saltwater disposal systems in our Howard County core areas with over 17,000 barrels of water per day ("bwpd") capacity and access to over 35 fresh water supply wells throughout our acreage, a saltwater disposal system in our Glasscock County core area with over 2,700 bwpd capacity and access to over 20 fresh water supply wells throughout our acreage, and three saltwater disposal systems in our Midland County core areas with over 14,000 bwpd capacity and access to over 20 fresh water supply wells throughout our acreage. In addition, we have established pipeline infrastructures in each of these core areas to reduce our need for trucking services.

        Recent and Future Activity.    During 2012, 133 gross (124 net) wells were drilled on our Midland Basin acreage and our 2012 development capital was approximately $276 million. For 2012, our F&D costs were $8.42 per BOE. A total of 24 gross (21 net) wells were drilled on our Midland Basin acreage

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during 2011. As of May 31, 2013 we had 2,298 identified gross potential vertical drilling locations based on 40-acre spacing and an additional 2,604 identified gross potential vertical drilling locations based on 20-acre spacing. We currently expect to drill an estimated 162 gross (150 net) vertical Wolfberry wells and 4 gross (4 net) horizontal Wolfcamp wells on our acreage in 2013. The wells are expected to be drilled to approximately 9,900 feet to 11,300 feet at an estimated average completed gross well cost of approximately $1.80 million to $2.15 million per well. In this prospectus, we define identified potential drilling locations as locations specifically identified by management as an estimation of our multi-year drilling activities based on evaluation of applicable geologic and engineering data on 40-acre or 20-acre spacing as indicated. The availability of local infrastructure, drilling support assets and other factors as management may deem relevant, such as easement restrictions and state and local regulations, are considered in determining such locations. The drilling locations on which we actually drill wells will ultimately depend upon the availability of capital, regulatory approvals, seasonal restrictions, oil and natural gas prices, costs, actual drilling results and other factors.

Oil and Natural Gas Data

Proved Reserves

        Evaluation and Review of Proved Reserves.    Our historical proved reserve estimates were prepared by CG&A, our independent petroleum engineers. The technical persons responsible for preparing our proved reserve estimates meet the requirements with regard to qualifications, independence, objectivity and confidentiality set forth in the Standards Pertaining to the Estimating and Auditing of Oil and Gas Reserves Information promulgated by the Society of Petroleum Engineers. The third-party engineering firm does not own an interest in any of our properties, nor is it employed by us on a contingent basis. Copies of the independent petroleum engineering firm's proved reserve report as of December 31, 2012 is attached hereto as an exhibit.

        We maintain an internal staff of petroleum engineers and geoscience professionals who worked closely with our independent reserve engineers to ensure the integrity, accuracy and timeliness of the data used to calculate our proved reserves relating to our assets in the Permian Basin. Our internal technical team members meet with our independent reserve engineers periodically during the period covered by the proved reserve report to discuss the assumptions and methods used in the proved reserve estimation process. We provide historical information to the independent reserve engineers for our properties, such as ownership interest, oil and natural gas production, well test data, commodity prices and operating and development costs. Jennifer Palko, our Vice President—Business Development and Engineering, is primarily responsible for overseeing the preparation of all of our reserve estimates. Ms. Palko is a petroleum engineer with over 19 years of reservoir and operations experience and our geoscience staff has an average of approximately 14 years of industry experience per person.

        The preparation of our proved reserve estimates are completed in accordance with our internal control procedures. These procedures, which are intended to ensure reliability of reserve estimations, include the following:

•

review and verification of historical production data, which data is based on actual production as reported by us;

•

preparation of reserve estimates by Ms. Palko or under her direct supervision;

•

review by Ms. Palko of all of our reported proved reserves at the close of each quarter, including the review of all significant reserve changes and all new proved undeveloped reserves additions;

•

direct reporting responsibilities by Ms. Palko to our Chief Executive Officer; and

•

verification of property ownership by our land department.

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        Estimation of Proved Reserves.    Under SEC rules, proved reserves are those quantities of oil and natural gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible—from a given date forward, from known reservoirs and under existing economic conditions, operating methods and government regulations—prior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain, regardless of whether deterministic or probabilistic methods are used for the estimation. If deterministic methods are used, the SEC has defined reasonable certainty for proved reserves as a "high degree of confidence that the quantities will be recovered." All of our proved reserves as of December 31, 2012 were estimated using a deterministic method. The estimation of reserves involves two distinct determinations. The first determination results in the estimation of the quantities of recoverable oil and natural gas and the second determination results in the estimation of the uncertainty associated with those estimated quantities in accordance with the definitions established under SEC rules. The process of estimating the quantities of recoverable oil and natural gas reserves relies on the use of certain generally accepted analytical procedures. These analytical procedures fall into four broad categories or methods: (1) production performance-based methods; (2) material balance-based methods; (3) volumetric-based methods; and (4) analogy. These methods may be used singularly or in combination by the reserve evaluator in the process of estimating the quantities of reserves. Reserves for proved developed producing wells were estimated using production performance methods for the vast majority of properties. Certain new producing properties with very little production history were forecast using a combination of production performance and analogy to similar production, both of which are considered to provide a relatively high degree of accuracy. Non-producing reserve estimates, for developed and undeveloped properties, were forecast using either volumetric or analogy methods, or a combination of both. These methods provide a relatively high degree of accuracy for predicting proved developed non-producing and proved undeveloped reserves for our properties, due to the mature nature of the properties targeted for development and an abundance of subsurface control data.

        To estimate economically recoverable proved reserves and related future net cash flows, CG&A considered many factors and assumptions, including the use of reservoir parameters derived from geological, geophysical and engineering data which cannot be measured directly, economic criteria based on current costs and the SEC pricing requirements and forecasts of future production rates.

        Under SEC rules, reasonable certainty can be established using techniques that have been proven effective by actual production from projects in the same reservoir or an analogous reservoir or by other evidence using reliable technology that establishes reasonable certainty. Reliable technology is a grouping of one or more technologies (including computational methods) that has been field tested and has been demonstrated to provide reasonably certain results with consistency and repeatability in the formation being evaluated or in an analogous formation. To establish reasonable certainty with respect to our estimated proved reserves, the technologies and economic data used in the estimation of our proved reserves have been demonstrated to yield results with consistency and repeatability, and include production and well test data, downhole completion information, geologic data, electrical logs, radioactivity logs, core analyses, available seismic data and historical well cost and operating expense data.

        Summary of Oil and Natural Gas Reserves.    The following table presents our estimated net proved oil and natural gas reserves as of December 31, 2012 and 2011, based on the proved reserve reports prepared by CG&A, an independent petroleum engineering firm, and such proved reserve reports have been prepared in accordance with the rules and regulations of the SEC. All of our proved reserves are located in the United States. Copies of the proved reserve reports as of December 31, 2012 and 2011 prepared by CG&A with respect to our properties are included as exhibits to the registration statement of which this prospectus forms a part. Our estimates of net proved reserves have not been filed with or

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included in reports to any federal authority or agency other than the SEC in connection with this offering.

	December 31,
	2012		2011
Proved developed reserves:
Oil (MBbls)		14,470		7,942
Natural gas (MMcf)		31,965		14,063
NGLs (MBbls)		5,900		3,211
Combined (MBOE)		25,698		13,496
Proved undeveloped reserves:
Oil (MBbls)		34,953		18,030
Natural gas (MMcf)		71,718		37,497
NGLs (MBbls)		13,375		8,338
Combined (MBOE)		60,281		32,618
Proved reserves:
Oil (MBbls)		49,423		25,972
Natural gas (MMcf)		103,683		51,560
NGLs (MBbls)		19,275		11,549
Combined (MBOE)		85,979		46,114

        Reserve engineering is and must be recognized as a subjective process of estimating volumes of economically recoverable oil and natural gas that cannot be measured in an exact manner. The accuracy of any reserve estimate is a function of the quality of available data and of engineering and geological interpretation. As a result, the estimates of different engineers often vary. In addition, the results of drilling, testing and production may justify revisions of such estimates. Accordingly, reserve estimates often differ from the quantities of oil and natural gas that are ultimately recovered. Estimates of economically recoverable oil and natural gas and of future net revenues are based on a number of variables and assumptions, all of which may vary from actual results, including geologic interpretation, prices and future production rates and costs. Please read "Risk Factors" appearing elsewhere in this prospectus.

        Additional information regarding our proved reserves can be found in the notes to our consolidated financial statements included elsewhere in this prospectus and the proved reserve reports as of December 31, 2012 and 2011 which are included as exhibits to the registration statement of which this prospectus forms a part.

Proved Undeveloped Reserves (PUDs)

        As of December 31, 2012, our proved undeveloped reserves were composed of 34,953 MBbls of oil, 71,718 MMcf of natural gas and 13,375 MBbls of NGLs, for a total of 60,281 MBOE. PUDs will be converted from undeveloped to developed as the applicable wells begin production.

        The following table summarizes our changes in PUDs during 2012 (in MBOE):

Balance, December 31, 2011	32,618
Purchases of minerals-in-place	6,393
Extensions and discoveries	35,810
Revisions of previous estimates1	(8,087	)
Transfers to proved developed	(6,453	)
Balance, December 31, 2012	60,281

¹

Revisions to previous estimates are comprised of 7,185 MBOE of PUDs that are not currently scheduled to be drilled within the next five years and 902 MBOE of negative net revisions due to the combination of price, cost and technical revisions.

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        Costs incurred relating to the development of PUDs reflected in our 2011 proved reserve report were $135.3 million during 2012. In addition, we incurred costs of $65.9 million to develop locations that became classified as PUDs during 2012. Estimated future development costs relating to the development of PUDs are projected to be approximately $103.0 million in 2013, $163.2 million in 2014, $174.1 million in 2015, $315.9 million in 2016 and $289.7 million in 2017. As we continue to develop our properties and have more well production and completion data, we believe we will continue to realize cost savings and experience lower relative drilling and completion costs as we convert PUDs into proved developed reserves in upcoming years. All of our PUD drilling locations are scheduled to be drilled prior to the end of 2017.

        As of December 31, 2012, approximately 4% of our total proved reserves were classified as proved developed non-producing.

Oil and Natural Gas Production Prices and Production Costs

Production and Price History

        The following table sets forth information regarding net production of oil, natural gas and NGLs, and certain price and cost information for the periods indicated:

	Three months ended March 31,				Year ended December 31,
	2013		2012		2012		2011
Total production volumes:
Oil (MBbls)		542		276		1,457		556
Natural gas (MMcf)		1,030		534		3,163		1,017
NGLs (MBbls)		183		102		595		239
Combined (MBOE)		896		468		2,579		964
Average daily production volumes:
Oil (Bbls/D)		6,023		3,036		3,981		1,523
Natural gas (Mcf/D)		11,446		5,871		8,641		2,786
NGLs (Bbls/D)		2,028		1,125		1,625		654
Combined (BOE/D)		9,959		5,140		7,047		2,641
Average realized prices:
Oil ($/Bbl) (excluding impact of cash settled derivatives)	$	84.23	$	99.29	$	87.90	$	92.08
Oil ($/Bbl) (after impact of cash settled derivatives)		83.65		89.53		87.16		87.16
Natural gas ($/Mcf)		3.27		2.71		2.66		3.46
NGLs ($/Bbl)		31.34		42.48		34.65		45.96
Combined ($/BOE) (excluding impact of cash settled derivatives)		61.08		71.05		60.91		68.13
Combined ($/BOE) (after impact of cash settled derivatives)		60.73		65.28		60.50		65.29
Expenses (per BOE):
Lease operating	$	8.07	$	10.05	$	9.89	$	13.82
Production, severance and ad valorem taxes		4.12		5.03		4.05		4.90
Depletion, depreciation and amortization		20.14		20.55		21.11		20.48
General and administrative		3.73		5.55		3.75		8.01

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Productive Wells

        As of December 31, 2012, we owned an average 92% working interest in 492 gross (454 net) productive wells. Productive wells consist of producing wells and wells capable of production, including oil wells awaiting connection to production facilities. Gross wells are the total number of producing wells in which we have an interest, and net wells are the sum of our fractional working interests owned in gross wells.

Developed and Undeveloped Acreage

        The following table sets forth information as of May 31, 2013 relating to our leasehold acreage. Developed acres are acres spaced or assigned to productive wells and does not include undrilled acreage held by production under the terms of the lease. Undeveloped acres are acres on which wells have not been drilled or completed to a point that would permit the production of commercial quantities of oil or natural gas, regardless of whether such acreage contains proved reserves. A gross acre is an acre in which a working interest is owned. The number of gross acres is the total number of acres in which a working interest is owned. A net acre is deemed to exist when the sum of the fractional ownership working interests in gross acres equals one. The number of net acres is the sum of the fractional working interests owned in gross acres expressed as whole numbers and fractions thereof.

	Developed Acreage				Undeveloped Acreage				Total Acreage
Area	Gross		Net		Gross		Net		Gross		Net
Howard		57,186		39,466		12,475		12,090		69,661		51,556
Midland & Other		10,768		9,504		25,926		24,205		36,694		33,709
Glasscock		10,435		5,051		8,135		8,032		18,570		13,083
Total		78,389		54,021		46,536		44,327		124,925		98,348

        Many of the leases comprising the undeveloped acreage set forth in the table above will expire at the end of their respective primary terms unless production from the leasehold acreage has been established prior to such date, in which event the lease will remain in effect until the cessation of production. As of May 31, 2013, we had leases representing 9,639 gross (7,653 net) acres scheduled to expire in 2013, 5,362 gross (4,257 net) acres scheduled to expire in 2014, 9,213 gross (7,363 net) acres scheduled to expire in 2015, 27,224 gross (21,049 net) acres scheduled to expire in 2016 and no net acres scheduled to expire in 2017. We have not attributed any PUD reserves to acreage whose expiration date precedes the scheduled date for PUD drilling.

Drilling Results

        The following table sets forth information with respect to the number of wells completed during the periods indicated. The information should not be considered indicative of future performance, nor should it be assumed that there is necessarily any correlation between the number of productive wells

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drilled, quantities of reserves found or economic value. Productive wells are those that produce commercial quantities of hydrocarbons, whether or not they produce a reasonable rate of return.

	Year ended December 31,
	2012				2011
	Gross		Net		Gross		Net
Development Wells:
Productive		102		94		18		15
Dry holes		2		2		0		0
		104		96		18		15
Exploratory Wells:
Productive		29		28		5		5
Dry holes		0		0		1		1
		29		28		6		6
Total:
Productive		131		122		23		20
Dry holes		2		2		1		1
		133		124		24		21

        As of December 31, 2012, we had 25 gross (23 net) wells in the process of drilling, completing or dewatering or shut in awaiting infrastructure that are not reflected in the above table.

Operations

General

        As of December 31, 2012, we operated approximately 99% of our proved reserves. As operator, we design and manage the development of a well and supervise operation and maintenance activities on a day-to-day basis. Independent contractors engaged by us provide all the equipment and personnel associated with these activities. We employ petroleum engineers, geologists and land professionals who work to improve production rates, increase reserves and lower the cost of operating our oil and natural gas properties.

Marketing and Customers

        We market all of the oil and natural gas production from properties we operate for both our account and the account of the other working interest owners in these properties. We sell our natural gas production to purchasers at market price under contracts with terms ranging from month-to-month to over five years. All of our oil is also sold under various contracts with a month-to-month term.

        We normally sell production to a relatively small number of customers, as is customary in the exploration, development and production business. For 2012, three purchasers accounted for more than 10% of our revenues: Pecos Gathering & Marketing (43%); Occidental Petroleum Corporation (29%); and DCP Midstream (12%). For 2011, three purchasers accounted for more than 10% of our revenues: Occidental Petroleum Corporation (58%); DCP Midstream (13%); and Pecos Gathering & Marketing (13%). If a major customer decided to stop purchasing oil and natural gas from us, revenues could decline and our operating results and financial condition could be harmed. However, based on the current demand for oil and natural gas, and the availability of other purchasers, we believe that the loss of any one or all of our major purchasers would not have a material adverse effect on our financial condition and results of operations, as crude oil and natural gas are fungible products with well-established markets and numerous purchasers.

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Transportation

        During the initial development of our fields, we consider all gathering and delivery infrastructure in the areas of our production. Our oil is transported from the wellhead to our tank batteries by our gathering systems. The oil is then transported by the purchaser by truck or pipeline to a tank farm, another pipeline or a refinery. Our natural gas is transported from the wellhead to the purchaser's meter and pipeline interconnection point through our gathering system.

Competition

        The oil and natural gas industry is intensely competitive, and we compete with other companies that have greater resources. Many of these companies not only explore for and produce oil and natural gas, but also carry on midstream and refining operations and market petroleum and other products on a regional, national or worldwide basis. These companies may be able to pay more for productive oil and natural gas properties and exploratory prospects or to define, evaluate, bid for and purchase a greater number of properties and prospects than our financial or human resources permit. In addition, these companies may have a greater ability to continue exploration activities during periods of low oil and natural gas market prices. Our larger or more integrated competitors may be able to absorb the burden of present and future federal, state, local and other laws and regulations more easily than we can, which would adversely affect our competitive position. Our ability to acquire additional properties and to discover reserves in the future will be dependent upon our ability to evaluate and select suitable properties and to consummate transactions in a highly competitive environment. In addition, because we have fewer financial and human resources than many companies in our industry, we may be at a disadvantage in bidding for exploratory prospects and producing reserves.

Title to Properties

        As is customary in the oil and natural gas industry, we initially conduct only a cursory review of the title to our properties. At such time as we determine to conduct drilling operations on those properties, we conduct a thorough title examination and perform curative work with respect to significant defects prior to commencement of drilling operations. To the extent title opinions or other investigations reflect title defects on those properties, we are typically responsible for curing any title defects at our expense. We generally will not commence drilling operations on a property until we have cured any material title defects on such property. We have obtained title opinions on substantially all of our properties and believe that we have satisfactory title to our properties in accordance with standards generally accepted in the oil and natural gas industry. Prior to completing an acquisition of oil and natural gas leases, we perform title reviews on the most significant leases and, depending on the materiality of properties, we may obtain a title opinion, obtain an updated title review or opinion or review previously obtained title opinions. Our oil and natural gas properties are subject to customary royalty and other interests, liens for current taxes and other burdens which we believe do not materially interfere with the use of or affect our carrying value of the properties.

Oil and Natural Gas Leases

        The typical oil and natural gas lease agreement covering our properties provides for the payment of royalties to the mineral owner for all oil and natural gas produced from any wells drilled on the leased premises. The lessor royalties and other leasehold burdens on our properties generally range from 20% to 30%, resulting in a net revenue interest to us of 70% to 80%.

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Regulation

Environmental Matters and Regulation

        Our oil and natural gas exploration, development and production operations are subject to stringent laws and regulations governing the discharge of materials into the environment or otherwise relating to environmental protection. Numerous governmental agencies, such as the EPA, issue regulations which often require difficult and costly compliance measures that carry substantial administrative, civil and criminal penalties and may result in injunctive obligations for non-compliance. These laws and regulations may require the acquisition of a permit before drilling commences, restrict the types, quantities and concentrations of various substances that can be released into the environment in connection with drilling and production activities, limit or prohibit construction or drilling activities on certain lands lying within wilderness, wetlands, ecologically sensitive and other protected areas, require action to prevent or remediate pollution from current or former operations, such as plugging abandoned wells or closing pits, result in the suspension or revocation of necessary permits, licenses and authorizations, require that additional pollution controls be installed and impose substantial liabilities for pollution resulting from our operations or relate to our owned or operated facilities. The strict and joint and several liability nature of such laws and regulations could impose liability upon us regardless of fault. Moreover, it is not uncommon for neighboring landowners and other third parties to file claims for personal injury and property damage allegedly caused by the release of hazardous substances, hydrocarbons or other waste products into the environment. Changes in environmental laws and regulations occur frequently, and any changes that result in more stringent and costly pollution control or waste handling, storage, transport, disposal or cleanup requirements could materially adversely affect our results of operations and financial condition, as well as the oil and natural gas industry in general. Our management believes that we are in substantial compliance with applicable environmental laws and regulations and we have not experienced any material adverse effect from compliance with these environmental requirements. This trend, however, may not continue in the future.

        Waste Handling.    The Resource Conservation and Recovery Act, as amended, ("RCRA") and comparable state statutes and regulations promulgated thereunder, affect oil and natural gas exploration, development and production activities by imposing requirements regarding the generation, transportation, treatment, storage, disposal and cleanup of hazardous and non-hazardous wastes. With federal approval, the individual states administer some or all of the provisions of RCRA, sometimes in conjunction with their own, more stringent requirements. Although most wastes associated with the exploration, development and production of crude oil and natural gas are exempt from regulation as hazardous wastes under RCRA, such wastes may constitute "solid wastes" that are subject to the less stringent requirements of non-hazardous waste provisions. However, we cannot assure you that the EPA or state or local governments will not adopt more stringent requirements for the handling of non-hazardous wastes or categorize some non-hazardous wastes as hazardous for future regulation. Indeed, legislation has been proposed from time to time in Congress to re-categorize certain oil and natural gas exploration, development and production wastes as "hazardous wastes." Any such changes in the laws and regulations could have a material adverse effect on our capital expenditures and operating expenses.

        Administrative, civil and criminal penalties can be imposed for failure to comply with waste handling requirements. We believe that we are in substantial compliance with applicable requirements related to waste handling, and that we hold all necessary and up-to-date permits, registrations and other authorizations to the extent that our operations require them under such laws and regulations. Although we do not believe the current costs of managing our wastes, as presently classified, to be significant, any legislative or regulatory reclassification of oil and natural gas exploration and production wastes could increase our costs to manage and dispose of such wastes.

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        Remediation of Hazardous Substances.    The Comprehensive Environmental Response, Compensation and Liability Act, as amended, ("CERCLA") also known as the "Superfund" law, and analogous state laws, generally imposes strict and joint and several liability, without regard to fault or legality of the original conduct, on classes of persons who are considered to be responsible for the release of a "hazardous substance" into the environment. These persons include the current owner or operator of a contaminated facility, a former owner or operator of the facility at the time of contamination, and those persons that disposed or arranged for the disposal of the hazardous substance at the facility. Under CERCLA and comparable state statutes, persons deemed "responsible parties" may be subject to strict and joint and several liability for the costs of removing or remediating previously disposed wastes (including wastes disposed of or released by prior owners or operators) or property contamination (including groundwater contamination), for damages to natural resources and for the costs of certain health studies. In addition, it is not uncommon for neighboring landowners and other third parties to file claims for personal injury and property damage allegedly caused by the hazardous substances released into the environment. In the course of our operations, we use materials that, if released, would be subject to CERCLA and comparable state statutes. Therefore, governmental agencies or third parties may seek to hold us responsible under CERCLA and comparable state statutes for all or part of the costs to clean up sites at which such "hazardous substances" have been released.

        Water Discharges.    The Federal Water Pollution Control Act of 1972, as amended, also known as the Clean Water Act (the "CWA"), the SDWA, the Oil Pollution Act (the "OPA") and analogous state laws and regulations promulgated thereunder impose restrictions and strict controls regarding the unauthorized discharge of pollutants, including produced waters and other gas and oil wastes, into navigable waters of the United States, as well as state waters. The discharge of pollutants into regulated waters is prohibited, except in accordance with the terms of a permit issued by the EPA or the state. The CWA and regulations implemented thereunder also prohibit the discharge of dredge and fill material into regulated waters, including jurisdictional wetlands, unless authorized by an appropriately issued permit. Spill prevention, control and countermeasure plan requirements under federal law require appropriate containment berms and similar structures to help prevent the contamination of navigable waters in the event of a petroleum hydrocarbon tank spill, rupture or leak. These laws and regulations also prohibit certain activity in wetlands unless authorized by a permit issued by the U.S. Army Corps of Engineers. The EPA has also adopted regulations requiring certain oil and natural gas exploration and production facilities to obtain individual permits or coverage under general permits for storm water discharges. In addition, on October 20, 2011, the EPA announced a schedule to develop pre-treatment standards for wastewater discharges produced by natural gas extraction from underground coalbed and shale formations. The EPA stated that it will gather data, consult with stakeholders, including ongoing consultation with industry, and solicit public comment on a proposed rule for coalbed methane in 2013 and a proposed rule for shale gas in 2014. Costs may be associated with the treatment of wastewater or developing and implementing storm water pollution prevention plans, as well as for monitoring and sampling the storm water runoff from certain of our facilities. Some states also maintain groundwater protection programs that require permits for discharges or operations that may impact groundwater conditions.

        The OPA is the primary federal law for oil spill liability. The OPA contains numerous requirements relating to the prevention of and response to petroleum releases into waters of the United States, including the requirement that operators of offshore facilities and certain onshore facilities near or crossing waterways must develop and maintain facility response contingency plans and maintain certain significant levels of financial assurance to cover potential environmental cleanup and restoration costs. The OPA subjects owners of facilities to strict, joint and several liability for all containment and cleanup costs and certain other damages arising from a release, including, but not limited to, the costs of responding to a release of oil to surface waters.

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        Noncompliance with the CWA or the OPA may result in substantial administrative, civil and criminal penalties, as well as injunctive obligations. We believe we are in material compliance with the requirements of each of these laws.

        Air Emissions.    The CAA and comparable state laws and regulations regulate emissions of various air pollutants through the issuance of permits and the imposition of other requirements. The EPA has developed, and continues to develop, stringent regulations governing emissions of air pollutants at specified sources. New facilities may be required to obtain permits before work can begin, and existing facilities may be required to obtain additional permits and incur capital costs in order to remain in compliance. For example, on April 17, 2012, the EPA approved final regulations under the CAA that establish new emission controls for oil and natural gas production and processing operations, which regulations are discussed in more detail in "—Regulation of Hydraulic Fracturing." These laws and regulations may increase the costs of compliance for some facilities we own or operate, and federal and state regulatory agencies can impose administrative, civil and criminal penalties for non-compliance with air permits or other requirements of the CAA and associated state laws and regulations. We believe that we are in substantial compliance with all applicable air emissions regulations and that we hold all necessary and valid construction and operating permits for our operations. Obtaining or renewing permits has the potential to delay the development of oil and natural gas projects.

        Climate Change.    Many nations have agreed to limit emissions of GHGs pursuant to the Kyoto Protocol. Methane, a primary component of natural gas, and carbon dioxide, a byproduct of the burning of oil, natural gas and refined petroleum products, are GHGs regulated by the Kyoto Protocol. Although the United States is not participating in the Kyoto Protocol at this time, several states or geographic regions have adopted legislation and regulations to reduce emissions of GHGs. The EPA has adopted two sets of related rules, one of which purports to regulate emissions of GHGs from motor vehicles and the other of which regulates emissions of GHGs from certain large stationary sources of emissions such as power plants or industrial facilities. The EPA finalized the motor vehicle rule in April 2010 and it became effective January 2011. The EPA adopted the stationary source rule, also known as the "Tailoring Rule," in May 2010, and it also became effective January 2011. Additionally, in September 2009, the EPA issued a final rule requiring the reporting of GHG emissions from specified large GHG emission sources in the U.S., including NGLs fractionators and local natural gas/distribution companies, beginning in 2011 for emissions occurring in 2010. In November 2010, the EPA expanded its existing GHG reporting rule to include onshore and offshore oil and natural gas production and onshore processing, transmission, storage and distribution facilities, which may include certain of our facilities, beginning in 2012 for emissions occurring in 2011. In addition, the EPA has continued to adopt GHG regulations of other industries, such as the March 2012 proposed GHG rule restricting future development of coal-fired power plants. As a result of this continued regulatory focus, future GHG regulations of the oil and natural gas industry remain a possibility.

        In addition, the U.S. Congress has from time to time considered adopting legislation to reduce emissions of GHGs and almost one-half of the states have already taken legal measures to reduce emissions of GHGs primarily through the planned development of GHG emission inventories and/or regional GHG cap and trade programs. Although the U.S. Congress has not adopted such legislation at this time, it may do so in the future and many states continue to pursue regulations to reduce greenhouse gas emissions. Most of these cap and trade programs work by requiring major sources of emissions, such as electric power plants or major producers of fuels, such as refineries and natural gas processing plants, to acquire and surrender emission allowances that correspond to their annual emissions of GHGs. The number of allowances available for purchase is reduced each year until the overall GHG emission reduction goal is achieved. As the number of GHG emission allowances declines each year, the cost or value of such allowances is expected to escalate significantly.

        Restrictions on GHG emissions that may be imposed in various states could adversely affect the oil and natural gas industry. While we are subject to certain federal GHG monitoring and reporting

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requirements, our operations are not adversely impacted by existing federal, state and local climate change initiatives and, at this time, it is not possible to accurately estimate how future laws or regulations addressing GHG emissions would impact our business.

Regulation of Hydraulic Fracturing

        Hydraulic fracturing is an important common practice that is used to stimulate production of hydrocarbons, particularly natural gas, from tight formations, including shales. The process involves the injection of water, sand and chemicals under pressure into formations to fracture the surrounding rock and stimulate production. The SDWA regulates the underground injection of substances through the UIC program. Hydraulic fracturing generally is exempt from regulation under the UIC program, and the hydraulic fracturing process is typically regulated by state oil and natural gas commissions. The EPA, however, has recently taken the position that hydraulic fracturing with fluids containing diesel fuel is subject to regulation under the UIC program, specifically as "Class II" UIC wells. At the same time, the EPA has commenced a study of the potential environmental impacts of hydraulic fracturing activities, and a committee of the U.S. House of Representatives is also conducting an investigation of hydraulic fracturing practices. Moreover, the EPA commenced a study regarding the environmental effects of hydraulic fracturing activities. The EPA issued a Progress Report in December 2012 and a final draft is anticipated by 2014 for peer review and public comment. As part of these studies, both the EPA and the House committee have requested that certain companies provide them with information concerning the chemicals used in the hydraulic fracturing process. These studies, depending on their results, could spur initiatives to regulate hydraulic fracturing under the SDWA or otherwise. Further, on October 20, 2011, the EPA announced its intention to propose federal Clean Water Act regulations by 2014 governing wastewater discharges from hydraulic fracturing and certain other natural gas operations. Legislation to amend the SDWA to repeal the exemption for hydraulic fracturing from the definition of "underground injection" and require federal permitting and regulatory control of hydraulic fracturing, as well as legislative proposals to require disclosure of the chemical constituents of the fluids used in the fracturing process, were proposed in recent sessions of Congress. The U.S. Congress continues to consider legislation to amend the SDWA.

        Federal agencies are also considering additional regulation of hydraulic fracturing. On October 20, 2011, the EPA announced its intention to propose federal Clean Water Act regulations by 2014 governing wastewater discharges from hydraulic fracturing and certain other natural gas operations.

        On August 16, 2012, the EPA published final regulations under the CAA that establish new air emission controls for oil and natural gas production and natural gas processing operations. Specifically, the EPA's rule package includes New Source Performance Standards to address emissions of sulfur dioxide and VOCs and a separate set of emission standards to address hazardous air pollutants frequently associated with oil and natural gas production and processing activities. The final rule includes a 95% reduction in VOCs emitted by requiring the use of reduced emission completions or "green completions" on all hydraulically-fractured wells constructed or refractured after January 1, 2015. The rules also establish specific new requirements regarding emissions from compressors, controllers, dehydrators, storage tanks and other production equipment. The EPA received numerous requests for reconsideration of these rules from both industry and the environmental community, and court challenges to the rules were also filed. The EPA intends to issue revised rules in 2013 that are likely responsive to some of these requests. For example, on April 12, 2013, the EPA published a proposed amendment extending compliance dates for certain storage vessels. The final revised rules could require modifications to our operations or increase our capital and operating costs without being offset by increased product capture. At this point, we cannot predict the final regulatory requirements or the cost to comply with such requirements with any certainty. The U.S. Department of the Interior has also announced its intention to propose a new rule regulating hydraulic fracturing activities on federal lands, including requirements for disclosure, wellbore integrity and handling of flowback water.

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        Several states, including Texas have adopted, or are considering adopting, regulations that could restrict or prohibit hydraulic fracturing in certain circumstances and/or require the disclosure of the composition of hydraulic fracturing fluids. In June 2011, Texas enacted a law requiring oil and natural gas operators to publicly disclose the chemicals used in the hydraulic fracturing process, effective as of September 1, 2011. The Texas Railroad Commission has adopted rules and regulations implementing this legislation that will apply to all wells for which the Texas Railroad Commission issues an initial drilling permit on or after February 1, 2012. The new law requires that the well operator disclose the list of chemical ingredients subject to the requirements of the OSHA for disclosure on an internet website and also file the list of chemicals with the Texas Railroad Commission with the well completion report. The total volume of water used to hydraulically fracture a well must also be disclosed to the public and filed with the Texas Railroad Commission.

        There has been increasing public controversy regarding hydraulic fracturing with regard to use of fracturing fluids, impacts on drinking water supplies, use of waters and the potential for impacts to surface water, groundwater and the environment generally. A number of lawsuits and enforcement actions have been initiated across the country implicating hydraulic fracturing practices. If new laws or regulations that significantly restrict hydraulic fracturing are adopted, such laws could make it more difficult or costly for us to perform fracturing to stimulate production from tight formations as well as make it easier for third parties opposing the hydraulic fracturing process to initiate legal proceedings based on allegations that specific chemicals used in the fracturing process could adversely affect groundwater. In addition, if hydraulic fracturing is further regulated at the federal or state level, our fracturing activities could become subject to additional permitting and financial assurance requirements, more stringent construction specifications, increased monitoring, reporting and recordkeeping obligations, plugging and abandonment requirements and also to attendant permitting delays and potential increases in costs. Such legislative changes could cause us to incur substantial compliance costs, and compliance or the consequences of any failure to comply by us could have a material adverse effect on our financial condition and results of operations. At this time, it is not possible to estimate the impact on our business of newly enacted or potential federal or state legislation governing hydraulic fracturing.

Other Regulation of the Oil and Natural Gas Industry

        The oil and natural gas industry is extensively regulated by numerous federal, state and local authorities. Legislation affecting the oil and natural gas industry is under constant review for amendment or expansion, frequently increasing the regulatory burden. Also, numerous departments and agencies, both federal and state, are authorized by statute to issue rules and regulations that are binding on the oil and natural gas industry and its individual members, some of which carry substantial penalties for failure to comply. Although the regulatory burden on the oil and natural gas industry increases our cost of doing business and, consequently, affects our profitability, these burdens generally do not affect us any differently or to any greater or lesser extent than they affect other companies in the industry with similar types, quantities and locations of production.

        The availability, terms and cost of transportation significantly affect sales of oil and natural gas. The interstate transportation and sale for resale of oil and natural gas is subject to federal regulation, including regulation of the terms, conditions and rates for interstate transportation, storage and various other matters, primarily by FERC. Federal and state regulations govern the price and terms for access to oil and natural gas pipeline transportation. FERC's regulations for interstate oil and natural gas transmission in some circumstances may also affect the intrastate transportation of oil and natural gas.

        Although oil and natural gas prices are currently unregulated, Congress historically has been active in the area of oil and natural gas regulation. We cannot predict whether new legislation to regulate oil and natural gas might be proposed, what proposals, if any, might actually be enacted by Congress or

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the various state legislatures, and what effect, if any, the proposals might have on our operations. Sales of condensate, oil and NGLs are not currently regulated and are made at market prices.

        Drilling and Production.    Our operations are subject to various types of regulation at the federal, state and local level. These types of regulation include requiring permits for the drilling of wells, drilling bonds and reports concerning operations. The state, and some counties and municipalities, in which we operate also regulate one or more of the following:

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the location of wells;

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the method of drilling and casing wells;

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the timing of construction or drilling activities, including seasonal wildlife closures;

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the rates of production or "allowables";

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the surface use and restoration of properties upon which wells are drilled;

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the plugging and abandonment of wells; and

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notice to, and consultation with, surface owners and other third parties.

        State laws regulate the size and shape of drilling and spacing units or proration units governing the pooling of oil and natural gas properties. Some states allow forced pooling or integration of tracts to facilitate exploration while other states rely on voluntary pooling of lands and leases. In some instances, forced pooling or unitization may be implemented by third parties and may reduce our interest in the unitized properties. In addition, state conservation laws establish maximum rates of production from oil and natural gas wells, generally prohibit the venting or flaring of natural gas and impose requirements regarding the ratability of production. These laws and regulations may limit the amount of oil and natural gas we can produce from our wells or limit the number of wells or the locations at which we can drill. Moreover, each state generally imposes a production or severance tax with respect to the production and sale of oil, natural gas and NGLs within its jurisdiction. States do not regulate wellhead prices or engage in other similar direct regulation, but we cannot assure you that they will not do so in the future. The effect of such future regulations may be to limit the amounts of oil and natural gas that may be produced from our wells, negatively affect the economics of production from these wells or to limit the number of locations we can drill.

        Federal, state and local regulations provide detailed requirements for the abandonment of wells, closure or decommissioning of production facilities and pipelines and for site restoration in areas where we operate. The U.S. Army Corps of Engineers and many other state and local authorities also have regulations for plugging and abandonment, decommissioning and site restoration. Although the U.S. Army Corps of Engineers does not require bonds or other financial assurances, some state agencies and municipalities do have such requirements.

        Natural Gas Sales and Transportation.    Historically, federal legislation and regulatory controls have affected the price of the natural gas we produce and the manner in which we market our production. FERC has jurisdiction over the transportation and sale for resale of natural gas in interstate commerce by natural gas companies under the Natural Gas Act of 1938 and the Natural Gas Policy Act of 1978. Since 1978, various federal laws have been enacted which have resulted in the complete removal of all price and non-price controls for sales of domestic natural gas sold in "first sales," which include all of our sales of our own production. Under the Energy Policy Act of 2005, FERC has substantial enforcement authority to prohibit the manipulation of natural gas markets and enforce its rules and orders, including the ability to assess substantial civil penalties.

        FERC also regulates interstate natural gas transportation rates and service conditions and establishes the terms under which we may use interstate natural gas pipeline capacity, which affects the marketing of natural gas that we produce, as well as the revenues we receive for sales of our natural

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gas and release of our natural gas pipeline capacity. Commencing in 1985, FERC promulgated a series of orders, regulations and rule makings that significantly fostered competition in the business of transporting and marketing gas. Today, interstate pipeline companies are required to provide nondiscriminatory transportation services to producers, marketers and other shippers, regardless of whether such shippers are affiliated with an interstate pipeline company. FERC's initiatives have led to the development of a competitive, open access market for natural gas purchases and sales that permits all purchasers of natural gas to buy gas directly from third-party sellers other than pipelines. However, the natural gas industry historically has been very heavily regulated; therefore, we cannot guarantee that the less stringent regulatory approach currently pursued by FERC and Congress will continue indefinitely into the future nor can we determine what effect, if any, future regulatory changes might have on our natural gas related activities.

        Under FERC's current regulatory regime, transmission services must be provided on an open-access, non-discriminatory basis at cost-based rates or at market-based rates if the transportation market at issue is sufficiently competitive. Gathering service, which occurs upstream of jurisdictional transmission services, is regulated by the states onshore and in state waters. Although its policy is still in flux, FERC has in the past reclassified certain jurisdictional transmission facilities as non-jurisdictional gathering facilities, which has the tendency to increase our costs of transporting gas to point-of-sale locations.

        Oil Sales and Transportation.    Sales of crude oil, condensate and NGLs are not currently regulated and are made at negotiated prices. Nevertheless, Congress could reenact price controls in the future.

        Our crude oil sales are affected by the availability, terms and cost of transportation. The transportation of oil in common carrier pipelines is also subject to rate regulation. FERC regulates interstate oil pipeline transportation rates under the Interstate Commerce Act and intrastate oil pipeline transportation rates are subject to regulation by state regulatory commissions. The basis for intrastate oil pipeline regulation, and the degree of regulatory oversight and scrutiny given to intrastate oil pipeline rates, varies from state to state. Insofar as effective interstate and intrastate rates are equally applicable to all comparable shippers, we believe that the regulation of oil transportation rates will not affect our operations in any materially different way than such regulation will affect the operations of our competitors.

        Further, interstate and intrastate common carrier oil pipelines must provide service on a non-discriminatory basis. Under this open access standard, common carriers must offer service to all shippers requesting service on the same terms and under the same rates. When oil pipelines operate at full capacity, access is governed by prorationing provisions set forth in the pipelines' published tariffs. Accordingly, we believe that access to oil pipeline transportation services generally will be available to us to the same extent as to our competitors.

        State Regulation.    Texas regulates the drilling for, and the production, gathering and sale of, oil and natural gas, including imposing severance taxes and requirements for obtaining drilling permits. Texas imposes a 4.6% severance tax on oil production and a 7.5% severance tax on natural gas production. States also regulate the method of developing new fields, the spacing and operation of wells and the prevention of waste of natural gas resources. States may regulate rates of production and may establish maximum daily production allowables from natural gas wells based on market demand or resource conservation, or both. States do not regulate wellhead prices or engage in other similar direct economic regulation, but we cannot assure you that they will not do so in the future. The effect of these regulations may be to limit the amount of natural gas that may be produced from our wells and to limit the number of wells or locations we can drill.

        The petroleum industry is also subject to compliance with various other federal, state and local regulations and laws. Some of those laws relate to resource conservation and equal employment

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opportunity. We do not believe that compliance with these laws will have a material adverse effect on us.

Operational Hazards and Insurance

        The oil and natural gas industry involves a variety of operating risks, including the risk of fire, explosions, blow outs, pipe failures and, in some cases, abnormally high pressure formations which could lead to environmental hazards such as oil spills, natural gas leaks and the discharge of toxic gases. If any of these should occur, we could incur legal defense costs and could be required to pay amounts due to injury, loss of life, damage or destruction to property, natural resources and equipment, pollution or environmental damage, regulatory investigation and penalties and suspension of operations.

        In accordance with what we believe to be industry practice, we maintain insurance against some, but not all, of the operating risks to which our business is exposed. We have insurance policies for property (including leased oil and natural gas properties), general liability, operational control of certain wells, pollution, commercial auto, umbrella liability, inland marine, workers' compensation and other coverage. The limits for certain of our policies are as follows:

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oil and natural gas lease property/inland marine: $790,370 on owned equipment, $100,000 per item/occurrence on rented or leased equipment, with a deductible of $2,500;

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general liability: $1,000,000 per occurrence and $2,000,000 in the aggregate with no deductible (this coverage includes sudden and accidental pollution);

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umbrella liability: $25,000,000 per occurrence with $25,000,000 aggregate coverage; and

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control of well: $10,000,000 with a deductible per accident ranging from $75,000 to $150,000 based on feet in depth.

        As noted above, most of our insurance coverage includes deductibles that must be met prior to recovery. Additionally, our insurance is subject to exclusion and limitations, and there is no assurance that such coverage will fully or adequately protect us against liability from all potential consequences, damages and losses. Any of these operational hazards could cause a significant disruption to our business. A loss not fully covered by insurance could have a material adverse effect on our financial condition, results of operations and cash flows.

        We reevaluate the purchase of insurance, policy terms and limits annually. Future insurance coverage for our industry could increase in cost and may include higher deductibles or retentions. In addition, some forms of insurance may become unavailable in the future or unavailable on terms that we believe are economically acceptable. No assurance can be given that we will be able to maintain insurance in the future at rates that we consider reasonable and we may elect to maintain minimal or no insurance coverage. We may not be able to secure additional insurance or bonding that might be required by new governmental regulations. This may cause us to restrict our operations, which might severely impact our financial condition. The occurrence of a significant event, not fully insured against, could have a material adverse effect on our financial condition and results of operations.

        Generally, we also require our third party vendors to sign master service agreements in which they agree to indemnify us for injuries and deaths of the service provider's employees as well as contractors and subcontractors hired by the service provider.

Employees

        As of May 31, 2013, we had 57 full time employees, including four geologists, 11 engineers and eight land professionals, 43 of whom are salaried administrative or supervisory employees. Of these 57 full time employees, 31 work in our corporate headquarters. None of our employees are represented by labor unions or covered by any collective bargaining agreements. We also hire independent contractors

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and consultants involved in land, technical, regulatory and other disciplines to assist our full time employees. We consider our relations with our employees to be satisfactory.

Facilities

        Our corporate headquarters is located in Fort Worth, Texas. We also lease additional office space in Midland, Texas. We believe that our facilities are adequate for our current operations.

Legal Proceedings

        From time to time, we are a party to ongoing legal proceedings in the ordinary course of business, including workers' compensation claims and employment related disputes. We do not believe the results of these proceedings, individually or in the aggregate, will have a material adverse effect on our business, financial condition, results of operations or liquidity.

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MANAGEMENT

Directors and Executive Officers

        The following sets forth information regarding our directors and officers:

Name	Age		Position with Athlon
Robert C. Reeves		43	President, Chief Executive Officer and Director
Nelson K. Treadway		48	Senior Vice President—Business Development and Land
William B. D. Butler		36	Vice President and Chief Financial Officer
Melvyn E. Foster		44	Vice President—Reservoir Engineering
Bud W. Holmes		46	Vice President—Engineering and Operations
David B. McClelland		42	Vice President—Drilling and Geosciences
Jennifer L. Palko		39	Vice President—Business Development and Engineering
James R. Plemons		45	Vice President—Business Development and Land
John C. Souders		42	Vice President—Controller
Gregory A. Beard		41	Director
Sam Oh		42	Director
Rakesh Wilson		38	Director
Ted A. Gardner		55	Director Nominee

        Robert C. Reeves—President, Chief Executive Officer and Director.    Mr. Reeves has been Athlon's President and Chief Executive Officer since its formation in August 2010. Prior to Athlon's formation, Mr. Reeves was Senior Vice President, Chief Financial Officer and Treasurer of Encore Energy Partners GP LLC, the general partner of Encore Energy Partners LP, from February 2007 until March 2010, and Corporate Secretary from May 2008 to August 2010. Mr. Reeves was also the Senior Vice President, Chief Financial Officer and Treasurer of Encore Acquisition Company ("EAC") from November 2006 until March 2010, and Corporate Secretary from May 2008 to August 2010. Mr. Reeves served as Senior Vice President, Chief Accounting Officer, Controller and Assistant Corporate Secretary of EAC from November 2005 until November 2006. He served as EAC's Vice President, Controller and Assistant Corporate Secretary from August 2000 until October 2005. He served as Assistant Controller of EAC from April 1999 until August 2000. Prior to joining EAC, Mr. Reeves served as Assistant Controller for Hugoton Energy Corporation. Mr. Reeves received his Bachelor of Science degree in Accounting from the University of Kansas. He is a Certified Public Accountant. Based upon Mr. Reeves' extensive background in operations and management, having served in various high-level executive roles, as well as his strong financial background and his experience with Athlon, which provide him with a unique understanding of our business and the operational, financial and strategic issues that energy companies face, we believe that Mr. Reeves possesses the requisite set of skills to serve as a member of our Board of Directors.

        Nelson K. Treadway—Senior Vice President—Business Development and Land.    Mr. Treadway has been Athlon's Senior Vice President—Business Development and Land since its formation in August 2010. Prior to Athlon's formation, Mr. Treadway served as Senior Vice President—Land of Encore Energy Partners GP LLC and EAC from February 2008 to March 2010. Mr. Treadway served as Vice President—Land of EAC from April 2003 to February 2008. He served as a Vice President—Land at Encore Energy Partners GP LLC from February 2007 to February 2008. From May 2000 to April 2003, Mr. Treadway held various positions of increasing responsibility in EAC's land department. Prior to EAC, he served as a landman at Coho Resources. Mr. Treadway received a Bachelor of Science degree in Petroleum Land Management from the University of Southwestern Louisiana.

        William B. D. Butler—Vice President and Chief Financial Officer.    Mr. Butler has been Athlon's Vice President and Chief Financial Officer since March 2013. Prior to joining Athlon, Mr. Butler served as Managing Director for Stephens Inc. from August 2010 to March 2013, where he developed and led its

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Exploration & Production research practice. Previously, he was Vice President and Assistant Treasurer of XTO Energy Inc. from June 2003 until June 2010. During his seven-year tenure, XTO completed 21 capital raises, including public equity, senior notes and bank debt, for more than $15 billion in aggregate proceeds to fund XTO's growth strategy. From June 2000 to June 2003, Mr. Butler served at Stephens Inc. as an investment banker. Mr. Butler received a Bachelor of Science degree in Commerce from Washington & Lee University with special attainments in Business Administration and History.

        Melvyn E. Foster—Vice President—Reservoir Engineering.    Mr. Foster has been Athlon's Vice President—Reservoir Engineering since its formation in August 2010. Prior to Athlon's formation, Mr. Foster was Reservoir Engineering Manager—North Region of Denbury Resources, Inc. from April 2010 to August 2010. Mr. Foster was Northern Region Reservoir Engineering Manager of EAC from December 2007 to April 2010. From April 2002 to December 2007, Mr. Foster held various positions of increasing responsibility in EAC's engineering department. Prior to EAC, he served in various engineering positions at Phillips Petroleum Company. Mr. Foster received his Bachelor of Science degree in Petroleum Engineering from the University of Texas at Austin and his Master of Science degree in Petroleum Engineering from the University of Houston.

        Bud W. Holmes—Vice President—Engineering and Operations.    Mr. Holmes has been Athlon's Vice President—Engineering and Operations since its formation in August 2010. Prior to Athlon's formation, Mr. Holmes served as Northern Region Production Manager and member of the Strategic Management Team of EAC from October 2003 until March 2010. Mr. Holmes served as Northern Region Senior Operations Engineer from April 2001 until October 2003. Prior to joining EAC, Mr. Holmes served in various reservoir, production and drilling engineering positions for Louis Dreyfus Natural Gas, Union Pacific Resources and Shell Western E&P. Mr. Holmes received his Bachelor of Science degree in Petroleum Engineering from the University of Oklahoma, graduating with top honors.

        David B. McClelland—Vice President—Drilling and Geosciences.    Mr. McClelland has been Athlon's Vice President—Drilling and Geosciences since its formation in August 2010. Prior to Athlon's formation, Mr. McClelland was the Geoscience Manager—Southern Region for EAC, from February 2007 to June 2010, and he was a Senior Geologist from March 2004 to January 2007 at EAC. Prior to EAC, he was a Geologist at Anadarko Petroleum Company and held various geosciences positions at Union Pacific Resources and Cross Timbers Oil Company. Mr. McClelland received his Bachelor of Science degree in Geology from the University of Texas at Arlington. He also received his Master of Science degree in Geology from the University of Texas at Arlington. Mr. McClelland is a licensed professional geoscientist in the State of Texas, and is a 16 year member of the American Association of Petroleum Geologists.

        Jennifer L. Palko—Vice President—Business Development and Engineering.    Ms. Palko has been Athlon's Vice President—Business Development and Engineering since its formation in August 2010. Prior to Athlon's formation, Ms. Palko served as the Reserves & Planning Engineering Manager and a member of the Strategic Management Team of EAC from October 2003 until March 2010. Prior to serving as the Reserves & Planning Engineering Manager, Ms. Palko held various positions of increasing responsibility in EAC's engineering department from May 2001 until October 2003. Prior to joining EAC, Ms. Palko served as an Independent Petroleum Consultant at Cawley, Gillespie & Associates, Inc. from September 2000 until May 2001. Prior to joining Cawley, Gillespie & Associates, Inc., Ms. Palko served in various reservoir and operations engineering positions at Union Pacific Resources from May 1995 until September 2000. Ms. Palko received her Bachelor of Science degree in Petroleum Engineering from Texas A&M University, graduating first in her class with top honors.

