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                                                                  EXHIBIT 10.1.2


        FIRST AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT AGREEMENT
        ---------------------------------------------------------------

     This First Amendment to Second Amended and Restated Credit Agreement (this
First Amendment) is executed as of the 25th day of October, 1999, by and among
---------------
Patina Oil & Gas Corporation, a Delaware Corporation (Borrower), Chase Bank of
                                                      --------
Texas, National Association, as Administrative Agent (Administrative Agent), and
                                                      --------------------
the financial institutions parties hereto as Banks (individually a Bank and
                                                                   ----
collectively Banks).
             -----

                                 W I T N E S E T H:
                                 - - - - - - - - -

     WHEREAS, Borrower, Administrative Agent and Banks are parties to that
certain Second Amended and Restated Credit Agreement dated as of July 15, 1999
(as amended, the Credit Agreement) (unless otherwise defined herein, all terms
                 ----------------
used herein with their initial letter capitalized shall have the meaning given
such terms in the Credit Agreement); and

     WHEREAS, pursuant to the Credit Agreement, Banks have made a revolving
credit loan to Borrower; and

     WHEREAS, Borrower has (a) notified Administrative Agent and Banks that
effective  October 25, 1999 Borrower redeemed 623,000 shares of its Original
Preferred Stock, 457,000 shares of which were redeemed for $12,000,000 in cash,
and (b) requested that the Credit Agreement be amended to revise Section 10.2
thereof as set forth herein in connection therewith; and

     WHEREAS, Borrower and Banks desire to set forth herein the amount of the
Borrowing Base for the period commencing on November 1, 1999 and continuing
until the next succeeding Determination Date.

     NOW THEREFORE, for and in consideration of the mutual covenants and
agreements herein contained and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged and confessed,
Borrower, Administrative Agent and each Bank hereby agree as follows:

     SECTION 1.  Amendments.  In reliance on the representations, warranties,
     ---------   ----------
covenants and agreements contained in this First Amendment and subject to the
terms and conditions set forth herein, the Credit Agreement shall be amended
effective as of the date hereof in the manner provided in this Section 1.
                                                               ---------

     1.1. Amendment to Definition.  The definition of Loan Papers contained in
          -----------------------                     -----------
Section 2.1 of the Credit Agreement shall be amended to read in full as follows:

          Loan Papers means this Agreement, the First Amendment, the Notes, each
          -----------
     Restricted Subsidiary Guarantee now or hereafter executed, each Restricted
     Subsidiary Pledge Agreement now or hereafter executed, all Mortgages now or
     at any time hereafter delivered pursuant to Section 6.1, the Collateral
                                                 -----------
     Assignment, and all other certificates, documents or instruments delivered
     in connection with this Agreement, as the foregoing may be amended from
     time to time.

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     1.2. Additional Definitions.  Section 2.1 of the Credit Agreement shall be
          ----------------------
amended to add the following definitions to such Section:

          First Amendment means the First Amendment to Second Amended and
          ---------------
     Restated Credit Agreement dated as of October 25, 1999, entered into by and
     among Borrower, Administrative Agent and Banks.

          Qualified Redemption means a one-time redemption by Borrower of
          --------------------
     623,000 shares of the Original Preferred Stock, of which (i) 166,000 shares
     are converted into 482,000 shares of Common Stock, and (ii) 457,000 shares
     are redeemed for $12,000,000 in cash, and which redemption shall (a) be
     pursuant to a Redemption Notice delivered by Borrower not more than ninety
     (90) days and not less than thirty (30) days prior to October 25, 1999, and
     (b) be effective October 25, 1999.

          Redemption Notice means a notice by Borrower to the holders of the
          -----------------
     Original Preferred Stock, pursuant to which Borrower calls 623,000 shares
     of such Original Preferred Stock for redemption.

