Document:

<PAGE>
                                                                     EXHIBIT 4.3

                          SECOND SUPPLEMENTAL INDENTURE

         THIS SUPPLEMENTAL INDENTURE (this "SUPPLEMENTAL INDENTURE"), dated as
of August 21, 2001, among Westport Resources Corporation, a company incorporated
under the laws of the State of Nevada, formerly known as Belco Oil & Gas Corp.
(the "COMPANY"), the undersigned Subsidiary Guarantors (each individually, a
"SUBSIDIARY GUARANTOR"), and The Bank of New York, a New York banking
corporation, as trustee under the indenture referred to below (the "TRUSTEE").

                                   WITNESSETH

         WHEREAS, the Company has heretofore executed and delivered to the
Trustee an indenture (as previously amended, the "INDENTURE"), dated as of
September 23, 1997, providing for the issuance of an aggregate principal amount
at maturity of $150,000,000 of 8?% Senior Subordinated Notes due 2007 (the
"NOTES");

         WHEREAS, Westport Resources Corporation, a Delaware corporation, has
merged into Belco Oil & Gas Corp., which has changed its name to Westport
Resources Corporation;

         WHEREAS, Section 4.16 of the Indenture provides that, under certain
circumstances, the Company is required to cause Subsidiary Guarantors to execute
and deliver to the Trustee a Subsidiary Guarantee on the terms and conditions
set forth herein;

         WHEREAS, Section 5.1 of the Indenture requires each existing Subsidiary
Guarantor to confirm its Subsidiary Guarantee upon the occurrence of a merger;
and

         WHEREAS, pursuant to Section 9.1 of the Indenture, the Company, the
Subsidiary Guarantors and the Trustee are authorized to execute and deliver this
Supplemental Indenture.

         NOW, THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt of which is hereby acknowledged, the
Company, the Subsidiary Guarantors and the Trustee mutually covenant and agree
for the equal and ratable benefit of the holders of the Notes as follows:

         1. CAPITALIZED TERMS.

                  Capitalized terms used herein without definition shall have
the meanings assigned to them in the Indenture.

         2. INDENTURE PROVISIONS PURSUANT TO WHICH GUARANTEE IS GIVEN.

                  This Supplemental Indenture is being executed and delivered
pursuant to Sections 4.16, 5.1 and 9.1 of the Indenture.

<PAGE>

         3. EXISTING SUBSIDIARY GUARANTORS.

                  Each Subsidiary Guarantor which is currently a party to the
Indenture executes this Supplemental Indenture (i) to ratify and confirm its
existing Subsidiary Guarantee as continuing to be in full force and effect and
(ii) evidence its agreement to the terms of this Supplemental Indenture.

         4. AGREEMENTS TO GUARANTEE.

                  Each new Subsidiary Guarantor hereby agrees as follows:

                  (a) The Subsidiary Guarantor, jointly and severally with all
other Subsidiary Guarantors, if any, unconditionally guarantees to each Holder
of a Note authenticated and delivered by the Trustee and to the Trustee and its
successors and assigns, regardless of the validity and enforceability of the
Indenture, the Notes and the obligations of the Company under the Indenture and
the Notes, that:

                           (i) the principal of, premium, if any, and interest
on the Notes shall be promptly paid in full when due, whether at maturity, by
acceleration, redemption or otherwise, and interest on the overdue principal of,
premium, if any, and interest on the Notes, to the extent lawful, and all other
obligations of the Company to the Holders or the Trustee thereunder shall be
promptly paid in full, all in accordance with the terms thereof; and

                           (ii) in case of any extension of time for payment or
renewal of any Notes or any of such other obligations, that the same shall be
promptly paid in full when due in accordance with the terms of the extension or
renewal, whether at maturity, by acceleration or otherwise.

                  Notwithstanding the foregoing, in the event that this
Subsidiary Guarantee would constitute or result in a violation of any applicable
fraudulent conveyance or similar law of any relevant jurisdiction, the liability
of the Subsidiary Guarantor under this Supplemental Indenture and its Subsidiary
Guarantee shall be limited to such amount as will not, after giving effect
thereto, and to all other liabilities of the Subsidiary Guarantor, result in
such amount constituting a fraudulent transfer or conveyance.

         5. SUBORDINATION.

                  The Subsidiary Guarantors agree, and each Holder by accepting
a Note agrees, that (a) the obligations of the Subsidiary Guarantors under this
Subsidiary Guarantee are subordinated in right of payment to the prior payment
in full (when due) of all existing and future Guarantor Senior Indebtedness of
the Subsidiary Guarantors, including without limitation any guarantee by the
Subsidiary Guarantors of the Indebtedness under the New Credit Facility or of
any Senior Debt of the Company or of any Guarantor Senior Indebtedness of any
other Subsidiary Guarantor, to the extent and in the matter provided in Article
10 (including, without limitation, Section 10.12) of the Indenture (as if the
Subsidiary Guarantor were the Company for purposes of such Article 10 and all
defined terms used therein, and the Guarantor Senior

                                       2
<PAGE>

Indebtedness of the Guarantor were Senior Debt), and this Subsidiary Guarantee
is made subject to such provisions (which are hereby incorporated herein by
reference), and (b) such subordination is for the benefit of and enforceable by
the holders of Guarantor Senior Indebtedness of the Subsidiary Guarantor.

         6. EXECUTION AND DELIVERY OF SUBSIDIARY GUARANTEE.

                  (a) To evidence its Subsidiary Guarantee set forth in this
Supplemental Indenture, each Subsidiary Guarantor hereby agrees that a notation
of such Subsidiary Guarantee substantially in the form of Annex A hereto shall
be endorsed by an officer of such Subsidiary Guarantor on each Note
authenticated and delivered by the Trustee after the date hereof.

                  (b) Notwithstanding the foregoing, each Subsidiary Guarantor
hereby agrees that its Subsidiary Guarantee set forth herein shall remain in
full force and effect notwithstanding any failure to endorse on each Note a
notation of such Subsidiary Guarantee.

                  (c) If an officer whose signature is on this Supplemental
Indenture or on the Subsidiary Guarantee no longer holds that office at the time
the Trustee authenticates the Note on which a Subsidiary Guarantee is endorsed,
the Subsidiary Guarantee shall be valid nevertheless.

                  (d) The delivery of a Note by the Trustee, after the
authentication thereof under the Indenture, shall constitute due delivery of the
Subsidiary Guarantee set forth in this Supplemental Indenture on behalf of the
Subsidiary Guarantor.

                  (e) Each Subsidiary Guarantor hereby agrees that its
obligations hereunder shall be unconditional, regardless of the validity,
regularity or enforceability of the Notes or the Indenture, the absence of any
action to enforce the same, any waiver or consent by any Holder of the Notes
with respect to any provisions hereof or thereof, the recovery of any judgment
against the Company, any action to enforce the same or any other circumstance
which might otherwise constitute a legal or equitable discharge or defense of a
guarantor.

