Exhibit 10.1

SUPPORT AGREEMENT

THIS SUPPORT AGREEMENT (this “Agreement”) is dated as of August 12, 2020, by and among each stockholder of Montage Resources Corporation, a Delaware corporation (the “Company”), set forth on Schedule A hereto (each, a “Stockholder” and collectively, the “Stockholders”), and Southwestern Energy Company, a Delaware corporation (“Parent”).

W I T N E S S E T H:

WHEREAS, concurrently with the execution and delivery of this Agreement, Parent and the Company are entering into an Agreement and Plan of Merger, dated as of the date hereof (as the same may be amended or supplemented, the “Merger Agreement”), providing that, among other things, upon the terms and subject to the conditions set forth in the Merger Agreement, the Company will be merged with Parent (the “Merger”), and each outstanding share of common stock, par value $0.01 per share, of the Company (“Company Common Stock”) will be converted into the Merger Consideration;

WHEREAS, each Stockholder beneficially owns such number of shares of Company Common Stock set forth opposite such Stockholder’s name on Schedule A hereto (collectively, such shares of Company Common Stock are referred to herein as the “Subject Shares”); and

WHEREAS, as a condition and inducement to Parent to enter into the Merger Agreement, Parent has required that the Stockholders enter into this Agreement.

NOW, THEREFORE, to induce Parent to enter into, and in consideration of its entering into, the Merger Agreement, and in consideration of the promises and the representations, warranties and agreements contained herein and therein, the parties, intending to be legally bound hereby, agree as follows:

1.    Representations and Warranties of each Stockholder. Each Stockholder hereby represents and warrants to Parent, severally and not jointly, as of the date hereof as follows:

(a)    Due Organization. Such Stockholder is an entity duly formed under the laws of its jurisdiction of formation and is validly existing and in good standing under the laws thereof.

(b)    Authority; No Violation. Such Stockholder has full organizational power and authority to execute and deliver this Agreement and to perform its obligations hereunder. The execution and delivery of this Agreement and the performance of its obligations hereunder have been duly and validly approved by the governing authority of such Stockholder and no other organizational proceedings on the part of such Stockholder are necessary to approve this Agreement and to perform its obligations hereunder. This Agreement has been duly and validly executed and delivered by such Stockholder and (assuming due authorization, execution and delivery by Parent) this Agreement constitutes a valid and binding obligation of such Stockholder, enforceable against such Stockholder in accordance with its terms, except that such enforceability (i) may be limited by bankruptcy, insolvency, moratorium or other similar laws affecting or relating to the enforcement of creditors’ rights generally and (ii) is subject to general principles of equity and the discretion of the court before which any proceedings seeking injunctive relief or specific performance may be brought. Neither the execution and delivery of this Agreement by such Stockholder, nor the consummation by such Stockholder of the transactions contemplated hereby, nor compliance by such Stockholder with any of the terms or provisions hereof, will (x) violate any provision of the governing documents of such Stockholder, (y) violate any statute, code, ordinance, rule, regulation, judgment, order, writ, decree or injunction applicable to such Stockholder, or any of its properties or assets, or (z) violate, conflict with, result in a breach of any provision of or the loss of any benefit under, constitute a default (or an event which, with notice or lapse of time, or both, would constitute a default) under, result in the termination of or a right of termination or cancellation under, accelerate the performance required by, or result in the creation of any lien, claim, mortgage, encumbrance, pledge, deed of trust, security interest, equity or charge of any kind (each, a “Lien”) upon any of the Subject Shares pursuant to any of the terms, conditions or provisions of any note, bond, mortgage, indenture, deed of trust, license, lease, agreement or other instrument or obligation to which such Stockholder is a party, or by which it or any of its properties or assets may be bound or affected, except, in the case of this clause (z), for such matters that would not, individually or in the aggregate, impair the ability of such Stockholder to perform its obligations under this Agreement.

