8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(d) OF

THE SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported): November 10, 2011

MARKWEST ENERGY PARTNERS, L.P.

(Exact name of registrant as specified in its charter)

Delaware	001-31239	27-0005456
(State or other jurisdiction of incorporation or organization)	(Commission File Number)	(I.R.S. Employer Identification Number)

1515 Arapahoe Street, Tower 1, Suite 1600, Denver CO 80202

(Address of principal executive offices)

Registrant’s telephone number, including area code: 303-925-9200

Not Applicable.

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

oWritten Communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

oSoliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

oPre-Commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

oPre-Commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

ITEM 1.01.    Entry into a Material Agreement.

Sixth Supplemental Indenture for 8.75% Senior Notes due 2018

On November 10, 2011, MarkWest Energy Partners, L.P. (the “Partnership”) announced that it had accepted for purchase and payment (the “Initial Settlement”) approximately 76% of the outstanding $334.2 million aggregate principal amount of its 8.75% Senior Notes due 2018 (CUSIP No. 570506AH8) (the “Notes”) that were validly tendered (and not validly withdrawn) prior to 5:00 p.m., New York City time, on November 9, 2011 pursuant to its previously announced tender offer and consent solicitation, which commenced on October 25, 2011.  In addition, on November 10, 2011, payment for the Notes pursuant to the Initial Settlement was made.  The tender offer for the Notes will expire on November 25, 2011, unless extended by the Partnership in its sole discretion. Assuming no additional Notes are tendered for repurchase prior to the expiration of the tender offer,  the Partnership will record a pre-tax loss on redemption of debt of approximately $36 million, which consists of approximately $32 million for the payment of the related tender premiums and third-party expenses and approximately $4 million for the non-cash write off of the unamortized discount and deferred finance costs.

On November 10, 2011, following receipt of the requisite consents of the holders of the Notes, the Partnership entered into the Sixth Supplemental Indenture (the “Sixth Supplemental Indenture”), by and among the Partnership, its wholly-owned subsidiary MarkWest Energy Finance Corporation (“Finance Corp.”), certain subsidiary guarantors named therein and Wells Fargo Bank, National Association, to the Indenture, dated as of April 15, 2008, by and among the Partnership, Finance Corp., the subsidiary guarantors named therein and Wells Fargo Bank, National Association, as amended.  The Sixth Supplemental Indenture eliminates most of the restrictive covenants and certain default provisions respecting the Notes.  The Sixth Supplemental Indenture became operative upon the purchase by the Partnership of a majority of the outstanding Notes pursuant to its tender offer and consent solicitation.

A copy of the Sixth Supplemental Indenture is filed as Exhibit 4.1 hereto and is incorporated herein by reference.  The description of the Sixth Supplemental Indenture contained herein is qualified in its entirety by the full text of such exhibit.

ITEM 7.01.    Regulation FD Disclosure

On November 10, 2011, the Partnership issued a press release, which announced the receipt of the requisite consents with respect to its tender offer and consent solicitation for its Notes. The press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated by reference into this Item 7.01.

The information contained in this Item 7.01 shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or incorporated by reference in any filing under the Securities Act or the Exchange Act, except as shall be expressly set forth by specific reference in such filing.

2

ITEM 9.01.    Financial Statements and Exhibits.

(d)         Exhibits.

Exhibit No.	Description of Exhibit
4.1	Sixth Supplemental Indenture, dated as of November 10, 2011, by and among MarkWest Energy Partners, L.P., MarkWest Energy Finance Corporation, the Subsidiary Guarantors named therein and Wells Fargo Bank, National Association, as trustee.
99.1	Press release dated November 10, 2011, announcing the receipt of the requisite consents with respect to its tender offer and consent solicitation for its Notes.

3

SIGNATURE

Pursuant to the requirements of the Securities and Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	MARKWEST ENERGY PARTNERS, L.P.
	(Registrant)
	By:	MarkWest Energy GP, L.L.C.,
		Its General Partner
Date: November 15, 2011	By:	/s/ NANCY K. BUESE
		Nancy K. Buese
		Senior Vice President and Chief Financial Officer

4

EX-4.1

Exhibit 4.1

MARKWEST ENERGY PARTNERS, L.P.