                  (f) Each Subsidiary Guarantor hereby waives diligence,
presentment, demand of payment, filing of claims with a court in the event of
insolvency or bankruptcy of the Company, any right to require a proceeding first
against the Company, protest, notice and all demands whatsoever and covenants
that its Subsidiary Guarantee made pursuant to this Supplemental Indenture will
not be discharged except by complete performance of the obligations contained in
the Notes and the Indenture or pursuant to Section 7(b) of this Supplemental
Indenture.

                  (g) If the Trustee or any Holder has instituted any proceeding
to enforce any right or remedy under this Supplemental Indenture or under the
Subsidiary Guarantee made pursuant to this Supplemental Indenture and such
proceeding has been discontinued or abandoned for any reason, or has been
determined adversely to the Trustee or to such Holder, then, and in every such
case, subject to any determination in such proceeding, the Subsidiary Guarantor,
the Trustee and the Holders shall be restored severally and respectively to
their

                                       3
<PAGE>

former positions hereunder and thereafter all rights and remedies of the
Subsidiary Guarantor, the Trustee and the Holders shall continue as though no
such proceeding had been instituted.

                  (h) Each Subsidiary Guarantor hereby waives and will not in
any manner whatsoever claim or take the benefit or advantage of, any rights of
reimbursement, indemnity or subrogation or any other rights against the Company
or any other Subsidiary Guarantor as a result of any payment by such Subsidiary
Guarantor under its Subsidiary Guarantee. The Subsidiary Guarantor further
agrees that, as between the Subsidiary Guarantors, on the one hand, and the
Holders and the Trustee, on the other hand:

                           (i) the maturity of the obligations guaranteed hereby
may be accelerated as provided in Article 6 of the Indenture for the purposes of
the Subsidiary Guarantee made pursuant to this Supplemental Indenture,
notwithstanding any stay, injunction or other prohibition preventing such
acceleration in respect of the obligations guaranteed hereby; and

                           (ii) in the event of any declaration of acceleration
of such obligations as provided in such Article 6, such obligations (whether or
not due and payable) shall forthwith become due and payable by the Subsidiary
Guarantor for the purpose of the Subsidiary Guarantee made pursuant to this
Supplemental Indenture.

                  (i) The Subsidiary Guarantors shall have the right to seek
contribution from any other non-paying Subsidiary Guarantor, if any, so long as
the exercise of such right does not impair the rights of the Holders under the
Subsidiary Guarantee made pursuant to this Supplemental Indenture.

                  (j) Each Subsidiary Guarantor covenants (to the extent that it
may lawfully do so) that it will not at any time insist upon, or plead, or in
any manner whatsoever claim or take the benefit or advantage of, any stay,
extension or usury law wherever enacted, now or at any time hereafter in force,
which may affect the covenants or the performance of the Indenture or this
Subsidiary Guarantee; and each Subsidiary Guarantor (to the extent that it may
lawfully do so) hereby expressly waives all benefit or advantage of any such
law, and covenants that it will not hinder, delay or impede the execution of any
power herein granted to the Trustee, but will suffer and permit the execution of
every such power as though no such law had been enacted.

         7. SUBSIDIARY GUARANTORS MAY CONSOLIDATE, ETC. ON CERTAIN TERMS.

                  (a) Except as set forth in Articles 4 and 5 of the Indenture,
nothing contained in the Indenture, this Supplemental Indenture or in the Notes
shall prevent any consolidation or merger of a Subsidiary Guarantor with or into
the Company or any other Subsidiary Guarantor or shall prevent any transfer,
sale or conveyance of the property of the Subsidiary Guarantor as an entirety or
substantially as an entirety, to the Company or any other Subsidiary Guarantor.

                  (b) Except as set forth in Article 5 of the Indenture, upon
the sale or disposition of all of the Capital Stock of the Subsidiary Guarantor
by the Company or the Subsidiary of the Company, or upon the consolidation or
merger of the Subsidiary Guarantor

                                       4
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with or into any Person, or the sale of all or substantially all of the assets
of the Subsidiary Guarantor (in each case, other than to an Affiliate of the
Company), such Subsidiary Guarantor shall be deemed automatically and
unconditionally released and discharged from all obligations under this
Subsidiary Guarantee without any further action required on the part of the
Trustee or any Holder if no Default shall have occurred and be continuing;
provided, that in the event of an Asset Sale, the Net Proceeds therefrom are
treated in accordance with Section 4.10 of the Indenture. Except with respect to
transactions set forth in the preceding sentence, the Company and the Subsidiary
Guarantor covenant and agree that upon any such consolidation, merger or
transfer of assets, the performance of all covenants and conditions of this
Supplemental Indenture to be performed by such Subsidiary Guarantor shall be
expressly assumed by supplemental indenture satisfactory in form to the Trustee,
by the corporation formed by such consolidation, or into which the Subsidiary
Guarantor shall have merged, or by the corporation which shall have acquired
such property. Upon receipt of an Officer's Certificate of the Company or the
Subsidiary Guarantor, as the case may be, to the effect that the Company or such
Subsidiary Guarantor has complied with the first sentence of this Section 7(b),
the Trustee shall execute any documents reasonably requested by the Company or
the Subsidiary Guarantor, at the cost of the Company or such Subsidiary
Guarantor, as the case may be, in order to evidence the release of such
Subsidiary Guarantor from its obligations under its Guarantee endorsed on the
Notes and under the Indenture and this Supplemental Indenture.

         8. RELEASES UPON RELEASE OF GUARANTEE OF GUARANTEED INDEBTEDNESS.

                  Concurrently with the release or discharge of the Subsidiary
Guarantor's guarantee of the payment of (i) notes and other obligations under
that certain Indenture dated as of March 18, 1996, among Westport Resources
Corporation as successor to Coda Energy, Inc. (as issuer) and Chase Bank of
Texas, N.A. (f/k/a Texas Commerce Bank, N.A.) (as trustee) and (ii) the New
Credit Facility ("GUARANTEED DEBT") (other than a release or discharge by or as
a result of payment under such guarantee of Guaranteed Indebtedness), the
Subsidiary Guarantor shall be automatically and unconditionally released and
relieved of its obligations under this Supplemental Indenture and its Subsidiary
Guarantee made pursuant to Section 6 of this Supplemental Indenture. Upon
delivery by the Company to the Trustee of an Officer's Certificate to the effect
that such release or discharge has occurred, the Trustee shall execute any
documents reasonably required in order to evidence the release of the Subsidiary
Guarantor from its obligations under this Supplemental Indenture and its
Subsidiary Guarantee made pursuant hereto; provided such documents shall not
affect or impair the rights of the Trustee and Paying Agent under Section 7.7 of
the Indenture.

         9. NEW YORK LAW TO GOVERN.

                  The substantive law of the State of New York shall govern and
be used to construe this Supplemental Indenture.

                                       5
<PAGE>

         10. COUNTERPARTS.

                  The parties may sign any number of copies of this Supplemental
Indenture. Each signed copy shall be an original, but all of them together
represent the same agreement.