(c)    The Subject Shares. As of the date of this Agreement, such Stockholder is the beneficial owner of and, together with the applicable controlling entity or entities of such Stockholder set forth on Schedule A hereto (as applicable, the “Controlling Entities”), has the sole right to vote and dispose of the Subject Shares set forth opposite such Stockholder’s name on Schedule A hereto, free and clear of any Liens whatsoever, except for any Liens which arise hereunder, in each case except as disclosed in any Schedule 13D filed by such Stockholder prior to the date hereof. None of the Subject Shares is subject to any voting trust or other similar agreement, arrangement or restriction, except as contemplated by this Agreement. Without limiting the generality of

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the foregoing, (i) there are no agreements or arrangements of any kind, contingent or otherwise, obligating such Stockholder to sell, transfer (including by tendering into any tender or exchange offer), assign, grant a participation interest in, option, pledge, hypothecate or otherwise dispose of or encumber, including by operation of law or otherwise (each, a “Transfer”), or cause to be Transferred, any of the Subject Shares, other than a Transfer, such as a hedging or derivative transaction, with respect to which such Stockholder (and/or its Controlling Entities) retains its Subject Shares and the sole right to vote, dispose of and exercise dissenters’ rights with respect to its Subject Shares during the Applicable Period, and (ii) no Person has any contractual or other right or obligation to purchase or otherwise acquire any of the Subject Shares. Other than the Subject Shares, such Stockholder does not own any equity interests or other equity-based securities in the Company or any of its Subsidiaries.

(d)    Absence of Litigation. There is no litigation, suit, claim, action, proceeding or investigation pending, or to the knowledge of such Stockholder, threatened against such Stockholder, or any property or asset of such Stockholder, before any Governmental Entity that seeks to delay or prevent the consummation of the transactions contemplated by this Agreement.

(e)    No Consents Required. No consent of, or registration, declaration or filing with, any Person or Governmental Entity is required to be obtained or made by or with respect to such Stockholder in connection with the execution, delivery and performance of this Agreement and except for any applicable requirements and filings with the SEC, if any, under the Exchange Act and except where the failure to obtain such consents, approvals, authorizations or permits, or to make such filings or notifications, would not prevent or delay the performance by such Stockholder of such Stockholder’s obligations under this Agreement in any material respect.

(f)    Reliance. Such Stockholder understands and acknowledges that Parent is entering into the Merger Agreement in reliance upon such Stockholder’s execution and delivery of this Agreement.

(g)    Stockholder Has Adequate Information. Such Stockholder is a sophisticated seller with respect to the Subject Shares and has adequate information concerning the business and financial condition of Parent to make an informed decision regarding the Merger and the transactions contemplated thereby and has independently and without reliance upon Parent and based on such information as such Stockholder has deemed appropriate, made its own analysis and decision to enter into this Agreement. Such Stockholder acknowledges that Parent has not made and does not make any

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representation or warranty, whether express or implied, of any kind or character except as expressly set forth in the Merger Agreement and this Agreement. Notwithstanding the foregoing, and for the elimination of doubt, Stockholder is not waiving and is expressly preserving any claims that might arise in connection with the Registration Statement contemplated to be filed in connection with the Merger.

2.    Representations and Warranties of Parent. Parent hereby represents and warrants to each Stockholder as of the date hereof as follows:

(a)    Due Organization. Parent is a corporation duly incorporated under the laws of the State of Delaware and is validly existing and in good standing under the laws thereof.

(b)    Authority; No Violation. Parent has full corporate power and authority to execute and deliver this Agreement. The execution and delivery of this Agreement have been duly and validly approved by the Board of Directors of Parent and no other corporate proceedings on the part of Parent are necessary to approve this Agreement. This Agreement has been duly and validly executed and delivered by Parent and (assuming due authorization, execution and delivery by the Stockholder) this Agreement constitutes a valid and binding obligation of Parent, enforceable against Parent in accordance with its terms except that such enforceability (i) may be limited by bankruptcy, insolvency, moratorium or other similar laws affecting or relating to the enforcement of creditors’ rights generally and (ii) is subject to general principles of equity and the discretion of the court before which any proceedings seeking injunctive relief or specific performance may be brought. Neither the execution and delivery of this Agreement by Parent, nor the consummation by Parent of the transactions contemplated hereby, nor compliance by Parent with any of the terms or provisions hereof, will (x) violate any provision of the governing documents of Parent or the certificate of incorporation, bylaws or similar governing documents of any of Parent’s Subsidiaries, (y) violate any statute, code, ordinance, rule, regulation, judgment, order, writ, decree or injunction applicable to the Parent or any of Parent’s Subsidiaries, or any of their respective properties or assets, or (z) violate, conflict with, result in a breach of any provision of or the loss of any benefit under, constitute a default (or an event which, with notice or lapse of time, or both, would constitute a default) under, result in the termination of or a right of termination or cancellation under, accelerate the performance required by, or result in the creation of any Lien upon any of the respective properties or assets of Parent or any of Parent’s Subsidiaries under, any of the terms, conditions or provisions of any note, bond, mortgage, indenture, deed of trust, license, lease, agreement or other instrument or obligation to which Parent or any of Parent’s Subsidiaries is a party, or by which they or any of their respective properties or assets may be bound or affected.

