EXHIBIT 4.45
                                                                    ------------



                                                                  EXECUTION COPY


                            THIRD AMENDING AGREEMENT
                            ------------------------


         THIS AGREEMENT dated effective as of July 29, 2003.

BETWEEN:

                  NEXEN INC., a corporation subsisting under the laws of Canada
                  (hereinafter referred to as the "BORROWER"),

                                                              OF THE FIRST PART,

                                     - and -


                  THE FINANCIAL INSTITUTIONS SET FORTH ON THE SIGNATURE PAGE
                  HEREOF UNDER THE HEADING "LENDERS:" (hereinafter collectively
                  referred to as the "Lenders" and sometimes individually
                  referred to as a "Lender"),

                                                             OF THE SECOND PART,

                                     - and -


                  THE TORONTO-DOMINION BANK, a Canadian chartered bank, as agent
                  of the Lenders (hereinafter referred to as the "AGENT"),

                                                              OF THE THIRD PART.


         WHEREAS the parties hereto entered into the Credit Agreement;

         AND WHEREAS the parties hereto have agreed to amend and supplement
certain provisions of the Credit Agreement as set out herein;

         AND WHEREAS the Lenders have agreed that the Agent execute this
Agreement on their behalf;

         NOW THEREFORE THIS AGREEMENT WITNESSES that in consideration of the
covenants and agreements herein contained and other good and valuable
consideration, the receipt and sufficiency of which are hereby conclusively
acknowledged by each of the parties hereto, the parties hereto covenant and
agree as follows:

1.

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                                      -2-

1.       INTERPRETATION

1.1      In this Agreement and the recitals hereto, unless something in the
subject matter or context is inconsistent therewith:

         "AGREEMENT" means this agreement, as amended, modified, supplemented or
         restated from time to time; and

         "CREDIT AGREEMENT" means the Restated Credit Agreement among the
         parties hereto originally made as of December 29, 1988 and amended and
         restated as of November 17, 2000, as amended by the First Amending
         Agreement made as of August 1, 2001 and by the Second Amending
         Agreement made as of July 31, 2002 and as otherwise amended,
         supplemented, modified or restated from time to time.

1.2      Capitalized terms used herein without express definition shall have the
same meanings herein as are ascribed thereto in the Credit Agreement.

1.3      The division of this Agreement into Sections and the insertion of
headings are for convenience of reference only and shall not affect the
construction or interpretation of this Agreement. The terms "this Agreement",
"hereof", "hereunder" and similar expressions refer to this Agreement and not to
any particular Section or other portion hereof and include any agreements
supplemental hereto.

1.4      This Agreement shall be governed by and construed in accordance with
the laws of the Province of Alberta and federal laws of Canada applicable
therein.

2.       AMENDMENTS

         The Credit Agreement is hereby amended as follows:

         (a)      the definition of "Credit Facility" in Section 1.1 is hereby
                  amended by deleting "$400,000,000" and substituting therefor
                  "$410,000,000";

         (b)      the definition of "Maturity Date" in Section 1.1 is hereby
                  amended by deleting the word "fourth" in the second line and
                  substituting therefor the word "third"; and

         (c)      Clause (a) of Section 2.17 is amended as follows:

                  (i)      by deleting the number "5" in the second line and
                           substituting therefor the number "4"; and

                  (ii)     by deleting the number "4" in the tenth line and
                           substituting therefor the number "3".

3.       ADDITION OF BNP PARIBAS AS LENDER

3.1      BNP PARIBAS AS LENDER. The parties hereto hereby confirm and agree
that, from and after the date hereof, BNP Paribas (Canada) ("BNP Paribas") shall
be a Lender for all purposes

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                                      -3-


of the Credit Agreement and the other Documents and all references therein to
"Lenders" or "a Lender" shall be deemed to include BNP Paribas.

3.2      BNP PARIBAS COMMITMENT. The parties hereto hereby confirm and agree
that, from and after the date hereof, the Commitment of BNP Paribas shall be
Cdn. $50,000,000.

3.3      NOVATION OF BNP PARIBAS. BNP Paribas hereby agrees that it will be
bound by the Credit Agreement and the other Documents as a Lender to the extent
of its aggregate Commitment as fully as if it had been an original party to the
Credit Agreement.

