Document:

<PAGE>
                                                                    EXHIBIT 10.9

[CANADIAN AGENT WILL ADVISE THE CANADIAN LENDERS OF THE DATE ON WHICH CANADIAN
BORROWER EXECUTES AND DELIVERS THIS AMENDMENT TO CANADIAN AGENT.]

                  FOURTH AMENDMENT TO CANADIAN CREDIT AGREEMENT

         The Offer for Extension set forth in this Fourth Amendment to Canadian
Credit Agreement (herein called this "Amendment") is made by Bank of America
Canada, individually and as administrative agent ("Canadian Agent"), and the
undersigned Canadian Lenders party to the Original Agreement defined below
("Canadian Lenders") and shall be open for acceptance by Northstar Energy
Corporation, an Alberta corporation ("Canadian Borrower") until (and including)
August 21, 2001.

                                   WITNESSETH:

         WHEREAS, Canadian Borrowers, Canadian Agent and Canadian Lenders have
entered into that certain Canadian Credit Agreement dated as of August 29, 2000
(as amended, supplemented, or restated to the date hereof, the "Original
Agreement"), for the purpose and consideration therein expressed, whereby
Canadian Lenders became obligated to make loans to Canadian Borrowers as therein
provided; and

         WHEREAS, on January 1, 2001 Northstar Energy, Devon Energy Canada
Holding Corporation (the successor by amalgamation to Devon Energy Canada) and
certain other Alberta corporations, all of which were Subsidiaries of US
Borrower, amalgamated under the name Northstar Energy Corporation (defined above
as the "Canadian Borrower") which is now the sole Canadian Borrower; and

         WHEREAS, pursuant to Section 1.6 of the Original Agreement, Canadian
Borrower has delivered to Canadian Agent a Request for Offer of Extension and a
copy thereof has been provided to all Canadian Lenders; and

         WHEREAS, all of the Canadian Lenders have agreed to accept such Request
for Offer of Extension; and

         WHEREAS, all of the Canadian Lenders have agreed to extend the Canadian
Revolving Period until the Conversion Date as described in Section 2.1 of this
Amendment and Canadian Agent hereby makes an Offer of Extension to Canadian
Borrower on such terms;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements contained herein and in the Original Agreement, in
consideration of the loans which

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

may hereafter be made by Canadian Lenders to Canadian Borrower, and for other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto do hereby agree as follows:

                                   ARTICLE I.

                           Definitions and References

         Section 1.1. Terms Defined in the Original Agreement. Unless the
context otherwise requires or unless otherwise expressly defined herein, the
terms defined in the Original Agreement shall have the same meanings whenever
used in this Amendment.

         Section 1.2. Other Defined Terms. Unless the context otherwise
requires, the following terms when used in this Amendment shall have the
meanings assigned to them in this Section 1.2.

                  "Amendment" means this Fourth Amendment to Canadian Credit
         Agreement.

                  "Canadian Agreement" means the Original Agreement as amended
         hereby.

                                   ARTICLE II.

                        Amendments to Original Agreement

         Section 2.1. Defined Terms.

         (a) The definition of "Conversion Date" in Annex I of the Original
Agreement is hereby amended in its entirety to read as follows:

                           "'Conversion Date' means the date which is 364 days
                  after the date on which Canadian Borrower executes and
                  delivers to Canadian Agent the Fourth Amendment to Canadian
                  Credit Agreement among Canadian Borrower, Canadian Agent and
                  Canadian Lenders, or such later day to which the Conversion
                  Date is extended pursuant to Section 1.6 of the Canadian
                  Agreement."

         Section 2.2. Waiver of Notice. Each Canadian Lender hereby waives the
requirement under Section 1.6 of the Original Agreement that a Request for Offer
of Extension be made by a specific date prior to the current Conversion Date of
August 28, 2001.

         Section 2.3. Lenders Schedule. Annex II to this Amendment is hereby
substituted for Annex II to the Original Agreement.

                                       2

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

                                  ARTICLE III.

                           Conditions of Effectiveness

         Section 3.1. Effective Date. This Amendment shall become effective on
the date on which Canadian Borrower has executed and delivered this Amendment to
Canadian Agent (provided that Canadian Borrower shall have executed this
Amendment on or before August 21, 2001) and the following additional conditions
are satisfied:

         (a) Canadian Agent shall have received all of the following, at
Canadian Agent's office, duly executed and delivered and in form and substance
satisfactory to Canadian Agent, all of the following:

                  (i) this Amendment executed by Canadian Borrower, Canadian
         Agent and all Canadian Lenders.

                  (ii) a certificate of the Chairman of the Board, President, or
         Vice President - Finance of Canadian Borrower dated the date of this
         Amendment certifying: (i) that all of the representations and
         warranties set forth in Article IV hereof are true and correct at and
         as of such date, and (ii) that no Default exists at and as of such
         date.

         (b) Canadian Borrower shall have paid, in connection with such Canadian
Loan Documents, all fees and reimbursements to be paid to Canadian Agent and
Canadian Lenders pursuant to any Canadian Loan Documents, or otherwise due
Canadian Agent or Canadian Lenders and including fees and disbursements of
Canadian Agent's attorneys.

         Section 3.2. Offer to Extend. The Offer to Extend set forth herein
shall be withdrawn and this Amendment shall be null and void if it is not
executed and delivered by Canadian Borrower on or before August 21, 2001.

                                   ARTICLE IV.

                         Representations and Warranties

         Section 4.1. Representations and Warranties of Canadian Borrower. In
order to induce each Canadian Lender to enter into this Amendment, Canadian
Borrower represents and warrants to each Canadian Lender that:

         (a) The representations and warranties contained in Article V of the
Original Agreement are true and correct at and as of the time of the
effectiveness hereof, except to the extent that the facts on which such
representations and warranties are based have been changed by the extension of
credit under the Canadian Agreement.

                                       3

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

         (b) Canadian Borrower is duly authorized to execute and deliver this
Amendment and is and will continue to be duly authorized to borrow monies and to
perform its obligations under the Canadian Agreement. Canadian Borrower has duly
taken all corporate action necessary to authorize the execution and delivery of
this Amendment and to authorize the performance of the obligations of Canadian
Borrower hereunder.

         (c) The execution and delivery by Canadian Borrower of this Amendment,
the performance by Canadian Borrower of its obligations hereunder and the
consummation of the transactions contemplated hereby do not and will not (i)
conflict with any provision of (A) any Law, (B) the organizational documents of
Canadian Borrower, or (C) any agreement, judgment, license, order or permit
applicable to or binding upon Canadian Borrower unless such conflict would not
reasonably be expected to have a Material Adverse Effect, or (ii) result in or
require the creation of any Lien upon any assets or properties of Canadian
Borrower which would reasonably be expected to have a Material Adverse Effect,
except as expressly contemplated or permitted in the Loan Documents. Except as
expressly contemplated in the Loan Documents no consent, approval, authorization
or order of, and no notice to or filing with, any Tribunal or third party is
required in connection with the execution, delivery or performance by Canadian
Borrower of this Amendment or to consummate any transactions contemplated by
this Amendment, unless failure to obtain such consent would not reasonably be
expected to have a Material Adverse Effect.

         (d) When duly executed and delivered, each of this Amendment and the
Canadian Agreement will be a legal and binding obligation of Canadian Borrower,
enforceable in accordance with its terms, except as limited by bankruptcy,
insolvency or similar laws of general application relating to the enforcement of
creditors' rights and by equitable principles of general application.