        James R. Plemons—Vice President—Business Development and Land.    Mr. Plemons has been Athlon's Vice President—Business Development and Land since its formation in August 2010. Prior to the Partnership's formation, Mr. Plemons served as the Southern Region Land Manager of Encore Energy Partners GP LLC and EAC from January 2007 to June 2010. Prior to serving as Southern

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Region Land Manager, Mr. Plemons served in several roles with increasing responsibility in EAC's land department from June 2004 to December 2006. Prior to EAC, he served as a landman at Wagner Oil Company. Mr. Plemons received a Bachelor of Science degree in Marketing from Sam Houston State University.

        John C. Souders—Vice President—Controller.    Mr. Souders has been Athlon's Vice President—Controller since July 2011 and was Director of Accounting from March 2011 until his promotion in July 2011. Prior to Athlon's formation, Mr. Souders served as a Senior Accounting Manager at EAC from May 2007 until February 2011. Prior to EAC, Mr. Souders served as an Accounting Manager at Sabre Holdings and as an auditor at Ernst & Young. Mr. Souders has a Bachelor of Science degree in Economics from Texas A&M University and a Masters in Accounting from North Texas University. He is a Certified Public Accountant.

        Gregory A. Beard—Director.    Mr. Beard is currently a Senior Partner at Apollo. Mr. Beard joined the firm in June 2010 as the Global Head of Natural Resources, based in the New York office. Mr. Beard joined Apollo with 19 years of investment experience, the last ten of which were with Riverstone Holdings where he was a founding member, Managing Director and lead deal partner in many of the firm's top oil and natural gas and energy service investments. While at Riverstone, Mr. Beard was involved in all aspects of the investment process including sourcing, structuring, monitoring and exiting transactions. Mr. Beard began his career as a Financial Analyst at Goldman Sachs, where he played an active role in that firm's energy-sector principal investment activities. Mr. Beard has served on the board of directors of many oil and natural gas companies including Apex Energy, EP Energy, Belden & Blake Corporation, Canera Resources, Cobalt International Energy, Eagle Energy, Legend Natural Gas I—IV, Mariner Energy, Phoenix Exploration, Titan Operating, Talos Energy, Pinnacle Agriculture Holdings, LLC, NRI Management Group, LLC and Vantage Energy. Mr. Beard has also served on the board of directors of various oilfield services companies, including CDM Max, CDM Resource Management and International Logging. Mr. Beard received his Bachelor of Arts degree from the University of Illinois at Urbana. Based upon Mr. Beard's extensive investment and management experience, particularly in the energy sector, his strong financial background and his service on the boards of multiple oil and natural gas exploration and production companies and oilfield services companies, which have provided him with a deep working knowledge of our operating environment, we believe that he possesses the requisite skills to serve as a member of our Board of Directors.

        Sam Oh—Director.    Mr. Oh is currently a Senior Partner at Apollo. Mr. Oh joined the firm in April 2008 and is one of the original founding members of Apollo's Natural Resources group. Prior to joining Apollo, Mr. Oh was with Morgan Stanley's Commodities Department where he led principal investments for the group. While at Morgan Stanley, Mr. Oh launched a successful oil and natural gas fund, Helios Energy/Royalty Partners, and sat on the board of several portfolio companies. Mr. Oh has 18 years of experience, including 13 years of principal investing. He also has a broad range of experience in the commodities markets including risk management and structured products. Since joining Apollo, Mr. Oh has been actively involved in Apollo's E&P investments, including leading the Parallel Petroleum acquisition in 2009. Mr. Oh was formerly Chairman of the Board of Parallel Petroleum and is a director of EP Energy. Mr. Oh received a Bachelor of Science degree from the University of Pennsylvania's Wharton School of Business and an MBA from the Yale School of Management. He is also a Certified Public Accountant and a Chartered Financial Analyst. Based upon Mr. Oh's strong management experience and extensive background in commodities markets having overseen various complex commodities investments, as well as his experience with Athlon and his service on multiple boards of directors, we believe that Mr. Oh possesses the requisite set of skills to serve as a member of our Board of Directors.

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        Rakesh Wilson—Director.    Mr. Wilson is currently a Principal at Apollo. Mr. Wilson joined the firm in March 2009, where he is currently a senior member of Apollo's Natural Resources group. Prior to joining Apollo, Mr. Wilson was at Morgan Stanley's Commodities Department in the principal investing group responsible for generating, evaluating and executing investment ideas across the energy sector with deals including Wellbore Capital and Helios Energy/Royalty Partners. Mr. Wilson began his career at Goldman Sachs in equity research and then moved to its investment banking division in New York and Asia. Mr. Wilson currently serves on the boards of directors of EP Energy and Talos Energy and previously served as a director of Parallel Petroleum. Mr. Wilson graduated from the University of Texas at Austin and received his MBA from INSEAD, Fontainebleau, France. He has also taught business courses at universities in China. We believe that Mr. Wilson's extensive international investment and risk management experience, his knowledge of Athlon and his service on multiple boards have provided him with a strong understanding of the financial, operational and strategic issues facing public companies in our industry, and that he possesses the requisite set of skills to serve as a member of our Board of Directors.

        Ted A. Gardner—Director Nominee.    Mr. Gardner has agreed to serve as a director of Athlon and will become a member of the board of directors prior to the listing of our common stock on the NYSE. Mr. Gardner has been a Managing Partner of Silverhawk Capital Partners in Charlotte, North Carolina since 2005. Mr. Gardner is also currently a director of Summit Materials Holdings, Spartan Energy Partners, Kinder Morgan Management, LLC and Kinder Morgan G.P., Inc. Formerly, he was a director and Chairman of the Compensation Committee of Kinder Morgan, Inc. from 1999 to 2007 and was a director and Chairman of the Audit Committee of Encore Acquisition Company from 2001 to 2010. Mr. Gardner also served as Managing Partner of Wachovia Capital Partners and was a Senior Vice President of Wachovia Corporation from 1990 to June 2003. Based upon his prior management, business and leadership experience, as well as his previous board experience with other publicly-held companies in the energy sector, we believe that Mr. Gardner possesses the requisite set of skills to serve as a member of our Board of Directors.

Composition of Our Board of Directors

        Upon the closing of this offering, it is anticipated that we will have five directors. Assuming the Apollo Funds continue to control more than 50% of our common stock, we intend to avail ourselves of the "controlled company" exception under NYSE rules, which eliminates the requirements that we have a majority of independent directors on our Board of Directors and that we have a compensation committee and a nominating and corporate governance committee, each composed entirely of independent directors. We will be required, however, to have an audit committee comprised entirely of independent directors within the permitted "phase-in" period under NYSE rules.

        The stockholders agreement that we will enter into in connection with this offering will provide that, except as otherwise required by applicable law, if the Apollo Funds hold: (a) at least 50% of our outstanding common stock, they will have the right to designate no fewer than that number of directors that would constitute a majority of our Board of Directors; (b) at least 30% but less than 50% of our outstanding common stock, they will have the right to designate up to three director nominees; (c) at least 20% but less than 30% of our outstanding common stock, they will have the right to designate up to two director nominees; and (d) at least 10% but less than 20% of our outstanding common stock, they will have the right to designate up to one director nominee. The agreement also provides that if the size of our Board of Directors is increased or decreased at any time to other than seven directors, the Apollo Funds' nomination rights will be proportionately increased or decreased, respectively, rounded up to the nearest whole number. In addition, the agreement provides that if the Apollo Funds hold at least 30% of our outstanding common stock, we will cause any committee of our Board of Directors to include in its membership at least one of the Apollo Funds nominees, except to the extent that such membership would violate applicable securities laws or stock exchange or stock market rules.

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As a result of the size of their ownership of our common stock, the Apollo Funds will be able to control matters requiring stockholder approval, including the election of directors, changes to our organizational documents and significant corporate transactions.

        If at any time we cease to be a "controlled company" under NYSE rules (including upon completion of this offering and the related transactions), the Board of Directors will take all action necessary to comply with the NYSE rules, including appointing a majority of independent directors to the Board of Directors and ensuring we have a compensation committee and a nominating and corporate governance committee, each composed entirely of independent directors, subject to a permitted "phase-in" period. We will cease to qualify as a "controlled company" once the Apollo Funds cease to control a majority of our voting stock.

        Following the closing of this offering, our Board of Directors will be divided into three classes. The members of each class will serve staggered, three-year terms (other than with respect to the initial terms of the Class I and Class II directors, which will be one and two years, respectively). Upon the expiration of the term of a class of directors, directors in that class will be elected for three-year terms at the annual meeting of stockholders in the year in which their term expires. Following the completion of this offering:

•

Sam Oh and Rakesh Wilson will be Class I directors, whose initial terms will expire at the 2014 annual meeting of stockholders;

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Ted A. Gardner and Robert C. Reeves will be Class II directors, whose initial terms will expire at the 2015 annual meeting of stockholders; and

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Gregory A. Beard will be a Class III director, whose initial term will expire at the 2016 annual meeting of stockholders.

        Any additional directorships resulting from an increase in the number of directors will be distributed among the three classes so that, as nearly as possible, each class will consist of one-third of our directors. This classification of our Board of Directors may have the effect of delaying or preventing changes in control.

        At each annual meeting following completion of this offering, our stockholders will elect certain of our directors. Our executive officers and key employees serve at the discretion of our Board of Directors. Directors may be removed for cause by the affirmative vote of the holders of a majority of our common stock so long as at least 33¹/3% of the voting power of all our shares is owned by the Apollo Funds and the Apollo Funds cast their votes in favor of the proposed action. At any other time, directors may be removed for cause only by the affirmative vote of at least 66²/3% of the voting power of our common stock.

Apollo Approval of Certain Matters

        Under the stockholders agreement that we have agreed to enter into with the Apollo Funds and certain stockholders upon consummation of this offering, until such time as the Apollo Funds no longer beneficially own at least 33¹/3% of our outstanding common stock, a majority of the Board of Directors, including a majority of the directors designated to our Board of Directors by the Apollo Funds, must approve certain of our significant business decisions before we are permitted to take action, including each of the following:

•

amending, modifying or repealing any provision of our certificate of incorporation and bylaws or similar organization documents in a manner that adversely affects the Apollo Funds or their affiliates;

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•

issuing additional equity interests other than any (i) award under any stockholder-approved equity compensation plan, (ii) intra-company issuance among our subsidiaries and us or (iii) issuance of equity interests pursuant to the exchange agreement;

•

consolidating or merging with or into any other entity, transferring all or substantially all of our and our subsidiaries' assets, taken as a whole, to another entity or entering into or agreeing to undertake any transaction that would constitute a "Change of Control" as defined in our credit agreement or the indenture governing our senior notes;

•

disposing of any of our or any of our subsidiaries' assets with a value in excess of $100 million in any single transaction or $200 million in the aggregate in any series of transactions during a calendar year;

•

consummating any acquisition by us or any of our subsidiaries of the equity interests or assets of any other entity involving consideration in excess of $100 million in any single transaction or $200 million in the aggregate in any series of transactions during a calendar year;

•

incurring any indebtedness by us or any of our subsidiaries (including through capital leases, the issuance of debt securities or the guarantee of indebtedness of another entity) that would result in our total net indebtedness to adjusted EBITDA for the trailing twelve-month period exceeding 2.50 to 1.0;

•

terminating our Chief Executive Officer or designating a new Chief Executive Officer; and

•

changing the size of our Board of Directors.

        Please read "—Composition of Our Board of Directors" for a description of the Apollo Funds' rights to nominate a certain number of directors.

Director Independence

        Our Board of Directors has determined that, under NYSE listing standards and taking into account any applicable committee standards and rules under the Exchange Act, Mr. Gardner is an independent director. Within 90 days of our listing on the NYSE, we will appoint at least one additional independent director. Within one year of the date of effectiveness of the registration statement, we will appoint a third independent director. Mr. Reeves is not considered independent under any general listing standards due to his current employment relationship with us, and Messrs. Beard, Oh and Wilson, are not considered independent under any general listing standards due to their relationship with the Apollo Funds, our largest stockholder.

Committees of the Board of Directors

        Prior to the listing of our common stock on the NYSE, we intend to have an Audit Committee, a Compensation Committee and a Nominating and Corporate Governance Committee, and may have such other committees as the Board of Directors shall determine from time to time. Each of the standing committees of the Board of Directors will have the composition and responsibilities described below.

Audit Committee

        Mr. Gardner will serve as the initial member of our Audit Committee. Within 90 days of our listing on the NYSE we will appoint another independent director to our Audit Committee. Our Board of Directors has determined that Mr. Gardner is an Audit Committee financial expert as defined by the SEC. Each member of the Audit Committee meets or will meet criteria for independence of Audit Committee members set forth in Rule 10A-3(b)(1) under the Exchange Act.

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        The principal duties of the Audit Committee are to assist the Board of Directors in fulfilling its responsibility to oversee management regarding:

•

systems of internal control over financial reporting and disclosure controls and procedures;

•

the integrity of the financial statements;

•

the qualifications, engagement, compensation, independence and performance of the independent auditors and our internal audit function;

•

compliance with legal and regulatory requirements;

•

review of material related party transactions; and

•

compliance with and adequacy of the code of business and ethics, review and, if appropriate, approve any requests for written waivers sought with respect to any executive officer or director under, the code of business and ethics.

Compensation Committee

        Robert C. Reeves, Gregory A. Beard, Sam Oh, Rakesh Wilson and Ted A. Gardner will serve as the initial members of our Compensation Committee. The principal duties of the Compensation Committee are to:

•

oversee our management compensation policies and practices, including, without limitation, (i) determining and approving the compensation of the Chief Executive Officer and our other executive officers, (ii) reviewing and approving management incentive policies and programs and exercising any applicable rule making or discretion in the administration of such programs, (iii) reviewing and approving equity compensation programs for employees, and exercising any applicable rule making or discretion in the administration of such programs and (iv) reviewing and approving any share ownership and clawback policies applicable to the senior management group or other employees;

•

set and review the compensation of and reimbursement and share ownership policies for members of our Board of Directors;

•

provide oversight concerning the selection of officers, expense accounts and severance plans and policies and compliance with all compensation and benefits-related legal and regulatory matters;

•

review and discuss with management our compensation discussion and analysis to be included in our annual proxy statement or annual report on Form 10-K filed with the SEC; and

•

prepare an annual Compensation Committee report, provide regular reports to our Board of Directors, and take such other actions as are necessary and consistent with the governing law and our organizational documents.

Nominating and Corporate Governance Committee

        Gregory A. Beard, Sam Oh and Rakesh Wilson will serve as the initial members of our Nominating and Corporate Governance Committee. The principal duties and responsibilities of our Nominating and Corporate Governance Committee will be the following:

•

implementation and review of criteria for membership on our Board of Directors and its committees;

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identification and recommendation of proposed nominees for election to our Board of Directors and membership on its committees;

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•

development of and recommendation to our Board of Directors regarding governance and related matters; and

•

overseeing the evaluation of our Board of Directors.

Code of Ethics

        Our Board of Directors has adopted a code of business conduct and ethics (the "Code of Conduct") that applies to all directors, officers and employees, including our principal executive officer, principal financial officer and principal accounting officer. Upon the closing of this offering, the Code of Conduct will be available in the Corporate Governance section of our website at www.athlonenergy.com. The contents of our website are not incorporated by reference herein or otherwise a part of this prospectus. The purpose of the Code of Conduct is to promote honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships; to promote full, fair, accurate, timely and understandable disclosure in periodic reports required to be filed by us; and to promote compliance with all applicable rules and regulations that apply to us and our officers.

Corporate Governance Guidelines

        Our Board of Directors will adopt corporate governance guidelines in accordance with the corporate governance rules of the NYSE.

Executive Compensation

        This executive compensation disclosure provides an overview of the 2012 executive compensation program for our named executive officers ("NEOs") identified below. For 2012, our NEOs were:

•

Robert C. Reeves, President, Chief Executive Officer and Director;

•

Nelson K. Treadway, Senior Vice President—Business Development and Land; and

•

David B. McClelland, Vice President—Drilling and Geosciences.

Summary Compensation Table

        The following summarizes the total compensation awarded to, earned by or paid to our NEOs for 2012:

Name and Principal Position	Year		Salary ($)		Non-Equity Incentive Plan Compensation ($)1		All Other Compensation ($)2		Total ($)
Robert C. Reeves, President, Chief Executive Officer and Director		2012	$	374,583	$	385,000	$	26,539	$	786,122
Nelson K. Treadway, Senior Vice President—Business Development and Land		2012		279,375		206,225		22,401		508,001
David B. McClelland, Vice President—Drilling and Geosciences		2012		219,792		117,150		20,865		357,807

¹

Represents cash bonuses paid to our NEOs under our incentive program with respect to 2012 company and individual performance. For additional information, please read "—Narrative Disclosure to Summary Compensation Table—Cash Bonuses" below.

²

Represents employer contributions under our 401(k) plan.

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Narrative Disclosure to Summary Compensation Table

        The primary elements of compensation for the NEOs are base salary, cash bonuses and long-term equity-based compensation awards. The NEOs also receive certain retirement, health, welfare and additional benefits as described below.

Compensation Element	Characteristics	Primary Objective
Base salary	Fixed annual cash compensation. Salaries may be increased from time to time based on the NEOs' responsibilities and performance.	Recognize performance of job responsibilities and attract and retain talented employees.
Cash bonuses	Performance-based semi-annual cash incentive.	Encourage focus on near-term performance goals and reward achievement of those goals.
Long-term equity incentives	Equity-based compensation awards subject to time-vesting provisions.	Emphasize our long-term growth, encourage maximizing equity value and retain talented employees.
Severance provisions	Salary continuation and COBRA reimbursement upon certain qualifying terminations.	Encourage continued attention and dedication of key individuals and focus their attention when considering strategic alternatives.
Retirement savings 401(k) plan	Qualified 401(k) retirement plan benefits are available for our NEOs and all other full-time employees.	Provide an opportunity for tax-efficient savings.
Health and welfare benefits	Health and welfare benefits are available to our NEOs and other full-time employees.	Provide benefits to meet the health and welfare needs of our employees and their families.

        Base Salary.    Base salaries for our NEOs have generally been set at levels deemed necessary to attract and retain individuals with superior talent. While the Board will review and may adjust each NEO's salary from time to time, Messrs. Treadway's and McClelland's employment agreements provide that their respective salary will not be reduced for two years after the effective date of his agreement and Mr. Reeves' employment agreement provides that his base salary will never be reduced.

        In September 2012, the Board approved salary increases for our NEOs based upon the responsibilities and performance of each NEO as well as market conditions. Our NEOs' base salaries will also be increased upon the closing of this offering to better align total compensation with

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competitive pay levels for similarly situated public companies. The base salaries of our NEOs before and after the 2012 increase and after the offering are set forth in the following table:

Name and Principal Position	Base Salary Before 2012 Increase		Base Salary After 2012 Increase		Base Salary After the Offering
Robert C. Reeves	$	360,000	$	410,000	$	570,000
Nelson K. Treadway		275,000		290,000		300,000
David B. McClelland1		215,000		240,000		275,000

¹

Mr. McClelland received an additional salary adjustment in April 2012 that increased his base salary from $205,000 to $215,000.

        Cash Bonuses.    Each of our NEOs is eligible to participate in a semi-annual cash incentive program which provides participants with an opportunity to earn cash bonus awards generally based on individual and company performance. Target bonus levels for each of our NEOs other than Mr. Reeves are established by the Board of Directors at the beginning of each year, subject to mid-year adjustment, and are based on a percentage of their respective base salary. Mr. Reeves' target bonus level of 100% is set forth in his employment agreement and was established based upon individual negotiations at the time of his commencement of employment. For 2012, Mr. Treadway had a target bonus level of 73%. Mr. McClelland had a target bonus level of 43% for the first half of 2012 and 60% for the second half of 2012. Upon the closing of this offering, Mr. Treadway's and Mr. McClelland's target bonus levels will be adjusted to 80% and 70% of their annual base salaries, respectively.

        Historically, including for 2012, with respect to assessment of company performance, the bonus awards for our NEOs have not been based on specific pre-determined performance targets or goals. Rather, we have generally considered our overall operational performance for the applicable year as a guide in determining award payout levels and have maintained discretion to adjust awards in circumstances where individual performance may warrant such an adjustment. For 2012, we determined to pay bonuses to each of our NEOs 100% of their respective target bonus levels and did not make any individual performance adjustments to these awards. Our decision in this regard was based primarily on generally attaining budgeted levels for the year with respect to certain operational performance metrics, which included rate of return on drilling capital, our net asset value, drilling costs per well, production volumes and LOE per BOE. We focused on operating metrics of this type in determining cash bonus awards for our NEOs, rather than on financial metrics such as revenue or net income because such financial metrics are influenced by commodity prices, which can fluctuate based on macro-economic factors that are beyond the control of our NEOs.

        Long-Term Equity-Based Compensation Awards.    None of our NEOs received awards or grants of equity or equity-based compensation during 2012. However, in August 2010, each of our NEOs was granted Class B limited partner interests of Athlon Holdings LP pursuant to the Athlon Holdings LP Limited Partnership Agreement. The Class B limited partner interests were intended to align the interests of our NEOs with those of our equity sponsor and provide a retention incentive for our NEOs.

        The Class B limited partner interests are profits interests that were intended to allow our NEOs to participate in the increase in value of Athlon Holdings LP from and after the date of grant of such interests. Class B limited partner interests are subject to time-vesting provisions. Mr. Reeves' Class B limited partner interests were scheduled to vest in equal monthly installments over a four-year period, beginning on the last date of the month of the grant date. Messrs. Treadway's and McClelland's Class B limited partner interests were scheduled to vest in equal semi-annual installments over a five-year period, beginning on the six-month anniversary of the grant date. Please read "—Severance and Change in Control Provisions" for a description of the other circumstances under which vesting of

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these awards may have accelerated. In connection with the reorganization as described under "Corporate Reorganization," all of the Class B limited partner interests held by our NEOs and certain other employees were converted into shares of our common stock. For information regarding the number of our shares of common stock beneficially owned by each of our NEOs immediately following the consummation of this offering, please read "Principal and Selling Stockholders."

        In connection with this offering, we intend to adopt the Athlon Energy Inc. 2013 Incentive Award Plan, under which we expect to make periodic grants of equity and equity-based awards to our NEOs and other key employees, including awards expected to be granted shortly after the closing of this offering. For additional information, please read "—Executive Compensation Plans—2013 Incentive Award Plan."

        Retirement, Health, Welfare and Additional Benefits.    The NEOs are eligible to participate in such employee benefit plans and programs as we may from time to time offer to our other full-time employees, subject to the terms and eligibility requirements of those plans. The NEOs are also eligible to participate in a tax-qualified 401(k) defined contribution plan to the same extent as all of our other full-time employees. For 2012, we made a fully vested safe harbor non-elective contribution on behalf of each of the plan's participants equal to 3% of that participant's salary for the year.

Outstanding Equity Awards at December 31, 2012

        The outstanding Class B limited partner interests in Athlon Holdings LP held by our NEOs as of December 31, 2012 were as follows:

	Equity Awards
Name	Number of Class B Limited Partner Interests that Have not Vested (#)1			Market Value of Class B Limited Partner Interests That Have Not Vested ($)4
Robert C. Reeves		15,833	2	$	1,481,177
Nelson K. Treadway		7,200	3		673,560
David B. McClelland		3,150	3		294,683

¹

As discussed above under "—Summary Compensation Table—Narrative Disclosure to Summary Compensation Table—Long-Term Equity-Based Compensation Awards," the Class B limited partner interests were converted in anticipation of this offering into shares of our common stock.

²

Unvested Class B limited partner interests were scheduled to vest in equal monthly installments through the fourth anniversary of the date of grant in August 2010.

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Unvested Class B limited partner interests were scheduled to vest in equal semi-annual installments through the fifth anniversary of the date of grant in August 2010.

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Amount shown represents an estimate of fair market value of the unvested Class B limited partner interests as of December 31, 2012 of $93.55 per interest, as determined by an independent third-party valuation expert.

Employment Agreements

        We entered into an employment agreement with Mr. Reeves on August 23, 2010 for a term of three years, subject to automatic renewal for a one-year period, and with Messrs. Treadway and McClelland on August 23, 2010, each for a term of two years, subject to automatic renewal for a one-year period. In addition, in connection with the consummation of this offering, we are entering into new employment agreements with each of our NEOs. These agreements will provide for a similar initial term as the prior agreements and, as revised, contain (i) compensation provisions, including provisions regarding base salary, cash incentive bonuses and other benefits, (ii) termination and

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severance provisions (discussed more in detail below) and (iii) noncompete, nonsolicit and nondisclosure provisions, with a restriction period of one year for the noncompete and nonsolicit provisions.

Severance and Change in Control Provisions

        Mr. Reeves' Severance and Change in Control Benefits.    Mr. Reeves' new employment agreement provides that if we terminate Mr. Reeves' employment for cause, he resigns without good reason or he does not extend his term of employment, then he is entitled to receive: (i) the portion of his base salary earned through the date of termination but not yet paid, plus any accrued vacation earned but not used through the date of termination; (ii) any cash incentive bonus earned but not yet paid; (iii) any expenses owed to him; and (iv) any amount accrued arising from his participation in, or benefits accrued under any employee benefits plans, programs or arrangements. Any rights to salary, cash bonus or other benefits will then cease.

        However, if Mr. Reeves is terminated without cause, resigns with good reason or we do not extend his term of employment and Mr. Reeves signs a release within 45 days, he is entitled, in addition to the items listed in the above paragraph, to (i) receive an amount of cash equal to four times the annual base salary in effect as of the date of termination payable 50% in a lump sum within 60 days following his separation from service and 50% over the subsequent twelve months, in accordance with regular payroll practices, and (ii) have us pay directly or reimburse him for COBRA premiums if he (or his dependents) elect to receive continued healthcare coverage pursuant to COBRA until the earlier of two years or the last day of the applicable COBRA period.

        In addition to the items listed in the paragraph above, if Mr. Reeves is terminated without cause, he resigns with good reason or we do not extend his term of employment, in any case within one year following the date of a change in control, then in lieu of the amount of cash listed above, he is entitled to receive an amount in cash equal to three times his annual base salary in effect as of the date of termination, plus three times the greater of the average of his previous two years' bonus payments or his target bonus.

        If Mr. Reeves is terminated due to death or disability and, in the case of disability, he signs a release within 45 days, he is additionally entitled to (i) receive an amount of cash equal to 25% of his base salary, payable in lump sum on the 60^th day following his separation from service and (ii) have us pay directly or reimburse him for COBRA premiums if he (or his dependents) elect to receive continued healthcare coverage pursuant to COBRA for three months.

        Good reason is defined in Mr. Reeves' employment agreement generally to mean the occurrence of any of the following events without his express written consent: (i) any reduction in his base salary; (ii) any material breach by us of the employment agreement; (iii) his duties or responsibilities for us or our successor are materially reduced or there is any material change in his title or any material change in the types of positions reporting to him or the type of position to whom he reports; or (iv) any transfer of his primary place of employment of more than 25 miles from 420 Throckmorton Street, Suite 1200, Fort Worth, Texas 76102, provided that such transfer increases his commute by more than 25 miles.

        In addition, Mr. Reeves' award agreement granting his Class B limited partner interests also contains certain termination and change in control provisions, under which all unvested Class B limited partner interests will fully vest upon (i) a change of control, winding up of Athlon Holdings LP's affairs, dissolution or liquidation of Athlon Holdings LP, (ii) a sale of all or substantially all of the assets of Athlon Holdings LP or (iii) the partners of Athlon Holdings LP receiving distributions from Athlon Holdings LP representing a return of their invested capital plus an 8% compounded annual return. If Mr. Reeves' employment is terminated for other than cause, due to death or disability or if

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he resigns for good reason, then half of his unvested Class B limited partner interests will vest upon his termination or resignation.

        Other NEOs' Severance and Change in Control Benefits.    Messrs. Treadway's and McClelland's new employment agreements provide that if either NEO's employment is terminated (i) for cause, due to death or disability, (ii) due to resignation without good reason or (iii) either party decides not to extend the term of employment, then each is entitled to (a) the portion of his base salary earned through the date of termination but not yet paid, plus any accrued vacation earned but not used through the date of termination, (b) any expenses owed to him and (c) any amount accrued arising from his participation in, or benefits accrued under any employee benefits plans, programs or arrangements. Any rights to salary, cash bonus or other benefits will then cease.

        However, if Messrs. Treadway or McClelland is terminated without cause or resigns for good reason and signs a release within 45 days, then each is entitled, in addition to the items listed in the above paragraph, to (i) receive an amount of cash equal to his annual base salary payable over the twelve-month period from his separation of service, in accordance with regular payroll practices, and (ii) have us pay directly or reimburse him for COBRA premiums if he (or his dependents) elect to receive continued healthcare coverage pursuant to COBRA until the earlier of twelve months, the date the covered dependents are no longer eligible or the date he becomes eligible to receive substantially comparable coverage from another employer.

        If either Messrs. Treadway or McClelland is terminated without cause or resigns for good reasons or we do not extend his term of employment, in either case within one year following the date of a change in control, then (i) in lieu of the amount of cash listed above, each is entitled to receive an amount in cash equal to two and a half times his annual base salary in effect as of the date of termination, plus two and a half times the greater of the average of his previous two years' bonus payments or his target bonus, and (ii) in lieu of the healthcare continuation listed above, we will continue to pay or reimburse his healthcare coverage pursuant to COBRA until the earlier of 18 months, the date the covered dependents are no longer eligible or the date he becomes eligible to receive substantially comparable coverage from another employer.

        Cause is defined in the employment agreements generally as the occurrence or existence of any of the following events: (i) the NEO's willful engagement in material mismanagement in providing services to us or our affiliates; (ii) the NEO's willful engagement in misconduct that he knew, based on facts known to him, could reasonably be expected to be materially injurious to us or our affiliates; (iii) the NEO's material breach of the employment agreement; (iv) the NEO's conviction of, or entrance into a plea bargain or settlement admitting guilt for, any felony, under the laws of the United States, any state or the District of Columbia; or (v) each NEO being the subject of any order, judicial or administrative, obtained or issued by the SEC, for any securities violation involving fraud. Good reason is defined in a similar manner to Mr. Reeves' employment agreement.

        Change in Control is defined to have the same meaning as in the Athlon Energy Inc. 2013 Incentive Award Plan, without regard to any amendments that may be adopted after the date of this offering.

        In addition, Messrs. Treadway's and McClelland's award agreements granting Class B limited partner interests also contain certain termination and change in control provisions, under which all unvested Class B limited partner interests will fully vest upon (i) a change of control, winding up of Athlon Holdings LP's affairs, dissolution or liquidation of Athlon Holdings LP, (ii) a sale of all or substantially all of the assets of Athlon Holdings LP or (iii) the partners of Athlon Holdings LP receiving distributions from Athlon Holdings LP representing a return of their invested capital plus an 8% compounded annual return.

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Executive Compensation Plans

        The following are summaries of the short-term and long-term incentive compensation plans in which our NEOs may participate following the closing of the offering.

2013 Incentive Award Plan

        Following the closing of this offering, we anticipate granting equity and equity-based compensation awards to our NEOs and other key employees on a periodic basis to align compensation with our performance. These awards will be granted under the Athlon Energy Inc. 2013 Incentive Award Plan that we intend to adopt prior to the closing of this offering and which will be effective no later than the day prior to the completion of this offering. The material terms of the Athlon Energy Inc. 2013 Incentive Award Plan, which we refer to as the Plan, are described in more detail below.

Purpose; Eligibility and Administration

        The principal purpose of the Plan will be to attract, retain and engage selected employees, consultants and directors through the granting of equity and equity-based compensation awards.

        Our and our subsidiaries' employees, consultants and directors, including our NEOs, will be eligible to receive awards under the Plan. The Compensation Committee will administer the Plan unless our Board of Directors assumes authority for administration. The Compensation Committee will be authorized to delegate its duties and responsibilities as plan administrator to subcommittees comprised of our directors and/or officers, subject to certain limitations. Our Board of Directors will administer the Plan with respect to awards to non-employee directors.

        Subject to the express terms and conditions of the Plan, the plan administrator will have the authority to make all determinations and interpretations under the plan, prescribe all forms for use with the plan and adopt, amend and/or rescind rules for the administration of the plan. The plan administrator will also set the terms and conditions of all awards under the plan, including any vesting and vesting acceleration conditions.

Limitation on Awards and Shares Available

        Initially, the aggregate number of our shares of common stock available for issuance pursuant to awards granted under the Plan will be the sum of 8,400,000 shares, subject to adjustment as described below plus an annual increase on the first day of each calendar year beginning January 1, 2014 and ending on and including the last January 1 prior to the expiration date of the Plan, equal to the least of (i) 12,000,000 shares, (ii) 4% of the shares outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year and (iii) such smaller number of shares as determined by the Board. Please read "—Certain Transactions." This number will also be adjusted due to the following shares becoming eligible to be used again for grants under the Plan:

•

shares subject to awards or portions of awards granted under the Plan which are forfeited, expire or lapse for any reason, or are settled for cash without the delivery of shares, to the extent of such forfeiture, expiration, lapse or cash settlement; and

•

shares that we repurchase prior to vesting so that such shares are returned to us.

        Shares granted under the Plan may be treasury shares, authorized but unissued shares, or shares purchased in the open market. The payment of cash dividends in conjunction with any outstanding awards will not be counted against the shares available for issuance under the Plan. In addition, if we or one of our subsidiaries acquires or combines with another company that has shares available for grant pursuant to a qualifying equity plan, we may use those shares (until such date as they could not

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have been used under such entity's plan) to grant awards pursuant to the Plan to individuals who were not providing services to us immediately prior to the acquisition or combination.

        The Plan will not provide for individual limits on awards that may be granted to any individual participant under the Plan. Rather, the amount of awards to be granted to individual participants will be determined by our Board of Directors or the Compensation Committee from time to time, as part of their compensation decision-making processes, provided, however, that the Plan will not permit awards having a grant date fair value in excess of $700,000 to be granted to our non-employee directors in any year.

Awards

        The Plan provides for the grant of stock options (including non-qualified stock options, or "NQSOs," and incentive stock options, or "ISOs"), restricted stock, dividend equivalents, stock payments, restricted stock units, or "RSUs," performance awards, stock appreciation rights, or "SARs," and other equity-based and cash-based awards, or any combination thereof. Awards under the Plan will be set forth in award agreements, which will detail the terms and conditions of the awards, including any applicable vesting and payment terms and post-termination exercise limitations as well as any other consequences with respect to the awards upon a termination of the applicable eligible individual's service. Equity-based awards will generally be settled in shares of our common stock, but the plan administrator may provide for cash settlement of any award. A brief description of each award type follows.

•

Non-qualified Stock Options.  NQSOs will provide for the right to purchase shares of our common stock at a specified price which generally, except with respect to certain substitute options granted in connection with corporate transactions, will not be less than fair market value on the date of grant. NQSOs may be granted for any term specified by the plan administrator that does not exceed ten years and will usually become exercisable in one or more installments after the grant date, subject to vesting conditions which may include continued employment or service with us, satisfaction of performance targets and/or other conditions, as determined by the plan administrator.

•

Incentive Stock Options.  ISOs will be designed in a manner intended to comply with the provisions of Section 422 of the Internal Revenue Code, or the Code, and will be subject to specified restrictions contained in the Code. ISOs will have an exercise price of not less than 100% of the fair market value of the underlying shares on the date of grant (or 110% in the case of ISOs granted to certain significant stockholders), except with respect to certain substitute ISOs granted in connection with a corporate transaction. Only employees will be eligible to receive ISOs, and ISOs will not have a term of more than ten years (or five years in the case of ISOs granted to certain significant stockholders). Vesting conditions may apply to ISOs as determined by the plan administrator and may include continued employment or service with us, satisfaction of performance targets and/or other conditions.

•

Restricted Stock.  Restricted stock may be granted to any eligible individual and made subject to such restrictions as may be determined by the plan administrator. Unless the plan administrator determines otherwise, restricted stock may be forfeited for no consideration or repurchased by us if the conditions or restrictions on vesting are not met. In general, restricted stock may not be sold or otherwise transferred until restrictions are removed or expire. Recipients of restricted stock, unlike recipients of options, will have voting rights and will have the right to receive dividends, if any, prior to the time when the restrictions lapse, subject to the terms of an applicable award agreement, which may provide for dividends to be placed in escrow and not released until the restrictions are removed or expire.

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•

Restricted Stock Units.  RSUs may be awarded to any eligible individual, typically without payment of consideration but subject to vesting conditions based upon continued employment or service with us, satisfaction of performance criteria and/or other conditions, all as determined by the plan administrator. Like restricted stock, RSUs generally may not be sold or otherwise transferred or hypothecated until the applicable vesting conditions are removed or expire. Unlike restricted stock, shares of stock underlying RSUs will not be issued until the RSUs vest (or later, if payment is deferred), and recipients of RSUs generally will have no voting or dividend rights with respect to such shares prior to the time when the applicable vesting conditions are satisfied.

•

Dividend Equivalents.  Dividend equivalents represent the per share value of the dividends, if any, paid by us, calculated with reference to the number of shares of our common stock covered by an award. Dividend equivalents may be settled in cash or shares and at such times as determined by the plan administrator.

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Stock Payments.  Stock payments may be authorized by the plan administrator in the form of our shares or an option or other right to purchase our shares as part of a deferred compensation or other arrangement in lieu of all or any part of compensation, including bonuses, that would otherwise be payable in cash to an employee, consultant or non-employee director.

•

Stock Appreciation Rights.  SARs may be granted in connection with stock options, other awards or separately. SARs typically provide for payment to the holder based upon increases in the price of a share over a set exercise price. The exercise price of any SAR granted under the Plan generally, except with respect to certain substitute SARs granted in connection with a corporate transaction, will be at least 100% of the fair market value of the underlying shares on the date of grant. The term of a SAR may not be longer than ten years. There are no restrictions specified in the Plan on the exercise of SARs or the amount of gain realizable therefrom, although restrictions may be imposed by the plan administrator in the SAR award agreement. SARs granted under the Plan may be settled in cash or our shares, or in a combination of both, at the election of the plan administrator. Vesting conditions may apply to SARs as determined by the plan administrator and may include continued employment or service with us, satisfaction of performance goals and/or other conditions.

•

Performance Awards.  Performance awards may be granted by the plan administrator on an individual or group basis. Generally, these awards will consist of bonuses based upon attainment of specific performance targets and may be paid in cash, our shares or a combination of both. Performance awards may also include "phantom" stock awards that provide for payments based upon the value of our shares.

Certain Transactions

        The plan administrator will have broad discretion to equitably adjust the provisions of the Plan and the terms and conditions of existing and future awards, including with respect to aggregate number and type of shares subject to the Plan and awards granted pursuant to the Plan, to prevent the dilution or enlargement of intended benefits and/or facilitate necessary or desirable changes in the event of certain transactions and events affecting our shares, such as stock dividends, stock splits, mergers, acquisitions, consolidations and other corporate transactions. In the case of certain events or changes in capitalization that constitute "equity restructurings," equitable adjustments will be non-discretionary. In the event of a change in control where the acquirer does not assume or replace awards granted under the Plan, such awards may be subject to accelerated vesting so that 100% of such awards will become vested and exercisable or payable, as applicable, and will be exercisable for a period of fifteen days following notice of such event from the plan administrator and, if not exercised, will terminate upon the expiration of such fifteen-day period. The plan administrator may also provide for the acceleration, cash-out, termination, assumption, substitution or conversion of awards in the event of a change in

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control or certain other unusual or nonrecurring events or transactions. A "change in control" is defined in the Plan to mean (i) the acquisition by a person or group of more than 50% of the total combined voting power of our outstanding securities, (ii) during any consecutive two-year period, the replacement of a majority of our incumbent directors with directors whose election was not supported by at least two-thirds of our incumbent directors, (iii) a merger, consolidation, reorganization or business combination or the sale of substantially all of our assets after which the Apollo Funds and its affiliates cease to own at least 50% of the combined voting power in us, in each case, other than a transaction which results in our voting securities before such transaction continuing to represent or being converted into a majority of the voting securities of the surviving entity and after which no person or group owns a majority of the combined voting power of the surviving entity or (iv) our liquidation or dissolution; provided, however, any event or occurrence whereby the Apollo Funds or a group consisting of our directors, executive officers or members of our management acquire voting control of us will not constitute a change in control for purposes of the Plan.

Transferability, Repricing and Participant Payments

        With limited exceptions for estate planning, domestic relations orders, certain beneficiary designations and the laws of descent and distribution, awards under the Plan are generally non-transferable prior to vesting and are exercisable only by the participant. The price per share of a stock option or SAR may not be decreased and an underwater stock option or SAR may not be replaced or cashed out without stockholder approval. With regard to tax withholding, exercise price and purchase price obligations arising in connection with awards under the Plan, the plan administrator may, in its discretion, accept cash or check, our shares that meet specified conditions, a "market sell order" (or other cashless broker-assisted transaction) or such other consideration as it deems suitable.

Amendment and Termination

        Our Board of Directors may terminate, amend or modify the Plan at any time and from time to time. However, we must generally obtain stockholder approval to increase the number of shares available under the Plan (other than in connection with certain corporate events, as described above) or to the extent required by applicable law, rule or regulation (including any applicable stock exchange rule).

Expiration Date

        The Plan will expire on, and no option or other award may be granted pursuant to the Plan after, the tenth anniversary of the date the plan was adopted by our Board of Directors. Any award that is outstanding on the expiration date of the Plan will remain in force according to the terms of the Plan and the applicable award agreement.

Awards To Be Granted Following This Offering

        Following the consummation of this offering, we expect that our Board of Directors will approve an award of restricted stock units under the Plan to certain of our key employees, including each of our NEOs. We currently expect that these awards will contain a combination of time and performance-based vesting conditions, with a three-year annual vesting schedule. However, the number of shares subject to the awards and the precise terms and conditions of the restricted stock units have not yet been finally determined or approved.

Director Compensation

        For 2012, individuals who served as members of our Board of Directors and predecessor governing bodies did not receive compensation for their services as directors.

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        Following the consummation of this offering, our or our subsidiaries' officers, employees, consultants or advisors who also serve as directors will not receive additional compensation for their service as directors. Following the consummation of this offering, our directors who are not our or our subsidiaries' officers, employees, consultants or advisors or Apollo's officers or employees will receive cash and/or equity-based compensation for their services as directors.

        Although the terms of our expected director compensation program have not yet been determined, we expect such compensation may consist of the following:

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an annual retainer of $40,000;

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an additional annual retainer of $10,000 for service as the chair of any standing committee; and

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an annual equity-based award granted under our Plan, having a value as of the grant date of approximately $150,000. Equity-based awards are expected to be subject to vesting conditions that have not yet been determined.

        Directors will also receive reimbursement for out-of-pocket expenses associated with attending such board or committee meetings and director and officer liability insurance coverage. Each director will be fully indemnified by us for actions associated with being a director to the fullest extent permitted under Delaware law.

Compensation Committee Interlocks and Insider Participation

        None of our officers or employees will be members of our Compensation Committee. None of our executive officers serve on the board of directors or compensation committee of a company that has an executive officer that serves on our Board of Directors or Compensation Committee. No member of our Board of Directors is an executive officer of a company in which one of our executive officers serves as a member of the board of directors or compensation committee of that company.

        To the extent any member of our Compensation Committee and affiliates of theirs has participated in transactions with us, a description of those transactions would be described in "Certain Relationships and Related Party Transactions."

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CERTAIN RELATIONSHIPS AND RELATED PARTY TRANSACTIONS

Corporate Reorganization

        In connection with our corporate reorganization, we engaged in certain transactions with certain affiliates and the limited partners of Athlon Holdings LP. Please read "Corporate Reorganization" for a description of these transactions.

Capital Contributions

        Prior to our corporate reorganization, the Apollo Funds had committed approximately $400 million of capital contributions to fund our business and operations. As of March 31, 2013, we had remaining capital commitments of approximately $38.1 million from the Apollo Funds. After our corporate reorganization, the Apollo Funds have no further capital commitments.

Stockholders Agreement

        We will enter into a stockholders agreement with the Apollo Funds and certain stockholders in connection with this offering that will provide that, except as otherwise required by applicable law, if the Apollo Funds hold: (a) at least 50% of our outstanding common stock, they will have the right to designate no fewer than that number of directors that would constitute a majority of our Board of Directors; (b) at least 30% but less than 50% of our outstanding common stock, they will have the right to designate up to three director nominees; (c) at least 20% but less than 30% of our outstanding common stock, they will have the right to designate up to two director nominees; and (d) at least 10% but less than 20% of our outstanding common stock, they will have the right to designate up to one director nominee. The agreement also provides that if the size of our Board of Directors is increased or decreased at any time to other than seven directors, the Apollo Funds' nomination rights will be proportionately increased or decreased, respectively, rounded up to the nearest whole number. In addition, the agreement provides that if the Apollo Funds hold at least 30% of our outstanding common stock, we will cause any committee of our Board of Directors to include in its membership at least one of the Apollo Funds nominees, except to the extent that such membership would violate applicable securities laws or stock exchange or stock market rules.

        Under the stockholders agreement, if the Apollo Funds hold at least 33¹/3% of our outstanding common stock, they will have the right to engage in each of the following actions:

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consult with and advise our senior management with respect to business and financial matters;

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inspect all of our books, records, facilities and properties and receive financial and operating data with respect to our business and properties, when reasonably requested; and

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designate a representative who may attend the meetings of our Board of Directors, receive the information given to directors and make recommendations to our Board of Directors. The representative shall have no vote on our Board of Directors.

        The stockholders agreement also provides that so long as the Apollo Funds hold at least 33¹/3% of our outstanding common stock, a majority of our Board of Directors, including a majority of the directors designated to our Board of Directors by the Apollo Funds, must approve certain of our significant business decisions before we are permitted to take action, including each of the following:

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amending, modifying or repealing any provision of our certificate of incorporation and bylaws or similar organization documents in a manner that adversely affects the Apollo Funds or their affiliates;

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•

issuing additional equity interests other than any (i) award under any stockholder-approved equity compensation plan, (ii) intra-company issuance among our subsidiaries and us or (iii) issuance of equity interests pursuant to the exchange agreement;

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consolidating or merging with or into any other entity, transferring all or substantially all of our and our subsidiaries' assets, taken as a whole, to another entity or entering into or agreeing to undertake any transaction that would constitute a "Change of Control" as defined in our credit agreement or the indenture governing our senior notes;

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disposing of any of our or any of our subsidiaries' assets with a value in excess of $100 million in any single transaction or $200 million in the aggregate in any series of transactions during a calendar year;

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consummating any acquisition by us or any of our subsidiaries of the equity interests or assets of any other entity involving consideration in excess of $100 million in any single transaction or $200 million in the aggregate in any series of transactions during a calendar year;

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incurring any indebtedness by us or any of our subsidiaries (including through capital leases, the issuance of debt securities or the guarantee of indebtedness of another entity) that would result in our total net indebtedness to adjusted EBITDA for the trailing twelve-month period exceeding 2.50 to 1.0;

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terminating our Chief Executive Officer or designating a new Chief Executive Officer; and

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changing the size of our Board of Directors.

        The stockholders agreement will also provide that the Apollo Funds, or any employee stockholder owning at least 1% of our outstanding common stock, may make one or more written demands requiring us to register the shares of our common stock owned by the Apollo Funds or the employee stockholders. In addition, any stockholder (including the Apollo Funds) will have piggyback rights entitling them to require us to register shares of our common stock owned by them in connection with any registration statements filed by us, subject to certain exceptions. We will agree to indemnify the Apollo Funds (to the extent they are selling stockholders in any such registration) against losses suffered by them in connection with any untrue or alleged untrue statement of a material fact contained in any registration statement, prospectus or preliminary prospectus or any omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statement therein not misleading, except insofar as the same may be caused by or contained in any information furnished in writing to us by such selling stockholder for use therein.

Transaction Fee Agreement

        We are a party to a Transaction Fee Agreement, dated August 23, 2010, which requires us to pay a fee to Apollo equal to 2% of the total equity contributed to us, as defined in the agreement, in exchange for consulting and advisory services provided by Apollo. In October 2012, Apollo assigned its rights and obligations under the Transaction Fee Agreement to one of its affiliates, Apollo Global Securities, LLC. Since our inception through March 31, 2013, we have incurred transaction fees under the Transaction Fee Agreement of approximately $7.5 million in total. Upon the consummation of this offering, we intend to terminate the Transaction Fee Agreement.

Services Agreement

        We are party to a Services Agreement, dated August 23, 2010, which requires us to compensate Apollo for consulting and advisory services equal to the higher of (i) 1.00% of earnings before interest, income taxes, depletion, depreciation, amortization and exploration expense per quarter and (ii) $62,500 per quarter (the "Advisory Fee"); provided, however, that such Advisory Fee for any

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calendar year shall not exceed $500,000. The Services Agreement also provides for reimbursement to Apollo for any reasonable out-of-pocket expenses incurred while performing services under the Services Agreement. During the first quarter of 2013 and 2012, we incurred approximately $405,000 and $213,000, respectively, of Advisory Fees. During 2012 and 2011, we incurred approximately $493,000 and $411,000, respectively, of Advisory Fees.

        The Services Agreement provides that Apollo will provide advisory services until the earliest of (i) August 23, 2020, (ii) such time as Apollo owns in the aggregate less than 5% of the beneficial economic interest of Athlon Holdings LP and (iii) such date as is mutually agreed upon by us and Apollo. Upon the consummation of this offering, we intend to terminate the Services Agreement and, in connection with the termination, Apollo will receive approximately $2.5 million (plus any unreimbursed expenses) from us. Such payment corresponds to the present value as of the date of termination of the aggregate annual fees that would have been payable during the remainder of the term of the Services Agreement (assuming a term ending on August 23, 2020) using a discount rate of 8.0%. Under the Services Agreement, we also agreed to indemnify Apollo and its affiliates and their respective limited partners, general partners, directors, members, officers, managers, employees, agents, advisors, their directors, officers and representatives for potential losses relating to the services contemplated under the Services Agreement.

Participation of Apollo Global Securities, LLC in Senior Notes Offering and this Offering

        Apollo Global Securities, LLC is an affiliate of our sponsor the Apollo Funds and received a portion of the gross spread as an initial purchaser in our senior notes offering of approximately $500,000. Apollo Global Securities, LLC is also an underwriter in this offering and will receive a portion of the discounts and commissions paid to the underwriters in this offering. See "Underwriting (Conflicts of Interest)."

Distribution

        We used a portion of the net proceeds from the senior notes offering to make a distribution to our Class A limited partners, including the Apollo Funds and our management team. The Apollo Funds received approximately $73 million of the distribution and the remaining Class A limited partners received approximately $2 million, in the aggregate.

Exchange Agreement

        We will enter into an exchange agreement with certain members of our management team and employees that will hold New Holdings Units after the closing of this offering. Under the exchange agreement, each such holder (and certain permitted transferees thereof) may, under certain circumstances after the date of the closing of this offering (subject to the terms of the exchange agreement), exchange their New Holdings Units for shares of common stock of Athlon Energy Inc. on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. As a holder exchanges its New Holdings Units, Athlon Energy Inc.'s interest in Athlon Holdings LP will be correspondingly increased.