3.4      NOTICES. The parties hereto hereby confirm and agree that, from and
after the date hereof, any demand, notice or communication to be given to BNP
Paribas, as a Lender, in accordance with the provisions of the Credit Agreement
shall be made or given to BNP Paribas at the following address:

77 King Street West, Suite 4100
Toronto, Ontario
M5K 1N8

3.5      THE AGENT. Without in any way limiting the other provisions hereof, BNP
Paribas irrevocably appoints and authorizes the Agent to take such action as
agent on its behalf and to exercise such powers under the Credit Agreement and
the other Documents as are delegated to the Agent by the terms thereof, together
with such powers as are reasonably incidental thereto, all in accordance with
the provisions of the Credit Agreement.

3.6      BNP CREDIT DECISION. BNP Paribas acknowledges to the Agent that BNP
Paribas has itself been, and will continue to be, solely responsible for making
its own independent appraisal of and investigations into the financial
condition, creditworthiness, condition, affairs, status and nature of the
Borrower and its Subsidiaries, all of the matters and transactions contemplated
herein and in the Credit Agreement and other Documents and all other matters
incidental to the Credit Agreement and the other Documents. BNP Paribas confirms
with the Agent that it does not rely, and it will not hereafter rely, on the
Agent:

         (a)      to check or inquire on its behalf into the adequacy, accuracy
                  or completeness of any information provided by the Borrower,
                  its Subsidiaries or any other person under or in connection
                  with the Credit Agreement and other Documents or the
                  transactions therein contemplated (whether or not such
                  information has been or is hereafter distributed to BNP
                  Paribas by the Agent); or

         (b)      to assess or keep under review on its behalf the financial
                  condition, creditworthiness, condition, affairs, status or
                  nature of the Borrower and its Subsidiaries.

BNP Paribas further acknowledges to the Agent that a copy of the Credit
Agreement (including a copy of the Schedules annexed thereto) has been made
available to it for review and further acknowledges and agrees that it has
received copies of such other Documents and such other information that it has
requested for the purposes of its investigation and analysis of all matters
related to this Agreement, the Credit Agreement, the other Documents and the
transactions

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                                      -4-


contemplated hereby and thereby. BNP Paribas acknowledges to the Agent that it
is satisfied with the form and substance of the Credit Agreement and the other
Documents.

4.       INCREASE IN LOAN LIMIT; ADJUSTMENT OF LENDER COMMITMENTS AND
OUTSTANDING PRINCIPAL

4.1      Effective as of the date of this Agreement, the Loan Limit shall be and
is hereby increased from Cdn. $400,000,000 to Cdn. $410,000,000.

4.2      Effective as of the date of this Agreement, the revised Commitments of
each Lender shall be as set forth in Schedule A attached hereto. To evidence and
give effect to the foregoing, Schedule A (Lenders and Commitments) to the Credit
Agreement is hereby deleted in its entirety and the new Schedule A attached
hereto is substituted therefor. The Lenders hereby agree that on the effective
date of this Agreement and after giving effect to such change in Commitments,
each Lender is owed its amended Rateable Portion of all Outstanding Principal.

5.       REPRESENTATIONS AND WARRANTIES

5.1      The Borrower hereby represents and warrants as follows to each Lender
and the Agent and acknowledges and confirms that each Lender and the Agent is
relying upon such representations and warranties:

         (a)      Capacity, Power and Authority

                  (i)      The Borrower is duly incorporated and is validly
                           subsisting under the laws of its jurisdiction of
                           incorporation or creation and has all the requisite
                           corporate capacity, power and authority to carry on
                           its business as presently conducted and to own its
                           property; and

                  (ii)     The Borrower has the requisite corporate capacity,
                           power and authority to execute and deliver this
                           Agreement.

         (b)      Authorization; Execution; Enforceability

                  The Borrower has taken or caused to be taken all necessary
                  action to authorize, and has duly executed and delivered this
                  Agreement. This Agreement is a legal, valid and binding
                  obligation of the Borrower, enforceable against it in
                  accordance with its terms, subject to applicable bankruptcy,
                  reorganization, winding up, insolvency, moratorium or other
                  laws of general application affecting the enforcement of
                  creditors rights generally and to the equitable and statutory
                  powers of the courts having jurisdiction with respect thereto.