AND

MARKWEST ENERGY FINANCE CORPORATION

AND

THE SUBSIDIARY GUARANTORS NAMED HEREIN,

AND

WELLS FARGO BANK, NATIONAL ASSOCIATION,

as Trustee

SIXTH SUPPLEMENTAL INDENTURE

Dated as of November 10, 2011

to

Indenture

Dated as of April 15, 2008

8.75% Senior Notes due 2018

THIS SIXTH SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of November 10, 2011, is by and among MarkWest Energy Partners, L.P., a Delaware limited partnership (the “Company”), MarkWest Energy Finance Corporation, a Delaware corporation (“Finance Corp.” and, together with the Company, the “Issuers”), the Subsidiary Guarantors (as defined in the Indenture referred to herein), and Wells Fargo Bank, National Association, as trustee (the “Trustee”).

WHEREAS, the Issuers, the Subsidiary Guarantors and the Trustee are parties to that certain Indenture dated as of April 15, 2008 (the “Original Indenture”), relating to the Issuers’ 8.75% Senior Notes due 2018 (the “Notes”), and the Original Indenture has been amended and supplemented by five Supplemental Indentures (the Original Indenture, as so amended and supplemented, being referred to herein as the “Indenture”);

WHEREAS, $334,362,000 in principal amount of Notes is currently outstanding;

WHEREAS, Section 9.02 of the Indenture provides that, with the consent of the Holders of a majority in principal amount of the Notes then outstanding (including, without limitation, consents obtained in connection with a tender offer for Notes), the Issuers, the Subsidiary Guarantors and the Trustee may enter into an indenture supplemental to the Indenture for the purpose of amending or supplementing the Indenture or the Notes (subject to certain exceptions);

WHEREAS, the Issuers desire and have requested the Trustee to join with them and the Subsidiary Guarantors in entering into this Supplemental Indenture for the purpose of amending the Indenture and the Notes in certain respects as permitted by Section 9.02 of the Indenture;

WHEREAS, the Company has been soliciting consents to this Supplemental Indenture upon the terms and subject to the conditions set forth in its Offer to Purchase and Consent Solicitation Statement dated October 25, 2011 and the related Consent and Letter of Transmittal (which together, including any amendments, modifications or supplements thereto, constitute the “Tender Offer”);

WHEREAS, (1) the Company has received the consent of the Holders of a majority in principal amount of the outstanding Notes (excluding any Notes owned by the Company or any of its Affiliates), all as certified by an Officers’ Certificate delivered to the Trustee simultaneously with the execution and delivery of this Supplemental Indenture, (2) the Company has delivered to the Trustee simultaneously with the execution and delivery of this Supplemental Indenture an Opinion of Counsel relating to this Supplemental Indenture as contemplated by Section 9.06 of the Indenture and (3) the Issuers and the Subsidiary Guarantors have satisfied all other conditions required under Article 9 of the Indenture to enable the Issuers, the Subsidiary Guarantors and the Trustee to enter into this Supplemental Indenture.

NOW, THEREFORE, in consideration of the above premises, each party hereby agrees, for the benefit of the others and for the equal and ratable benefit of the Holders of the Notes, as follows:

1

ARTICLE I

AMENDMENTS TO INDENTURE AND NOTES

Section 1.1Amendments to Articles 3. 4. 5 and 6.  The Indenture is hereby amended by deleting the following Sections or clauses of the Indenture and all references and definitions related thereto in their entirety:

Section 3.09 (Offer to Purchase by Application of Net Proceeds);

Section 4.03(c) (Compliance Certificate);

Section 4.04 (Taxes);

Section 4.05 (Stay, Extension and Usury Laws);

Section 4.06 (Change of Control);

Section 4.07 (Asset Sales);

Section 4.08 (Restricted Payments);

Section 4.09 (Incurrence of Indebtedness and Issuance of Disqualified Equity);

Section 4.10 (Liens);

Section 4.11 (Dividend and Other Payment Restrictions Affecting Subsidiaries);

Section 4.12 (Transactions With Affiliates);

Section 4.13 (Additional Subsidiary Guarantees);

Section 4.14 (Designation of Restricted and Unrestricted Subsidiaries);

Section 4.15 (Business Activities);

Section 4.16 (Sale and Leaseback Transactions);

Section 4.17 (Payments for Consent);

Section 4.18 (Reports), except as required by Section 314(a) of the TIA;

Clauses (iii) and (iv) of Section 5.01(a) (Merger, Consolidation, or Sale of Assets); and Clauses (g) and (h) of Section 6.01 (Events of Default).

Section 1.2Amendments to Notes. The Notes are hereby amended to delete all provisions inconsistent with the amendments to the Indenture effected by this Supplemental Indenture.

ARTICLE II

MISCELLANEOUS PROVISIONS

Section 2.1Defined Terms.  For all purposes of this Supplemental Indenture, except as otherwise defined or unless the context otherwise requires, terms used in capitalized form in this Supplemental Indenture and defined in the Indenture have the meanings specified in the Indenture.