     1.3. Amendment to Restricted Payments Covenant.  Section 10.2 of the
          -----------------------------------------
Credit Agreement shall be amended to read in full as follows:

          SECTION 10.2.   Restricted Payments.  Neither Borrower nor any
                          -------------------
          Restricted Subsidiary of Borrower will declare or make any Restricted
          Payment; provided, that, so long as no Default, Event of Default or
                   --------  ----
          Borrowing Base Deficiency then exists, and provided that no Default or
          Event of Default would result therefrom, Borrower shall be permitted
          to (a) declare and pay accrued dividends on the Preferred Stock and
          the Common Stock, (b) repurchase any of its Common Stock or Preferred
          Stock or warrants, options or other rights to acquire such Common
          Stock or Preferred Stock, so long as, at any date, the sum of (y) the
          aggregate amount of all such dividends declared and paid pursuant to
          clause (a) above during the period commencing on April 1, 1999 to and
          including such date, plus (z) the aggregate amount paid by Borrower
          and its Restricted Subsidiaries in respect of the repurchase of all
          such Common Stock or Preferred Stock or warrants, options or other
          rights to acquire such Common Stock or Preferred Stock pursuant to
          clause (b) above, shall not exceed the Restricted Payment Limit in
          effect at such date, and (c) notwithstanding anything to the contrary
          contained herein, consummate and effectuate the Qualified Redemption,
          which such Qualified Redemption shall not impact or be counted against
          the Restricted Payment Limit.

     SECTION 2.  Borrowing Base.  In accordance with Article V of the Credit
     ---------   --------------
Agreement, effective November 1, 1999, and continuing until the next
Determination Date, the Borrowing Base shall be $175,000,000.

     SECTION 3.  Consent.  Notwithstanding anything to the contrary contained in
     ---------   -------
the Credit Agreement or in any other Loan Paper, Banks hereby (a) consent to the
consummation of the Qualified Redemption, and (b) waive any inconsistent
provisions of the Credit Agreement,

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including, without limitation, Section 10.2 thereof, with respect to the
consummation of such Qualified Redemption. The consent and waiver herein
contained are expressly limited as follows: (i) such consent and waiver are
limited solely to the consummation of the Qualified Redemption, (ii) such
consent and waiver shall not be applicable to any provision of any Loan Paper
other than Section 10.2 of the Credit Agreement, and (iii) such consent and
waiver are each a limited, one-time consent and waiver, and nothing contained
herein shall obligate Banks to grant any additional or future consent or waiver
of, or with respect to, Section 10.2 of the Credit Agreement or any other
provision of any Loan Paper.

     SECTION 4.  Representations and Warranties.  In order to induce
     ---------   ------------------------------
Administrative Agent and Banks to enter into this First Amendment, Borrower
hereby represents and warrants to Administrative Agent and each Bank that:

     4.1. Accuracy of Representations and Warranties.  Each representation and
          ------------------------------------------
warranty of Borrower and its Subsidiaries contained in the Loan Papers are true
and correct in all material respects as of the date hereof (except to the extent
that such representations and warranties are expressly made as of a particular
date, in which event such representations and warranties were true and correct
as of such date);

     4.2. Absence of Defaults.  Neither a Default nor an Event of Default has
          -------------------
occurred which is continuing; and

     4.3. No Defense.  Borrower has no defenses to payment, counterclaims or
          ----------
rights of set-off with respect to the Obligations on the date hereof.

     SECTION 5.  Miscellaneous.
     ---------   -------------

     5.1. Reaffirmation of Loan Papers; Extension of Liens.  Any and all of the
          ------------------------------------------------
terms and provisions of the Credit Agreement and the Loan Papers shall, except
as amended and modified hereby, remain in full force and effect.  Borrower
hereby extends the Liens securing the Obligations until the Obligations have
been paid in full, and agrees that the amendments and modifications herein
contained shall in no manner affect or impair the Obligations or the Liens
securing payment and performance thereof.

     5.2. Parties in Interest.  All of the terms and provisions of this First
          -------------------
Amendment shall bind and inure to the benefit of the parties hereto and their
respective successors and assigns.

     5.3. Counterparts.  This First Amendment may be executed in counterparts,
          ------------
and all parties need not execute the same counterpart; however, no party shall
be bound by this First Amendment until this First Amendment has been executed by
Borrower, Administrative Agent and all Banks at which time this First Amendment
shall be binding on, enforceable against and inure to the benefit of Borrower,
Administrative Agent and all Banks.  Facsimiles shall be effective as originals.