Tax Receivable Agreement

        As described under "—Exchange Agreement," the holders of New Holdings Units may (subject to the terms of the exchange agreement) exchange such units for shares of common stock of Athlon Energy Inc. on a one-for-one basis. Athlon Holdings LP (and each of its subsidiaries treated as partnerships for United States federal income tax purposes) intends to make an election under Section 754 of the Code effective for each taxable year in which an exchange of Athlon Holdings LP units for shares of common stock occurs, which may result in an adjustment to the tax basis of the

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assets of Athlon Holdings LP at the time of an exchange. As a result of these exchanges, Athlon Energy Inc., which we refer to as the "corporate taxpayer", will become entitled to a proportionate share of the existing tax basis of the assets of Athlon Holdings LP. In addition, the purchase of New Holdings Units and subsequent exchanges are expected to result in increases in the tax basis of the assets of Athlon Holdings LP that otherwise would not have been available. Both this proportionate share and these increases in tax basis may reduce the amount of tax that the corporate taxpayer would otherwise be required to pay in the future. These increases in tax basis may also decrease gains (or increase losses) on future dispositions of certain capital assets to the extent tax basis is allocated to those capital assets. The IRS may challenge all or part of the existing tax basis, tax basis increase and increased deductions, and a court could sustain such a challenge.

        We will enter into a tax receivable agreement with certain members of our management team and employees that will hold New Holdings Units after the closing of this offering that will provide for the payment from time to time by the corporate taxpayer to such unitholders of Athlon Holdings LP of 85% of the amount of the benefits, if any, that the corporate taxpayer is deemed to realize as a result of increases in tax basis and certain other tax benefits related to exchanges of New Holdings Units pursuant to the exchange agreement, including tax benefits attributable to payments under the tax receivable agreement. These payment obligations will be obligations of the corporate taxpayer and not of Athlon Holdings LP. For purposes of the tax receivable agreement, the benefit deemed realized by the corporate taxpayer will be computed by comparing the actual income tax liability of the corporate taxpayer (calculated with certain assumptions) to the amount of such taxes that the corporate taxpayer would have been required to pay had there been no increase to the tax basis of the assets of Athlon Holdings LP as a result of the exchanges and had the corporate taxpayer not entered into the tax receivable agreement. The term of the tax receivable agreement will continue until all such tax benefits have been utilized or expired, unless the corporate taxpayer exercises its right to terminate the tax receivable agreement for an amount based on the agreed payments remaining to be made under the agreement, the corporate taxpayer breaches any of its material obligations under the tax receivable agreement or the holders of New Holdings Units elect to terminate the tax receivable agreement, in which case the corporate taxpayer's obligations will generally be accelerated. Estimating the amount of payments that may be made under the tax receivable agreement is by its nature imprecise, insofar as the calculation of amounts payable depends on a variety of factors. The actual increase in tax basis, as well as the amount and timing of any payments under the tax receivable agreement, will vary depending upon a number of factors, including:

•

the timing of exchanges—for instance, the increase in any tax deductions will vary depending on the fair value, which may fluctuate over time, of the depletable, depreciable or amortizable assets of Athlon Holdings LP at the time of each exchange;

•

the price of shares of our common stock at the time of the exchange—the increase in any tax deductions, as well as the tax basis increase in other assets, of Athlon Holdings LP is directly proportional to the price of shares of our common stock at the time of the exchange;

•

the extent to which such exchanges are taxable—if an exchange is not taxable for any reason, increased deductions will not be available; and

•

the amount and timing of our income—the corporate taxpayer will be required to pay 85% of the deemed benefits as and when deemed realized. If the corporate taxpayer does not have taxable income, the corporate taxpayer generally is not required (absent a change of control or circumstances requiring an early termination payment) to make payments under the tax receivable agreement for that taxable year because no benefit will have been actually realized. However, any tax benefits that do not result in realized benefits in a given tax year will likely generate tax attributes that may be utilized to generate benefits in previous or future tax years. The utilization of such tax attributes will result in payments under the tax receivable agreement.

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        The step-up in basis will depend on the fair value of the New Holdings Units at conversion. Further, we do not expect to be in a tax paying position before 2019, so we cannot presently determine what the benefit or payments under the tax receivable agreement will be. In addition, there is no intent of the holders of New Holdings Units to exchange their units for shares of our common stock in the foreseeable future.

        In addition, the tax receivable agreement will provide that upon certain mergers, asset sales, other forms of business combinations or other changes of control, the corporate taxpayer's (or its successor's) obligations with respect to exchanged or acquired New Holdings Units (whether exchanged or acquired before or after such transaction) would be based on certain assumptions, including that the corporate taxpayer would have sufficient taxable income to fully utilize the deductions arising from the increased tax deductions and tax basis and other benefits related to entering into the tax receivable agreement. As a result, we could be required to make payments under the tax receivable agreement that are greater than or less than the specified percentage of the actual benefits we realize in respect of the tax attributes subject to the tax receivable agreement. Furthermore, if we elect to terminate the tax receivable agreement early, we would be required to make an immediate payment equal to the present value of the anticipated future tax benefits, which upfront payment may be made years in advance of the actual realization of such future benefits. In these situations, our obligations under the tax receivable agreement could have a substantial negative impact on our liquidity.

        Decisions made in the course of running our business, such as with respect to mergers, asset sales, other forms of business combinations or other changes in control, may influence the timing and amount of payments that are received by an exchanging or selling existing owner under the tax receivable agreement. For example, the earlier disposition of assets following an exchange or acquisition transaction will generally accelerate payments under the tax receivable agreement and increase the present value of such payments, and the disposition of assets before an exchange or acquisition transaction will increase an existing owner's tax liability without giving rise to any rights of an existing owner to receive payments under the tax receivable agreement.

        Payments will be generally due under the tax receivable agreement within a specified period of time following the filing of our tax return for the taxable year with respect to which the payment obligation arises, although interest on such payments will begin to accrue at a rate of LIBOR plus 300 basis points from the due date (without extensions) of such tax return.

        Payments under the tax receivable agreement will be based on the tax reporting positions that we will determine. Although we are not aware of any issue that would cause the IRS to challenge a tax basis increase, the corporate taxpayer will not be reimbursed for any payments previously made under the tax receivable agreement. As a result, in certain circumstances, payments could be made under the tax receivable agreement in excess of the benefits that the corporate taxpayer actually realizes in respect of the tax attributes subject to the tax receivable agreement.

Athlon Holdings LP Amended and Restated Limited Partnership Agreement

        Upon the closing of this offering, the limited partnership agreement of Athlon Holdings LP will be amended and restated to, among other things, modify Athlon Holdings LP's capital structure by replacing its different classes of interests with a single new class of units as described in "Corporate Reorganization."

        The unitholders of Athlon Holdings LP, including Athlon Energy Inc., will incur U.S. federal, state and local income taxes on their proportionate share of any taxable income of Athlon Holdings LP. Net income of Athlon Holdings LP will generally be allocated to our unitholders (including Athlon Energy Inc.) in accordance with their percentage interest in Athlon Holdings LP. Net losses of Athlon Holdings LP will generally be allocated first to the unitholders (including Athlon Energy Inc.) in accordance with their percentage interest in Athlon Holdings LP until their capital accounts are reduced to zero, and

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then to the general partner. The partnership agreement of Athlon Holdings LP will provide for quarterly cash distributions, which we refer to as "tax distributions," to the limited partners of Athlon Holdings LP (including Athlon Energy Inc.). Generally, these tax distributions will be computed based on the estimate of the Board of Supervisors as to the projected deemed income tax liability of each limited partner with respect to the partnership interest of such limited partner. Tax distributions will be made only to the extent that cash is available to cover such distributions.

Policies and Procedures for Review of Related Party Transactions

        Pursuant to its written charter, our Audit Committee must review and approve all material related party transactions, which include any related party transactions that we would be required to disclose pursuant to Item 404 of Regulation S-K promulgated by the SEC. In determining whether to approve a related party transaction, our Audit Committee will consider a number of factors including whether the related party transaction is on terms and conditions no less favorable to us than may reasonably be expected in arm's-length transactions with unrelated parties.

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CORPORATE REORGANIZATION

        Athlon Energy Inc. is a holding company and its sole assets are controlling equity interests in Athlon Holdings LP and its subsidiaries. Athlon Energy Inc. operates and controls all of the business and affairs and consolidates the financial results of Athlon Holdings LP and its subsidiaries. Prior to our reorganization in April 2013, the Apollo Funds, members of our management team and certain employees owned all of the Class A limited partner interests in Athlon Holdings LP and members of our management team and certain employees owned all of the Class B limited partner interests in Athlon Holdings LP. In the reorganization, the Apollo Funds entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Athlon Holdings LP for common stock of Athlon Energy Inc. The remaining holders of Class A limited partner interests in Athlon Holdings LP have not exchanged their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Athlon Holdings LP exchanged their interests for common stock of Athlon Energy Inc. Upon closing of this offering, the limited partnership agreement of Athlon Holdings LP will be amended and restated to, among other things, modify Athlon Holdings LP's capital structure by replacing its different classes of interests with a single new class of units that we refer to as the "New Holdings Units." The members of our management team and certain employees that hold Class A limited partner interests will own New Holdings Units and will enter into an exchange agreement under which (subject to the terms of the exchange agreement) they will have the right, under certain circumstances, to exchange their New Holdings Units for shares of common stock of Athlon Energy Inc. on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. All other New Holdings Units will be held by Athlon Energy Inc.

        The diagrams below set forth our simplified organizational structure before and after our corporate reorganization and this offering. These charts are provided for illustrative purpose only and do not represent all legal entities affiliated with us. The ownership percentages after this offering are based on an estimated valuation of Athlon using an assumed initial public offering price of $19.00 per share, the midpoint of the price range set forth on the cover page of this prospectus.

Pre-Reorganization Structure Before the Offering

¹

Borrowing base of $320 million as of July 22, 2013.

²

Co-Issuer of our 7³/8% senior notes due 2021.

³

Guarantors of our credit agreement and 7³/8% senior notes due 2021.

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Post-Reorganization Structure After the Offering

¹

The Apollo Funds and the public stockholders will hold 65.8% and 22.1% of our shares of common stock, respectively, if the underwriters exercise in full their option to purchase additional shares of common stock from the Apollo Funds.

²

Borrowing base of $320 million as of July 22, 2013.

³

Co-Issuer of our 7³/8% senior notes due 2021.

⁴

Guarantors of our credit agreement and 7³/8% senior notes due 2021.

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PRINCIPAL AND SELLING STOCKHOLDERS

        The following table sets forth the beneficial ownership of our common stock and New Holdings Units, after giving effect to the reorganization transactions described under "Corporate Reorganization," immediately prior to and after this offering by:

•

each entity or person known by us to beneficially own more than 5% of our outstanding common stock (assuming the exchange of all New Holdings Units for common stock);

•

each of our named executive officers;

•

each member of or nominee to our Board of Directors;

•

all of our directors, director nominees and executive officers as a group; and

•

each of the selling stockholders.

        Except as otherwise indicated, the person or entities listed below have sole voting and investment power with respect to all shares of our common stock beneficially owned by them, except to the extent this power may be shared with a spouse. All information with respect to beneficial ownership has been furnished by the respective directors, director nominees, named executive officers or 5% or more stockholders, as the case may be. Unless otherwise indicated, the address for each listed beneficial owner is 420 Throckmorton Street, Suite 1200, Fort Worth, Texas 76102.

        Upon the completion of this offering, the Apollo Funds will own, in the aggregate, approximately 68.6% of our outstanding common stock (or approximately 65.8% if the underwriters exercise in full their option to purchase additional shares of common stock from the Apollo Funds). As a result, we will qualify as a "controlled company" within the meaning of the corporate governance rules of the NYSE.

        If this offering is priced above the assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus) or if more than the number of shares set forth on the cover page of this prospectus are sold, then we may sell only such number of shares (the "threshold number") as is necessary to achieve gross proceeds from this offering to us of $300 million, and the Apollo Funds may sell a number of shares equal to the difference between the threshold number and the number of shares sold in this offering.

						Number of shares of common stock offered if the underwriters' option to purchase additional shares is exercised in full
	Common stock beneficially owned before the offering							Common stock beneficially owned after the offering (assuming no exercise of the underwriters' option to purchase additional shares)					Common stock beneficially owned after the offering (assuming the underwriters' option to purchase additional shares is exercised in full)
Name and Address of Beneficial Owner1	Number		Percentage					Number		Percentage			Number		Percentage
Principal and Selling Stockholders
Apollo Funds2		56,364,418		82.7	%		2,368,421		56,364,418		67.1	%		53,995,997		64.3	%
Directors and Named Executive Officers
Robert C. Reeves3		4,775,013		7.0	%		—		4,775,013		5.7	%		4,775,013		5.7	%
Gregory A. Beard		—		*			—		—		*			—		*
Sam Oh		—		*			—		—		*			—		*
Rakesh Wilson		—		*			—		—		*			—		*
Ted A. Gardner4		—		*			—		—		*			—		*
Nelson K. Treadway3		1,477,745		2.2	%		—		1,477,745		1.8	%		1,477,745		1.8	%
David B. McClelland3		598,722		*			—		598,722		*			598,722		*
Directors and executive officers as a group (12 persons)3		10,080,628		14.8	%		—		10,080,628		12.0	%		10,080,628		12.0	%

*

Less than 1%.

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¹

The amounts and percentages of common stock beneficially owned are reported on the bases of regulations of the SEC governing the determination of beneficial ownership of securities. Under the rules of the SEC, a person is deemed to be a "beneficial owner" of a security if that person has or shares voting power, which includes the power to vote or direct the voting of such security, or investment power, which includes the power to dispose of or to direct the disposition of such security. Securities that can be so acquired are deemed to be outstanding for purposes of computing such person's ownership percentage, but not for purposes of computing any other person's percentage. Under these rules, more than one person may be deemed beneficial owner of the same securities and a person may be deemed to be a beneficial owner of securities as to which such person has no economic interest. Except as otherwise indicated in these footnotes, each of the beneficial owners has, to our knowledge, sole voting and investment power with respect to the indicated shares of common stock. The amounts shown in the table are based on an estimated valuation of Athlon using an assumed initial public offering price of $19.00 per share (the midpoint of the price range set forth on the cover page of this prospectus).

²

The amount reported includes shares held of record by Apollo Athlon Holdings, L.P. ("Athlon Holdings") and AP Overseas VII (Athlon FC) Holdings, L.P. ("Overseas VII (Athlon FC)," together with Athlon Holdings, the "Apollo Funds"). Apollo Management VII, L.P. ("Management VII") is the manager of the Apollo Funds. AIF VII Management, LLC ("AIF VII LLC") is the general partner of Management VII. Apollo Management, L.P. ("Apollo Management") is the sole member and manager of AIF VII LLC, and Apollo Management GP, LLC ("Apollo Management GP") is the general partner of Apollo Management. Apollo Management Holdings, L.P. ("Management Holdings") is the sole member and manager of Apollo Management GP, and Apollo Management Holdings GP, LLC ("Management Holdings GP") is the general partner of Management Holdings. Leon Black, Joshua Harris and Marc Rowan are the managers, as well as executive officers, of Management Holdings GP, and as such may be deemed to have voting and dispositive control over the shares of our common stock held by the Apollo Funds. The address of the Apollo Funds is One Manhattanville Road, Suite 201, Purchase, New York 10577. The address of each of Management VII, AIF VII LLC, Apollo Management, Apollo Management GP, Management Holdings and Management Holdings GP, and Messrs. Black, Harris and Rowan, is 9 West 57th Street, 43rd Floor, New York, New York 10019.

³

Includes New Holdings Units that are exchangeable for shares of our common stock as follows: Mr. Reeves (730,186), Mr. Treadway (264,448), Mr. McClelland (67,885) and directors and executive officers as a group (1,712,218).

⁴

Director nominee.

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DESCRIPTION OF CAPITAL STOCK

The following is a description of the material terms of our amended and restated certificate of incorporation and amended and restated bylaws as each will be in effect as of the closing of this offering, and of specific provisions of Delaware law. The following description is intended as a summary only and is qualified in its entirety by reference to our amended and restated certificate of incorporation, our amended and restated bylaws and the DGCL.

General

        Pursuant to our amended and restated certificate of incorporation, our capital stock will consist of 550,000,000 authorized shares, of which 500,000,000 shares, par value $0.01 per share, will be designated as "common stock" and 50,000,000 shares, par value $0.01 per share, will be designated as "preferred stock." There will be no shares of preferred stock outstanding immediately following the closing of this offering. Upon the effectiveness of our amended and restated certificate of incorporation following the closing of this offering, we will have one class of common stock.

Common Stock

        Voting Rights.    Holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders. Holders of common stock do not have cumulative voting rights in the election of directors.

        Dividend Rights.    Holders of common stock are entitled to receive ratably dividends if, as and when dividends are declared from time to time by our Board of Directors out of funds legally available for that purpose, after payment of dividends required to be paid on outstanding preferred stock, as described below, if any. Under Delaware law, we can only pay dividends either out of "surplus" or out of the current or the immediately preceding year's net profits. Surplus is defined as the excess, if any, at any given time, of the total assets of a corporation over its total liabilities and statutory capital. The value of a corporation's assets can be measured in a number of ways and may not necessarily equal their book value.

        Liquidation Rights.    Upon liquidation, dissolution or winding up of our affairs, whether voluntarily or involuntarily, the holders of common stock are entitled to receive ratably the assets available for distribution to the stockholders after payment of liabilities and accrued but unpaid dividends and liquidation preferences on any outstanding preferred stock.

        Other Matters.    The common stock has no preemptive, subscription or conversion rights. There are no redemption or sinking fund provisions applicable to the common stock. All outstanding shares of our common stock are fully paid and non-assessable, and the shares of our common stock offered in this offering, upon payment and delivery in accordance with the underwriting agreement, will be fully paid and non-assessable.

Preferred Stock

        Pursuant to our amended and restated certificate of incorporation, shares of preferred stock will be issuable from time to time, in one or more series, with the designations of the series, the dividend rates and whether such dividends will be cumulative or non-cumulative, the voting conversion or exchange rights of the shares of the series (if any), redemption rights, whether or not the shares of the series will be entitled to the benefit of a retirement or sinking fund, liquidation rights, the powers, preferences and relative, participation, optional or other special rights (if any), and any qualifications, limitations or restrictions thereof as our Board of Directors from time to time may adopt by resolution (and without further stockholder approval), subject to certain limitations. Each series will consist of that number of shares as will be stated and expressed in the certificate of designations providing for the

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issuance of the stock of the series, which number may be increased or decreased from time to time by our Board of Directors. All shares of any one series of preferred stock will be identical.

Composition of Board of Directors; Election and Removal of Directors; Number of Directors

        In accordance with our amended and restated certificate of incorporation and our amended and restated bylaws, the number of directors comprising our Board of Directors will be determined from time to time by our Board of Directors, and only a majority of the Board of Directors may fix the number of directors; provided that in no event shall the total number of directors be less than three nor more than fifteen. Assuming the Apollo Funds continue to control at least 50% of our common stock, we intend to avail ourselves of the "controlled company" exception under the NYSE rules, which exempt us from certain requirements, including the requirements that we have a majority of independent directors on our Board of Directors and that we have a compensation committee and a nominating and corporate governance committee composed entirely of independent directors. We will, however, remain subject to the requirement that we have an audit committee composed entirely of independent members.

        The stockholders agreement that we will enter into in connection with this offering will provide that, except as otherwise required by applicable law, if the Apollo Funds hold: (a) at least 50% of our outstanding common stock, they will have the right to designate no fewer than that number of directors that would constitute a majority of our Board of Directors; (b) at least 30% but less than 50% of our outstanding common stock, they will have the right to designate up to three director nominees; (c) at least 20% but less than 30% of our outstanding common stock, they will have the right to designate up to two director nominees; and (d) at least 10% but less than 20% of our outstanding common stock, they will have the right to designate up to one director nominee. The agreement also provides that if the size of our Board of Directors is increased or decreased at any time to other than seven directors, Apollo's nomination rights will be proportionately increased or decreased, respectively, rounded up to the nearest whole number. In addition, the agreement provides that if the Apollo Funds hold at least 30% of our outstanding common stock, we will cause any committee of our Board of Directors to include in its membership at least one of the Apollo Funds nominees, except to the extent that such membership would violate applicable securities laws or stock exchange or stock market rules.

        Upon the closing of this offering, it is anticipated that we will have five directors. Within 90 days of our listing on the NYSE, we will appoint at least one additional director, and within one year of the date of effectiveness of the registration statement, we will appoint at least one more additional director. Our amended and restated bylaws will provide that our Board of Directors is divided into three classes of directors, with the classes to be as nearly equal in number as possible. As a result, approximately one-third of our Board of Directors will be elected at each annual meeting of stockholders, with such elections decided by plurality vote, each year. The classification of directors has the effect of making it more difficult for stockholders to change the composition of our Board of Directors. Each director is to hold office until his successor is duly elected and qualified or until his earlier death, resignation or removal. Any vacancies on our Board of Directors may be filled only by the affirmative vote of a majority of the remaining directors, although less than a quorum. Our amended and restated certificate of incorporation will provide that stockholders do not have the right to cumulative votes in the election of directors. At any meeting of our Board of Directors, except as otherwise required by law, a majority of the total number of directors then in office will constitute a quorum for all purposes. Please read "Management—Committees of the Board of Directors."

Special Meetings of Stockholders

        Our amended and restated bylaws will provide that special meetings of the stockholders may be called only by the majority of our Board of Directors or the chairman of our Board of Directors, and only proposals included in our notice to stockholders may be considered at such special meetings.

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Certain Corporate Anti-Takeover Provisions

        Certain provisions in our amended and restated certificate of incorporation and amended and restated bylaws may be deemed to have an anti-takeover effect and may delay, deter or prevent a tender offer or takeover attempt that a stockholder might consider to be in its best interests, including attempts that might result in a premium being paid over the market price for the shares held by stockholders.

Preferred Stock

        Our amended and restated certificate of incorporation will contain provisions that permit our Board of Directors to issue, without any further vote or action by the stockholders, shares of preferred stock in one or more series and, with respect to each such series, to fix the number of shares constituting the series and the designation of the series, the dividend rates and whether such dividends will be cumulative or non-cumulative, the voting conversion or exchange rights of the shares of the series (if any), redemption rights, whether or not the shares of the series will be entitled to the benefit of a retirement or sinking fund, liquidation rights, the powers, preferences and relative, participation, optional and other special rights, if any, and any qualifications, limitations or restrictions, of the shares of such series. Please read "—Preferred Stock."

Classified Board

        Our amended and restated certificate of incorporation and amended and restated bylaws will provide that our Board of Directors is divided into three classes of directors, with the classes to be as nearly equal in number as possible, and the number of directors on our Board of Directors may be fixed only by the majority of our Board of Directors, as described above in "—Composition of Board of Directors; Election and Removal of Directors; Number of Directors."

Removal of Directors; Vacancies

        At any time at least 33¹/3% of the voting power of all our shares is owned by the Apollo Funds and the Apollo Funds cast their votes associated with such shares in favor of the proposed action, our stockholders will be able to remove directors only by the affirmative vote of the holders of a majority of the voting power entitled to vote for the election of directors. At any other time, our stockholders will be able to remove directors only for cause and only by the affirmative vote of the holders of at least 66²/3% of the voting power entitled to vote for the election of directors. Vacancies on our Board of Directors may be filled only by a majority of our Board of Directors, although less than a quorum.

No Cumulative Voting

        Our amended and restated certificate of incorporation will provide that stockholders do not have the right to cumulative votes in the election of directors. Cumulative voting rights would have been available to the holders of our common stock if our amended and restated certificate of incorporation had not specifically provided that cumulative voting was not available.

No Stockholder Action by Written Consent; Calling of Special Meetings of Stockholders

        Our amended and restated certificate of incorporation will not permit stockholder action without a meeting by consent if less than a majority of the voting power of all our shares is owned by the Apollo Funds. So long as the Apollo Funds own a majority of the voting power of all our shares, stockholder action without a meeting by consent is permitted without a meeting, without prior notice and without a vote, if a consent or consents in writing, setting forth the action so taken, is signed by stockholders having not less than the minimum number of votes that would be necessary to authorize or take the action at a meeting at which all our shares were present and voted. Our amended and restated bylaws

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will also provide that special meetings of the stockholders may be called only by a majority of our Board of Directors or the chairman of our Board of Directors, and only proposals included in our notice may be considered at such special meetings.

Advance Notice Requirements for Stockholders Proposals and Director Nominations

        Our amended and restated bylaws will provide that stockholders seeking to bring business before an annual meeting of stockholders, or to nominate candidates for election as directors at an annual meeting of stockholders, must provide timely notice thereof in writing. To be timely, a stockholder's notice generally will have to be delivered to and received at our principal executive offices not less than 60 days nor more than 120 days prior to the first anniversary of the preceding year's annual meeting; provided, that in the event that the date of such meeting is advanced more than 30 days prior to, or delayed by more than 30 days after, the anniversary of the preceding year's annual meeting of our stockholders, a stockholder's notice to be timely will have to be so delivered not earlier than the close of business on the 120th day prior to such meeting and not later than the close of business on the later of the 90th day prior to such meeting or, if the first public announcement of the date of such annual meeting is less than 100 days prior to such meeting, the tenth day following the day on which public announcement of the date of such meeting is first made. Our amended and restated bylaws will also specify certain requirements as to the form and content of a stockholder's notice. These provisions may preclude stockholders from bringing matters before an annual meeting of stockholders or from making nominations for directors at an annual meeting of stockholders.

        All the foregoing proposed provisions of our amended and restated certificate of incorporation and amended and restated bylaws could discourage potential acquisition proposals and could delay or prevent a change in control. These provisions are intended to enhance the likelihood of continuity and stability in the composition of our Board of Directors and in the policies formulated by our Board of Directors and to discourage certain types of transactions that may involve an actual or threatened change of control. These same provisions may delay, deter or prevent a tender offer or takeover attempt that a stockholder might consider to be in its best interest. In addition, such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our common stock that could result from actual or rumored takeover attempts. Such provisions also may have the effect of preventing changes in our management.

Delaware Anti-Takeover Law

        We have elected to be exempt from the restrictions imposed under Section 203 of the DGCL. Section 203 of the DGCL provides that, subject to exception specified therein, an "interested stockholder" of a Delaware corporation shall not engage in any "business combination," including general mergers or consolidations or acquisitions of additional shares of the corporation, with the corporation for a three-year period following the time that such stockholder becomes an interested stockholder unless:

•

prior to such time, the board of directors of the corporation approved either the business combination or the transaction which resulted in the stockholder becoming an interested stockholder;

•

upon consummation of the transaction which resulted in the stockholder becoming an "interested stockholder," the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced (excluding specified shares); or

•

on or subsequent to such time, the business combination is approved by the board of directors of the corporation and authorized at an annual or special meeting of stockholders, and not by

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written consent, by the affirmative vote of at least 66²/3% of the outstanding voting stock not owned by the interested stockholder.

        Under Section 203, the restrictions described above also do not apply to specified business combinations proposed by an interested stockholder following the announcement or notification of one of specified transactions involving the corporation and a person who had not been an interested stockholder during the previous three years or who became an interested stockholder with the approval of a majority of the corporation's directors, if such transaction is approved or not opposed by a majority of the directors who were directors prior to any person becoming an interested stockholder during the previous three years or were recommended for election or elected to succeed such directors by a majority of such directors.

        Except as otherwise specified in Section 203, an "interested stockholder" is defined to include:

•

any person that is the owner of 15% or more of the outstanding voting stock of the corporation, or is an affiliate or associate of the corporation and was the owner of 15% or more of the outstanding voting stock of the corporation at any time within three years immediately prior to the date of determination; and

•

the affiliates and associates of any such person.

        Under some circumstances, Section 203 makes it more difficult for a person who is an interested stockholder to effect various business combinations with us for a three-year period.

Corporate Opportunity

        Under our amended and restated certificate of incorporation, to the extent permitted by law:

•

any director or officer of Athlon who is also an officer, director, employee, managing director or other affiliate of Apollo (each a "Covered Apollo Person") has the right to, and has no duty to abstain from, exercising such right to, conduct business with any business that is competitive or in the same line of business as Athlon, do business with any of Athlon's clients, customers, vendors or lessors, or make investments in the kind of property in which Athlon may make investments;

•

if a Covered Apollo Person or any of its officers, partners, directors or employees acquire knowledge of a potential transaction that could be a corporate opportunity, he has no duty to offer such corporate opportunity to Athlon;

•

Athlon has renounced any interest or expectancy in, or in being offered an opportunity to participate in, such corporate opportunities; and

•

in the event that any of Athlon's directors and officers who is also a Covered Apollo Person acquires knowledge of a corporate opportunity or is offered a corporate opportunity, provided that this knowledge was not acquired solely in such person's capacity as Athlon's director or officer and such person acted in good faith, then such person will be deemed to have fully satisfied such person's fiduciary duty and will not be liable to us or our stockholders if any of the Covered Apollo Persons pursues or acquires such corporate opportunity or if such person did not present the corporate opportunity to Athlon.

Amendment of Our Certificate of Incorporation

        Our amended and restated certificate of incorporation will provide that at any time the Apollo Funds control at least 33¹/3% of the voting power of our outstanding common stock, the amended and restated certificate of incorporation can be amended with the affirmative vote of a majority of the outstanding stock entitled to vote thereon or by the vote of a majority of our Board of Directors, so

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long as the Apollo Funds vote in favor of such amendment. At any other time our amended and restated certificate of incorporation will provide that the amended and restated certificate of incorporation can be amended by the affirmative vote of at least 66²/3% of the outstanding stock entitled to vote thereon or by the vote of a majority of our Board of Directors.

Amendment of Our Bylaws

        Our amended and restated certificate of incorporation will provide that at any time the Apollo Funds control at least 33¹/3% of the voting power of our outstanding common stock, the amended and restated bylaws can be amended with the affirmative vote of a majority of the outstanding stock entitled to vote thereon, so long as the Apollo Funds vote in favor of such amendment, or by the vote of a majority of our Board of Directors. At any other time our amended and restated certificate of incorporation will provide that the amended and restated bylaws can be amended by the affirmative vote of at least 66²/3% of the outstanding stock entitled to vote thereon or by the vote of a majority of our Board of Directors.

Limitation of Liability and Indemnification

        Our amended and restated certificate of incorporation will limit the liability of our directors to the maximum extent permitted by Delaware law. Delaware law provides that directors will not be personally liable for monetary damages for breach of their fiduciary duties as directors, except with respect to liability:

•

for any breach of the director's duty of loyalty to us or our stockholders;

•

for acts or omissions not in good faith or that involve intentional misconduct or a knowing violation of law;

•

for any unlawful payments of dividends or unlawful stock repurchases or redemption as provided in Section 174 of the DGCL; or

•

for any transaction from which the director derived any improper personal benefit.

        However, if the DGCL is amended to authorize corporate action further eliminating or limiting the personal liability of directors, then the liability of our directors will be eliminated or limited to the fullest extent permitted by the DGCL, as so amended. The modification or repeal of this provision of our amended and restated certificate of incorporation will not adversely affect any right or protection of a director existing at the time of such modification or repeal.

        Our amended and restated certificate of incorporation and amended and restated bylaws will provide that we will, to the fullest extent from time to time permitted by law, indemnify our directors and officers against all liabilities and expenses in any suit or proceeding, arising out of their status as an officer or director or their activities in these capacities. We will also indemnify any person who, at our request, is or was serving as a director, officer, trustee, employee or agent of another corporation, partnership, joint venture, trust or other enterprise. We may, by action of our Board of Directors, provide indemnification to our employees and agents within the same scope and effect as the foregoing indemnification of directors and officers. In addition, we intend to enter into separate indemnification agreements with each of our directors and executive officers, which may be broader than the specific indemnification provisions contained in the DGCL. These indemnification agreements may require us, among other things, to indemnify our directors and officers against liabilities that may arise by reason of their status or service as directors or officers, other than liabilities arising from willful misconduct.

        The right to be indemnified will include the right of an officer or a director to be paid expenses, including attorneys' fees, in advance of the final disposition of any proceeding, provided that, if

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required by law, we receive an undertaking to repay such amount if it will be determined that he or she is not entitled to be indemnified.

        Our Board of Directors may take such action as it deems necessary to carry out these indemnification provisions, including adopting procedures for determining and enforcing indemnification rights and purchasing insurance policies. Our Board of Directors may also adopt bylaws, resolutions or contracts implementing indemnification arrangements as may be permitted by law. Neither the amendment nor the repeal of these indemnification provisions, nor the adoption of any provision of our amended and restated certificate of incorporation inconsistent with these indemnification provisions, will eliminate or reduce any rights to indemnification relating to such person's status or any activities prior to such amendment, repeal or adoption.

        We believe these provisions will assist in attracting and retaining qualified individuals to serve as directors and officers.

Transfer Agent and Registrar

        The transfer agent and registrar for our common stock will be Computershare Trust Company, N.A.

Listing

        We have been approved to list our common stock on the NYSE under the symbol "ATHL."

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SHARES ELIGIBLE FOR FUTURE SALE

        Prior to this offering, there has been no public market for our common stock, and no predictions can be made about the effect, if any, that market sales of shares of our common stock or the availability of such shares for sale will have on the market price prevailing from time to time. Nevertheless, the actual sale of, or the perceived potential for the sale of, our common stock in the public market may have an adverse effect on the market price for our common stock and could impair our ability to raise capital through future sales of our securities. Please read "Risk Factors—Risks Related to this Offering and Our Common Stock—Future sales of our common stock, or the perception that such future sales may occur, may cause our stock price to decline."

Sales of Restricted Shares

        Upon the closing of this offering, we will have 82,122,646 outstanding shares of common stock. Of these shares, all of the 15,789,474 shares of common stock to be sold in this offering will be freely tradable without restriction or further registration under the Securities Act, unless the shares are held by any of our "affiliates" as such term is defined in Rule 144 of the Securities Act. All remaining shares of common stock held by existing stockholders will be deemed "restricted securities" as such term is defined under Rule 144. The restricted securities were issued and sold by us in private transactions and are eligible for public sale only if registered under the Securities Act or if they qualify for an exemption from registration under Rule 144 or Rule 701 under the Securities Act, which rules are summarized below.

        As a result of the lock-up agreements described below and the provisions of Rule 144 and Rule 701 under the Securities Act, 64,757,222 shares of our common stock held by the Apollo Funds (assuming the underwriters do not exercise their option to purchase additional shares of common stock from the Apollo Funds) and our directors and executive officers will be available for sale in the public market upon the expiration of the lock-up agreements, beginning 180 days after the date of this prospectus (subject to extension) and when permitted under Rule 144 or Rule 701. In addition, 1,575,950 shares of our common stock held by other employees will not be subject to a lock-up agreement.

Rule 144

        In general, under Rule 144, a person (or persons whose shares are aggregated) who is not deemed to have been an affiliate of ours at any time during the three months preceding a sale, and who has beneficially owned restricted securities within the meaning of Rule 144 for a least six months (including any period of consecutive ownership of preceding non-affiliated holders) would be entitled to sell those shares, subject only to the availability of current public information about us. A non-affiliated person who has beneficially owned restricted securities within the meaning of Rule 144 for at least one year would be entitled to sell those shares without regard to the provisions of Rule 144.

        In connection with our reorganization transactions, we exchanged Class B limited partner interests in Athlon Holdings LP held by members of our management team and certain employees for 9,968,754 shares of our common stock. Such shares are expected to be eligible for resale by the holders thereof 90 days following the closing of this offering, subject to the lock-up agreements discussed below.

        A person (or persons whose shares are aggregated) who is deemed to be an affiliate of ours and who has beneficially owned restricted securities within the meaning of Rule 144 for at least six months would be entitled to sell within any three-month period a number of shares that does not exceed the greater of 1% of the then outstanding shares of our common stock or the average weekly trading volume of our common stock reported through the NYSE during the four calendar weeks preceding

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the filing of notice of the sale. Such sales are also subject to certain manner of sale provisions, notice requirements and the availability of current public information about us.

Rule 701

        In general, under Rule 701, any of our employees, directors, officers, consultants or advisors who purchases shares from us in connection with a compensatory stock or option plan or other written agreement before the effective date of this offering is entitled to sell such shares 90 days after the effective date of this offering in reliance on Rule 144, without having to comply with the holding period requirement of Rule 144 and, in the case of non-affiliates, without having to comply with the public information, volume limitation or notice filing provisions of Rule 144. The SEC has indicated that Rule 701 will apply to typical stock options granted by an issuer before it becomes subject to the reporting requirements of the Exchange Act, along with the shares acquired upon exercise of such options, including exercises after the date of this prospectus.

Stock Issued Under Employee Plans

        We intend to file a registration statement on Form S-8 under the Securities Act to register 8,400,000 shares of common stock initially reserved for issuance under the Athlon Energy Inc. 2013 Incentive Award Plan that we plan to adopt prior to the completion of this offering. This registration statement is expected to be filed following the effective date of the registration statement of which this prospectus forms a part and will be effective upon filing. Accordingly, shares registered under such registration statement will be available for sale in the open market following the effective date, unless such shares are subject to vesting restrictions with us, Rule 144 restrictions applicable to our affiliates or the lock-up restrictions described below.

Registration Rights

        We have granted the Apollo Funds and certain members of our management team that hold New Holdings Units registration rights, in each case, with respect to an aggregate of 62,617,176 shares of common stock beneficially owned by them. Please read "Certain Relationships and Related Party Transactions—Stockholders Agreement" for more detail regarding these registration rights.

Exchange of New Holdings Units into Shares of Common Stock

        We will enter into an exchange agreement with certain members of our management team and employees that will hold an aggregate of 1,862,043 New Holdings Units after the closing of this offering. Under the exchange agreement, each such holder (and certain permitted transferees thereof) may, under certain circumstances after the first anniversary of the closing of this offering, exchange their New Holdings Units for shares of common stock of Athlon Energy Inc. on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends and reclassifications. A holder that receives shares of our common stock upon exchange of its New Holdings Units will be eligible to sell its shares subject to Rule 144.

Lock-Up Agreements

        We, the Apollo Funds and each of our directors and executive officers have agreed that, subject to certain exceptions, without the prior written consent of Citigroup Global Markets Inc., we and they will not, directly or indirectly, for a period of 180 days after the date of the offering, offer, pledge, sell, contract to sell or otherwise transfer or dispose of any shares of our common stock (other than the shares sold by us and, if applicable, the Apollo Funds in this offering) or any other securities convertible into or exercisable or exchangeable for our common stock. For additional information, please read "Underwriting (Conflicts of Interest)."

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MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES TO NON-U.S. HOLDERS

        The following discussion is a summary of the material U.S. federal income tax consequences to non-U.S. holders (as defined below) of the purchase, ownership and disposition of our common stock issued pursuant to this offering, but does not purport to be a complete analysis of all potential tax effects. The effects of other U.S. federal tax laws, such as estate and gift tax laws, and any applicable state, local or foreign tax laws are not discussed. This discussion is based on the Internal Revenue Code of 1986, as amended (the "Code"), Treasury Regulations promulgated thereunder, judicial decisions and published rulings and administrative pronouncements of the IRS in effect as of the date of this offering. These authorities may change or be subject to differing interpretations. Any such change may be applied retroactively in a manner that could adversely affect a non-U.S. holder of our common stock. We have not sought and will not seek any rulings from the IRS regarding the matters discussed below. There can be no assurance the IRS or a court will not take a contrary position regarding the tax consequences of the purchase, ownership and disposition of our common stock.

        This discussion is limited to non-U.S. holders that hold our common stock as a "capital asset" within the meaning of Section 1221 of the Code (property held for investment). This discussion does not address all U.S. federal income tax consequences relevant to a non-U.S. holder's particular circumstances, including the impact of the unearned income Medicare contribution tax. In addition, it does not address consequences relevant to non-U.S. holders subject to particular rules, including, without limitation:

•

U.S. expatriates and certain former citizens or long-term residents of the United States;

•

persons subject to the alternative minimum tax;

•

persons holding our common stock as part of a hedge, straddle or other risk reduction strategy or as part of a conversion transaction or other integrated investment;

•

banks, insurance companies and other financial institutions;

•

real estate investment trusts or regulated investment companies;

•

brokers, dealers or traders in securities;

•

"controlled foreign corporations," "passive foreign investment companies" and corporations that accumulate earnings to avoid U.S. federal income tax;

•

S corporations, partnerships or other entities or arrangements treated as partnerships for U.S. federal income tax purposes;

•

tax-exempt organizations or governmental organizations;

•

persons deemed to sell our common stock under the constructive sale provisions of the Code;

•

persons who hold or receive our common stock pursuant to the exercise of any employee stock option or otherwise as compensation; and

•

tax-qualified retirement plans.

        If a partnership (or other entity treated as a partnership for U.S. federal income tax purposes) holds our common stock, the tax treatment of a partner in the partnership will depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level. Accordingly, partnerships holding our common stock and the partners in such partnerships should consult their tax advisors regarding the U.S. federal income tax consequences to them.

THIS DISCUSSION IS FOR INFORMATION PURPOSES ONLY AND IS NOT INTENDED AS TAX ADVICE. INVESTORS SHOULD CONSULT THEIR TAX ADVISORS WITH RESPECT TO THE APPLICATION OF THE U.S. FEDERAL INCOME TAX LAWS TO THEIR PARTICULAR

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SITUATIONS AS WELL AS ANY TAX CONSEQUENCES OF THE PURCHASE, OWNERSHIP AND DISPOSITION OF OUR COMMON STOCK ARISING UNDER THE U.S. FEDERAL ESTATE OR GIFT TAX LAWS OR UNDER THE LAWS OF ANY STATE, LOCAL OR NON-U.S. TAXING JURISDICTION OR UNDER ANY APPLICABLE INCOME TAX TREATY.

Definition of a Non-U.S. Holder

        For purposes of this discussion, a "non-U.S. holder" is any beneficial owner of our common stock that is neither a "U.S. person" nor a partnership for United States federal income tax purposes. A U.S. person is any of the following:

•

an individual who is a citizen or resident of the United States;

•

a corporation (or other entity taxable as a corporation for U.S. federal income tax purposes) created or organized under the laws of the United States, any state thereof, or the District of Columbia;

•

an estate, the income of which is subject to U.S. federal income tax regardless of its source; or

•

a trust that (1) is subject to the primary supervision of a U.S. court and the control of one or more United States persons (within the meaning of Section 7701(a)(30) of the Code) or (2) has made a valid election under applicable Treasury Regulations to continue to be treated as a United States person.

Distributions

        We do not anticipate declaring or paying dividends to holders of our common stock in the foreseeable future. However, if we make distributions on our common stock, such distributions of cash or property on our common stock will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts not treated as dividends for U.S. federal income tax purposes will constitute a return of capital and first be applied against and reduce a non-U.S. holder's adjusted tax basis in its common stock, but not below zero. Any excess will be treated as capital gain and will be treated as described below in the section relating to the sale or disposition of our common stock.

        Subject to the discussion below on backup withholding and foreign accounts, dividends paid to a non-U.S. holder of our common stock that are not effectively connected with the non-U.S. holder's conduct of a trade or business within the United States will be subject to U.S. federal withholding tax at a rate of 30% of the gross amount of the dividends (or such lower rate specified by an applicable income tax treaty).

        Non-U.S. holders may be entitled to a reduction in or an exemption from withholding on dividends as a result of either (a) an applicable income tax treaty or (b) the non-U.S. holder holding our common stock in connection with the conduct of a trade or business within the United States and dividends being paid in connection with that trade or business. To claim such a reduction in or exemption from withholding, the non-U.S. holder must provide the applicable withholding agent with a properly executed (a) IRS Form W-8BEN claiming an exemption from or reduction of the withholding tax under the benefit of an income tax treaty between the United States and the country in which the non-U.S. holder resides or is established, or (b) IRS Form W-8ECI stating that the dividends are not subject to withholding tax because they are effectively connected with the conduct by the non-U.S. holder of a trade or business within the United States, as may be applicable. These certifications must be provided to the applicable withholding agent prior to the payment of dividends and must be updated periodically. Non-U.S. holders that do not timely provide the applicable withholding agent with the required certification, but that qualify for a reduced rate under an applicable income tax treaty, may

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obtain a refund of any excess amounts withheld under these rules by timely filing an appropriate claim for refund with the IRS.

        Subject to the discussion below on backup withholding and foreign accounts, if dividends paid to a non-U.S. holder are effectively connected with the non-U.S. holder's conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the non-U.S. holder maintains a permanent establishment in the United States to which such dividends are attributable), then, although exempt from U.S. federal withholding tax (provided the non-U.S. holder provides appropriate certification, as described above), the non-U.S. holder will be subject to U.S. federal income tax on such dividends on a net income basis at the regular graduated U.S. federal income tax rates. In addition, a non-U.S. holder that is a corporation may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on its effectively connected earnings and profits for the taxable year that are attributable to such dividends (and, if required by an applicable income tax treaty, that are attributable to a permanent establishment maintained by the corporate non-U.S. holder in the United States), as adjusted for certain items. Non-U.S. holders should consult their tax advisors regarding their entitlement to benefits under any applicable income tax treaty.

Sale or Other Taxable Disposition

        Subject to the discussions below on backup withholding and foreign accounts, a non-U.S. holder will not be subject to U.S. federal income tax on any gain realized upon the sale or other disposition of our common stock unless:

•

the gain is effectively connected with the non-U.S. holder's conduct of a trade or business within the United States (and, if required by an applicable income tax treaty, the non-U.S. holder maintains a permanent establishment in the United States to which such gain is attributable);

•

the non-U.S. holder is a nonresident alien individual present in the United States for 183 days or more during the taxable year of the disposition and certain other requirements are met; or

•

our common stock constitutes a U.S. real property interest by reason of our status as a U.S. real property holding corporation (a "USRPHC") for U.S. federal income tax purposes.

        Gain described in the first bullet point above will generally be subject to U.S. federal income tax on a net income basis at the regular graduated U.S. federal income tax rates. A non-U.S. holder that is a foreign corporation also may be subject to a branch profits tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) of a portion of its effectively connected earnings and profits for the taxable year, as adjusted for certain items.

        A non-U.S. holder described in the second bullet point above will be subject to U.S. federal income tax at a rate of 30% (or such lower rate specified by an applicable income tax treaty) on any gain derived from the disposition, which may be offset by certain U.S. source capital losses of the non-U.S. holder (even though the individual is not considered a resident of the United States) provided the non-U.S. holder has timely filed U.S. federal income tax returns with respect to such losses.

        With respect to the third bullet point above, we believe that we currently are, and expect to remain for the foreseeable future, a USRPHC for U.S. federal income tax purposes. However, so long as our common stock is "regularly traded on an established securities market," a non-U.S. holder will be subject to U.S. federal net income tax on a disposition of our common stock only if the non-U.S. holder actually or constructively holds or held (at any time during the shorter of the five-year period preceding the date of disposition or the holder's holding period) more than 5% of our common stock. If our common stock is not considered to be so traded, all non-U.S. holders would be subject to U.S. federal net income tax on disposition of our common stock and a 10% withholding tax would apply to the gross proceeds from the sale of our common stock by a non-U.S. holder.

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        Non-U.S. holders should consult their tax advisors regarding potentially applicable income tax treaties that may provide for different rules.

Information Reporting and Backup Withholding

        A non-U.S. holder will not be subject to backup withholding with respect to payments of dividends on our common stock we make to the non-U.S. holder, provided the applicable withholding agent does not have actual knowledge or reason to know such holder is a United States person and the holder certifies its non-U.S. status, such as by providing a valid IRS Form W-8BEN or W-8ECI, or other applicable certification. However, information returns will be filed with the IRS in connection with any dividends on our common stock paid to the non-U.S. holder, regardless of whether any tax was actually withheld. Copies of these information returns may also be made available under the provisions of a specific treaty or agreement to the tax authorities of the country in which the non-U.S. holder resides or is established.

        Information reporting and backup withholding may apply to the proceeds of a sale of our common stock within the United States, and information reporting may (although backup withholding generally will not) apply to the proceeds of a sale of our common stock outside the United States conducted through certain U.S.-related financial intermediaries, in each case, unless the beneficial owner certifies under penalty of perjury that it is a non-U.S. holder on IRS Form W-8BEN or other applicable form (and the payor does not have actual knowledge or reason to know that the beneficial owner is a United States person) or such owner otherwise establishes an exemption.

        Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules may be allowed as a refund or a credit against a non-U.S. holder's U.S. federal income tax liability, provided the required information is timely furnished to the IRS.

Additional Withholding Tax on Payments Made to Foreign Accounts

        Withholding taxes may be imposed under the Foreign Account Tax Compliance Act ("FATCA") on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends on, or gross proceeds from the sale or other disposition of, our common stock paid to a "foreign financial institution" or a "non-financial foreign entity" (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any "substantial United States owners" (as defined in the Code) or furnishes identifying information regarding each substantial United States owner or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. If the payee is a foreign financial institution and is subject to the diligence and reporting requirements in (1) above, it must enter into an agreement with the U.S. Department of the Treasury requiring, among other things, that it undertake to identify accounts held by certain "specified United States persons" or "United States-owned foreign entities" (each as defined in the Code), annually report certain information about such accounts and withhold 30% on payments to non-compliant foreign financial institutions and certain other account holders. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the United States governing FATCA may be subject to different rules.

        Under the applicable Treasury Regulations, withholding under FATCA generally will apply to payments of dividends on our common stock made on or after July 1, 2014 and to payments of gross proceeds from the sale or other disposition of such stock on or after January 1, 2017.

        Prospective investors should consult their tax advisors regarding the potential application of withholding under FATCA to their investment in our common stock.

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UNDERWRITING (CONFLICTS OF INTEREST)

        Citigroup Global Markets Inc., Goldman, Sachs & Co., Merrill Lynch, Pierce, Fenner & Smith, Inc., UBS Securities LLC and Wells Fargo Securities, LLC are acting as joint book-running managers of the offering and Citigroup Global Markets Inc. is acting as representative of the underwriters named below. Subject to the terms and conditions stated in the underwriting agreement dated the date of this prospectus, each underwriter named below has severally agreed to purchase, and we have agreed to sell to that underwriter, the number of shares set forth opposite the underwriter's name.

Underwriter	Number of Shares
Citigroup Global Markets Inc.
Goldman, Sachs & Co.
Merrill Lynch, Pierce, Fenner & Smith,                   Inc.
UBS Securities LLC
Wells Fargo Securities, LLC
Apollo Global Securities, LLC
RBC Capital Markets, LLC
Scotia Capital (USA) Inc.
Barclays Capital Inc.
Credit Suisse Securities (USA) LLC
Tudor, Pickering, Holt & Co. Securities, Inc.
Credit Agricole Securities (USA) Inc.
Mitsubishi UFJ Securities (USA), Inc.
Simmons & Company International
Stephens Inc.
CIBC World Markets Corp.
FBR Capital Markets & Co.
Lebenthal & Co., LLC
Total	15,789,474

        The underwriting agreement provides that the obligations of the underwriters to purchase the shares included in this offering are subject to approval of legal matters by counsel and to other conditions. The underwriters are obligated to purchase all the shares (other than those covered by the underwriters' option to purchase additional shares described below) if they purchase any of the shares.

        Shares sold by the underwriters to the public will initially be offered at the initial public offering price set forth on the cover of this prospectus. Any shares sold by the underwriters to securities dealers may be sold at a discount from the initial public offering price not to exceed $            per share. After the shares are released for sale to the public, if all the shares are not sold at the initial offering price following a bona fide effort to do so, the underwriters may change the offering price and the other selling terms. The representative has advised us that the underwriters do not intend to make sales to discretionary accounts.

        If the underwriters sell more shares than the total number set forth in the table above, the Apollo Funds have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus, to purchase up to 2,368,421 additional shares at the public offering price less the underwriting discount. The underwriters may exercise the option solely for the purpose of covering over-allotments, if any, in connection with this offering. To the extent the option is exercised, each underwriter must purchase a number of additional shares approximately proportionate to that underwriter's initial purchase commitment. Any shares issued or sold under the option will be issued and sold on the same terms and conditions as the other shares that are the subject of this offering.