Section 2.2Indenture.  Except as amended hereby, the Indenture and the Notes are in all respects ratified and confirmed and all the terms shall remain in full force and effect.  This Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder of Notes heretofore or hereafter authenticated and delivered under the Indenture shall be bound hereby and all terms and conditions of both shall be read together as though they constitute a

2

single instrument, except that in the case of conflict the provisions of this Supplemental Indenture shall control.

Section 2.3Governing Law.  THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

Section 2.4Successors.  All agreements of the Issuers and the Subsidiary Guarantors in this Supplemental Indenture and the Notes shall bind their respective successors.  All agreements of the Trustee in this Supplemental Indenture shall bind its successors.

Section 2.5Duplicate Originals.  All parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together shall represent the same agreement. It is the express intent of the parties to be bound by the exchange of signatures on this Supplemental Indenture via telecopy or other form of electronic transmission.

Section 2.6Severability.  In case any one or more of the provisions in this Supplemental Indenture or in the Notes shall be held invalid, illegal or unenforceable, in any respect for any reason, the validity, legality and enforceability of any such provision in every other respect and of the remaining provisions shall not in any way be affected or impaired thereby, it being intended that all of the provisions hereof shall be enforceable to the fullest extent permitted by law.

Section 2.7Trustee Disclaimer.  The Trustee accepts the amendments of the Indenture effected by this Supplemental Indenture and agrees to execute the trust created by the Indenture as hereby amended, but on the terms and conditions set forth in the Indenture, including the terms and provisions defining and limiting the liabilities and responsibilities of the Trustee, which terms and provisions shall in like manner define and limit its liabilities and responsibilities in the performance of the trust created by the Indenture as hereby amended, and without limiting the generality of the foregoing, the Trustee shall not be responsible in any manner whatsoever for or with respect to any of the recitals or statements contained herein, all of which recitals or statements are made solely by the Issuers and the Subsidiary Guarantors, and the Trustee makes no representation with respect to any such matters.  Additionally, the Trustee makes no representations as to the validity or sufficiency of this Supplemental Indenture.

Section 2.8Effectiveness.  The provisions of this Supplemental Indenture shall be effective only upon execution and delivery of this instrument by the parties hereto.  Notwithstanding the foregoing sentence, the provisions of this Supplemental Indenture shall become operative only upon the purchase by the Company, pursuant to the Tender Offer, of a majority in principal amount of the outstanding Notes (excluding, for this purpose, any Notes owned by the Company or any of its Affiliates), with the result that the amendments to the Indenture effected by this Supplemental Indenture shall be deemed to be revoked retroactive to the date hereof if such purchase shall not occur.  The Company shall notify the Trustee promptly after the occurrence of such purchase or promptly after the Company shall determine that such purchase will not occur.

3

Section 2.9Endorsement and Change of Form of Notes.  Any Notes authenticated and delivered after the close of business on the date that this Supplemental Indenture becomes operative in substitution for Notes then outstanding and all Notes presented or delivered to the Trustee on and after that date for such purpose shall be stamped, imprinted or otherwise legended by the Company, with a notation as follows:

“Effective as of November 10, 2011, certain restrictive covenants of the Issuers and certain Events of Default have been eliminated or limited, as provided in the Sixth Supplemental Indenture, dated as of November 10, 2011.  Reference is hereby made to such Sixth Supplemental Indenture, copies of which are on file with the Trustee, for a description of the amendments made therein.”

Section 2.10Effect of Headings.  The Section headings herein are for convenience only and shall not affect the construction thereof.

[THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

4

IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed as of the day and year written above.

Issuers:
MARKWEST ENERGY PARTNERS, L.P.
By: MarkWest Energy GP, L.L.C., its General Partner
By:	/s/ Nancy K. Buese
Name:	Nancy K. Buese
Title:	Senior Vice President and Chief Financial Officer
MARKWEST ENERGY FINANCE CORPORATION
By:	/s/ Nancy K. Buese
Name:	Nancy K. Buese
Title:	Senior Vice President and Chief Financial Officer
Subsidiary Guarantors:
MARKWEST ENERGY GP, L.L.C.
MARKWEST HYDROCARBON, INC.
By:	/s/ Nancy K. Buese
Name:	Nancy K. Buese
Title:	Senior Vice President and Chief Financial Officer
MASON PIPELINE LIMITED LIABILITY COMPANY
By:  MarkWest Hydrocarbon, Inc., its Sole Member
By:	/s/ Nancy K. Buese
Name:	Nancy K. Buese
Title:	Senior Vice President and Chief Financial Officer

