FIRST SUPPLEMENTAL INDENTURE

Exhibit 4.2

Execution Version

MARINER ENERGY, INC,

as Issuer

THE GUARANTORS

FIRST SUPPLEMENTAL INDENTURE

Dated as of June 10, 2009

WELLS FARGO BANK, N.A.,

as Trustee

11 ³ / 4 % Senior Notes due 2016

TABLE OF CONTENTS

FIRST SUPPLEMENTAL INDENTURE

      THIS FIRST SUPPLEMENTAL INDENTURE , dated as of June 10, 2009 (this “ Supplemental Indenture ”), is entered into between MARINER ENERGY, INC., a Delaware corporation (the “ Company ”), the GUARANTORS (as defined herein) and WELLS FARGO BANK, N.A., a New York State banking association, as trustee (the “ Trustee ”). Capitalized terms used herein and not otherwise defined have the meanings set forth in the Base Indenture (as defined below).

RECITALS

      WHEREAS , the Company, the Guarantors and the Trustee have entered into that certain Indenture, dated as of June 10, 2009 (the “ Base Indenture ”), pursuant to which the Company may from time to time issue its senior indebtedness in the form of one or more series of debentures, notes, bonds or other evidences of indebtedness (collectively, the “ Securities ”).

      WHEREAS , Section 9.1 of the Base Indenture provides that the Company, the Guarantors and the Trustee may, without notice to or consent of the Holders of the Securities, enter into a supplemental Indenture (i) in accordance with clause (8) thereof, to establish the form or terms of Securities of any series as permitted by Section 2.1 of the Base Indenture or (ii) in accordance with clause (7) thereof, to change or eliminate any of the provisions of the Base Indenture in respect of a series of Securities so long as any such change or elimination shall become effective only when there is no Security of any series created prior to the execution of such supplemental indenture that is adversely affected in any material respect by such change in or elimination of such provision; and

      WHEREAS , the Company has duly authorized the issue of a new series of Securities designated as the 11 ³ / 4 % Senior Notes due 2016 (as they may be issued from time to time under this Supplemental Indenture, including any Additional Notes issued pursuant to Section 2.1 of the Base Indenture and Section 1.03 of this Supplemental Indenture, the “ Notes ”), initially in an aggregate principal amount not to exceed $300,000,000 and, in connection therewith, the Company has duly determined to make, execute and deliver this Supplemental Indenture to establish the form and set forth the terms of the Notes in accordance with the Base Indenture and to change and eliminate certain provisions of the Base Indenture in respect of the Notes; and

      WHEREAS , the Company proposes that its obligations under such new series of Securities and under the Indenture to the extent applicable to such new series of Securities be guaranteed by each of the Guarantors in accordance with the provisions of the Indenture (including Article X of the Base Indenture and the provisions of this Supplemental Indenture); and

      WHEREAS , the Company and the Guarantors have determined that this Supplemental Indenture is authorized or permitted by Section 9.1 of the Base Indenture and have delivered to the Trustee an Opinion of Counsel and Officers’ Certificate to the effect that all conditions precedent provided for in the Base Indenture to the execution and delivery of this Supplemental Indenture have been complied with; and

      WHEREAS , the Form of Note, the Trustee’s Certificate of Authentication to be borne by each Note, the Form of Option of Holder to Elect Purchase, the Form of Schedule of Increases or Decreases in Global Note and the Form of Assignment and Transfer to be borne by the Notes are to be substantially in the forms hereinafter provided for; and

      WHEREAS , all things necessary to make the Notes and the Guarantees thereof of the Guarantors, when the Notes have been executed by the Company and authenticated and delivered by the Trustee or a duly authorized authenticating agent, as in the Base Indenture provided, the valid and legally binding obligations of the Company and the Guarantors, respectively, have been done; and

      WHEREAS , all things necessary to make this Supplemental Indenture a valid and legally binding agreement according to its terms, and a valid and legally binding amendment of, and supplement to, the Base Indenture, have been done.

      NOW, THEREFORE , in consideration of the mutual agreements and covenants set forth herein, the parties hereto agree, subject to the terms and conditions hereinafter set forth, as follows for the benefit of the Trustee and the Holders:

ARTICLE 1

ISSUE AND DESCRIPTION OF NOTES

     Section 1.01 Designation and Amount; Payments; Denomination . The Notes shall be designated as the “11 ³ / 4 % Senior Notes due 2016.” The Notes are hereby established as a series of Securities under the Base Indenture. The aggregate principal amount of Notes that may be authenticated and delivered under this Supplemental Indenture is not limited. The aggregate principal amount of Notes initially authorized for authentication and delivery pursuant to this Supplemental Indenture (the “ Initial Notes ”) is limited to $300,000,000 (except for Notes authenticated and delivered upon registration or transfer of, or in exchange for, or in lieu of other Notes pursuant to Section 1.04(d) , Section 3.08, Section 4.07 , Section 4.09 and Section 9.05 hereof and Section 2.8, Section 2.9, Section 2.10, Section 2.13, Section 2.16, Section 5.7 and Section 9.5 of the Base Indenture). The Company may, and shall be entitled to, from time to time, without notice to or the consent of the Holders of the Notes and without any further supplement or amendment to the Base Indenture or this Supplemental Indenture, in accordance with and subject to the conditions specified in, Section 1.03 below, increase the principal amount of Notes and issue such increased principal amount (or any portion thereof) of Notes as “ Additional Notes ” under this Supplemental Indenture.

     Payment of the principal of and interest on the Notes shall be made in Dollars, and the Notes shall be denominated in Dollars and in amounts equal to either $2,000 or an integral multiple of $1,000 in excess thereof.

