AMENDMENT NO. 6, WAIVER AND AGREEMENT

Exhibit 10.19

AMENDMENT NO. 6, WAIVER AND AGREEMENT

      This Amendment No. 6, Waiver and Agreement (“Agreement”) dated as of January 20, 2006 (“Effective Date”) is among Mariner Energy, Inc., a Delaware corporation (the “Borrower”), Mariner LP LLC, a Delaware limited liability company (“Mariner LLC”), Mariner Energy Texas LP, a Delaware limited partnership (“Mariner LP,” and together with Mariner LLC, collectively referred to herein as the “Guarantors”), the Lenders (as defined below), and Union Bank of California, N.A., as administrative agent for such Lenders (in such capacity, the “Administrative Agent”) and as issuing lender for such Lenders (in such capacity, the “Issuing Lender”).

RECITALS

      A.     The Borrower, the Lenders, Issuing Lender and the Administrative Agent are parties to the Credit Agreement dated as of March 2, 2004, as amended by that certain Amendment No. 1 and Assignment Agreement dated as of July 14, 2004, that certain Amendment No. 2 and Consent dated as of February 7, 2005, that certain Amendment No. 3 and Consent dated as of March 3, 2005, that certain Amendment No. 4 dated as of July 14, 2005, and that certain Amendment No. 5 dated as of August 5, 2005 (as so amended, the “Credit Agreement”).

      B.     At the request of the Borrower, the Administrative Agent and the Lenders wish to, subject to the terms and conditions of this Agreement, (1) increase the Borrowing Base (as defined in the Credit Agreement), (2) acknowledge the existence of certain Defaults and Events of Default (each as defined in the Credit Agreement), (3) provide for a waiver of such existing Defaults and Events of Default as set forth below, and (4) amend certain provisions of the Credit Agreements as set forth herein.

      THEREFORE, the Borrower, the Guarantors, the Lenders, the Issuing Lender and the Administrative Agent hereby agree as follows:

ARTICLE I.

      Section 1.01      Terms Defined Above. As used in this Agreement, each of the terms defined in the opening paragraph and the Recitals above shall have the meanings assigned to such terms therein.

      Section 1.02      Terms Defined in the Credit Agreement. Each term defined in the Credit Agreement and used herein without definition shall have the meaning assigned to such term in the Credit Agreement, unless expressly provided to the contrary.

      Section 1.03      Other Definitional Provisions. The words “hereby”, “herein”, “hereinafter”, “hereof”, “hereto” and “hereunder” when used in this Agreement shall refer to this Agreement as a whole and not to any particular Article, Section, subsection or provision of this Agreement. Article, Section, subsection and Exhibit references herein are to such Articles, Sections, subsections and Exhibits of this Agreement unless otherwise specified. All titles or headings to Articles, Sections, subsections or other divisions of this Agreement or the exhibits

hereto, if any, are only for the convenience of the parties and shall not be construed to have any effect or meaning with respect to the other content of such Articles, Sections, subsections, other divisions or exhibits, such other content being controlling as the agreement among the parties hereto. Whenever the context requires, reference herein made to the single number shall be understood to include the plural; and likewise, the plural shall be understood to include the singular. Words denoting sex shall be construed to include the masculine, feminine and neuter, when such construction is appropriate; and specific enumeration shall not exclude the general but shall be construed as cumulative. Definitions of terms defined in the singular or plural shall be equally applicable to the plural or singular, as the case may be, unless otherwise indicated.

ARTICLE II.

      Section 2.01      Borrowing Base Increase . Subject to the terms of this Agreement, the Lenders and the Borrower hereby agree that, as of the Effective Date, the Borrowing Base shall be $185,000,000. Such Borrowing Base shall remain in effect until the next redetermination made pursuant to Section 2.02 of the Credit Agreement, as amended hereby.

      Section 2.02      Waiver .

      (a) The Borrower hereby acknowledges the existence of Defaults and Events of Default (collectively, the “Waiver Defaults”) arising directly as a result of the Borrower’s failure to comply with the requirements of Section 6.06 and Section 6.15 of the Credit Agreement in respect of its formation of, and investments in, MEI Sub, Inc., a Delaware corporation as a wholly owned Subsidiary of the Borrower (the “MEI Sub”).

      (b) The Lenders hereby agree, subject to the terms of this Agreement, to waive the Waiver Defaults. The waiver by the Lenders described in the preceding sentence is contingent upon the satisfaction of the conditions precedent set forth below in this Agreement. The waiver is limited to the Waiver Defaults and to the extent described herein and shall not be construed to be a consent to, or a permanent waiver of, the Sections covered by the Waiver Defaults or any other terms, provisions, covenants, warranties or agreements contained in the Credit Agreement or in any of the other Loan Documents. The Lenders and the Administrative Agent reserve the right to exercise any rights and remedies available to them in connection with any other present or future defaults with respect to the Credit Agreement or any other provision of any Loan Document.

      Section 2.03      Amendments to Credit Agreement .

      (a) Section 1.01 of the Credit Agreement is amended by adding the following new terms in alphabetical order:

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      (b) Section 2.02(b) of the Credit Agreement is amended by adding to the end thereof a new clause (v) as follows:

      (c) Section 6.15 of the Credit Agreement is amended and restated to read in its entirety as follows:

      (d) Article VI of the Credit Agreement is hereby further amended by adding a new Section 6.23 to the end thereof as follows: