<PAGE>

                                                                  EXHIBIT 10.25


                                                                EXECUTION COPY

                                    FIRST AMENDMENT dated as of March 2, 1998
                           (this "Amendment"), among UNION PACIFIC RESOURCES
                           GROUP INC., a Utah corporation (the "Borrower"), the
                           undersigned financial institutions party to the
                           Credit Agreement referred to below (the "Banks"),
                           CHASE BANK OF TEXAS, N.A., as administrative agent
                           for the Banks (in such capacity, the "Administrative
                           Agent"), THE CHASE MANHATTAN BANK, as auction
                           administration agent (in such capacity, the "Auction
                           Administration Agent"), BANK OF AMERICA NT&SA, as
                           documentation agent (in such capacity, the
                           "Documentation Agent") and NATIONSBANK OF TEXAS,
                           N.A., as syndication agent (in such capacity, the
                           "Syndication Agent").

                  A. Reference is made to the 364 Day Competitive
Advance/Revolving Credit Agreement dated as of November 25, 1997 (the "Credit
Agreement"), among the Borrower, the Banks, the Administrative Agent, the
Auction Administration Agent, the Documentation Agent and the Syndication Agent.
Capitalized terms used but not otherwise defined herein have the meanings
assigned to them in the Credit Agreement.

                  B. The Borrower has requested that the Banks amend certain
provisions of the Credit Agreement. The Banks are willing to do so, subject to
the terms and conditions of this Amendment.

                  Accordingly, in consideration of the mutual agreements herein
contained and other good and valuable consideration, the sufficiency and receipt
of which are hereby acknowledged, the parties hereto hereby agree as follows:

                  SECTION 1. Amendment to Article I. (a) The definition of
"Existing Credit Agreements" contained in Article I of the Credit Agreement is
hereby replaced in its entirety with the following: "Existing Credit Agreements"
means collectively (a) the Competitive Advance/Revolving Credit Agreement, dated
as of April 16, 1996 (as amended, extended, renewed or restated from time to
time), among the Borrower, Chase Bank of Texas, N.A., as administrative agent,
The Chase Manhattan Bank, as auction administration agent, Bank of America
NT&SA, as documentation agent, NationsBank of Texas, N.A., as syndication agent
and the banks party thereto and (b) the 364 Day Competitive Advance/Revolving
Credit Agreement (as amended, extended,



<PAGE>


                                                                               2



renewed or restated from time to time), to be entered into in March 1998 among
the Borrower, The Chase Manhattan Bank, as administrative agent, Bank of
Montreal, as syndication agent and the banks party thereto.

         (b) The following new definitions are hereby added to Article I of the
Credit Agreement in their proper alphabetical order:

                  (i) "Acquisition Subsidiary" means Union Pacific Resources
         Inc., a Canadian corporation and wholly owned Subsidiary of the
         Borrower.

                  (ii) "Designated Subsidiary" has the meaning specified in
         Section 5.02(b)(ii).

                  (iii) "Effective Date" means the closing date under the
         Existing Credit Agreement referred to in clause (b) of the definition
         of "Existing Credit Agreements".

                  (iv) "Material Debt" has the meaning specified in Section
         6.01(e).

                  (v)  "Norcen" means Norcen Energy Resources Limited, a
         Canadian corporation.

                  SECTION 2. Amendment to Section 4.01(g). Section 4.01(g) of
the Credit Agreement is hereby amended by replacing the reference to
"5.02(a)(i)" with "5.02(a)".

                  SECTION 3. Amendment to Section 5.02(a)(i). Section 5.02(a)(i)
of the Credit Agreement is hereby amended by (a) inserting immediately after the
reference to "paragraph (i)" therein "(A)" and (b) inserting at the end thereof
"and (B) so long as Norcen's capital stock constitutes margin stock (within the
meaning of Regulation U issued by the Board of Governors of the Federal Reserve
System), such portion (but only such portion) of Norcen's capital stock as it
shall be necessary to exclude from the operation of this paragraph in order to
avoid margin stock constituting more than 25% of the value of all assets subject
to this Section 5.02(a)".