         (e) The audited annual Consolidated financial statements of US Borrower
dated as of December 31, 2000 and the unaudited quarterly Consolidated financial
statements of US Borrower dated as of March 31, 2001 fairly present the
Consolidated financial position at such dates and the Consolidated statement of
operations and the changes in Consolidated financial position for the periods
ending on such dates for US Borrower. Copies of such financial statements have
heretofore been delivered to each Canadian Lender. Since such dates no material
adverse change has occurred in the Consolidated financial condition or
businesses of US Borrower.

                                   ARTICLE V.

                                  Miscellaneous

         Section 5.1. Ratification of Agreements. The Original Agreement as
hereby amended are hereby ratified and confirmed in all respects. The Canadian
Loan Documents, as they may be amended or affected by this Amendment, are hereby
ratified and confirmed in all respects. Any reference to the Canadian Agreement
in any Loan Document shall be deemed to be a reference to

                                       4

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

the Original Agreement as hereby amended. The execution, delivery and
effectiveness of this Amendment shall not, except as expressly provided herein,
operate as a waiver of any right, power or remedy of Canadian Lenders under the
Canadian Agreement or any other Canadian Loan Document nor constitute a waiver
of any provision of the Canadian Agreement or any other Canadian Loan Document.

         Section 5.2. Survival of Agreements. All representations, warranties,
covenants and agreements of Canadian Borrower herein shall survive the execution
and delivery of this Amendment and the performance hereof, including without
limitation the making or granting of the Loans, and shall further survive until
all of the Obligations are paid in full. All statements and agreements contained
in any certificate or instrument delivered by Canadian Borrower or any
Restricted Person hereunder or under the Canadian Agreement to any Canadian
Lender shall be deemed to constitute representations and warranties by, and/or
agreements and covenants of, Canadian Borrower under this Amendment and under
the Canadian Agreement.

         Section 5.3. Canadian Loan Documents. This Amendment is a Canadian Loan
Document, and all provisions in the Canadian Agreement pertaining to Canadian
Loan Documents apply hereto.

         Section 5.4. Governing Law. This Amendment shall be governed by and
construed in accordance the laws of the Province of Alberta and any applicable
laws of Canada in all respects, including construction, validity and
performance.

         Section 5.5. Counterparts; Fax. This Amendment may be separately
executed in counterparts and by the different parties hereto in separate
counterparts, each of which when so executed shall be deemed to constitute one
and the same Amendment. This Amendment may be validly executed by facsimile or
other electronic transmission.

         THIS AMENDMENT AND THE OTHER CANADIAN LOAN DOCUMENTS REPRESENT THE
FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF
PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE
NO UNWRITTEN ORAL AGREEMENTS OF THE PARTIES.

         [The remainder of this page has been intentionally left blank.]

                                       5

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

         IN WITNESS WHEREOF, this Amendment is executed by Canadian Borrower as
of August 13, 2001.

                                           NORTHSTAR ENERGY CORPORATION
                                           Canadian Borrower

                                           By:      /s/  Paul Brereton
                                                    ----------------------------
                                                    Paul Brereton
                                                    Vice President - Finance

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

         IN WITNESS WHEREOF, this Amendment is executed by Canadian Agent and
Canadian Lenders.

                                   BANK OF AMERICA CANADA
                                   Administrative Agent, Canadian LC Issuer and
                                   Lender

                                   By:    /s/  Nelson Liam
                                          --------------------------------------
                                          Name:   Nelson Liam
                                          Title:  Vice President

                                   ABN AMRO BANK CANADA
                                   Lender

                                   By:    /s/  Teresa Wu
                                          --------------------------------------
                                          Name:   Teresa Wu
                                          Title:  Vice President

                                   By:    /s/  Mark Bohn
                                          --------------------------------------
                                          Name:   Mark Bohn
                                          Title:  Group Vice President

                                   BANCFIRST
                                   Lender

                                   By:    /s/  Arthur B. Hobbs
                                          --------------------------------------
                                          Name:   Arthur B. Hobbs
                                          Title:  Vice President

                                   BANK OF TOKYO - MITSUBISHI (CANADA)
                                   Lender

                                   By:    /s/  Davis J. Stewart
                                          --------------------------------------
                                          Name:   Davis J. Stewart
                                          Title:  Vice President

                                   BANK ONE, NA CANADA BRANCH
                                   Lender

                                   By:    /s/  Ronald L. Dierker
                                          --------------------------------------
                                          Name:   Ronald L. Dierker
                                          Title:  Director, Capital Markets

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

                              BAYERISCHE LANDESBANK
                              GIROZENTRALE, TORONTO BRANCH
                              Lender

                              By:    /s/ Eckhart Mehler
                                     -------------------------------------------
                                     Name:   Eckhart Mehler
                                     Title:  Senior Vice President & Principal
                                             Officer

                              By:    /s/  Bernd Erpenbeck
                                     -------------------------------------------
                                     Name:   Bernd Erpenbeck
                                     Title:  Second Vice President

                              CANADIAN IMPERIAL BANK OF COMMERCE
                              Lender

                              By:    /s/  Joelle Schellenberg
                                     -------------------------------------------
                                     Name:   Joelle Schellenberg
                                     Title:  Director

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

                              CITIBANK CANADA
                              Lender

                              By:    /s/  James K. G. Campbell
                                     -------------------------------------------
                                     Name:   James K. G. Campbell
                                     Title:  Vice President

                              CREDIT LYONNAIS NEW YORK BRANCH
                              Lender

                              By:    /s/  Philippe Soustra
                                     -------------------------------------------
                                     Name:   Philippe Soustra
                                     Title:  Executive Vice President

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

                                   CREDIT SUISSE FIRST BOSTON CANADA
                                   Lender

                                   By:    /s/  Peter Chauvin
                                          --------------------------------------
                                          Name:      Peter Chauvin
                                          Title:     Vice President

                                   By:    /s/  Bill McFarland
                                          --------------------------------------
                                          Name:      Bill McFarland
                                          Title:     Vice President

                                   DEUTSCHE BANK AG NEW YORK BRANCH
                                   AND/OR CAYMAN ISLANDS BRANCH
                                   Lender

                                   By:    /s/  Michael E. Keating
                                          --------------------------------------
                                          Name:      Michael E. Keating
                                          Title:     Managing Director

                                   By:    /s/  Joel Makowsky
                                          --------------------------------------
                                          Name:      Joel Makowsky
                                          Title:     Vice President

                                   FIRST UNION NATIONAL BANK
                                   Lender

                                   By:    /s/  David E. Humphreys
                                          --------------------------------------
                                          Name:      David E. Humphreys
                                          Title:     Vice President

                                   ROYAL BANK OF CANADA
                                   Lender

                                   By:    /s/  Lorne Gartner
                                          --------------------------------------
                                          Name:      Lorne Gartner
                                          Title:     Vice President

                                   SUNTRUST BANK, ATLANTA
                                   Lender

                                   By:    /s/  David J. Edge
                                          --------------------------------------
                                          Name:      David J.Edge
                                          Title:     Director

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

                              THE BANK OF NEW YORK
                              Lender

                              By:    /s/  Raymond J. Palmer
                                     -------------------------------------------
                                     Name:      Raymond J. Palmer
                                     Title:     Vice President

                              THE CHASE MANHATTAN BANK, TORONTO BRANCH
                              Lender

                              By:    /s/  Drew McDonald
                                     -------------------------------------------
                                     Name:      Drew McDonald
                                     Title:     Authorized Representative

                              By:    /s/  Christine Chan
                                     -------------------------------------------
                                     Name:      Christine Chan
                                     Title:     Authorized Representative