         11. RECITALS, ETC.

                  The recitals herein contained are made by the Company and the
Subsidiary Guarantors and not by the Trustee, and the Trustee assumes no
responsibility for the correctness thereof. The Trustee makes no representations
as to the validity or sufficiency of this Supplemental Indenture.

         12. EFFECT OF HEADINGS.

                  The Section headings herein are for convenience only and shall
not effect the construction hereof.

                            [SIGNATURE PAGE FOLLOWS]

                                       6
<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date first above
written.

                                   THE BANK OF NEW YORK,
                                   as Trustee

                                   By:      /s/ MARIE E. TRIMBOLI
                                            ------------------------------------
                                   Name:    Marie E. Trimboli
                                   Title:   Assistant Vice President

                                   WESTPORT RESOURCES CORPORATION

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   ELECTRA RESOURCES, INC.

                                   By:      /s/ DONALD D. WOLF
                                            ------------------------------------
                                   Name:    Donald D. Wolf
                                   Title:   President

                                   BOG WYOMING LLC

                                   By:  BELCO ENERGY CORP., Manager

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                       7
<PAGE>

                                   BELCO ENERGY CORP.

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   BELCO ENERGY I L.P.

                                   By:  BELCO ENERGY CORP., General Partner

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   GIN LANE COMPANY

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   FORTUNE CORP.

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   BELCO FINANCE CO.

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                       8
<PAGE>

                                   WESTPORT OIL AND GAS COMPANY, INC.

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   WESTPORT ARGENTINA LLC

                                   By:      /s/ DONALD. D. WOLF
                                            ------------------------------------
                                   Name:    Donald. D. Wolf
                                   Title:   Manager

                                   WESTPORT CANADA LLC

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Member

                                   By:      /s/  BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   JERRY CHAMBERS EXPLORATION COMPANY

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Managing Partner

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                       9
<PAGE>

                                   WESTPORT OVERRIDING ROYALTY LLC

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Manager

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                       10
<PAGE>

                        ANNEX A TO SUPPLEMENTAL INDENTURE

                FORM OF NOTATION OF SUBSIDIARY GUARANTEE ON NOTE

         Each Subsidiary Guarantor (as defined in the Indenture) has jointly and
severally unconditionally guaranteed (a) the due and punctual payment of the
principal of, premium, if any, and interest on the Notes, whether at Stated
Maturity or an Interest Payment Date, by acceleration, call for redemption or
otherwise, (b) the due and punctual payment of interest on the overdue principal
and premium of, and interest, to the extent lawful, on the Notes and (c) that in
case of any extension of time of payment or renewal of any Notes or any of such
other obligations, the same will be promptly paid in full when due in accordance
with the terms of the extension of renewal, whether at stated maturity, by
acceleration or otherwise.

         Notwithstanding the foregoing, in the event that the Subsidiary
Guarantee would constitute or result in a violation of any applicable fraudulent
conveyance or similar law of any relevant jurisdiction, the liability of the
Subsidiary Guarantor under its Subsidiary Guarantee shall be limited to such
amount as will not, after giving effect thereto, and to all other liabilities of
the Subsidiary Guarantor, result in such amount constituting a fraudulent
transfer or conveyance.

         This Subsidiary Guarantee shall not be valid or obligatory for any
purpose until the certificate of authentication on the Note upon which the
Subsidiary Guarantee is noted shall have been executed by the Trustee under the
Indenture by the manual signature of one of its authorized signatories.

Dated: August 21, 2001.

                                   WESTPORT OIL AND GAS COMPANY, INC.

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   WESTPORT ARGENTINA LLC

                                   By:      /s/ DONALD D. WOLF
                                            ------------------------------------
                                   Name:    Donald D. Wolf
                                   Title:   Manager

                                        1

<PAGE>

                                   WESTPORT CANADA LLC

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Member

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   JERRY CHAMBERS EXPLORATION COMPANY

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Managing Partner

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                   WESTPORT OVERRIDING ROYALTY LLC

                                   By: WESTPORT OIL AND GAS COMPANY, INC.,
                                   Manager

                                   By:      /s/ BARTH E. WHITHAM
                                            ------------------------------------
                                   Name:    Barth E. Whitham
                                   Title:   President

                                        2<PAGE>
                                                                     EXHIBIT 4.4

================================================================================

                              SUBSIDIARY GUARANTEE

                                     MADE BY

                             EACH OF THE GUARANTORS
                         FROM TIME TO TIME PARTY HERETO

                                   IN FAVOR OF

                              THE SEVERAL CREDITORS
                  FROM TIME TO TIME PARTY TO THE LOAN DOCUMENTS

                                       AND

                            THE CHASE MANHATTAN BANK,
                             AS ADMINISTRATIVE AGENT

                           DATED AS OF AUGUST 21, 2001

================================================================================

<PAGE>

                                TABLE OF CONTENTS

<Table>
<S>                                                                                                           <C>
SECTION 1 DEFINITIONS............................................................................................2
         1.1      Defined Terms..................................................................................2
SECTION 2 GUARANTEE..............................................................................................2
         2.1      Guarantee......................................................................................2
         2.2      Right of Contribution..........................................................................3
         2.3      Right of Set-off...............................................................................4
         2.4      No Subrogation.................................................................................4
         2.5      Amendments, etc. with respect to the Obligations; Waiver of Rights.............................4
         2.6      Guarantee Absolute and Unconditional...........................................................5
         2.7      Reinstatement..................................................................................6
         2.8      Payments.......................................................................................6
SECTION 3 REPRESENTATIONS AND WARRANTIES.........................................................................6
         3.1      Representations and Warranties.................................................................6
SECTION 4 COVENANTS..............................................................................................7
         4.1      Covenants......................................................................................7
         4.2      Authority of Administrative Agent..............................................................7
SECTION 5 MISCELLANEOUS..........................................................................................7
         5.1      Notices........................................................................................7
         5.2      Counterparts...................................................................................7
         5.3      Severability...................................................................................7
         5.4      Integration....................................................................................8
         5.5      Amendments in Writing; No Waiver; Cumulative Remedies..........................................8
         5.6      Loan Documents.................................................................................8
         5.7      Section Headings...............................................................................8
         5.8      Successors and Assigns.........................................................................8
         5.9      GOVERNING LAW..................................................................................8
         5.10     Submission to Jurisdiction; Waivers............................................................8
         5.11     Acknowledgments................................................................................9
         5.12     WAIVERS OF JURY TRIAL..........................................................................9
         5.13     Additional Obligors............................................................................9
         5.14     Release.......................................................................................10
</Table>

SCHEDULES
Schedule 1  Address for Notices
Schedule 2  Form of Assumption Agreement

                                       i

<PAGE>

                              SUBSIDIARY GUARANTEE

         SUBSIDIARY GUARANTEE, dated as of August 21, 2001, is made by each of
the entities that is a signatory hereto (each of the signatories hereto,
together with any other Restricted Subsidiary of the Borrower that becomes a
party hereto from time to time after the date hereof, the "Guarantors"), in
favor of THE CHASE MANHATTAN BANK, as administrative agent (in such capacity,
the "Administrative Agent") for the lenders (the "Lenders") parties to the
Credit Agreement and all other Creditors.