                  SECTION 4. Amendment to Section 5.02(b). Section 5.02(b) of
the Credit Agreement is hereby replaced in its entirety with the following:


<PAGE>


                                                                               3

                  (b) Debt. (i) Create or suffer to exist any Debt if,
         immediately after giving effect to such Debt and the receipt and
         application of any proceeds thereof, the aggregate amount of Debt of
         the Borrower and its consolidated Subsidiaries, on a consolidated
         basis, would exceed (A) for the period from the Effective Date through
         the date eighteen months thereafter, 75%, and (B) at anytime

         thereafter, 65%, of the sum of the total consolidated stockholders'
         equity of the Borrower and its Subsidiaries as shown on the most recent
         consolidated balance sheet required to be delivered to the Banks
         pursuant to Section 5.01(b), and the aggregate amount of Debt of the
         Borrower and its consolidated Subsidiaries, on a consolidated basis (it
         being understood that for purposes of determining compliance with this
         covenant, guarantees by the Borrower of up to $200,000,000 of Debt of
         OCI Wyoming shall not constitute Debt of the Borrower);

                  (ii) not permit the Acquisition Subsidiary, Norcen or any of
         their respective Subsidiaries (collectively, the "Designated
         Subsidiaries") to incur any Debt which would result in the aggregate
         principal amount of Debt (other than Debt to the Borrower or any other
         Subsidiary) of all the Designated Subsidiaries, on a consolidated
         basis, exceeding US$1,400,000,000; and

                  (iii) not permit any of its Subsidiaries (other than the
         Designated Subsidiaries) to incur any Debt which would result in the
         aggregate principal amount of Debt (other than Debt to the Borrower or
         any other Subsidiary) of all Subsidiaries (other than the Designated
         Subsidiaries), on a consolidated basis, exceeding US$150,000,000.

                  SECTION 5.  Amendment to Section 5.02(e).  Section 
                              ---------------------------- 
5.02(e) of the Credit Agreement is hereby amended by (a) inserting a "(ii)"
immediately after the word "plus" therein, (b) replacing the reference to "65%"
with "(A) 75% during the period from the Effective Date through the date
eighteen months thereafter and (B) 65% at any time thereafter" and (c) inserting
the following sentence at the end thereof:  "For purposes of determining
compliance with the above covenant, guarantees by the Borrower of up to
$200,000,000 of Debt of OCI Wyoming shall not constitute Debt of the Borrower.".



<PAGE>


                                                                              4

                  Section 6. Amendment to Section 6.01. Section 6.01(e) of the
Credit Agreement is hereby replaced in its entirety with the following:

                  (e)(i) the Borrower or any Principal Subsidiary shall fail to
         pay any amount of principal or interest when due (or within any
         applicable grace period) with respect to any Debt of the Borrower or
         any Principal Subsidiary, whether such Debt now exists or shall
         hereafter be created, in an aggregate outstanding principal amount
         exceeding $50,000,000 ("Material Debt") or (ii) an event of default as
         defined in any mortgage, indenture or instrument under which there may
         be issued, or by which there may be secured or evidenced, any Debt of
         the Borrower or any Principal Subsidiary, whether such Debt now exists
         or shall hereafter be created, shall happen and shall result in
         Material Debt becoming or being declared due and payable prior to the
         date on which it would otherwise become due and payable, and such

         declaration shall not be rescinded or annulled; or

                  SECTION 7.  Principal Subsidiaries.  Schedule II to the Credit
Agreement is hereby replaced in its entirety by the Schedule II  attached
hereto.

                  SECTION 8.  Representations, Warranties and Agreements.  The
Borrower hereby represents and warrants to and agrees with each Bank, the
Administrative Agent, the Auction Administration Agent, the Documentation Agent
and the Syndication Agent that:

                  (a) The representations and warranties set forth in Section
         4.01 of the Credit Agreement, as amended hereby, are true and correct
         in all material respects with the same effect as if made on the
         Amendment Effective Date (as defined herein), except to the extent such
         representations and warranties expressly relate to an earlier date.

                  (b) The Borrower has the requisite power and authority to
         execute, deliver and perform its obligations under this Amendment.

                  (c) The execution, delivery and performance by the Borrower of
         this Amendment (i) have been duly authorized by all requisite action
         and (ii) will not (A) violate (x) any provision of law, statute, rule
         or regulation, or of the certificate of incorporation, by-


<PAGE>

                                                                              5 

         laws or other constitutive documents of the Borrower or any of its
         Subsidiaries, (y) any order of any governmental court or governmental
         department, commission, board, bureau, agency or instrumentality,
         domestic or foreign or (z) any provision of any indenture, any
         agreement for borrowed money or any other material agreement or
         instrument to which the Borrower or any of its Subsidiaries is a party
         or by which any of them or any of their property is or may be bound,
         (B) be in conflict with, result in a breach of or constitute (alone or
         with notice or lapse of time or both) a default under any such
         indenture, agreement for borrowed money or other material agreement or
         instrument or (C) result in the creation or imposition of any Lien upon
         or with respect to any property or assets now owned or hereafter
         acquired by the Borrower or any of its Subsidiaries.