                              THE FUJI BANK, LIMITED
                              Lender

                              By:    /s/  Jacques Azagury
                                     -------------------------------------------
                                     Name:      Jacques Azagury
                                     Title:     Senior Vice President & Manager

                              UBS AG, STAMFORD BRANCH
                              Lender

                              By:    /s/  Susan Brunner
                                     -------------------------------------------
                                     Name:      Susan Brunner
                                     Title:     Associate Director

                              By:    /s/  Patricia O'Kicki
                                     -------------------------------------------
                                     Name:      Patricia O'Kicki
                                     Title:     Director

                              UMB BANK
                              Lender

                              By:    /s/  Derek K. Duncan
                                     -------------------------------------------
                                     Name:      Derek K. Duncan
                                     Title:     Vice President

                                   Fourth Amendment to Canadian Credit Agreement

<PAGE>

                                                                        ANNEX II

                                LENDERS SCHEDULE

                                   Fourth Amendment to Canadian Credit Agreement
<PAGE>

                                                                Fourth Amendment

                              CONSENT AND AGREEMENT

         Devon Energy Corporation, a Delaware corporation ("Canadian
Guarantor"), hereby (i) consents to the provisions of this Amendment and the
transactions contemplated herein, (ii) ratifies and confirms the Guaranty dated
as of August 29, 2000 made by it for the benefit of Canadian Agent and Lenders
executed pursuant to the Credit Agreement and the other Canadian Loan Documents,
(iii) agrees that all of its respective obligations and covenants thereunder
shall remain unimpaired by the execution and delivery of this Amendment and the
other documents and instruments executed in connection herewith, and (iv) agrees
that the Canadian Guaranty and such other Canadian Loan Documents shall remain
in full force and effect.

                                             DEVON ENERGY CORPORATION

                                             By:  /s/ Dale T. Wilson
                                                  ------------------------------
                                                  Dale T. Wilson
                                                  Treasurer

<PAGE>
                             COMPLIANCE CERTIFICATE

                          NORTHSTAR ENERGY CORPORATION

         Reference is made to that certain Fourth Amendment to Canadian Credit
Agreement dated as of August 13, 2001 (the "Fourth Amendment") among Northstar
Energy Corporation, ("Northstar"), Bank of America Canada, individually and as
administrative agent ("Canadian Agent"), and certain financial institutions
("Lenders"). Terms which are defined in the Fourth Amendment and which are used
but not defined herein shall have the meanings given them in the Fourth
Amendment. The undersigned, Paul F. Brereton, does hereby certify that he has
made a thorough inquiry into all matters certified herein and, based upon such
inquiry, experience, and the advice of counsel, does hereby further certify
that:

         1.       He is the duly elected, qualified, and acting Vice
                  President-Finance of Northstar.

         2.       All representations and warranties made by any Restricted
                  Person in any Canadian Loan Document delivered on or before
                  the date hereof are true on and as of the date hereof (except
                  to the extent that the facts upon which such representations
                  are based have been changed by the transactions contemplated
                  in the Fourth Amendment) as if such representations and
                  warranties had been made as of the date hereof.

         3.       No Default exists on the date hereof.

         4.       Each Restricted Person has performed and complied with all
                  agreements and conditions required in the Canadian Loan
                  Documents to be performed or complied with by it on or prior
                  to the date hereof.

         IN WITNESS WHEREOF, this instrument is executed by the undersigned as
of August 13, 2001.

                                             NORTHSTAR ENERGY CORPORATION

                                             By: /s/  Paul F. Brereton
                                                --------------------------------
                                                      Paul F. Brereton
                                                      Vice President-Finance
<PAGE>
                            ASSIGNMENT AND ACCEPTANCE
                           (Canadian Credit Agreement)

         Reference is made to the Canadian Credit Agreement dated as of August
29, 2000 (as amended, supplemented or otherwise modified from time to time, the
"Credit Agreement") among Northstar Energy Corporation, an Alberta corporation
(the "Canadian Borrower"), the Canadian Lenders (as defined in the Credit
Agreement) and Bank of America Canada, individually and as administrative agent
for the Lenders (the "Canadian Agent"). Terms defined in the Credit Agreement
are used herein with the same meaning.

         Each of the "Assignors" and the "Assignees" referred to on Schedule 1
agree as follows:

         1. Each Assignor hereby sells and assigns to the Assignees the portion
of its Canadian Maximum Credit Amount specified opposite its name on Schedule 1
hereto and the related Canadian Rights and Obligations (as hereinafter defined),
without recourse and without representation or warranty except as expressly set
forth herein, and each Assignee hereby purchases and assumes from the Assignors
the portion of the Canadian Maximum Credit Amount specified opposite its name on
Schedule 1 hereto and the related Canadian Rights and Obligations. After giving
effect to such sale and assignment, each Assignor's Canadian Maximum Credit
Amount and the amount of Canadian Loans owing to each Assignor will be as set
forth on Schedule 1 and each Assignee's Canadian Maximum Credit Amount and the
amount of Canadian Loans owing to each Assignee will be as set forth on Schedule
1. As used herein, "Canadian Rights and Obligations" means all outstanding
rights and obligations under the Credit Agreement and the other Canadian Loan
Documents relating to the Canadian Loans and the Canadian Maximum Credit Amount.
This Assignment and Acceptance is subject to Section 1.12 of the Credit
Agreement. On the Effective Date under such Section 1.12, the amount allocated
to the Canadian Maximum Credit Amount is $275,000,000 and the amount allocated
to the Tranche B Maximum Credit Amount is $525,000,000.

         2. Each Assignor (i) represents and warrants that it is the legal and
beneficial owner of the interest being assigned by it hereunder and that such
interest is free and clear of any adverse claim; (ii) makes no representation or
warranty and assumes no responsibility with respect to any statements,
warranties or representations made in or in connection with the Canadian Loan
Documents or the execution, legality, validity, enforceability, genuineness,
sufficiency or value of the Canadian Loan Documents or any other instrument or
document furnished pursuant thereto; (iii) makes no representation or warranty
and assumes no responsibility with respect to the financial condition of any
Restricted Person or the performance or observance by any Restricted Person of
any of its obligations under the Canadian Loan Documents or any other instrument
or document furnished pursuant thereto; and (iv) is delivering to Canadian Agent
its Canadian Note and requests that Canadian Agent exchange such Canadian Note
for a new Canadian Note payable to the order of such Assignor in an amount equal
to the Canadian Maximum Credit Amount retained by such Assignor as specified on
Schedule 1 and a new Canadian Note payable to the order of the relevant Assignee
in an amount equal to the Canadian Maximum Credit Amount of such Assignee
specified in Schedule 1.

<PAGE>

         3. Each Assignee (i) confirms that it has received a copy of the Credit
Agreement, together with copies of the financial statements referred to in
Section 6.2 thereof and such other documents and information as it has deemed
appropriate to make its own credit analysis and decision to enter into this
Assignment and Acceptance; (ii) agrees that it will, independently and without
reliance upon Canadian Agent, the Assignors or any other Lender and based on
such documents and information as it shall deem appropriate at the time,
continue to make its own credit decisions in taking or not taking action under
the Credit Agreement; (iii) confirms that it is an Eligible Transferee; (iv)
appoints and authorizes Canadian Agent to take such action as Canadian Agent on
its behalf and to exercise such powers and discretion under the Credit Agreement
as are delegated to Canadian Agent by the terms thereof, together with such
powers and discretion as are reasonably incidental thereto; (v) agrees that it
will perform in accordance with their terms all of the obligations that by the
terms of the Credit Agreement are required to be performed by it as a Lender.

         4. Following the execution of this Assignment and Acceptance, it will
be delivered to Canadian Agent for acceptance and recording by Canadian Agent.
The effective date for this Assignment and Acceptance (the "Effective Date")
shall be August 9, 2001.

         5. Upon such acceptance and recording by Canadian Agent, as of the
Effective Date, (i) the Assignees shall be parties to the Credit Agreement and,
to the extent provided in this Assignment and Acceptance, have the rights and
obligations of Canadian Lenders thereunder and (ii) the Assignors shall, to the
extent provided in this Assignment and Acceptance, relinquish their rights and
be released from their obligations under the Credit Agreement.

         6. Upon such acceptance and recording by Canadian Agent, from and after
the Effective Date, Canadian Agent shall make all payments under the Credit
Agreement and the Canadian Notes in respect of the interest assigned hereby
(including, without limitation, all payments of principal, interest and
commitment fees with respect thereto) to the appropriate Assignees, except that
BAs outstanding on the Effective Date shall settle on the expiration date
thereof in accordance with the interests therein held by Assignors on the
Effective Date. The Assignors and Assignees shall make all appropriate
adjustments in payments under the Credit Agreement and the Canadian Notes for
periods prior to the Effective Date directly between themselves.

         7. This Assignment and Acceptance shall be governed by, and construed
in accordance with, the Laws of the Province of Alberta, Canada.

         8. This Assignment and Acceptance may be executed in any number of
counterparts and by different parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement. Delivery of an executed
counterpart of this Assignment and Acceptance by telecopier shall be effective
as delivery of a manually executed counterpart of this Assignment and
Acceptance.

<PAGE>

         IN WITNESS WHEREOF, the Assignors and the Assignees have caused this
Assignment and Acceptance to be executed by their officers thereunto duly
authorized as of August 9, 2001.

ASSIGNORS:                       BANK OF AMERICA CANADA, as Assignor

                                 By:    /s/  Nelson Lam
                                        ----------------------------------------
                                        Name:      Nelson Lam
                                        Title:     Vice President

                                 ABN AMRO BANK CANADA, as Assignor

                                 By:    /s/  Mark Bohn
                                        ----------------------------------------
                                        Name:      Mark Bohn
                                        Title:     Group Vice President

                                 By:    /s/  Teresa Wu
                                        ----------------------------------------
                                        Name:      Teresa Wu
                                        Title:     Vice President

                                 BANK ONE, NA, CANADA BRANCH,
                                 as Assignor

                                 By:    /s/  Ronald L. Dierker
                                        ----------------------------------------
                                        Name:      Ronald L. Dierker
                                        Title:     Director, Capital Markets

                                 CITIBANK CANADA, as Assignor

                                 By:    /s/  James K. G. Campbell
                                        ----------------------------------------
                                        Name:      James K. G. Campbell
                                        Title:     Vice President

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                 FIRST UNION NATIONAL BANK,
                                 as Assignor

                                 By:    /s/  David E. Humphreys
                                        ----------------------------------------
                                        Name:      David E. Humphreys
                                        Title:     Vice President

                                 SUNTRUST BANK, ATLANTA,
                                 as Assignor

                                 By:    /s/  David J. Edge
                                        ----------------------------------------
                                        Name:      David J. Edge
                                        Title:     Director

                                 THE CHASE MANHATTAN BANK,
                                 TORONTO BRANCH, as Assignor

                                 By:    /s/  Drew McDonald
                                        ----------------------------------------
                                        Name:      Drew McDonald
                                        Title:     Authorized Representative

                                 By:    /s/  Christine Chan
                                        ----------------------------------------
                                        Name:      Christine Chan
                                        Title:     Authorized Representative

                                 UMB BANK, as Assignor

                                 By:    /s/  Derek K. Duncan
                                        ----------------------------------------
                                        Name:      Derek K. Duncan
                                        Title:     Vice President

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                 WESTDEUTSCHE LANDESBANK
                                 GIROZENTRALE, as Assignor

                                 By:    /s/  Salvatore Battinelli
                                        ----------------------------------------
                                        Name:      Salvatore Battinelli
                                        Title:     Managing Director

                                 By:    /s/  Walter T. Duffy III
                                        ----------------------------------------
                                        Name:      Walter T. Duffy III
                                        Title:     Associate Director

ASSIGNEES:                       BANCFIRST, as Assignee

                                 By:    /s/  Arthur B. Hobbs
                                        ----------------------------------------
                                        Name:      Arthur B. Hobbs
                                        Title:     Vice President

                                 BANK OF TOKYO - MITSUBISHI
                                 (CANADA), as Assignee

                                 By:    /s/  Davis J. Stewart
                                        ----------------------------------------
                                        Name:      Davis J. Stewart
                                        Title:     Vice President

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                  BAYERISCHE LANDESBANK
                                  GIROZENTRALE, TORONTO  BRANCH,
                                  as Assignee

                                  By:    /s/  Eckhart Mehler
                                         ---------------------------------------
                                         Name:      Eckhart Mehler
                                         Title:     Senior Vice President &
                                                    Principal Officer

                                  By:    /s/  Bernd Erpenbeck
                                         ---------------------------------------
                                         Name:      Bernd Erpenbeck
                                         Title:     Second Vice President

                                  CANADIAN IMPERIAL BANK OF
                                  COMMERCE, as Assignee

                                  By:    /s/  Joelle Schellenberg
                                         ---------------------------------------
                                         Name:      Joelle Schellenberg
                                         Title:     Director

                                  CREDIT LYONNAIS NEW YORK
                                  BRANCH, as Assignee

                                  By:    /s/  Philippe Soustra
                                         ---------------------------------------
                                         Name:      Philippe Soustra
                                         Title:     Executive Vice President

                                  CREDIT SUISSE FIRST BOSTON,
                                  as Assignee

                                  By:    /s/  Peter Chauvin
                                         ---------------------------------------
                                         Name:      Peter Chauvin
                                         Title:     Vice President

                                  By:    /s/  Bill McFarland
                                         ---------------------------------------
                                         Name:      Bill McFarland
                                         Title:     Vice President

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                  DEUTSCHE BANK AG NEW YORK
                                  BRANCH AND/OR CAYMAN ISLANDS
                                  BRANCH, as Assignee

                                  By:    /s/  Michael E. Keating
                                         ---------------------------------------
                                         Name:   Michael E. Keating
                                         Title:  Managing Director

                                  By:    /s/  Joel Makowsky
                                         ---------------------------------------
                                         Name:   Joel Makowsky
                                         Title:  Vice President

                                  ROYAL BANK OF CANADA, as Assignee

                                  By:    /s/  Lorne Gartner
                                         ---------------------------------------
                                         Name:   Lorne Gartner
                                         Title:  Vice President

                                  THE BANK OF NEW YORK, as Assignee

                                  By:    /s/  Raymond J. Palmer
                                         ---------------------------------------
                                         Name:   Raymond J. Palmer
                                         Title:  Vice President

                                  THE FUJI BANK, LIMITED, as Assignee

                                  By:    /s/  Jacques Azagury
                                         ---------------------------------------
                                         Name:   Jacques Azagury
                                         Title:  Senior Vice President & Manager

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                  UBS AG, STAMFORD BRANCH,
                                  as Assignee

                                  By:    /s/  Wilfred V. Saint
                                         ---------------------------------------
                                         Name:      Wilfred S. Saint
                                         Title:     Associate Director
                                                    Banking Products Services US

                                  By:    /s/  Patricia O'Kicki
                                         ---------------------------------------
                                         Name:      Patricia O'Kicki
                                         Title:     Director
                                                    Banking Products Services

