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                                                                    EXHIBIT 10.4

                                SECOND AMENDMENT

                                       TO

                  SECOND AMENDED AND RESTATED CREDIT AGREEMENT


                  Second Amendment, dated as of October 22, 2003 (this
"Amendment"), to the Second Amended and Restated Credit Agreement, dated as of
June 5, 2003 (the "Credit Agreement"), by and among MISSION RESOURCES
CORPORATION, a corporation formed under the laws of the State of Delaware (the
"Borrower"), the several banks and other financial institutions or entities from
time to time parties to thereto (the "Lenders"), FARALLON ENERGY LENDING,
L.L.C., as sole advisor, sole lead arranger and sole bookrunner (in such
capacity, the "Arranger"), JEFFERIES & COMPANY, INC., as the syndication agent
(in such capacity, the "Syndication Agent") and WELLS FARGO FOOTHILL, INC.,
formerly known as Foothill Capital Corporation, as the administrative agent (in
such capacity, the "Administrative Agent"). All terms used herein which are
defined in the Credit Agreement and not otherwise defined herein are used herein
as defined therein.

                  The Borrower and the Required Lenders desire to amend Section
2.7(b) of the Credit Agreement as hereinafter set forth.

                  Accordingly, the Borrower and the Majority Lenders hereby
agree as follows:

                           1. Conditions Subsequent. (a) Clause (b) of Section
2.7 of the Credit Agreement is hereby amended and restated in its entirety to
read as follows:

                           "(b) Unless the Required Lenders shall otherwise
                  agree, if on any date any Loan Party shall receive Net Cash
                  Proceeds from any Asset Sale or Recovery Event then, except as
                  provided below, the Loans shall be prepaid by an amount equal
                  to the amount of such Net Cash Proceeds as set forth in
                  Section 2.7(e). No prepayment shall be required under this
                  Section 2.7(b) with respect to the following: (i) at the
                  written request of the Borrower prior to the applicable
                  Reinvestment Prepayment Date to the extent such Net Cash
                  Proceeds have not been used to purchase or otherwise acquire
                  Replacement Assets, up to $5,000,000 in aggregate Net Cash
                  Proceeds received from one or more Asset Sales or Recovery
                  Events during the term of the Loans, (ii) the Net Cash
                  Proceeds of any Asset Sale or Recovery Event used to pay for
                  the acquisition of Replacement Assets acquired after the date
                  of such Asset Sale or Recovery Event and prior to the
                  applicable Reinvestment Prepayment Date, provided, that the
                  Borrower shall have delivered a Reinvestment Notice to the
                  Administrative Agent within twenty Business Days after such
                  acquisition or expenditure, and (iii) that portion of the Net
                  Cash Proceeds of any Asset Sale equal to the aggregate cash
                  consideration paid by a Loan Party for the acquisition of
                  Replacement Assets during the 90-day period immediately prior
                  to the consummation of such Asset Sale, provided, that the
                  Borrower shall have delivered a Reinvestment Notice to the
                  Administrative


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                  Agent not less than three Business Days prior to the
                  Reinvestment Prepayment Date; provided, that the sum (without
                  duplication) of the aggregate Net Cash Proceeds of Asset Sales
                  and Recovery Events that may be excluded from the foregoing
                  prepayment requirement pursuant to clauses (i), (ii) and (iii)
                  shall not exceed $50,000,000 during the term of the Loans.
                  Except as provided in clauses (i), (ii) and (iii) of this
                  Section 2.7(b), or as otherwise may be agreed by the Required
                  Lenders, the Reinvestment Deferred Amounts received by the
                  Borrower or any of its Subsidiaries shall be applied as a
                  prepayment on the Obligations as set forth in Section 2.7(e).
                  The provisions of this Section 2.7(b) do not constitute a
                  consent to the consummation of any Disposition not permitted
                  by Section 6.4. Notwithstanding any provision hereof to the
                  contrary, with respect to the Term Loans to be prepaid
                  pursuant to this Section 2.7(b), such Term Loans will be
                  prepaid in the minimum amount of $1,000,000 and in integral
                  multiples thereof, and proceeds of Asset Sales otherwise
                  payable pursuant to this Section 2.7(b) with respect to such
                  Term Loans will cumulate until such minimum amount (or an
                  integral multiple thereof) is reached, and the parties agree
                  that these provisions shall not be applicable to the payment
                  of the Revolving Loan Obligations. Any amounts not applied to
                  the Term Loans as a result of the operation of the immediately
                  preceding sentence will be carried forward and taken into
                  account in connection with any subsequent prepayment pursuant
                  to this Section 2.7(b)."