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3.    Covenants of Each Stockholder. Each Stockholder, severally and not jointly, agrees as follows; provided that all of the following covenants shall apply solely to actions taken by such Stockholder in its capacity as a stockholder of the Company:

(a)    Agreement to Vote Subject Shares. During the Applicable Period (as defined below), at any meeting of the stockholders of the Company, however called, or at any postponement or adjournment thereof, or in any other circumstance upon which a vote or other approval of all or some of the stockholders of the Company is sought, such Stockholder shall, and shall cause any holder of record of its Subject Shares on any applicable record date to, vote: (i) in favor of adoption of the Merger Agreement and approval of any other matter that is required to be approved by the stockholders of the Company in order to effect the Merger; (ii) against any merger agreement or merger (other than the Merger Agreement and the Merger), consolidation, combination, sale or transfer of a material amount of assets, reorganization, recapitalization, dissolution, liquidation or winding up of or by the Company or any of its Subsidiaries that is prohibited by the Merger Agreement, unless such transaction is approved in writing by Parent, or any Alternative Proposal, and (iii) against any amendment of the Company’s certificate of incorporation or bylaws or other proposal or transaction involving the Company or any of its Subsidiaries, which amendment or other proposal or transaction would in any manner delay, impede, frustrate, prevent or nullify the Merger, the Merger Agreement or any of the transactions contemplated by the Merger Agreement or change in any manner the voting rights of any outstanding class of capital stock of the Company. During the Applicable Period, such Stockholder (and/or its Controlling Entities) shall retain at all times the right to vote all of its Subject Shares in such Stockholder’s sole discretion and without any other limitation on those matters other than those set forth in this Section 3(a) that are at any time or from time to time presented for consideration to the Company’s stockholders generally. During the Applicable Period, in the event that any meeting of the stockholders of the Company is held, such Stockholder shall (or shall cause the holder of record on any applicable record date to) appear at such meeting or otherwise cause all of its Subject Shares to be counted as present thereat for purposes of establishing a quorum. During the Applicable Period, such Stockholder further agrees not to commit or agree, and to cause any record holder of its Subject Shares not to commit or agree, to take any action inconsistent with the foregoing during the Applicable Period. “Applicable Period” means the period from and including the date of this Agreement to and including the date of the termination of this Agreement.

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(b)    No Transfers. Except as provided in the last sentence of this Section 3(b), such Stockholder agrees not to, and to cause any record holder of its Subject Shares, not to, in any such case directly or indirectly, during the Applicable Period (i) Transfer or enter into any agreement, option or other arrangement (including any profit sharing arrangement) with respect to the Transfer of, any of its Subject Shares (or any interest therein) to any Person, other than the exchange of its Subject Shares for Merger Consideration in accordance with the Merger Agreement or (ii) grant any proxies, or deposit any of its Subject Shares into any voting trust or enter into any voting arrangement, whether by proxy, voting agreement or otherwise, with respect to its Subject Shares, other than pursuant to this Agreement. Subject to the last sentence of this Section 3(b), such Stockholder further agrees not to commit or agree to take, and to cause any record holder of any of its Subject Shares not to commit or agree to take, any of the foregoing actions during the Applicable Period. Notwithstanding the foregoing, such Stockholder shall have the right to (a) Transfer its Subject Shares to an Affiliate if and only if such Affiliate shall have agreed in writing, in a manner acceptable in form and substance to Parent, (i) to accept such Subject Shares subject to the terms and conditions of this Agreement, and (ii) to be bound by this Agreement as if it were “the Stockholder” for all purposes of this Agreement; provided, however, that no such transfer shall relieve such Stockholder from its obligations under this Agreement with respect to any Subject Shares or (b) Transfer its Subject Shares in a transaction, such as a hedging or derivative transaction, with respect to which such Stockholder retains the sole right to vote its Subject Shares during the Applicable Period; provided that no such transaction shall (x) in any way limit any of the obligations of such Stockholder under this Agreement, or (y) have any adverse effect on the ability of the Stockholder to perform its obligations under this Agreement.