ACCEPTED AND APPROVED,
as of the 9th day of August, 2001:

BANK OF AMERICA, CANADA

By: /s/  Nelson Lam
    ---------------------------------------
    Name:  Nelson Lam
    Title: Vice President

APPROVED as of the 9th day of August, 2001:

NORTHSTAR ENERGY CORPORATION

By: /s/  John Richels
    ---------------------------------------
    Name:  John Richels
    Title: Chief Executive Officer

                           Assignment and Acceptance (Canadian Credit Agreement)
<PAGE>

                                   SCHEDULE 1
                                       TO
                            ASSIGNMENT AND ACCEPTANCE
                           (CANADIAN CREDIT AGREEMENT)

                                                         Page 1 of Schedule 1 to
                           Assignment and Acceptance (Canadian Credit Agreement)

<PAGE>

<Table>
<Caption>
                                                                                                                MAXIMUM AGGREGATE
                                                    NEW CANADIAN CREDIT                        OUTSTANDING     COMMITMENT UNDER U.S.
                               AMOUNT OF CANADIAN      MAXIMUM AMOUNT      PERCENTAGE SHARE      CANADIAN      CREDIT AGREEMENT AND
                                 MAXIMUM CREDIT     AFTER ASSIGNMENT AND  UNDER THE CANADIAN    LOANS AFTER       CANADIAN CREDIT
                                 AMOUNT ASSIGNED    CANADIAN NOTE AMOUNT   CREDIT AGREEMENT      ASSIGNMENT          AGREEMENT
          BANK NAME             (IN US DOLLARS)      (IN U.S. DOLLARS)     AFTER ASSIGNMENT   (IN US DOLLARS)    (IN U.S. DOLLARS)
          ---------            ------------------   --------------------  ------------------  ---------------  ---------------------
<S>                            <C>                  <C>                   <C>                 <C>              <C>
 ASSIGNORS:

 Bank of America Canada            5,156,250              28,125,000            7.500%          5,897,853.46       60,000,000.00

 ABN AMRO Bank Canada              3,750,000              23,437,500            6.250%          4,914,877.89       50,000,000.00

 Bank One, NA, Canada Branch       5,156,250              28,125,000            7.500%          5,897,853.46       60,000,000.00

 Citibank Canada                   3,750,000              23,437,500            6.250%          4,914,877.89       50,000,000.00

 First Union National Bank         5,156,250              28,125,000            7.500%          5,897,853.46       60,000,000.00

 SunTrust Bank                     1,562,500               7,031,250            1.875%          1,474,463.37       15,000,000.00

 The Chase Manhattan Bank,        20,625,000              28,125,000            7.500%          5,897,853.46       60,000,000.00
 Toronto Branch

 UMB Bank                            468,750               7,031,250            1.875%          1,474,463.37       15,000,000.00

 Westdeutsche Landesbank          20,625,000                       0                0                      0                   0
</Table>

                                                         Page 2 of Schedule 1 to
                           Assignment and Acceptance (Canadian Credit Agreement)

<PAGE>

<Table>
<Caption>
                                                                                                                MAXIMUM AGGREGATE
                                                    NEW CANADIAN CREDIT                        OUTSTANDING     COMMITMENT UNDER U.S.
                               AMOUNT OF CANADIAN      MAXIMUM AMOUNT      PERCENTAGE SHARE      CANADIAN      CREDIT AGREEMENT AND
                                 MAXIMUM CREDIT     AFTER ASSIGNMENT AND  UNDER THE CANADIAN    LOANS AFTER       CANADIAN CREDIT
                                 AMOUNT ASSIGNED    CANADIAN NOTE AMOUNT   CREDIT AGREEMENT      ASSIGNMENT          AGREEMENT
          BANK NAME             (IN US DOLLARS)      (IN U.S. DOLLARS)     AFTER ASSIGNMENT   (IN US DOLLARS)    (IN U.S. DOLLARS)
          ---------            ------------------   --------------------  ------------------  ---------------  ---------------------
<S>                            <C>                  <C>                   <C>                 <C>              <C>
ASSIGNEES:

BancFirst                            4,687,500            4,687,500            1.250%             982,463.37        10,000,000.00

Bank of Tokyo - Mitsubishi           7,968,750           18,750,000            5.000%           3,931,902.31        40,000,000.00
Canada

Bayerische                             937,500           18,750,000            5.000%           3,931,902.31        40,000,000.00
Landesbank
Girozentrale,
Toronto Branch

Canadian Imperial Bank of              937,500           11,718,750            3.125%           2,457,438.94        25,000,000.00
Commerce

Credit Lyonnais                        937,500           18,750,000            5.000%           3,931,902.31        40,000,000.00

Credit Suisse First Boston          23,437,500           23,437,500            6.250%           4,914,877.89        50,000,000.00

Deutsche Bank AG                     4,375,000           23,437,500            6.250%           4,914,877.89        50,000,000.00

Royal Bank of Canada                 7,500,000           28,125,000            7.500%           5,897,853.46        60,000,000.00

The Bank of New York                   468,750           21,093,750            5.625%           4,423,390.10        45,000,000.00

The Fuji Bank, Limited               3,281,250           21,093,750            5.625%           4,423,390.10        45,000,000.00
(Mizuho)

UBS AG                              11,718,750           11,718,750            3.125%           2,457,438.94        25,000,000.00
</Table>

                                                         Page 3 of Schedule 1 to
                           Assignment and Acceptance (Canadian Credit Agreement)<PAGE>
                                                                   EXHIBIT 10.10

                  FIFTH AMENDMENT TO CANADIAN CREDIT AGREEMENT

         THIS FIFTH AMENDMENT TO CANADIAN CREDIT AGREEMENT (herein called this
"Amendment") made as of September 21, 2001 by and among Northstar Energy
Corporation, an Alberta corporation ("Canadian Borrower"), Bank of America
Canada, individually and as administrative agent ("Canadian Agent"), and the
Canadian Lenders party to the Original Agreement defined below ("Canadian
Lenders").

                                   WITNESSETH:

         WHEREAS, Canadian Borrower, Canadian Agent and Canadian Lenders entered
into that certain Canadian Credit Agreement dated as of August 29, 2000 (as
amended, supplemented, or restated to the date hereof, the "Original
Agreement"), for the purpose and consideration therein expressed, whereby
Canadian Lenders became obligated to make loans to Canadian Borrowers as therein
provided;

         WHEREAS, upon becoming an "authorized foreign bank", it is intended
that Bank of America, N.A. acting through a Canadian branch will replace Bank of
America Canada as Canadian Agent, Canadian LC Issuer, Canadian Swing Lender and
as a Canadian Lender;

         WHEREAS, Canadian Borrower, Canadian Agent and Canadian Lenders desire
to amend the Original Agreement as set forth herein;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements contained herein and in the Original Agreement, in
consideration of the loans which may hereafter be made by Canadian Lenders to
Canadian Borrower, and for other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto do hereby
agree as follows:

                                   ARTICLE I.

                           Definitions and References

         Section 1.1. Terms Defined in the Original Agreement. Unless the
context otherwise requires or unless otherwise expressly defined herein, the
terms defined in the Original Agreement shall have the same meanings whenever
used in this Amendment.

         Section 1.2. Other Defined Terms. Unless the context otherwise
requires, the following terms when used in this Amendment shall have the
meanings assigned to them in this Section 1.2.

                  "Amendment" means this Fifth Amendment to Canadian Credit
         Agreement.