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        We, our officers and directors and the Apollo Funds have agreed that, for a period of 180 days from the date of this prospectus, subject to certain exceptions, we and they will not, without the prior written consent of Citigroup, dispose of or hedge any shares or any securities convertible into or exchangeable for our common stock. Citigroup in its sole discretion may release any of the securities subject to these lock-up agreements at any time which, in the case of officers and directors, shall be with notice.

        Prior to this offering, there has been no public market for our shares. Consequently, the initial public offering price for the shares was determined by negotiations among us, the Apollo Funds as selling stockholders, and the representative. Among the factors considered in determining the initial public offering price were our results of operations, our current financial condition, our future prospects, our markets, the economic conditions in and future prospects for the industry in which we compete, our management and currently prevailing general conditions in the equity securities markets, including current market valuations of publicly traded companies considered comparable to our company. We cannot assure you, however, that the price at which the shares will sell in the public market after this offering will not be lower than the initial public offering price or that an active trading market in our shares will develop and continue after this offering.

        We have been approved to list our shares on the NYSE under the symbol "ATHL."

        The following table shows the underwriting discounts and commissions that we and the Apollo Funds as selling stockholders are to pay to the underwriters in connection with this offering. These amounts are shown assuming both no exercise and full exercise of the underwriters' option to purchase additional shares.

	Paid by Athlon		Paid by Apollo Funds
	No Exercise	Full Exercise	No Exercise	Full Exercise
Per share	$	$	$	$
Total	$	$	$	$

        We estimate that our portion of the total expenses of this offering, excluding underwriting discounts and commissions, will be approximately $5.0 million.

        In connection with the offering, the underwriters may purchase and sell shares in the open market. Purchases and sales in the open market may include short sales, purchases to cover short positions, which may include purchases pursuant to the underwriters' option to purchase additional shares, and stabilizing purchases.

•

Short sales involve secondary market sales by the underwriters of a greater number of shares than they are required to purchase in the offering.

•

"Covered" short sales are sales of shares in an amount up to the number of shares represented by the underwriters' option to purchase additional shares.

•

"Naked" short sales are sales of shares in an amount in excess of the number of shares represented by the underwriters' option to purchase additional shares.

•

Covering transactions involve purchases of shares either pursuant to the underwriters' option to purchase additional shares or in the open market in order to cover short positions.

•

To close a naked short position, the underwriters must purchase shares in the open market. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the shares in the open market after pricing that could adversely affect investors who purchase in the offering.

•

To close a covered short position, the underwriters must purchase shares in the open market or must exercise the underwriters' option to purchase additional shares. In determining the

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source of shares to close the covered short position, the underwriters will consider, among other things, the price of shares available for purchase in the open market as compared to the price at which they may purchase shares through the underwriters' option to purchase additional shares.

•

Stabilizing transactions involve bids to purchase shares so long as the stabilizing bids do not exceed a specified maximum.

        Purchases to cover short positions and stabilizing purchases, as well as other purchases by the underwriters for their own accounts, may have the effect of preventing or retarding a decline in the market price of the shares. They may also cause the price of the shares to be higher than the price that would otherwise exist in the open market in the absence of these transactions. The underwriters may conduct these transactions on the NYSE, in the over-the-counter market or otherwise. If the underwriters commence any of these transactions, they may discontinue them at any time.

Conflicts of Interest

        The underwriters are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, principal investment, hedging, financing and brokerage activities. The underwriters and their respective affiliates have in the past performed commercial banking, investment banking and advisory services for us from time to time for which they have received customary fees and reimbursement of expenses and may, from time to time, engage in transactions with and perform services for us in the ordinary course of their business for which they may receive customary fees and reimbursement of expenses. In the ordinary course of their various business activities, the underwriters and their respective affiliates, officers, directors and employees may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (which may include bank loans and/or credit default swaps) for their own account and for the accounts of their customers and may at any time hold long and short positions in such securities and instruments. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates including the Apollo Funds.

        In addition, affiliates of certain of the underwriters are lenders under our credit agreement and/or are holders of our senior notes. Certain of the underwriters or their affiliates that have a lending relationship with us routinely hedge their credit exposure to us consistent with their customary risk management policies. A typical such hedging strategy would include these underwriters or their affiliates hedging such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities. Certain of the underwriters or their affiliates were initial purchasers in our senior notes offering and received customary fees and reimbursement of expenses. In connection therewith, Apollo Global Securities, LLC, an affiliate of our sponsor, was an initial purchaser in our senior notes offering and received a portion of the gross spread of approximately $500,000. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

        Apollo Global Securities, LLC is an affiliate of our sponsor, the Apollo Funds. Since the Apollo Funds beneficially owns more than 10% of our outstanding common stock, a "conflict of interest" is deemed to exist under Rule 5121(f)(5)(B) of the Conduct Rules of the Financial Industry Regulatory Authority, or FINRA. In addition, if the Apollo Funds sell shares of common stock in this offering, the Apollo Funds, as selling stockholders, will likely receive more than 5% of the net proceeds of this offering and a "conflict of interest" will also exist under Rule 5121(f)(5)(c)(ii). Accordingly, this offering will be made in compliance with the applicable provisions of Rule 5121. Since Apollo is not primarily responsible for managing this offering, the appointment of a "qualified independent

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underwriter" is not required pursuant to Rule 5121(a)(1). As such, any underwriter that has a conflict of interest pursuant to Rule 5121 will not confirm sales to accounts in which it exercises discretionary authority without the prior written consent of the customer.

        We are a party to a Transaction Fee Agreement and a Services Agreement with Apollo, both of which were entered into on August 23, 2010. In October 2012, Apollo assigned its rights and obligations under the Transaction Fee Agreement to one of its affiliates, Apollo Global Securities, LLC. Since our inception through March 31, 2013, we have incurred transaction fees under the Transaction Fee Agreement of approximately $7.5 million in total. During the first quarter of 2013 and calendar years 2012 and 2011, we incurred approximately $405,000, $493,000 and $411,000, respectively, of advisory fees under the Services Agreement. Upon the consummation of this offering, we intend to terminate the Transaction Fee Agreement and the Services Agreement. In connection with the termination of the Services Agreement, Apollo will receive approximately $2.5 million (plus any unreimbursed expenses) from us. Such payment corresponds to the present value as of the date of termination of the aggregate annual fees that would have been payable during the remainder of the term of the Services Agreement (assuming a term ending on August 23, 2020) using a discount rate of 8.0%. No termination fee will be paid in connection with the termination of the Transaction Fee Agreement. Please read "Certain Relationships and Related Party Transactions" for further details about these arrangements.

        We and the Apollo Funds as selling stockholders have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make because of any of those liabilities.

Notice to Prospective Investors in the European Economic Area

        In relation to each member state of the European Economic Area that has implemented the Prospectus Directive (each, a relevant member state), with effect from and including the date on which the Prospectus Directive is implemented in that relevant member state (the relevant implementation date), an offer of shares described in this prospectus may not be made to the public in that relevant member state other than:

•

to any legal entity which is a qualified investor as defined in the Prospectus Directive;

•

to fewer than 100 or, if the relevant member state has implemented the relevant provision of the 2010 PD Amending Directive, 150 natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the relevant Dealer or Dealers nominated by us for any such offer; or

•

in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of shares shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Directive.

        For purposes of this provision, the expression an "offer of securities to the public" in any relevant member state means the communication in any form and by any means of sufficient information on the terms of the offer and the shares to be offered so as to enable an investor to decide to purchase or subscribe for the shares, as the expression may be varied in that member state by any measure implementing the Prospectus Directive in that member state, and the expression "Prospectus Directive" means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the relevant member state) and includes any relevant implementing measure in the relevant member state. The expression 2010 PD Amending Directive means Directive 2010/73/EU.

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        The sellers of the shares have not authorized and do not authorize the making of any offer of shares through any financial intermediary on their behalf, other than offers made by the underwriters with a view to the final placement of the shares as contemplated in this prospectus. Accordingly, no purchaser of the shares, other than the underwriters, is authorized to make any further offer of the shares on behalf of the sellers or the underwriters.

Notice to Prospective Investors in the United Kingdom

        This prospectus is only being distributed to, and is only directed at, persons in the United Kingdom that are qualified investors within the meaning of Article 2(1)(e) of the Prospectus Directive that are also (i) investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the "Order") or (ii) high net worth entities, and other persons to whom it may lawfully be communicated, falling within Article 49(2)(a) to (d) of the Order (each such person being referred to as a "relevant person"). This prospectus and its contents are confidential and should not be distributed, published or reproduced (in whole or in part) or disclosed by recipients to any other persons in the United Kingdom. Any person in the United Kingdom that is not a relevant person should not act or rely on this document or any of its contents.

Notice to Prospective Investors in France

        Neither this prospectus nor any other offering material relating to the shares described in this prospectus has been submitted to the clearance procedures of the Autorité des Marchés Financiers or of the competent authority of another member state of the European Economic Area and notified to the Autorité des Marchés Financiers. The shares have not been offered or sold and will not be offered or sold, directly or indirectly, to the public in France. Neither this prospectus nor any other offering material relating to the shares has been or will be:

•

released, issued, distributed or caused to be released, issued or distributed to the public in France; or

•

used in connection with any offer for subscription or sale of the shares to the public in France.

        Such offers, sales and distributions will be made in France only:

•

to qualified investors (investisseurs qualifiés) and/or to a restricted circle of investors (cercle restreint d'investisseurs), in each case investing for their own account, all as defined in, and in accordance with articles L.411-2, D.411-1, D.411-2, D.734-1, D.744-1, D.754-1 and D.764-1 of the French Code monétaire et financier;

•

to investment services providers authorized to engage in portfolio management on behalf of third parties; or

•

in a transaction that, in accordance with article L.411-2-II-1°-or-2°-or 3° of the French Code monétaire et financier and article 211-2 of the General Regulations (Règlement Général) of the Autorité des Marchés Financiers, does not constitute a public offer (appel public à l'épargne).

        The shares may be resold directly or indirectly, only in compliance with articles L.411-1, L.411-2, L.412-1 and L.621-8 through L.621-8-3 of the French Code monétaire et financier.

Notice to Prospective Investors in Hong Kong

        The shares may not be offered or sold in Hong Kong by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a "prospectus" within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation

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or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares which are or are intended to be disposed of only to persons outside Hong Kong or only to "professional investors" within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Notice to Prospective Investors in Japan

        The shares offered in this prospectus have not been and will not be registered under the Financial Instruments and Exchange Law of Japan. The shares have not been offered or sold and will not be offered or sold, directly or indirectly, in Japan or to or for the account of any resident of Japan (including any corporation or other entity organized under the laws of Japan), except (i) pursuant to an exemption from the registration requirements of the Financial Instruments and Exchange Law and (ii) in compliance with any other applicable requirements of Japanese law.

Notice to Prospective Investors in Singapore

        This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the shares may not be circulated or distributed, nor may the shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the "SFA"), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

        Where the shares are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

•

a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

•

a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

shares, debentures and units of shares and debentures of that corporation or the beneficiaries' rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the shares pursuant to an offer made under Section 275 of the SFA except:

•

to an institutional investor (for corporations, under Section 274 of the SFA) or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than S$200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets, and further for corporations, in accordance with the conditions specified in Section 275 of the SFA;

•

where no consideration is or will be given for the transfer; or

•

where the transfer is by operation of law.

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Notice to Prospective Investors in Australia

        No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission, in relation to the offering. This prospectus does not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the "Corporations Act"), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

        Any offer in Australia of the shares may only be made to persons (the "Exempt Investors") who are "sophisticated investors" (within the meaning of section 708(8) of the Corporations Act), "professional investors" (within the meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the shares without disclosure to investors under Chapter 6D of the Corporations Act.

        The shares applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring shares must observe such Australian on-sale restrictions.

        This prospectus contains general information only and does not take account of the investment objectives, financial situation or particular needs of any particular person. It does not contain any securities recommendations or financial product advice. Before making an investment decision, investors need to consider whether the information in this prospectus is appropriate to their needs, objectives and circumstances, and, if necessary, seek expert advice on those matters.

Notice to Prospective Investors in the Dubai International Financial Centre

        This prospectus relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority ("DFSA"). This prospectus is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus nor taken steps to verify the information set forth herein and has no responsibility for the prospectus. The shares to which this prospectus relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares offered should conduct their own due diligence on the shares. If you do not understand the contents of this prospectus you should consult an authorized financial advisor.

Notice to Prospective Investors in Switzerland

        We have not and will not register with the Swiss Financial Market Supervisory Authority ("FINMA") as a foreign collective investment scheme pursuant to Article 119 of the Federal Act on Collective Investment Scheme of 23 June 2006, as amended ("CISA"), and accordingly the securities being offered pursuant to this prospectus have not and will not be approved, and may not be licenseable, with FINMA. Therefore, the securities have not been authorized for distribution by FINMA as a foreign collective investment scheme pursuant to Article 119 CISA and the securities offered hereby may not be offered to the public (as this term is defined in Article 3 CISA) in or from Switzerland. The securities may solely be offered to "qualified investors," as this term is defined in Article 10 CISA, and in the circumstances set out in Article 3 of the Ordinance on Collective Investment Scheme of 22 November 2006, as amended ("CISO"), such that there is no public offer. Investors, however, do not benefit from protection under CISA or CISO or supervision by FINMA. This prospectus and any other materials relating to the securities are strictly personal and confidential to each offeree and do not constitute an offer to any other person. This prospectus may only be used

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by those qualified investors to whom it has been handed out in connection with the offer described herein and may neither directly or indirectly be distributed or made available to any person or entity other than its recipients. It may not be used in connection with any other offer and shall in particular not be copied and/or distributed to the public in Switzerland or from Switzerland. This prospectus does not constitute an issue prospectus as that term is understood pursuant to Article 652a and/or 1156 of the Swiss Federal Code of Obligations. We have not applied for a listing of the securities on the SIX Swiss Exchange or any other regulated securities market in Switzerland, and consequently, the information presented in this prospectus does not necessarily comply with the information standards set out in the listing rules of the SIX Swiss Exchange and corresponding prospectus schemes annexed to the listing rules of the SIX Swiss Exchange.

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LEGAL MATTERS

        The validity of our common stock offered by this prospectus will be passed upon for us by Latham & Watkins LLP, Houston, Texas. Certain legal matters in connection with this offering will be passed upon for the underwriters by Baker Botts L.L.P., Houston, Texas.

EXPERTS

        The consolidated financial statements of Athlon Holdings LP at December 31, 2012 and 2011, and for each of the two years in the period ended December 31, 2012, appearing in this Prospectus and Registration Statement have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon appearing elsewhere herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

        The balance sheet of Athlon Energy Inc. as of April 25, 2013, appearing in this Prospectus and Registration Statement has been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon appearing elsewhere herein, and is included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

        The carve out financial statements of the Element Petroleum, LP Permian Basin Operations as of and for the nine months ended September 30, 2011 included in the registration statement of which this prospectus is a part, have been audited by UHY LLP, an independent registered public accounting firm, as set forth in their report thereon appearing elsewhere herein, and are included in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

        The information included in this prospectus regarding estimated quantities of proved reserves, the future net revenues from those reserves and their present value as of December 31, 2012 and 2011 is based on proved reserve reports prepared by Cawley, Gillespie & Associates, Inc., our independent petroleum engineers. These estimates are included in this prospectus in reliance upon the authority of such firm as an expert in these matters.

WHERE YOU CAN FIND MORE INFORMATION

        We have filed with the SEC a registration statement on Form S-1 (including the exhibits, schedules and amendments thereto) under the Securities Act, with respect to the shares of our common stock offered hereby. This prospectus does not contain all of the information set forth in the registration statement and the exhibits and schedules thereto. For further information with respect to us and the common stock offered hereby, we refer you to the registration statement and the exhibits and schedules filed therewith. Statements contained in this prospectus as to the contents of any contract, agreement or any other document are summaries of the material terms of this contract, agreement or other document. With respect to each of these contracts, agreements or other documents filed as an exhibit to the registration statement, reference is made to the exhibits for a more complete description of the matter involved. A copy of the registration statement, and the exhibits and schedules thereto, may be inspected without charge at the Public Reference Room of the SEC at 100 F Street N.E., Washington, DC 20549. Copies of these materials may be obtained from such office, upon payment of a duplicating fee. Please call the SEC at 1-800-SEC-0330 for further information on the operation of the Public Reference Room. The SEC maintains a website at www.sec.gov that contains reports, proxy and information statements and other information regarding registrants that file electronically with the SEC.

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GLOSSARY

        The terms defined in this section are used throughout this prospectus:

        "3-D seismic." Geophysical data that depict the subsurface strata in three dimensions. 3-D seismic typically provides a more detailed and accurate interpretation of the subsurface strata than 2-D, or two-dimensional, seismic.

        "Basin." A large natural depression on the earth's surface in which sediments generally brought by water accumulate.

        "Bbl." One stock tank barrel, of 42 U.S. gallons liquid volume, used in reference to crude oil, condensate or natural gas liquids.

        "Bbl/D." One Bbl per day.

        "Bcf." One billion cubic feet of natural gas.

        "BOE." One barrel of oil equivalent, with 6,000 cubic feet of natural gas being equivalent to one barrel of oil.

        "BOE/D." One barrel of oil equivalent per day.

        "British thermal unit (Btu)." The heat required to raise the temperature of a one-pound mass of water from 58.5 to 59.5 degrees Fahrenheit.

        "Cash operating expense." Equals lease operating expense plus production, severance and ad valorem tax, processing, gathering and overhead and general and administrative expense less non-cash equity-based compensation expense and acquisition costs.

        "Completion." The process of treating a drilled well followed by the installation of permanent equipment for the production of oil or natural gas, or in the case of a dry hole, the reporting of abandonment to the appropriate agency.

        "Condensate." A mixture of hydrocarbons that exists in the gaseous phase at original reservoir temperature and pressure, but that, when produced, is in the liquid phase at surface pressure and temperature.

        "Developed acreage." The number of acres that are allocated or assignable to productive wells or wells capable of production.

        "Development capital." Expenditures to obtain access to proved reserves and to construct facilities for producing, treating and storing hydrocarbons.

        "Development well." A well drilled within the proved area of an oil or natural gas reservoir to the depth of a stratigraphic horizon known to be productive.

        "Dry hole." A well found to be incapable of producing hydrocarbons in sufficient quantities such that proceeds from the sale of such production exceed production expenses and taxes.

        "Economically producible." A resource that generates revenue that exceeds, or is reasonably expected to exceed, the costs of the operation. For a complete definition of economically producible, refer to the SEC's Regulation S-X, Rule 4-10(a)(10).

        "Enhanced recovery." The recovery of hydrocarbons through the injection of liquids or gases into the reservoir, supplementing its natural energy. Enhanced recovery methods are often applied when production slows due to depletion of the natural pressure.

        "Estimated ultimate recovery (EUR)." The sum of gross reserves remaining as of a given date and cumulative production as of that date.

G-1

        "Exploratory well." A well drilled to find a new field or to find a new reservoir in a field previously found to be productive of oil or natural gas in another reservoir.

        "Finding and Development (F&D) costs." F&D costs are calculated by dividing the sum of property acquisition costs, exploration costs and development costs for the year, by the sum of proved reserve extensions, discoveries, acquisitions and revisions for the year.

        "Field." An area consisting of a single reservoir or multiple reservoirs all grouped on or related to the same individual geological structural feature and/or stratigraphic condition. The field name refers to the surface area, although it may refer to both the surface and the underground productive formations. For a complete definition of field, refer to the SEC's Regulation S-X, Rule 4-10(a)(15).

        "Formation." A layer of rock which has distinct characteristics that differ from nearby rock.

        "GAAP." Accounting principles generally accepted in the United States.

        "Gross acres" or "Gross wells." The total acres or wells, as the case may be, in which an entity owns a working interest.

        "Held by production acreage." Acreage covered by a mineral lease that perpetuates a company's right to operate a property as long as the property produces a minimum paying quantity of oil or gas.

        "Horizontal drilling." A drilling technique used in certain formations where a well is drilled vertically to a certain depth and then drilled at a right angle within a specified interval.

        "Infill wells." Wells drilled into the same pool as known producing wells so that oil or natural gas does not have to travel as far through the formation.

        "IRS." Internal Revenue Service.

        "Lease operating expense (LOE)." All direct and allocated indirect costs of lifting hydrocarbons from a producing formation to the surface constituting part of the current operating expenses of a working interest. Such costs include labor, superintendence, supplies, repairs, maintenance, allocated overhead charges, workover, insurance and other expenses incidental to production, but exclude lease acquisition or drilling or completion expenses.

        "LIBOR." London Interbank Offered Rate.

        "MBbl." One thousand barrels of crude oil, condensate or NGLs.

        "MBOE." One thousand barrels of oil equivalent.

        "Mcf." One thousand cubic feet of natural gas.

        "MMBOE." One million barrels of oil equivalent.

        "MMBtu." One million British thermal units.

        "MMcf." One million cubic feet of natural gas.

        "Natural gas liquids (NGLs)." The combination of ethane, propane, butane, isobutane and natural gasolines that when removed from natural gas become liquid under various levels of higher pressure and lower temperature.

        "Net acres" or "Net wells." The percentage of total acres or wells, as the case may be, an owner has out of a particular number of gross acres or wells. For example, an owner who has 50% interest in 100 gross acres owns 50 net acres.

        "Net revenue interest." An owner's interest in the revenues of a well after deducting proceeds allocated to royalty and overriding interests.

G-2

        "NYMEX." The New York Mercantile Exchange.

        "Operator." The entity responsible for the exploration, development and production of a well or lease.

        "Present value of future net revenues (PV-10)." The estimated future gross revenue to be generated from the production of proved reserves, net of estimated production and future development and abandonment costs, using prices and costs in effect at the determination date, before income taxes, and without giving effect to non-property-related expenses, discounted to a present value using an annual discount rate of 10% in accordance with the guidelines of the SEC.

        "Productive well." A well that is found to be capable of producing hydrocarbons in sufficient quantities such that proceeds from the sale of the production exceed production expenses and taxes.

        "Proved developed reserves." Proved reserves that can be expected to be recovered:

            i.  Through existing wells with existing equipment and operating methods or in which the cost of the required equipment is relatively minor compared with the cost of a new well; or

           ii.  Through installed extraction equipment and infrastructure operational at the time of the reserves estimate if the extraction is by means not involving a well.

        "Proved reserves." Those quantities of oil and natural gas, which, by analysis of geoscience and engineering data, can be estimated with reasonable certainty to be economically producible—from a given date forward, from known reservoirs, and under existing economic conditions, operating methods, and government regulations—prior to the time at which contracts providing the right to operate expire, unless evidence indicates that renewal is reasonably certain, regardless of whether deterministic or probabilistic methods are used for the estimation. The project to extract the hydrocarbons must have commenced, or the operator must be reasonably certain that it will commence, the project within a reasonable time. For a complete definition of proved oil and natural gas reserves, refer to the SEC's Regulation S-X, Rule 4-10(a)(22).

        "Proved undeveloped reserves (PUDs)." Proved reserves that are expected to be recovered from new wells on undrilled acreage, or from existing wells where a relatively major expenditure is required for recompletion.

        Reserves on undrilled acreage shall be limited to those directly offsetting development spacing areas that are reasonably certain of production when drilled, unless evidence using reliable technology exists that establishes reasonable certainty of economic producibility at greater distances.

        Undrilled locations can be classified as having undeveloped reserves only if a development plan has been adopted indicating that they are scheduled to be drilled within five years, unless the specific circumstances justify a longer time.

        Under no circumstances shall estimates for proved undeveloped reserves be attributable to any acreage for which an application of fluid injection or other improved recovery technique is contemplated, unless such techniques have been proved effective by actual projects in the same reservoir or an analogous reservoir, or by other evidence using reliable technology establishing reasonable certainty.

        "Reasonable certainty." A high degree of confidence. For a complete definition of reasonable certainty, refer to the SEC's Regulation S-X, Rule 4-10(a)(24).

        "Recompletion." The process of re-entering an existing wellbore that is either producing or not producing and completing new reservoirs in an attempt to establish or increase existing production.

G-3

        "Reliable technology." A grouping of one or more technologies (including computational methods) that have been field tested and have been demonstrated to provide reasonably certain results with consistency and repeatability in the formation being evaluated or in an analogous formation.

        "Reserve/production ratio (R/P Ratio)." The number of years proved reserves would last assuming current production continued at the January 2013 rate. This ratio is calculated by dividing annualized average daily production into the proved reserve quantity. Because production rates naturally decline over time, the R/P Ratio is not a useful estimate of how long properties should economically produce.

        "Reserves." Estimated remaining quantities of oil and natural gas and related substances anticipated to be economically producible, as of a given date, by application of development prospects to known accumulations. In addition, there must exist, or there must be a reasonable expectation that there will exist, the legal right to produce or a revenue interest in the production, installed means of delivering oil and natural gas or related substances to market and all permits and financing required to implement the project.

        "Reservoir." A porous and permeable underground formation containing a natural accumulation of producible hydrocarbons that is confined by impermeable rock or water barriers and is separate from other reservoirs.

        "Royalty." An interest in an oil and natural gas lease that gives the owner the right to receive a portion of the production from the leased acreage (or of the proceeds from the sale thereof), but does not require the owner to pay any portion of the production or development costs on the leased acreage. Royalties may be either landowner's royalties, which are reserved by the owner of the leased acreage at the time the lease is granted, or overriding royalties, which are usually reserved by an owner of the leasehold in connection with a transfer to a subsequent owner.

        "SEC." The United States Securities and Exchange Commission.

        "Spacing." The distance between wells producing from the same reservoir. Spacing is often expressed in terms of acres, e.g., 40-acre spacing, and is often established by regulatory agencies.

        "Stacked pay." Multiple geological zones that potentially contain hydrocarbons and are arranged in a vertical stack.

        "Standardized Measure." The present value of estimated future net revenue to be generated from the production of proved reserves, determined in accordance with the rules and regulations of the SEC (using 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves and costs in effect as of the date of estimation), less future development and production costs and income taxes, and discounted at 10% per annum to reflect the timing of future net revenue. Standardized Measure does not give effect to derivative transactions.

        "TD." Total depth.

        "Undeveloped acreage." Lease acreage on which wells have not been drilled or completed to a point that would permit the production of economic quantities of oil or natural gas regardless of whether such acreage contains proved reserves.

        "Wellbore." The hole drilled by the bit that is equipped for oil or gas production on a completed well. Also called well or borehole.

        "Working interest." The right granted to the lessee of a property to explore for and to produce and own oil, natural gas or other minerals. The working interest owners bear the exploration, development and operating costs on either a cash, penalty or carried basis.

        "Workover." Operations on a producing well to restore or increase production.

        "WTI." West Texas Intermediate crude oil, which is a light, sweet crude oil, characterized by an American Petroleum Institute gravity, or API gravity, between 39 and 41 and a sulfur content of approximately 0.4 weight percent that is used as a benchmark for other crude oils.

G-4

INDEX TO FINANCIAL STATEMENTS

	Page
ATHLON ENERGY INC.
BALANCE SHEET
Report of Independent Registered Public Accounting Firm	F-2
Balance Sheet as of April 25, 2013	F-3
Notes to Balance Sheet	F-4
UNAUDITED PRO FORMA FINANCIAL STATEMENTS
Introduction	F-5
Unaudited Pro Forma Balance Sheet as of March 31, 2013	F-6
Unaudited Pro Forma Statement of Operations for the Three Months Ended March 31, 2013	F-7
Unaudited Pro Forma Statement of Operations for the Year Ended December 31, 2012	F-8
Notes to Unaudited Pro Forma Financial Statements	F-9
ATHLON HOLDINGS LP
UNAUDITED CONSOLIDATED FINANCIAL STATEMENTS
Consolidated Balance Sheets as of March 31, 2013 and December 31, 2012	F-16
Consolidated Statements of Operations for the Three Months Ended March 31, 2013 and 2012	F-17
Consolidated Statement of Changes in Partners' Equity for the Three Months Ended March 31, 2013	F-18
Consolidated Statements of Cash Flows for the Three Months Ended March 31, 2013 and 2012	F-19
Notes to Consolidated Financial Statements	F-20
AUDITED CONSOLIDATED FINANCIAL STATEMENTS
Report of Independent Registered Public Accounting Firm	F-33
Consolidated Balance Sheets as of December 31, 2012 and 2011	F-34
Consolidated Statements of Operations for the Years Ended December 31, 2012 and 2011	F-35
Consolidated Statements of Changes in Partners' Equity for the Years Ended December 31, 2012 and 2011	F-36
Consolidated Statements of Cash Flows for the Years Ended December 31, 2012 and 2011	F-37
Notes to Consolidated Financial Statements	F-38
Supplementary Information	F-59
ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS
AUDITED CARVE OUT FINANCIAL STATEMENTS
Report of Independent Registered Public Accounting Firm	F-64
Carve Out Balance Sheet as of September 30, 2011	F-65
Carve Out Statement of Operations for the Nine Months Ended September 30, 2011	F-66
Carve Out Statement of Changes in Owner's Net Equity for the Nine Months Ended September 30, 2011	F-67
Carve Out Statement of Cash Flows for the Nine Months Ended September 30, 2011	F-68
Notes to Carve Out Financial Statements	F-69

F-1

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Board of Directors and Stockholders
Athlon Energy Inc.

        We have audited the accompanying balance sheet of Athlon Energy Inc. as of April 25, 2013. This balance sheet is the responsibility of the Company's management. Our responsibility is to express an opinion on this balance sheet based on our audit.

        We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the balance sheet is free of material misstatement. We were not engaged to perform an audit of the Company's internal control over financial reporting. Our audit included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Company's internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the balance sheet, assessing the accounting principles used and significant estimates made by management, and evaluating the overall balance sheet presentation. We believe that our audit provides a reasonable basis for our opinion.

        In our opinion, the balance sheet referred to above presents fairly, in all material respects, the financial position of Athlon Energy Inc. at April 25, 2013, in conformity with U.S. generally accepted accounting principles.

/s/ Ernst & Young LLP

Fort Worth, Texas
June 4, 2013

F-2

ATHLON ENERGY INC.

BALANCE SHEET

	April 25, 2013
ASSETS
Current assets:
Receivable from stockholder	$	10
Total assets	$	10
STOCKHOLDER'S EQUITY
Stockholder's equity:
Common stock, $0.01 par value, 1,000 shares authorized, issued and outstanding	$	10
Total stockholder's equity	$	10

The accompanying notes are an integral part of this balance sheet.

F-3

ATHLON ENERGY INC.

NOTES TO BALANCE SHEET

Note 1. Formation of the Company and Description of Business

        Athlon Energy Inc. (together with its subsidiaries, the "Company"), a Delaware corporation, was formed on April 1, 2013 and is currently a wholly-owned subsidiary of Athlon Holdings GP LLC (the "General Partner"), a Delaware limited liability company. Athlon Holdings LP (together with its subsidiaries, "Holdings"), a Delaware limited partnership, was formed on July 22, 2011 and is an independent exploration and production company focused on the acquisition, development and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. The General Partner serves as the general partner of Holdings.

        On April 25, 2013, the Company was authorized to issue 1,000 shares of common stock, $.01 par value, and had 1,000 shares outstanding, all of which were owned by the General Partner. On April 25, 2013, the Company had a $10 receivable from the General Partner equal to the sales price of the shares of common stock the General Partner owns.

        There were no other transactions involving the Company as of April 25, 2013.

Note 2. Subsequent Events

        The Company intends to offer shares of common stock to the public in an offering registered under the Securities Act of 1933, as amended.

        Subsequent to April 25, 2013, the Company collected the $10 receivable from the General Partner.

        On April 26, 2013, Holdings underwent a corporate reorganization and as a result, the Company became the holding company of Holdings. The Company will operate and control all of the business and affairs and consolidate the financial results of Holdings. In the reorganization, Apollo Investment Fund VII, L.P. and its parallel funds (the "Apollo Funds") entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Holdings for common stock of the Company. The remaining holders of Class A limited partner interests in Holdings have not exchanged their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Holdings exchanged their interests for common stock of the Company subject to the same vesting terms.

        Subsequent events have been considered through June 4, 2013, the date the balance sheet was issued.

F-4

ATHLON ENERGY INC.

UNAUDITED PRO FORMA FINANCIAL STATEMENTS

INTRODUCTION

        Athlon Energy Inc. (the "Company") incorporated in Delaware on April 1, 2013 and is an independent exploration and production company focused on the acquisition, development, and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. The Company plans to pursue an initial public offering of shares of common stock (the "Offering"). The accompanying unaudited pro forma financial statements give effect to the following transactions:

•

the issuance of $500 million of 7³/8% Senior Notes due 2021 on April 17, 2013 (the "Notes") and the application of the net proceeds received thereby to (1) repay a portion of indebtedness outstanding under the Company's credit agreement, (2) repay in full and terminate the Company's former second lien term loan, and (3) make a distribution to Athlon Holdings LP's Class A limited partners;

•

the reorganization of the Company as described in "Corporate Reorganization"; and

•

the completion of the Offering and the use of proceeds from the Offering as described in "Use of Proceeds".

The unaudited pro forma balance sheet assumes that the transactions occurred on March 31, 2013. The unaudited pro forma statements of operations assumes that the transactions occurred on January 1, 2012.

        The Company's accounting predecessor, Athlon Holdings LP ("Holdings"), conducted its operations as a limited partnership with all earnings taxed at the partner level. Following its corporate reorganization, the Company will be subject to subchapter C of the Internal Revenue Code and, as a result, will become taxable as a corporation and subject to U.S. federal and state income taxes at the entity level.

        The accompanying unaudited pro forma financial statements of the Company should be read together with the audited consolidated financial statements of Holdings as of and for the years ended December 31, 2012 and 2011 and the unaudited consolidated financial statements of Holdings as of March 31, 2013 and for the three months ended March 31, 2013 and 2012, both of which are included elsewhere in this prospectus. The accompanying unaudited pro forma financial statements of the Company were derived by making certain adjustments to the consolidated financial statements of Holdings. The adjustments are based on currently available information and certain estimates and assumptions. Therefore, the actual adjustments may differ from the pro forma adjustments. However, management believes that the assumptions provide a reasonable basis for presenting the significant effects of the transactions as contemplated and that the pro forma adjustments give appropriate effect to those assumptions and are properly applied in the unaudited pro forma financial statements.

        The unaudited pro forma financial statements and related notes are presented for illustrative purposes only. If the Offering and other transactions contemplated herein had occurred in the past, the Company's operating results might have been materially different from those presented in the unaudited pro forma financial statements. The unaudited pro forma financial statements should not be relied upon as an indication of operating results that the Company would have achieved if the Offering and other transactions contemplated herein had taken place on the specified date. In addition, future results may vary significantly from the results reflected in the unaudited pro forma financial statements of operations and should not be relied on as an indication of the future results the Company will have after the completion of the Offering and the other transactions contemplated by these unaudited pro forma financial statements.

F-5

ATHLON ENERGY INC.

UNAUDITED PRO FORMA BALANCE SHEET

March 31, 2013

(in thousands)

	Athlon Holdings LP Historical			Notes Offering Pro Forma Adjustments			Corporate Reorganization Pro Forma Adjustments			Initial Public Offering Pro Forma Adjustments			Pro Forma as Adjusted
ASSETS
Current assets:
Cash and cash equivalents	$	3,379		$	487,458	(a)	$	—		$	278,895	(g)	$	275,103
					(488,253	)(b)					(3,173	)(h)
					(703	)(c)					(2,500	)(j)
Accounts receivable		33,149			—			—			—			33,149
Inventory		1,023			—			—			—			1,023
Other		781			—			—			—			781
Total current assets		38,332			(1,498	)		—			273,222			310,056
Properties and equipment, at cost—full cost method:
Proved properties, including wells and related equipment		864,350			—			—			377	(k)		864,727
Unproved properties		95,892			—			—			—			95,892
Accumulated depletion, depreciation, and amortization		(91,829	)		—			—			—			(91,829	)
		868,413			—			—			377			868,790
Derivatives		2,204			—			—			—			2,204
Debt issuance costs		5,906			12,542	(a)		—			—			15,591
					(2,857	)(d)
Other		1,680			—			—			(395	)(i)		1,285
Total assets	$	916,535		$	8,187		$	—		$	273,204		$	1,197,926
LIABILITIES AND EQUITY
Current liabilities:
Accounts payable:
Trade	$	250		$	—		$	—		$	—		$	250
Affiliate		538			—			—			—			538
Accrued liabilities:
Lease operating		4,460			—			—			—			4,460
Production, severance, and ad valorem taxes		2,459			—			—			—			2,459
Development capital		29,986			—			—			—			29,986
Derivatives		4,599			—			—			—			4,599
Revenue payable		12,842			—			—			—			12,842
Other		3,232			(703	)(c)		—			—			2,529
Total current liabilities		58,366			(703	)		—			—			57,663
Derivatives		324			—			—			—			324
Asset retirement obligations, net of current portion		5,600			—			—			—			5,600
Long-term debt		416,426			500,000	(a)		—			(3,173	)(h)		500,000
					(413,253	)(b)
Deferred tax liability		2,361			—			19,002	(f)		—			21,363
Other		128			—			—			—			128
Total liabilities		483,205			86,044			19,002			(3,173	)		585,078
Commitments and contingencies
Equity:
Preferred stock		—			—			—			—			—
Common stock		—			—			10	(e)		158	(g)		821
											653	(1)
Additional paid-in capital		—			—			346,034	(e)		278,737	(g)		625,371
											(395	)(i)
											1,648	(k)
											(653	)(1)
Partners' capital		433,330			(75,000	)(b)		(355,473	)(e)		—			—
					(2,857	)(d)
Accumulated deficit		—			—			(19,002	)(f)		(2,500	)(j)		(22,773	)
											(1,271	)(k)
Total stockholders' equity		433,330			(77,857	)		(28,431	)		276,377			603,419
Noncontrolling interest		—			—			9,429	(e)		—			9,429
Total equity		433,330			(77,857	)		(19,002	)		276,377			612,848
Total liabilities and equity	$	916,535		$	8,187		$	—		$	273,204		$	1,197,926

The accompanying notes are an integral part of these unaudited pro forma financial statements.

F-6

ATHLON ENERGY INC.

UNAUDITED PRO FORMA STATEMENT OF OPERATIONS

For the Three Months Ended March 31, 2013

(in thousands)

	Athlon Holdings LP Historical		Notes Offering Pro Forma Adjustments			Corporate Reorganization Pro Forma Adjustments			Initial Public Offering Pro Forma Adjustments			Pro Forma as Adjusted
Revenues:
Oil	$	45,659	$	—		$	—		$	—		$	45,659
Natural gas		3,367		—			—			—			3,367
Natural gas liquids		5,720		—			—			—			5,720
Total revenues		54,746		—			—			—			54,746
Expenses:
Production:
Lease operating		7,237		—			—			—			7,237
Production, severance, and ad valorem taxes		3,694		—			—			—			3,694
Depletion, depreciation, and amortization		18,053		—			—			—			18,053
General and administrative		3,339		—			—			—			3,339
Derivative fair value loss		6,849		—			—			—			6,849
Other operating		194		—			—			—			194
Total expenses		39,366		—			—			—			39,366
Operating income (loss)		15,380		—			—			—			15,380
Interest expense		4,474		9,614	(a)		—			—			9,976
				(4,112)	(b)
Income (loss) before income taxes		10,906		(5,502	)		—			—			5,404
Income tax provision		27		—			1,994	(c)		—			2,021
Consolidated net income (loss)		10,879		(5,502	)		(1,994	)		—			3,383
Less: net income (loss) attributable to noncontrolling interest		—		—			168	(d)		(50)	(e)		118
Net income (loss) attributable to stockholders	$	10,879	$	(5,502	)	$	(2,162	)	$	50		$	3,265
Net income (loss) per common share (f):
Basic												$	0.05
Diluted												$	0.05
Weighted average common shares outstanding (f):
Basic													66,333
Diluted													68,195

The accompanying notes are an integral part of these unaudited pro forma financial statements.

F-7

ATHLON ENERGY INC.

UNAUDITED PRO FORMA STATEMENT OF OPERATIONS

For the Year Ended December 31, 2012

(in thousands)

	Athlon Holdings LP Historical			Notes Offering Pro Forma Adjustments			Corporate Reorganization Pro Forma Adjustments			Initial Public Offering Pro Forma Adjustments			Pro Forma as Adjusted
Revenues:
Oil	$	128,081		$	—		$	—		$	—		$	128,081
Natural gas		8,415			—			—			—			8,415
Natural gas liquids		20,615			—			—			—			20,615
Total revenues		157,111			—			—			—			157,111
Expenses:
Production:
Lease operating		25,503			—			—			—			25,503
Production, severance, and ad valorem taxes		10,438			—			—			—			10,438
Depletion, depreciation, and amortization		54,456			—			—			—			54,456
General and administrative		9,678			—			—			—			9,678
Acquisitions costs		876			—			—			—			876
Derivative fair value gain		(9,293	)		—			—			—			(9,293	)
Other operating		562			—			—			—			562
Total expenses		92,220			—			—			—			92,220
Operating income (loss)		64,891			—			—			—			64,891
Interest expense		9,949			39,096	(a)		—			—			40,590
					(8,455	)(b)
Income (loss) before income taxes		54,942			(30,641	)		—			—			24,301
Income tax provision		1,928			—			7,158	(c)		—			9,086
Consolidated net income (loss)		53,014			(30,641	)		(7,158	)		—			15,215
Less: net income (loss) attributable to noncontrolling interest		—			—			753	(d)		(224)	(e)		529
Net income (loss) attributable to stockholders	$	53,014		$	(30,641	)	$	(7,911	)	$	224		$	14,686
Net income (loss) per common share (f):
Basic													$	0.22
Diluted													$	0.22
Weighted average common shares outstanding (f):
Basic														66,333
Diluted														68,195

The accompanying notes are an integral part of these unaudited pro forma financial statements.

F-8

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS

Note 1. Basis of Presentation, the Offering, and Other Transactions

        The historical financial information is derived from the consolidated financial statements of Holdings included elsewhere in this prospectus. For purposes of the unaudited pro forma balance sheet, it is assumed that the transactions had taken place on March 31, 2013. For purposes of the unaudited pro forma statements of operations, it is assumed all transactions had taken place on January 1, 2012.

        Upon closing of the Offering, the Company expects to incur direct, incremental general and administrative expenses as a result of being a publicly traded company, including, but not limited to, costs associated with annual and quarterly reports to stockholders, tax return preparation, independent auditor fees, investor relations activities, registrar and transfer agent fees, incremental director and officer liability insurance costs, and independent director compensation. The Company estimates these direct, incremental general and administrative expenses initially to total approximately $2.0 million per year. These direct, incremental general and administrative expenditures are not reflected in the historical consolidated financial statements or in the unaudited pro forma financial statements.

        Upon closing of the Offering, the limited partnership agreement of Holdings will be amended and restated to, among other things, modify Holdings' capital structure by replacing its different classes of interests with a single new class of units that we refer to as the "New Holdings Units." The members of the Company's management team and certain employees that hold Class A limited partner interests will own New Holdings Units and will enter into an exchange agreement under which (subject to the terms of the exchange agreement) they will have the right, under certain circumstances, to exchange their New Holdings Units for shares of the Company's common stock on a one-for-one basis, subject to customary conversion rate adjustments for stock splits, stock dividends, and reclassifications. All other New Holdings Units will be held by the Company. As a holder exchanges its New Holdings Units, the Company's interest in Holdings will be correspondingly increased.

        The Company will enter into a tax receivable agreement for the benefit of the holders of New Holdings Units. Future exchanges of New Holdings Units for the Company's common stock under the exchange agreement are expected to result in increases in the tax basis of Holdings' assets that otherwise would not have been available. Depletion from the increase in tax basis will be available, subject to limitations, to reduce the amount of tax that the Company would be required to pay in the future.

        Under the tax receivable agreement, the Company will agree to pay to the holders of New Holdings Units (or certain permitted transferees thereof) 85% of the actual reduction in U.S. federal, state, and local tax payments that the Company is deemed to realize as a result of increases in tax basis and certain other tax benefits related to exchanges of New Holdings Units pursuant to the exchange agreement, including tax benefits attributable to payments under the tax receivable agreement. The beneficiaries under the tax receivable agreement will not reimburse the Company for any payments previously made under the tax receivable agreement if such benefits are subsequently disallowed, although future payments would be adjusted to the extent possible to reflect the result of such disallowance. As a result, in certain circumstances, payments could be made under the tax receivable agreement in excess of the Company's reported deferred tax assets. The obligation to pay 85% of the amount of such cash savings to the holders of New Holdings Units is the Company's obligation, and not the obligation of Holdings or any other subsidiary. Please read "Corporate Reorganization" and "Certain Relationships and Related Party Transactions—Tax Receivable Agreement."

        The step-up in basis will depend on the fair value of the New Holdings Units at conversion. There is no intent of the holders of New Holdings Units to exchange their units for shares of the Company's common stock in the foreseeable future. In addition, the Company does not expect to be in a tax

F-9

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 1. Basis of Presentation, the Offering, and Other Transactions (Continued)

paying position before 2019. Therefore, the Company cannot presently estimate what the benefit or payments under the tax receivable agreement will be on a factually supportable basis. If the tax receivable agreement were terminated immediately after the Offering, the Company estimates it would be required to make an early termination payment of approximately $5.3 million to the holders of the New Holdings Units.

Note 2. Pro Forma Adjustments and Assumptions

        The Company made the following adjustments and assumptions in the preparation of the unaudited pro forma balance sheet:

(a)

Reflects gross proceeds of $500 million from the issuance of the Notes, net of underwriting discounts and commissions of $10 million, in the aggregate, and additional debt issuance costs of approximately $2.5 million.



(b)

Reflects the use of net proceeds from the issuance of the Notes and cash on hand to (1) repay approximately $288.3 million of outstanding borrowings under the Company's credit agreement, (2) repay in full and terminate the Company's former second lien term loan of $125 million, and (3) make a $75 million distribution to Holdings' Class A limited partners.



(c)

Reflects the use of net proceeds from the issuance of the Notes to pay approximately $0.7 million of accrued interest on the Company's former second lien term loan.



(d)

Reflects the write off of approximately $2.9 million of debt issuance costs related to (1) the reduction in the borrowing base under the Company's credit agreement from $360 million to $267.5 million in connection with the issuance of the Notes and (2) the repayment in full and termination of the Company's former second lien term loan. The write off of debt issuance costs related to the Company's credit agreement was a result of a decrease in borrowing capacity as determined in accordance with ASC 470-50, "Debt—Modifications and Extinguishments—Derecognition".



(e)

Reflects (1) the issuance of 860,907 shares of common stock to Apollo in exchange for their Class A limited partner interest in Holdings, (2) the issuance of 100,000 shares of common stock to the Company's management and certain employees in exchange for their Class B limited partner interests in Holdings, (3) the reclassification of management's Class A limited partner interests in Holdings to noncontrolling interest of the Company, and (4) the reclassification of the Company's predecessor's retained earnings to additional paid-in capital. The 100,000 shares of common stock issued to the Company's management and certain employees in exchange for their Class B limited partner interests in Holdings are subject to the same vesting and performance terms as the original grant.



(f)

Reflects estimated change in long-term deferred tax liabilities for temporary differences between the historical cost basis and tax basis of the Company's assets and liabilities as the result of its change in tax status to a subchapter C corporation. A corresponding charge to earnings has not been reflected in the unaudited pro forma statement of operations as the charge is considered non-recurring.



(g)

Reflects estimated gross proceeds of $300 million from the issuance and sale of 15,789,474 shares of common stock at an assumed initial public offering price of $19.00 per share, net of estimated underwriting discounts and commissions of $16.5 million, in the aggregate, and additional estimated expenses related to the Offering of approximately

F-10

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 2. Pro Forma Adjustments and Assumptions (Continued)

$4.6 million. The following table provides a reconciliation of the pro forma cash expected to be received upon consummation of the Offering and the net proceeds from the Offering as disclosed throughout this registration statement (in millions):

Gross proceeds from the Offering	$	300.0
Estimated underwriting discounts and commissions		16.5
Additional estimated Offering expenses		4.6
Pro forma cash expected to be received from the Offering		278.9
Offering expenses incurred prior to March 31, 2013		0.4
Net proceeds from the Offering	$	278.5

(h)

Reflects the use of a portion of the net proceeds from the Offering to repay approximately $3.2 million of remaining outstanding borrowings under the Company's credit agreement.



(i)

Reflects the reclassification of expenses related to the Offering incurred prior to March 31, 2013 of approximately $0.4 million.



(j)

Reflects the termination of the Company's Services Agreement, dated August 23, 2010, and, in connection with the termination, the payment to Apollo of approximately $2.5 million. Such payment corresponds to the present value as of the date of termination of the aggregate annual fees that would have been payable during the remainder of the term of the Services Agreement (assuming a term ending on August 23, 2020) using a discount rate of 8.0%. This adjustment is not reflected in the accompanying unaudited pro forma statements of operations as it is considered non-recurring.



(k)

Reflects the recognition of the remaining unrecognized equity-based compensation related to the 100,000 shares of common stock which were issued to the Company's management in exchange for their Class B limited partner interests in Holdings. The terms of the underlying agreements cause the awards to immediately vest upon the closing of the Offering. Includes the estimated grant date fair value of 2,725 Class B limited partner interests granted during April 2013. This adjustment is not reflected in the accompanying unaudited pro forma statements of operations as it is considered non-recurring.



(l)

Reflects the stock split for shares held by the Company's existing stockholders prior to the consummation of this Offering.

        The Company made the following adjustments and assumptions in the preparation of the unaudited pro forma statements of operations:

(a)

Reflects estimated incremental interest expense and amortization of debt issuance costs associated with the issuance of the Notes.



(b)

Reflects (1) the elimination of interest expense and amortization of debt issuance costs related to the Company's former second lien term loan, which was repaid in full and terminated in connection with the issuance of the Notes, and (2) the reduction in interest expense under the Company's credit agreement, partially offset by an increase in unused commitment fees. On a pro forma basis, there would have been no outstanding borrowings under the Company's credit agreement as of January 1, 2012.

F-11

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 2. Pro Forma Adjustments and Assumptions (Continued)

A ¹/8% change in LIBOR would have had no effect on our interest expense as we would have had no outstanding variable rate debt during the periods presented on a pro forma basis.

(c)

Reflects estimated incremental income tax provision associated with the Company's historical results of operations and the Notes Offering pro forma adjustments assuming the Company's earnings had been subject to federal income tax as a subchapter C corporation using an effective tax rate of approximately 37.4%. This rate is inclusive of federal, state, and local income taxes.



(d)

Reflects the reduction in consolidated net income (loss) attributable to noncontrolling interest for the Company's historical results of operations and the Notes Offering pro forma adjustments. As described in "Corporate Reorganization", the Company has become the sole managing partner of Holdings and will initially own less than 100% of the economic interest in Holdings, but will have 100% of the voting power and control the management of Holdings. Upon completion of the Company's reorganization, the noncontrolling interest was approximately 3.2%.



(e)

Reflects the reduction in consolidated net income (loss) attributable to noncontrolling interest for the change in noncontrolling interest percentage as a result of the Offering. Upon consummation of the Offering, additional shares of common stock will be issued to Apollo, the Company's management and certain employees, and the investors in the Offering resulting in an increase in the Company's ownership percentage of Holdings. This will reduce the noncontrolling interest from approximately 3.2% to approximately 2.2%.



(f)

Reflects basic and diluted income per common share for the issuance of shares of common stock in the Offering. Please read "Note 3. Pro Forma Earnings Per Share" for additional discussion.