                  (d) This Amendment has been duly executed and delivered by the
         Borrower. This Amendment and the Credit Agreement, as amended hereby,
         constitutes a legal, valid and binding obligation of the Borrower,
         enforceable against the Borrower in accordance with its terms, except
         as enforceability may be limited by (i) any applicable bankruptcy,
         insolvency, reorganization, moratorium or similar laws affecting the
         enforcement of creditors' rights generally and (ii) general principles
         of equity.

                  (e) As of the Amendment Effective Date, no Event of Default or

         any event which, with the giving of notice or the passage of time, or
         both, would become an Event of Default has occurred and is continuing.

                  SECTION 9. Conditions to Effectiveness. This Amendment shall
become effective on the date (the "Amendment Effective Date") that each of the
following conditions has been satisfied:

                  (a) The Administrative Agent shall have received duly executed
         counterparts hereof which, when taken together, bear the authorized
         signatures of the Borrower, the Administrative Agent, the Auction
         Administration Agent, the Documentation Agent, the Syndication Agent
         and the Majority Banks.

                  (b) The Effective Date occurs.


<PAGE>


                                                                              6

                  SECTION 10. Credit Agreement. Except as specifically stated
herein, the Credit Agreement shall continue in full force and effect in
accordance with the provisions thereof. As used therein, the terms "Agreement",
"herein", "hereunder", "hereto", "hereof" and words similar import shall, unless
the context otherwise requires, refer to the Credit Agreement as modified
hereby.

                  SECTION 11.  Applicable Law.  THIS AMENDMENT SHALL BE GOVERNED
BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

                  SECTION 12.  Counterparts.  This Amendment may be executed in
any number of counterparts, each of which shall be an original but all of which,
when taken together, shall constitute but one instrument.

                  SECTION 13. Expenses. The Borrower agrees to reimburse the
Administrative Agent for its out-of-pocket expenses in connection with this
Amendment, including the reasonable fees, charges and disbursements of Cravath,
Swaine & Moore, counsel for the Administrative Agent.

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

                                            UNION PACIFIC RESOURCES GROUP INC.

                                                  by

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

                                            CHASE BANK OF TEXAS, N.A., as


                                            Administrative Agent and as a Bank

                                                  by

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


<PAGE>


                                                                              7

                                            BANK OF AMERICA NT&SA, as
                                            Documentation Agent and as a Bank

                                                by

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

                                            NATIONSBANK OF TEXAS, N.A., as
                                            Syndication Agent and as a Bank

                                                by

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

                                            THE CHASE MANHATTAN BANK, as
                                            Auction Administrative Agent

                                                by

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

                                            ABN AMRO BANK N.V., HOUSTON AGENCY

                                            By:  ABN AMRO North America, Inc.,
                                            as Agent

                                                by

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

                                                by


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


<PAGE>


                                                                              8

                                            BANQUE NATIONALE DE PARIS,

                                            HOUSTON AGENCY

                                                by

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

                                            BANK OF MONTREAL

                                                by

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

                                            BANK OF NEW YORK

                                                by

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

                                            CREDIT SUISSE FIRST BOSTON

                                                by

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

                                                by

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

                                            THE FIRST NATIONAL BANK OF CHICAGO

                                                by


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


<PAGE>


                                                                              9

                                            THE INDUSTRIAL BANK OF JAPAN, LTD.,
                                            NEW YORK BRANCH

                                                by

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

                                            MELLON BANK, N.A.

                                                by

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

                                            THE NORTHERN TRUST COMPANY

                                                by

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

                                            ROYAL BANK OF CANADA

                                                by

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

                                            WELLS FARGO BANK (TEXAS), N.A.

                                                by

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


<PAGE>



                                                                              10

                                                                     Schedule II

                            Principal Subsidiaries

     1. Union Pacific Resources Company
     2. UP Fuels Marketing and Trading, Inc.
     3. Rock Springs Royalty Company
     4. Bitter Creek Coal Company
     5. Union Pacific Resources Inc.
     6. Norcen Energy Resources Limited