     If a Holder has given wire transfer instructions to the Company, the Company will, or if the Company is not then the Paying Agent, the Company will cause the Paying Agent to, pay all principal, interest and premium, if any, on that Holder’s Notes in accordance with the instructions; all other payments of the principal of (and premium, if any) and interest on the Notes shall be payable at the office or agency of the Company maintained for such purpose in The City of New York, or at such other office or agency of the Company as may be maintained for such purpose pursuant to Section 2.5 of the Base Indenture; provided, however , that, at the option of the Company, each installment of interest may be paid by check mailed to addresses of the Persons entitled thereto as such addresses shall appear on the Note Register. Payments in respect of Notes represented by a Global Note (including principal, premium and interest) will be made by wire transfer of immediately available funds to the accounts specified by DTC or its nominee.

     Initially, Wells Fargo Bank, N.A. will act as Paying Agent and Registrar with respect to the Notes. The Company may appoint and change any Paying Agent or Registrar without notice.

     The Notes shall be guaranteed by Guarantees of each of the Guarantors as set forth in Article 10 hereof. Article X of the Base Indenture (as amended and supplemented by this Supplemental Indenture, including Article 10 hereof) shall apply to the Notes.

     Provisions of the Base Indenture to the extent related to Additional Amounts (as defined therein) shall not apply to the Notes.

     Section 1.02 Form of Notes . The Notes shall be substantially in the form set forth in Exhibit A hereto, which is incorporated in and made a part of this Supplemental Indenture.

     The Notes shall not bear, and the Note Guarantees thereof by any Guarantor shall be valid and enforceable notwithstanding the absence on the Notes of, any Notation of Guarantee by such Guarantor.

     Any of the Notes may have such letters, numbers or other marks of identification and, in addition to those set forth on Exhibit A and in Section 1.05(b) , such notations, legends or endorsements as the officers executing the same may approve (execution thereof to be conclusive evidence of such approval) and as are not inconsistent with the provisions of this Supplemental Indenture or the Base Indenture or as may be required to comply with any law or with any rule or regulation made pursuant thereto or with any rule or regulation of any securities exchange or automated quotation system on which the Notes may be listed or designated for issuance, or to conform to usage or to indicate any special limitations or restrictions to which any particular Notes are subject.

     The terms and provisions contained in the form of Note attached as Exhibit A hereto shall constitute, and are hereby expressly made, a part of the Indenture and, to the extent applicable, the Company, the Guarantors and the Trustee, by their execution and delivery of this Supplemental Indenture, expressly agree to such terms and provisions and to be bound thereby.

     Section 1.03 Additional Notes .

     (a) With respect to any Additional Notes, there shall be (a) established in or pursuant to a Board Resolution and (b) (i) set forth or determined in the manner provided in an Officers’ Certificate or (ii) established in one or more indentures supplemental to this Supplemental Indenture, prior to the issuance of such Additional Notes:

     (1) the aggregate principal amount of such Additional Notes to be authenticated and delivered pursuant to this Supplemental Indenture;

     (2) the issue price and the issue date of such Additional Notes, including the date from which interest shall accrue and the first interest payment date therefor; and

     (3) if applicable, that such Additional Notes shall be issuable in whole or in part in the form of one or more Global Securities and, in such case, the respective depositaries for such Global Securities, the form of any legend or legends which shall be borne by such Global Securities in addition to or in lieu of those set forth in Exhibit A hereto and any circumstances in addition to or in lieu of those set forth in Exhibit A in which any such Global Securities

may be exchanged in whole or in part for Additional Notes registered, or any transfer of such Global Security in whole or in part may be registered, in the name or names of Persons other than the depositary for such Global Note or a nominee thereof.

     (b) If any of the terms of any Additional Notes are established by action taken pursuant to a Board Resolution, a copy thereof shall be delivered to the Trustee at or prior to the delivery of the Officers’ Certificate or the indenture supplemental to this Supplemental Indenture setting forth the terms of the Additional Notes.

     (c) The Initial Notes and any Additional Notes shall be considered collectively as a single class for all purposes of the Indenture. Holders of the Initial Notes and any Additional Notes will vote and consent together on all matters to which such Holders are entitled to vote or consent as one class, and none of the Holders of the Initial Notes or any Additional Notes shall have the right to vote or consent as a separate class on any matter to which such Holders are entitled to vote or consent.

     Section 1.04 Execution and Authentication .

     (a) The Initial Notes may forthwith be executed by the Company and, together with a Company Order for authentication and delivery thereof, delivered to the Trustee for authentication and delivery by the Trustee for original issue in accordance with the provisions of Section 2.4 of the Base Indenture.

     (b) At any time and from time to time after the issuance of the Initial Notes, the Trustee shall authenticate and deliver any Additional Notes for original issue in accordance with the provisions of Section 2.4 of the Base Indenture in an aggregate principal amount determined at the time of issuance and specified in a Company Order. Such Company Order shall specify the principal amount of the Additional Notes to be authenticated and the date on which the original issue of such Additional Notes is to be authenticated.

     (c) The Trustee may appoint an agent (the “ Authenticating Agent ”) reasonably acceptable to the Company to authenticate the Notes. Unless limited by the terms of such appointment, any such Authenticating Agent may authenticate Notes whenever the Trustee may do so. Each reference in the Indenture to authentication by the Trustee includes authentication by the Authenticating Agent.

     (d) In case the Company or any Guarantor, pursuant to Article 5 or Section 10.02 , shall be consolidated, amalgamated or merged with or into any other Person, shall convert into another form of entity or continue in another jurisdiction or shall convey, transfer, lease or otherwise dispose of all or substantially all of its properties and assets to any Person, and the successor Person resulting from such consolidation, amalgamation, conversion or continuation, or surviving such merger, or into which any Company or any Guarantor shall have been merged, or the Person which shall have received a conveyance, transfer, lease or other disposition as aforesaid, shall have executed an indenture supplemental hereto with the Trustee pursuant to Article 5, any of the Notes authenticated or delivered prior to such consolidation, amalgamation, merger, conversion, continuation, conveyance, transfer, lease or other disposition may, from time to time, at the request of the successor Person, be exchanged for other Notes executed in the name of the successor Person with such changes in phraseology and form as may be appropriate, but otherwise in substance of like tenor as the Notes surrendered for such exchange and of like principal amount; and the Trustee, upon Company Order of the successor Person, shall authenticate and deliver Notes as specified in such order for the purpose of such exchange. If

Notes shall at any time be authenticated and delivered in any new name of a successor Person pursuant to this Section 1.04 in exchange or substitution for or upon registration of transfer of any Notes, such successor Person, at the option of the Holders but without expense to them, shall provide for the exchange of all Notes at the time outstanding for Notes authenticated and delivered in such new name.