F-12

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 3. Pro Forma Earnings Per Share

        The following table reflects the pro forma allocation of net income to the Company's common stockholders and earnings per share ("EPS") computations for the periods indicated:

	Three months ended March 31, 2013		Year ended December 31, 2012
	(in thousands, except per share amounts)
Basic EPS
Numerator:
Basic net income attributable to stockholders	$	3,265	$	14,686
Denominator:
Basic weighted average shares outstanding		66,333		66,333
Basic EPS attributable to stockholders	$	0.05	$	0.22
Diluted EPS
Numerator:
Net income attributable to stockholders	$	3,265	$	14,686
Effect of conversion of New Holdings Units to shares of the Company's common stock		118		529
Diluted net income attributable to stockholders	$	3,383	$	15,215
Denominator:
Basic weighted average shares outstanding		66,333		66,333
Effect of conversion of New Holdings Units to shares of the Company's common stock		1,862		1,862
Diluted weighted average shares outstanding		68,195		68,195
Diluted EPS attributable to stockholders	$	0.05	$	0.22

        If the Company included the shares of common stock issued in the Offering in the above pro forma EPS calculations, basic weighted average shares outstanding for the three months ended March 31, 2013 and for the year ended December 31, 2012 would be 83,123,000 with a corresponding basic EPS attributable to stockholders of $0.04 per share and $0.18 per share, respectively, and diluted weighted average shares outstanding for the three months ended March 31, 2013 and for the year ended December 31, 2012 would be 83,985,000 with a corresponding diluted EPS attributable to stockholders of $0.04 per share and $0.18 per share, respectively.

Note 4. Supplementary Information

        The following pro forma standardized measure of the discounted net future cash flows and changes applicable to the Company's proved reserves reflect the effect of income taxes assuming the Company's standardized measure had been subject to federal income tax as a subchapter C corporation. The future cash flows are discounted at 10% per year and assume continuation of existing economic conditions.

        The standardized measure of discounted future net cash flows, in management's opinion, should be examined with caution. The basis for this table is the reserve studies prepared by independent petroleum engineering consultants, which contain imprecise estimates of quantities and rates of production of reserves. Revisions of previous year estimates can have a significant impact on these

F-13

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 4. Supplementary Information (Continued)

results. Also, exploration costs in one year may lead to significant discoveries in later years and may significantly change previous estimates of proved reserves and their valuation. Therefore, the standardized measure of discounted future net cash flow is not necessarily indicative of the fair value of the Company's proved oil and natural gas properties.

        The data presented should not be viewed as representing the expected cash flow from or current value of, existing proved reserves since the computations are based on a large number of estimates and arbitrary assumptions. Reserve quantities cannot be measured with precision and their estimation requires many judgmental determinations and frequent revisions. Actual future prices and costs are likely to be substantially different from the prices and costs utilized in the computation of reported amounts.

        The Company's pro forma standardized measure of discounted estimated future net cash flows was as follows as of December 31, 2012:

	Athlon Holdings LP Historical			Reorganization Pro Forma Adjustments			Pro Forma as Adjusted
	(in thousands)
Future cash inflows	$	5,361,058		$	—		$	5,361,058
Future production costs		(1,811,514	)		—			(1,811,514	)
Future development costs		(1,060,785	)		—			(1,060,785	)
Future income taxes		(37,527	)		(677,762	)		(715,289	)
Future net cash flows		2,451,232			(677,762	)		1,773,470
10% annual discount		(1,600,318	)		429,334			(1,170,984	)
Standardized measure of discounted estimated future net cash flows	$	850,914		$	(248,428	)	$	602,486

F-14

ATHLON ENERGY INC.

NOTES TO UNAUDITED PRO FORMA FINANCIAL STATEMENTS (Continued)

Note 4. Supplementary Information (Continued)

        The changes in Holdings' pro forma standardized measure of discounted estimated future net cash flows were as follows for 2012:

	Athlon Holdings LP Historical			Reorganization Pro Forma Adjustments			Pro Forma as Adjusted
	(in thousands)
Net change in prices and production costs	$	(109,214	)	$	—		$	(109,214	)
Purchases of minerals-in-place		81,304			—			81,304
Extensions, discoveries, and improved recovery		376,493			—			376,493
Revisions of previous quantity estimates		(189,505	)		—			(189,505	)
Production, net of production costs		(121,170	)		—			(121,170	)
Previously estimated development costs incurred during the period		119,361			—			119,361
Accretion of discount		59,144			—			59,144
Change in estimated future development costs		60,210			—			60,210
Net change in income taxes		(5,378	)		(95,776	)		(101,154	)
Change in timing and other		(1,488	)		—			(1,488	)
Net change in standardized measure		269,757			(95,776	)		173,981
Standardized measure, beginning of year		581,157			(152,652	)		428,505
Standardized measure, end of year	$	850,914		$	(248,428	)	$	602,486

F-15

ATHLON HOLDINGS LP
CONSOLIDATED BALANCE SHEETS
(in thousands)

	March 31, 2013			December 31, 2012
	(unaudited)
ASSETS
Current assets:
Cash and cash equivalents	$	3,379		$	8,871
Accounts receivable		33,149			24,501
Derivatives		—			2,246
Inventory		1,023			1,022
Other		781			2,486
Total current assets		38,332			39,126
Properties and equipment, at cost—full cost method:
Proved properties, including wells and related equipment		864,350			788,571
Unproved properties		95,892			89,860
Accumulated depletion, depreciation, and amortization		(91,829	)		(73,824	)
		868,413			804,607
Derivatives		2,204			2,854
Debt issuance costs		5,906			4,418
Other		1,680			1,293
Total assets	$	916,535		$	852,298
LIABILITIES AND PARTNERS' EQUITY
Current liabilities:
Accounts payable:
Trade	$	250		$	3,170
Affiliate		538			935
Accrued liabilities:
Lease operating		4,460			3,858
Production, severance, and ad valorem taxes		2,459			1,307
Development capital		29,986			39,483
Derivatives		4,599			592
Revenue payable		12,842			9,330
Other		3,232			2,700
Total current liabilities		58,366			61,375
Derivatives		324			519
Asset retirement obligations, net of current portion		5,600			5,049
Long-term debt		416,426			362,000
Other		2,489			2,478
Total liabilities		483,205			431,421
Commitments and contingencies
Partners' equity		433,330			420,877
Total liabilities and partners' equity	$	916,535		$	852,298

The accompanying notes are an integral part of these consolidated financial statements.

F-16

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands)

(unaudited)

	Three months ended March 31,
	2013		2012
Revenues:
Oil	$	45,659	$	27,433
Natural gas		3,367		1,448
Natural gas liquids		5,720		4,351
Total revenues		54,746		33,232
Expenses:
Production:
Lease operating		7,237		4,699
Production, severance, and ad valorem taxes		3,694		2,350
Depletion, depreciation, and amortization		18,053		9,614
General and administrative		3,339		2,597
Derivative fair value loss		6,849		22,711
Other operating		194		130
Total expenses		39,366		42,101
Operating income (loss)		15,380		(8,869	)
Interest expense		4,474		1,495
Income (loss) before income taxes		10,906		(10,364	)
Income tax provision (benefit)		27		(364	)
Net income (loss)	$	10,879	$	(10,000	)

The accompanying notes are an integral part of these consolidated financial statements.

F-17

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY

(in thousands)

(unaudited)

	Total Partner's Equity
Balance at December 31, 2012	$	420,877
Capital contributions and equity-based compensation		1,574
Net income		10,879
Balance at March 31, 2013	$	433,330

The accompanying notes are an integral part of these consolidated financial statements.

F-18

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

(unaudited)

	Three months ended March 31,
	2013			2012
Cash flows from operating activities:
Net income (loss)	$	10,879		$	(10,000	)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depletion, depreciation, and amortization		18,053			9,614
Deferred taxes		27			(364	)
Non-cash derivative loss		6,708			20,118
Equity-based compensation		48			58
Other		438			300
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable		(8,648	)		(3,021	)
Other current assets		219			319
Accounts payable		(2,253	)		4,712
Revenue payable		3,010			948
Other current liabilities		1,916			(1,961	)
Net cash provided by operating activities		30,397			20,723
Cash flows from investing activities:
Acquisitions of oil and natural gas properties		(8,819	)		(1,239	)
Development of oil and natural gas properties		(81,605	)		(57,120	)
Other		(136	)		(139	)
Net cash used in investing activities		(90,560	)		(58,498	)
Cash flows from financing activities:
Proceeds from long-term debt, net of issuance costs		53,271			21,816
Payments on long-term debt		—			(9,000	)
Other		1,400			166
Net cash provided by financing activities		54,671			12,982
Decrease in cash and cash equivalents		(5,492	)		(24,793	)
Cash and cash equivalents, beginning of period		8,871			32,030
Cash and cash equivalents, end of period	$	3,379		$	7,237

The accompanying notes are an integral part of these consolidated financial statements.

F-19

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

(unaudited)

Note 1. Formation of the Partnership and Description of Business

        Athlon Holdings LP (together with its subsidiaries, "Holdings"), a Delaware limited partnership, is an independent exploration and production company focused on the acquisition, development, and exploitation of unconventional oil and liquids-rich natural gas reserves in the Permian Basin. Holdings was formed on July 22, 2011, and is the holding company for Athlon Energy LP, a Delaware limited partnership, which was formed on August 5, 2010, and Athlon FE Energy LP, a Delaware limited partnership, which was formed on July 22, 2011. Athlon Holdings GP LLC serves as the general partner to Holdings with no obligations to make capital contributions and no rights to distributions.

        As of March 31, 2013, Holdings was a party to a limited partnership agreement with its management group and Apollo Athlon Holdings LLC ("Apollo"), which is an affiliate of Apollo Global Management, LLC. Apollo has a controlling influence over Holdings. As of March 31, 2013, Apollo Investment Fund VII, L.P. and its parallel funds (the "Apollo Funds"), members of Holdings' management team, and certain employees owned all of the Class A limited partner interests in Holdings and members of Holdings' management team and certain employees own all of the Class B limited partner interests in Holdings. Please read "Note 6. Partners' Equity" and "Note 7. Class B Limited Partner Interests" for additional discussion.

        Athlon Energy Inc. ("Athlon") was formed on April 1, 2013. On April 26, 2013, Holdings underwent a corporate reorganization and as a result, Athlon became the holding company of Holdings. Athlon will operate and control all of the business and affairs and consolidate the financial results of Holdings. In the reorganization, the Apollo Funds entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Holdings for common stock of Athlon. The remaining holders of Class A limited partner interests in Holdings have not exchanged their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Holdings exchanged their interests for common stock of Athlon subject to the same vesting terms.

Note 2. Basis of Presentation

        Holdings' consolidated financial statements include the accounts of its wholly owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation.

        In the opinion of management, the accompanying unaudited consolidated financial statements include all adjustments necessary to present fairly, in all material respects, Holdings financial position as of March 31, 2013 and results of operations and cash flows for the three months ended March 31, 2013 and 2012. All adjustments are of a normal recurring nature. These interim results are not necessarily indicative of results for an entire year.

        Certain amounts and disclosures have been condensed and omitted from the unaudited consolidated financial statements pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (the "SEC"). Therefore, these unaudited consolidated financial statements should be read in conjunction with Holdings' audited consolidated financial statements and related notes thereto.

F-20

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 2. Basis of Presentation (Continued)

New Accounting Pronouncements

        In December 2011, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") 2011-11, "Disclosures about Offsetting Assets and Liabilities" and in January 2013 issued ASU 2013-01, "Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities". These ASUs created new disclosure requirements regarding the nature of an entity's rights of setoff and related arrangements associated with its derivative instruments, repurchase agreements, and securities lending transactions. Certain disclosures of the amounts of certain instruments subject to enforceable master netting arrangements are required, irrespective of whether the entity has elected to offset those instruments in the statement of financial position. These ASUs were effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of these ASUs did not impact Holdings' financial position, results of operations, or liquidity.

        No other new accounting pronouncements issued or effective during the three months ended March 31, 2013, or from March 31, 2013 through the date of this Report, had or are expected to have a material impact on Holdings' unaudited consolidated financial statements.

Note 3. Commitments and Contingencies

        Holdings is a party to ongoing legal proceedings in the ordinary course of business. Management does not believe the results of these proceedings, individually or in the aggregate, will have a material adverse effect on Holdings' business, financial position, results of operations, or liquidity.

        Additionally, Holdings has contractual obligations related to future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal, long-term debt, commodity derivative contracts, operating leases, and development commitments.

Note 4. Asset Retirement Obligations

        Asset retirement obligations relate to future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal. The following table summarizes the changes in Holdings' asset retirement obligations for the three months ended March 31, 2013 (in thousands):

Balance at January 1	$	5,049
Acquisition of properties		265
Wells drilled		253
Accretion of discount		149
Plugging and abandonment costs incurred		(9	)
Balance at March 31	$	5,707

        As of March 31, 2013, $5.6 million of Holdings' asset retirement obligations were long-term and recorded in "Asset retirement obligations, net of current portion" and $107,000 were current and included in "Other current liabilities" in the accompanying Consolidated Balance Sheets.

F-21

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 5. Long-Term Debt

Credit Agreement

        Holdings is a party to an amended and restated credit agreement dated March 19, 2013 (the "Holdings Credit Agreement"), which matures on March 19, 2018. The Holdings Credit Agreement provides for revolving credit loans to be made to Holdings from time to time and letters of credit to be issued from time to time for the account of Holdings or any of its restricted subsidiaries. The aggregate amount of the commitments of the lenders under the Holdings Credit Agreement is $1.0 billion. Availability under the Holdings Credit Agreement is subject to a borrowing base, which is redetermined semi-annually and upon requested special redeterminations. As of March 31, 2013, the borrowing base was $360 million and there were $291.4 million of outstanding borrowings, $68.6 million of borrowing capacity, and no outstanding letters of credit under the Holdings Credit Agreement.

        Obligations under the Holdings Credit Agreement are secured by a first-priority security interest in substantially all of Holdings' proved reserves and in the equity interests of its operating subsidiaries. In addition, obligations under the Holdings Credit Agreement are guaranteed by Holdings' operating subsidiaries.

        Loans under the Holdings Credit Agreement are subject to varying rates of interest based on (1) outstanding borrowings in relation to the borrowing base and (2) whether the loan is a Eurodollar loan or a base rate loan. Eurodollar loans under the Holdings Credit Agreement bear interest at the Eurodollar rate plus the applicable margin indicated in the following table, and base rate loans under the Holdings Credit Agreement bear interest at the base rate plus the applicable margin indicated in the following table. Holdings also incurs a quarterly commitment fee on the unused portion of the Holdings Credit Agreement indicated in the following table:

Ratio of Outstanding Borrowings to Borrowing Base	Unused Commitment Fee			Applicable Margin for Eurodollar Loans			Applicable Margin for Base Rate Loans
Less than or equal to .30 to 1		0.375	%		0.50	%		1.50	%
Greater than .30 to 1 but less than or equal to .60 to 1		0.375	%		0.75	%		1.75	%
Greater than .60 to 1 but less than or equal to .80 to 1		0.50	%		1.00	%		2.00	%
Greater than .80 to 1 but less than or equal to .90 to 1		0.50	%		1.25	%		2.25	%
Greater than .90 to 1		0.50	%		1.50	%		2.50	%

        The "Eurodollar rate" for any interest period (either one, two, three, or six months, as selected by Holdings) is the rate equal to the British Bankers Association London Interbank Offered Rate ("LIBOR") for deposits in dollars for a similar interest period. The "Base Rate" is calculated as the highest of: (1) the annual rate of interest announced by Bank of America, N.A. as its "prime rate"; (2) the federal funds effective rate plus 0.5%; or (3) except during a "LIBOR Unavailability Period", the Eurodollar rate (for dollar deposits for a one-month term) for such day plus 1.0%.

        Any outstanding letters of credit reduce the availability under the Holdings Credit Agreement. Borrowings under the Holdings Credit Agreement may be repaid from time to time without penalty.

        The Holdings Credit Agreement contains covenants including, among others, the following:

•

a prohibition against incurring debt, subject to permitted exceptions;

F-22

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 5. Long-Term Debt (Continued)

•

a restriction on creating liens on Holdings' assets and the assets of its operating subsidiaries, subject to permitted exceptions;

•

restrictions on merging and selling assets outside the ordinary course of business;

•

restrictions on use of proceeds, investments, transactions with affiliates, or change of principal business;

•

a requirement that Holdings maintain a ratio of consolidated funded debt to consolidated Adjusted EBITDA (as defined in the Holdings Credit Agreement) of not more than 4.75 to 1.0 beginning with the quarter ended June 30, 2013 (which ratio changes to 4.5 to 1.0 beginning with the quarter ended June 30, 2014); and

•

a provision limiting commodity derivative contracts to a volume not exceeding 85% of projected production from proved reserves for a period not exceeding 66 months from the date the swap is entered into.

        The Holdings Credit Agreement contains customary events of default, which would permit the lenders to accelerate the debt if not cured within applicable grace periods. If an event of default occurs and is continuing, lenders with a majority of the aggregate commitments may require Bank of America, N.A. to declare all amounts outstanding under the Holdings Credit Agreement to be immediately due and payable.

Second Lien

        As of March 31, 2013, Holdings was a party to a second lien term loan agreement dated September 5, 2012 (the "Second Lien"), which matures on November 21, 2017. The Second Lien provided for term loans to be made to Holdings in the aggregate amount of up to $125 million. As of March 31, 2013, there were $125 million outstanding loans under the Second Lien. Holdings used the net proceeds from the Second Lien to reduce outstanding borrowings under its credit agreement. The Second Lien was repaid in full with a portion of the net proceeds from the issuance of senior notes in April 2013. Please read "Note 10. Subsequent Events—Senior Notes" for additional discussion.

Note 6. Partners' Equity

        Holdings is party to a limited partnership agreement with its management group and Apollo. The Apollo Funds, members of Holdings' management team, and certain employees are Class A limited partners. The following table shows the partnership interest in Holdings as of March 31, 2013:

		Partnership Interest
Athlon Holdings LLC	General Partner		0.000	%
The Apollo Funds	Class A Partner		96.825	%
Management team and employees	Class A Partner		3.175	%

        As of March 31, 2013, Holdings had remaining capital commitments of approximately $38.1 million from the Apollo Funds and none from management and employees. After Holdings' corporate

F-23

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 6. Partners' Equity (Continued)

reorganization as discussed in "Note 10. Subsequent Events—Corporate Reorganization", the Apollo Funds have no further capital commitments.

Note 7. Class B Limited Partner Interests

        Holdings' limited partnership agreement provides for the issuance of Class B limited partner interests. The Class B interests entitle the holder to participate in the net profits of Holdings, but are subject to various performance criteria. Class A limited partners are entitled to a return of their initial investment plus interest compounded at 8% annually (the "Class A Preference Amount"). Upon the occurrence of a liquidity event and after the Class A Preference Amount has been satisfied, 80% and 20% of the remaining net profits will be distributed to holders of Class A interests and Class B interests, respectively. The Class B interests vest over four or five years or upon certain performance thresholds being met by Holdings. Class B interests can also vest on the occurrence of certain events such as a change in control or in some cases upon termination of employment with Holdings. The total number of Class B interests that may be issued pursuant to the partnership agreement is 100,000. As of March 31, 2013, there were 2,600 Class B interests available for issuance under the partnership agreement. Class B interests that are forfeited will again become available for issuance under the partnership agreement.

        Management has independent valuations prepared for its grants of Class B limited partner interests. During the three months ended March 31, 2013 and 2012, Holdings recorded approximately $48,000 and $58,000, respectively, of non-cash equity-based compensation expense, which was allocated to LOE and general and administrative expenses in the accompanying Consolidated Statements of Operations based on the allocation of the respective employees' compensation. During the three months ended March 31, 2013, Holdings also capitalized approximately $26,000 of non-cash stock-based compensation expense as a component of "Proved properties, including wells and related equipment" in the accompanying Consolidated Balance Sheets.

        The fair value of Class B interests granted was estimated on the grant date using an option pricing model based on the following assumptions for the periods indicated:

	Three months ended March 31,
	2013			2012
Expected volatility		40.6	%		46.3	%
Expected dividend yield		0	%		0	%
Expected term (in years)		0.62			1.63
Risk-free interest rate		0.13	%		0.24	%
Weighted-average grant date fair value per interest	$	67.68		$	140.72

        The expected volatility was calculated based on the average historical volatility of each company in Holdings' peer group based on historical stock price data. The expected term of the Class B interests was based on expected payout date from a triggering event. The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the grant date for a period of time commensurate with the expected term of the Class B interests.

F-24

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 7. Class B Limited Partner Interests (Continued)

        The following table summarizes the changes in Holdings' Class B interests for the three months ended March 31, 2013:

	Number of Class B Interests			Weighted- Average Grant Date Fair Value
Outstanding at January 1		50,212		$	22.07
Granted		3,600			67.68
Vested		(7,175	)		6.36
Forfeited		—			—
Outstanding at March 31		46,637			27.65

        As of March 31, 2013, Holdings had approximately $1.2 million of total unrecognized compensation cost related to unvested Class B interests, which is expected to be recognized over a weighted-average period of approximately 3.8 years. During the three months ended March 31, 2013 and 2012, there were 7,175 and 6,832, respectively, Class B interests that vested, the total grant date fair value of which was approximately $46,000 and none, respectively.

        In conjunction with Holdings' corporate reorganization as discussed in "Note 10. Subsequent Events—Corporate Reorganization", the holders of the Class B limited partner interest in Holdings exchanged their interests for common stock of Athlon subject to the same vesting terms.

Note 8. Fair Value Measurements

        The book values of cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the short-term nature of these instruments. The book values of the Holdings Credit Agreement and the Second Lien approximate fair value as the interest rates are variable. Holdings considers debt with variable interest rates to have a fair value equal to its carrying value ("Level 1" input). Commodity derivative contracts are marked-to-market each quarter and are thus stated at fair value in the accompanying Consolidated Balance Sheets.

Derivative Policy

        Holdings uses various financial instruments for non-trading purposes to manage and reduce price volatility and other market risks associated with its oil production. These arrangements are structured to reduce Holdings' exposure to commodity price decreases, but they can also limit the benefit Holdings might otherwise receive from commodity price increases. Holdings' risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions, most of which are lenders underwriting the Holdings Credit Agreement.

        Holdings applies the provisions of the "Derivatives and Hedging" topic of the Accounting Standards Codification, which requires each derivative instrument to be recorded in the accompanying Consolidated Balance Sheets at fair value. If a derivative has not been designated as a hedge or does not otherwise qualify for hedge accounting, it must be adjusted to fair value through earnings. Holdings elected not to designate its current portfolio of commodity derivative contracts as hedges. Therefore,

F-25

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 8. Fair Value Measurements (Continued)

changes in fair value of these derivative instruments are recognized in earnings and included in "Derivative fair value loss" in the accompanying Consolidated Statements of Operations.

Commodity Derivative Contracts

        Commodity prices are often subject to significant volatility due to many factors that are beyond Holdings' control, including but not limited to: prevailing economic conditions, supply and demand of hydrocarbons in the marketplace, actions by speculators, and geopolitical events such as wars or natural disasters. Holdings' objective is to manage its exposure to oil price risk with swaps, puts, and collars. Swaps provide a fixed price for a notional amount of sales volumes. Puts provide a fixed floor price on a notional amount of sales volumes while allowing full price participation if the relevant index price closes above the floor price. Collars provide a floor price on a notional amount of sales volumes while allowing some additional price participation if the relevant index price closes above the floor price. This participation is limited by a ceiling price specified in the contract.

        The following table summarizes open commodity derivative contracts as of March 31, 2013:

Period	Average Daily Floor Volume		Weighted- Average Floor Price		Average Daily Cap Volume		Weighted- Average Cap Price		Average Daily Swap Volume		Weighted- Average Swap Price		Asset (Liability) Fair Market Value
	(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(in thousands)
Apr. - Dec. 2013		150	$	75.00		150	$	105.95		6,000	$	94.66	$	(3,474	)
2014		—		—		—		—		5,950		92.76		130
2015		—		—		—		—		1,300		93.18		1,782
													$	(1,562	)

        Holdings is also party to basis differential swaps for 5,000 Bbls/D at $1.20/Bbl for March through December 2013. At March 31, 2013, the fair value of these contracts was a liability of approximately $1.2 million.

        Counterparty Risk.    At March 31, 2013, Holdings had committed 10% or greater (in terms of fair market value) of its oil derivative contracts in asset positions from the following counterparties:

Counterparty	Fair Market Value of Oil Derivative Contracts Committed
	(in thousands)
BNP Paribas	$	1,824

        Holdings does not require collateral from its counterparties for entering into financial instruments, so in order to mitigate the credit risk associated with financial instruments, Holdings enters into master netting agreements with certain counterparties. The master netting agreement is a standardized, bilateral contract between a given counterparty and Holdings. Instead of treating each financial transaction between the counterparty and Holdings separately, the master netting agreement enables the counterparty and Holdings to aggregate all financial trades and treat them as a single agreement. This arrangement is intended to benefit Holdings in two ways: (1) default by a counterparty under one

F-26

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 8. Fair Value Measurements (Continued)

financial trade can trigger rights to terminate all financial trades with such counterparty; and (2) netting of settlement amounts reduces Holdings' credit exposure to a given counterparty in the event of close-out. Holdings' accounting policy is to not offset fair value amounts between different counterparties for derivative instruments in the accompanying Consolidated Balance Sheets.

Tabular Disclosures of Fair Value Measurements

        The following table summarizes the fair value of Holdings' derivative instruments not designated as hedging instruments as of the dates indicated:

Balance Sheet Location	Oil Commodity Derivatives			Commodity Derivatives Nettinga			Total Commodity Derivatives
As of March 31, 2013
Assets
Derivatives—current	$	863		$	(863	)	$	—
Derivatives—noncurrent		3,110			(906	)		2,204
Total assets		3,973			(1,769	)		2,204
Liabilities
Derivatives—current		(5,462	)		863			(4,599	)
Derivatives—noncurrent		(1,230	)		906			(324	)
Total liabilities		(6,692	)		1,769			(4,923	)
Net assets (liabilities)	$	(2,719	)	$	—		$	(2,719	)
As of December 31, 2012
Assets
Derivatives—current	$	3,386		$	(1,140	)	$	2,246
Derivatives—noncurrent		3,265			(411	)		2,854
Total assets		6,651			(1,551	)		5,100
Liabilities
Derivatives—current	$	(1,732	)		1,140		$	(592	)
Derivatives—noncurrent		(930	)		411			(519	)
Total liabilities		(2,662	)		1,551			(1,111	)
Net assets (liabilities)	$	3,989		$	—		$	3,989

^a

Represents counterparty netting under master netting agreements, which allow for netting of commodity derivative contracts. These derivative instruments are reflected net on the accompanying Consolidated Balance Sheets.

F-27

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 8. Fair Value Measurements (Continued)

        The following table summarizes the effect of derivative instruments not designated as hedges on the accompanying Consolidated Statements of Operations for the periods indicated (in thousands):

		Amount of Loss Recognized in Income
		Three months ended March 31,
	Location of Loss Recognized in Income
Derivatives Not Designated as Hedges		2013		2012
Commodity derivative contracts	Derivative fair value loss	$	6,849	$	22,711

Fair Value Hierarchy

        Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. GAAP establishes a three-tier fair value hierarchy, which prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are defined as follows:

•

Level 1—Inputs such as unadjusted, quoted prices that are available in active markets for identical assets or liabilities.

•

Level 2—Inputs, other than quoted prices within Level 1, that are either directly or indirectly observable.

•

Level 3—Inputs that are unobservable for use when little or no market data exists requiring the use of valuation methodologies that result in management's best estimate of fair value.

        As required by GAAP, Holdings utilizes the most observable inputs available for the valuation technique used. The financial assets and liabilities are classified in their entirety based on the lowest level of input that is of significance to the fair value measurement. Holdings' assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the financial assets and liabilities and their placement within the fair value hierarchy levels. The following methods and assumptions were used to estimate the fair values of Holdings' assets and liabilities that are accounted for at fair value on a recurring basis:

•

Level 2—Fair values of swaps were estimated using a combined income-based and market-based valuation methodology based upon forward commodity price curves obtained from independent pricing services. Holdings' collars and puts are average value options. Settlement is determined by the average underlying price over a predetermined period of time. Holdings uses observable inputs in an option pricing valuation model to determine fair value such as: (1) current market and contractual prices for the underlying instruments; (2) quoted forward prices for oil and natural gas; (3) interest rates, such as a LIBOR curve for a term similar to the commodity derivative contract; and (4) appropriate volatilities.

        Holdings adjusts the valuations from the valuation model for nonperformance risk. For commodity derivative contracts which are in an asset position, Holdings uses the counterparty's credit default swap

F-28

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 8. Fair Value Measurements (Continued)

rating. For commodity derivative contracts which are in a liability position, Holdings uses the average credit default swap rating of its peer companies as Holdings does not have its own credit default swap rating. All fair values have been adjusted for nonperformance risk resulting in an increase in the net commodity derivative liability of approximately $0.2 million as of March 31, 2013 and an increase in the net commodity derivative asset of approximately $0.1 million as of December 31, 2012.

        The following table sets forth Holdings' assets and liabilities that were accounted for at fair value on a recurring basis as of the dates indicated:

				Fair Value Measurements at Reporting Date Using
Description	Asset (liability), net			Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	(in thousands)
As of March 31, 2013
Oil derivative contracts—swaps	$	(1,504	)	$	—	$	(1,504	)	$	—
Oil derivative contracts—basis differential swaps		(1,157	)		—		(1,157	)		—
Oil derivative contracts—collars and puts		(58	)		—		(58	)		—
Total	$	(2,719	)	$	—	$	(2,719	)	$	—
As of December 31, 2012
Oil derivative contracts—swaps	$	4,069		$	—	$	4,069		$	—
Oil derivative contracts—collars and puts		(80	)		—		(80	)		—
Total	$	3,989		$	—	$	3,989		$	—

Note 9. Related Party Transactions

Transaction Fee Agreement

        Holdings is a party to a Transaction Fee Agreement, dated August 23, 2010, which requires Holdings to pay a fee to Apollo equal to 2% of the total equity contributed to Holdings, as defined in the agreement, in exchange for consulting and advisory services provided by Apollo. In October 2012, Apollo assigned its rights and obligations under the Transaction Fee Agreement to an affiliate, Apollo Global Securities, LLC. Since Holdings' inception through March 31, 2013, it has incurred transaction fees under the Transaction Fee Agreement of approximately $7.5 million in total. Upon the consummation of Athlon's initial public offering as discussed in "Note 10. Subsequent Events—Initial Public Offering", Holdings intends to terminate the Transaction Fee Agreement.

F-29

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 9. Related Party Transactions (Continued)

Services Agreement

        Holdings is a party to a Services Agreement, dated August 23, 2010, which requires Holdings to further compensate Apollo for consulting and advisory services equal to a minimum of $62,500 per quarter or 1% of net income before interest, income taxes, and DD&A, not to exceed $500,000 in any calendar year. The Services Agreement also provides for reimbursement to Apollo for any reasonable out-of-pocket expenses incurred while performing under the Services Agreement. During the three months ended March 31, 2013 and 2012, Holdings incurred approximately $405,000 and $213,000, respectively, of fees under the Services Agreement, which is included in "General and administrative expenses" in the accompanying Consolidated Statements of Operations.

        The Services Agreement provides that Apollo will provide advisory services until the earliest of (i) August 23, 2020, (ii) such time as Apollo owns in the aggregate less than 5% of the beneficial economic interest of Holdings, and (iii) such date as is mutually agreed upon by Holdings and Apollo. Upon the consummation of Athlon's initial public offering as discussed in "Note 10. Subsequent Events—Initial Public Offering", Holdings intends to terminate the Services Agreement and, in connection with the termination, Apollo will receive a discounted payment corresponding to the present value as of the date of termination of the aggregate annual fees that would have been payable during the remainder of the term of the Services Agreement (assuming a term ending on August 23, 2020). Under the Services Agreement, Holdings also agreed to indemnify Apollo and its affiliates and their respective limited partners, general partners, directors, members, officers, managers, employees, agents, advisors, their directors, officers, and representatives for potential losses relating to the services contemplated under the Services Agreement.

Note 10. Subsequent Events

Senior Notes

        In April 2013, Holdings issued $500 million aggregate principal amount of 7³/8% senior notes due 2021. The net proceeds from the senior notes offering were used to repay a portion of the outstanding borrowings under the Holdings Credit Agreement, to repay the Second Lien in full, to make a $75 million distribution to Holdings' Class A limited partners, and for general partnership purposes. The indenture governing the senior notes contains covenants, including, among other things, covenants that restrict Holdings' ability to:

•

make distributions, investments, or other restricted payments if Holdings' fixed charge coverage ratio is less than 2.0 to 1.0;

•

incur additional indebtedness if Holdings' fixed charge coverage ratio would be less than 2.0 to 1.0; and

•

create liens, sell assets, consolidate or merge with any other person, or engage in transactions with affiliates.

These covenants are subject to a number of important qualifications, limitations, and exceptions. In addition, the indenture contains other customary terms, including certain events of default upon the occurrence of which the senior notes may be declared immediately due and payable.

F-30

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 10. Subsequent Events (Continued)

        Under the indenture, starting on April 15, 2016, Holdings will be able to redeem some or all of the senior notes at a premium that will decrease over time, plus accrued and unpaid interest to the date of redemption. Prior to April 15, 2016, Holdings will be able, at its option, to redeem up to 35% of the aggregate principal amount of the senior notes at a price of 107.375% of the principal thereof, plus accrued and unpaid interest to the date of redemption, with an amount equal to the net proceeds from certain equity offerings. In addition, at Holdings' option, prior to April 15, 2016, Holdings may redeem some or all of the senior notes at a redemption price equal to 100% of the principal amount of the senior notes, plus an "applicable premium", plus accrued and unpaid interest to the date of redemption. If a change of control occurs on or prior to July 15, 2014, Holdings may redeem all, but not less than all, of the notes at 110% of the principal amount thereof plus accrued and unpaid interest to, but not including, the redemption date. Certain asset dispositions will be triggering events that may require Holdings to repurchase all or any part of a noteholder's notes at a purchase price in cash equal to 101% of the principal amount thereof, plus accrued and unpaid interest, if any, to but excluding the date of repurchase. Interest on the senior notes is payable in cash semi-annually in arrears, commencing on October 15, 2013, through maturity.

Holdings Credit Agreement

        In conjunction with the offering of senior notes, the borrowing base under the Holdings Credit Agreement was reduced to $267.5 million. Holdings used a portion of the net proceeds from the offering of the senior notes as discussed above to reduce the outstanding borrowings under the Holdings Credit Agreement. As of May 15, 2013, there were $36 million of outstanding borrowings under the Holdings Credit Agreement.

Corporate Reorganization

        As previously discussed in "Note 1. Formation of the Partnership and Description of Business", Athlon was formed on April 1, 2013. On April 26, 2013, Holdings underwent a corporate reorganization and as a result, Athlon became the holding company of Holdings. Athlon will operate and control all of the business and affairs and consolidate the financial results of Holdings. In the corporate reorganization, the Apollo Funds entered into a number of distribution and contribution transactions pursuant to which the Apollo Funds exchanged their Class A limited partner interests in Holdings for common stock of Athlon. The remaining holders of Class A limited partner interests in Holdings have not exchanged their interests in the reorganization transactions. In addition, the holders of the Class B limited partner interests in Holdings exchanged their interests for common stock of Athlon subject to the same vesting terms. As a result of the corporate reorganization, Athlon has become a taxable entity for federal income tax purposes. Management is in the process of computing the tax-related impacts of the corporate reorganization.

Initial Public Offering

        On April 29, 2013, Athlon announced that it has confidentially submitted a draft registration statement on Form S-1 to the SEC for a possible initial public offering of shares of its common stock. The number of shares to be offered and the price range for the offering have not yet been determined. Athlon intends to contribute the proceeds from the initial public offering to Holdings, which is

F-31

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

(unaudited)

Note 10. Subsequent Events (Continued)

expected to use the proceeds to reduce outstanding borrowings under the Holdings Credit Agreement, to provide additional liquidity for use in its drilling program, and for general corporate purposes, including potential acquisitions. The initial public offering is expected to commence after the SEC completes the review process with respect to Athlon's registration statement, subject to market conditions and other conditions.

        These financial statements considered subsequent events through May 15, 2013, the date the consolidated financial statements were available to be issued.

F-32

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Board of Supervisors and Partners
Athlon Holdings LP

        We have audited the accompanying consolidated balance sheets of Athlon Holdings LP (the "Partnership") as of December 31, 2012 and 2011, and the related consolidated statements of operations, changes in partners' equity, and cash flows for each of the two years in the period ended December 31, 2012. These financial statements are the responsibility of the Partnership's management. Our responsibility is to express an opinion on these financial statements based on our audits.

        We conducted our audits in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. We were not engaged to perform an audit of the Partnership's internal control over financial reporting. Our audits included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of the Partnership's internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audits provide a reasonable basis for our opinion.

        In our opinion, the financial statements referred to above present fairly, in all material respects, the consolidated financial position of Athlon Holdings LP at December 31, 2012 and 2011, and the consolidated results of its operations and its cash flows for each of the two years in the period ended December 31, 2012, in conformity with U.S. generally accepted accounting principles.

/s/ Ernst & Young LLP

Fort Worth, Texas
March 8, 2013

F-33

ATHLON HOLDINGS LP

CONSOLIDATED BALANCE SHEETS

(in thousands)

	December 31,
	2012			2011
ASSETS
Current assets:
Cash and cash equivalents	$	8,871		$	32,030
Accounts receivable		24,501			17,181
Derivatives		2,246			—
Inventory		1,022			751
Other		2,486			1,574
Total current assets		39,126			51,536
Properties and equipment, at cost—full cost method:
Proved properties, including wells and related equipment		788,571			399,205
Unproved properties		89,860			125,036
Accumulated depletion, depreciation, and amortization		(73,824	)		(19,589	)
		804,607			504,652
Derivatives		2,854			2,503
Debt issuance costs		4,418			2,264
Other		1,293			868
Total assets	$	852,298		$	561,823
LIABILITIES AND PARTNERS' EQUITY
Current liabilities:
Accounts payable:
Trade	$	3,170		$	3,214
Affiliate		935			4,581
Accrued liabilities:
Lease operating		3,858			2,568
Production, severance, and ad valorem taxes		1,307			2,592
Development capital		39,483			30,863
Derivatives		592			5,908
Revenue payable		9,330			5,710
Other		2,700			2,036
Total current liabilities		61,375			57,472
Derivatives		519			2,554
Asset retirement obligations		5,049			3,704
Long-term debt		362,000			170,000
Other		2,478			641
Total liabilities		431,421			234,371
Commitments and contingencies
Partners' equity		420,877			327,452
Total liabilities and partners' equity	$	852,298		$	561,823

The accompanying notes are an integral part of these consolidated financial statements.

F-34

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENTS OF OPERATIONS

(in thousands)

	Year ended December 31,
	2012			2011
Revenues:
Oil	$	128,081		$	51,193
Natural gas		8,415			3,521
Natural gas liquids		20,615			10,967
Total revenues		157,111			65,681
Expenses:
Production:
Lease operating		25,503			13,328
Production, severance, and ad valorem taxes		10,438			4,727
Depletion, depreciation, and amortization		54,456			19,747
General and administrative		9,678			7,724
Acquisition costs		876			9,519
Derivative fair value loss (gain)		(9,293	)		7,959
Other operating		562			404
Total expenses		92,220			63,408
Operating income		64,891			2,273
Interest expense		9,949			2,932
Income (loss) before income taxes		54,942			(659	)
Income tax provision		1,928			470
Net income (loss)	$	53,014		$	(1,129	)

The accompanying notes are an integral part of these consolidated financial statements.

F-35

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENTS OF CHANGES IN PARTNERS' EQUITY

(in thousands)

	Total Partners' Equity
Balance at December 31, 2010	$	24,499
Capital contributions from partners		303,976
Equity-based compensation		106
Net loss		(1,129	)
Balance at December 31, 2011		327,452
Capital contributions from partners		40,166
Equity-based compensation		245
Net income		53,014
Balance at December 31, 2012	$	420,877

The accompanying notes are an integral part of these consolidated financial statements.

F-36

ATHLON HOLDINGS LP

CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands)

	Year ended December 31,
	2012			2011
Cash flows from operating activities:
Net income (loss)	$	53,014		$	(1,129	)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depletion, depreciation, and amortization		54,456			19,747
Deferred taxes		1,928			470
Non-cash derivative loss (gain)		(9,947	)		7,509
Equity-based compensation		152			106
Other		1,758			963
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable		(7,320	)		(16,963	)
Other current assets		(337	)		(1,691	)
Other assets		—			(16	)
Accounts payable		(2,140	)		537
Revenue payable		3,620			5,710
Derivatives		—			1,950
Other current liabilities		118			5,579
Net cash provided by operating activities		95,302			18,872
Cash flows from investing activities:
Acquisitions of oil and natural gas properties		(80,602	)		(414,759	)
Development of oil and natural gas properties		(266,235	)		(57,457	)
Monetization of put options		—			7,625
Other		(422	)		(884	)
Net cash used in investing activities		(347,259	)		(465,475	)
Cash flows from financing activities:
Proceeds from long-term debt, net of issuance costs		519,672			198,651
Payments on long-term debt		(331,000	)		(31,000	)
Capital contributions from partners		40,166			303,976
Other		(40	)		—
Net cash provided by financing activities		228,798			471,627
Increase (decrease) in cash and cash equivalents		(23,159	)		25,024
Cash and cash equivalents, beginning of period		32,030			7,006
Cash and cash equivalents, end of period	$	8,871		$	32,030

The accompanying notes are an integral part of these consolidated financial statements.

F-37

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

Note 1. Formation of the Partnership and Description of Business

        Athlon Holdings LP (together with its subsidiaries, "Holdings"), a Delaware limited partnership, is engaged in the acquisition and development of oil and natural gas reserves in the Permian Basin of West Texas. Holdings was formed on July 22, 2011, and is the holding company for Athlon Energy LP (together with its operating subsidiary, Athlon Energy Operating LLC, "Athlon SG"), a Delaware limited partnership, which was formed on August 5, 2010, and Athlon FE Energy LP (together with its operating subsidiary, Athlon FE Operating LLC, "Athlon FE"), a Delaware limited partnership, which was formed on July 22, 2011. Athlon Holdings LLC serves as the general partner to Holdings with no obligations to make capital contributions and no rights to distributions. Holdings owns all of Athlon SG's and Athlon FE's general partner and limited partner units.

        On August 23, 2010, Athlon SG entered into a limited partnership agreement with its management group and Apollo Athlon Holdings LLC ("Apollo"), which is an affiliate of Apollo Global Management, LLC. Apollo has a controlling influence over Holdings. On July 22, 2011, the partnership agreement was amended and restated resulting in the formation of Holdings and Athlon FE. Upon formation, Holdings became the holding company of Athlon SG and Athlon FE. The amended and restated partnership agreement required all of Athlon SG's equity contributions to be contributed to Holdings. The holders of all Class A and Class B limited partner units in Athlon SG contributed these units to Holdings in exchange for equivalent units of Holdings. As the amendment of the partnership agreement constituted a reorganization of entities under common control, the operations of Athlon SG are presented as if Holdings existed and owned Athlon SG prior to July 22, 2011 and the assets and liabilities of Athlon SG are reflected at their carrying amounts. Please read "Note 7. Partners' Equity" and "Note 8. Employee Benefit Plans" for additional discussion.

Note 2. Summary of Significant Accounting Policies

Principles of Consolidation

        Holdings' consolidated financial statements include the accounts of its wholly owned subsidiaries. All material intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

        Preparing financial statements in conformity with accounting principles generally accepted in the United States requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses, and the disclosure of contingent assets and liabilities in the consolidated financial statements. Although management believes these estimates are reasonable, actual results could differ materially from those estimates.

        Estimates made in preparing these consolidated financial statements include, among other things, estimates of the proved oil and natural gas reserve volumes used in calculating depletion, depreciation, and amortization ("DD&A") expense; operating costs accrued; volumes and prices for revenues accrued; valuation of derivative instruments; and the timing and amount of future abandonment costs used in calculating asset retirement obligations. Changes in the assumptions used could have a significant impact on results in future periods.

F-38

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

Cash and Cash Equivalents

        Cash and cash equivalents include demand deposits and funds invested in highly liquid instruments with original maturities of three months or less and typically exceed federally insured limits.

        The following table sets forth supplemental disclosures of cash flow information for the periods indicated:

	Year ended December 31,
	2012		2011
	(in thousands)
Cash paid during the period for:
Interest	$	8,326	$	2,395
Income taxes		—		—

Accounts Receivable

        Accounts receivable, which are primarily from the sale of oil, natural gas, and natural gas liquids ("NGLs"), is accrued based on estimates of the sales and prices Holdings believes it will receive. Holdings routinely reviews outstanding balances, assesses the financial strength of its customers, and records a reserve for amounts not expected to be fully recovered. Actual balances are not applied against the reserve until substantially all collection efforts have been exhausted. At December 31, 2012 and 2011, Holdings had no allowance for doubtful accounts.

Inventory

        Inventory includes materials and supplies that Holdings intends to deploy to various development activities and oil in tanks at the lease, both of which are stated at the lower of cost (determined on an average basis) or market. Oil in tanks at the lease is carried at an amount equal to its costs to produce. Inventory consisted of the following as of the dates indicated:

	December 31,
	2012		2011
	(in thousands)
Materials and supplies	$	670	$	371
Oil inventory		352		380
Total inventory	$	1,022	$	751

Oil and Natural Gas Properties

        Holdings applies the provisions of the "Extractive Activities—Oil and Gas" topic of the Financial Accounting Standards Board's (the "FASB") Accounting Standards Codification (the "ASC"). Holdings uses the full cost method of accounting for its oil and natural gas properties. Under this method, costs directly associated with the acquisition, exploration, and development of reserves are capitalized into a full cost pool. Capitalized costs are amortized using a unit-of-production method. Under this method, the provision for DD&A is computed at the end of each period by multiplying total production for the

F-39

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

period by a depletion rate. The depletion rate is determined by dividing the total unamortized cost base plus future development costs by net equivalent proved reserves at the beginning of the period.

        Costs associated with unproved properties are excluded from the amortizable cost base until a determination has been made as to the existence of proved reserves. Unproved properties are reviewed at the end of each quarter to determine whether the costs incurred should be reclassified to the full cost pool and, thereby, subjected to amortization. The costs associated with unproved properties primarily consist of acquisition and leasehold costs as well as development costs for wells in progress for which a determination of the existence of proved reserves has not been made. These costs are transferred to the amortization base once a determination is made whether or not proved reserves can be assigned to the property, upon impairment of a lease, or immediately upon determination that the well is unsuccessful. Costs of seismic data that cannot be directly associated to specific unproved properties are included in the full cost pool as incurred, otherwise, they are allocated to various unproved leaseholds and transferred to the amortization base with the associated leasehold costs on a specific project basis.

        Unevaluated properties are assessed periodically, at least annually, for possible impairment. Properties are assessed on an individual basis or as a group if properties are individually insignificant. The assessment includes consideration of various factors, including, but not limited to: intent to drill, remaining lease term, geological and geophysical evaluations, drilling results, and economic viability of development if proved reserves are assigned. During any period in which these factors indicate impairment, the cumulative drilling costs incurred to date for such property and all or a portion of the associated leasehold costs are transferred to the full cost pool and become subject to amortization.

        Under the full cost method of accounting, total capitalized costs of oil and natural gas properties, net of accumulated depletion, less related deferred income taxes may not exceed an amount equal to the present value of future net revenues from proved reserves, discounted at 10% per annum, plus the lower of cost or fair value of unevaluated properties, plus estimated salvage value, less the related tax effects (the "ceiling limitation"). A ceiling limitation is calculated at the end of each quarter. If total capitalized costs, net of accumulated DD&A, less related deferred income taxes are greater than the ceiling limitation, a write-down or impairment of the full cost pool is required. A write-down of the carrying value of the full cost pool is a non-cash charge that reduces earnings and impacts partners' equity in the period of occurrence and typically results in lower DD&A expense in future periods. Once incurred, a write-down cannot be reversed at a later date.

        The ceiling limitation calculation is prepared using the 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves ("net wellhead prices"). If applicable, these net wellhead prices would be further adjusted to include the effects of any fixed price arrangements for the sale of oil and natural gas. Holdings uses commodity derivative contracts to mitigate the risk against the volatility of oil and natural gas prices. Commodity derivative contracts that qualify and are designated as cash flow hedges are included in estimated future cash flows. Holdings has not designated any of its commodity derivative contracts as cash flow hedges and has therefore not included its commodity derivative contracts in estimating future cash flows. The future cash outflows associated with future development or abandonment of wells are included in the computation of the discounted present value of future net revenues for purposes of the ceiling limitation calculation.

F-40

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

        Sales and abandonments of oil and natural gas properties being amortized are accounted for as adjustments to the full cost pool, with no gain or loss recognized, unless the adjustments would significantly alter the relationship between capitalized costs and proved reserves. A significant alteration would not ordinarily be expected to occur upon the sale of reserves involving less than 25% of the reserve quantities of a cost center.

        Natural gas volumes are converted to barrels of oil equivalent ("BOE") at the rate of six thousand cubic feet ("Mcf") of natural gas to one barrel ("Bbl") of oil. This convention is not an equivalent price basis and there may be a large difference in value between an equivalent volume of oil versus an equivalent volume of natural gas.

        Independent petroleum engineers estimate Holdings' proved reserves annually on December 31. This results in a new DD&A rate which Holdings uses for the preceding fourth quarter after adjusting for fourth quarter production. Holdings internally estimates reserve additions and reclassifications of reserves from unproved to proved at the end of the first, second, and third quarters for use in determining a DD&A rate for the respective quarter.

        Holdings capitalizes interest on expenditures made in connection with exploration and development projects that are not subject to current amortization. Interest is capitalized only for the period that activities are in progress to bring these projects to their intended use. Capitalized interest cannot exceed gross interest expense. During 2012, Holdings capitalized approximately $0.2 million of interest expense. During 2011, Holdings did not capitalize any interest expense.

        Amounts shown in the accompanying Consolidated Balance Sheets as "Proved properties, including wells and related equipment" consisted of the following as of the date indicated:

	December 31,
	2012		2011
	(in thousands)
Proved leasehold costs	$	376,271	$	283,302
Wells and related equipment—completed		379,036		89,140
Wells and related equipment—in process		33,264		26,763
Total proved properties	$	788,571	$	399,205

Asset Retirement Obligations

        Holdings applies the provisions of the "Asset Retirement and Environmental Obligations" topic of the ASC. Holdings has obligations as a result of lease agreements and enacted laws to remove its equipment and restore land at the end of production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and land remediation. At the time a well is drilled or acquired, Holdings records a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas asset representing asset retirement costs in the accompanying Consolidated Balance Sheets. The cost of the related oil and natural gas asset, including the asset retirement cost, is included in Holdings' full cost pool. The estimated fair value of an asset retirement obligation is the present value of the expected future cash outflows required to satisfy the asset retirement obligations discounted at Holdings' credit-adjusted,

F-41

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

risk-free interest rate at the time the liability is incurred. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.

        Inherent to the present-value calculation are numerous estimates, assumptions, and judgments, including, but not limited to: the ultimate settlement amounts, inflation factors, credit-adjusted risk-free rates, timing of settlement, and changes in the legal, regulatory, environmental, and political environments. To the extent future revisions to these assumptions affect the present value of the abandonment liability, Holdings makes corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. These revisions result in prospective changes to DD&A expense and accretion of the discounted abandonment liability. Please read "Note 5. Asset Retirement Obligations" for additional information.