(c)    Reserved.

(d)    Adjustment to Subject Shares. In case of a stock dividend or distribution, or any change in the Company Common Stock by reason of any stock dividend or distribution, split-up, recapitalization, combination, exchange of shares or the like, the term “Subject Shares” shall be deemed to refer to and include the Subject Shares as well as all such stock dividends and distributions and any securities into which or for which any or all of the Subject Shares may be changed or exchanged or which are received in such transaction.

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(e)    Non-Solicitation. Except to the extent that the Company or the Company Board is permitted to do so under the Merger Agreement, but subject to any limitations imposed on the Company or the Company Board under the Merger Agreement, such Stockholder agrees, solely in its capacity as a stockholder of the Company, that it shall not, and shall cause its Affiliates and its and their respective agents and representatives not to, directly or indirectly, (i) initiate, solicit, knowingly encourage or knowingly facilitate (including by way of furnishing information) any Alternative Proposal, (ii) participate or engage in any discussions or negotiations with, or disclose any non-public information or data relating to the Company or any of its Subsidiaries to any Person that has made an Alternative Proposal, (iii) approve, endorse or recommend (or publicly propose to approve, endorse or recommend) any Alternative Proposal or (iv) enter into any letter of intent, term sheet, memorandum of understanding, merger agreement, acquisition agreement, exchange agreement or any other agreement with respect to an Alternative Proposal. Each Stockholder will, and will cause its Affiliates and its and their respective investment bankers, attorneys, accountants and other representatives to, immediately cease and cause to be terminated any discussions or negotiations with any Person conducted heretofore with respect to any Alternative Proposal. Nothing contained in this Section 3(e) shall prevent any Person affiliated with such Stockholder who is a director or officer of the Company or designated by such Stockholder as a director of officer of the Company from taking actions in his capacity as a director or officer of the Company, including taking any actions permitted under Section 5.3 of the Merger Agreement.

4.    Assignment; No Third-Party Beneficiaries. Except as provided herein, neither this Agreement nor any of the rights, interests or obligations hereunder shall be assigned by any of the parties without the prior written consent of the other parties hereto, except that Parent may assign, it its sole discretion, any or all of its rights, interest and obligations hereunder to any direct or indirect wholly owned Subsidiary of Parent. Subject to the preceding sentence, this Agreement will be binding upon, inure to the benefit of and be enforceable by the parties hereto and their respective successors and assigns. Except as otherwise expressly provided herein, this Agreement (including the documents and instruments referred to herein) is not intended to confer upon any Person other than the parties hereto any rights or remedies hereunder; provided, however, that the Company is an intended third-party beneficiary of the agreement of the Stockholders set forth in Section 3(c) hereof.

5.    Termination. This Agreement and the covenants and agreements set forth in this Agreement shall automatically terminate (without any further action of the parties) upon the earliest to occur of: (a) the termination of the Merger Agreement in accordance with its terms; (b) the Effective Time; (c) the date of any modification, waiver or amendment to the Merger Agreement effected without such Stockholder’s consent that (y) decreases the amount or changes the form of consideration payable to all of the stockholders of the Company pursuant to the terms of the Merger Agreement as in effect on the date of this Agreement or (z) otherwise materially

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adversely affects the interests of such Stockholder; (d) the mutual written consent of the parties hereto; and (e) the Termination Date. In the event of termination of this Agreement pursuant to this Section 5, this Agreement shall become void and of no effect with no liability on the part of any party; provided, however, that no such termination shall relieve any party from liability for any breach hereof prior to such termination.

6.    General Provisions.

(a)    Amendments. This Agreement may not be amended except by an instrument in writing signed on behalf of each of the parties hereto.

(b)    Notice. All notices and other communications hereunder shall be in writing and shall be deemed given if delivered personally, email (upon receipt), telecopied (which is confirmed) or sent by overnight courier (providing proof of delivery) at the following addresses (or at such other address for a party as specified by like notice; provided that notices of a change of address will be effective only upon receipt thereof):

(i)    If to the Stockholders, to:

EnCap Investments L.P.