     (e) The Registrar shall retain copies of all letters, notices and other written communications received pursuant to Section 1.01 or this Section 1.04 . The Company shall have the right to inspect and make copies of all such letters, notices or other written communications at any reasonable time upon the giving of reasonable prior written notice to the Registrar.

     Section 1.05 Transfer and Exchange .

     (a)  Global Notes . The Initial Notes and, to the extent specified as provided in Section 1.03(a)(2) , any Additional Notes shall be issued in the form of a permanent global Note, without interest coupons, substantially in the form of Exhibit A , which is hereby incorporated by reference and made a part of the Indenture, deposited with the Trustee, as custodian for DTC or its nominee (the “ Securities Custodian ”), duly executed by the Company and authenticated by the Trustee as hereinafter provided, including the legend set forth in Section 1.05(b) hereof. The Global Notes may be represented by more than one certificate, if so required by DTC’s rules regarding the maximum principal amount to be represented by a single certificate. The aggregate principal amount of any Global Note may from time to time be increased or decreased by adjustments made on the records of the Trustee, as Securities Custodian, as hereinafter provided.

     (b)  Legend . The Global Notes shall bear the following legend (the “ Global Note Legend ”) on the face thereof:

“UNLESS THIS CERTIFICATE IS PRESENTED BY AN AUTHORIZED REPRESENTATIVE OF THE DEPOSITORY TRUST COMPANY, A NEW YORK CORPORATION (“DTC”), NEW YORK, NEW YORK, TO THE COMPANY OR ITS AGENT FOR REGISTRATION OF TRANSFER, EXCHANGE OR PAYMENT, AND ANY CERTIFICATE ISSUED IS REGISTERED IN THE NAME OF CEDE & CO. OR IN SUCH OTHER NAME AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC (AND ANY PAYMENT IS MADE TO CEDE & CO. OR TO SUCH OTHER ENTITY AS IS REQUESTED BY AN AUTHORIZED REPRESENTATIVE OF DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR OTHERWISE BY OR TO ANY PERSON IS WRONGFUL INASMUCH AS THE REGISTERED OWNER HEREOF, CEDE & CO., HAS AN INTEREST HEREIN.

TRANSFERS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS IN WHOLE, BUT NOT IN PART, TO NOMINEES OF DTC OR TO A SUCCESSOR THEREOF OR SUCH SUCCESSOR’S NOMINEE AND TRANSFERS OF PORTIONS OF THIS GLOBAL NOTE SHALL BE LIMITED TO TRANSFERS MADE IN ACCORDANCE WITH THE RESTRICTIONS SET FORTH IN THE INDENTURE REFERRED TO ON THE REVERSE HEREOF.”

     (c)  Book-Entry Provisions .

     (1) This Section 1.05(c) shall apply only to Global Notes deposited with the Trustee, as custodian for DTC.

     (2) Each Global Note initially shall (x) be registered in the name of DTC for such Global Note or the nominee of DTC, (y) be delivered to the Trustee as custodian for DTC and (z) bear the legend as set forth in Section 1.05(b) .

     (3) Members of, or participants in, DTC (“ Agent Members ”) shall have no rights under the Indenture with respect to any Global Note held on their behalf by DTC or by the Trustee as the custodian of DTC or under such Global Note, and DTC may be treated by the Company, the Guarantors, the Trustee and any agent of the Company or the Trustee as the absolute owner of such Global Note for all purposes whatsoever. Notwithstanding the foregoing, nothing herein shall (A) prevent the Company, the Guarantors, the Trustee or any agent of the Company or the Trustee from giving effect to any written certification, proxy or other authorization furnished by DTC or (B) impair, as between DTC and its Agent Members, the operation of customary practices of DTC governing the exercise of the rights of a Holder of a beneficial interest in any Global Note.

     (4) In connection with any transfer of a portion of the beneficial interest in a Global Note pursuant to subsection (d) of this Section 1.05(c) to beneficial owners who are required to hold Definitive Notes, the Securities Custodian shall reflect on its books and records the date and a decrease in the principal amount of such Global Note in an amount equal to the principal amount of the beneficial interest in the Global Note to be transferred, and the Company shall execute, and the Trustee shall authenticate and deliver, one or more Definitive Notes of like tenor and amount.

     (5) In connection with the transfer of an entire Global Note to beneficial owners pursuant to subsection (6) of this Section 1.05(c) , such Global Note shall be deemed to be surrendered to the Trustee for cancellation, and the Company shall execute, and the Trustee shall authenticate and deliver, to each beneficial owner identified by DTC in exchange for its beneficial interest in such Global Note, an equal aggregate principal amount of Definitive Notes of authorized denominations.

     (6) The registered Holder of a Global Note may grant proxies and otherwise authorize any person, including Agent Members and persons that may hold interests through Agent Members, to take any action which a Holder is entitled to take under the Indenture or the Notes.

     (d)  Definitive Notes . (1) Except as provided below, owners of beneficial interests in Global Notes will not be entitled to receive Definitive Notes. If required to do so pursuant to any applicable law or regulation, beneficial owners may obtain Definitive Notes in exchange for their beneficial interests in a Global Note upon written request in accordance with DTC’s and the Registrar’s procedures. In addition, Definitive Notes shall be transferred to all beneficial owners in exchange for their beneficial interests in a Global Note if (a) DTC notifies the Company that it is unwilling or unable to continue as depositary for such Global Notes or DTC ceases to be a clearing agency registered under the Exchange Act, at a time when DTC is required to be so registered in order to act as depositary, and, in either case, a successor depositary is not appointed by the Company within 90 days of such notice, (b) the Company, at its option, notifies the Trustee in writing that it elects to cause the issuance of Definitive Notes or (c) a Default or Event of Default has occurred and is continuing with respect to the Notes.