Segment Reporting

        Holdings operates in only one industry: the oil and natural gas exploration and production industry in the United States. All revenues are derived from customers located in the United States.

Major Customers/Concentration of Credit Risk

        The following purchasers accounted for 10% or greater of the sales of production for the periods indicated and the corresponding outstanding accounts receivable balance as of the dates indicated:

	Percentage of Total Revenues for the Year Ended December 31,						Outstanding Accounts Receivable Balance as of December 31,
Purchaser	2012			2011			2012		2011
							(in thousands)
Occidental Petroleum Corporation		29	%		58	%	$	4,456	$	5,863
DCP Midstream		12	%		13	%		2,604		2,716
Pecos Gathering & Marketing		43	%		13	%		9,348		3,756

Income Taxes

        Holdings is treated as a partnership for federal and state income tax purposes with each partner being separately taxed on their share of Holdings' taxable income. Therefore, no provision for current or deferred federal income taxes has been provided for in the accompanying Consolidated Financial Statements. However, Holdings' operations located in Texas are subject to an entity-level tax, the Texas margin tax, at a statutory rate of up to 0.7% of income that is apportioned to Texas. Deferred tax assets and liabilities are recognized for future Texas margin tax consequences attributable to differences between financial statement carrying amounts of existing assets and liabilities and their respective Texas margin tax bases.

        Net income (loss) for financial statement purposes may differ significantly from taxable income reportable to partners as a result of differences between the tax bases and financial reporting bases of assets and liabilities and the taxable income allocation requirements under the partnership agreement. In addition, individual partners have different investment bases depending upon the timing and price of acquisition of their partnership units, and each partner's tax accounting, which is partially dependent

F-42

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

upon the partner's tax position, differs from the accounting followed in the accompanying Consolidated Financial Statements. As a result, the aggregate difference in the basis of net assets for financial and tax reporting purposes cannot be readily determined as Holdings does not have access to information about each partner's tax attributes in Holdings.

        Holdings performs a periodic evaluation of tax positions to review the appropriate recognition threshold for each tax position recognized in its consolidated financial statements. As of December 31, 2012 and 2011, all of Holdings' tax positions met the "more-likely-than-not" threshold. As a result, no additional tax expense, interest, or penalties have been accrued.

Revenue Recognition

        Revenues from the sale of oil, natural gas and NGLs are recognized when the production is sold, net of any royalty interest. Because final settlement of Holdings' hydrocarbon sales can take up to two months, the expected sales volumes and prices for those properties are estimated and accrued using information available at the time the revenue is recorded. Natural gas revenues are recorded using the sales method of accounting whereby revenue is recognized based on actual sales of natural gas rather than Holdings' proportionate share of natural gas production. If Holdings' overproduced imbalance position (i.e., Holdings has cumulatively been over-allocated production) is greater than its share of remaining reserves, a liability would be recorded for the excess at period-end prices unless a different price is specified in the contract, in which case that price is used. At December 31, 2012 and 2011, Holdings did not have any natural gas imbalances. Revenue is not recognized for oil production in tanks, but the production is recorded as a current asset based on the cost to produce and included in "Inventory" in the accompanying Consolidated Balance Sheets. Transportation expenses are included in operating expenses and are not material.

Derivatives

        Holdings uses various financial instruments for non-trading purposes to manage and reduce price volatility and other market risks associated with its oil production. These arrangements are structured to reduce Holdings' exposure to commodity price decreases, but they can also limit the benefit Holdings might otherwise receive from commodity price increases. Holdings' risk management activity is generally accomplished through over-the-counter commodity derivative contracts with large financial institutions, most of which are lenders underwriting Holdings' revolving credit agreement.

        Holdings applies the provisions of the "Derivatives and Hedging" topic of the ASC, which requires each derivative instrument to be recorded in the accompanying Consolidated Balance Sheets at fair value. If a derivative has not been designated as a hedge or does not otherwise qualify for hedge accounting, it must be adjusted to fair value through earnings. Holdings elected not to designate its current portfolio of commodity derivative contracts as hedges. Therefore, changes in fair value of these derivative instruments are recognized in earnings and included in "Derivative fair value loss (gain)" in the accompanying Consolidated Statements of Operations.

        Holdings enters into commodity derivative contracts for the purpose of economically hedging the price of its anticipated oil production even though Holdings does not designate the derivatives as hedges for accounting purposes. Holdings classifies cash flows related to derivative contracts based on the nature and purpose of the derivative. As the derivative cash flows are considered an integral part of Holdings' oil and natural gas operations, they are classified as cash flows from operating activities in

F-43

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

the accompanying Consolidated Statements of Cash Flows. During 2011 and 2012, Holdings entered into commodity derivative contracts all of which were for the purpose of economically hedging its anticipated oil production.

        Cash flows relating to commodity derivative contracts that were entered into prior to Holdings commencing oil and natural gas operations in January 2011 are classified as investing activities in the accompanying Consolidated Statements of Cash Flows.

New Accounting Pronouncements

        In May 2011, the FASB issued Accounting Standards Update ("ASU") 2011-04, "Amendments to Achieve Common Fair Value Measurements and Disclosure Requirements in U.S. GAAP and IFRSs". ASU 2011-04 amended ASC 820 to converge the fair value measurement guidance in GAAP and International Financial Reporting Standards. Certain of the amendments clarified the application of existing fair value measurement requirements, while other amendments changed a particular principle in ASC 820. In addition, ASU 2011-04 required additional fair value disclosures. The amendments were effective for annual periods beginning after December 15, 2011. The adoption of ASU 2011-04 did not have a material impact on Holdings' financial position, results of operations, or liquidity.

        In December 2011, the FASB issued ASU 2011-11, "Disclosures about Offsetting Assets and Liabilities" and in January 2013 issued ASU 2013-01, "Clarifying the Scope of Disclosures About Offsetting Assets and Liabilities". These ASUs create new disclosure requirements regarding the nature of an entity's rights of setoff and related arrangements associated with its derivative instruments, repurchase agreements, and securities lending transactions. Certain disclosures of the amounts of certain instruments subject to enforceable master netting arrangements would be required, irrespective of whether the entity has elected to offset those instruments in the statement of financial position. These ASUs are effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of these ASUs will not impact Holdings' financial position, results of operations, or liquidity.

        No other new accounting pronouncements issued or effective during 2012, or in 2013 through the date of this report, had or are expected to have a material impact on Holdings' consolidated financial statements.

Note 3. Acquisitions

Cobra

        In December 2012, Athlon FE acquired certain oil and natural gas properties and related assets in the Permian Basin in West Texas from Cobra Oil & Gas Corporation and certain of its subsidiaries and affiliates for approximately $48.3 million in cash, which was financed through a $40 million capital contribution from Apollo and borrowings under Holdings' credit agreement. The operations of these properties have been included with those of Athlon FE from the date of acquisition.

Element

        On October 3, 2011, Athlon FE acquired certain oil and natural gas properties and related assets in the Permian Basin in West Texas from Element Petroleum, LP ("Element") for approximately $253.2 million in cash, which was financed through borrowings under Athlon FE's then-existing credit

F-44

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 3. Acquisitions (Continued)

agreement and capital contributions from partners. The operations of these properties have been included with those of Athlon FE from the date of acquisition. Athlon FE incurred approximately $6.4 million of transaction costs related to this acquisition, which are included in "General and administrative expenses" in the accompanying Consolidated Statements of Operations. Of this amount, approximately $4.3 million was paid to Apollo. Please read "Note 10. Related Party Transactions" for additional discussion.

        The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from Element was as follows (in thousands):

Proved properties, including wells and related equipment	$	130,527
Unproved properties		123,107
Other assets		806
Total assets acquired		254,440
Current liabilities		831
Asset retirement obligations		393
Total liabilities assumed		1,224
Fair value of net assets acquired	$	253,216

Pro Formas

        The following unaudited pro forma condensed financial data was derived from the historical financial statements of Holdings and from the accounting records of Element to give effect to the acquisition as if it had occurred on January 1, 2011. The unaudited pro forma condensed financial information has been included for comparative purposes only and is not necessarily indicative of the results that might have occurred had the Element acquisition taken place on January 1, 2011 and is not intended to be a projection of future results.

	Year ended December 31, 2011
	(in thousands)
Pro forma total revenues	$	89,618
Pro forma net income	$	9,777

SandRidge

        On January 6, 2011, Athlon SG acquired certain oil and natural gas properties and related assets in the Permian Basin in West Texas from SandRidge Exploration and Production, LLC ("SandRidge") for approximately $156.0 million in cash, which was financed through borrowings under Athlon SG's then-existing credit agreement and capital contributions from partners. The operations of these properties have been included with those of Athlon SG from the date of acquisition. Athlon SG incurred $2.6 million of transaction costs related to this acquisition, which are included in "General and administrative expenses" in the accompanying Consolidated Statements of Operations. Of this amount,

F-45

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 3. Acquisitions (Continued)

approximately $2.3 million was paid to Apollo. Please read "Note 10. Related Party Transactions" for additional discussion.

        The allocation of the purchase price to the fair value of the assets acquired and liabilities assumed from SandRidge was as follows (in thousands):

Proved properties, including wells and related equipment	$	158,157
Oil inventory		637
Total assets acquired		158,794
Asset retirement obligations		2,778
Fair value of net assets acquired	$	156,016

Note 4. Commitments and Contingencies

Leases

        Holdings leases certain office space that has non-cancelable lease terms in excess of one year. The following table summarizes by year the remaining non-cancelable future payments under these operating leases as of December 31, 2012:

	Payments Due by Period
	Total		2013		2014		2015		2016		2017		Thereafter
	(in thousands)
Corporate office lease	$	1,412	$	381	$	375	$	375	$	281	$	—	$	—
Midland office lease		375		90		92		96		97		—		—
Total	$	1,787	$	471	$	467	$	471	$	378	$	—	$	—

        Holdings' operating lease rental expense was approximately $507 thousand and $272 thousand during 2012 and 2011, respectively.

Litigation

        Holdings is a party to ongoing legal proceedings in the ordinary course of business. Management does not believe the results of these proceedings, individually or in the aggregate, will have a material adverse effect on Holdings' business, financial position, results of operations, or liquidity.

F-46

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 5. Asset Retirement Obligations

        Asset retirement obligations relate to future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal. The following table summarizes the changes in Holdings' asset retirement obligations for the period indicated:

	Year Ended December 31,
	2012			2011
	(in thousands)
Balance at January 1	$	3,704		$	—
Acquisition of properties		60			3,282
Wells drilled		815			166
Accretion of discount		478			344
Revisions of previous estimates		(8	)		—
Plugging and abandonment costs incurred		—			(88	)
Balance at December 31	$	5,049		$	3,704

Note 6. Long-Term Debt

Second Lien

        Holdings is a party to a second lien term loan agreement dated September 5, 2012 (the "Second Lien"), which matures on November 21, 2017. The Second Lien provides for term loans to be made to Holdings in the aggregate amount of up to $125 million. At December 31, 2012, there were $125 million outstanding loans under the Second Lien. Holdings used the net proceeds from the Second Lien to reduce outstanding borrowings under its credit agreements.

        Obligations under the Second Lien are secured by a second-priority security interest in substantially all of Holdings' proved reserves and in the equity interests of its operating subsidiaries. In addition, obligations under the Second Lien are fully and unconditionally guaranteed by Holdings' operating subsidiaries.

        Loans under the Second Lien are subject to varying rates of interest based on whether the loan is a Eurodollar loan or a base rate loan. Eurodollar loans under the Second Lien bear interest at the Eurodollar rate plus the applicable margin indicated in the following table, and base rate loans under the Second Lien bear interest at the base rate plus the applicable margin indicated in the following table:

Period	Eurodollar Loans			Base Rate Loans
September 5, 2012 through December 31, 2013		6.50	%		5.50	%
January 1, 2014 through December 31, 2014		6.75	%		5.75	%
January 1, 2015 through December 31, 2015		7.00	%		6.00	%
January 1, 2016 and thereafter		7.25	%		6.25	%

        The "Eurodollar rate" for any interest period (either one, two, three, or six months, as selected by Holdings) is equal to the British Bankers Association London Interbank Offered Rate ("LIBOR") divided by 1.00 minus the rate prescribed by the Board of Governors of the Federal Reserve System for determining the maximum reserve requirements in respect of Eurocurrency liabilities for a member of

F-47

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 6. Long-Term Debt (Continued)

the Federal Reserve System in New York City. The "Base Rate" is calculated as the highest of: (1) the annual rate of interest announced by Wells Fargo Bank, N.A. as its "prime rate"; (2) the federal funds effective rate plus 0.5%; or (3) LIBOR plus 1.0%.

        Borrowings under the Second Lien may be repaid from time to time without penalty, except during 2015 in which case there is a 1.0% pre-payment fee.

        The Second Lien contains covenants including, among others, the following:

•

a prohibition against incurring debt, subject to permitted exceptions;

•

a restriction on creating liens on Holdings' assets and the assets of its operating subsidiaries, subject to permitted exceptions;

•

restrictions on merging and selling assets outside the ordinary course of business;

•

restrictions on use of proceeds, investments, transactions with affiliates, or change of principal business;

•

a provision limiting oil and natural gas swaps to a volume not exceeding the percentages indicated in the following table:

The Months Immediately Following Any Date of Determination	Projected Production from Proved Developed Producing Reserves			Projected Production from Proved Reserves
1st through the 24th month		90	%		65	%
25th through the 36th month		85	%		50	%
37th and each succeeding month		85	%		0	%

•

a requirement that Holdings maintain a ratio of consolidated current assets (which includes availability under Holdings credit agreement) to consolidated current liabilities (which excludes current maturities of long-term debt, non-cash derivative assets and liabilities, and amounts due to Apollo under the Transaction Fee Agreement) of not less than 1.0 to 1.0;

•

a requirement that Holdings maintain a ratio of consolidated funded debt to consolidated Adjusted EBITDA (as defined in the Second Lien) of not more than 4.5 to 1.0; and

•

a requirement that Holdings maintain a ratio of the most recent present value of total proved reserves discounted at 10% to consolidated funded debt of not less than 1.5 to 1.0.

        As of December 31, 2012, Holdings was in compliance with all covenants of the Second Lien.

        The Second Lien contains customary events of default, which would permit the lenders to accelerate the debt if not cured within applicable grace periods. If an event of default occurs and is continuing, lenders with a majority of the aggregate commitments may require Wells Fargo Energy Capital, Inc. to declare all amounts outstanding under the Second Lien to be immediately due and payable.

F-48

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 6. Long-Term Debt (Continued)

Credit Agreements

Athlon SG Credit Agreement

        Athlon SG was a party to a credit agreement dated January 6, 2011 (as amended, the "SG Credit Agreement"), which was scheduled to mature on January 6, 2016. In May 2012, all outstanding borrowings under the SG Credit Agreement were repaid with borrowings under Holdings' new credit agreement discussed below and the SG Credit Agreement was terminated.

Athlon FE Credit Agreement

        Athlon FE was a party to a credit agreement dated October 3, 2011 (as amended, the "FE Credit Agreement"), which was scheduled to mature on October 3, 2016. In May 2012, all outstanding borrowings under the FE Credit Agreement were repaid with borrowings under Holdings' new credit agreement discussed below and the FE Credit Agreement was terminated.

Holdings Credit Agreement

        Holdings is a party to a credit agreement dated May 21, 2012 (as amended, the "Holdings Credit Agreement"), which matures on May 21, 2017. Upon entering into the Holdings Credit Agreement, all outstanding borrowings under each of the SG Credit Agreement and the FE Credit Agreement were repaid and the agreements were terminated. On September 5, 2012, Holdings amended the Holdings Credit Agreement to, among other things: (1) exclude amounts due to Apollo under the Transaction Fee Agreement from consolidated current liabilities in the calculation of consolidated current ratio; (2) provide for a reduction in the borrowing base of 20% of any amount incurred under the Second Lien in excess of $100 million; (3) waive the current ratio requirement for the quarter ended June 30, 2012; and (4) reaffirm the borrowing base at $245 million.

        The Holdings Credit Agreement provides for revolving credit loans to be made to Holdings from time to time and letters of credit to be issued from time to time for the account of Holdings or any of its restricted subsidiaries. The aggregate amount of the commitments of the lenders under the Holdings Credit Agreement is $700 million. Availability under the Holdings Credit Agreement is subject to a borrowing base, which is redetermined semi-annually and upon requested special redeterminations. On December 31, 2012, the borrowing base was $275 million and there were $237 million of outstanding borrowings, $38 million of borrowing capacity, and no outstanding letters of credit under the Holdings Credit Agreement.

        Holdings incurs a quarterly commitment fee at a rate of 0.5% per year on the unused portion of the Holdings Credit Agreement.

        Obligations under the Holdings Credit Agreement are secured by a first-priority security interest in substantially all of Holdings' proved reserves and in the equity interests of its operating subsidiaries. In addition, obligations under the Holdings Credit Agreement are guaranteed by Holdings' operating subsidiaries.

        Loans under the Holdings Credit Agreement are subject to varying rates of interest based on (1) outstanding borrowings in relation to the borrowing base and (2) whether the loan is a Eurodollar loan or a base rate loan. Eurodollar loans under the Holdings Credit Agreement bear interest at the Eurodollar rate plus the applicable margin indicated in the following table, and base rate loans under

F-49

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 6. Long-Term Debt (Continued)

the Holdings Credit Agreement bear interest at the base rate plus the applicable margin indicated in the following table:

Ratio of Outstanding Borrowings to Borrowing Base	Applicable Margin for Eurodollar Loans			Applicable Margin for Base Rate Loans
Less than .50 to 1		2.00	%		1.00	%
Greater than or equal to .50 to 1 but less than .75 to 1		2.25	%		1.25	%
Greater than or equal to .75 to 1 but less than .90 to 1		2.50	%		1.50	%
Greater than or equal to .90 to 1		2.75	%		1.75	%

        The "Eurodollar rate" for any interest period (either one, two, three, or six months, as selected by Holdings) is the rate equal to the LIBOR for deposits in dollars for a similar interest period. The "Base Rate" is calculated as the highest of: (1) the annual rate of interest announced by Bank of America, N.A. as its "prime rate"; (2) the federal funds effective rate plus 0.5%; or (3) except during a "LIBOR Unavailability Period," the Eurodollar rate (for dollar deposits for a one-month term) for such day plus 1.0%.

        Any outstanding letters of credit reduce the availability under the Holdings Credit Agreement. Borrowings under the Holdings Credit Agreement may be repaid from time to time without penalty.

        The Holdings Credit Agreement contains covenants including, among others, the following:

•

a prohibition against incurring debt, subject to permitted exceptions;

•

a restriction on creating liens on Holdings' assets and the assets of its operating subsidiaries, subject to permitted exceptions;

•

restrictions on merging and selling assets outside the ordinary course of business;

•

restrictions on use of proceeds, investments, transactions with affiliates, or change of principal business;

•

a provision limiting oil and natural gas swaps to a volume not exceeding the percentages indicated in the following table:

The Months Immediately Following Any Date of Determination	Projected Production from Proved Developed Producing Reserves			Projected Production from Proved Reserves
1st through the 24th month		90	%		65	%
25th through the 36th month		85	%		50	%
37th and each succeeding month		85	%		0	%

•

a requirement that Holdings maintain a ratio of consolidated current assets (which includes availability under the Holdings Credit Agreement) to consolidated current liabilities (which excludes current maturities of long-term debt, obligations to Apollo arising from the Transaction Fee Agreement, and non-cash derivative assets and liabilities) of not less than 1.0 to 1.0; and

•

a requirement that Holdings maintain a ratio of consolidated funded debt to consolidated Adjusted EBITDA (as defined in the Holdings Credit Agreement) of not more than 4.0 to 1.0.

F-50

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 6. Long-Term Debt (Continued)

        As of December 31, 2012, Holdings was in compliance with all covenants of the Holdings Credit Agreement.

        The Holdings Credit Agreement contains customary events of default, which would permit the lenders to accelerate the debt if not cured within applicable grace periods. If an event of default occurs and is continuing, lenders with a majority of the aggregate commitments may require Bank of America, N.A. to declare all amounts outstanding under the Holdings Credit Agreement to be immediately due and payable.

Long-Term Debt Maturities

        The following table shows Holdings' long-term debt maturities as of December 31, 2012:

	Payments Due by Period
	Total		2013		2014		2015		2016		2017		Thereafter
	(in thousands)
Holdings Credit Agreement	$	237,000	$	—	$	—	$	—	$	—	$	237,000	$	—
Second Lien		125,000		—		—		—		—		125,000		—
Total	$	362,000	$	—	$	—	$	—	$	—	$	362,000	$	—

        During 2012 and 2011, the weighted-average interest rate for total indebtedness was 4.3% and 3.8%, respectively.

Note 7. Partners' Equity

        On August 23, 2010, Athlon SG entered into a limited partnership agreement with its management group and Apollo. On July 22, 2011, the partnership agreement was amended and restated resulting in the formation of Holdings. The amended and restated partnership agreement required all of Athlon SG's equity contributions to be contributed to Holdings. The holders of all Class A and Class B limited partner units in Athlon SG contributed these units to Holdings in exchange for equivalent units of Holdings. Apollo and Holdings' management group are Class A limited partners in Athlon. The following table shows the partnership interest in Holdings as of December 31, 2012:

		Partnership Interest
Athlon Holdings LLC	General Partner		0.0	%
Apollo Athlon Holdings LLC	Class A Partner		97.2	%
Management group	Class A Partner		2.8	%

        As of December 31, 2012, Holdings had remaining capital commitments of approximately $38.1 million from Apollo and none from management.

Note 8. Employee Benefit Plans

401(k) Plan

        Holdings made contributions to its 401(k) plan, which is a voluntary and contributory plan for eligible employees based on a percentage of employee contributions, of approximately $454 thousand

F-51

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 8. Employee Benefit Plans (Continued)

and $219 thousand during 2012 and 2011, respectively. Holdings' 401(k) plan does not allow employees to invest in securities of Holdings.

Class B Limited Partner Interests

        Holdings' limited partnership agreement provides for the issuance of Class B limited partner interests. The Class B interests entitle the holder to participate in the net profits of Holdings, but are subject to various performance criteria. Class A interest holders are entitled to a return of their initial investment plus interest compounded at 8% annually (the "Class A Preference Amount"). Upon the occurrence of a liquidity event and after the Class A Preference Amount has been satisfied, 80% and 20% of the remaining net profits will be distributed to holders of Class A interests and Class B interests, respectively. The Class B interests vest over four or five years or upon certain performance thresholds being met by Holdings. Class B interests can also vest on the occurrence of certain events such as a change in control or in some cases upon termination of employment with Holdings. The total number of Class B interests that may be issued pursuant to the partnership agreement is 100,000. As of December 31, 2012, there were 6,200 Class B interests available for issuance under the partnership agreement. Class B interests that are forfeited will again become available for issuance under the partnership agreement.

        Management evaluated the terms of the Class B interests granted during 2010, in particular the potential impact of the performance criteria on the potential value of the Class B interests, and concluded that any compensation expense related to those grants would have been nominal. Management had independent valuations of its Class B interests granted during 2012 and 2011 and recorded approximately $152 thousand and $106 thousand, respectively, of non-cash equity-based compensation expense, which was allocated to LOE and general and administrative expenses in the accompanying Consolidated Statements of Operations based on the allocation of the respective employees' cash compensation. During 2012, Holdings also capitalized approximately $93 thousand of non-cash stock-based compensation expense as a component of "Proved properties, including wells and related equipment" in the accompanying Consolidated Balance Sheets.

        The fair value of Class B interests granted was estimated on the grant date using an option pricing model based on the following assumptions for the periods indicated:

	Year Ended December 31,
	2012			2011
Expected volatility		47	%		44	%
Expected dividend yield		0	%		0	%
Expected term (in years)		1.52			1.65
Risk-free interest rate		0.23	%		0.35	%
Weighted-average grant date fair value per interest	$	128.94		$	134.84

        The expected volatility was calculated based on the average historical volatility of each company in Holdings' peer group based on historical stock price data. The expected term of the Class B interests was based on expectations about future behavior. The risk-free interest rate was based on the U.S. Treasury yield curve in effect at the grant date for a period of time commensurate with the expected term of the Class B interests.

F-52

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 8. Employee Benefit Plans (Continued)

        The following table summarizes the changes in Holdings' Class B interests for the periods indicated:

	Year Ended December 31,
	2012					2011
	Number of Class B Interests			Weighted- Average Grant Date Fair Value		Number of Class B Interests			Weighted- Average Grant Date Fair Value
Outstanding at beginning of period		68,662		$	15.93		82,153		$	—
Granted		2,195			128.94		9,050			134.84
Vested		(20,375	)		11.32		(19,046	)		3.11
Forfeited		(270	)		140.72		(3,495	)		19.13
Outstanding at end of year		50,212			22.07		68,662			15.93

        The following table provides information regarding the expected vesting of Holdings' outstanding Class B interests at December 31, 2012:

	Year of Vesting
Year of Grant	2013		2014		2015		2016		2017		Total
2010		18,664		14,497		8,664		—		—		41,825
2011		1,711		1,711		1,711		1,329		—		6,462
2012		385		385		385		385		385		1,925
Total		20,760		16,593		10,760		1,714		385		50,212

        As of December 31, 2012, Holdings had approximately $1.0 million of total unrecognized compensation cost related to unvested Class B interests, which is expected to be recognized over a weighted-average period of approximately 3.7 years. During 2012 and 2011, there were 20,375 and 19,046, respectively, Class B interests that vested, the total fair value of which was approximately $231 thousand and $59 thousand, respectively.

Note 9. Fair Value Measurements

        The book values of cash and cash equivalents, accounts receivable, and accounts payable approximate fair value due to the short-term nature of these instruments. The book values of the Holdings Credit Agreement and the Second Lien approximate fair value as the interest rates are variable. Commodity derivative contracts are marked-to-market each quarter and are thus stated at fair value in the accompanying Consolidated Balance Sheets.

Commodity Derivative Contracts

        Commodity prices are often subject to significant volatility due to many factors that are beyond Holdings' control, including but not limited to: prevailing economic conditions, supply and demand of hydrocarbons in the marketplace, actions by speculators, and geopolitical events such as wars or natural disasters. Holdings' objective is to manage its exposure to oil price risk with swaps, puts, and collars. Swaps provide a fixed price for a notional amount of sales volumes. Puts provide a fixed floor price on

F-53

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 9. Fair Value Measurements (Continued)

a notional amount of sales volumes while allowing full price participation if the relevant index price closes above the floor price. Collars provide a floor price on a notional amount of sales volumes while allowing some additional price participation if the relevant index price closes above the floor price. This participation is limited by a ceiling price specified in the contract.

        The following table summarizes open commodity derivative contracts as of December 31, 2012:

Period	Average Daily Floor Volume		Weighted- Average Floor Price		Average Daily Cap Volume		Weighted- Average Cap Price		Average Daily Swap Volume		Weighted- Average Swap Price		Asset Fair Market Value
	(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(in thousands)
2013		150	$	75.00		150	$	105.95		5,000	$	94.15	$	1,654
2014		—		—		—		—		4,950		92.65		956
2015		—		—		—		—		800		94.86		1,379
													$	3,989

        In January 2011, Holdings terminated certain oil puts that were in place at December 31, 2010 and received net proceeds of approximately $7.6 million, which is reflected as "Monetization of put options" in the "Investing activities" section of the accompanying Consolidated Statements of Cash Flows. In July and August 2011, Holdings entered into additional oil puts that included deferred premiums. These deferred premiums increased Holdings' interest expense by approximately $0.2 million during 2011. In October 2011, Holdings terminated the oil puts and entered into oil swaps that required the initial payment of premiums of approximately $2.0 million.

        Counterparty Risk.    At December 31, 2012, Holdings had committed 10% or greater (in terms of fair market value) of its oil derivative contracts in asset positions from the following counterparties:

Counterparty	Fair Market Value of Oil Derivative Contracts Committed
	(in thousands)
BNP Paribas	$	3,660
Royal Bank of Canada		711
Scotiabank		617

        Holdings does not require collateral from its counterparties for entering into financial instruments, so in order to mitigate the credit risk associated with financial instruments, Holdings enters into master netting agreements with certain counterparties. The master netting agreement is a standardized, bilateral contract between a given counterparty and Holdings. Instead of treating each financial transaction between the counterparty and Holdings separately, the master netting agreement enables the counterparty and Holdings to aggregate all financial trades and treat them as a single agreement. This arrangement is intended to benefit Holdings in two ways: (1) default by a counterparty under one financial trade can trigger rights to terminate all financial trades with such counterparty; and (2) netting of settlement amounts reduces Holdings' credit exposure to a given counterparty in the event of close-out. Holdings' accounting policy is to not offset fair value amounts between different counterparties for derivative instruments in the accompanying Consolidated Balance Sheets.

F-54

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 9. Fair Value Measurements (Continued)

Tabular Disclosures of Fair Value Measurements

        The following table summarizes the fair value of Holdings' derivative instruments as of the dates indicated (in thousands):

	Asset Derivatives					Liability Derivatives
		Fair Value					Fair Value
	Balance Sheet Location	December 31, 2012		December 31, 2011		Balance Sheet Location	December 31, 2012		December 31, 2011
Derivatives not designated as hedges
Commodity derivative contracts	Derivatives—current	$	2,246	$	—	Derivatives—current	$	592	$	5,908
Commodity derivative contracts	Derivatives—noncurrent		2,854		2,503	Derivatives—noncurrent		519		2,554
Total derivatives not designated as hedges		$	5,100	$	2,503		$	1,111	$	8,462

        The following table summarizes the effect of derivative instruments not designated as hedges on the accompanying Consolidated Statements of Operations for the periods indicated (in thousands):

		Amount of Loss (Gain) Recognized in Income
		Year ended December 31,
	Location of Loss (Gain) Recognized in Income
Derivatives Not Designated as Hedges		2012			2011
Commodity derivative contracts	Derivative fair value loss (gain)	$	(9,293	)	$	7,959

Fair Value Hierarchy

        Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. GAAP establishes a three-tier fair value hierarchy, which prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are defined as follows:

•

Level 1—Inputs such as unadjusted, quoted prices that are available in active markets for identical assets or liabilities.

•

Level 2—Inputs, other than quoted prices within Level 1, that are either directly or indirectly observable.

•

Level 3—Inputs that are unobservable for use when little or no market data exists requiring the use of valuation methodologies that result in management's best estimate of fair value.

        As required by GAAP, Holdings utilizes the most observable inputs available for the valuation technique used. The financial assets and liabilities are classified in their entirety based on the lowest

F-55

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 9. Fair Value Measurements (Continued)

level of input that is of significance to the fair value measurement. Holdings' assessment of the significance of a particular input to the fair value measurement requires judgment and may affect the valuation of the financial assets and liabilities and their placement within the fair value hierarchy levels. The following methods and assumptions were used to estimate the fair values of Holdings' assets and liabilities that are accounted for at fair value on a recurring basis:

•

Level 2—Fair values of swaps were estimated using a combined income-based and market-based valuation methodology based upon forward commodity price curves obtained from independent pricing services. Holdings' collars and puts are average value options. Settlement is determined by the average underlying price over a predetermined period of time. Holdings uses observable inputs in an option pricing valuation model to determine fair value such as: (1) current market and contractual prices for the underlying instruments; (2) quoted forward prices for oil and natural gas; (3) interest rates, such as a LIBOR curve for a term similar to the commodity derivative contract; and (4) appropriate volatilities.

        Holdings adjusts the valuations from the valuation model for nonperformance risk. For commodity derivative contracts which are in an asset position, Holdings uses the counterparty's credit default swap rating. For commodity derivative contracts which are in a liability position, Holdings uses the average credit default swap rating of its peer companies as Holdings does not have its own credit default swap rating. All fair values have been adjusted for nonperformance risk resulting in an increase in the net commodity derivative asset of approximately $0.1 million as of December 31, 2012 and a decrease of the net commodity derivative liability of approximately $0.5 million as of December 31, 2011.

        The following table sets forth Holdings' assets and liabilities that were accounted for at fair value on a recurring basis as of the dates indicated:

				Fair Value Measurements at Reporting Date Using
Description	Asset (liability), net			Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)			Significant Unobservable Inputs (Level 3)
	(in thousands)
As of December 31, 2012
Oil derivative contracts—swaps	$	4,069		$	—	$	4,069		$	—
Oil derivative contracts—collars and puts		(80	)		—		(80	)		—
Total	$	3,989		$	—	$	3,989		$	—
As of December 31, 2011
Oil derivative contracts—swaps	$	(5,392	)	$	—	$	(5,392	)	$	—
Oil derivative contracts—collars and puts		(567	)		—		—			(567	)
Total	$	(5,959	)	$	—	$	(5,392	)	$	(567	)

        Holdings' oil collars were classified as Level 3 in the fair value hierarchy as of December 31, 2011. Beginning in 2012, these contracts were classified as Level 2 in the fair value hierarchy as a result of

F-56

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 9. Fair Value Measurements (Continued)

Holdings' ability to obtain appropriate volatilities. The following table summarizes the changes in the fair value of Holdings' Level 3 assets and liabilities that were previously classified as Level 3 for the periods indicated:

	Fair Value Measurements Using Significant Unobservable Inputs (Level 3)
	Oil Derivative Contracts— Collars and Puts
	(in thousands)
Balance at January 1, 2011	$	7,475
Total gains (losses):
Included in earnings		(461	)
Monetization of put options		(7,625	)
Purchases (premiums paid)		44
Balance at December 31, 2011		(567	)
Transfers out of Level 3		567
Balance at December 31, 2012	$	—

        Since Holdings does not use hedge accounting for its commodity derivative contracts, all gains and losses on its Level 3 assets and liabilities are included in "Derivative fair value loss (gain)" in the accompanying Consolidated Statements of Operations.

Note 10. Related Party Transactions

Transaction Fee Agreement

        Holdings is a party to a Transaction Fee Agreement, dated August 23, 2010, which requires Holdings to pay a fee to Apollo equal to 2% of the total equity contributed to Holdings, as defined in the agreement, in exchange for consulting and advisory services provided by Apollo. In October 2012, Apollo assigned its rights and obligations under the Transaction Fee Agreement to Apollo Global Securities, LLC. In December 2012, Holdings incurred a transaction fee payable to Apollo Global Securities, LLC of $0.8 million related to a $40 million capital contribution received from Apollo. Upon the closing of the SandRidge acquisition in January 2011, Athlon SG incurred a transaction fee payable to Apollo of approximately $2.3 million. Upon the closing of the Element acquisition in October 2011, Athlon FE incurred a transaction fee payable to Apollo of approximately $4.3 million. All transaction fees incurred under the Transaction Fee Agreement are included in "Acquisition costs" in the accompanying Consolidated Statements of Operations during the period incurred.

Services Agreement

        Holdings is also a party to a Services Agreement, dated August 23, 2010, which requires Holdings to further compensate Apollo for consulting and advisory services equal to a minimum of $62,500 per quarter or 1% of net income before interest, income taxes, and DD&A, not to exceed $500,000 in any calendar year. The Services Agreement also provides for reimbursement to Apollo for any reasonable out-of-pocket expenses incurred while performing under the Services Agreement. During 2012 and

F-57

ATHLON HOLDINGS LP

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Continued)

Note 10. Related Party Transactions (Continued)

2011, Holdings incurred approximately $493 thousand and $411 thousand, respectively, of fees under the Services Agreement, which is included in "General and administrative expenses" in the accompanying Consolidated Statements of Operations.

Note 11. Subsequent Events

        In January 2013, Holdings increased the borrowing base under the Holdings Credit Agreement to $295 million.

        During February 2013, Holdings entered into additional oil swaps. The following table summarizes open commodity derivative contracts as of March 8, 2013:

Period	Average Daily Floor Volume		Weighted- Average Floor Price		Average Daily Cap Volume		Weighted- Average Cap Price		Average Daily Swap Volume		Weighted- Average Swap Price
	(Bbl)		(per Bbl)		(Bbl)		(per Bbl)		(Bbl)		(per Bbl)
2013		150	$	75.00		150	$	105.95		5,500	$	94.50
2014		—		—		—		—		5,450		92.83
2015		—		—		—		—		1,300		93.18

        In February 2013, Holdings also entered into basis differential swaps for 5,000 Bbls/D at $1.20/Bbl for March through December 2013.

        These financial statements considered subsequent events through March 8, 2013, the date the consolidated financial statements were available to be issued.

F-58

ATHLON HOLDINGS LP

SUPPLEMENTARY INFORMATION

Capitalized Costs and Costs Incurred Relating to Oil and Natural Gas Producing Activities

        The capitalized cost of oil and natural gas properties was as follows as of the dates indicated:

	December 31,
	2012			2011
	(in thousands)
Properties and equipment, at cost—full cost method:
Proved properties, including wells and related equipment	$	788,571		$	399,205
Unproved properties		89,860			125,036
Accumulated depletion, depreciation, and amortization		(73,824	)		(19,589	)
	$	804,607		$	504,652

        The following table summarizes costs incurred related to oil and natural gas properties for the periods indicated:

	Year ended December 31,
	2012		2011
	(in thousands)
Acquisitions:
Proved propertiesa	$	42,122	$	287,400
Unproved propertiesb		38,908		130,273
Total acquisitions		81,030		417,673
Development:
Drilling and exploitationc		201,174		71,403
Total development		201,174		71,403
Exploration:
Drilling and exploitationd		75,008		17,829
Total exploration		75,008		17,829
Total costs incurred	$	357,212	$	506,905

^a

Includes asset retirement obligations incurred of approximately $60 thousand and $3.3 million during 2012 and 2011, respectively.

^b

Costs incurred for unproved properties are excluded from the amortization base.

^c

Includes asset retirement obligations incurred of approximately $606 thousand and $108 thousand during 2012 and 2011, respectively.

^d

Includes asset retirement obligations incurred of approximately $209 thousand and $58 thousand during 2012 and 2011, respectively.

Oil & Natural Gas Producing Activities—Unaudited

        All of Holdings' results of operations relate to oil and natural gas producing activities. Holdings only has one cost center, which is the Permian Basin in West Texas. Holdings average depletion rate per BOE of production was $21.03 and $20.32 for 2012 and 2011, respectively.

F-59

ATHLON HOLDINGS LP

SUPPLEMENTARY INFORMATION (Continued)

        The estimates of Holdings' proved reserves, which are located entirely within the United States, were prepared in accordance with rules and regulations established by the FASB. Proved oil and natural gas reserve quantities are based on internal estimates reviewed by independent petroleum engineers.

        Future prices received for production and future production costs may vary, perhaps significantly, from the prices and costs assumed for purposes of these estimates. There can be no assurance that the proved reserves will be developed within the periods assumed or that prices and costs will remain constant. Actual production may not equal the estimated amounts used in the preparation of reserve projections. Estimates of future net cash flows from Holdings' properties, and the representative value thereof, were made using 12-month first-day-of-the-month oil and natural gas average prices, as adjusted for basis or location differentials, held constant over the life of the reserves. Prices used in estimating Holdings' future net cash flows were as follows as of the dates indicated:

	December 31,
	2012		2011
Oil (per Bbl)	$	94.71	$	93.25
Natural gas (per Mcf)		2.75		3.53

        Net future cash inflows have not been adjusted for commodity derivative contracts outstanding at the end of the year. Future cash inflows are reduced by estimated production and development costs, which are based on year-end economic conditions and held constant throughout the life of the properties, and the estimated effect of future income taxes due to the Texas margin tax. Future federal income taxes have not been deducted from future net revenues in the calculation of Holdings' standardized measure as each partner is separately taxed on his share of Holdings' taxable income.

        There are numerous uncertainties inherent in estimating quantities of proved reserves and in projecting future rates of production and timing of development expenditures. Oil and natural gas reserve engineering is and must be recognized as a subjective process of estimating underground accumulations of oil and natural gas that cannot be measured in any exact way, and estimates of other engineers might differ materially from those included herein. The accuracy of any reserve estimate is a function of the quality of available data and engineering, and estimates may justify revisions based on the results of drilling, testing, and production activities. Accordingly, reserve estimates are often materially different from the quantities of oil and natural gas that are ultimately recovered. Reserve estimates are integral to management's analysis of impairment of oil and natural gas properties and the calculation of DD&A on these properties.

F-60

ATHLON HOLDINGS LP

SUPPLEMENTARY INFORMATION (Continued)

        Holdings' estimated net quantities of proved reserves were as follows as of the dates indicated:

	December 31,
	2012		2011
Proved developed reserves:
Oil (MBbls)		14,470		7,942
Natural gas (MMcf)		31,965		14,063
Natural gas liquids (MBbls)		5,900		3,211
Combined (MBOE)		25,698		13,496
Proved undeveloped reserves:
Oil (MBbls)		34,953		18,030
Natural gas (MMcf)		71,718		37,497
Natural gas liquids (MBbls)		13,375		8,338
Combined (MBOE)		60,281		32,618
Proved reserves:
Oil (MBbls)		49,423		25,972
Natural gas (MMcf)		103,683		51,560
Natural gas liquids (MBbls)		19,275		11,549
Combined (MBOE)		85,979		46,114

        The changes in Holdings' proved reserves were as follows for the periods indicated:

	Oil (MBbls)			Natural Gas (MMcf)			Natural Gas Liquids (MBbls)			Oil Equivalent (MBOE)
Balance at December 31, 2010		—			—			—			—
Purchases of minerals-in-place		21,308			39,179			8,935			36,773
Extensions and discoveries		4,200			10,064			2,285			8,162
Revisions of previous estimates		1,020			3,334			568			2,143
Production		(556	)		(1,017	)		(239	)		(964	)
Balance, December 31, 2011		25,972			51,560			11,549			46,114
Purchases of minerals-in-place		5,203			5,874			1,162			7,344
Extensions and discoveries		23,471			56,736			10,525			43,452
Revisions of previous estimates1		(3,766	)		(7,324	)		(3,366	)		(8,352	)
Production		(1,457	)		(3,163	)		(595	)		(2,579	)
Balance, December 31, 2012		49,423			103,683			19,275			85,979

¹

During 2012, Holdings experienced negative revisions of previous estimates, 7,185 MBOE of which was related to proved undeveloped locations that are not currently scheduled to be drilled within the next five years.

        The following is a standardized measure of the discounted net future cash flows and changes applicable to proved reserves. The future cash flows are discounted at 10% per year and assume continuation of existing economic conditions.

        The standardized measure of discounted future net cash flows, in management's opinion, should be examined with caution. The basis for this table is the reserve studies prepared by independent petroleum engineering consultants, which contain imprecise estimates of quantities and rates of

F-61

ATHLON HOLDINGS LP

SUPPLEMENTARY INFORMATION (Continued)

production of reserves. Revisions of previous year estimates can have a significant impact on these results. Also, exploration costs in one year may lead to significant discoveries in later years and may significantly change previous estimates of proved reserves and their valuation. Therefore, the standardized measure of discounted future net cash flow is not necessarily indicative of the fair value of Holdings' proved oil and natural gas properties.

        The data presented should not be viewed as representing the expected cash flow from or current value of, existing proved reserves since the computations are based on a large number of estimates and arbitrary assumptions. Reserve quantities cannot be measured with precision and their estimation requires many judgmental determinations and frequent revisions. Actual future prices and costs are likely to be substantially different from the prices and costs utilized in the computation of reported amounts.

        Holdings' standardized measure of discounted estimated future net cash flows was as follows as of the dates indicated:

	December 31,
	2012			2011
	(in thousands)
Future cash inflows	$	5,361,058		$	3,155,756
Future production costs		(1,811,514	)		(972,343	)
Future development costs		(1,060,785	)		(569,672	)
Future income taxes		(37,527	)		(22,090	)
Future net cash flows		2,451,232			1,591,651
10% annual discount		(1,600,318	)		(1,010,494	)
Standardized measure of discounted estimated future net cash flows	$	850,914		$	581,157

F-62

ATHLON HOLDINGS LP

SUPPLEMENTARY INFORMATION (Continued)

        The changes in Holdings' standardized measure of discounted estimated future net cash flows were as follows for the periods indicated:

	Year ended December 31,
	2012			2011
	(in thousands)
Net change in prices and production costs	$	(109,214	)	$	73,093
Purchases of minerals-in-place		81,304			394,248
Extensions, discoveries, and improved recovery		376,493			101,396
Revisions of previous quantity estimates		(189,505	)		27,499
Production, net of production costs		(121,170	)		(47,626	)
Previously estimated development costs incurred during the period		119,361			43,994
Accretion of discount		59,144			20,072
Change in estimated future development costs		60,210			(22,239	)
Net change in income taxes		(5,378	)		(2,809	)
Change in timing and other		(1,488	)		(6,471	)
Net change in standardized measure		269,757			581,157
Standardized measure, beginning of year		581,157			—
Standardized measure, end of year	$	850,914		$	581,157

F-63

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

To the Board of Supervisors and Partners
Athlon Holdings LP

        We have audited the accompanying carve out balance sheet of Element Petroleum, LP's ("Element") Permian Basin Operations as defined in Note 1 as of September 30, 2011, and the related carve out statements of operations, owner's net equity, and cash flows for the nine months then ended. These financial statements are the responsibility of Athlon Holdings LP's management. Our responsibility is to express an opinion on these financial statements based on our audit.

        We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the financial statements are free of material misstatement. We were not engaged to perform an audit of Element's internal control over financial reporting. Our audit included consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of Element's internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audit provides a reasonable basis for our opinion.

        In our opinion, the financial statements referred to above present fairly, in all material respects, the carve out financial position of Element's Permian Basin Operations included in the Purchase and Sale Agreement with Athlon FE Operating LLC at September 30, 2011 and the carve out results of its operations and its cash flows for the nine months then ended in conformity with U.S. generally accepted accounting principles.

/s/ UHY LLP

Houston, Texas
May 16, 2012

F-64

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

CARVE OUT BALANCE SHEET

(in thousands)

	September 30, 2011
ASSETS
Current assets:
Accounts receivable	$	2,253
Inventory		271
Total current assets		2,524
Properties and equipment, at cost—successful efforts method:
Proved properties, including wells and related equipment		121,568
Unproved properties		13,515
Accumulated depletion, depreciation, and amortization		(30,732	)
		104,351
Other property and equipment		939
Accumulated depreciation		(173	)
		766
Other		73
Total assets	$	107,714
LIABILITIES AND OWNER'S NET EQUITY
Current liabilities:
Accounts payable	$	6,501
Accrued liabilities:
Lease operating		170
Production, severance, and ad valorem taxes		401
Development capital		2,516
Revenues payable		1,802
Other		305
Total current liabilities		11,695
Asset retirement obligations		1,754
Total liabilities		13,449
Commitments and contingencies (see Note 3)
Owner's net equity		94,265
Total liabilities and owner's net equity	$	107,714

The accompanying notes are an integral part of these carve out financial statements.

F-65

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

CARVE OUT STATEMENT OF OPERATIONS

(in thousands)

	Nine Months Ended September 30, 2011
Revenues:
Oil	$	17,406
Natural gas		6,109
Management fees		422
Total revenues		23,937
Expenses:
Production:
Lease operating		1,962
Production, severance, and ad valorem taxes		1,590
Depletion, depreciation, and amortization		5,594
General and administrative		1,897
Accretion		62
Total expenses		11,105
Operating income		12,832
Interest, net		1
Net income	$	12,833

The accompanying notes are an integral part of these carve out financial statements.

F-66

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

CARVE OUT STATEMENT OF CHANGES IN OWNER'S NET EQUITY

(in thousands)

Balance at December 31, 2010	$	45,041
Net contributions from owner		36,391
Net income		12,833
Balance at September 30, 2011	$	94,265

The accompanying notes are an integral part of these carve out financial statements.

F-67

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

CARVE OUT STATEMENT OF CASH FLOWS

(in thousands)

	Nine Months Ended September 30, 2011
Cash flows from operating activities:
Net income	$	12,833
Adjustments to reconcile net income to net cash provided by operating activities:
Depletion, depreciation, and amortization		5,594
Accretion		62
Changes in operating assets and liabilities:
Accounts receivable		(1,563	)
Inventory		89
Accounts payable		(1,118	)
Other current liabilities		3,470
Net cash provided by operating activities		19,367
Cash flows from investing activities:
Acquisition of oil and natural gas properties		(2,085	)
Development of oil and natural gas properties		(53,640	)
Other		(33	)
Net cash used in investing activities		(55,758	)
Cash flows from financing activities:
Net contributions from owner		36,391
Net cash provided by financing activities		36,391
Increase (decrease) in cash and cash equivalents		—
Cash and cash equivalents, beginning of period		—
Cash and cash equivalents, end of period	$	—
Non-cash investing activities:
Establishment of asset retirement obligations	$	639

The accompanying notes are an integral part of these carve out financial statements.

F-68

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS

Note 1. Description of Business and Basis of Presentation

        Athlon FE Energy LP together with its subsidiary, ("Athlon FE"), a Delaware limited partnership, was formed on July 22, 2011 (the "date of inception"), and is the holding company for Athlon FE Operating LLC (the "Company"), which was also formed on July 22, 2011. Athlon FE seeks to execute a low-risk "acquire and exploit" strategy by establishing a footprint in proven oil and natural gas basins with initial acquisitions of mature producing properties that have long-lived, predictable reserves in the onshore continental United States. On October 3, 2011, the Company acquired certain oil and natural gas properties from Element Petroleum, LP ("Element") in the Permian Basin of West Texas (the "Permian Basin Operations") for approximately $253.2 million.

        The accompanying carve out financial statements and related notes thereto represent the financial position, results of operations, changes in owner's net equity, and cash flows of the Permian Basin Operations. The carve out financial statements have been prepared in accordance with Regulation S-X, Article 3, "General instructions as to financial statements" and Staff Accounting Bulletin ("SAB") Topic 1-B, "Allocations of Expenses and Related Disclosure in Financial Statements of Subsidiaries, Divisions or Lesser Business Components of Another Entity". Certain expenses incurred by Element are only indirectly attributable to its ownership of the Permian Basin Operations as Element owns interests in numerous other oil and natural gas properties. As a result, certain assumptions and estimates were made in order to allocate a reasonable share of such expenses to the Permian Basin Operations so that the accompanying carve out financial statements reflect substantially all the costs of doing business borne by Element on behalf of the Permian Basin Operations. These allocations may not be indicative of the cost of future operations or the amount of future allocations. The allocations and related estimates and assumptions are described more fully in "Note 2. Summary of Significant Accounting Policies" and "Note 5. Related Party Transactions".

Note 2. Summary of Significant Accounting Policies

        The accompanying carve out financial statements were derived from the accounting records of Element.

Allocation of Costs

        The accompanying carve out financial statements have been prepared in accordance with SAB Topic 1-B. These rules require allocations of costs for salaries and benefits, depreciation, rent, accounting, legal services, and other expenses. Element has allocated general and administrative expenses to the Permian Basin Operations using an average of its proportionate share of Element's consolidated oil and natural gas revenues, capital expenditures, and well count. Management believes the allocation methodologies used are reasonable and result in an allocation of the cost of doing business borne by Element on behalf of the Permian Basin Operations. These allocations may not be indicative of the cost of future operations or the amount of future allocations.

Use of Estimates

        Preparing carve out financial statements in conformity with accounting principles generally accepted in the United States ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, and expenses, and the disclosure of contingent assets and liabilities in the carve out financial statements. Also, certain amounts in the accompanying carve out financial statements have been allocated in a way that management believes is

F-69

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

reasonable and consistent in order to depict the historical financial position, results of operations, and cash flows of the Permian Basin Operations on a stand-alone basis. Although management believes these estimates are reasonable, actual results could differ from these estimates.

        Estimates made in preparing these carve out financial statements include, among other things, estimates of the proved oil and natural gas reserve volumes used in calculating depletion, depreciation, and amortization ("DD&A") expense; the estimated future cash flows and fair value of properties used in determining the need for any impairment write-down; operating costs accrued; volumes and prices for revenues accrued; and the timing and amount of future abandonment costs used in calculating asset retirement obligations. Changes in the assumptions used could have a significant impact on results in future periods.

Cash and Cash Equivalents

        Element provided cash as needed to support the Permian Basin Operations and collected cash from sales of production. Consequently, the accompanying Carve Out Balance Sheet do not include any cash balances. Net cash paid from Element to the Permian Basin Operations is reflected as net contributions from owner on the accompanying Carve Out Statement of Owner's Net Equity and Carve Out Statement of Cash Flows.

Accounts Receivable

        Trade accounts receivable, which are primarily from oil and natural gas sales, are recorded at the invoiced amount and do not bear interest. Element routinely reviews outstanding accounts receivable balances, assesses the financial strength of its customers, and records a reserve for amounts not expected to be fully recovered. Actual balances are not applied against the reserve until substantially all collection efforts have been exhausted. At September 30, 2011, the Permian Basin Operations had no allowance for doubtful accounts.

Properties and Equipment

        Oil and Natural Gas Properties.    The Permian Basin Operations use the successful efforts method of accounting for its oil and natural gas properties under the provisions of the "Financial Accounting and Reporting by Oil and Gas Producing Companies" topic of the Financial Accounting Standards Board's (the "FASB") Accounting Standards Codification (the "ASC"). Under this method, all costs associated with productive and nonproductive development wells are capitalized. Exploration expenses, including geological and geophysical expenses and delay rentals, are charged to expense as incurred. Costs associated with drilling exploratory wells are initially capitalized pending determination of whether the well is economically productive or nonproductive.

        If an exploratory well does not find reserves or does not find reserves in a sufficient quantity as to make them economically producible, the previously capitalized costs would be expensed in the accompanying Carve Out Statement of Operations and shown as an adjustment to net income in the "Operating activities" section of the accompanying Carve Out Statement of Cash Flows in the period in which the determination was made. If an exploratory well finds reserves but they cannot be classified as proved, the associated cost continues to be capitalized as long as the well has found a sufficient quantity of reserves to justify its completion as a producing well and sufficient progress is being made in assessing the reserves and the operating viability of the project. If subsequently it is determined that

F-70

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

these conditions do not continue to exist, all previously capitalized costs associated with the exploratory well would be expensed and shown as an adjustment to net income in the "Operating activities" section of the accompanying Carve Out Statement of Cash Flows in the period in which the determination was made. Re-drilling or directional drilling in a previously abandoned well is classified as development or exploratory based on whether it is in a proved or unproved reservoir. Costs for repairs and maintenance to sustain or increase production from the existing producing reservoir are charged to expense as incurred. Costs to recomplete a well in a different unproved reservoir are capitalized pending determination that economic reserves have been added. If the recompletion is unsuccessful, the costs would be charged to expense. All capitalized costs associated with both development and exploratory wells are shown as "Development of oil and natural gas properties" in the "Investing activities" section of the accompanying Carve Out Statement of Cash Flows.

        Significant tangible equipment added or replaced that extends the useful or productive life of the property is capitalized. Costs to construct facilities or increase the productive capacity from existing reservoirs are capitalized. Capitalized costs are amortized on a unit-of-production basis over the remaining life of proved developed reserves or total proved reserves, as applicable. Natural gas volumes are converted to barrels of oil equivalent ("BOE") at the rate of six thousand cubic feet ("Mcf") of natural gas to one barrel ("Bbl") of oil. This convention is not an equivalent price basis and there may be a large difference in value between an equivalent volume of oil versus an equivalent volume of natural gas.

        DD&A of capitalized costs for producing oil and natural gas properties is provided for using the unit-of-production method based on estimates of proved oil and natural gas reserves on a field-by-field basis. Costs of significant nonproducing properties, wells in progress of being drilled, and development projects are excluded from depletion until such time as the related project is developed and proved reserves are established or impairment is determined. The costs of retired, sold, or abandoned properties that constitute part of an amortization base are charged or credited, net of proceeds received, to accumulated DD&A.

        Reserve engineers estimate the reserves of the Permian Basin Operations annually on December 31.

        In accordance with the provisions of the "Accounting for the Impairment or Disposal of Long-Lived Assets" topic of the ASC, management assesses the need for an impairment of long-lived assets to be held and used, including proved oil and natural gas properties, whenever events and circumstances indicate that the carrying value of the asset may not be recoverable. If impairment is indicated based on a comparison of the asset's carrying value to its undiscounted expected future net cash flows, then an impairment charge is recognized to the extent the asset's carrying value exceeds its fair value. Expected future net cash flows are based on existing proved reserves, forecasted production information, and management's outlook of future commodity prices. Any impairment charge incurred is expensed and reduces the net basis in the asset. Management aggregates proved property for impairment testing the same way as for calculating DD&A. The price assumptions used to calculate undiscounted cash flows is based on judgment. Management uses prices consistent with the prices it believes a market participant would use in bidding on acquisitions and/or assessing capital projects. These price assumptions are critical to the impairment analysis as lower prices could trigger impairment.

F-71

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

        Unproved properties, the majority of which relate to the acquisition of leasehold interests, are assessed for impairment on a property-by-property basis for individually significant balances and on an aggregate basis for individually insignificant balances. If the assessment indicates impairment, a loss is recognized by providing a valuation allowance at the level at which impairment was assessed. The impairment assessment is affected by economic factors such as the results of exploration activities, commodity price outlooks, remaining lease terms, and potential shifts in business strategy employed by management. In the case of individually insignificant balances, the amount of the impairment loss recognized is determined by amortizing the portion of these properties' costs which management believes will not be transferred to proved properties over the remaining life of the lease.

        Amounts shown in the accompanying Carve Out Balance Sheet as "Proved properties, including wells and related equipment" consisted of the following as of the date indicated:

	September 30, 2011
	(in thousands)
Proved leasehold costs	$	15,342
Wells and related equipment—Completed		97,029
Wells and related equipment—In process		9,197
Total proved properties	$	121,568

        Other Property and Equipment.    Other property and equipment is carried at cost. Depreciation is expensed on a straight-line basis over estimated useful lives, which range from three to seven years. Gains or losses from the disposal of other property and equipment are recognized in the period realized.

Asset Retirement Obligations

        Management applies the provisions of the "Accounting for Asset Retirement Obligation" topic of the ASC. The Permian Basin Operations have significant obligations under its lease agreements and federal regulation to remove its equipment and restore land at the end of oil and natural gas production operations. These asset retirement obligations are primarily associated with plugging and abandoning wells and land remediation. Estimating the future restoration and removal cost is difficult and requires management to make estimates and judgments because most of the removal obligations are many years in the future and contracts and regulation often have vague descriptions of what constitutes removal. Asset removal technologies and costs are constantly changing, as are regulatory, political, environmental, safety, and public relations considerations. At the time the well is drilled, the Permian Basin Operations record a separate liability for the estimated fair value of its asset retirement obligations, with an offsetting increase to the related oil and natural gas properties representing asset retirement costs in the accompanying Carve Out Balance Sheet. The cost of the related oil and natural gas asset, including the asset retirement cost, is included in the Permian Basin Operations' capitalized property costs. The estimated fair value of an asset retirement obligation is the present value of the expected future cash outflows required to satisfy the asset retirement obligations discounted at Element's credit-adjusted, risk-free interest rate. Accretion expense is recognized over time as the discounted liability is accreted to its expected settlement value.

F-72

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

        Inherent to the present-value calculation are numerous estimates, assumptions, and judgments, including, but not limited to: the ultimate settlement amounts, inflation factors, credit-adjusted, risk-free rates, timing of settlement, and changes in the legal, regulatory, environmental, and political environments. To the extent future revisions to these assumptions affect the present value of the abandonment liability, management makes corresponding adjustments to both the asset retirement obligation and the related oil and natural gas property asset balance. Increases in the discounted asset retirement obligations resulting from the passage of time are reflected as additional accretion expense in the accompanying Carve Out Statement of Operations. Please read "Note 4. Asset Retirement Obligations" for additional information.

Owner's Net Equity

        The change in net assets that is not attributable to current period earnings is reflected as net contributions from owner for that period. As the Permian Basin Operations were not a separate legal entity during the period covered by these carve out financial statements, none of Element's debt is directly attributable to its ownership of the Permian Basin Operations, and no formal intercompany financing arrangement exists related to the Permian Basin Operations. Additionally, as debt cannot be specifically ascribed to the Permian Basin Operations, the accompanying Carve Out Statement of Operations do not include any allocation of interest expense incurred by Element related to the Permian Basin Operations.

Segment Reporting

        The Permian Basin Operations operate in only one industry: the oil and natural gas exploration and production industry in the United States. All revenues are derived from customers located in the United States.

Major Customers / Concentration of Credit Risk

        The following purchasers accounted for 10% or greater of the sales of production for the period indicated and the corresponding outstanding accounts receivable balance as of the date indicated:

	Percentage of Total Sales of Production for the			Outstanding Accounts Receivable Balance
Purchaser	Nine Months Ended September 30, 2011			As of September 30, 2011
				(in thousands)
Pecos Gathering		58	%	$	(10	)
DCP Midstream		15	%		424
LPC Crude Oil		16	%		747

Oil and Natural Gas Revenue Recognition

        Oil and natural gas revenues are recognized as oil and natural gas is produced and sold, net of royalties. Royalties are incurred based upon the actual price received from the sales. To the extent actual volumes and prices of oil and natural gas are unavailable for a given reporting period because of timing or information not received from third parties, the expected sales volumes and prices for those

F-73

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 2. Summary of Significant Accounting Policies (Continued)

properties are estimated and recorded as "Accounts receivable" in the accompanying Carve Out Balance Sheet. Natural gas revenues are recorded using the sales method of accounting whereby revenue is recognized based on actual sales of natural gas rather than the Permian Basin Operations' proportionate share of natural gas production. If the Permian Basin Operations' overproduced imbalance position (i.e., the Permian Basin Operations have cumulatively been over-allocated production) is greater than its share of remaining reserves, a liability would be recorded for the excess at period-end prices unless a different price is specified in the contract in which case that price is used. At September 30, 2011, the Permian Basin Operations had no oil inventories in pipelines or tanks and it had no natural gas imbalances. Revenue is not recognized for oil production in tanks.

Earnings Per Share

        During the period presented, the Permian Basin Operations were wholly owned by Element. Accordingly, earnings per share is not presented.

Fair Value of Financial Instruments

        Financial instruments in the accompanying Carve Out Balance Sheet include accounts receivable and accounts payable. The book values of accounts receivable and accounts payable approximate fair value due to the short-term nature of these instruments.

New Accounting Pronouncements

        In May 2011, the FASB issued Accounting Standards Update ("ASU") 2011-04, "Amendments to Achieve Common Fair Value Measurements and Disclosure Requirements in U.S. GAAP and IFRSs". ASU 2011-04 amended ASC 820 to converge the fair value measurement guidance in GAAP and International Financial Reporting Standards. Certain of the amendments clarify the application of existing fair value measurement requirements, while other amendments change a particular principle in ASC 820. In addition, ASU 2011-04 requires additional fair value disclosures. The amendments will be applied prospectively and are effective for annual periods beginning after December 15, 2011. Management does not believe the adoption of this guidance will have a material impact on the Permian Basin Operations' financial position, results of operations, or liquidity.

        In December 2011, the FASB issued ASU 2011-11, "Disclosures about offsetting Assets and Liabilities" requiring additional disclosure about offsetting and related arrangements. ASU 2011-11 is effective retrospectively for annual reporting periods beginning on or after January 1, 2013. The adoption of ASU 2011-11 will not impact the Permian Basin Operations' position, results of operations, or liquidity.

        No other new accounting pronouncements issued or effective during 2011 had or are expected to have a material impact on the Permian Basin Operations' carve out financial statements.

Note 3. Commitments and Contingencies

        The Permian Basin Operations are subject to various possible contingencies. Such contingencies include environmental issues and other matters. Although management believes it has complied with the various laws and regulations, administrative rulings and interpretations thereof, adjustments could be required as new interpretations and regulations are issued. In addition, production rates and

F-74

ELEMENT PETROLEUM, LP PERMIAN BASIN OPERATIONS

NOTES TO CARVE OUT FINANCIAL STATEMENTS (Continued)

Note 3. Commitments and Contingencies (Continued)

environmental matters are subject to regulation by various federal and state agencies. Additionally, the Permian Basin Operations have contractual obligations related to future plugging and abandonment expenses on oil and natural gas properties as discussed in "Note 4. Asset Retirement Obligations".

Note 4. Asset Retirement Obligations

        Asset retirement obligations relate to future plugging and abandonment expenses on oil and natural gas properties and related facilities disposal. The following table summarizes the changes in the Permian Basin Operations' asset retirement obligations for the period indicated:

	Nine Months Ended September 30, 2011
	(in thousands)
Balance at beginning of period	$	1,053
Acquisition of properties		—
Wells drilled		638
Accretion of discount		62
Revisions of previous estimates		1
Balance at end of period	$	1,754

Note 5. Related Party Transactions

        The employees supporting the operations of the Permian Basin Operations are employees of Element's management company. Accordingly, Element recognizes all employee-related expenses and liabilities in its consolidated financial statements. In addition to employee payroll-related expenses, Element incurred general and administrative expenses related to leasing office space and other corporate overhead expenses during the period covered by these carve out financial statements. For purposes of deriving the accompanying carve out financial statements, Element allocated general and administrative expenses to the Permian Basin Operations using an average of its proportionate share of Element's consolidated oil and natural gas revenues, capital expenditures, and well count. For the nine months ended September 30, 2011, the portion of Element's consolidated general and administrative expenses allocated to the Permian Basin Operations was 60.4%, or approximately $1.9 million.

Note 6. Subsequent Events

        These carve out financial statements considered subsequent events through May 16, 2012, the date the financial statements were available to be issued. No subsequent events requiring recognition or disclosure have occurred.

F-75

15,789,474 Shares

Athlon Energy Inc.

Common Stock

PROSPECTUS

                        , 2013

Citigroup
Goldman, Sachs & Co.
BofA Merrill Lynch
UBS Investment Bank
Wells Fargo Securities
Barclays
Credit Suisse
RBC Capital Markets
Scotiabank / Howard Weil
Tudor, Pickering, Holt & Co.
Apollo Global Securities
CIBC
Credit Agricole CIB
FBR
Lebenthal Capital Markets
Mitsubishi UFJ Securities
Simmons & Company
International
Stephens Inc.

Until                        , 2013 (25 days after the date of this prospectus), all dealers that buy, sell or trade our common stock, whether or not participating in this offering, may be required to deliver a prospectus. This is in addition to the dealers' obligation to deliver a prospectus when acting as underwriters and with respect to their unsold allotments or subscriptions.

Part II

INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 13.    Other Expenses of Issuance and Distribution

        The following table sets forth an itemized statement of the amounts of all expenses (excluding underwriting discounts and commissions) payable by us in connection with the registration of the common stock offered hereby. With the exception of the SEC registration fee, FINRA filing fee and NYSE listing fee), the amounts set forth below are estimates.

SEC registration fee	$	49,535
FINRA filing fee		54,974
NYSE listing fee		250,000
Accounting fees and expenses		500,000
Legal fees and expenses		2,000,000
Printing and engraving expenses		400,000
Transfer agent and registrar fees		5,000
Miscellaneous		1,740,491
Total	$	5,000,000

ITEM 14.    Indemnification of Directors and Officers

        Section 145 of the Delaware General Corporation Law permits a Delaware corporation to indemnify its officers, directors and other corporate agents to the extent and under the circumstances set forth therein. Our amended and restated certificate of incorporation and bylaws provide that we will indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding whether civil, criminal, administrative or investigative, by reason of the fact that he is or was our director or officer, or is or was serving at our request as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, in accordance with provisions corresponding to Section 145 of the Delaware General Corporation Law. These indemnification provisions may be sufficiently broad to permit indemnification of the registrant's executive officers and directors for liabilities, including reimbursement of expenses incurred, arising under the Securities Act.

        Pursuant to Section 102(b)(7) of the Delaware General Corporation Law, our amended and restated certificate of incorporation eliminates the personal liability of a director to us or our stockholders for monetary damages for a breach of fiduciary duty as a director, except for liabilities arising:

•

from any breach of the director's duty of loyalty to us or our stockholders;

•

from acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law;

•

under Section 174 of the Delaware General Corporation Law; and

•

from any transaction from which the director derived an improper personal benefit.

        The above discussion of Section 145 of the Delaware General Corporation Law and of our amended and restated certificate of incorporation and bylaws is not intended to be exhaustive and is respectively qualified in its entirety by Section 145 of the Delaware General Corporation Law, our amended and restated certificate of incorporation and bylaws.

        As permitted by Section 145 of the Delaware General Corporation Law, we will carry primary and excess insurance policies insuring our directors and officers against certain liabilities they may incur in

II-1

their capacity as directors and officers. Under the policies, the insurer, on our behalf, may also pay amounts for which we granted indemnification to our directors and officers.

        In addition, the underwriting agreement to be filed as Exhibit 1.1 to this Registration Statement provides that the underwriters will indemnify us and our executive officers and directors for certain liabilities related to this offering, including liabilities arising under the Securities Act.

ITEM 15.    Recent Sales of Unregistered Securities

        In connection with our incorporation on April 1, 2013 under the laws of the State of Delaware, we issued 1,000 shares of our common stock to Athlon Holdings GP LLC for an aggregate purchase price of $10.00. These securities were offered and sold by us in reliance upon the exemption from the registration requirements provided by Section 4(2) of the Securities Act.

        On April 26, 2013, in connection with our reorganization transactions, certain holders of interests in Athlon Holdings LP exchanged their Class A limited partner interests and Class B interests of Athlon Holdings for an aggregate of 960,907 shares of our common stock. These securities were issued by us in reliance upon the exemption from the registration requirements provided by Section 4(2) of the Securities Act.

ITEM 16.    Exhibits and Financial Statement Schedules

(a)

Exhibits

Exhibit Number		Description
	1.1	Form of Underwriting Agreement.
	3.1*	Form of Amended and Restated Certificate of Incorporation of Athlon Energy Inc.
	3.2*	Form of Amended and Restated Bylaws of Athlon Energy Inc.
	4.1*	Indenture between Wells Fargo Bank, N.A. and Athlon Holdings LP dated April 17, 2013 relating to the 73/8% Senior Notes due 2021 (including form of Note) (previously filed as exhibit 4.2 to this registration statement on June 5, 2013).
	4.2*	Registration Rights Agreement among Athlon Holdings LP, Athlon Finance Corp. and Merrill Lynch, Pierce, Fenner & Smith Incorporated dated April 17, 2013 relating to the 73/8% Senior Notes due 2021 (previously filed as exhibit 4.3 to this registration statement on June 5, 2013).
	5.1	Opinion of Latham & Watkins LLP as to the legality of the securities being registered.
	10.1*	Amended and Restated Credit Agreement, dated as of March 19, 2013, among Athlon Holdings LP, Bank of America, N.A., as Administrative Agent and L/C Issuer, and the lenders party thereto.
	10.2*	Borrowing Base Redetermination and First Amendment to Amended and Restated Guarantee Agreement, dated as of May 31, 2013 by and among Athlon Holdings LP, Bank of America, N.A., as Administrative Agent and L/C Issuer, and the lenders party thereto.
	10.3*+	Form of Employment Agreement between Athlon Holdings LP and Robert C. Reeves.
	10.4*+	Form of Employment Agreement between Athlon Holdings LP and Officers other than Robert C. Reeves.
	10.5*+	Form of Athlon Energy Inc. 2013 Incentive Award Plan.
	10.6*+	Form of Director and Officer Indemnification Agreement between Athlon Energy Inc. and each of the officers and directors thereof (previously filed as exhibit 10.12 to Amendment No. 1 to this registration statement on June 27, 2013).
	10.7*	Form of Tax Receivable Agreement by and among Athlon Energy Inc., Athlon Holdings LP and each of the Partners named therein (previously filed as exhibit 10.13 to Amendment No. 1 to this registration statement on June 27, 2013).

II-2

Exhibit Number		Description
	10.8*	Form of Exchange Agreement by and among Athlon Energy Inc. and each of the Partners named therein (previously filed as exhibit 10.14 to Amendment No. 1 to this registration statement on June 27, 2013).
	10.9*	Form of Stockholders Agreement by and among Athlon Energy Inc. and those stockholders named therein.
	10.10*	Form of Advisory Services and Transaction Fee Termination Agreement by and among Athlon Holdings LP, Apollo Management VII, L.P. and Apollo Global Securities, LLC.
	10.11*	Form of Amended and Restated Agreement of Limited Partnership of Athlon Holdings LP.
	21.1*	Subsidiaries of Athlon Energy Inc.
	23.1	Consent of Ernst & Young LLP.
	23.2	Consent of UHY LLP.
	23.3	Consent of Cawley, Gillespie & Associates, Inc.
	23.4	Consent of Latham & Watkins LLP (included in Exhibit 5.1).
	23.5*	Consent of Director Nominee.
	24.1*	Power of Attorney.
	99.1*	Report of Cawley, Gillespie & Associates, Inc. for Athlon Energy Operating LLC's proved reserves at December 31, 2011 dated as of February 20, 2012.
	99.2*	Report of Cawley, Gillespie & Associates, Inc. for Athlon FE Operating LLC's proved reserves at December 31, 2011 dated as of February 20, 2012.
	99.3*	Report of Cawley, Gillespie & Associates, Inc. for Athlon Holdings LP's proved reserves at December 31, 2012 dated as of February 15, 2013.

^*

Previously filed.

⁺

Management contract or compensatory plan, contract or arrangement.

ITEM 17.    Undertakings

        The undersigned registrant hereby undertakes to provide to the underwriters at the closing specified in the underwriting agreement certificates in such denominations and registered in such names as required by the underwriters to permit prompt delivery to each purchaser.

        Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrant pursuant to the foregoing provisions, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act of 1933 and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act of 1933 and will be governed by the final adjudication of such issue.

        The undersigned registrant hereby undertakes that:

(1)

For purposes of determining any liability under the Securities Act of 1933, the information omitted from the form of prospectus filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act of 1933 shall be deemed to be part of this registration statement as of the time it was declared effective.



(2)

For the purpose of determining any liability under the Securities Act of 1933, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

II-3

SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of Fort Worth, State of Texas, on July 22, 2013.

Athlon Energy Inc.
By:	/s/ ROBERT C. REEVES Robert C. Reeves President, Chief Executive Officer and Director

        Pursuant to the requirements of the Securities Act of 1933, as amended, this registration statement has been signed below by the following persons in the capacities and the dates indicated.

Signature		Title	Date
	/s/ ROBERT C. REEVES Robert C. Reeves	President, Chief Executive Officer and Director (Principal Executive Officer)	July 22, 2013
	* William B. D. Butler	Vice President and Chief Financial Officer (Principal Financial Officer)	July 22, 2013
	* John C. Souders	Vice President and Controller (Principal Accounting Officer)	July 22, 2013
	* Gregory A. Beard	Director	July 22, 2013
	* Sam Oh	Director	July 22, 2013
	* Rakesh Wilson	Director	July 22, 2013
*By:	/s/ ROBERT C. REEVES Robert C. Reeves Attorney-in-fact

II-4

INDEX TO EXHIBITS

Exhibit Number		Description
	1.1	Form of Underwriting Agreement.
	3.1*	Form of Amended and Restated Certificate of Incorporation of Athlon Energy Inc.
	3.2*	Form of Amended and Restated Bylaws of Athlon Energy Inc.
	4.1*	Indenture between Wells Fargo Bank, N.A. and Athlon Holdings LP dated April 17, 2013 relating to the 73/8% Senior Notes due 2021 (including form of Note) (previously filed as exhibit 4.2 to this registration statement on June 5, 2013).
	4.2*	Registration Rights Agreement among Athlon Holdings LP, Athlon Finance Corp. and Merrill Lynch, Pierce, Fenner & Smith Incorporated dated April 17, 2013 relating to the 73/8% Senior Notes due 2021 (previously filed as exhibit 4.3 to this registration statement on June 5, 2013).
	5.1	Opinion of Latham & Watkins LLP as to the legality of the securities being registered.
	10.1*	Amended and Restated Credit Agreement, dated as of March 19, 2013, among Athlon Holdings LP, Bank of America, N.A., as Administrative Agent and L/C Issuer, and the lenders party thereto.
	10.2*	Borrowing Base Redetermination and First Amendment to Amended and Restated Guarantee Agreement, dated as of May 31, 2013 by and among Athlon Holdings LP, Bank of America, N.A., as Administrative Agent and L/C Issuer, and the lenders party thereto.
	10.3*+	Form of Employment Agreement between Athlon Holdings LP and Robert C. Reeves.
	10.4*+	Form of Employment Agreement between Athlon Holdings LP and Officers other than Robert C. Reeves.
	10.5*+	Form of Athlon Energy Inc. 2013 Incentive Award Plan.
	10.6*+	Form of Director and Officer Indemnification Agreement between Athlon Energy Inc. and each of the officers and directors thereof (previously filed as exhibit 10.12 to Amendment No. 1 to this registration statement on June 27, 2013).
	10.7*	Form of Tax Receivable Agreement by and among Athlon Energy Inc., Athlon Holdings LP and each of the Partners named therein (previously filed as exhibit 10.13 to Amendment No. 1 to this registration statement on June 27, 2013).
	10.8*	Form of Exchange Agreement by and among Athlon Energy Inc. and each of the Partners named therein (previously filed as exhibit 10.14 to Amendment No. 1 to this registration statement on June 27, 2013).
	10.9*	Form of Stockholders Agreement by and among Athlon Energy Inc. and those stockholders named therein.
	10.10*	Form of Advisory Services and Transaction Fee Termination Agreement by and among Athlon Holdings LP, Apollo Management VII, L.P. and Apollo Global Securities, LLC.
	10.11*	Form of Amended and Restated Agreement of Limited Partnership of Athlon Holdings LP.
	21.1*	Subsidiaries of Athlon Energy Inc.
	23.1	Consent of Ernst & Young LLP.
	23.2	Consent of UHY LLP.
	23.3	Consent of Cawley, Gillespie & Associates, Inc.
	23.4	Consent of Latham & Watkins LLP (included in Exhibit 5.1).
	23.5*	Consent of Director Nominee.
	24.1*	Power of Attorney.
	99.1*	Report of Cawley, Gillespie & Associates, Inc. for Athlon Energy Operating LLC's proved reserves at December 31, 2011 dated as of February 20, 2012.
	99.2*	Report of Cawley, Gillespie & Associates, Inc. for Athlon FE Operating LLC's proved reserves at December 31, 2011 dated as of February 20, 2012.
	99.3*	Report of Cawley, Gillespie & Associates, Inc. for Athlon Holdings LP's proved reserves at December 31, 2012 dated as of February 15, 2013.

^*

Previously filed.

⁺

Management contract or compensatory plan, contract or arrangement.

II-5

EX-1.1

Exhibit 1.1

Athlon Energy Inc.

[       ] Shares
Common Stock
($0.01 par value)

Underwriting Agreement

New York, New York
July [    ], 2013

Citigroup Global Markets Inc.
As Representative of the several Underwriters,
388 Greenwich Street
New York, New York 10013

Ladies and Gentlemen:

Athlon Energy Inc., a corporation organized under the laws of Delaware (the “Company”), proposes to sell to the several underwriters named in Schedule I hereto (the “Underwriters”), for whom you (the “Representative”) are acting as representative, [       ] shares of common stock, $0.01 par value (“Common Stock”) of the Company (said shares to be issued and sold by the Company being hereinafter called the “Underwritten Securities”).  The persons named in Schedule II hereto (the “Selling Stockholders”) also propose to grant to the Underwriters an option to purchase up to [       ] additional shares of Common Stock to cover over allotments, if any (the “Option Securities”; the Option Securities, together with the Underwritten Securities, being hereinafter called the “Securities”).  To the extent there are no additional Underwriters listed on Schedule I other than you, the term “Representatives” as used herein shall mean you, as Underwriters, and the terms “Representatives” and “Underwriters” shall mean either the singular or plural as the context requires.  In addition, to the extent that there is not more than one Selling Stockholder named in Schedule II, the term “Selling Stockholder” shall mean either the singular or plural.  The use of the neuter in this Agreement shall include the feminine and masculine wherever appropriate.  Certain terms used herein are defined in Section 20 hereof.

It is understood and agreed by all parties hereto that the Company was recently incorporated to become a holding company for Athlon Holdings LP (“Holdings”), as described more particularly in the Preliminary Prospectus and the Prospectus.

Prior to the date hereof, funds affiliated with Apollo Global Management, LLC exchanged their Class A limited partner interests in Holdings and holders of Class B limited partner interests in Holdings exchanged their Class B limited partners interests for Common Stock (the “Reorganization”). The “Documents” shall mean (i) the Contribution and Exchange Agreement, dated as of April 26, 2013, by and among the Class B limited partners of Holdings and the Company, (ii) the Contribution and Exchange Agreement,

dated as of April 26, 2013, by and among Apollo Athlon Holdings, L.P., AP Overseas VII (Athlon FC) Holdings, L.P., AIF VII (Athlon Conduit), L.P., AIF VII (Athlon Conduit II), L.P., AIF VII (Athlon Conduit III), L.P., the Company and Apollo Management VII, L.P., (iii) the Tax Receivable Agreement, to be entered into on the Closing Date, by and among the Company, Holdings and each of the Partners (as described therein), (iv) the Exchange Agreement, to be entered into on the Closing Date, by and among the Company and the Partners (as defined therein)[, and (z) the Stockholders Agreement, to be entered into on the Closing Date, by and among the Company and each of the stockholders of the Company listed on Schedule A thereto].  The Company and all of its subsidiaries are referred to collectively herein as the “Company Parties” and, individually, as a “Company Party.”

1.Representations and Warranties.

(i)The Company represents and warrants to, and agrees with, each Underwriter as set forth below in this Section 1.

(a)Registration Statement.  The Company has prepared and filed with the Commission a registration statement (file number 333-189109) on Form S-1, including a related preliminary prospectus, for registration under the Act of the offering and sale of the Securities.  Such Registration Statement, including any amendments thereto filed prior to the Execution Time, has become effective.  The Company may have filed one or more amendments thereto, including a related preliminary prospectus, each of which has previously been furnished to you.  The Company will file with the Commission a final prospectus in accordance with Rule 424(b).  As filed, such final prospectus shall contain all information required by the Act and the rules thereunder and, except to the extent the Representatives shall agree in writing to a modification, shall be in all substantive respects in the form furnished to you prior to the Execution Time or, to the extent not completed at the Execution Time, shall contain only such specific additional information and other changes (beyond that contained in the latest Preliminary Prospectus) as the Company has advised you, prior to the Execution Time, will be included or made therein.

(b)Form of Documents; No Material Misstatements or Omission in the Registration Statement and the Prospectus.  On the Effective Date, the Registration Statement did, and when the Prospectus is first filed in accordance with Rule 424(b) and on the Closing Date (as defined herein) and on any date on which Option Securities are purchased, if such date is not the Closing Date (a “settlement date”), the Prospectus (and any supplement thereto) will, comply in all material respects with the applicable requirements of the Act and the rules thereunder; on the Effective Date and at the Execution Time, the Registration Statement did not and will not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the date of any filing pursuant to Rule 424(b) and on the Closing Date and any settlement date, the Prospectus (together with any supplement thereto) will not include any untrue statement of a

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material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; provided, however, that the Company makes no representations or warranties as to the information contained in or omitted from the Registration Statement, or the Prospectus (or any supplement thereto) in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriter through the Representatives specifically for inclusion in the Registration Statement or the Prospectus (or any supplement thereto), it being understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 8 hereof.

(c)No Material Misstatements or Omission in the Disclosure Package.  (i) The Disclosure Package and the price to the public, the number of Underwritten Securities and the number of Option Securities to be included on the cover page of the Prospectus, when taken together as a whole, (ii) each electronic road show, when taken together as a whole with the Disclosure Package and the price to the public, the number of Underwritten Securities and the number of Option Securities to be included on the cover page of the Prospectus and (iii) any individual Written Testing-the-Waters Communication, when taken together as a whole with the Disclosure Package and the price to the public, the number of Underwritten Securities and the number of Option Securities to be included on the cover page of the Prospectus, does not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriter consists of the information described as such in Section 8 hereof.

(d)Ineligible Issuer.  (i) At the time of filing the Registration Statement and (ii) as of the Execution Time (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an “ineligible issuer” (as defined in Rule 405), without taking account of any determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an ineligible issuer.

(e)Emerging Growth Company.  From the time of initial confidential submission of the Company’s draft Registration Statement on Form S-1 to the Commission (or, if earlier, the first date on which the Company engaged directly or through any Person authorized to act on its behalf in any Testing-the-Waters Communication) through the Execution Time, the Company has been and is an “emerging growth company,” as defined in Section 2(a) of the Act (an “Emerging Growth Company”).

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(f)No Testing-the-Waters Communications.  The Company (i) has not alone engaged in any Testing-the-Waters Communication and (ii) has not authorized anyone other than the Representatives to engage in Testing-the-Waters Communications.  The Company reconfirms that the Representatives have been authorized to act on its behalf in undertaking Testing-the-Waters Communications.  The Company has not distributed any Written Testing-the-Waters Communications.

(g)Free Writing Prospectus.  Each Issuer Free Writing Prospectus does not include any information that conflicts with the information contained in the Registration Statement.  The foregoing sentence does not apply to statements in or omissions from any Issuer Free Writing Prospectus based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriter consists of the information described as such in Section 8 hereof.

(h)The Underwriting Agreement.  This Agreement has been duly authorized, executed and delivered by the Company.

(i)Incorporation and Good Standing of the Company Parties.  Each of the Company Parties has been duly incorporated or formed, as applicable, and is validly existing as a corporation, limited partnership or limited liability company, as applicable, in good standing under the laws of the jurisdiction of its incorporation or formation, as applicable, and has corporate, partnership or limited liability company, as applicable, power and authority to own, lease and operate its properties and to conduct its business as described in the Registration Statement, Disclosure Package and Prospectus and to enter into and perform its obligations under this Agreement and each of the Documents to which it is a party.  Each of the Company Parties is duly qualified as a foreign corporation, limited partnership or limited liability company, as applicable, to transact business and is in good standing or equivalent status in each jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except for such jurisdictions where the failure to so qualify or to be in good standing would not, individually or in the aggregate, result in a Material Adverse Change (as defined herein).  All of the issued and outstanding capital stock or other ownership interest of each subsidiary of the Company has been duly authorized and validly issued, is fully paid and nonassessable and is owned by the Company, directly or through subsidiaries, free and clear of any security interest, mortgage, pledge, lien, encumbrance or claim, except as disclosed in the Registration Statement, Disclosure Package and Prospectus.  The subsidiaries listed on Annex A attached hereto are the only significant subsidiaries of the Company as defined by Rule 1-02 of Regulation S-X.

(j)Capitalization.  The Company’s authorized equity capitalization is as set forth in the Registration Statement, Disclosure Package and Prospectus and

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the capital stock of the Company conforms to the description thereof contained in the Registration Statement, Disclosure Package and Prospectus.  The outstanding shares of Common Stock of the Company (including the Option Securities being sold hereunder by the Selling Stockholders) have been duly and validly authorized and issued and are fully paid and nonassessable and the Securities being sold hereunder by the Company have been duly and validly authorized, and, when issued and delivered to and paid for by the Underwriters pursuant to this Agreement, will be fully paid and nonassessable.  The Securities being sold by the Company and the Selling Stockholders have been approved to be listed for trading on the New York Stock Exchange, subject to official notice of issuance and evidence of satisfactory distribution.  The holders of outstanding shares of capital stock of the Company are not entitled to preemptive or other rights to subscribe for the Securities and, except as set forth in the Registration Statement, Disclosure Package and Prospectus, no options, warrants or other rights to purchase, agreements or other obligations to issue, or rights to convert any obligations into or exchange any securities for, shares of capital stock of or ownership interests in the Company are outstanding.

(k)Accuracy of Statements in the Registration Statement, Disclosure Package and Prospectus.  There is no franchise, contract or other document of a character required to be described in the Registration Statement, Disclosure Package and Prospectus, or to be filed as an exhibit thereto, which is not described or filed as required (and the Preliminary Prospectus contains in all material respects the same description of the foregoing matters contained in the Prospectus); and the statements in the Preliminary Prospectus and the Prospectus under the caption “Description of Capital Stock,” insofar as they purport to constitute a summary of the terms of the Common Stock, and under the captions “Corporate Reorganization,” “Certain Relationships and Related Party Transactions” and “Material U.S. Federal Income Tax Consequences to Non-US Holders” insofar as they purport to describe the provisions of the laws and documents referred to therein to which the Company is a party, are accurate in all material respects.

(l)Company Parties Not an “Investment Company”.  No Company Party is, or after receipt of payment for the Securities and application of the proceeds as described under “Use of Proceeds” in the Registration Statement, Disclosure Package and Prospectus will be, required to register as an “investment company” within the meaning of the Investment Company Act of 1940, as amended.

(m)Non-Contravention of Existing Instruments; No Further Authorizations or Approvals Required.  None of the Company Parties (i) is in violation of its charter, certificate of formation, bylaws, limited partnership agreement or limited liability company agreement (or other applicable organizational document) (collectively, the “Organizational Documents”), or (ii) is (or, with the giving of notice or lapse of time, would be) in default (“Default”) under any indenture, mortgage, loan or credit agreement, note, contract, franchise,

5

lease or other instrument to which a Company Party is a party or by which it or any of them may be bound (including, without limitation, the Existing Indebtedness), or to which any of the property or assets of the Partnership Parties is subject (each, an “Existing Instrument”), except with respect to clause (ii), for such Defaults as would not, individually or in the aggregate, result in a Material Adverse Change.  The execution, delivery and performance of this Agreement and the Documents by the Company Parties party thereto, and the issuance and delivery of the Underwritten Securities, and consummation by the Company Parties of the Reorganization and the transactions contemplated hereby and thereby and by the Registration Statement, Disclosure Package and Prospectus (i) have been duly authorized by all necessary Company Party action (corporate or otherwise) and will not result in any violation of the Organizational Documents of the Company Parties, (ii) will not conflict with or constitute a breach of or Default under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company Parties pursuant to, or require the consent of any other party to, any Existing Instrument, except for such conflicts, breaches, Defaults, liens, charges or encumbrances as would not, individually or in the aggregate, result in a Material Adverse Change and (iii) will not result in any violation of any law, administrative regulation or administrative or court decree applicable to the Company Parties.  No consent, approval, authorization or other order of, or registration or filing with, any court or other governmental or regulatory authority or agency is required for the execution, delivery and performance of this Agreement or the Documents by the Company Parties party thereto, or the issuance and delivery of the Underwritten Securities, or consummation of the transactions contemplated hereby and thereby and by the Registration Statement, Disclosure Package and Prospectus by the Company Parties, except such as have been obtained under the Act and such as may be required by the securities laws of the several states of the United States in connection with the purchase and distribution of the Securities by the Underwriters in the manner contemplated herein and in the Disclosure Package and the Prospectus or which, if not obtained, would not, individually or in the aggregate, cause a Material Adverse Change.

(n)Preparation of the Financial Statements.  The financial statements, together with the related schedules and notes, included in the Registration Statement, Disclosure Package and Prospectus present fairly in all material respects the consolidated financial position of the entities to which they relate as of and at the dates indicated and the results of their operations and cash flows for the periods specified.  Such financial statements have been prepared in conformity with generally accepted accounting principles as applied in the United States (“GAAP”) applied on a consistent basis throughout the periods involved, except as may be expressly stated in the related notes thereto.  The summary historical financial and operating information set forth in the Registration Statement, Disclosure Package and Prospectus under the captions “Summary Consolidated Financial, Reserve and Operating Data” and “Selected Historical Consolidated Financial Data” and elsewhere in the Registration Statement, Disclosure Package and Prospectus presents fairly in all material respects the

6

information set forth therein on a basis consistent with that of the audited financial statements contained in the Registration Statement, Disclosure Package and Prospectus. The statistical and market-related data and forward-looking statements included in the Registration Statement, Disclosure Package and Prospectus are based on or derived from sources that the Company Parties believe to be reliable and accurate in all material respects and represent their good faith estimates that are made on the basis of data derived from such sources.

(o)Pro Forma Financial Statements.  The pro forma financial statements included in the Registration Statement, Disclosure Package and Prospectus include assumptions that provide a reasonable basis for presenting the significant effects directly attributable to the transactions and events described therein, the related pro forma adjustments give appropriate effect to those assumptions, and the pro forma adjustments reflect the proper application of those adjustments to the historical financial statement amounts in the pro forma financial statements included in the Registration Statement, Disclosure Package and Prospectus.  The pro forma financial statements included in the Registration Statement, Disclosure Package and Prospectus comply as to form in all material respects with the applicable accounting requirements of Regulation S-X under the Act and the pro forma adjustments have been properly applied to the historical amounts in the compilation of those statements.

(p)Sarbanes-Oxley Act.  There is and has been no failure on the part of the Company Parties or any of the Company Parties’ directors or officers, in their capacities as such, to comply with any provision of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated in connection therewith, including Section 402 relating to loans and Sections 302 and 906 relating to certifications.

(q)No Material Actions or Proceedings.  There are no legal or governmental actions, suits or proceedings pending or, to the best of the Company Parties’ knowledge, threatened (i) against or affecting the Company Parties or (ii) which has as the subject thereof any property owned or leased by the Company Parties and any such action, suit or proceeding, if determined adversely to the Company Parties, would result in a Material Adverse Change or adversely affect the consummation of the transactions contemplated by this Agreement.  No material labor dispute with the employees of the Company Parties exists or, to the Company Parties’ knowledge, is threatened or imminent.

(r)No Material Adverse Change.  Except as otherwise disclosed in the Registration Statement, Disclosure Package and Prospectus (exclusive of any amendment or supplement thereto), subsequent to the respective dates as of which information is given in the Registration Statement, Disclosure Package and Prospectus (exclusive of any amendment or supplement thereto):  (i) there has been no material adverse change, or any development that could reasonably be expected to result in a material adverse change, in the condition, financial or otherwise, or in the earnings, business or operations, whether or not arising from

7

transactions in the ordinary course of business, of the Company Parties, considered as one entity (any such change is called a “Material Adverse Change”); (ii) the Company Parties, considered as one entity, have not incurred any material liability or obligation, indirect, direct or contingent, not in the ordinary course of business nor entered into any material transaction or agreement not in the ordinary course of business; and (iii) there has been no dividend or distribution of any kind declared, paid or made by the Company or, except for dividends paid to the Company or to other subsidiaries, any of its subsidiaries on any class of equity or repurchase or redemption by the Company or any of its subsidiaries of any class of equity.

(s)Title to Properties.  Except as disclosed in the Registration Statement, Disclosure Package and Prospectus, the Company Parties have (i) defensible title to all of their oil and gas properties (including oil and gas wells, producing leasehold interests and appurtenant personal property), title investigations having been carried out by the Company Parties consistent with the reasonable practice in the oil and gas industry in the areas in which the Company Parties operate and (ii) good and marketable title to all other real properties and good title to all personal properties and assets owned by them, in the case of each of (i) and (ii) free from liens, encumbrances and defects (other than liens disclosed in the Registration Statement, Disclosure Package and Prospectus) that would individually or in the aggregate result in a Material Adverse Change; and except as disclosed in the Registration Statement, Disclosure Package and Prospectus, the Company Parties hold any leased real or personal property under valid and enforceable leases with no exceptions that would interfere with the use made or to be made thereof by them, except as would not individually or in the aggregate result in a Material Adverse Change.

(t)Independent Accountants.  Ernst & Young LLP, which has expressed its opinion with respect to the financial statements (which term as used in this Agreement includes the related notes thereto) and supporting schedules included in the Registration Statement, Disclosure Package and Prospectus is an independent registered public accounting firm within the meaning of the Securities Act, the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and the rules of the Public Company Accounting Oversight Board, and any non-audit services provided by Ernst & Young LLP to the Company Parties have been approved by the Board of Directors of the Company.  UHY LLP, which has expressed its opinion with respect to the financial statements and supporting schedules included in the Registration Statement, Disclosure Package and Prospectus with respect to Element Petroleum LP, is an independent registered public accounting firm within the meaning of the Securities Act, the Exchange Act and the rules of the Public Company Accounting Oversight Board, and any non-audit services provided by UHY LLP to the Company Parties have been approved by the Board of Directors of the Company.

(u)Independent Petroleum Engineers.  Cawley, Gillespie & Associates, Inc. (“CGA”), whose reserve evaluations are referenced or appear, as

8

the case may be, in the Registration Statement, Disclosure Package and Prospectus were, as of December 31, 2011 and December 31, 2012, and are, as of the date hereof, independent engineers with respect to the Company Parties; and the historical information underlying the estimates of the reserves of the Company supplied by the Company Parties to CGA for the purposes of preparing the reserve reports of the Company referenced in the Registration Statement, Disclosure Package and Prospectus (the “Reserve Reports”), including, without limitation, production volumes, sales prices for production, contractual pricing provisions under oil or gas sales or marketing contracts or under hedging arrangements, costs of operations and development, and working interest and net revenue information relating to the Company’s ownership interests in properties, was true and correct on the date that each such Reserve Report was prepared in all material respects in accordance with Commission rules and customary industry practices.  Other than normal production of the reserves, product price fluctuations, and fluctuations of demand for such products, and except as disclosed in the Registration Statement, Disclosure Package and Prospectus, the Company is not aware of any facts or circumstances that would result in a Material Adverse Change in the reserves in the aggregate, or the aggregate present value of the future net cash flows therefrom as described in the Registration Statement, Disclosure Package and Prospectus and as reflected in the Reserve Reports.

(v)Tax Law Compliance.  The Company and its consolidated subsidiaries have filed all necessary federal, state, local and foreign income and franchise tax returns and have paid all taxes required to be paid by any of them and, if due and payable, any related or similar assessment, fine or penalty levied against any of them, except for any taxes, assessments, fines or penalties as may be being contested in good faith and by appropriate proceedings or as would not, individually or in the aggregate, cause a Material Adverse Change.  The Company has made adequate charges, accruals and reserves in accordance with GAAP in the applicable financial statements referred to in Section 1(n) hereof in respect of all federal, state and foreign income and franchise taxes for all periods as to which the tax liability of the Company or any of its consolidated subsidiaries has not been finally determined.

(w)Transfer Taxes.  To the Company’s knowledge, there are no transfer taxes or other similar fees or charges under Federal law or the laws of any state, or any political subdivision thereof, required to be paid in connection with the execution and delivery of this Agreement or the issuance by the Company or sale by the Company of the Underwritten Securities.

(x)Compliance with Labor Laws.  Except as would not, individually or in the aggregate, result in a Material Adverse Change, (i) there is (A) no unfair labor practice complaint pending or, to the best of the Company Parties’ knowledge, threatened against the Company Parties before the National Labor Relations Board, and no grievance or arbitration proceeding arising out of or under collective bargaining agreements pending, or to the best of the Company

9

Parties’ knowledge, threatened, against the Company Parties, (B) no strike, labor dispute, slowdown or stoppage pending or, to the best of the Company Parties’ knowledge, threatened against the Company Parties and (C) no union representation question existing with respect to the employees of the Company Parties and, to the best of the Company Parties’ knowledge, no union organizing activities taking place and (ii) there has been no violation of any federal, state or local law relating to discrimination in hiring, promotion or pay of employees or of any applicable wage or hour laws.

(y)Insurance.  Each of the Company Parties is insured by recognized, financially sound institutions with policies in such amounts and with such deductibles and covering such risks as are generally deemed adequate and customary for their businesses.  The Company Parties have no reason to believe that it or any subsidiary will not be able (i) to renew its existing insurance coverage as and when such policies expire or (ii) to obtain comparable coverage from similar institutions as may be necessary or appropriate to conduct its business as now conducted and at a cost that would not result in a Material Adverse Change.  None of the Company Parties has been denied any insurance coverage which it has sought or for which it has applied.

(z)All Necessary Permits, etc.  The Company Parties possess such valid and current certificates, authorizations or permits issued by the appropriate state, federal or foreign regulatory agencies or bodies necessary to own, lease and operate its properties and to conduct their respective businesses in all material respects, and none of the Company Parties has received any notice of proceedings relating to the revocation or modification of, or non-compliance with, any such certificate, authorization or permit which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would result in a Material Adverse Change.

(aa)Company’s Accounting System.  The Company Parties (considered as one entity) maintain a system of accounting controls that is sufficient to provide reasonable assurances that:  (i) transactions are executed in accordance with management’s general or specific authorization; (ii) transactions are recorded as necessary to permit preparation of the Company’s financial statements in conformity with GAAP and to maintain accountability for its assets; (iii) access to the assets of the Company and its subsidiaries is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

(bb)Disclosure Controls and Procedures.  The Company Parties (considered as one entity) maintain “disclosure controls and procedures” (as such term is defined in Rule 13a-15(e) under the Exchange Act); such disclosure controls and procedures are effective.

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(cc)No Price Stabilization or Manipulation.  None of the Company Parties has taken or will take, directly or indirectly, any action designed to or that might be reasonably expected to cause or result in stabilization or manipulation of the price of any security of the Company Parties to facilitate the sale or resale of the Securities.

(dd)Environmental Laws.  Except as disclosed in the Registration Statement, Disclosure Package and Prospectus, to the best knowledge of the Company Parties, none of the Company Parties is in violation of any statute, rule, regulation, decision or order of any governmental agency or body or any court, domestic or foreign, relating to the use, disposal or release of hazardous or toxic substances or relating to the protection or restoration of the environment or human exposure to hazardous or toxic substances (collectively, “Environmental Laws”), owns or operates any real property contaminated with any substance that is subject to any Environmental Laws, is liable for any off-site disposal or contamination pursuant to any Environmental Laws, or is subject to any claim relating to any Environmental Laws, which violation, contamination, liability or claim would individually or in the aggregate result in a Material Adverse Change; and, except as disclosed in the Registration Statement, Disclosure Package and Prospectus, the Company Parties are not aware of any pending investigation which might lead to such a claim.

(ee)ERISA Compliance.  The Company Parties and any “employee benefit plan” (as defined under the Employee Retirement Income Security Act of 1974 (as amended, “ERISA,” which term, as used herein, includes the regulations and published interpretations thereunder) established or maintained by the Company Parties or their ERISA Affiliates (as defined below) are in compliance with the requirements of ERISA and, to the knowledge of the Company Parties, each “multiemployer plan” (as defined in Section 4001 of ERISA) to which the Company Parties or an ERISA Affiliate contributes (a “Multiemployer Plan”) is in compliance with the requirements of ERISA, except as would not, individually or in the aggregate, result in a Material Adverse Change.  “ERISA Affiliate” means, with respect to the Company Parties, any member of any group of organizations described in Section 414 of the Internal Revenue Code of 1986 (as amended, the “Code,” which term, as used herein, includes the regulations and published interpretations thereunder) of which a Company Parties is a member.  Except as would not, individually or in the aggregate, result in a Material Adverse Change, (i) no “reportable event” (as defined under ERISA) has occurred or is reasonably expected to occur with respect to any “employee benefit plan” established or maintained by the Company Parties or any of their ERISA Affiliates, (ii) no “single employer plan” (as defined in Section 4001 of ERISA) established or maintained by the Company Parties or any of their ERISA Affiliates, if such “employee benefit plan” were terminated, would have any “amount of unfunded benefit liabilities” (as defined under ERISA), (iii) neither the Company Parties nor any of their ERISA Affiliates has incurred or reasonably expects to incur any liability under (A) Title IV of ERISA with respect to termination of, or withdrawal from, any “employee benefit plan” or (B) Sections

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412, 4971, 4975 or 4980B of the Code, and (iv) each “employee benefit plan” established or maintained by the Company Parties or any of their ERISA Affiliates that is intended to be qualified under Section 401 of the Code is so qualified and nothing has occurred, whether by action or failure to act, which would cause the loss of such qualification.