Signature Page - Sixth Supplemental Indenture

MARKWEST ENERGY OPERATING COMPANY, L.L.C.
By:  MarkWest Energy Partners, L.P., its Managing Member
By:  MarkWest Energy GP, L.L.C., its General Partner
By:		/s/ Nancy K. Buese
Name:		Nancy K. Buese
Title:		Senior Vice President and Chief Financial Officer
WEST SHORE PROCESSING COMPANY, L.L.C.
MARKWEST BLACKHAWK, L.L.C.
MARKWEST ENERGY APPALACHIA, L.L.C.
MARKWEST ENERGY EAST TEXAS GAS COMPANY, .L.C.
MARKWEST GAS MARKETING, L.L.C.
MARKWEST GAS SERVICES, L.L.C.
MARKWEST JAVELINA COMPANY, L.L.C.
MARKWEST JAVELINA PIPLELINE COMPANY, L.L.C.
MARKWEST LIBERTY GAS GATHERING, L.L.C.
MARKWEST MARKETING, L.L.C.
MARKWEST NEW MEXICO, L.L.C.
MARKWEST PINNACLE, L.L.C.
MARKWEST PIPELINE COMPANY, L.L.C.
MARKWEST PNG UTILITY, L.L.C.
MARKWEST POWER TEX, L.L.C.
MARKWEST TEXAS PNG UTILITY, L.L.C.
MARKWEST MOUNTAINEER PIPELINE COMPANY, L.L.C.
MARKWEST MICHIGAN PIPELINE COMPANY, L.L.C.
MARKWEST OKLAHOMA GAS COMPANY, L.L.C.
By:	MarkWest Energy Operating Company, L.L.C.,
	their Sole Member
By:	MarkWest Energy Partners, L.P., its Managing
	Member
By:	MarkWest Energy GP, L.L.C., its General Partner
By:		/s/ Nancy K. Buese
Name:		Nancy K. Buese
Title:		Senior Vice President and Chief Financial Officer

Signature Page - Sixth Supplemental Indenture

MATREX, L.L.C.
By:	West Shore Processing Company L.L.C., its Sole Member
By:	MarkWest Energy Operating Company, L.L.C., its Sole Member
By:	MarkWest Energy Partners, L.P., its Managing Member
By:	MarkWest Energy GP, L.L.C., its General Partner
By:			/s/ Nancy K. Buese
Name:			Nancy K. Buese
Title:			Senior Vice President and Chief Financial Officer
MARKWEST MCALESTER, L.L.C.
By:		MarkWest Oklahoma Gas Company, L.L.C., its Sole Member
By:		MarkWest Energy Operating Company, L.L.C., its Sole Member
By:		MarkWest Energy Partners, L.P., its Managing Member
By:		MarkWest Energy GP, L.L.C., its General Partner
By:			/s/ Nancy K. Buese
Name:			Nancy K. Buese
Title:			Senior Vice President and Chief Financial Officer

Signature Page - Sixth Supplemental Indenture

MARKWEST RANGER PIPELINE COMPANY, L.L.C.
By:	MarkWest Energy Appalachia, L.L.C., its Sole Member
By:	MarkWest Energy Operating Company, L.L.C., its Sole Member
By:	MarkWest Energy Partners, L.P., its Managing Member
By:	MarkWest Energy GP, L.L.C., its General Partner
By:		/s/ Nancy K. Buese
Name:		Nancy K. Buese
Title:		Senior Vice President and Chief Financial Officer

Signature Page - Sixth Supplemental Indenture

WELLS FARGO BANK, NATIONAL ASSOCIATION,
as Trustee
By:	/s/ Patrick T. Giordano
Name:	Patrick T. Giordano
Title:	Vice President

Signature Page - Sixth Supplemental Indenture

EX-99.1

Exhibit 99.1

MarkWest Energy Partners, L.P.	Contact:	Frank Semple, Chairman, President & CEO
1515 Arapahoe Street		Nancy Buese, Senior VP and CFO
Tower 1, Suite 1600		Dan Campbell, VP of Finance & Treasurer
Denver, CO 80202	Phone:	(866) 858-0482
	E-mail:	investorrelations@markwest.com

MarkWest Energy Partners Announces Receipt of Requisite Consents with Respect to its Tender Offer and Consent Solicitation for its 8.75% Senior Notes due 2018

DENVER—November 10, 2011—MarkWest Energy Partners, L.P. (NYSE: MWE and the “Partnership”) today announced that as of 5:00 p.m., New York City time, on November 9, 2011 (the “Consent Expiration”), it had received tenders and consents from holders of approximately 76% of the aggregate principal amount of its outstanding 8.75% senior notes due 2018 (CUSIP No. 570506AH8) (the “Notes”), in connection with its previously announced tender offer and consent solicitation for the Notes, which commenced on October 25, 2011, and is described in the Offer to Purchase and Consent Solicitation Statement dated October 25, 2011 (the “Offer to Purchase”).