                           (b) Clause (d) of Section 2.7 of the Credit Agreement
         is hereby amended and restated in its entirety to read as follows

                           "(d) Pending a prepayment of the Loans and/or the
                  acquisition of Replacement Assets with the Net Cash Proceeds
                  received from an Asset Sale and/or Recovery Event pursuant to
                  Section 2.7(b), such proceeds shall be deposited with the
                  Administrative Agent who shall hold such proceeds in an
                  interest bearing cash collateral account reasonably
                  satisfactory to it; provided, however, that the Loan Parties
                  shall not be required to deposit the proceeds from any Asset
                  Sale resulting in less than $250,000 in Net Cash Proceeds
                  until the aggregate Net Cash Proceeds of such Asset Sales
                  exceeds $1,000,000. From time to time, upon the written
                  request of the Borrower, and provided no Default has occurred
                  and is continuing, the Administrative Agent will release such
                  proceeds to the Borrower as necessary (i) for the acquisition
                  of Replacement Assets in accordance with Section 2.7(b)(ii) or
                  (ii) pursuant to the written request of the Borrower made in
                  accordance with Section 2.7(b)(i)."

                           2. Continued Effectiveness of Credit Agreement. The
Borrower hereby (i) confirms and agrees that each Loan Document to which it is a
party is, and shall continue to be, in full force and effect and is hereby
ratified and confirmed in all respects except that on and after the date hereof
all references in any such Loan Document to "the Credit Agreement", "thereto",
"thereof", "thereunder" or words of like import referring to the Credit
Agreement shall mean the Credit Agreement as amended by this Amendment, and (ii)
confirms and agrees that to the extent that any such Loan Document purports to
assign or pledge to the Collateral Agent, or to grant to the Collateral Agent a
security interest in or lien on, any collateral as security for the Obligations
of the Borrower from time to time existing in respect of


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the Credit Agreement and the Loan Documents, such pledge, assignment and/or
grant of the security interest or lien is hereby ratified and confirmed in all
respects.

                  3. Miscellaneous.

                  (a) This Amendment may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which shall be deemed to be an original, but all of which taken together shall
constitute one and the same agreement. Delivery of an executed counterpart of
this Amendment by telefacsimile shall be equally as effective as delivery of an
original executed counterpart of this Amendment.

                  (b) Section and paragraph headings herein are included for
convenience of reference only and shall not constitute a part of this Amendment
for any other purpose.

                  (c) This Amendment shall be governed by, and construed in
accordance with, the laws of the State of New York.

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                  IN WITNESS WHEREOF, the parties hereto have caused this
Amendment to be executed by their respective officers thereunto duly authorized
as of the day and year first above written.

                                          MISSION RESOURCES CORPORATION, as
                                          Borrower



                                          By: /s/ Richard W. Piacenti
                                              ----------------------------------
                                              Name:  Richard W. Piacenti
                                              Title: Executive VP & CFO



                                          FARALLON ENERGY LENDING, L.L.C., as
                                          Arranger and as a Lender



                                          By: /s/ William Mellin
                                              ----------------------------------
                                              Name:  William Mellin
                                              Title: Managing Member


                                          WELLS FARGO FOOTHILL, INC., as
                                          Administrative Agent and as a Lender



                                          By: /s/ Thomas Shughrue
                                              ----------------------------------
                                              Name:  Thomas Shughrue
                                              Title: Vice President

                                          ABLECO FINANCE LLC, as a Lender, for
                                          itself and on behalf of its affiliate
                                          assignees



                                          By: /s/ Kevin Genda
                                              ----------------------------------
                                              Name:  Kevin Genda
                                              Title: Sr. VP/Chief Credit Officer


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                                          HIGHBRIDGE/ZWIRN SPECIAL OPPORTUNITIES
                                          FUND, L.P., as a Lender

                                          By:  Highbridge/Zwirn Capital
                                               Management, LLC


                                          By: /s/ Daniel B. Zwirn
                                              ----------------------------------
                                              Name:  Daniel B. Zwirn
                                              Title: Managing Principal


                                          ARES LEVERAGED INVESTMENT FUND II,
                                          L.P., as a Lender

                                          By:  ARES Management II, L.P., its
                                               general partner


                                          By: /s/ Seth J. Brufsky
                                              ----------------------------------
                                              Name:  Seth J. Brufsky
                                              Title: Vice President


                                          TRS THEBE LLC, as Lender



                                          By: /s/ Deborah O'Keeffe
                                              ----------------------------------
                                              Name:  Deborah O'Keeffe
                                              Title: Vice President


                                          BERNARD LEVERAGED LOAN INVESTORS,
                                          LTD., as Lender



                                          By: /s/ Mora Parchment
                                              ----------------------------------
                                              Name:  Mora Parchment
                                              Title: Director