     (2) In connection with the exchange of a portion of a Definitive Note for a beneficial interest in a Global Note, the Trustee shall cancel such Definitive Note, and the Company shall execute, and the Trustee shall authenticate and deliver, to the transferring Holder a new Definitive Note representing the principal amount not so transferred.

     (e)  Obligations with Respect to Transfers and Exchanges of Notes .

     (1) To permit registrations of transfers and exchanges, the Company shall, subject to the other terms and conditions of this Article 1 and Article II of the Base Indenture, execute, and the Trustee shall authenticate, Definitive Notes and Global Notes at the Registrar’s or co-registrar’s request.

     (2) No service charge shall be made to a Holder for any registration of transfer or exchange, but the Company may require payment of a sum sufficient to cover any transfer tax, assessments, or similar governmental charge payable in connection therewith (other than any such transfer taxes, assessments or similar governmental charges payable upon exchange or transfer pursuant to Sections 1.04(d) , 3.08, 4.07 , 4.09 or 9.05 ).

     (3) The Registrar or co-registrar shall not be required to register the transfer or exchange of (i) any Notes selected for redemption (except in the case of Notes to be redeemed in part, the portion of the Note not to be redeemed) or (ii) any Notes for a period beginning 15 days before a selection of Notes to be redeemed.

     (4) Prior to the due presentation for registration of transfer of any Note, the Company, the Trustee, the Paying Agent, the Registrar or any co-registrar may deem and treat the person in whose name a Note is registered as the absolute owner of such Note for the purpose of receiving payment of principal of, premium, if any, on and interest on, such Note and for all other purposes whatsoever, whether or not such Note is overdue, and none of the Company, the Trustee, the Paying Agent, the Registrar or any co-registrar shall be affected by notice to the contrary.

     (5) All Notes issued upon any transfer or exchange pursuant to the terms of the Indenture shall evidence the same debt and shall be entitled to the same benefits under the Indenture as the Notes surrendered upon such transfer or exchange.

     (f)  No Obligation of the Trustee .

     (1) The Trustee shall have no responsibility or obligation to any beneficial owner of a Global Note, a member of, or a participant in, DTC or other Person with respect to the accuracy of the records of DTC or its nominee or of any participant or member thereof, with respect to any ownership interest in the Notes or with respect to the delivery to any participant, member, beneficial owner or other Person (other than DTC) of any notice (including any notice of redemption) or the payment of any amount or delivery of any Notes (or other Note or property) under or with respect to such Notes. All notices and communications to be given to the Holders and all payments to be made to Holders in respect of the Notes shall be given or made only to or upon the order of the registered Holders (which shall be DTC or its nominee in the case of a Global Note). The rights of beneficial owners in any Global Note shall be exercised only through DTC subject to the applicable rules and procedures of DTC. The

Trustee may rely and shall be fully protected in relying upon information furnished by DTC with respect to its members, participants and any beneficial owners.

     (2) The Trustee shall have no obligation or duty to monitor, determine or inquire as to compliance with any restrictions on transfer imposed under the Indenture or under applicable law with respect to any transfer of any interest in any Note (including any transfers between or among DTC participants, members or beneficial owners in any Global Note) other than to require delivery of such certificates and other documentation or evidence as are expressly required by, and to do so if and when expressly required by, the terms of the Indenture, and to examine the same to determine substantial compliance as to form with the express requirements hereof.

ARTICLE 2

DEFINITIONS AND INCORPORATION BY REFERENCE

     All capitalized terms contained in this Supplemental Indenture shall, except as specifically provided for herein and except as the context may otherwise require, have the meanings given to such terms in the Base Indenture. Unless otherwise specified or the context otherwise requires, (i) all references in this Supplemental Indenture to Articles, Sections or Exhibits refer to Articles, or Sections of or Exhibits to this Supplemental Indenture and (ii) the terms “herein,” “hereof,” “hereunder” and any other word of similar import refers to this Supplemental Indenture. In the event of any inconsistency between the Base Indenture and this Supplemental Indenture, this Supplemental Indenture shall govern. The rules of interpretation set forth in the Base Indenture shall be applied hereto as if set forth in full herein. Unless the context otherwise requires, the following terms shall have the following meanings:

     Section 2.01 Definitions

     “ Acquired Debt ” means, with respect to any specified Person:

     “ Additional Assets ” means:

provided , however , that any such Restricted Subsidiary described in clause (2) or (3) is primarily engaged in the Oil and Gas Business.

     “ Additional Notes ” has the meaning ascribed to it in Section 1.01 of this Supplemental Indenture.

     “ Adjusted Consolidated Net Tangible Assets ” means (without duplication), as of the date of determination:

(1) the sum of:

(a) discounted future net revenue from proved crude oil and natural gas reserves of the Company and its Restricted Subsidiaries calculated in accordance with SEC guidelines before any state or Federal income taxes, as estimated in a reserve report prepared as of the end of the fiscal year ending at least 91 days prior to the date of determination, which reserve report is prepared or audited by independent petroleum engineers as increased by, as of the date of determination, the discounted future net revenue of:

and decreased by, as of the date of determination, the discounted future net revenue attributable to:

provided , however , that, in the case of each of the determinations made pursuant to clauses (i) through (iv), such increases and decreases shall be estimated by the Company’s engineers, except that if as a result of such acquisitions, dispositions, discoveries, extensions or revisions, there is a Material Change, then such increases and decreases in the discounted future net revenue shall be confirmed in writing by an independent petroleum engineer;

(b) the capitalized costs that are attributable to crude oil and natural gas properties of the Company and its Restricted Subsidiaries to which no proved crude oil and natural gas reserves are attributable, based on the Company’s books and records as of a date no earlier than the date of the Company’s latest available annual or quarterly financial statements;

(c) the Net Working Capital (excluding, to the extent included in the determination of discounted future net revenues under clause (1)(a) above, any adjustments made pursuant to FAS 143) as of a date no earlier than the date of the Company’s latest available annual or quarterly financial statements; and

(d) the greater of

(2) the sum of:

(a) Minority Interests;

(b) any net natural gas balancing liabilities of the Company and its Restricted Subsidiaries reflected in the Company’s latest audited financial statements;

(c) to the extent included in clause (1)(a) above, the discounted future net revenue, calculated in accordance with SEC guidelines (utilizing the same prices in the Company’s year-end reserve report), attributable to reserves subject to

participation interests, overriding royalty interests or other interests of third parties, pursuant to participation, partnership, vendor financing or other agreements then in effect, or which otherwise are required to be delivered to third parties;

(d) to the extent included in clause (1)(a) above, the discounted future net revenue calculated in accordance with SEC guidelines (utilizing the same prices utilized in the Company’s year-end reserve report), attributable to reserves that are required to be delivered to third parties to fully satisfy the obligations of the Company and its Restricted Subsidiaries with respect to Volumetric Production Payments on the schedules specified with respect thereto; and

(e) the discounted future net revenue, calculated in accordance with SEC guidelines, attributable to reserves subject to Dollar-Denominated Production Payments that, based on the estimates of production included in determining the discounted future net revenue specified in the immediately preceding clause (i)(a) (utilizing the same prices utilized in the Company’s year-end reserve report), would be necessary to satisfy fully the obligations of the Company and its Restricted Subsidiaries with respect to Dollar-Denominated Production Payments on the schedules specified with respect thereto.

If the Company changes its method of accounting from the full cost method to the successful efforts method or a similar method of accounting, “Adjusted Consolidated Net Tangible Assets” will continue to be calculated as if the Company were still using the full cost method of accounting.

     “ Applicable Premium ” means, with respect to any Note on any Redemption Date, an amount equal to the excess of:

Unless the Company defaults in payment of the Applicable Premium, on and after the applicable Redemption Date, interest will cease to accrue on the Notes to be redeemed.

     “ Asset Sale ” means:

     Notwithstanding the preceding, none of the following items will be deemed to be an Asset Sale:

     “ Attributable Debt ” in respect of a sale and leaseback transaction means, at the time of determination, the present value of the obligation of the lessee for net rental payments during the remaining term of the lease included in such sale and leaseback transaction including any period for which such lease has been extended or may, at the option of the lessor, be extended. Such present value shall be calculated using a discount rate equal to the rate of interest implicit in such transaction, determined in accordance with GAAP.

     “ Beneficial Owner ” has the meaning assigned to such term in Rule 13d-3 and Rule 13d-5 under the Exchange Act, except that in calculating the beneficial ownership of any particular “person” (as that term is used in Section 13(d)(3) of the Exchange Act), such “person” will be deemed to have beneficial ownership of all securities that such “person” has the right to acquire by conversion or exercise of other securities, whether such right is currently exercisable or is exercisable only after the passage of time. The terms “Beneficial Ownership”, “Beneficially Owns” and “Beneficially Owned” have a corresponding meaning.

     “ Capital Lease Obligation ” means, at the time any determination is to be made, the amount of the liability in respect of a capital lease that would at that time be required to be capitalized on a balance sheet prepared in accordance with GAAP, and the Stated Maturity thereof shall be the date of the last payment of rent or any other amount due under such lease prior to the first date upon which such lease may be prepaid by the lessee without payment of a penalty.

     “ Cash Equivalents ” means:

     “ Change of Control ” means the occurrence of any of the following:

     “ Change of Control Triggering Event ” means the occurrence of both a Change of Control and a Rating Decline with respect to the Notes.

     “ Consolidated Cash Flow ” means, with respect to any specified Person for any period, the Consolidated Net Income of such Person for such period plus without duplication:

     in each case, on a consolidated basis and determined in accordance with GAAP.

     Notwithstanding the foregoing, the provision for taxes on the income or profits of, and the depreciation, depletion and amortization and other non-cash charges and expenses of, a Restricted Subsidiary of the referent Person shall be added to Consolidated Net Income to compute Consolidated Cash Flow only to the extent (and in the same proportion) that the Net Income of such Restricted Subsidiary was included in calculating the Consolidated Net Income of such Person and only if a corresponding amount would be permitted at the date of determination to be dividended to the referent Person by such Restricted Subsidiary without prior governmental approval (that has not been obtained), and without direct or indirect restriction pursuant to the terms of its charter and all agreements, instruments, judgments, decrees, orders, statutes, rules and governmental regulations applicable to that Restricted Subsidiary or its stockholders.

     “ Consolidated Net Income ” means, with respect to any specified Person for any period, the aggregate of the Net Income of such Person and its Restricted Subsidiaries for such period, on a consolidated basis, determined in accordance with GAAP; provided that:

     “ Consolidated Net Worth ” means, with respect to any specified Person as of any date, the sum of:

     “ Continuing Directors ” means, as of any date of determination, any member of the Board of Directors of the Company who:

     “ Credit Agreement ” means that certain Amended and Restated Credit Agreement, dated as of March 2, 2006, by and among the Company and Mariner Energy Resources, Inc., as borrowers, Union Bank of California, N.A., as administrative agent and issuing lender, BNP Paribas, as syndication agent, and the lenders from time to time party thereto, providing for up to $1.0 billion of revolving credit borrowings and letters of credit, including any related notes, Guarantees, collateral documents, instruments and agreements executed in connection therewith, and, in each case, as amended, restated, modified, renewed, refunded, replaced (whether upon or after termination or otherwise), supplemented or refinanced (including by means of sales of debt securities to institutional investors) in whole or in part from time to time.