                                    RECITALS

         A. The Lenders have severally agreed to make Loans to and to
participate in Letters of Credit issued for the account of the Borrower upon the
terms and subject to the conditions set forth in the Credit Agreement dated as
of even date herewith (as such may be amended, supplemented or otherwise
modified from time to time, the "Credit Agreement"), among WESTPORT RESOURCES
CORPORATION, a Nevada corporation (the "Borrower"), the Lenders, the Syndication
Agents, the Documentation Agents and the Administrative Agent.

         B. Any Creditor may, but shall be under no obligation to, enter into
one or more Interest Rate Protection Agreement, Commodity Price Risk Management
Agreement, foreign currency exchange agreement, commodity price protection
agreement or other interest or currency exchange rate or commodity price hedging
arrangement with a Lender or an Affiliate of a Lender (such agreements or
arrangements being "Hedging Agreements").

         C. The Borrower owns directly or indirectly all of the issued and
outstanding Capital Stock of each Guarantor.

         D. The proceeds of the Loans, Letters of Credit and the Hedging
Agreements will be used in part to enable the Borrower to make valuable
transfers to each Guarantor in connection with the operation of its business.

         E. The Borrower and the Guarantors are engaged in related businesses,
and each Guarantor will derive substantial direct and indirect benefit from the
making of the Loans, the issuance of the Letters of Credit and the execution of
the Hedging Agreements.

         F. The Loans are necessary and convenient to the conduct, promotion and
attainment of the business of the Borrower and the Guarantors.

         G. To induce the Lenders to enter the Credit Agreement and to make the
Loans and participate in the Letters of Credit issued thereunder and to induce
the Creditors to enter into Hedging Agreements, the Guarantors have agreed to
guarantee the obligations of the Borrower under the Credit Agreement and of the
Loan Parties under the Hedging Agreements.

         H. Now, therefore, in consideration of the premises, the Guarantors
hereby agree with the Administrative Agent and the Creditors, as follows:

<PAGE>

                                    SECTION 1
                                   DEFINITIONS

         1.1 Defined Terms.

                  (a) Unless otherwise defined herein, each term defined in the
Credit Agreement and used herein shall have the meaning given to it in the
Credit Agreement.

                  (b) As used herein, "Creditor" means the Agents, any Lender or
any Affiliate of a Lender party to any Hedging Agreement with a Loan Party.

                  (c) As used herein, "Obligations" means the collective
reference to the unpaid principal of and interest on the Loans and Hedging
Agreements and all other obligations and liabilities of the Borrower or any
other Loan Party (including, without limitation, interest accruing at the then
applicable rate provided in the Credit Agreement after the maturity of the Loans
and interest accruing at the then applicable rate provided in the Credit
Agreement after the filing of any petition in bankruptcy, or the commencement of
any insolvency, reorganization or like proceeding, relating to the Borrower or
any of its Restricted Subsidiaries whether or not a claim for post-filing or
post-petition interest is allowed in such proceeding) to the Administrative
Agent or any Creditor, whether direct or indirect, absolute or contingent, due
or to become due, or now existing or hereafter incurred, which may arise under,
out of, or in connection with, the Credit Agreement, any Note, this Guarantee,
any Hedging Agreement, any other Loan Document or any other document made,
delivered or given in connection therewith, whether on account of principal,
interest, reimbursement obligations, fees, indemnities, costs, expenses or
otherwise (including, without limitation, all fees and disbursements of counsel
to the Administrative Agent or to the Creditors that are required to be paid by
the Borrower or any Guarantor pursuant to the terms of the Credit Agreement or
this Guarantee or any other Loan Document).

                  (d) As used herein, "Loan Document" means the Credit
Agreement, any Note, the Pledge Agreement, this Guarantee, the L/C Applications
and any Hedging Agreement.

                  (e) The words "hereof," "herein" and "hereunder" and words of
similar import when used in this Guarantee shall refer to this Guarantee as a
whole and not to any particular provision of this Guarantee, and section and
paragraph references are to this Guarantee unless otherwise specified.

                  (f) The meanings given to terms defined herein shall be
equally applicable to both the singular and plural forms of such terms.

                                    SECTION 2
                                    GUARANTEE

         2.1 Guarantee.

                  (a) Subject to the provisions of subsection 2.1(b), each of
the Guarantors hereby, jointly and severally, unconditionally and irrevocably,
guarantees to the Administrative Agent and the Creditors and their respective
successors, indorsees, transferees and assigns, the

                                       2
<PAGE>

prompt and complete payment and performance by the Borrower when due (whether at
the stated maturity, by acceleration or otherwise) of the Obligations.

                  (b) Anything herein or in any other Loan Document to the
contrary notwithstanding, the maximum liability of each Guarantor hereunder and
under the other Loan Documents shall in no event exceed the amount which can be
guaranteed by such Guarantor under applicable federal and state laws relating to
the insolvency of debtors.

                  (c) Each Guarantor further agrees to pay any and all expenses
(including, without limitation, all reasonable fees and disbursements of
counsel) which may be paid or incurred by the Administrative Agent or any
Creditor in enforcing, or obtaining advice of counsel in respect of, any rights
with respect to, or collecting, any or all of the Obligations and/or enforcing
any rights with respect to, or collecting against, such Guarantor under this
Guarantee. This Guarantee shall remain in full force and effect until the
Obligations are paid in full and the Aggregate Commitments are terminated,
notwithstanding that from time to time prior thereto no amounts may be
outstanding under the Credit Agreement.

                  (d) Each Guarantor agrees that the Obligations may at any time
and from time to time exceed the amount of the liability of such Guarantor
hereunder without impairing this Guarantee or affecting the rights and remedies
of the Administrative Agent or any Creditor hereunder.

                  (e) No payment or payments made by the Borrower, the
Guarantor, any other guarantor or any other Person or received or collected by
the Administrative Agent or any Creditor from the Borrower, any Guarantor, any
other guarantor or any other Person by virtue of any action or proceeding or any
set-off or appropriation or application at any time or from time to time in
reduction of or in payment of the Obligations shall be deemed to modify, reduce,
release or otherwise affect the liability of any Guarantor hereunder which
shall, notwithstanding any such payment or payments (other than payments made by
the Borrower or such Guarantor in respect of the Obligations or payments
received or collected from such Guarantor in respect of the Obligations), remain
liable for the Obligations up to the maximum liability of such Guarantor
hereunder until the Obligations are paid in full and the Aggregate Commitments
are terminated.

                  (f) Each Guarantor agrees that whenever, at any time, or from
time to time, it shall make any payment to the Administrative Agent or any
Creditor on account of its liability hereunder, it will notify the
Administrative Agent in writing that such payment is made under this Guarantee
for such purpose.