1100 Louisiana, Suite 4900

Houston, Texas 77002

Facsimile: (713) 659-6130

Attention:    Doug Swanson; Mark Burroughs, Jr.

Email:          dswanson@encapinvestments.com;

                     mburroughs@encapinvestments.com

With copies (which shall not constitute notice) to:

Vinson & Elkins LLP

1001 Fannin, Suite 2500

Houston, Texas 77002

Attention:    W. Matthew Strock; Stephen M. Gill

Facsimile:    (713) 615-5650; (713) 615-5956

Email:          mstrock@velaw.com; sgill@velaw.com

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(ii)    If to Parent, to:

Southwestern Energy Company

10000 Energy Drive

Spring, TX 77389

Attention: General Counsel

With copies (which shall not constitute notice) to:

Skadden, Arps, Slate, Meagher & Flom LLP

1000 Louisiana St., Suite 6800

Houston, TX 77002

Attention:    Frank E. Bayouth

                    Eric C. Otness

Facsimile: (713) 655-5200

(c)    Interpretation. When a reference is made in this Agreement to a Section, such reference shall be to a Section to this Agreement unless otherwise indicated. The headings contained in this Agreement are for reference purposes only and shall not affect in any way the meaning or interpretation of this Agreement. Wherever the words “include,” “includes” or “including” are used in this Agreement, they shall be deemed to be followed by the words “without limitation.” The phrases “the date of this Agreement,” “the date hereof” and terms of similar import, unless the context otherwise requires, shall be deemed to refer to August 12, 2020.

(d)    Counterparts. This Agreement may be executed in counterparts, all of which shall be considered one and the same agreement and shall become effective when counterparts have been signed by each of the parties hereto and delivered to the other parties hereto, it being understood that all parties hereto need not sign the same counterpart.

(e)    Entire Agreement. This Agreement (including the documents and the instruments referred to herein) constitutes the entire agreement and supersedes all prior agreements and understandings, both written and oral, among the parties hereto with respect to the subject matter hereof.

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(f)    Governing Law. This Agreement shall be governed by, and construed in accordance with, the laws of the State of Delaware regardless of the laws that might otherwise govern under applicable principles of conflicts of law thereof or of any other jurisdiction.

(g)    Severability. If any term, provision, covenant or restriction herein, or the application thereof to any circumstance, shall, to any extent, be held by a court of competent jurisdiction to be invalid, void or unenforceable, the remainder of the terms, provisions, covenants and restrictions herein and the application thereof to any other circumstances, shall remain in full force and effect, shall not in any way be affected, impaired or invalidated, and shall be enforced to the fullest extent permitted by law, and the parties hereto shall reasonably negotiate in good faith a substitute term or provision that comes as close as possible to the invalidated and unenforceable term or provision, and that puts each party hereto in a position as nearly comparable as possible to the position each such party would have been in but for the finding of invalidity or unenforceability, while remaining valid and enforceable.

(h)    Waiver. Any provisions of this Agreement may be waived at any time by the party that is entitled to the benefits thereof. Any agreement on the part of a party hereto to any such extension or waiver shall be valid only if set forth in a written instrument signed on behalf of such party, but such extension or waiver or failure to insist on strict compliance with an obligation, covenant, agreement or condition shall not operate as a waiver of, or estoppel with respect to, any subsequent or other failure.

(i)    Further Assurances. Each Stockholder will, from time to time, (i) at the request of Parent take, or cause to be taken, all actions, and do, or cause to be done, and assist and cooperate with the other parties hereto in doing, all things reasonably necessary, proper or advisable to carry out the intent and purposes of this Agreement and (ii) execute and deliver, or cause to be executed and delivered, such additional or further consents, documents and other instruments as Parent may reasonably request for the purpose of effectively carrying out the intent and purposes of this Agreement.

(j)    Publicity. Except as otherwise required by law (including securities laws and regulations) and the regulations of any national stock exchange, so long as this Agreement is in effect, the Stockholder shall not issue or cause the publication of any press release or other public announcement with respect to, or otherwise make any public statement concerning, the transactions contemplated by this Agreement or the Merger Agreement, without the consent of Parent, which consent shall not be unreasonably withheld.

