<PAGE>

                                                                 EXECUTION COPY

                                    THIRD 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 Competitive Advance/Revolving
Credit Agreement dated as of April 16, 1996, as amended (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
following amendments are made to the definitions contained
in Article I of the Credit Agreement:



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                                                                              2

                  (i) The definition of "Applicable Margin" is hereby amended
         by (A) replacing the reference to "Category 5" with "Category 6" in
         clause (i) thereof, (B) replacing Category 5 in its entirety as set
         forth below and (C) inserting the following Category 6:


<TABLE>
<CAPTION>
                                         Applicable              Applicable
                                         Margin for              Margin for
                                         Adjusted                Eurodollar             Applicable

                                         CD Rate                 Rate                   Margin for
                                         Contract                Contract               Facility
                 Ratings                 Borrowings              Borrowings             Fees
<S>                                      <C>                     <C>                    <C>
               Category 5

               BBB by S&P;

                                         .35%                    .225%                  .15%
             Baa2 by Moody's

               Category 6

            Lower than BBB by            .425%                   .30%                   .15%
           S&P;

           Lower than Baa2 by
           Moody's
</TABLE>

                  (ii) The definition of "Existing Credit Agreements" is hereby
         replaced in its entirety with the following: "Existing Credit
         Agreements" means collectively (a) the 364 Day Competitive
         Advance/Revolving Credit Agreement, dated as of November 25, 1997 (as
         amended, extended, renewed or restated from time to time), among the
         Borrower, Texas Commerce Bank National Association, 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,
         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.



<PAGE>


                                                                              3

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

                  (b) Section 4.01 of the Credit Agreement is hereby amended by
inserting the following:

         (m) No "Event of Default" under either of the Existing Credit
         Agreements or any event or existence of any circumstance which, with
         the giving of notice or lapse of time or both, would become an Event of
         Default under either of the Existing Credit Agreements exists.

                  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(a)(ii).
Section 5.02(a)(ii) of the Credit Agreement is hereby



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                                                                              4

amended by (a) deleting the "and" immediately after the ";" in clause (F), (b)
inserting a new clause (G) that reads as follows: "any Liens securing Debt of
Borrower under the Existing Credit Agreements, so long as the Banks are granted
Liens of equal priority upon any property to which such Liens under the Existing
Credit Agreements attach; and", (c) replacing the reference to "(G)" with "(H)"
and (d) replacing the reference to "(E)" in clause (G) with "(G)".

                  SECTION 5. Amendment to Section 5.02(b). Section 5.02(b) of
the Credit Agreement is hereby replaced in its entirety with the following:

                  (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 6.  Amendment to Section 5.02(e).  Section 5.02(e) 
of the Credit Agreement is hereby amended by (a)



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                                                                              5

replacing the reference to "65%" with "(I) 75% during the period from the
Effective Date through the date eighteen months thereafter and (II) 65% at any
time thereafter" and (b) 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.".

                  Section 7. Amendment to Section 6.01.  (a) 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

                  (b) Section 6.01 of the Credit Agreement is hereby amended by
(a) inserting an "or" immediately after the ";" in clause (h) and (b) inserting
the following clause immediately after the "or" at the end of clause (h): "(i)
any "Event of Default" described in either of the Existing Credit Agreements
shall occur;".

                  SECTION 9.  Principal Subsidiaries.  Schedule II to the 
Credit Agreement is hereby replaced in its entirety by the Schedule II 
attached hereto.

                  SECTION 10.  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



<PAGE>


                                                                              6

         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-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.



<PAGE>


                                                                              7

                  SECTION 11. 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.

                  SECTION 12. 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 13.  Applicable Law.  THIS AMENDMENT SHALL BE 
GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

                  SECTION 14.  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 15. 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.



<PAGE>



                                                                              8

                  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:

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

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

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

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

                                            THE CHASE MANHATTAN BANK, as
                                            Auction Administration Agent

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



<PAGE>


                                                                              9


                                            NATIONAL WESTMINSTER BANK, PLC

                                            NEW YORK BRANCH

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

                                            NASSAU BRANCH

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

                                            ABN AMRO BANK N.V., HOUSTON AGENCY
                                            By:  ABN AMRO North America, Inc.,
                                            as Agent

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

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

                                            BANK OF MONTREAL

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

                                            ROYAL BANK OF CANADA

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



<PAGE>


                                                                              10



                                            CREDIT LYONNAIS NEW YORK BRANCH


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

                                            CREDIT SUISSE FIRST BOSTON

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

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

                                            THE FIRST NATIONAL BANK OF CHICAGO

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

                                            MELLON BANK, N.A.

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

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

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



<PAGE>


                                                                              11

                                                                     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