<PAGE>
                  "Amendment Fee" means a fee, payable to each Canadian Lender
         which executes and delivers this Amendment before noon on September 21,
         2001 (unless extended by Canadian Borrower), in the amount of five
         basis points (0.05%) of such Canadian Lender's Percentage Share of the
         Canadian Maximum Credit Amount.

                  "Long Term Financing" means a senior unsecured bank facility
         in an amount not to exceed US $6,000,000,000 arranged by UBS Warburg
         LLC and Banc of America Securities LLC to finance the acquisition by US
         Borrower of Anderson Exploration Ltd. and/or Mitchell Energy &
         Development Corp. through wholly-owned Subsidiaries of US Borrower.

                  "Canadian Agreement" means the Original Agreement as amended
         hereby.

                                   ARTICLE II.

                        Amendments to Original Agreement

         Section 2.1. Defined Terms.

         (a) The definitions of "Canadian Agent", "Canadian LC Issuer",
"Canadian Lenders", "Canadian Prime Rate", "Canadian Resident Lender", "Canadian
Swing Lender", "Canadian Swing Rate" and "Canadian US Dollar Base Rate" in Annex
I to the Original Agreement are hereby amended in their entirety to read as
follows:

                  "Canadian Agent" means Bank of America Canada and its
         successors and assigns as administrative agent under the Canadian
         Agreement.

                  "Canadian LC Issuer" means Bank of America Canada and its
         successors and assigns in its capacity as the issuer of Letters of
         Credit under the Canadian Agreement. Canadian Agent may, with the
         consent of Canadian Borrower and the Lender in question, appoint any
         Canadian Resident Lender hereunder as a Canadian LC Issuer in place of
         or in addition to Canadian Agent.

                  "Canadian Lenders" means each signatory to the Canadian
         Agreement (other than any Borrower), including Bank of America Canada
         and, upon the requirements of Section 2.5 of the Fifth Amendment to
         Canadian Credit Agreement, dated as of September 21, 2001, among
         Canadian Borrower, Canadian Agent and Canadian Lenders, being
         completed, Bank of America, N.A. acting through a Canadian branch in
         the capacity of a Canadian Lender and the Canadian Swing Lender
         hereunder, rather than as Canadian Agent and Canadian LC Issuer, and
         the successors of each such party as holder of a Canadian Note.

                  "Canadian Prime Rate" means on any day a fluctuating rate of
         interest per annum equal to the higher of (i) the rate of interest per
         annum most recently announced by

                                       2

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>
         Canadian Agent as its reference rate for Canadian Dollar commercial
         loans made to a Person in Canada; and (ii) Canadian Agent's Discount
         Rate for Bankers' Acceptances having a maturity of thirty days plus the
         Applicable Margin. No Canadian Prime Rate charged by any Person shall
         ever exceed the Highest Lawful Rate.

                  "Canadian Resident Lender" means each Lender identified as
         such on Annex II to the Canadian Agreement or any Assignment and
         Acceptance executed by a new Lender, each being a Person that is (i)
         not a non-resident of Canada for the purposes of the Income Tax Act
         (Canada) or (ii) a Person that is an "authorized foreign bank" as
         defined in section 2 of the Bank Act (Canada) and in subsection 248(1)
         of the Income Tax Act (Canada) which will receive all amounts paid or
         credited to it under the Canadian Obligations in respect of its
         "Canadian banking business" for the purposes of paragraph 212(13.3)(a)
         of the Income Tax Act (Canada).

                  "Canadian Swing Lender" means Bank of America Canada and its
         successors and assigns, in their individual capacities, as Canadian
         Swing Lender.

                  "Canadian Swing Rate" means on any day a fluctuating rate of
         interest per annum established from time to time by Canadian Swing
         Lender as its money market rate, which rate may not be the lowest rate
         of interest charged by Canadian Swing Lender to its customers, plus the
         Applicable Margin. The Canadian Swing Rate shall never exceed the
         Highest Lawful Rate.

                  "Canadian US Dollar Base Rate" means on any day, the rate per
         annum equal to the higher of (a) the Federal Funds Rate for such day
         plus one-half of one percent (0.5%) and (b) the rate of interest per
         annum most recently established by Canadian Agent as its reference rate
         for US Dollar commercial loans made to a Person in Canada. Any change
         in the Canadian US Dollar Base Rate due to a change in Canadian Agent's
         reference rate shall be effective on the effective date of such change.
         No Canadian US Dollar Base Rate charged by any Person shall ever exceed
         the Highest Lawful Rate.

                  "Schedule II BA Reference Banks" means the Lenders listed in
         Schedule II to the Bank Act (Canada) and the Lenders listed in Schedule
         III to the Bank Act (Canada) that are not subject to the restrictions
         and requirements referred to in subsection 524(2) of the Bank Act
         (Canada) as are, at such time, designated by Canadian Agent, with the
         prior consent of the Canadian Borrower (acting reasonably), as the
         Schedule II BA Reference Banks.

         (b) Clauses (o) and (x) of the definition of "Permitted Liens" in Annex
I to the Original Agreement are hereby amended in their entirety to read as
follows:

                  "(o)     Liens in respect of Indebtedness permitted by
                           Sections 7.1(b), 7.1(f) and 7.1(j), and Liens in
                           respect of Indebtedness permitted by Section 7.1(c),
                           but only to the extent that such Liens encumber the
                           assets expressly permitted to secure such
                           Indebtedness by the terms of Section 7.1(c);"

                                       3

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

                  "(x)     in addition to Liens permitted by clauses (a) through
                           (w) above, Liens on property or assets if the
                           aggregate Indebtedness secured thereby does not
                           exceed two percent (2%) of Consolidated Assets."

         Section 2.2. Indebtedne Section Subsection (c) of Section 7.1 of the
Original Agreement is hereby amended in its entirety to read as follows:

                  "(c) unsecured Liabilities owed among the Restricted Persons;
         provided that Liabilities owed by any Restricted Subsidiary (other than
         Canadian Borrower) to US Borrower may be secured by any and all assets
         of such Restricted Subsidiary."

         Section 2.3. Funded Debt to Total Capitalization. Section 7.6 of the
Original Agreement is hereby amended in its entirety to read as follows:

                  "Section 7.6. Funded Debt to Total Capitalization. The ratio
         of US Borrower's Consolidated Total Funded Debt to US Borrower's Total
         Capitalization will not exceed (i) seventy percent (70%) at the end of
         any Fiscal Quarter ending on or before June 30, 2002, or (ii)
         sixty-five percent (65%) at the end of any Fiscal Quarter thereafter."

         Section 2.4. Assignments. Section 10.6(a)(ii) of the Original Agreement
is hereby amended in its entirety to read as follows:

                  "(ii) together with each such assignment of its rights and
         obligations under this Agreement, such Lender shall assign the same
         Percentage Share of its rights and obligations with respect to the
         Tranche B Loans under the US Agreement to the same Eligible Transferee
         or an Affiliate of such Eligible Transferee, unless such assignment is
         being made to an Eligible Transferee which is an Affiliate of the
         assignor;"

         Section 2.5. Concerning Bank of America. Canadian Agent, Canadian
Borrower and Canadian Lenders hereby agree that Bank of America, N.A. acting
through a Canadian branch shall automatically become Canadian Agent, Canadian LC
Issuer, Canadian Swing Lender and a Canadian Lender under the Canadian Agreement
and that all references to Bank of America Canada in the Loan Documents shall be
deemed to refer to Bank of America, N.A. acting through a Canadian branch upon
(i) Bank of America, N.A. acting through a Canadian branch becoming an
"authorized foreign bank" under the Bank Act (Canada), and (ii) Bank of America,
N.A. acting through a Canadian branch providing to Canadian Borrower all of the
following:

                  (a) evidence that Bank of America, N.A. acting through a
         Canadian branch has become an "authorized foreign bank" under the Bank
         Act (Canada); and

                  (b) an assignment by Bank of America Canada to Bank of
         America, N.A. acting through a Canadian branch of all its rights and
         obligations under the Canadian Agreement (including, without
         limitation, all of its Canadian Loans, Canadian Note and its Percentage
         Share of the Canadian LC Obligations and the Canadian Maximum Credit
         Amount) complying with the requirements of Section 10.6 of the Canadian
         Agreement, as amended hereby except for the provisions of the last
         sentence of Section 10.6(a) which shall not be applicable.