     “ Credit Facilities ” means, with respect to the Company or any of its Restricted Subsidiaries, one or more debt facilities (including, without limitation, the Credit Agreement), commercial paper facilities or Debt Issuances with banks, investment banks, insurance companies, mutual funds, other institutional lenders, institutional investors or any of the foregoing providing for revolving credit loans, term loans, receivables financing (including through the sale of receivables to such lenders, other financiers or to special purpose entities formed to borrow from (or sell such receivables to) such lenders or other financiers against such receivables), letters of credit, bankers’ acceptances, other borrowings or Debt Issuances, in each case, as amended, restated, modified, renewed, extended, refunded, replaced or refinanced (in each case, without limitation as to amount), in whole or in part, from time to time (including through one or more Debt Issuances) and any agreements and related documents governing Indebtedness or Obligations incurred to refinance amounts then outstanding or permitted to be outstanding, whether or not with the original administrative agent, lenders, investment banks, insurance companies, mutual funds, other institutional lenders, institutional investors or any of the foregoing and whether provided under the original agreement, indenture or other documentation relating thereto).

     “ Debt Issuances ” means, with respect to the Company or any Restricted Subsidiary, one or more issuances after the Issue Date of Indebtedness evidenced by notes, debentures, bonds or other similar securities or instruments.

     “ Default ” means any event that is, or with the passage of time or the giving of notice or both would be, an Event of Default as defined in Section 6.01 .

     “ Definitive Note ” means a certificated Note registered in the name of the Holder thereof and issued in accordance with Section 1.05(d) hereof, in the form of Exhibit A hereto except that such Note shall not bear the Global Note Legend specified in Section 1.05(b) .

     “ De Minimis Guaranteed Amount ” means a principal amount of Indebtedness that does not exceed $5.0 million.

     “ Disqualified Stock ” means any Capital Stock that, by its terms (or by the terms of any security into which it is convertible, or for which it is exchangeable, in each case, at the option of the holder of the Capital Stock), or upon the happening of any event, matures or is mandatorily redeemable, pursuant to a sinking fund obligation or otherwise, or redeemable at the option of the holder of the Capital Stock, in whole or in part, on or prior to the date that is 91 days after the date on which the Notes mature; provided, that only the portion of Capital Stock which so matures or is

mandatorily redeemable, or is so redeemable at the option of the holder thereof prior to such date, will be deemed to be Disqualified Stock. Notwithstanding the preceding sentence, any Capital Stock that would constitute Disqualified Stock solely because the holders of the Capital Stock have the right to require the Company to repurchase such Capital Stock upon the occurrence of a change of control or an asset sale will not constitute Disqualified Stock if the terms of such Capital Stock provide that the Company may not repurchase or redeem any such Capital Stock pursuant to such provisions unless such repurchase or redemption complies with Section 4.04 . The amount of Disqualified Stock deemed to be outstanding at any time for purposes of this Supplemental Indenture will be the maximum amount that the Company and its Restricted Subsidiaries may become obligated to pay upon the maturity of, or pursuant to any mandatory redemption provisions of, such Disqualified Stock, exclusive of accrued dividends.

     “ Dollar-Denominated Production Payments ” means production payment obligations recorded as liabilities in accordance with GAAP, together with all undertakings and obligations in connection therewith.

     “ Domestic Subsidiary ” means any Restricted Subsidiary of the Company that was formed under the laws of the United States or any state of the United States or the District of Columbia or that guarantees or otherwise provides direct credit support for any Indebtedness of the Company.

     “ Existing Indebtedness ” means Indebtedness of the Company and its Subsidiaries (other than Indebtedness under the Credit Agreement but including the Existing Senior Notes) in existence on the date of this Supplemental Indenture, until such amounts are repaid.

     “ Existing Senior Notes ” means the Company’s 7 ¹ / 2 % senior notes due 2013 and its 8% senior notes due 2017.

     “ Fair Market Value ” means the value that would be paid by a willing buyer to an unaffiliated willing seller in a transaction not involving distress or necessity of either party, determined in good faith by the Board of Directors of the Company (unless otherwise provided in this Supplemental Indenture), which determination will be conclusive for all purposes under this Supplemental Indenture.

     “ Fixed Charge Coverage Ratio ” means with respect to any specified Person for any period, the ratio of the Consolidated Cash Flow of such Person for such period to the Fixed Charges of such Person for such period. In the event that the specified Person or any of its Restricted Subsidiaries incurs, assumes, guarantees, repays, repurchases, redeems, defeases or otherwise discharges any Indebtedness (other than ordinary working capital borrowings) or issues, repurchases or redeems Preferred Stock subsequent to the commencement of the period for which the Fixed Charge Coverage Ratio is being calculated and on or prior to the date on which the event for which the calculation of the Fixed Charge Coverage Ratio is made (the “ Calculation Date ”), then the Fixed Charge Coverage Ratio will be calculated giving pro forma effect to such incurrence, assumption, Guarantee, repayment, repurchase, redemption, defeasance or other discharge of Indebtedness, or such issuance, repurchase or redemption of Preferred Stock, and the use of the proceeds therefrom, as if the same had occurred at the beginning of the applicable four-quarter reference period.

     In addition, for purposes of calculating the Fixed Charge Coverage Ratio:

     “ Fixed Charges ” means, with respect to any specified Person for any period, the sum, without duplication, of:

     “ Foreign Subsidiary ” means any Restricted Subsidiary of the Company that was not formed under the laws of the United States or any state of the United States or the District of Columbia.

     “ Global Note ” means a permanent global note that is in the Form of Note attached hereto as Exhibit A , and that is deposited with the Depositary or its custodian and registered in the name of the Depositary.