(ff)No Unlawful Contributions or Other Payments.  Neither the Company Parties nor, to the knowledge of the Company Parties, any director, officer, agent, employee or affiliate of the Company Parties (excluding for purposes of this Section 1(ff) Apollo Global Management LLC, its subsidiary funds and their portfolio companies other than the Company (the “Apollo Entities”)) is aware of or has taken any action, directly or indirectly, that would result in a violation by such persons of the FCPA, including, without limitation, making use of the mails or any means or instrumentality of interstate commerce corruptly in furtherance of an offer, payment, promise to pay or authorization of the payment of any money, or other property, gift, promise to give, or authorization of the giving of anything of value to any “foreign official” (as such term is defined in the FCPA) or any foreign political party or official thereof or any candidate for foreign political office, in contravention of the FCPA and the Company Parties and, to the knowledge of the Company Parties, their affiliates (excluding for the purposes of this Section 1(ff) the Apollo Entities) have conducted their businesses in compliance with the FCPA and have instituted and maintain policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith.  “FCPA” means Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder.

(gg)No Conflict with Money Laundering Laws.  The operations of the Company Parties are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the money laundering statutes of all applicable jurisdictions, the rules and regulations thereunder and any related or similar rules, regulations or guidelines issued, administered or enforced by any governmental agency (collectively, the “Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company Parties with respect to the Money Laundering Laws is pending or, to the best knowledge of the Company Parties, threatened.

(hh)No Conflict with Sanctions Laws.  Neither the Company Parties nor, to the knowledge of the Company Parties, any director, officer, agent, employee or affiliate of the Company Parties (excluding for the purposes of this Section 1(hh) the Apollo Entities) is currently subject to any U.S. sanctions administered by the Office of Foreign Assets Control of the U.S. Treasury Department, the U.S. Department of Commerce, the U.S. Department of State (collectively, “Sanctions”), and the Company Parties are not located, organized or residents in a country or territory that is the subject of Sanctions.  The Company

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Parties will not, directly or indirectly, use the proceeds of the offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, joint venture partner or other person, (i) to fund any activities of or business with any person that, at the time of such funding, is the subject of Sanctions, or is in Burma/Myanmar, Cuba, Iran, Libya, North Korea, Sudan or in any other country or territory, that, at the time of such funding, is the subject of Sanctions, or (ii) in any other manner that will result in a violation by any person (including any person participating in the offering, whether as underwriter, advisor, investor or otherwise) of Sanctions.

(ii)Intellectual Property Rights.  The Company Parties own, possess or can acquire on reasonable terms, adequate trademarks, trade names and other rights to inventions, knowhow, patents, copyrights, confidential information and other intellectual property (collectively, “Intellectual Property Rights”) that, to their best knowledge after due inquiry, are necessary to conduct their business as described in the Registration Statement, Disclosure Package and Prospectus, or presently employed by them, and have not received any notice of infringement of or conflict with asserted rights of others with respect to any Intellectual Property Rights that, if determined adversely to the Company Parties, would individually or in the aggregate cause a Material Adverse Change.

(jj)Related Party Transactions.  Except as disclosed in the Registration Statement, Disclosure Package and Prospectus, no relationship, direct or indirect, exists between or among any of the Company Parties or their affiliates, on the one hand, and any director, officer, member, stockholder, customer or supplier of the Company Parties or their affiliates, on the other hand, which is required by the Securities Act to be disclosed in the Registration Statement, Disclosure Package and Prospectus.  There are no outstanding loans, advances (except advances for business expenses in the ordinary course of business) or guarantees of indebtedness by the Company Parties or their affiliates to or for the benefit of any of the officers or directors of the Company Parties or their affiliates or any of their respective family members.

(kk)FINRA Member Affiliations.  To the knowledge of the Company Parties, there are no affiliations or associations between any member of Financial Industry Regulatory Authority, Inc. (“FINRA”) and any of the Company Parties’ officers, directors or 5% or greater stockholders, except as described in the Disclosure Package, Prospectus and Registration Statement.

(ll)No Registration Rights.  Except with respect to the registration and sale of the Option Securities by the Selling Stockholders pursuant hereto or as disclosed in the Registration Statement, Disclosure Package or Prospectus, no holders of securities of the Company have rights to the registration of such securities under the Registration Statement.

(mm)No Restricted Payments.  No subsidiary is currently prohibited, directly or indirectly, from paying any dividends to the Company, from making

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any other distribution on such subsidiary’s capital stock, from repaying to the Company any loans or advances to such subsidiary from the Company or from transferring any of such subsidiary’s property or assets to the Company or any other subsidiary of the Company, except as described in or contemplated by the Registration Statement, Disclosure Package and Prospectus (exclusive of any supplement thereto).

Any certificate signed by any officer of the Company and delivered to the Representatives or counsel for the Underwriters in connection with the offering of the Securities shall be deemed a representation and warranty by the Company, as to matters covered thereby, to each Underwriter.

(ii)Each Selling Stockholder represents and warrants to, and agrees with, each Underwriter that:

(a)Title to Securities.  On the applicable Closing Date, such Selling Stockholder is the record and beneficial owner of the Securities to be sold by it hereunder free and clear of all liens, encumbrances, equities and claims, and has full power and authority to sell its interest in the Securities, and, assuming that each Underwriter acquires its interest in the Securities it has purchased from such Selling Stockholder without notice of any adverse claim (within the meaning of Section 8-105 of the New York Uniform Commercial Code (“UCC”)), each Underwriter that has purchased such Securities delivered on the Closing Date to The Depository Trust Company or other securities intermediary by making payment therefor as provided herein, and that has had such Securities credited to the securities account or accounts of such Underwriters maintained with The Depository Trust Company or such other securities intermediary will have acquired a security entitlement (within the meaning of Section 8-102(a)(17) of the UCC) to such Securities purchased by such Underwriter, and no action based on an adverse claim (within the meaning of Section 8-105 of the UCC) may be asserted against such Underwriter with respect to such Securities.

(b)No Price Stabilization or Manipulation.  Such Selling Stockholder has not taken, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(c)No Further Authorizations or Approvals Required.  No consent, approval, authorization or order of any court or governmental agency or body is required for the consummation by such Selling Stockholder (except as may be required as a result of the identity or status of the Underwriters) of the transactions contemplated herein, except (i) as may be required under states securities “Blue Sky” laws in connection with the transactions contemplated hereby, (ii) such as will have been obtained on or prior to the Closing Date or any settlement date and (iii) for such consents, approvals, authorizations or orders as would not adversely affect the Underwriters and as would not materially

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adversely affect such Selling Stockholder’s ability to perform its obligations hereunder or materially impair the validity or enforceability hereof.

(d)Non-Contravention of Existing Instruments.  The execution, delivery and performance of this Agreement and the consummation of the transactions herein contemplated by such Selling Stockholder will not result in a breach or violation of any of the terms and provisions of, or constitute a default under, or result in the imposition of any lien upon any property or assets of such Selling Stockholder pursuant to, (i) any statute, any rule, regulation or order of any governmental agency or body or any court having jurisdiction over such Selling Stockholder or any of its properties, (ii) any agreement or instrument to which such Selling Stockholder is a party or by which such Selling Stockholder is bound which is material to such Selling Stockholder or to which any of the properties of such Selling Stockholder is subject, or (iii) the Organizational Documents of such Selling Stockholder, except, in the case of clauses (i) and (ii) above, where such breach, violation or default would not, individually or in the aggregate, materially adversely affect such Selling Stockholder’s ability to perform its obligations hereunder or materially impair the validity or enforceability hereof.

(e)Selling Stockholders’ Intent.  The sale of the Securities by such Selling Stockholder pursuant hereto is not prompted by any material information concerning the Company or any of its subsidiaries which is not set forth in the Disclosure Package and the Prospectus.

(f)Other Representations.  In respect of any statements in or omissions from the Registration Statement, Disclosure Package and Prospectus or any amendment or supplement thereto used by the Company or any Underwriter, as the case may be, made in reliance upon and in conformity with information furnished in writing to the Company by any Selling Stockholder specifically for use in connection with the preparation thereof, such Selling Stockholder hereby makes the same representations and warranties to each Underwriter as the Company makes to such Underwriter under paragraphs (i)(b), (i)(c) and (i)(g) of this Section.

Any certificate signed by any officer of any Selling Stockholder and delivered to the Representatives or counsel for the Underwriters in connection with the offering of the Securities shall be deemed a representation and warranty by such Selling Stockholder, as to matters covered thereby, to each Underwriter.

2.Purchase and Sale.  (a)  Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to each Underwriter, and each Underwriter agrees, severally and not jointly, to purchase from the Company, at a purchase price of $[                ] per share, the amount of the Underwritten Securities set forth opposite such Underwriter’s name in Schedule I hereto.

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(b)Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Selling Stockholders named in Schedule II hereto hereby grant an option to the several Underwriters to purchase, severally and not jointly, up to [   ] Option Securities at the same purchase price per share as the Underwriters shall pay for the Underwritten Securities, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Underwritten Securities but not payable on the Option Securities.  Said option may be exercised only to cover over-allotments in the sale of the Underwritten Securities by the Underwriters.  Said option may be exercised in whole or in part at any time on or before the 30th day after the date of the Prospectus upon written or telegraphic notice by the Representatives to the Company and such Selling Stockholders setting forth the number of shares of the Option Securities as to which the several Underwriters are exercising the option and the settlement date.  The maximum number of Option Securities to be sold by the Selling Stockholders in the aggregate is [       ].  The maximum number of Option Securities which each Selling Stockholder agrees to sell is set forth in Schedule II hereto.  In the event that the Underwriters exercise less than their full option to purchase Option Securities, the number of Option Securities to be sold by the each Selling Stockholder listed on Schedule II shall be, as nearly as practicable, in the same proportion as the maximum number of Option Securities to be sold by each Selling Stockholder and the number of Option Securities to be sold.  The number of Option Securities to be purchased by each Underwriter shall be the same percentage of the total number of shares of the Option Securities to be purchased by the several Underwriters as such Underwriter is purchasing of the Underwritten Securities, subject to such adjustments as you in your absolute discretion shall make to eliminate any fractional shares.

3.Delivery and Payment.  Delivery of and payment for the Underwritten Securities and the Option Securities (if the option provided for in Section 2(b) hereof shall have been exercised on or before the third Business Day immediately preceding the Closing Date) shall be made at 10:00 AM, New York City time, on [              ], 2013, or at such time on such later date not more than three Business Days after the foregoing date as the Representatives shall designate, which date and time may be postponed by agreement among the Representatives, the Company and the Selling Stockholders or as provided in Section 9 hereof (such date and time of delivery and payment for the Securities being herein called the “Closing Date”).  Delivery of the Securities shall be made to the Representatives for the respective accounts of the several Underwriters against payment by the several Underwriters through the Representatives of the respective aggregate purchase prices of the Securities being sold by the Company and each of the Selling Stockholders to or upon the order of the Company and, to the extent the option to purchase the Option Securities is exercised, the Selling Stockholders by wire transfer payable in same-day funds to the accounts specified by the Company and the Selling Stockholders.  Delivery of the Underwritten Securities and the Option Securities shall be made through the facilities of The Depository Trust Company unless the Representatives shall otherwise instruct.

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Each Selling Stockholder will pay all applicable state transfer taxes, if any, involved in the transfer to the several Underwriters of the Securities to be purchased by them from such Selling Stockholder and the respective Underwriters will pay any additional stock transfer taxes involved in further transfers.

If the option provided for in Section 2(b) hereof is exercised after the third Business Day immediately preceding the Closing Date, the Selling Stockholders will deliver the Option Securities (at the expense of the Company) to the Representatives, at 388 Greenwich Street, New York, New York, on the date specified by the Representatives (which shall be within three Business Days after exercise of said option) for the respective accounts of the several Underwriters, against payment by the several Underwriters through the Representatives of the purchase price thereof to or upon the order of the Selling Stockholders by wire transfer payable in same-day funds to the accounts specified by the Selling Stockholders.  If settlement for the Option Securities occurs after the Closing Date, such Selling Stockholders will deliver to the Representatives on the settlement date for the Option Securities, and the obligation of the Underwriters to purchase the Option Securities shall be conditioned upon receipt of, supplemental opinions, certificates and letters confirming as of such date the opinions, certificates and letters delivered on the Closing Date pursuant to Section 6 hereof.

4.Offering by Underwriters.  It is understood that the several Underwriters propose to offer the Securities for sale to the public as set forth in the Prospectus.

5.Agreements.

(i)The Company agrees with the several Underwriters that:

(a)Prior to the termination of the offering of the Securities, the Company will not file any amendment of the Registration Statement or supplement to the Prospectus or any Rule 462(b) Registration Statement unless the Company has furnished you a copy for your review prior to filing and will not file any such proposed amendment or supplement to which you reasonably object. The Company will cause the Prospectus, properly completed, and any supplement thereto to be filed in a form approved by the Representatives with the Commission pursuant to the applicable paragraph of Rule 424(b) within the time period prescribed and will provide evidence satisfactory to the Representatives of such timely filing.  The Company will promptly advise the Representatives (i) when the Prospectus, and any supplement thereto, shall have been filed (if required) with the Commission pursuant to Rule 424(b) or when any Rule 462(b) Registration Statement shall have been filed with the Commission, (ii) when, prior to termination of the offering of the Securities, any amendment to the Registration Statement shall have been filed or become effective, (iii) of any request by the Commission or its staff for any amendment of the Registration Statement, or any Rule 462(b) Registration Statement, or for any supplement to the Prospectus or for any additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration

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Statement or of any notice objecting to its use or the institution or threatening of any proceeding for that purpose and (v) of the receipt by the Company of any notification with respect to the suspension of the qualification of the Securities for sale in any jurisdiction or the institution or threatening of any proceeding for such purpose.  The Company will use its reasonable best efforts to prevent the issuance of any such stop order or the occurrence of any such suspension or objection to the use of the Registration Statement and, upon such issuance, occurrence or notice of objection, to obtain as soon as possible the withdrawal of such stop order or relief from such occurrence or objection, including, if necessary, by filing an amendment to the Registration Statement or a new registration statement and using its reasonable best efforts to have such amendment or new registration statement declared effective as soon as practicable.

(b)If, at any time prior to the filing of the Prospectus pursuant to Rule 424(b), any event occurs as a result of which the Disclosure Package would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made or the circumstances then prevailing not misleading, the Company will (i) notify promptly the Representatives so that any use of the Disclosure Package may cease until it is amended or supplemented; (ii) amend or supplement the Disclosure Package to correct such statement or omission; and (iii) supply any amendment or supplement to you in such quantities as you may reasonably request.

(c)If, at any time when a prospectus relating to the Securities is required to be delivered under the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), any event occurs as a result of which the Prospectus as then supplemented would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made at such time not misleading, or if it shall be necessary to amend the Registration Statement or supplement the Prospectus to comply with the Act or the rules thereunder, the Company promptly will (i) notify the Representatives of any such event; (ii) prepare and file with the Commission, subject to the second sentence of paragraph (a) of this Section 5, an amendment or supplement which will correct such statement or omission or effect such compliance; and (iii) supply any supplemented Prospectus to you in such quantities as you may reasonably request.

(d)As soon as practicable, the Company will make generally available to its security holders and to the Representatives an earnings statement or statements of the Company and its subsidiaries which will satisfy the provisions of Section 11(a) of the Act and Rule 158.

(e)The Company will furnish to the Representatives and counsel for the Underwriters, without charge, signed copies of the Registration Statement (including exhibits thereto) and to each other Underwriter a copy of the Registration Statement (without exhibits thereto) and, so long as delivery of a

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prospectus by an Underwriter or dealer may be required by the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), as many copies of each Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus and any supplement thereto as the Representatives may reasonably request.  The Company will pay the expenses of printing or other production of all documents relating to the offering.

(f)The Company will use its reasonable best efforts to arrange, if necessary, for the qualification of the Securities for sale under the laws of such jurisdictions as the Representatives may reasonably designate and will maintain such qualifications in effect so long as reasonably required for the distribution of the Securities; provided that in no event shall the Company be obligated to qualify to do business in any jurisdiction where it is not now so qualified or to take any action that would subject it to service of process in suits, other than those arising out of the offering or sale of the Securities, in any jurisdiction where it is not now so subject.

(g)The Company will not, without the prior written consent of Citigroup Global Markets Inc., offer, sell, contract to sell, pledge, or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the Company or any affiliate of the Company or any person in privity with the Company or any affiliate of the Company) directly or indirectly, including the filing (or participation in the filing) of a registration statement with the Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act, any other shares of Common Stock or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock; or publicly announce an intention to effect any such transaction, for a period of 180 days after the date of the Underwriting Agreement, provided, however, that (i) the Company may issue and sell Common Stock pursuant to any employee stock option plan, stock ownership plan or dividend reinvestment plan of the Company in effect at the Execution Time, (ii) the Company may file one or more registration statements on Form S-8, (iii) the Company may offer, issue and sell shares of Common Stock or any securities convertible into, or exercisable, or exchangeable for, Common Stock in connection with any acquisition or strategic investment (including any joint venture or partnership) as long as (x) the aggregate number of shares of Common Stock issued or issuable does not exceed 10% of the number of shares of Common Stock outstanding immediately after the issuance and sale of the Securities pursuant to this Agreement and (y) each recipient of any such Common Stock issued or issuable agrees to the restrictions on the resale of securities that are consistent with the lock-up letters described in Section 6(n) hereof for the remainder of the 180-day restricted period and (iv) the Company may issue Common Stock issuable upon the conversion of securities at the Execution Time.  The Company will provide the Representatives and any co-managers and each individual subject to the restricted period pursuant to the lock-

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up letters described in Section 6(n) hereof with prior notice of any such announcement that gives rise to an extension of the restricted period.

(h)If Citigroup Global Markets Inc., in its sole discretion, agrees to release or waive the restrictions set forth in a lock-up letter described in Section 6(n) hereof for an officer or director of the Company and provides the Company with notice of the impending release or waiver at least three Business Days before the effective date of the release or waiver, the Company agrees to announce the impending release or waiver by a press release substantially in the form of Exhibit B hereto through a major news service at least two Business Days before the effective date of the release or waiver.

(i)The Company will not take, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(j)The Company agrees to pay the costs and expenses relating to the following matters:  (i) the preparation, printing or reproduction and filing with the Commission of the Registration Statement (including financial statements and exhibits thereto), each Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus, and each amendment or supplement to any of them; (ii) the printing (or reproduction) and delivery (including postage, air freight charges and charges for counting and packaging) of such copies of the Registration Statement, each Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus, and all amendments or supplements to any of them, as may, in each case, be reasonably requested for use in connection with the offering and sale of the Securities; (iii) the preparation, printing, authentication, issuance and delivery of certificates for the Securities, including any stamp or transfer taxes in connection with the original issuance and sale of the Securities; (iv) the printing (or reproduction) and delivery of this Agreement, any blue sky memorandum and all other agreements or documents printed (or reproduced) and delivered in connection with the offering of the Securities; (v) the registration of the Securities under the Exchange Act and the listing of the Securities on the New York Stock Exchange; (vi) any registration or qualification of the Securities for offer and sale under the securities or blue sky laws of the several states (including filing fees and the reasonable fees and expenses of counsel for the Underwriters (not to exceed $10,000) relating to such registration and qualification); (vii) any filings required to be made with the FINRA (including filing fees and the reasonable fees and expenses of counsel for the Underwriters (not to exceed $10,000) relating to such filings); (viii) all expenses incident to the “road show” for the offering of the Securities, provided that the Underwriters agree to pay the cost of any chartered airplane or other transportation in connection therewith; (ix) the fees and expenses of the Company’s accountants and reserve engineers and the fees and expenses of counsel (including local and special counsel) for the Company and the Selling

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Stockholders; and (ix) all other costs and expenses incident to the performance by the Company and the Selling Stockholders of their obligations hereunder.

(k)The Company agrees that, unless it has or shall have obtained the prior written consent of the Representatives, and each Underwriter, severally and not jointly, agrees with the Company that, unless it has or shall have obtained, as the case may be, the prior written consent of the Company, it has not made and will not make any offer relating to the Securities that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a “free writing prospectus” (as defined in Rule 405) required to be filed by the Company with the Commission or retained by the Company under Rule 433; provided that the prior written consent of the parties hereto shall be deemed to have been given in respect of the Free Writing Prospectuses included in Schedule III hereto and any electronic road show.  Any such free writing prospectus consented to by the Representatives or the Company is hereinafter referred to as a “Permitted Free Writing Prospectus.”  The Company agrees that (x) it has treated and will treat, as the case may be, each Permitted Free Writing Prospectus as an Issuer Free Writing Prospectus and (y) it has complied and will comply, as the case may be, with the requirements of Rules 164 and 433 applicable to any Permitted Free Writing Prospectus, including in respect of timely filing with the Commission, legending and record keeping.

(l)The Company will promptly notify the Representatives if the Company ceases to be an Emerging Growth Company at any time prior to the later of (a) completion of the distribution of the Securities within the meaning of the Securities Act and (b) completion of the 180-day restricted period referred to in Section 5(g) hereof.

(m)If at any time following the distribution of any Written Testing-the-Waters Communication, any event occurs as a result of which such Written Testing-the-Waters Communication would include any untrue statement of a material fact or  omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made at such time not misleading, the Company will (i) notify promptly the Representatives so that use of the Written Testing-the-Waters Communication may cease until it is amended or supplemented; (ii) amend or supplement the Written Testing-the-Waters Communication to correct such statement or omission; and (iii) supply any amendment or supplement to the Representatives in such quantities as may be reasonably requested.

(ii)Each Selling Stockholder agrees with the several Underwriters that:

(a)Such Selling Stockholder will not, without the prior written consent of Citigroup Global Markets Inc., offer, sell, contract to sell, pledge or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition

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or effective economic disposition due to cash settlement or otherwise) by the Selling Stockholder or any affiliate of the Selling Stockholder or any person in privity with the Selling Stockholder or any affiliate of the Selling Stockholder) directly or indirectly, or file (or participate in the filing of) a registration statement with the Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act with respect to, any shares of capital stock of the Company or any securities convertible into or exercisable or exchangeable for such capital stock, or publicly announce an intention to effect any such transaction, for a period of 180 days after the date of this Agreement, other than shares of Common Stock disposed of as bona fide gifts approved by Citigroup Global Markets Inc.

(b)Such Selling Stockholder will not take, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(c)Such Selling Stockholder will advise you promptly, and if requested by you, will confirm such advice in writing, so long as delivery of a prospectus relating to the Securities by an underwriter or dealer may be required under the Act, of any material change in information in the Registration Statement, the Prospectus any Preliminary Prospectus or any Free Writing Prospectus or any amendment or supplement thereto relating to such Selling Stockholder.

(d)Such Selling Stockholder represents that it has not prepared or had prepared on its behalf or used or referred to, and agrees that it will not prepare or have prepared on its behalf or use or refer to, any Free Writing Prospectus, and has not distributed and will not distribute any written materials in connection with the offer or sale of the Securities.

6.Conditions to the Obligations of the Underwriters.  The obligations of the Underwriters to purchase the Underwritten Securities and the Option Securities, as the case may be, shall be subject to the accuracy of the representations and warranties on the part of the Company and the Selling Stockholders contained herein as of the Execution Time, the Closing Date and any settlement date pursuant to Section 3 hereof, to the accuracy of the statements of the Company and the Selling Stockholders made in any certificates pursuant to the provisions hereof, to the performance by the Company and the Selling Stockholders of their respective obligations hereunder and to the following additional conditions:

(a)The Prospectus, and any supplement thereto, have been filed in the manner and within the time period required by Rule 424(b); any material required to be filed by the Company pursuant to Rule 433(d) under the Act shall have been filed with the Commission within the applicable time periods prescribed for such

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filings by Rule 433; and no stop order suspending the effectiveness of the Registration Statement or any notice objecting to its use shall have been issued and no proceedings for that purpose shall have been instituted or threatened.

(b)The Company shall have requested and caused Latham & Watkins LLP and Potter Anderson & Corroon LLP, special counsel for the Company, to have furnished to the Representatives their respective opinions, dated the Closing Date and addressed to the Representatives, in form and substance reasonably satisfactory to the Representatives, substantially in the forms set forth on Exhibits C-1 and C-2 hereto.

(c)On any Closing Date for Option Securities, if applicable, the Selling Stockholders shall have requested and caused [Akin Gump Strauss Hauer & Feld LLP], special counsel for the Selling Stockholders, to have furnished to the Representatives their opinion dated such Closing Date and addressed to the Representatives, in form and substance reasonably satisfactory to the Representatives, substantially in the form set forth on Exhibit C-3 hereto.

(d)The Representatives shall have received from Baker Botts L.L.P., counsel for the Underwriters, such opinion or opinions, dated the Closing Date and addressed to the Representatives, with respect to the issuance and sale of the Securities, the Registration Statement, Disclosure Package and Prospectus (together with any supplement thereto) and other related matters as the Representatives may reasonably require, and the Company and each Selling Stockholder shall have furnished to such counsel such documents as they request for the purpose of enabling them to pass upon such matters.

(e)The Company shall have furnished to the Representatives a certificate of the Company, signed by the Chief Executive Officer or President and the Chief Financial Officer or Chief Accounting Officer of the Company, dated the Closing Date, to the effect that the signers of such certificate have carefully examined the Registration Statement, Disclosure Package and Prospectus and any amendment or supplement thereto, as well as each electronic road show used in connection with the offering of the Securities, and this Agreement and that:

(i)the representations and warranties of the Company in this Agreement are true and correct on and as of the Closing Date with the same effect as if made on the Closing Date and the Company has complied with all the agreements and satisfied all the conditions on its part to be performed or satisfied at or prior to the Closing Date;

(ii)no stop order suspending the effectiveness of the Registration Statement or any notice objecting to its use has been issued and no proceedings for that purpose have been instituted or, to the Company’s knowledge, threatened; and

23

(iii)since the date of the most recent financial statements included in the Disclosure Package and the Prospectus (exclusive of any supplement thereto), there has been no Material Adverse Change, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(f)The Company shall have furnished to the Representatives at the Execution Time a certificate, signed by the Chief Financial Officer substantially in the form set forth on Exhibit D hereto.

(g)On any Closing Date for Option Securities, if applicable, each Selling Stockholder shall have furnished to the Representatives a certificate, signed by such Selling Stockholder, dated such Closing Date, to the effect that the signer of such certificate has carefully examined the Registration Statement, Disclosure Package and Prospectus and any amendment or supplement thereto and this Agreement and that the representations and warranties of such Selling Stockholder in this Agreement are true and correct in all material respects on and as of the Closing Date to the same effect as if made on the Closing Date.

(h)On the date hereof, the Underwriters shall have received from each of Ernst & Young LLP and UHY LLP a “comfort letter” dated the date hereof addressed to the Underwriters, in form and substance satisfactory to the Representatives, covering the financial information in the Registration Statement and Preliminary Prospectus and other customary matters.  In addition, on the Closing Date, the Underwriters shall have received from such accountants a “bring-down comfort letter” dated the Closing Date addressed to the Underwriters, in form and substance satisfactory to the Representatives, in the form of the “comfort letter” delivered on the date hereof, except that (i) it shall cover the financial information in the Registration Statement and the Prospectus and any amendment or supplement thereto and (ii) procedures shall be brought down to a date no more than three (3) days prior to the Closing Date.

(i)On the date hereof, the Underwriters shall have received from CGA, independent petroleum engineers, a letter dated the date hereof addressed to the Underwriters, in form and substance satisfactory to the Representatives, covering the oil and gas reserves information in the Registration Statement and Preliminary Prospectus and other customary matters.  In addition, on the Closing Date, the Underwriters shall have received from such independent petroleum engineers a “bring-down comfort letter” dated the Closing Date addressed to the Underwriters, in form and substance satisfactory to the Representatives, in the form of the “comfort letter” delivered on the date hereof, except that (i) it shall cover the oil and gas reserves information in the Registration Statement and the Prospectus and any amendment or supplement thereto and (ii) procedures shall be brought down to a date no more than three (3) days prior to the Closing Date.

(j)Subsequent to the Execution Time or, if earlier, the dates as of which information is given in the Registration Statement (exclusive of any

24

amendment thereof) and the Prospectus (exclusive of any supplement thereto), there shall not have been (i) any change or decrease in the customary level of comfort provided in the letter or letters referred to in paragraph (h) of this Section 6 or (ii) any change, or any development involving a prospective change, in or affecting the condition (financial or otherwise), prospects, earnings, business or properties of the Company Parties taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto) the effect of which, in any case referred to in clause (i) or (ii) above, is, in the sole judgment of the Representatives, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the Registration Statement, Disclosure Package and Prospectus (exclusive of any amendment or supplement thereto).

(k)Subsequent to the Execution Time, there shall not have been any decrease in the rating of any of the Company’s debt securities by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 3(a)(62) under the Exchange Act) or any notice given of any intended or potential decrease in any such rating or of a possible change in any such rating that does not indicate the direction of the possible change.

(l)Prior to the Closing Date, the Company and the Selling Stockholders shall have furnished to the Representatives such further customary information, certificates and documents as the Representatives may reasonably request.

(m)The Securities shall have been listed and admitted and authorized for trading on the New York Stock Exchange, and reasonably satisfactory evidence of such actions shall have been provided to the Representatives.

(n)At the Execution Time, the Company shall have furnished to the Representatives a letter substantially in the form of Exhibit A hereto from each officer and director of the Company and each of the Selling Stockholders addressed to the Representatives.

If any of the conditions specified in this Section 6 shall not have been fulfilled when and as provided in this Agreement, or if any of the opinions and certificates mentioned above or elsewhere in this Agreement shall not be reasonably satisfactory in form and substance to the Representatives and counsel for the Underwriters, this Agreement and all obligations of the Underwriters hereunder may be canceled at, or at any time prior to, the Closing Date by the Representatives.  Notice of such cancellation shall be given to the Company and each Selling Stockholder in writing or by telephone or facsimile confirmed in writing.

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The documents required to be delivered by this Section 6 shall be delivered at the office of Baker Botts L.L.P., counsel for the Underwriters, at One Shell Plaza, 910 Louisiana Street, Houston, Texas 77002, on the Closing Date.

7.Reimbursement of Underwriters’ Expenses.  If the sale of the Securities provided for herein is not consummated because any condition to the obligations of the Underwriters set forth in Section 6 hereof is not satisfied or because of any refusal, inability or failure on the part of the Company or any Selling Stockholders to perform any agreement herein or comply with any provision hereof other than by reason of a default by any of the Underwriters, the Company will reimburse the Underwriters severally through Citigroup Global Markets Inc. on demand for all expenses (including reasonable fees and disbursements of counsel) that shall have been incurred by them in connection with the proposed purchase and sale of the Securities.  If the Company is required to make any payments to the Underwriters under this Section 7 because of any Selling Stockholder’s refusal, inability or failure to satisfy any condition to the obligations of the Underwriters set forth in Section 6, the Selling Stockholders pro rata in proportion to the percentage of Securities to be sold by each shall reimburse the Company on demand for all amounts so paid.

8.Indemnification and Contribution.  (a) The Company agrees to indemnify and hold harmless each Underwriter, the directors, officers, employees and agents of each Underwriter and each person who controls any Underwriter within the meaning of either the Act or the Exchange Act against any and all losses, claims, damages or liabilities, joint or several, to which they or any of them may become subject under the Act, the Exchange Act or other Federal or state statutory law or regulation, at common law or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon any untrue statement or alleged untrue statement of a material fact contained in the registration statement for the registration of the Securities as originally filed or in any amendment thereof, or in any Preliminary Prospectus, or in the Prospectus or in any Issuer Free Writing Prospectus, or in any Written Testing-the-Waters Communication or in any amendment thereof or supplement thereto, or arise out of or are based upon the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with investigating or defending any such loss, claim, damage, liability or action; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon any such untrue statement or alleged untrue statement or omission or alleged omission made therein in reliance upon and in conformity with written information furnished to the Company by or on behalf of any Underwriter through the Representatives specifically for inclusion therein.  This indemnity agreement will be in addition to any liability which the Company may otherwise have.

(b)Each Selling Stockholder severally agrees to indemnify and hold harmless the Company, each of its directors, each of its officers who signs the Registration Statement and each Underwriter, the directors, officers, employees

26

and agents of each Underwriter to the same extent as the foregoing indemnity from the Company to each Underwriter, but only with reference to written information furnished to the Company by or on behalf of such Selling Stockholder specifically for inclusion in the documents referred to in the foregoing indemnity.  This indemnity agreement will be in addition to any liability which any Selling Stockholder may otherwise have.

(c)Each Underwriter severally and not jointly agrees to indemnify and hold harmless the Company, each of its directors, each of its officers who signs the Registration Statement, and each person who controls the Company within the meaning of either the Act or the Exchange Act and each Selling Stockholder, to the same extent as the foregoing indemnity to each Underwriter, but only with reference to written information relating to such Underwriter furnished to the Company by or on behalf of such Underwriter through the Representatives specifically for inclusion in the documents referred to in the foregoing indemnity.  This indemnity agreement will be in addition to any liability which any Underwriter may otherwise have.  The Company and each Selling Stockholder acknowledge that the statements set forth (i) in the last paragraph of the cover page regarding delivery of the Securities and, under the heading “Underwriting (Conflicts of Interest)”, (ii) the list of Underwriters and their respective participation in the sale of the Securities, (iii) the sentences related to concessions and reallowances and (iv) the paragraphs related to stabilization, syndicate covering transactions and penalty bids in any Preliminary Prospectus and the Prospectus constitute the only information furnished in writing by or on behalf of the several Underwriters for inclusion in any Preliminary Prospectus, the Prospectus and any Issuer Free Writing Prospectus.

(d)Promptly after receipt by an indemnified party under this Section 8 of notice of the commencement of any action, such indemnified party will, if a claim in respect thereof is to be made against the indemnifying party under this Section 8, notify the indemnifying party in writing of the commencement thereof; but the failure so to notify the indemnifying party (i) will not relieve it from liability under paragraph (a), (b) or (c) above unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses and (ii) will not, in any event, relieve the indemnifying party from any obligations to any indemnified party other than the indemnification obligation provided in paragraph (a), (b) or (c) above.  The indemnifying party shall be entitled to appoint counsel of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought (in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided, however, that such counsel shall be reasonably satisfactory to the indemnified party.  Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ one separate counsel (including local counsel), and the indemnifying party shall bear

27

the reasonable fees, costs and expenses of such separate counsel if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel reasonably satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party.  An indemnifying party will not, without the prior written consent of the indemnified parties (which consent shall not be unreasonably withheld), settle or compromise or consent to the entry of any judgment with respect to any pending or threatened claim, action, suit or proceeding in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified parties are actual or potential parties to such claim or action) unless such settlement, compromise or consent includes an unconditional release of each indemnified party from all liability arising out of such claim, action, suit or proceeding.

(e)In the event that the indemnity provided in paragraph (a), (b) or (c) of this Section 8 is unavailable to or insufficient to hold harmless an indemnified party for any reason, the Company, the Selling Stockholders and the Underwriters agree to contribute to the aggregate losses, claims, damages and liabilities (including legal or other expenses reasonably incurred in connection with investigating or defending same) (collectively “Losses”) to which the Company, one or more of the Selling Stockholders and one or more of the Underwriters may be subject in such proportion as is appropriate to reflect the relative benefits received by the Company, by the Selling Stockholders and by the Underwriters from the offering of the Securities; provided, however, that in no case shall any Underwriter (except as may be provided in any agreement among underwriters relating to the offering of the Securities) be responsible for any amount in excess of the underwriting discount or commission applicable to the Securities purchased by such Underwriter hereunder.  If the allocation provided by the immediately preceding sentence is unavailable for any reason, the Company, the Selling Stockholders and the Underwriters shall contribute in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company, of the Selling Stockholders and of the Underwriters in connection with the statements or omissions which resulted in such Losses as well as any other relevant equitable considerations.  Benefits received by the Company and by the Selling Stockholders shall be deemed to be equal to the total net proceeds from the offering (before deducting expenses) received by each of them, and benefits received by the Underwriters shall be deemed to be equal to the total underwriting discounts and commissions, in each case as set forth on the cover page of the Prospectus.  Relative fault shall be determined by reference to, among other things, whether any untrue or any alleged untrue statement of a material fact

28

or the omission or alleged omission to state a material fact relates to information provided by the Company, the Selling Stockholders or the Underwriters, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such untrue statement or omission.  The Company, the Selling Stockholders and the Underwriters agree that it would not be just and equitable if contribution were determined by pro rata allocation or any other method of allocation which does not take account of the equitable considerations referred to above.  Notwithstanding the provisions of this paragraph (e), no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.  For purposes of this Section 8, each person who controls an Underwriter within the meaning of either the Act or the Exchange Act and each director, officer, employee and agent of an Underwriter shall have the same rights to contribution as such Underwriter, and each person who controls the Company within the meaning of either the Act or the Exchange Act, each officer of the Company who shall have signed the Registration Statement and each director of the Company shall have the same rights to contribution as the Company, subject in each case to the applicable terms and conditions of this paragraph (e).

(f)The liability of each Selling Stockholder under such Selling Stockholder’s representations and warranties contained in Section 1 hereof and under the indemnity and contribution agreements contained in this Section 8 shall be limited to an amount equal to the initial public offering price of the Securities sold by such Selling Stockholder to the Underwriters.  The Company and the Selling Stockholders may agree, as among themselves and without limiting the rights of the Underwriters under this Agreement, as to the respective amounts of such liability for which they each shall be responsible.

9.Default by an Underwriter.  If any one or more Underwriters shall fail to purchase and pay for any of the Securities agreed to be purchased by such Underwriter or Underwriters hereunder and such failure to purchase shall constitute a default in the performance of its or their obligations under this Agreement, the remaining Underwriters shall be obligated severally to take up and pay for (in the respective proportions which the amount of Securities set forth opposite their names in Schedule I hereto bears to the aggregate amount of Securities set forth opposite the names of all the remaining Underwriters) the Securities which the defaulting Underwriter or Underwriters agreed but failed to purchase; provided, however, that in the event that the aggregate amount of Securities which the defaulting Underwriter or Underwriters agreed but failed to purchase shall exceed 10% of the aggregate amount of Securities set forth in Schedule I hereto, the remaining Underwriters shall have the right to purchase all, but shall not be under any obligation to purchase any, of the Securities, and if such nondefaulting Underwriters do not purchase all the Securities, this Agreement will terminate without liability to any nondefaulting Underwriter, the Selling Stockholders or the Company.  In the event of a default by any Underwriter as set forth in this Section 9, the Closing Date shall be postponed for such period, not exceeding five Business Days, as the Representatives shall determine in order that the required changes in the

29

Registration Statement, Disclosure Package and Prospectus or in any other documents or arrangements may be effected.  Nothing contained in this Agreement shall relieve any defaulting Underwriter of its liability, if any, to the Company, the Selling Stockholders and any nondefaulting Underwriter for damages occasioned by its default hereunder.

10.Termination.  This Agreement shall be subject to termination in the absolute discretion of the Representatives, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such delivery and payment (i) trading in the Company’s Common Stock shall have been suspended by the Commission or the New York Stock Exchange or trading in securities generally on the New York Stock Exchange shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by Federal, New York or Delaware authorities or a material disruption in commercial banking or securities settlement or clearance services in the United States has occurred or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representatives, impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the Preliminary Prospectus or the Prospectus (exclusive of any amendment or supplement thereto).

11.Representations and Indemnities to Survive. The respective agreements, representations, warranties, indemnities and other statements of the Company or its officers, of each Selling Stockholder and of the Underwriters set forth in or made pursuant to this Agreement will remain in full force and effect, regardless of any investigation made by or on behalf of any Underwriter, any Selling Stockholder or the Company or any of the officers, directors, employees, agents or controlling persons referred to in Section 8 hereof, and will survive delivery of and payment for the Securities.  The provisions of Sections 7 and 8 hereof shall survive the termination or cancellation of this Agreement.

12.Notices.  All communications hereunder will be in writing and effective only on receipt, and, if sent to the Representatives, will be mailed, delivered or telefaxed to the Citigroup Global Markets Inc. General Counsel (fax no.: (212) 816-7912) and confirmed to the General Counsel, Citigroup Global Markets Inc., at 388 Greenwich Street, New York, New York, 10013, Attention: General Counsel; or, if sent to the Company, will be mailed, delivered or telefaxed to the Athlon Energy Inc. Chief Executive Officer (fax no.: (817) 984-8217) and confirmed to the Chief Executive Officer, Athlon Energy Inc., at 420 Throckmorton Street, Suite 1200, Fort Worth, Texas, 76102, Attention: Chief Executive Officer; or if sent to any Selling Stockholder, will be mailed, delivered or telefaxed and confirmed to it at the address set forth in Schedule II hereto.

13.Successors.  This Agreement will inure to the benefit of and be binding upon the parties hereto and their respective successors and the officers, directors, employees, agents and controlling persons referred to in Section 8 hereof, and no other person will have any right or obligation hereunder.

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14.No fiduciary duty. The Company and the Selling Stockholders hereby acknowledge that (a) the purchase and sale of the Securities pursuant to this Agreement is an arm’s-length commercial transaction between the Company and the Selling Stockholders, on the one hand, and the Underwriters and any affiliate through which it may be acting, on the other, (b) the Underwriters are acting as principal and not as an agent or fiduciary of the Company or the Selling Stockholders and (c) the Company’s engagement of the Underwriters in connection with the offering and the process leading up to the offering is as independent contractors and not in any other capacity. Furthermore, the Company and the Selling Stockholders agree that they are solely responsible for making their own judgments in connection with the offering (irrespective of whether any of the Underwriters has advised or is currently advising the Company or any Selling Stockholder on related or other matters).  The Company and the Selling Stockholders agree that they will not claim that the Underwriters have rendered advisory services of any nature or respect, or owe an agency, fiduciary or similar duty to the Company or any of the Selling Stockholders, in connection with such transaction or the process leading thereto.

15.Integration. This Agreement supersedes all prior agreements and understandings (whether written or oral) between the Company, the Selling Stockholders and the Underwriters, or any of them, with respect to the subject matter hereof.

16.Applicable Law.  This Agreement will be governed by and construed in accordance with the laws of the State of New York applicable to contracts made and to be performed within the State of New York.

17.Waiver of Jury Trial. The Company and the Selling Stockholders hereby irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

18.Counterparts.  This Agreement may be signed in one or more counterparts, each of which shall constitute an original and all of which together shall constitute one and the same agreement.

19.Headings.  The section headings used herein are for convenience only and shall not affect the construction hereof.

20.Definitions.  The terms that follow, when used in this Agreement, shall have the meanings indicated.

“Act” shall mean the Securities Act of 1933, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Business Day” shall mean any day other than a Saturday, a Sunday or a legal holiday or a day on which banking institutions or trust companies are authorized or obligated by law to close in New York City.

“Commission” shall mean the Securities and Exchange Commission.

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“Disclosure Package” shall mean (i) the Preliminary Prospectus that is generally distributed to investors and used to offer the Securities, (ii) the Issuer Free Writing Prospectuses, if any, identified in Schedule III hereto, and (iii) any other Free Writing Prospectus that the parties hereto shall hereafter expressly agree in writing to treat as part of the Disclosure Package.

“Effective Date” shall mean each date and time that the Registration Statement, any post-effective amendment or amendments thereto and any Rule 462(b) Registration Statement became or becomes effective.

“Exchange Act” shall mean the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Execution Time” shall mean the date and time that this Agreement is executed and delivered by the parties hereto.

“Free Writing Prospectus” shall mean a free writing prospectus, as defined in Rule 405.

“Issuer Free Writing Prospectus” shall mean an issuer free writing prospectus, as defined in Rule 433.

“Preliminary Prospectus” shall mean any preliminary prospectus referred to in paragraph 1(i)(a) above and any preliminary prospectus included in the Registration Statement at the Effective Date that omits Rule 430A Information.

“Prospectus” shall mean the prospectus relating to the Securities that is first filed pursuant to Rule 424(b) after the Execution Time.

“Registration Statement” shall mean the registration statement referred to in paragraph 1(i)(a) above, including exhibits and financial statements and any prospectus supplement relating to the Securities that is filed with the Commission pursuant to Rule 424(b) and deemed part of such registration statement pursuant to Rule 430A, as amended at the Execution Time and, in the event any post-effective amendment thereto or any Rule 462(b) Registration Statement becomes effective prior to the Closing Date, shall also mean such registration statement as so amended or such Rule 462(b) Registration Statement, as the case may be.

“Rule 158”, “Rule 163”, “Rule 164”, “Rule 172”, “Rule 405”, “Rule 415”, “Rule 424”, “Rule 430A” and “Rule 433” refer to such rules under the Act.

“Rule 430A Information” shall mean information with respect to the Securities and the offering thereof permitted to be omitted from the Registration Statement when it becomes effective pursuant to Rule 430A.

“Rule 462(b) Registration Statement” shall mean a registration statement and any amendments thereto filed pursuant to Rule 462(b) relating to the offering covered by the registration statement referred to in Section 1(i)(a) hereof.

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“Testing-the-Waters Communication” shall mean any oral or written communication with potential investors undertaken in reliance on Section 5(d) of the Act.

“Written Testing-the-Waters Communication” shall mean any Testing-the-Waters Communication that is a written communication within the meaning of Rule 405.

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to us the enclosed duplicate hereof, whereupon this letter and your acceptance shall represent a binding agreement among the Company, the Selling Stockholder(s) and the several Underwriters.

Very truly yours,
Athlon Energy Inc.
By:
	Name: Robert C. Reeves
	Title: President and Chief Executive Officer
[Selling Stockholder]
By:
	Name:
	Title:
[Selling Stockholder]
By:
	Name:
	Title:

34

The foregoing Agreement is hereby confirmed and accepted as of the date first above written.
Citigroup Global Markets Inc.
By:
	Name:
	Title:
For itself and the other several Underwriters named in Schedule I to the foregoing Agreement.

35

EX-5.1

Exhibit 5.1

	811 Main Street, Suite 3700 Houston, TX 77002 Tel: +1.713.546.5400 Fax: +1.713.546.5401 www.lw.com
	FIRM / AFFILIATE OFFICES
	Abu Dhabi	Milan
	Barcelona	Moscow
	Beijing	Munich
	Boston	New Jersey
	Brussels	New York
	Chicago	Orange County
	Doha	Paris
	Dubai	Riyadh
	Düsseldorf	Rome
	Frankfurt	San Diego
	Hamburg	San Francisco
	Hong Kong	Shanghai
	Houston	Silicon Valley
	London	Singapore
	Los Angeles	Tokyo
	Madrid	Washington, D.C.

July 22, 2013
Athlon Energy Inc.
420 Throckmorton Street,
Suite 1200
Fort Worth, Texas 76102

Re:

Form S-1 Registration Statement File No. 333-189109
Initial Public Offering of up to 18,157,895 Shares of Common Stock of Athlon Energy Inc.

Ladies and Gentlemen:

        We have acted as special counsel to Athlon Energy Inc., a Delaware corporation (the "Company"), in connection with the proposed issuance of up to 18,157,895 shares of common stock, $0.01 par value per share, up to 15,789,474 shares of which are being offered by the Company (the "Company Shares") and up to 2,368,421 shares (subject to the underwriters' option to purchase additional shares) of which are being offered by certain stockholders of the Company (the "Selling Stockholder Shares," and together with the Company Shares, the "Shares"). The Shares are included in a registration statement on Form S-1 under the Securities Act of 1933, as amended (the "Act"), filed with the Securities and Exchange Commission (the "Commission") on June 5, 2013 (Registration No. 333-189109) (as amended, the "Registration Statement"). The term "Shares" shall include any additional shares of common stock registered by the Company pursuant to Rule 462(b) under the Act in connection with the offering contemplated by the Registration Statement. This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or related Prospectus (the "Prospectus"), other than as expressly stated herein with respect to the issue of the Shares.

        As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to General Corporation Law of the State of Delaware (the "Delaware Act"), and we express no opinion with respect to any other laws.

July 22, 2013
Page 2

        Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof:

        1.     When the Company Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the purchasers and have been issued by the Company against payment therefor (not less than par value) in the circumstances contemplated by the form of underwriting agreement most recently filed as an exhibit to the Registration Statement, the issue and sale of the Company Shares will have been duly authorized by all necessary corporate action of the Company, and the Company Shares will be validly issued, fully paid and nonassessable. In rendering the foregoing opinion, we have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the Delaware Act.

        2.     The Selling Stockholder Shares have been duly authorized by all necessary corporate action of the Company and are validly issued, fully paid and nonassessable.

        This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm in the Prospectus under the heading "Legal Matters." We further consent to the incorporation by reference of this letter and consent into any registration statement filed pursuant to Rule 462(b) with respect to the Shares. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ Latham & Watkins LLP

EX-23.1

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Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption "Experts" and to the use of our report dated March 8, 2013 with respect to the consolidated financial statements of Athlon Holdings LP and our report dated June 4, 2013 with respect to the balance sheet of Athlon Energy Inc., in Amendment No. 3 to the Registration Statement (Form S-1 No. 333-189109) and related Prospectus of Athlon Energy Inc.

/s/ ERNST & YOUNG LLP

Fort Worth, Texas
July 18, 2013

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Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

EX-23.2

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Exhibit 23.2

Consent of Independent Registered Public Accounting Firm

We consent to the reference to our firm under the caption "Experts" and to the use of our report dated May 16, 2012 with respect to the carve out financial statements of Element Petroleum, LP's Permian Basin Operations as of and for the nine months ended September 30, 2011 in Amendment No. 3 to the Registration Statement (Form S-1 No. 333-189109) and related Prospectus of Athlon Energy Inc.

        /s/ UHY LLP

Houston, Texas
July 22, 2013

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Exhibit 23.2

Consent of Independent Registered Public Accounting Firm

EX-23.3

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Exhibit 23.3

CAWLEY, GILLESPIE & ASSOCIATES, INC.

	PETROLEUM CONSULTANTS
13640 BRIARWICK DRIVE, SUITE 100 AUSTIN, TEXAS 78729-1707 512-249-7000	306 WEST SEVENTH STREET, SUITE 302 FORT WORTH, TEXAS 76102-4987 817-336-2461 www.cgaus.com	1000 LOUISIANA STREET, SUITE 625 HOUSTON, TEXAS 77002-5008 713-651-9944

CONSENT OF INDEPENDENT PETROLEUM ENGINEERS

        We hereby consent to the references to our firm in this Amendment No. 3 to the Registration Statement on Form S-1 and all appendixes, exhibits and attachments thereto (including the related prospectus) filed by Athlon Energy Inc., and to the use of our audit of their reserves and reserves present value as of December 31, 2011 and 2012 for Athlon Energy Inc. and its predecessors (the "Registration Statement"). We also consent to all references to our firm in the prospectus included in such Registration Statement, including under the heading "Experts."

Sincerely,

/s/ Robert Ravnaas
Cawley, Gillespie & Associates, Inc.

Texas Registered Engineering Firm F-693

July 22, 2013
Fort Worth, Texas

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Exhibit 23.3

CAWLEY, GILLESPIE & ASSOCIATES, INC.
CONSENT OF INDEPENDENT PETROLEUM ENGINEERS