                                       4

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

                                  ARTICLE III.

                           Conditions of Effectiveness

         Section 3.1. Effective Date. Except for the amendment in Section2.3
hereof, this Amendment shall become effective as of the date first above written
when and only when:

         (a) Canadian Agent shall have received all of the following, at
Canadian Agent's office, duly executed and delivered and in form and substance
satisfactory to Canadian Agent, all of the following:

                  (i) this Amendment executed by Canadian Borrower, Canadian
         Agent and Canadian Required Lenders.

                  (ii) a certificate of the Chairman of the Board, President, or
         Vice President - Finance of Canadian Borrower dated the date of this
         Amendment certifying: (i) that all of the representations and
         warranties set forth in Article IV hereof are true and correct at and
         as of such date, and (ii) that no Default exists at and as of such
         date.

         (b) Canadian Borrower shall have paid, to each Canadian Lender which
executed and delivered this Amendment before noon on September 21, 2001 (unless
extended by Canadian Borrower), such Canadian Lender's Amendment Fee and all
other fees and reimbursements to be paid to Canadian Agent and Canadian Lenders
pursuant to any Canadian Loan Documents, or otherwise due Canadian Agent or
Canadian Lenders and including fees and disbursements of Canadian Agent's
attorneys.

         Section 3.2. Effective Date of Section 2.3. The amendment in Section
2.3 of this Amendment shall become effective as of the date when and only as of
the date when:

         (a) The conditions set forth in Section 3.1 (a) and (b) above have been
satisfied; and

         (b) The documentation governing the Long Term Financing shall have been
executed and delivered, the initial funding shall have been advanced thereunder,
and shares of Anderson Exploration Ltd. shall have been acquired by US Borrower
or a Restricted Subsidiary pursuant to US Borrower's offer to purchase the
shares of Anderson Exploration Ltd.

                                       5

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

                                   ARTICLE IV.

                         Representations and Warranties

         Section 4.1. Representations and Warranties of Canadian Borrower. In
order to induce each Canadian Lender to enter into this Amendment, Canadian
Borrower represents and warrants to each Canadian Lender that:

         (a) The representations and warranties contained in Article V of the
Original Agreement are true and correct at and as of the time of the
effectiveness hereof, except to the extent that the facts on which such
representations and warranties are based have been changed by the extension of
credit under the Canadian Agreement.

         (b) Canadian Borrower is duly authorized to execute and deliver this
Amendment and is and will continue to be duly authorized to borrow monies and to
perform its obligations under the Canadian Agreement. Canadian Borrower has duly
taken all corporate action necessary to authorize the execution and delivery of
this Amendment and to authorize the performance of the obligations of Canadian
Borrower hereunder.

         (c) The execution and delivery by Canadian Borrower of this Amendment,
the performance by Canadian Borrower of its obligations hereunder and the
consummation of the transactions contemplated hereby do not and will not (i)
conflict with any provision of (A) any Law, (B) the organizational documents of
Canadian Borrower, or (C) any agreement, judgment, license, order or permit
applicable to or binding upon Canadian Borrower unless such conflict would not
reasonably be expected to have a Material Adverse Effect, or (ii) result in or
require the creation of any Lien upon any assets or properties of Canadian
Borrower which would reasonably be expected to have a Material Adverse Effect,
except as expressly contemplated or permitted in the Loan Documents. Except as
expressly contemplated in the Loan Documents no consent, approval, authorization
or order of, and no notice to or filing with, any Tribunal or third party is
required in connection with the execution, delivery or performance by Canadian
Borrower of this Amendment or to consummate any transactions contemplated by
this Amendment, unless failure to obtain such consent would not reasonably be
expected to have a Material Adverse Effect.

         (d) When duly executed and delivered, each of this Amendment and the
Canadian Agreement will be a legal and binding obligation of Canadian Borrower,
enforceable in accordance with its terms, except as limited by bankruptcy,
insolvency or similar laws of general application relating to the enforcement of
creditors' rights and by equitable principles of general application.

         (e) The audited annual Consolidated financial statements of US Borrower
dated as of December 31, 2000 and the unaudited quarterly Consolidated financial
statements of US Borrower dated as of June 30, 2001 fairly present the
Consolidated financial position at such dates and the Consolidated statement of
operations and the changes in Consolidated financial position for the periods
ending on such dates for US Borrower. Copies of such financial

                                       6

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

statements have heretofore been delivered to each Canadian Lender. Since such
dates no material adverse change has occurred in the Consolidated financial
condition or businesses of US Borrower.

                                   ARTICLE V.

                                  Miscellaneous

         Section 5.1. Long Term Financing. Pursuant to Section 9.7 of the
Canadian Agreement, Canadian Lenders agreed that Bank of America Canada and its
Affiliates may engage in any kind of banking, trust, financial advisory,
underwriting or other business with each of the Restricted Persons and their
respective Affiliates as though Bank of America Canada were not the Canadian
Agent or the Canadian LC Issuer hereunder and without notice to or consent of
Lenders. Canadian Lenders acknowledged that, pursuant to such activities, Bank
of America Canada or its Affiliates may receive information regarding any
Restricted Person or its Affiliates (including information that may be subject
to confidentiality obligations in favor of such Restricted Person or such
Affiliate) and that the Canadian Agent shall be under no obligation to provide
such information to them. Although not required by the terms of the Original
Agreement, Bank of America Canada hereby notifies Canadian Lenders that USB AG,
Stamford Branch, UBS Warburg LLC, Bank of America and Banc of America Securities
LLC have agreed to provide the Long Term Financing and may provide additional
services to the Restricted Persons in connection with the acquisitions financed
thereby.

         Section 5.2. Ratification of Agreements. The Original Agreement as
hereby amended is hereby ratified and confirmed in all respects. The Canadian
Loan Documents, as they may be amended or affected by this Amendment, are hereby
ratified and confirmed in all respects. Any reference to the Canadian Agreement
in any Loan Document shall be deemed to be a reference to the Original Agreement
as hereby amended. The execution, delivery and effectiveness of this Amendment
shall not, except as expressly provided herein, operate as a waiver of any
right, power or remedy of Canadian Lenders under the Canadian Agreement or any
other Canadian Loan Document nor constitute a waiver of any provision of the
Canadian Agreement or any other Canadian Loan Document.

         Section 5.3. Survival of Agreements. All representations, warranties,
covenants and agreements of Canadian Borrower herein shall survive the execution
and delivery of this Amendment and the performance hereof, including without
limitation the making or granting of the Loans, and shall further survive until
all of the Obligations are paid in full. All statements and agreements contained
in any certificate or instrument delivered by Canadian Borrower or any
Restricted Person hereunder or under the Canadian Agreement to any Canadian
Lender shall be deemed to constitute representations and warranties by, and/or
agreements and covenants of, Canadian Borrower under this Amendment and under
the Canadian Agreement.