     “ Guarantee ” means a guarantee other than by endorsement of negotiable instruments for collection in the ordinary course of business, direct or indirect, in any manner including, without limitation, by way of a pledge of assets or through letters of credit or reimbursement agreements in respect thereof, of all or any part of any Indebtedness (whether arising by virtue of partnership arrangements, or by agreements to keep-well, to maintain financial statement conditions or otherwise), or entered into for purposes of assuring in any other manner the obligee of such Indebtedness of the payment thereof or to protect such obligee against loss in respect thereof (in whole or in part).

     “ Guarantors ” means each of:

     (1) Mariner LP LLC, Mariner Energy Resources, Inc., MC Beltway 8 LLC and Mariner Gulf of Mexico LLC; and

     (2) any other Subsidiary of the Company that executes a Note Guarantee in accordance with the provisions of this Supplemental Indenture,

and their respective successors and assigns, in each case, until the Note Guarantee of such Person has been released in accordance with the provisions of this Supplemental Indenture.

     “ Hedging Obligations ” means, with respect to any specified Person, the obligations of such Person under:

     “ Holder ” or “ Holders ” means a Person or Persons in whose name a Note is registered in the Note Register.

     “ Hydrocarbons ” means oil, gas, casinghead gas, drip gasoline, natural gasoline, condensate, distillate, liquid hydrocarbons, gaseous hydrocarbons and all constituents, elements or compounds thereof and products refined or processed therefrom.

     “ Indebtedness ” means, with respect to any specified Person, any indebtedness of such Person (excluding accrued expenses and trade payables), whether or not contingent:

provided that the indebtedness described in clauses (1), (2), (4) and (5) shall be included in this definition of Indebtedness only if, and to the extent that, the indebtedness described in such clauses would appear as a liability upon a balance sheet of such Person prepared in accordance with GAAP. Subject to clause (9) of the preceding sentence, neither Dollar-Denominated Production Payments nor Volumetric Production Payments shall be deemed to be Indebtedness.

     The amount of any Indebtedness outstanding as of any date will be:

     The amount of Indebtedness of any Person at any date will be the outstanding balance at such date of all unconditional obligations as described above and the maximum liability, upon the occurrence of the contingency giving rise to the obligation, of any contingent obligations at such date.

     In addition, “Indebtedness” of any Person shall include Indebtedness described in the preceding paragraph that would not appear as a liability on the balance sheet of such Person if:

     “ Indenture ” means the Base Indenture, as supplemented and modified by this Supplemental Indenture, as either may be amended or supplemented from time to time in accordance with the terms hereof, including the provisions of the TIA that are deemed to be a part hereof.

     “ Initial Notes ” has the meaning ascribed to it in Section 1.01 of this Supplemental Indenture.

     “ Investments ” means, with respect to any Person, all direct or indirect investments by such Person in other Persons (including Affiliates) in the forms of loans (including Guarantees or other obligations), advances or capital contributions (excluding endorsements of negotiable instruments and documents in the ordinary course of business, and commission, travel and similar advances to officers, employees and consultants made in the ordinary course of business), purchases or other acquisitions for consideration of Indebtedness, Equity Interests or other securities, together with all items that are or would be classified as investments on a balance sheet prepared in accordance with GAAP. If the Company or any Restricted Subsidiary of the Company sells or otherwise disposes of any Equity Interest of any direct or indirect Subsidiary of the Company such that, after giving effect to any such sale or disposition, such Person is no longer a Restricted Subsidiary of the Company, the Company shall be deemed to have made an Investment on the date of any such sale or disposition equal to the Fair Market Value of the Company’s Investments in such Restricted Subsidiary that were not sold or disposed of in an amount determined as provided in Section 4.04 . The acquisition by the Company or any Subsidiary of the Company of a Person that holds an Investment in a third Person will be deemed to be an Investment by the Company or such Subsidiary in such third Person in an amount equal to the Fair Market Value of the Investments held by the acquired Person in such third Person in an amount determined as provided in Section 4.04 . Except as otherwise provided in this Supplemental Indenture, the amount of an Investment will be determined at the time the Investment is made and without giving effect to subsequent changes in value.

     “ Investment Grade Rating ” means a rating equal to or higher than:

or, if either such entity ceases to rate the Notes for reasons outside of the Company’s control, the equivalent investment grade credit rating from any other Rating Agency.

     “ Investment Grade Rating Event ” means the first day on which the Notes have an Investment Grade Rating from a Rating Agency and no Default has occurred and is then continuing under this Supplemental Indenture.

     “ Investment Grade Securities ” means:

     “ Issue Date ” means June 10, 2009, the date of original issuance of the Notes.

     “ Lien ” means, with respect to any asset, any mortgage, lien, pledge, charge, security interest or encumbrance of any kind in respect of such asset, whether or not filed, recorded or otherwise perfected under applicable law, including any conditional sale or other title retention agreement, any lease in the nature thereof, any option or other agreement to sell or give a security interest in and any filing of any financing statement under the Uniform Commercial Code (or equivalent statutes) of any jurisdiction.

     “ Material Change ” means an increase or decrease (excluding changes that result solely from changes in prices and changes resulting from the incurrence of previously estimated future development costs) of more than 25% during a fiscal quarter in the discounted future net revenues from proved crude oil and natural gas reserves of the Company and its Restricted Subsidiaries, calculated in accordance with clause (1)(a) of the definition of Adjusted Consolidated Net Tangible Assets; provided, however, that the following will be excluded from the calculation of Material Change:

     “ Minority Interest ” means the percentage interest represented by any shares of stock of any class of Capital Stock of a Restricted Subsidiary of the Company that are not owned by the Company or a Restricted Subsidiary of the Company.

     “ Moody’s ” means Moody’s Investors Service, Inc. or any successor to the rating agency business thereof.

     “ Net Income ” means, with respect to any specified Person, the net income (loss) of such Person, determined in accordance with GAAP and before any reduction in respect of Preferred Stock dividends, excluding, however:

     “ Net Proceeds ” means the aggregate cash proceeds received by the Company or any of its Restricted Subsidiaries in respect of any Asset Sale (including, without limitation, any cash received upon the sale or other disposition of any non-cash consideration received in any Asset Sale), net of:

     “ Net Working Capital ” means (a) all current assets of the Company and its Restricted Subsidiaries except current assets from commodity price risk management activities arising in the ordinary course of business, less (b) all current liabilities of the Company and its Restricted Subsidiaries, except current liabilities included in Indebtedness and any current liabilities from commodity price risk management activities arising in the ordinary course of business, in each case as set forth in the consolidated financial statements of the Company prepared in accordance with GAAP (excluding any adjustments made pursuant to FAS 133).

     “ Non-Recourse Debt ” means Indebtedness:

     “ Note Guarantee ” means the Securities Guarantee by each Guarantor of the Company’s Obligations under the Notes and the Indenture (including this Supplemental Indenture) with respect to the Notes, executed pursuant to the provisions of this Supplemental Indenture.

     “ Notes ” has the meaning ascribed to it in the third recital of this Supplemental Indenture and shall include the Initial Notes and any Additional Notes authenticated and delivered in accordance with Section 1.03 .

     “ Note Register ” means the register of Notes maintained by the Registrar pursuant to Section 2.5 of the Base Indenture.

     “ Obligations ” means any principal, interest, penalties, fees, indemnifications, reimbursements, damages and other liabilities payable under the documentation governing any Indebtedness.

     “ Oil and Gas Business ” means:

     “ Permitted Acquisition Indebtedness ” means Indebtedness or Disqualified Stock of the Company or any of the Company’s Restricted Subsidiaries to the extent such Indebtedness or Disqualified Stock was Indebtedness or Disqualified Stock of:

     “ Permitted Business Investments ” means Investments made in the ordinary course of, and of a nature that is or shall have become customary in, the Oil and Gas Business, including through agreements, transactions, interests or arrangements that permit one to share risk or costs, comply with regulatory requirements regarding local ownership or satisfy other objectives customarily achieved through the conduct of the Oil and Gas Business jointly with third parties, including without limitation:

     “ Permitted Investment ” means:

     “ Permitted Liens ” means, with respect to any Person:

     “ Permitted Refinancing Indebtedness ” means any Indebtedness of the Company or any of its Restricted Subsidiaries issued in exchange for, or the net proceeds of which are used to extend, renew, refund, refinance, replace, defease or discharge other Indebtedness of the Company or any of its Restricted Subsidiaries (other than intercompany Indebtedness); provided that:

     Notwithstanding the foregoing, any Indebtedness incurred under Credit Facilities pursuant to Section 4.03 shall be subject to the refinancing provisions of the definition of “Credit Facilities” and not pursuant to the requirements set forth in this definition of Permitted Refinancing Indebtedness.

     “ Preferred Stock ”, as applied to the Capital Stock of any corporation, means Capital Stock of any class or classes (however designated) which is preferred as to the payment of dividends, or as to the distribution of assets upon any voluntary or involuntary liquidation or dissolution of such corporation, over shares of Capital Stock of any other class of such corporation.

     “ Production Payments ” means, collectively, Dollar-Denominated Production Payments and Volumetric Production Payments.

     “ Production Payments and Reserve Sales ” means the grant or transfer by the Company or a Restricted Subsidiary of the Company to any Person of a royalty, overriding royalty, net profits interest, production payment (whether volumetric or dollar denominated), partnership or other interest

in oil and gas properties, reserves or the right to receive all or a portion of the production or the proceeds from the sale of production attributable to such properties, including any such grants or transfers pursuant to incentive compensation programs on terms that are reasonably customary in the oil and gas business for geologists, geophysicists and other providers of technical services to the Company or a Subsidiary of the Company.

     “ Prospectus ” means the prospectus, dated June 2, 2009, as supplemented by the prospectus supplement, dated June 4, 2009, prepared in connection with the issuance of the Initial Notes.

     “ Rating Agency ” means each of S&P and Moody’s, or if S&P or Moody’s or both shall not make a rating on the Notes publicly available, a nationally recognized statistical rating agency or agencies, as the case may be, selected by the Company (as certified by a Board Resolution) which shall be substituted for S&P or Moody’s, or both, as the case may be.

     “ Rating Decline ” means the occurrence of:

provided , however , that such decrease or withdrawal occurs on, or within 90 days before or after the earlier of (a) a Change of Control, (b) the date of public notice of the occurrence of a Change of Control or (c) public notice of the intention by the Company to effect a Change of Control (which period shall be extended so long as the rating of the Notes is under publicly announced consideration for downgrade by either Rating Agency).

     “ Redemption Date ” when used with respect to any Note to be redeemed, in whole or in part, means the date fixed for such redemption by or pursuant to this Supplemental Indenture.

     “ Reference Date ” means April 24, 2006.

     “ Restricted Investment ” means an Investment other than a Permitted Investment.

     “ Restricted Subsidiary ” of a Person means any Subsidiary of the referent Person that is not an Unrestricted Subsidiary.

     “ sale and leaseback transaction ” means an arrangement relating to property now owned or hereafter acquired whereby the Company or a Restricted Subsidiary transfers such property to a Person and the Company or a Restricted Subsidiary leases it from such Person.

     “ S&P ” means Standard & Poor’s Ratings Services, a division of The McGraw-Hill Companies, Inc.

     “ Senior Debt ” means:

Notwithstanding anything to the contrary in the preceding sentence, Senior Debt will not include:

For the avoidance of doubt, “Senior Debt” will not include any trade payables or taxes owed or owing by the Company or any Restricted Subsidiary.

     “ Stated Maturity ” means, with respect to any installment of interest or principal on any series of Indebtedness, the date on which the payment of interest or principal was scheduled to be paid in the documentation governing such Indebtedness as of the date of this Supplemental Indenture, and will not include any contingent obligations to repay, redeem or rep