         2.2 Right of Contribution. Each Guarantor hereby agrees that to the
extent that a Guarantor shall have paid more than its proportionate share of any
payment made hereunder, such Guarantor shall be entitled to seek and receive
contribution from and against any other Guarantor hereunder who has not paid its
proportionate share of such payment. Each Guarantor's right of contribution
shall be subject to the terms and conditions of subsection 2.4 hereof. The
provisions of this subsection shall in no respect limit the obligations and
liabilities of any Guarantor to the Administrative Agent and the Creditors, and
each Guarantor shall remain liable to the Administrative Agent and the Creditors
for the full amount guaranteed by such Guarantor hereunder.

                                       3
<PAGE>

         2.3 Right of Set-off. During the continuance of any Event of Default,
each Guarantor hereby irrevocably authorizes each Creditor at any time and from
time to time without notice to such Guarantor or any other Guarantor, any such
notice being expressly waived by each Guarantor, to set-off and appropriate and
apply any and all deposits (general or special, time or demand, provisional or
final, but excluding deposits held by such Guarantor as a fiduciary for others),
in any currency, and any other credits, indebtedness or claims, in any currency,
in each case whether direct or indirect, absolute or contingent, matured or
unmatured, at any time held or owing by such Creditor to or for the credit or
the account of such Guarantor, or any part thereof in such amounts as such
Creditor may elect, against and on account of the obligations and liabilities of
such Guarantor to such Creditor hereunder and claims of every nature and
description of such Creditor against such Guarantor, in any currency, whether
arising hereunder, under the Credit Agreement, any Note, any Loan Documents or
otherwise, as such Creditor may elect, whether or not the Administrative Agent
or any Creditor has made any demand for payment and although such obligations,
liabilities and claims may be contingent or unmatured. Such Creditor shall
notify such Guarantor and the Administrative Agent promptly of any such set-off
and the application made by such Creditor, provided that the failure to give
such notice shall not affect the validity of such set-off and application. The
rights of each Creditor under this subsection are in addition to other rights
and remedies (including, without limitation, other rights of set-off) which the
Administrative Agent or such Creditor may have.

         2.4 No Subrogation. Notwithstanding any payment or payments made by any
of the Guarantors hereunder or any set-off or application of funds of any of the
Guarantors by any Creditor, no Guarantor shall be entitled to be subrogated to
any of the rights of the Administrative Agent or any Creditor against the
Borrower or any other Guarantor or any collateral security or guarantee or right
of offset held by any Creditor for the payment of the Obligations until all
amounts owing to the Administrative Agent and the Creditors by the Borrower on
account of the Obligations are paid in full and the Aggregate Commitments are
terminated, nor shall any Guarantor seek or be entitled to seek any contribution
or reimbursement from the Borrower or any other Guarantor in respect of payments
made by such Guarantor hereunder until all amounts owing to the Administrative
Agent and the Creditors by the Borrower on account of the Obligations are paid
in full and the Aggregate Commitments are terminated. If any amount shall be
paid to any Guarantor on account of such subrogation rights at any time when all
of the Obligations shall not have been paid in full, such amount shall be held
by such Guarantor in trust for the Administrative Agent and the Creditors,
segregated from other funds of such Guarantor, and shall, forthwith upon receipt
by such Guarantor, be turned over to the Administrative Agent in the exact form
received by such Guarantor (duly indorsed by such Guarantor to the
Administrative Agent, if required), to be applied against the Obligations,
whether matured or unmatured, in such order as the Administrative Agent may
determine.

         2.5 Amendments, etc. with respect to the Obligations; Waiver of Rights.
Each Guarantor shall remain obligated hereunder notwithstanding that, without
any reservation of rights against any Guarantor and without notice to or further
assent by any Guarantor: (a) any demand for payment of any of the Obligations
made by the Administrative Agent or any Creditor may be rescinded by such party
and any of the Obligations continued; (b) the Obligations, or the liability of
any other party upon or for any part thereof, or any collateral security or
guarantee therefor or right of offset with respect thereto, may, from time to
time, in whole or in part, be renewed, extended, amended, modified, accelerated,
compromised, waived, surrendered or

                                       4
<PAGE>

released by the Administrative Agent or any Creditor (with the consent of the
applicable Loan Parties where required by the terms hereof or thereof); (c) the
Credit Agreement, the Notes and the other Loan Documents and any other documents
executed and delivered in connection therewith may be amended, modified,
supplemented or terminated, in whole or in part, as the Administrative Agent (or
the Lenders or the Required Lenders, as the case may be) and the applicable Loan
Parties may deem advisable from time to time; and (d) any collateral security,
guarantee or right of offset at any time held by the Administrative Agent or any
Creditor for the payment of the Obligations may be sold, exchanged, waived,
surrendered or released. Neither the Administrative Agent nor any Creditor shall
have any obligation to protect, secure, perfect or insure any Lien at any time
held by it as security for the Obligations or for this Guarantee or any property
subject thereto. When making any demand hereunder against any of the Guarantors,
the Administrative Agent or any Creditor may, but shall be under no obligation
to, make a similar demand on the Borrower or any other Guarantor or guarantor,
and any failure by the Administrative Agent or any Creditor to make any such
demand or to collect any payments from the Borrower or any such other Guarantor
or guarantor or any release of the Borrower or such other Guarantor or guarantor
shall not relieve any of the Guarantors in respect of which a demand or
collection is not made or any of the Guarantors not so released of their several
obligations or liabilities hereunder, and shall not impair or affect the rights
and remedies, express or implied, or as a matter of law, of the Administrative
Agent or any Creditor against any of the Guarantors. For the purposes hereof
"demand" shall include the commencement and continuance of any legal
proceedings.

         2.6 Guarantee Absolute and Unconditional. Each Guarantor waives any and
all notice of the creation, renewal, extension or accrual of any of the
Obligations and notice of or proof of reliance by the Administrative Agent or
any Creditor upon this Guarantee or acceptance of this Guarantee, the
Obligations, and any of them, shall conclusively be deemed to have been created,
contracted or incurred, or renewed, extended, amended or waived, in reliance
upon this Guarantee. All dealings between the Borrower and any of the
Guarantors, on the one hand, and the Administrative Agent and the Creditors, on
the other hand, likewise shall be conclusively presumed to have been had or
consummated in reliance upon this Guarantee. Each Guarantor waives diligence,
presentment, protest, demand for payment and notice of default or nonpayment to
or upon the Borrower or any of the Guarantors with respect to the Obligations.
Each Guarantor understands and agrees that this Guarantee shall be construed as
a continuing, absolute and unconditional guarantee of payment without regard to
(a) the validity, regularity or enforceability of the Credit Agreement, any Note
or any other Loan Document, any of the Obligations or any other collateral
security therefor or guarantee or right of offset with respect thereto at any
time or from time to time held by the Administrative Agent or any Creditor, (b)
any defense, set-off or counterclaim (other than a defense of payment or
performance) which may at any time be available to or be asserted by the
Borrower against the Administrative Agent or any Creditor, or (c) any other
circumstance whatsoever (with or without notice to or knowledge of the Borrower
or such Guarantor) which constitutes, or might be construed to constitute, an
equitable or legal discharge of the Borrower for the Obligations, or of such
Guarantor under this Guarantee, in bankruptcy or in any other instance. When
pursuing its rights and remedies hereunder against any Guarantor, the
Administrative Agent and any Creditor may, but shall be under no obligation to,
pursue such rights and remedies as it may have against the Borrower or any other
Person or against any collateral security or guarantee for the Obligations or
any right of offset with respect thereto, and any failure by the Administrative
Agent or any