     5.4. COMPLETE AGREEMENT.  THIS FIRST AMENDMENT, THE CREDIT AGREEMENT AND
          ------------------
THE OTHER LOAN PAPERS REPRESENT THE FINAL AGREEMENT AMONG THE PARTIES AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,

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CONTEMPORANEOUS OR ORAL AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL
AGREEMENTS BETWEEN THE PARTIES.

     5.5. Headings.  The headings, captions and arrangements used in this First
          --------
Amendment are, unless specified otherwise, for convenience only and shall not be
deemed to limit, amplify or modify the terms of this First Amendment, nor affect
the meaning thereof.

     5.6. Legal Expenses.  Borrower hereby agrees to pay on demand all
          --------------
reasonable fees and expenses of counsel to Administrative Agent incurred by
Administrative Agent in connection with the preparation, negotiation and
execution of this First Amendment and all related documents.

     IN WITNESS WHEREOF, the parties hereto have caused this First Amendment to
be duly executed by their respective Authorized Officers on the date and year
first above written.

                                 [Signature Pages Follow]

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SIGNATURE PAGE TO FIRST AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT
AGREEMENT DATED AS OF NOVEMBER 1, 1999, BY AND AMONG PATINA OIL & GAS
CORPORATION, AS BORROWER, THE FINANCIAL INSTITUTIONS PARTIES THERETO, AS BANKS,
AND CHASE BANK OF TEXAS, NATIONAL ASSOCIATION, AS ADMINISTRATIVE AGENT


                                    PATINA OIL & GAS CORPORATION

                                    By: /s/ David J. Kornder
                                        --------------------------------------
                                        David J. Kornder, Vice President and
                                        Chief Financial Officer



                                    CHASE BANK OF TEXAS, NATIONAL
                                    ASSOCIATION, as Administrative Agent

                                    By: /s/ Dale S. Hurd
                                        --------------------------------------
                                        Dale S. Hurd, Managing Director



                                    CHASE BANK OF TEXAS, NATIONAL
                                    ASSOCIATION, as a Bank

                                    By: /s/ Dale S. Hurd
                                        --------------------------------------
                                        Dale S. Hurd, Managing Director


                                    BANK OF AMERICA, N.A., as a Bank

                                    By: /s/ J. Scott Fowler
                                        --------------------------------------
                                        J. Scott Fowler, Managing Director


                                    BANK ONE, NA
                                    (MAIN OFFICE - CHICAGO) as a Bank
                                    (FORMERLY KNOWN AS THE FIRST
                                    NATIONAL BANK OF CHICAGO)

                                    By: /s/ Carl Skoog
                                        --------------------------------------
                                         Carl Skoog, Vice President

                                       5
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SIGNATURE PAGE TO FIRST AMENDMENT TO SECOND AMENDED AND RESTATED CREDIT
AGREEMENT DATED AS OF NOVEMBER 1, 1999, BY AND AMONG PATINA OIL & GAS
CORPORATION, AS BORROWER, THE FINANCIAL INSTITUTIONS PARTIES THERETO, AS BANKS,
AND CHASE BANK OF TEXAS, NATIONAL ASSOCIATION, AS ADMINISTRATIVE AGENT


                                    BANKERS TRUST COMPANY, as a Bank

                                    By: /s/ Calli S. Hayes
                                        --------------------------------------
                                        Calli S. Hayes, Managing Director



                                    CREDIT LYONNAIS NEW YORK BRANCH

                                    By: /s/ Phillipe Soustra
                                        --------------------------------------
                                        Phillipe Soustra, Senior Vice President



                                    FIRST UNION NATIONAL BANK

                                    By: /s/ Robert R. Wetteroff
                                        -------------------------------------
                                        Robert R. Wetteroff, Senior V.P.



                                    WELLS FARGO BANK, N.A.


                                    By: /s/ Greg Petruska
                                        -------------------------------------
                                        Greg Petruska, Vice President

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