The Partnership intends to execute later today a supplemental indenture (the “Supplemental Indenture”) with respect to the indenture governing the Notes, which will eliminate most of the covenants and certain default provisions applicable to the Notes. The Supplemental Indenture will not become operative until a majority in aggregate principal amount of the Notes has been purchased by the Partnership pursuant to the terms of the tender offer and the consent solicitation, which is expected to occur today.

The Partnership’s obligation to accept for purchase, and pay for, any Notes pursuant to the tender offer is subject to a number of conditions that are set forth in the Offer to Purchase, including the previously announced closing on November 3, 2011, of the Partnership’s public offering of $700,000,000 of 6.25% senior notes due 2022. Subject to the satisfaction or waiver of these conditions, later today all holders who validly tendered (and did not validly withdraw) their Notes prior to the Consent Expiration will receive total consideration equal to $1,125.00 per $1,000 principal amount of the Notes, which includes a consent payment of $30.00 per $1,000 principal amount of the Notes. Additionally, holders will receive accrued and unpaid interest on the Notes up to, but not including, the payment date for such Notes.

Holders who tender their Notes after the Consent Expiration and prior to the expiration of the tender offer, will be entitled to receive consideration equal to $1,095.00 per $1,000 principal amount of the Notes, plus any accrued and unpaid interest on the Notes up to, but not including, the payment date for such Notes accepted for purchase. Holders of Notes tendered after the Consent Expiration will not receive a consent payment. The tender offer will expire at 11:59 p.m., New York City time, on Friday, November 25, 2011, unless extended by the Partnership in its sole discretion. As the Withdrawal Date of 5:00 p.m., New York City time, on November 9, 2011, has passed, previously tendered Notes can no longer be withdrawn, and holders who tender Notes after the Withdrawal Date will not have withdrawal rights.

1

Any Notes not tendered and purchased pursuant to the tender offer will remain outstanding and the holders will be subject to the terms of the Supplemental Indenture even though they did not consent to the amendments.

The Partnership has engaged Barclays Capital Inc. as exclusive Dealer Manager for the tender offer. Persons with questions regarding the tender offer should contact Barclays Capital Inc. at (800) 438-3242 (toll free) or (212) 528-7581 (collect). Requests for copies of the Offer to Purchase or other tender offer materials may be directed to D. F. King & Co., Inc., the Information Agent, at (800) 431-9643 (toll free) or (212) 269-5550 (collect).

This press release does not constitute an offer to purchase the Notes or a solicitation of consents to amend the related indenture. The tender offer is made solely pursuant to the Offer to Purchase. The tender offer is not being made to holders of Notes in any jurisdiction in which the making or acceptance thereof would not be in compliance with the securities, blue sky or other laws of such jurisdiction.

###

MarkWest Energy Partners, L.P. is a master limited partnership engaged in the gathering, transportation, and processing of natural gas; the transportation, fractionation, marketing, and storage of natural gas liquids; and the gathering and transportation of crude oil. MarkWest has extensive natural gas gathering, processing, and transmission operations in the southwest, Gulf Coast, and northeast regions of the United States, including the Marcellus Shale, and is the largest natural gas processor and fractionator in the Appalachian region.

This press release includes “forward-looking statements.”  All statements other than statements of historical facts included or incorporated herein may constitute forward-looking statements. Actual results could vary significantly from those expressed or implied in such statements and are subject to a number of risks and uncertainties. Although we believe that the expectations reflected in the forward-looking statements are reasonable, we can give no assurance that such expectations will prove to be correct. The forward-looking statements involve risks and uncertainties that affect our operations, financial performance, and other factors as discussed in our filings with the Securities and Exchange Commission.  Among the factors that could cause results to differ materially are those risks discussed in the periodic reports we file with the SEC, including our Annual Report on Form 10-K for the year ended December 31, 2010, and our Quarterly Report on Form 10-Q for the quarter ended September 30, 2011. You are urged to carefully review and consider the cautionary statements and other disclosures made in those filings, specifically those under the heading “Risk Factors.”  We do not undertake any duty to update any forward-looking statement except as required by law.

2