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                               FIRST AMENDMENT OF
                      AMENDED AND RESTATED CREDIT AGREEMENT

     THIS FIRST AMENDMENT OF AMENDED AND RESTATED CREDIT AGREEMENT (this
"Amendment"), dated as of July 1, 1999, is by and among BASIN EXPLORATION,
INC., a Delaware corporation ("Borrower"), U.S. BANK NATIONAL ASSOCIATION
f/k/a COLORADO NATIONAL BANK ("USB"), UNION BANK OF CALIFORNIA, N.A.
("Union"), and NATIONSBANK, N.A. f/k/a NATIONSBANK OF TEXAS, N.A. ("NBT"), in
its capacity as a Lender and as Agent for Lenders. USB, Union and NBT are
herein collectively referred to as "Lenders."

                                    RECITALS

         A. Borrower and Lenders entered into an Amended and Restated Credit
Agreement dated as of January 1, 1999 (the "Credit Agreement"), in order to
set forth the terms upon which Lenders would make loans to Borrower and issue
letters of credit at the request of Borrower and by which such loans and
letters of credit would be governed. Capitalized terms used herein without
definition shall have the same meanings as set forth in the Credit Agreement.

         B. The parties hereto wish to enter into this Amendment in order to
amend certain terms and provisions of the Credit Agreement.

                                    AGREEMENT

     NOW, THEREFORE, in consideration of $10.00 and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
the parties hereby agree as follows:

         1. CREDIT AGREEMENT. Effective as of the date of this Amendment, the
Credit Agreement shall be, and hereby is, amended as follows:

              (a) The definition of "Borrowing Base (Supplemental)" in
Section 1.1 on page 3 of the Credit Agreement shall be deleted, and the
following shall be substituted therefor:

               BORROWING BASE (SUPPLEMENTAL) means that portion of the Borrowing
          Base attributable to Facility B, which shall be: (a) at any time prior
          to July 1, 1999, the supplemental loan value attributable to the
          Borrowing Base Properties, as determined by Lenders in their sole and
          absolute discretion, in accordance with the procedures for
          supplemental oil and gas borrowing base loans set forth in Section 3.2
          below; and (b) at any time on or after July 1, 1999, zero.

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               (b) The definition of "Commitment Expiration Date (Facility
B)" in Section 1.1 on page 4 of the Credit Agreement shall be deleted, and
the following shall be substituted therefor:

               "COMMITMENT EXPIRATION DATE (FACILITY B)" means the date after
          which no further Advances under Facility B are to be made hereunder,
          which shall be the close of business on June 30, 1999.

               (c) Section 3.2(a) on page 26 of the Credit Agreement shall be
deleted, and the following shall be substituted therefor:

                   (a) regular semi-annual determinations, as of approximately
          April 1 and October 1 of each year;

              2. LOAN DOCUMENT. All references in any document to the Credit
Agreement shall refer to the Credit Agreement, as amended and supplemented
pursuant to this Amendment.

              3. CONDITIONS PRECEDENT. The obligations of the parties under
this Amendment are subject, at the option of Lenders, to the prior
satisfaction of the condition that Borrower shall have executed and/or
delivered, or caused to have been executed and/or delivered, to or for the
benefit of Lenders, the following (all documents to be satisfactory in form
and substance to Lenders):

              (a) This Amendment.

              (b) Such certificates of officers of Borrower as may be
required by Lenders.

              (c) Any and all other Loan Documents required by Lenders,
including without limitation any and all Security Documents required by
Lenders.

              4. REPRESENTATIONS AND WARRANTIES. Borrower hereby certifies to
Lenders that as of the date of (and after giving effect to) this Amendment,
except as heretofore disclosed to and waived by Lenders: (a) all of
Borrower's representations and warranties contained in the Credit Agreement
are true, accurate and complete in all material respects, and (b) no Default
or Event of Default has occurred and is continuing under the Credit Agreement.

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              5. CONTINUATION OF THE CREDIT AGREEMENT. Except as specified in
this Amendment, the provisions of the Credit Agreement shall remain in full
force and effect, and if there is a conflict between the terms of this
Amendment and those of the Credit Agreement, the terms of this Amendment
shall control. Borrower hereby ratifies, confirms and adopts the Credit
Agreement, as amended hereby.

              6. EXPENSES. Borrower shall pay all reasonable expenses
incurred in connection with the transactions contemplated by this Amendment,
including without limitation all reasonable fees and reasonable expenses of
Lenders' attorneys and all recording and filing fees, charges and expenses.

              7. MISCELLANEOUS. This Amendment shall be governed by and
construed under the laws of the State of Colorado and shall be binding upon
and inure to the benefit of the parties hereto and their successors and
assigns. This Amendment may be executed in any number of counterparts, each
of which shall be an original, but all of which together shall constitute one
instrument. Delivery of this Amendment and any and all documents to be
delivered in connection herewith by any party may be effected, without
limitation, by faxing a signed counterpart of this Amendment to NBT (any
party that effects delivery in such manner hereby agreeing to transmit
promptly to NBT an actual signed counterpart).

              EXECUTED as of the date first above written.


                                       BASIN EXPLORATION, INC.


                                       By:
                                          --------------------------------
                                          Vice President/Chief Financial Officer



                                       NATIONSBANK, N.A. f/k/a NATIONSBANK
                                       OF TEXAS, N.A., in its capacity as
                                       Lender and as Agent for Lenders


                                       By:
                                          --------------------------------
                                          Managing Director



                                       U.S. BANK NATIONAL ASSOCIATION f/k/a
                                       COLORADO NATIONAL BANK


                                       By:
                                          --------------------------------
                                          Vice President


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                                       UNION BANK OF CALIFORNIA, N.A.


                                       By:
                                          --------------------------------
                                          Vice President

                                       By:
                                          --------------------------------
                                          Senior Vice President


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