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(k)    Capitalized Terms. Capitalized terms used but not defined herein shall have the meanings set forth in the Merger Agreement. Notwithstanding the foregoing, the term “Affiliate” as used in Section 3(e) of this Agreement shall not include any portfolio company of EnCap Investments L.P. or its affiliated investment funds, other than the Company and its Subsidiaries, and except for any portfolio company taking any action that would otherwise be prohibited by Section 3(e) at the direction or encouragement of any Stockholder or Controlling Entity.

7.    Stockholder Capacity. Each Stockholder signs solely in its capacity as the beneficial owner of its Subject Shares and nothing contained herein shall limit or affect any actions taken by any officer, director, partner, Affiliate or representative of such Stockholder who is or becomes an officer or a director of the Company in his or her capacity as an officer or director of the Company, and none of such actions in such capacity shall be deemed to constitute a breach of this Agreement. Each Stockholder signs individually solely on behalf of itself and not on behalf of any other Stockholder.

8.    Enforcement. The parties hereto agree that irreparable damage would occur in the event that any of the provisions of this Agreement were not performed in accordance with their specific terms or were otherwise breached and that money damages would not be a sufficient remedy of any such breach. It is accordingly agreed that, in addition to any other remedy to which they are entitled at law or in equity, the parties hereto shall be entitled to specific performance and injunctive or other equitable relief, without the necessity of proving the inadequacy of money damages. Notwithstanding the foregoing, Parent agrees that with respect to any damage claim that might be brought against any Stockholder, any of its Affiliates under this Agreement, and without regard to whether such claim sounds in contract, tort or any other legal or equitable theory of relief, that damages are limited to actual damages and expressly waive any right to recover special damages, including, without limitation, lost profits as well as any punitive or exemplary damages. In the event of any litigation over the terms of this Agreement, the prevailing party in any such litigation shall be entitled to reasonable attorneys’ fees and costs incurred in connection with such litigation. The parties hereto further agree that any action or proceeding relating to this Agreement or the transactions contemplated hereby shall be brought and determined in the Court of Chancery of the State of Delaware (or, if the Court of Chancery of the State of Delaware declines to accept jurisdiction over a particular matter, the Superior Court of the State of Delaware (Complex Commercial Division) or, if subject matter jurisdiction over the matter that is the subject of the action or proceeding is vested exclusively in the federal courts of the United States of America, the federal court of the United States of America sitting in the district of Delaware) and any appellate court from any thereof. In addition, each of the parties hereto (a) consents that each party hereto irrevocably submits to the exclusive jurisdiction and venue of such courts listed in this Section 8 in the event any dispute

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arises out of this Agreement or any of the transactions contemplated hereby, (b) agrees that each party hereto irrevocably waives the defense of an inconvenient forum and all other defenses to venue in any such court in any such action or proceeding, and (c) waives any right to trial by jury with respect to any claim or proceeding related to or arising out of this Agreement or any of the transactions contemplated hereby. EACH PARTY HERETO HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVES ANY RIGHT IT MAY HAVE TO A TRIAL BY JURY IN RESPECT OF ANY LITIGATION OR PROCEEDING DIRECTLY OR INDIRECTLY ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY. EACH PARTY HERETO CERTIFIES AND ACKNOWLEDGES THAT (I) NO REPRESENTATIVE, AGENT OR ATTORNEY OF ANY OTHER PARTY HAS REPRESENTED, EXPRESSLY OR OTHERWISE, THAT SUCH OTHER PARTY WOULD NOT, IN THE EVENT OF LITIGATION, SEEK TO ENFORCE ANY OF SUCH WAIVER, (II) IT UNDERSTANDS AND HAS CONSIDERED THE IMPLICATIONS OF SUCH WAIVER, (III) IT MAKES SUCH WAIVER VOLUNTARILY, AND (IV) IT HAS BEEN INDUCED TO ENTER INTO THIS AGREEMENT BY, AMONG OTHER THINGS, THE MUTUAL WAIVERS AND CERTIFICATIONS IN THIS SECTION 8.

9.    No Ownership Interest. Nothing contained in this Agreement shall be deemed to vest in Parent or any other Person any direct or indirect ownership or incidence of ownership of, or with respect to, any Subject Shares. Subject to the restrictions and requirements set forth in this Agreement, all rights, ownership and economic benefits of and relating to the Subject Shares shall remain vested in and belong to each Stockholder, and this Agreement shall not confer any right, power or authority upon Parent or any other Person to direct the Stockholder in the voting of any of the Subject Shares (except as otherwise specifically provided for herein).