         Section 5.4. Canadian Loan Documents. This Amendment is a Canadian Loan
Document, and all provisions in the Canadian Agreement pertaining to Canadian
Loan Documents apply hereto.

                                       7

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

         Section 5.5. Governing Law. This Amendment shall be governed by and
construed in accordance the laws of the Province of Alberta and any applicable
laws of Canada in all respects, including construction, validity and
performance.

         Section 5.6. Counterparts; Fax. This Amendment may be separately
executed in counterparts and by the different parties hereto in separate
counterparts, each of which when so executed shall be deemed to constitute one
and the same Amendment. This Amendment may be validly executed by facsimile or
other electronic transmission.

         THIS AMENDMENT AND THE OTHER CANADIAN LOAN DOCUMENTS REPRESENT THE
FINAL AGREEMENT BETWEEN THE PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF
PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES. THERE ARE
NO UNWRITTEN ORAL AGREEMENTS OF THE PARTIES.

            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK.]

                                       8

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

         IN WITNESS WHEREOF, this Amendment is executed as of the date first
above written.

                             NORTHSTAR ENERGY CORPORATION
                             Canadian Borrower

                             By: /s/ Paul Brereton
                                 ----------------------------------------------
                                 Name:  Paul Brereton
                                 Title: Vice President - Finance

                             BANK OF AMERICA CANADA
                             Administrative Agent, Canadian LC Issuer and
                             Lender

                             By: /s/  Nelson Lam
                                 ----------------------------------------------
                                 Name:  Nelson Lam
                                 Title: Vice President

                             ABN AMRO BANK CANADA
                             Lender

                             By: /s/  Mark Bohn
                                 ----------------------------------------------
                                 Name:  Mark Bohn
                                 Title: Group Vice President

                             By: /s/  Teresa Wu
                                 ----------------------------------------------
                                 Name:  Teresa Wu
                                 Title: Vice President

                             BANCFIRST
                             Lender

                             By: /s/ Arthur B. Hobbs
                                 ----------------------------------------------
                                 Name:  Arthur B. Hobbs
                                 Title: Vice President

                             BANK OF TOKYO - MITSUBISHI (CANADA)
                             Lender

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

                                    Fifth Amendment to Canadian Credit Agreement

<PAGE>

                             BANK ONE, NA, CANADA BRANCH
                             Lender

                             By: /s/  Jeanie C. Harman
                                 ----------------------------------------------
                                 Name:  Jeanie C. Harman
                                 Title: First Vice President

                             BAYERISCHE LANDESBANK
                             GIROZENTRALE, TORONTO BRANCH
                             Lender

                             By: /s/  Thomas Miller
                                 ----------------------------------------------
                                 Name:  Thomas Miller
                                 Title: Vice President

                             By: /s/  Bernd Erpenbeck
                                 ----------------------------------------------
                                 Name:  Bernd Erpenbeck
                                 Title: Second Vice President

                             CANADIAN IMPERIAL BANK OF COMMERCE
                             Lender

                             By: /s/  Joelle Schellenberg
                                 ----------------------------------------------
                                 Name:  Joelle Schellenerg
                                 Title: Director

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

                             CITIBANK CANADA
                             Lender

                             By: /s/ James K. G. Campbell
                                 ----------------------------------------------
                                 Name:  James K. G. Campbell
                                 Title: Vice President

                             CREDIT LYONNAIS NEW YORK BRANCH
                             Lender

                             By: /s/ Bernard Weymuller
                                 ----------------------------------------------
                                 Name:  Bernard Weymuller
                                 Title: Senior Vice President

                                    Fifth Amendment to Canadian Credit Agreement

<PAGE>

                             CREDIT SUISSE FIRST BOSTON CANADA
                             Lender

                             By: /s/  W. M. McFarland
                                 ----------------------------------------------
                                 Name:  W. M. McFarland
                                 Title: Vice President

                             By: /s/  Peter Chauvin
                                 ----------------------------------------------
                                 Name:  Peter Chauvin
                                 Title: Vice President

                             DEUTSCHE BANK AG NEW YORK BRANCH
                             AND/OR CAYMAN ISLANDS BRANCH
                             Lender

                             By: /s/ Joel Makowsky
                                 ----------------------------------------------
                                 Name:  Joel Makowsky
                                 Title: Vice President

                             By: /s/ Hans C. Narberhaus
                                 ----------------------------------------------
                                 Name:  Hans C. Narberhaus
                                 Title: Vice President

                             FIRST UNION NATIONAL BANK
                             Lender

                             By: /s/ James M. Kipp
                                 ----------------------------------------------
                                 Name:  James M. Kipp
                                 Title: Managing Director

                             ROYAL BANK OF CANADA
                             Lender

                             By: /s/ Lorne Gartner
                                 ----------------------------------------------
                                 Name:  Lorne Gartner
                                 Title: Vice President

                             SUNTRUST BANK, ATLANTA
                             Lender

                             By: /s/ David J. Edge
                                 ----------------------------------------------
                                 Name:  David J.Edge
                                 Title: Director

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

                             THE BANK OF NEW YORK
                             Lender

                             By: /s/ Raymond J.Palmer
                                 ----------------------------------------------
                                 Name:  Raymond J. Palmer
                                 Title: Vice President

                             THE CHASE MANHATTAN BANK, TORONTO
                             BRANCH
                             Lender

                             By: /s/ Drew McDonald
                                 ----------------------------------------------
                                 Name:  Drew McDonald
                                 Title: Authorized Representative

                             By: /s/ Christine Chan
                                 ----------------------------------------------
                                 Name:  Christine Chan
                                 Title: Authorized Representative

                             THE FUJI BANK, LIMITED
                             Lender

                             By: /s/ Jacques Azagury
                                 ----------------------------------------------
                                 Name:  Jacques Azagury
                                 Title: Senior Vice President & Manager

                             UBS AG, STAMFORD BRANCH
                             Lender

                             By: /s/ Patricia O'Kicki
                                 ----------------------------------------------
                                 Name:  Patricia O'Kicki
                                 Title: Director
                                        Banking Products Services

                             By: /s/ Wilfred V. Saint
                                 ----------------------------------------------
                                 Name:  Wilfred V. Saint
                                 Title: Associate Director
                                        Banking Products Services, US

                             UMB BANK
                             Lender

                             By: /s/ Richard J. Lehrter
                                 ----------------------------------------------
                                 Name:  Richard J. Lehrter
                                 Title: Community Bank President

                                    Fifth Amendment to Canadian Credit Agreement
<PAGE>

                             WESTDEUTSCHE LANDESBANK
                             GIROZENTRALE
                             Lender

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

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

                                    Fifth Amendment to Canadian Credit Agreement

<PAGE>

                                                                 Fifth Amendment

                              CONSENT AND AGREEMENT

         Devon Energy Corporation, a Delaware corporation ("Canadian
Guarantor"), hereby (i) consents to the provisions of this Amendment and the
transactions contemplated herein, (ii) ratifies and confirms the Guaranty dated
as of August 29, 2000 made by it for the benefit of Canadian Agent and Lenders
executed pursuant to the Credit Agreement and the other Canadian Loan Documents,
(iii) agrees that all of its respective obligations and covenants thereunder
shall remain unimpaired by the execution and delivery of this Amendment and the
other documents and instruments executed in connection herewith, and (iv) agrees
that the Canadian Guaranty and such other Canadian Loan Documents shall remain
in full force and effect.

                                        DEVON ENERGY CORPORATION

                                        By: /s/ Dale T. Wilson
                                            -----------------------------------
                                            Name:  Dale T. Wilson
                                            Title: Treasurer

                                    Fifth Amendment to Canadian Credit Agreement

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