                                       5
<PAGE>

Creditor to pursue such other rights or remedies or to collect any payments from
the Borrower or any such other Person or to realize upon any such collateral
security or guarantee or to exercise any such right of offset, or any release of
the Borrower or any such other Person or any such collateral security, guarantee
or right of offset, shall not relieve such Guarantor of any liability hereunder,
and shall not impair or affect the rights and remedies, whether express, implied
or available as a matter of law, of the Administrative Agent and the Creditors
against such Guarantor. This Guarantee shall remain in full force and effect and
be binding in accordance with and to the extent of its terms upon each Guarantor
and the successors and assigns thereof, and shall inure to the benefit of the
Administrative Agent and the Creditors, and their respective successors,
indorsees, transferees and assigns, until all the Obligations and the
obligations of each Guarantor under this Guarantee shall have been satisfied by
payment in full and the Aggregate Commitments shall be terminated,
notwithstanding that from time to time during the term of the Credit Agreement
no amounts may be outstanding under the Credit Agreement.

         2.7 Reinstatement. This Guarantee shall continue to be effective, or be
reinstated, as the case may be, if at any time payment, or any part thereof, of
any of the Obligations is rescinded or must otherwise be restored or returned by
the Administrative Agent or any Creditor upon the insolvency, bankruptcy,
dissolution, liquidation or reorganization of the Borrower or any Guarantor, or
upon or as a result of the appointment of a receiver, intervenor or conservator
of, or trustee or similar officer for, the Borrower or any Guarantor or any
substantial part of its property, or otherwise, all as though such payments had
not been made.

         2.8 Payments. Each Guarantor hereby guarantees that payments hereunder
will be paid to the Administrative Agent without set-off or counterclaim in U.S.
Dollars at the office of the Administrative Agent located at 270 Park Avenue,
New York, New York 10017.

                                    SECTION 3
                         REPRESENTATIONS AND WARRANTIES

         3.1 Representations and Warranties. Each Guarantor hereby represents
and warrants that, in the case of such Guarantor, the representations and
warranties set forth in Section 5 of the Credit Agreement as they relate to such
Guarantor or to the other Loan Documents to which such Guarantor is a party,
each of which is hereby incorporated herein by reference, are true and correct,
and the Administrative Agent and each Creditor shall be entitled to rely on each
of them as if they were fully set forth herein, provided that each reference in
each such representation and warranty to the Borrower's knowledge shall, for the
purposes of this Section 3, be deemed to be a reference to such Guarantor's
knowledge.

         Each Guarantor agrees that the foregoing representations and warranties
shall be deemed to have been made by such Guarantor on the date of (a) each Loan
or (b) the issuance of any Letter of Credit under the Credit Agreement or (c)
each Hedging Agreement on and as of such date as though made hereunder on and as
of such date (except to the extent that such representations and warranties are
expressly made only as of an earlier date, in which case such representations
and warranties shall have been true and correct on and as of such earlier date).

                                       6
<PAGE>

                                    SECTION 4
                                    COVENANTS

         4.1 Covenants. Each Guarantor hereby covenants and agrees with the
Administrative Agent and each Creditor that, from and after the date of this
Guarantee until the Obligations are paid in full and the Aggregate Commitments
are terminated, such Guarantor shall take, or shall refrain from taking, as the
case may be, each action that is necessary to be taken or not taken, as the case
may be, so that no Default or Event of Default is caused by the failure to take
such action or to refrain from taking such action by such Guarantor or any of
its Subsidiaries.

         4.2 Authority of Administrative Agent. Each Guarantor acknowledges that
the rights and responsibilities of the Administrative Agent under this Guarantee
with respect to any action taken by the Administrative Agent or the exercise or
non-exercise by the Administrative Agent of any option, right, request, judgment
or other right or remedy provided for herein or resulting or arising out of this
Guarantee shall, as between the Administrative Agent and the other Creditors, be
governed by the Credit Agreement and by such other agreements with respect
thereto as may exist from time to time among them, but, as between the
Administrative Agent and such Guarantor, the Administrative Agent shall be
conclusively presumed to be acting as agent for the Creditors with full and
valid authority so to act or refrain from acting in the manner set forth in
Section 10 of the Credit Agreement, and no Guarantor shall be under any
obligation, or entitlement, to make any inquiry respecting such authority.

                                    SECTION 5
                                  MISCELLANEOUS

         5.1 Notices. All notices, requests and demands to or upon the
Administrative Agent or any Guarantor to be effective shall be in writing
(including by facsimile transmission) and, unless otherwise expressly provided
herein, shall be deemed to have been duly given or made (a) in the case of
delivery by hand or by courier service, when delivered, (b) in the case of
delivery by mail, three Business Days after being deposited in the mails,
postage prepaid, or (c) in the case of delivery by facsimile transmission, when
sent and receipt has been confirmed, addressed (x) if to the Administrative
Agent, at its address or transmission number for notices provided in subsection
11.2 of the Credit Agreement and (y) if to any Guarantor, at its address or
transmission number for notices set forth on Schedule 1 hereto. The
Administrative Agent and any Guarantor may change its address and transmission
numbers for notices by notice in the manner provided in this subsection 5. 1.

         5.2 Counterparts. This Guarantee may be executed by one or more of the
Guarantors on any number of separate counterparts, and all of said counterparts
taken together shall be deemed to constitute one and the same instrument. A set
of the counterparts of this Guarantee signed by all the Guarantors shall be
lodged with the Administrative Agent.

         5.3 Severability. Any provision of this Guarantee which is prohibited
or unenforceable in any jurisdiction shall, as to such jurisdiction, be
ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

                                       7
<PAGE>

         5.4 Integration. This Guarantee represents the agreement of each
Guarantor with respect to the subject matter hereof and there are no promises,
undertakings, representations or warranties by the Administrative Agent or any
Creditor relative to the subject matter hereof not reflected herein.

         5.5 Amendments in Writing; No Waiver; Cumulative Remedies.

                  (a) None of the terms or provisions of this Guarantee may be
waived, amended, supplemented or otherwise modified except by a written
instrument executed by each Guarantor and the Administrative Agent in accordance
with subsection 11. 1 of the Credit Agreement.

                  (b) Neither the Administrative Agent nor any Creditor shall by
any act (except by a written instrument pursuant to subsection 5.5(a) hereof),
delay, indulgence, omission or otherwise be deemed to have waived any right or
remedy hereunder or to have acquiesced in any Default or Event of Default or in
any breach of any of the terms and conditions hereof. No failure to exercise and
no delay in exercising, on the part of the Administrative Agent or any Creditor,
any right, remedy, power or privilege hereunder shall operate as a waiver
thereof; nor shall any single or partial exercise of any right, remedy, power or
privilege hereunder preclude any other or farther exercise thereof or the
exercise of any other right, remedy, power or privilege. A waiver by the
Administrative Agent or any Creditor of any right or remedy hereunder on any one
occasion shall not be construed as a bar to any right or remedy which the
Administrative Agent or such Creditor would otherwise have on any future
occasion.

                  (c) The rights and remedies herein provided are cumulative and
not exclusive of any other rights, remedies, powers and privileges provided by
law.

         5.6 Loan Documents. Each Guarantor agrees that this Guarantee shall
constitute a "Loan Document" under the Credit Agreement and that they shall be
deemed to be "Loan Parties", as such term is defined in the Credit Agreement.

         5.7 Section Headings. The section headings used in this Guarantee are
for convenience of reference only and are not to affect the construction hereof
or be taken into consideration in the interpretation hereof.

         5.8 Successors and Assigns. This Guarantee shall be binding upon the
successors and assigns of each Guarantor and shall inure to the benefit of the
Administrative Agent and the Creditors and their successors and assigns.

         5.9 GOVERNING LAW. THIS GUARANTEE AND THE RIGHTS AND OBLIGATIONS OF THE
PARTIES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED IN
ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK WITHOUT REGARD TO CONFLICTS OF
LAW PRINCIPLES THAT WOULD RESULT IN THE APPLICATION OF THE LAWS OF A DIFFERENT
JURISDICTION.

         5.10 Submission to Jurisdiction; Waivers. Each Guarantor hereby
irrevocably and unconditionally:

                                       8
<PAGE>

                  (a) submits for itself and its Property in any legal action or
proceeding relating to this Agreement and the other Loan Documents to which it
is a party, or for recognition and enforcement of any judgment in respect
thereof, to the non-exclusive general jurisdiction of the Courts of the State of
New York, the courts of the United States of America for the Southern District
of New York, and appellate courts from any thereof;

                  (b) consents that any such action or proceeding may be brought
in such courts and waives any objection that it may now or hereafter have to the
venue of any such action or proceeding in any such court or that such action or
proceeding was brought in an inconvenient court and agrees not to plead or claim
the same;

                  (c) agrees that service of process in any such action or
proceeding may be effected by mailing a copy thereof by registered or certified
mail (or any substantially similar form of mail), postage prepaid, to the
Guarantor at its address set forth in Schedule 1 hereto or at such other address
of which the Administrative Agent shall have been notified pursuant to
subsection 5.1;

                  (d) agrees that nothing herein shall affect the right to
effect service of process in any other manner permitted by law or shall limit
the right to sue in any other jurisdiction; and

                  (e) waives, to the maximum extent not prohibited by law, any
right it may have to claim or recover in any legal action or proceeding referred
to in this subsection any special, exemplary, punitive or consequential damages.

         5.11 Acknowledgments. Each Guarantor hereby acknowledges that:

                  (a) it has been advised by counsel in the negotiation,
execution and delivery of this Agreement and the other Loan Documents;

                  (b) no Agent nor any Creditor has any fiduciary relationship
with or duty to such Guarantor arising out of or in connection with this
Agreement or any of the other Loan Documents, and the relationship between the
Agents and the Creditors, on one hand, and such Guarantor, on the other hand, in
connection herewith or therewith is solely that of guarantor and creditor; and

                  (c) no joint venture is created hereby or by the other Loan
Documents or otherwise exists by virtue of the transactions contemplated hereby
among the Agents and the other Creditors or among the Borrower, the Agents and
the other Creditors.

         5.12 WAIVERS OF JURY TRIAL. THE PARTIES HERETO HEREBY KNOWINGLY AND
INTENTIONALLY, IRREVOCABLY AND UNCONDITIONALLY WAIVE TRIAL BY JURY IN ANY LEGAL
ACTION OR PROCEEDING RELATING TO THIS AGREEMENT OR ANY OTHER LOAN DOCUMENT AND
FOR ANY COUNTERCLAIM THEREIN.

         5.13 Additional Obligors. Each Restricted Subsidiary of the Borrower
that is required to become a party to this Guarantee pursuant to subsection
7.9(c) of the Credit Agreement shall become a Guarantor for all purposes of this
Guarantee upon execution and delivery by such

                                       9
<PAGE>

Subsidiary of an assumption agreement in the form of Schedule 2 hereto (each an
"Assumption Agreement").

         5.14 Release. At the request and sole expense of the Borrower, a
Guarantor shall be released from its obligations hereunder in the event that all
the capital stock of such Guarantor shall be sold, transferred or otherwise
disposed of in a transaction permitted by the Credit Agreement; provided that
the Borrower shall have delivered to the Administrative Agent, at least five
Business Days prior to the date of the proposed release, a written request for
release identifying the relevant Guarantor and the terms of the sale or other
disposition in reasonable detail, including the price thereof and any expenses
in connection therewith, together with a certification by the Borrower stating
that such transaction is in compliance with the Credit Agreement and the other
Loan Documents.

                                       10
<PAGE>

IN WITNESS WHEREOF, each of the undersigned has caused this Guarantee to be duly
executed and delivered by its duly authorized officer as of the day and year
first above written.

                                      BELCO ENERGY CORP.

                                      By: /s/ LON MCCAIN
                                         ---------------------------------------
                                            Lon McCain, Treasurer

                                      BELCO ENERGY I L.P.
                                         by Belco Energy Corp., general partner,
                                         a Nevada corporation

                                         By: /s/ LON MCCAIN
                                            ------------------------------------
                                               Lon McCain, Treasurer

                                      BELCO FINANCE CO.

                                      By: /s/ LON MCCAIN
                                         ---------------------------------------
                                               Lon McCain, Treasurer

                                      BOG WYOMING LLC
                                         by Belco Energy Corp., manager,
                                         a Nevada corporation

                                         By: /s/ LON MCCAIN
                                            ------------------------------------
                                               Lon McCain, Treasurer

                                      ELECTRA RESOURCES, INC.

                                      By: /s/ DONALD D. WOLF
                                         ---------------------------------------
                                               Donald D. Wolf, President

                                       11
<PAGE>

                                      FORTUNE CORP.