5.2      The representations and warranties set out in this Agreement shall
survive the execution and delivery of this Agreement and the making of each
Drawdown, notwithstanding any investigations or examinations which may be made
by the Agent, the Lenders or Lenders' counsel. Such representations and
warranties shall survive until the Credit Agreement has been terminated.

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                                      -5-


6.       MATURITY DATE

         The parties hereto confirm that the Maturity Date shall continue to be
July 31, 2007.

7.       CONFIRMATION OF CREDIT AGREEMENT AND OTHER DOCUMENTS

         The Credit Agreement and the other Documents and all covenants, terms
and provisions thereof, except as expressly amended and supplemented by this
Agreement, shall be and continue to be in full force and effect. The Credit
Agreement as amended and supplemented by this Agreement is hereby ratified and
confirmed and shall from and after the date hereof continue in full force and
effect as herein amended and supplemented.

8.       FURTHER ASSURANCES

         The parties hereto shall from time to time do all such further acts and
things and execute and deliver all such documents as are required in order to
effect the full intent of and fully perform and carry out the terms of this
Agreement.

9.       COUNTERPARTS

         This Agreement may be executed in any number of counterparts, and by
facsimile, each of which shall be deemed to be an original and all of which
taken together shall be deemed to constitute one and the same instrument, and it
shall not be necessary in making proof of this Agreement to produce or account
for more than one such counterpart.

         IN WITNESS WHEREOF the parties hereto have executed this Agreement.


BORROWER:                                     AGENT:

NEXEN INC.                                    THE TORONTO-DOMINION BANK,
                                              as Agent

By:  /s/ Una Power                            By: /s/ Wayne M. Shiplo
     ---------------------------                  -----------------------------
     Name:    Una Power                           Name:    Wayne M. Shiplo
     Title:   Treasurer                           Title:   Vice President, Loan
                                                           Syndications - Agency

By:  /s/ Rick Beingessner                     By:
     ---------------------------                  -----------------------------
     Name:    Rick Beingessner                    Name:
     Title:   Vice President, General             Title:
              Counsel--Corporate and
              Assistant Secretary


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                                      -6-


LENDERS:

THE TORONTO-DOMINION BANK                 ROYAL BANK OF CANADA

By:  /s/ Dean Ariss                       By: /s/ S.G. Tibbatts
     ---------------------------              -----------------------------
     Name:    Dean Ariss                      Name:    S.G. Tibbatts
     Title:   Managing Director               Title:   Senior Manager


By:  /s/ Kevin Kynoch                     By:
     ---------------------------              -----------------------------
     Name:    Kevin Kynoch                    Name:
     Title:   Associate --                    Title:
              Corporate Credit



THE BANK OF NOVA SCOTIA                   CANADIAN IMPERIAL BANK OF COMMERCE

By:  /s/ Dan W. Lindquist                 By:  /s/ Chris A. Perks
     ---------------------------              -----------------------------
     Name:    Dan W. Lindquist                Name:    Chris A. Perks
     Title:   Director                        Title:   Executive Director


By:                                       By: /s/  David J. Swain
     ---------------------------              -----------------------------
     Name:                                    Name:    David J. Swain
     Title:                                   Title:   Managing Director



BANK OF AMERICA, N.A.                     BNP PARIBAS (CANADA)

By:  /s/ Nelson Lam                       By: /s/  David J. Swain
     ---------------------------              -----------------------------
     Name:    Nelson Lam                      Name:    Jean-Philippe Cadot
     Title:   Vice President                  Title:   Vice President
                                                       Energy & Project Finance


By:                                       By: /s/ Charles Ritchie
     ---------------------------              -----------------------------
     Name:                                    Name:    Charles Ritchie
     Title:                                   Title:   Vice President
                                                       Energy & Project Finance


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                                   SCHEDULE A
                             LENDERS AND COMMITMENTS



The Toronto-Dominion Bank                              Commitment: $90,000,000

Royal Bank of Canada                                   Commitment: $85,000,000

The Bank of Nova Scotia                                Commitment: $75,000,000

Canadian Imperial Bank of Commerce                     Commitment: $60,000,000

Bank of America, N.A.                                  Commitment: $50,000,000

BNP Paribas (Canada)                                   Commitment: $50,000,000