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IN WITNESS WHEREOF, this Agreement has been executed and delivered as of the date first written above.

SOUTHWESTERN ENERGY COMPANY
By:	/s/ Bill Way
Name:	Bill Way
Title:	President & Chief Executive Officer

[Signature Page to Project Mercury Support Agreement]

ENCAP ENERGY CAPITAL FUND VIII CO-INVESTORS, L.P.

By:	EnCap Equity Fund VIII GP, L.P.,
	its general partner
By:	EnCap Investments L.P.,
	its general partner
By:	EnCap Investments GP, L.L.C.,
	its general partner
By:	/s/ Douglas E. Swanson, Jr.
Name:	Douglas E. Swanson, Jr.
Title:	Managing Director

ENCAP ENERGY CAPITAL FUND VIII, L.P.
By:	EnCap Equity Fund VIII GP, L.P.,
	its general partner
By:	EnCap Investments L.P.,
	its general partner
By:	EnCap Investments GP, L.L.C.,
	its general partner
By:	/s/ Douglas E. Swanson, Jr.
Name:	Douglas E. Swanson, Jr.
Title:	Managing Director

ENCAP ENERGY CAPITAL FUND IX, L.P.
By:	EnCap Equity Fund IX GP, L.P.,
	its general partner
By:	EnCap Investments L.P.,
	its general partner
By:	EnCap Investments GP, L.L.C.,
	Its general partner
By:	/s/ Douglas E. Swanson, Jr.
Name:	Douglas E. Swanson, Jr.
Title:	Managing Director

TPR RESIDUAL ASSETS, LLC
By:	Excalibur Resources Holdings, LLC,
	its sole member
By:	EnCap Energy Capital Fund IX, L.P.,
	its sole member
By:	EnCap Equity Fund IX GP, L.P.,
	its general partner
By:	EnCap Investments L.P.,
	its general partner
By:	EnCap Investments GP, L.L.C.,
	its general partner
By:	/s/ Douglas E. Swanson, Jr.
Name:	Douglas E. Swanson, Jr.
Title:	Managing Director

[Signature Page to Project Mercury Support Agreement]

Schedule A

Name of Stockholder	No. Shares of Company Common Stock
EnCap Energy Capital Fund VIII Co-Investors, L.P.(1)		2,694,673
EnCap Energy Capital Fund VIII, L.P.(1)		3,979,173
EnCap Energy Capital Fund IX, L.P.(1)		4,856,485
TPR Residual Assets, LLC(2)		2,521,573

(1) EnCap Energy Capital Fund VIII, L.P., a Texas limited partnership (“EnCap Fund VIII”), EnCap Energy Capital Fund IX, L.P., a Texas limited partnership (“EnCap Fund IX”), EnCap Energy Capital Fund VIII Co-Investors, L.P., a Texas limited partnership (“EnCap Fund VIII Co-Invest” and together with EnCap Fund VIII and EnCap Fund IX, the “EnCap Funds”), collectively directly hold the remaining shares of common stock. EnCap Partners GP, LLC (“EnCap Partners GP”) is the sole general partner of EnCap Partners, LP (“EnCap Partners”), which is the managing member of EnCap Investments Holdings, LLC (“EnCap Holdings”), which is the sole member of EnCap Investments Holdings Blocker, LLC (“EnCap Holdings Blocker”). EnCap Holdings Blocker is the sole member of EnCap Investments GP, L.L.C. (“EnCap Investments GP”), which is the sole general partner of EnCap Investments L.P. (“EnCap Investments LP”). EnCap Investments LP is the sole general partner of EnCap Equity Fund VIII GP, L.P. (“EnCap Fund VIII GP”) and EnCap Equity Fund IX GP, L.P. (“EnCap Fund IX GP”). EnCap Fund VIII GP is the sole general partner of each of EnCap Fund VIII and EnCap Fund VIII Co-Invest. EnCap Fund IX GP is the sole general partner of EnCap Fund IX. Therefore, EnCap Partners GP may be deemed to share the right to direct the voting and disposition of the Subject Shares held by the EnCap Funds.

(2) TPR Residual Assets, LLC (“TPR Residual”) is member-managed by EnCap Fund IX. As a result, EnCap Fund IX may be deemed to have the power to vote or direct the vote or to dispose or direct the disposition of the shares owned by TPR Residual.

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