                                      By: /s/ BARTH E. WHITHAM
                                         ---------------------------------------
                                               Barth E. Whitham, President

                                      GIN LANE COMPANY

                                      By: /s/ LON MCCAIN
                                         ---------------------------------------
                                               Lon McCain, Treasurer

                                      JERRY CHAMBERS EXPLORATION COMPANY
                                         by Westport Oil and Gas Company, Inc.,
                                         general partner,
                                         a Delaware corporation

                                         By: /s/ LON MCCAIN
                                            ------------------------------------
                                               Lon McCain, Vice President and
                                               Chief Financial Officer

                                      WESTPORT ARGENTINA LLC

                                      By: /s/ DONALD D. WOLF
                                         ---------------------------------------
                                               Donald D. Wolf, Manager

                                       12
<PAGE>

                                      WESTPORT CANADA LLC
                                         by Westport Oil and Gas Company, Inc.,
                                         member,
                                         a Delaware corporation

                                         By: /s/ LON MCCAIN
                                            ------------------------------------
                                               Lon McCain, Vice President and
                                               Chief Financial Officer

                                      WESTPORT OVERRIDING ROYALTY LLC
                                         by Westport Oil and Gas Company, Inc.,
                                         manager,
                                         a Delaware corporation

                                         By: /s/ LON MCCAIN
                                            ------------------------------------
                                               Lon McCain, Vice President and
                                               Chief Financial Officer

                                      WESTPORT OIL AND GAS COMPANY, INC.

                                      By: /s/ LON MCCAIN
                                         ---------------------------------------
                                            Lon McCain, Vice President and
                                            Chief Financial Officer

                                       13
<PAGE>

                                   SCHEDULE 1
                               ADDRESS FOR NOTICES

<Table>
<S>                                               <C>
Belco Energy Corp.                                   Belco Energy I L.P.
735 Pineland Drive                                   735 Pineland Drive
Suite 300                                            Suite 300
Dallas, Texas 75231                                  Dallas, Texas 75231
Phone: (214) 692-1800                                Phone: (214) 692-1800
Fax: (214) 265-4777                                  Fax: (214) 265-4777
Attention: Grant Henderson                           Attention: Grant Henderson

Belco Finance Co.                                    BOG Wyoming LLC
735 Pineland Drive                                   735 Pineland Drive
Suite 300                                            Suite 300
Dallas, Texas 75231                                  Dallas, Texas 75231
Phone: (214) 692-1800                                Phone: (214) 692-1800
Fax: (214) 265-4777                                  Fax: (214) 265-4777
Attention: Grant Henderson                           Attention: Grant Henderson

Electra Resources, Inc.                              Fortune Corp.
735 Pineland Drive                                   735 Pineland Drive
Suite 300                                            Suite 300
Dallas, Texas 75231                                  Dallas, Texas 75231
Phone: (214) 692-1800                                Phone: (214) 692-1800
Fax: (214) 265-4777                                  Fax: (214) 265-4777
Attention: Grant Henderson                           Attention: Grant Henderson

Gin Lane Company                                     Jerry Chambers Exploration Company
735 Pineland Drive                                   410 Seventeenth Street
Suite 300                                            Suite 2300
Dallas, Texas 75231                                  Denver, Colorado 80202
Phone: (214) 692-1800                                Phone: (303) 575-0119
Fax: (214) 265-4777                                  Fax: (303) 575-0172
Attention: Grant Henderson                           Attention: Lon McCain

Westport Argentina LLC                               Westport Canada LLC
410 Seventeenth Street                               410 Seventeenth Street
Suite 2300                                           Suite 2300
Denver, Colorado 80202                               Denver, Colorado 80202
Phone: (303) 575-0119                                Phone: (303) 575-0119
Fax: (303) 575-0172                                  Fax: (303) 575-0172
Attention: Lon McCain                                Attention: Lon McCain
</Table>

                                 Schedule 1 - 1
<PAGE>

<Table>
<S>                                               <C>
Westport Oil and Gas Co., Inc.                       Westport Overriding Royalty LLC
410 Seventeenth Street                               410 Seventeenth Street
Suite 2300                                           Suite 2300
Denver, Colorado 80202                               Denver, Colorado 80202
Phone: (303) 575-0119                                Phone: (303) 575-0119
Fax: (303) 575-0172                                  Fax: (303) 575-0172
Attention: Lon McCain                                Attention: Lon McCain
</Table>

                                 Schedule 1 - 2
<PAGE>

                                   SCHEDULE 2
                                  TO GUARANTEE

                          FORM OF ASSUMPTION AGREEMENT

         ASSUMPTION AGREEMENT, dated as of _________________, 200__, is made by
_________________________________, a _______________________ (the "Additional
Obligor"), in favor of THE CHASE MANHATTAN BANK as administrative agent (in such
capacity, the "Administrative Agent") for the banks and other financial
institutions (the "Lenders") parties to the Credit Agreement referred to below
and all other Creditors. All capitalized terms not defined herein shall have the
meaning ascribed to them in such Credit Agreement.

                                    RECITALS

         A. Westport Resources Corporation, a Nevada corporation (the
"Borrower"), the Administrative Agent, the Syndication Agents, the Documentation
Agents, and the Lenders have entered into a Credit Agreement, dated as of August
21, 2001 (as amended, supplemented or otherwise modified from time to time, the
"Credit Agreement").

         B. In connection with the Credit Agreement, certain Restricted
Subsidiaries (other than the Additional Obligor) have entered into the
Guarantee, dated as of even date with the Credit Agreement (as amended,
supplemented or otherwise modified from time to time, the "Guarantee") in favor
of the Administrative Agent and the Creditors.

         C. The Credit Agreement requires the Additional Obligor to become a
party to the Guarantee.

         D. The Additional Obligor has agreed to execute and deliver this
Assumption Agreement in order to become a party to the Guarantee.

         E. Now, therefore, it is agreed:

         1. Guarantee. By executing and delivering this Assumption Agreement,
the Additional Obligor, as provided in subsection 5.13 of the Guarantee, hereby
becomes a party to the Guarantee as a Guarantor thereunder with the same force
and effect as if originally named therein as a Guarantor and, without limiting
the generality of the foregoing, hereby expressly assumes all obligations and
liabilities of a Guarantor thereunder and expressly guarantees, jointly and
severally, to the Creditors the Obligations. The Additional Obligor hereby
represents and warrants that each of the representations and warranties
contained in Section 3 of the Guarantee is true and correct on and as of the
date hereof (after giving effect to this Assumption Agreement) as if made on and
as of such date.

         2. GOVERNING LAW. THIS ASSUMPTION AGREEMENT AND THE RIGHTS AND
OBLIGATIONS OF THE PARTIES HEREUNDER SHALL BE GOVERNED BY, AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK WITHOUT REGARD
TO CONFLICT OF

                                 Schedule 2 - 1
<PAGE>

LAW PRINCIPLES THAT WOULD RESULT IN THE APPLICATION OF THE LAWS OF A DIFFERENT
JURISDICTION.

         IN WITNESS WHEREOF, the undersigned has caused this Assumption
Agreement to be duly executed and delivered as of the date first above written.

                                        [ADDITIONAL OBLIGOR]

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

                                 Schedule 2 - 2

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00031-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00031-of-00352.parquet"}]]