<PAGE>   1
                                                                   EXHIBIT 10.18


                          AMENDMENT dated as of November 30, 2000 (this
                  "Amendment") in respect of the SHORT-TERM REVOLVING CREDIT
                  AGREEMENT dated as of February 25, 1998, as amended and
                  restated pursuant to the Amendment and Restatement Agreement
                  dated as of February 23, 1999, as amended as of January 17,
                  2000, and as amended and restated pursuant to the Second
                  Amendment and Restatement Agreement dated as of March 31, 2000
                  (the "Credit Agreement"), among BURLINGTON RESOURCES, INC., a
                  Delaware corporation (the "Borrower"), the financial
                  institutions (the "Lenders") listed on the signature pages
                  thereof, Citibank, N.A., as syndication agent for the Lenders,
                  Chase Bank of Texas, N.A. ("Chase" and, in its capacity as
                  administrative agent for the Lenders, the "Administrative
                  Agent"), The Chase Manhattan Bank, as auction administrative
                  agent for the Lenders (in such capacity, the "Auction
                  Administrative Agent"), and Bank of America, N.A. and Fleet
                  National Bank, as co-documentation agents for the Lenders.

         The Borrower has advised the Lenders that it desires to amend the
Credit Agreement to (i) conform the affirmative maintenance of existence
covenant to certain of its other material agreements and the existing merger
covenant by permitting conversions of Material Subsidiaries (such term and each
other capitalized term used and not otherwise defined herein having the meaning
assigned to it in the Credit Agreement as amended hereby) into non-corporate
forms and (ii) update the references to certain outdated tax forms, and has
requested in connection therewith that the Credit Agreement be amended as set
forth in Section 1 below. The parties hereto are willing so to amend the Credit
Agreement.

         In consideration of the premises and the agreements, provisions and
covenants herein contained, the parties hereto hereby agree, on the terms and
subject to the conditions set forth herein, as follows:

         SECTION 1. Amendment. Upon the effectiveness of this Amendment as
provided in Section 3 below, the Credit Agreement shall be amended as follows:

                  (i) Paragraph (a) of Section 5.01 of the Credit Agreement is
         hereby deleted in its entirety and replaced with the following:

                           "(a) PRESERVATION OF CORPORATE EXISTENCE, ETC.
                  Preserve and maintain, and cause each Material Subsidiary to
                  preserve and maintain, its existence, rights (organizational
                  and statutory) and material franchises, except as otherwise
                  contemplated or permitted by Section 5.02(c) or 5.02(d);
                  provided, that any Material Subsidiary may change its form of
                  organization to a partnership or other form of Business
                  Entity."
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                  (ii) Section 2.15 of the Credit Agreement is hereby amended by
         replacing (a) each reference to "form 1001" in such Section with the
         words "form W-8BEN" and (b) each reference to "form 4224" in such
         Section with the words "form W-8ECI".

         SECTION 2. Representations and Warranties. The Borrower represents and
warrants as of the effective date of this Amendment to each of the Lenders that:

                  (a) Immediately before and immediately after giving effect to
         this Amendment, the representation and warranties set forth in the
         Credit Agreement are true and correct in all material respects with the
         same effect as if made on the effective date hereof, except to the
         extent such representations and warranties expressly relate to an
         earlier date.

                  (b) Immediately before and immediately after giving effect to
         this Amendment, no Event of Default or Default has occurred and is
         continuing.

         SECTION 3. Conditions of Effectiveness. This Amendment shall become
effective as of the date hereof when Chase shall have received counterparts of
this Amendment that, when taken together, bear the signatures of the Borrower,
the Administrative Agent, Chase and the Majority Lenders.

         SECTION 4. Agreement. Except as specifically stated herein, the
provisions of the Credit Agreement are and shall remain in full force and
effect. As used therein, the terms "Credit Agreement", "herein", "hereunder",
"hereinafter", "hereto", "hereof" and words of similar import shall, unless the
context otherwise requires, refer to the Credit Agreement as amended hereby.

         SECTION 5. APPLICABLE LAW. THIS AMENDMENT SHALL BE GOVERNED BY, AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE SATE OF NEW YORK.

         SECTION 6. Counterparts. This Amendment may be executed in two or more
counterparts, each of which shall constitute an original but all of which when
taken together shall constitute but one contract.

         SECTION 7. Expenses. The Borrower agrees to reimburse the
Administrative Agent for all out-of-pocket expenses incurred by it in connection
with this Amendment, including the reasonable fees, charges and disbursements of
Cravath, Swaine & Moore, counsel for the Administrative Agent.


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

                                        BURLINGTON RESOURCES INC.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        CHASE BANK OF TEXAS, N.A., as
                                        Administrative Agent


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        CITIBANK, N.A., as Syndication Agent


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        BANK OF AMERICA NATIONAL TRUST AND
                                        SAVINGS ASSOCIATION, as
                                        Documentation Agent


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:







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                                        FLEET NATIONAL BANK,
                                        as Documentation Agent


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:








<PAGE>   5
         The Lenders



                                        CHASE BANK OF TEXAS, N.A.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        CITIBANK, N.A.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        BANK OF AMERICA NATIONAL TRUST AND
                                        SAVINGS ASSOCIATION


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        FLEET NATIONAL BANK


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        MELLON BANK, N.A.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


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                                        WELLS FARGO BANK


                                        By:
                                            ------------------------------------
                                                 Name:
                                                 Title:


                                        THE BANK OF NEW YORK


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        THE BANK OF TOKYO-MITSUBISHI, LTD.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        THE NORTHERN TRUST COMPANY


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        WACHOVIA BANK, N.A.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:





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                                        NATIONSBANK, N.A.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        PARIBAS


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        BANK OF MONTREAL


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        BARCLAYS BANK PLC


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                                        DEUTSCHE BANK


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:


                             Name of Institution:
                                                 -------------------------------


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title:
<PAGE>   8

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


                                        BURLINGTON RESOURCES INC.


                                        By:
                                           -------------------------------------
                                                 Name:
                                                 Title: