Document:

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                                                                   EXHIBIT 10.26

                                TABLE OF CONTENTS

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                                    ARTICLE I

                           PURCHASE AND SALE OF ASSETS

Section 1.01.     Purchased Assets...............................................................................1
Section 1.02.     Effective Date.................................................................................2
Section 1.03.     Excluded Assets................................................................................2
Section 1.04.     Permitted Encumbrances.........................................................................3

                                 PURCHASE PRICE

Section 2.01.     Consideration..................................................................................4
Section 2.02.     Preliminary Settlement Statement...............................................................4

                                     CLOSING

Section 3.01.     The Closing....................................................................................4
Section 3.02.     Seller's Closing Deliveries....................................................................4
Section 3.03.     Purchaser's Closing Deliveries.................................................................5
Section 3.04.     Payment at Closing.............................................................................5

                         REPRESENTATIONS AND WARRANTIES

Section 4.01.     Representations and Warranties of Purchaser....................................................5
Section 4.02.     Representations and Warranties of Seller.......................................................6
Section 4.03.     Disclaimer.....................................................................................8

                      OPERATIONS PRIOR TO THE CLOSING DATE

Section 5.01.     Operation of Properties Pending the Closing Date...............................................9

                                   ARTICLE VI

              ACCESS TO PURCHASED ASSETS PRIOR TO THE CLOSING DATE

Section 6.01.     Records and Personnel.........................................................................10
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                                   ARTICLE VII

                            ASSUMPTION AND INDEMNITY

Section 7.01.     Seller's Obligations and Liabilities..........................................................10
Section 7.02.     Purchaser's Obligations and Liabilities.......................................................10

                                  TITLE MATTERS

Section 8.01.     Warranty of Title.............................................................................11
Section 8.02.     Title Defects.................................................................................11

                                  ENVIRONMENTAL

Section 9.01.     Availability of Data to Purchaser; Phase I Environmental Audit................................12
Section 9.02.     Environmental Defects.........................................................................12

                                    ARTICLE X

                        CONDITIONS TO OBLIGATION TO CLOSE

Section 10.01.    Conditions to Obligation of Seller............................................................13
Section 10.02.    Conditions to Obligation of Purchaser.........................................................14

                                   ARTICLE XI

             REMEDIES FOR BREACHES OF THIS AGREEMENT OR FOR DEFECTS

Section 11.01.    Survival of Representations and Warranties....................................................14
Section 11.02.    Indemnification Provisions for the Benefit of Purchaser.......................................15
Section 11.03.    Indemnification Provisions for Benefit of the Seller..........................................15
Section 11.04.    Matters Involving Third Parties...............................................................15
Section 11.05.    Determination of Losses.......................................................................16
Section 11.06.    Effect of Indemnification Provisions..........................................................16
Section 11.07.    Negligence, Etc...............................................................................16
Section 11.08.    Concurrent Liability..........................................................................16

                                   ARTICLE XII

                                   TERMINATION

Section 12.01.    Termination of Agreement......................................................................17
Section 12.02.    Effect of Termination.........................................................................17
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                                  ARTICLE XIII

                             POST-CLOSING COVENANTS

Section 13.01.    Seller's Obligations..........................................................................17
Section 13.02.    Purchaser's Obligations.......................................................................18

                                   ARTICLE XIV

                                EFFECT OF CLOSING

Section 14.01.    Post-Closing Adjustments......................................................................19

                                   ARTICLE XV

                            CONFIDENTIALITY AGREEMENT

Section 15.01.    Confidentiality...............................................................................21

                                   ARTICLE XVI

                         CASUALTY LOSS AND CONDEMNATION

Section 16.01.    Casualty Loss.................................................................................22

                                  ARTICLE XVII

                                  MISCELLANEOUS

Section 17.01.    Trial Waivers.................................................................................22
Section 17.02.    Binding Arbitration...........................................................................23
Section 17.03.    Press Releases and Public Announcements.......................................................24
Section 17.04.    Entire Agreement; Amendment...................................................................24
Section 17.05.    Successors and Assigns........................................................................24
Section 17.06.    Facsimile; Counterparts.......................................................................24
Section 17.07.    Headings......................................................................................25
Section 17.08.    Governing Law.................................................................................25
Section 17.09.    Legal Fees and Costs..........................................................................25
Section 17.10.    Schedules, Exhibits and Other Instruments.....................................................25
Section 17.11.    Waiver........................................................................................25
Section 17.12.    Resignation as Operator.......................................................................25
Section 17.13.    Notices.......................................................................................26
Section 17.14.    Severability..................................................................................26
Section 17.15.    No Third-Party Beneficiaries..................................................................27
Section 17.16.    Construction..................................................................................27
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                           PURCHASE AND SALE AGREEMENT

         THIS PURCHASE AND SALE AGREEMENT (the "Agreement") is made and entered
into the 22nd day of February, 2000, by and between NEBRASKA PUBLIC GAS AGENCY,
a body politic and corporate under the laws of the State of Nebraska ("Seller"),
and HUMPHREY-HILL, L.P. a Texas limited partnership ("Purchaser"). Seller and
Purchaser are sometimes hereinafter referred to individually as a "Party" and
collectively as "Parties." Capitalized terms used in this Agreement have the
respective meanings ascribed to them or referenced in EXHIBIT A attached hereto.

                                    RECITALS

         A. Seller owns interests in certain oil and gas leases covering certain
lands in Pecos County, Texas and in wells and related leasehold equipment
located on the leases.

         B. Purchaser intends and desires to purchase from Seller, and Seller
intends and desires to sell to Purchaser, all of Seller's right, title and
interest in Pecos County, Texas, pursuant to the terms and conditions set forth
herein.

         NOW THEREFORE, in consideration of the mutual promises, covenants,
representations and warranties contained in this Agreement, the Parties agree as
follows:

                                   ARTICLE I

                           PURCHASE AND SALE OF ASSETS

         SECTION 1.01. PURCHASED ASSETS. At Closing, in reliance upon the
representations, warranties and agreements, and subject to the conditions set
forth in this Agreement, Seller shall sell, assign, transfer, convey and deliver
to Purchaser, and Purchaser shall purchase from Seller for the consideration set
forth in ARTICLE II hereof, all of Seller's right, title and interest in the
hereinafter described properties and interests in Pecos County, Texas, as such
right, title and interest existed on the Effective Date, excluding the Excluded
Assets (as defined in SECTION 1.03 below), but including the following assets
(all such assets, rights, title and interests being conveyed to Purchaser hereby
are collectively called the "Purchased Assets"):

                  (a) LEASES. Seller's interests in any and all oil and gas
         leases covering lands lying within the boundaries of the units
         described on EXHIBIT B attached hereto ("Lands") whether such leases
         are described on EXHIBIT B together with all mineral, royalty,
         overriding royalty or other interests in the oil gas and other minerals
         in the Lands (collectively, the "Leases");

                  (b) WELLS. Seller's interests in the wells located on the
         Lands, as set forth on EXHIBIT C attached hereto (collectively, the
         "Wells");

                  (c) EQUIPMENT. Seller's interests in the Equipment located on
         the Lands as set forth on EXHIBIT D attached hereto (collectively, the
         "Equipment");

<PAGE>   5

                  (d) UNITS. Seller's interest in the Units covering the Lands
         and subject to the Leases;

                  (e) LICENSES AND PERMITS. Seller's interest in all licenses
         and permits which relate to the Leases, Wells, Lands, Equipment and
         Units (collectively, the "Licenses");

                  (f) CONTRACTS. Seller's interest in contracts and other
         instruments (other than bonds posted by Seller) which concern and
         relate to any of the Leases, Wells, Lands, Units and/or Equipment or
         the operation thereof, INSOFAR AND ONLY INSOFAR as the same concern or
         relate to the Purchased Assets, including without limitation, oil, gas
         and condensate purchase and sale contracts; permits; rights-of-way;
         easements; servitudes; estates; surface leases; farmin and farmout
         agreements; division orders and transfer orders; bottom hole
         agreements; dry hole agreements; area-of mutual interest agreements;
         salt water disposal agreements; geologic and geophysical agreements;
         acreage contribution agreements; operating agreements; balancing
         agreements and unit agreements; pooling agreements; pooling orders;
         communitization agreements; processing, gathering, compression and
         transportation agreements; facilities or equipment leases relating
         thereto or used or held for use in connection with the ownership or
         operation thereof or with the production, treatment, sale or disposal
         of Hydrocarbons; and all other contracts and agreements related to the
         Purchased Assets, including but not limited to the contracts described
         on EXHIBIT E attached hereto (collectively, the "Contracts");

                  (g) RECORDS. Seller's Records and, to the extent transferable,
         all other contract rights, intangible rights (excluding Seller's
         trademarks and service marks), inchoate rights, choses in action,
         rights under warranties made by prior owners, manufacturers, vendors or
         other third parties, and rights accruing under applicable statutes of
         limitation or prescription, attributable to the Purchased Assets; and

                  (h) PAYMENTS. Seller's interest in all payments, and all
         rights to receive payments (including without limitation, all
         royalties, overriding royalties and production payments), with respect
         to the ownership of the production of Hydrocarbons from, or the conduct
         of operations with respect to, the Purchased Assets and the interests
         to be conveyed to Purchaser hereunder, accruing after the Effective
         Date.

         SECTION 1.02. EFFECTIVE DATE. The effective date of the transfer of the
Purchased Assets (the "Effective Date") and the production and costs
attributable thereto shall be January 1, 2000 at 7:00 a.m. Central Standard
Time. All payments for production sold prior to the Effective Date shall belong
to and shall be paid to Seller, and all payments for production sold on and
after the Effective Date shall belong to and shall be paid to Purchaser.

         SECTION 1.03. EXCLUDED ASSETS. Except as specifically set forth in
SECTION 1.01, the following assets, real, personal and mixed, tangible and
intangible, owned by Seller or its Affiliates, whether or not associated with or
employed in the operations of the Purchased Assets, (collectively "Excluded
Assets") are not intended by the Parties to be a part of the sale and purchase
contemplated hereunder and are, excepted, reserved and excluded from the
Purchased Assets:

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<PAGE>   6

                  (a) All cash, deposits, checks, funds, accounts receivable,
         notes receivable, or similar items attributable to the Purchased Assets
         with respect to any period of time prior to the Effective Date, except
         for those funds in suspense accounts to be delivered to Purchaser
         pursuant to SECTION 13.01(b) of this Agreement;

                  (b) All Hydrocarbon production from or attributable to the
         Purchased Assets with respect to all periods prior to the Effective
         Date and all proceeds attributable thereto, and all Hydrocarbons that,
         at the Effective Date, are owned by Seller and are in storage or
         otherwise held in inventory and all proceeds attributable thereto; and

                  (c) Purchased Assets retained by Seller because of the failure
         to obtain, comply with or otherwise satisfy a Transfer Requirement.

         SECTION 1.04. PERMITTED ENCUMBRANCES. Seller shall transfer, convey and
assign the Purchased Assets to Purchaser free and clear of any and all liens and
encumbrances, except the following (collectively, "Permitted Encumbrances"):

                  (a) liens for taxes not yet due or, if due, being challenged
         in good faith by appropriate proceedings;

                  (b) materialmen's, mechanic's and other similar liens or
         charges arising in the ordinary course of business for obligations that
         are not delinquent and that will be paid or discharged in the ordinary
         course of business or, if delinquent, that are being contested in good
         faith in the ordinary course of business;

                  (c) easements, rights-of-way, servitudes, permits, surface
         leases, and other rights granted to or reserved for third parties in
         respect of surface operations that do not materially interfere with
         operations of the portion of the Purchased Assets burdened thereby;

                  (d) rights reserved to or vested in any governmental authority
         to control or regulate any of the Leases, Wells or Units and all
         applicable laws, rules, regulations and orders of such authorities;

                  (e) any Title Defects that Purchaser may have expressly waived
         in writing or which are deemed to have been waived under this
         Agreement;

                  (f) liens arising under operating agreements, unitization and
         pooling agreements, orders and statutes and production sales contracts
         securing amounts not yet due or, if due, being contested in good faith
         in the ordinary course of business;

                  (g) the terms and conditions of the Leases and the Contracts;

                  (h) royalties, overriding royalties, net profits interests,
         production payments, reversionary interests, and similar interests;

                  (i) conventional rights of reassignment requiring notice to
         the holders of the rights prior to surrendering or releasing a
         leasehold interest;

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<PAGE>   7

                  (j) calls on production exercisable only at prices
         substantially equivalent to then current fair market value; and

                  (k) all rights to consent by, required notices to, filings
         with or other actions by governmental entities in connection with the
         conveyance of oil and gas leases or interests therein, if they are
         customarily obtained subsequent to the conveyance.

                                   ARTICLE II

                                 PURCHASE PRICE

         SECTION 2.01. CONSIDERATION. The aggregate consideration to be paid by
Purchaser to Seller for the Purchased Assets shall be Ten Million Two Hundred
Thousand Dollars ($10,200,000.00) ("Purchase Price"). Seller acknowledges
receipt of One Hundred Thousand Dollars ($100,000.00) ("Down Payment") from
Purchaser which is non-refundable, except as expressly provided in Sections
8.02, 9.02 12.01, 14.01(f) and 16.01, and shall be applied to the Purchase Price
at Closing.

         SECTION 2.02. PRELIMINARY SETTLEMENT STATEMENT. No later than three (3)
days before Closing, Seller will deliver to Purchaser a closing settlement
statement (the "Preliminary Settlement Statement") setting forth the Purchase
Price as adjusted under this Agreement by the Down Payment and by revenue
received, operating and maintenance expenses, ad valorem taxes, severance taxes,
federal excise and energy taxes, crude oil inventories, state and local sales
and use taxes, and other adjustments set forth in this Agreement, to the extent
this information is available at Closing (the Purchase Price as adjusted shall
be referred to herein as the "Closing Amount"). Seller will use the ad valorem
tax liability for the previous year if the liability for the current year is not
yet available and determine the oil inventory value at the Effective Date. The
Parties shall undertake to agree with respect to the adjustments to the Purchase
Price which are set forth on the Preliminary Settlement Statement prior to the
Closing.

                                  ARTICLE III

                                     CLOSING

         SECTION 3.01. THE CLOSING. The closing of the transactions contemplated
by this Agreement (the "Closing") shall take place on March 24, 2000 (or if the
conditions to the Closing shall not have been satisfied or waived by such date,
then as soon as practicable thereafter, but in no event later than April 30,
2000) (the "Closing Date"), at the offices of Kutak Rock, 717 Seventeenth
Street, Suite 2900, Denver, Colorado 80202-3329 or at such other time or place
as the Parties hereto shall agree in writing.

         SECTION 3.02. SELLER'S CLOSING DELIVERIES. Subject to the conditions
set forth in this Agreement, at the Closing, simultaneous with Purchaser's
deliveries hereunder, Seller shall deliver or cause to be delivered to Purchaser
the Conveyance Documents in the form set forth on EXHIBIT F and all other
documents, certificates and instruments set forth on EXHIBIT G, all in form and
substance reasonably satisfactory to Purchaser and Purchaser's counsel.

                                       4
<PAGE>   8

         SECTION 3.03. PURCHASER'S CLOSING DELIVERIES. Subject to the conditions
set forth in this Agreement, at the Closing, simultaneous with Seller's
deliveries hereunder, Purchaser shall deliver or cause to be delivered to Seller
all of the documents, certificates and instruments set forth on EXHIBIT H, all
in form and substance reasonably satisfactory to Seller and Seller's counsel.

         SECTION 3.04. PAYMENT AT CLOSING. Purchaser shall deliver the Closing
Amount by direct bank or wire transfer to NBC Bank Lincoln, 1248 "O" Street,
Lincoln, NE 68501-2409; ABA Routing Number 104000045 for credit to NPGA Revenue
Account No. 00637557 Attn: Leslie Gibbens and Roger Mock.

                                   ARTICLE IV

                         REPRESENTATIONS AND WARRANTIES

         SECTION 4.01. REPRESENTATIONS AND WARRANTIES OF PURCHASER. Purchaser
represents and warrants to Seller, as of the date of this Agreement and as of
the Closing Date, as follows:

                  (a) ORGANIZATION OF PURCHASER. Purchaser is a Texas limited
         partnership, duly organized, validly existing and in good standing
         under the laws of the State of Texas.

                  (b) AUTHORIZATION OF TRANSACTION. Purchaser has all requisite
         corporate power and authority to enter into this Agreement and perform
         its obligations hereunder. This Agreement has been duly executed and
         delivered by Purchaser and constitutes a legal, valid and binding
         obligation of it, enforceable against it in accordance with its terms
         and conditions except as such enforceability may be limited by or
         subject to (i) any bankruptcy, insolvency, reorganization, moratorium
         or other similar laws relating to creditors' rights generally and (ii)
         general principles of equity (regardless of whether such enforceability
         is considered in a proceeding in equity or at law). Except for (A)
         consents of, or filings with, the United States Department of Interior
         or other governmental agency or the applicable state or Indian agencies
         or authorities in connection with the assignment of any federal, state,
         or Indian leases or any interest therein, and (B) other Transfer
         Requirements which are applicable to the transactions contemplated by
         this Agreement, Purchaser need not give any notice to, make any filing
         with, or obtain any authorization, consent or approval of, any
         government or governmental agency or any other person or entity in
         order to consummate the transactions contemplated by this Agreement.

                  (c) NONCONTRAVENTON. There are no judicial or administrative
         actions or proceedings pending or, to the best of Purchaser's
         Knowledge, threatened that question the validity of this Agreement or
         any action taken or to be taken by Purchaser in connection with this
         Agreement or that, if adversely determined, would be a Material Adverse
         Event with respect to Purchaser's ability to perform its obligations
         under this Agreement.

                  (d) RELIANCE BY PURCHASER. Purchaser acknowledges that in
         entering into this Agreement, it has relied solely upon the express
         representations, warranties and

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         covenants in this Agreement and its independent investigation of, and
         judgment with respect to, the aggregate value of the Purchased Assets,
         and in this regard Purchaser has retained and is relying solely on the
         advice of its own legal, tax, economic, engineering, geological and
         geophysical advisors. Purchaser hereby acknowledges and affirms that it
         has made its own independent investigation, analysis and evaluation of
         the Purchased Assets (including its own estimate and appraisal of the
         extent and value of the oil and gas reserves represented by the
         Purchased Assets).

                  (e) FINANCIAL ABILITY. Purchaser has, and will have upon the
         Closing Date and thereafter sufficient cash, available lines of credit
         or other sources of immediately available good funds to enable it to
         make payment when due of any amounts to be paid by it hereunder and to
         operate the Purchased Assets and comply with its obligations with
         respect to the Purchased Assets after the Closing.

                  (f) BROKER'S FEES. Purchaser has incurred no liability,
         contingent or otherwise, for brokers' or finders' fees with respect to
         the transactions contemplated by this Agreement for which Seller shall
         have any responsibility whatsoever.

                  (g) TEXAS DECEPTIVE TRADE PRACTICES ACT WAIVER. Purchaser (i)
          represents and warrants to Seller that it (A) is acquiring the
          Purchased Assets for commercial or business use, and (B) has knowledge
          and experience in financial and business matters such that enable it
          to evaluate the merits and risks of the transactions contemplated by
          this Agreement and is not in a significantly disparate bargaining
          position with respect to Seller; and (ii) hereby unconditionally and
          irrevocably waives any and all rights or remedies it may have under
          the Deceptive Trade Practices - Consumer Protection Act of the State
          of Texas, Tex. Bus. & Com. Code Section 17.41, et seq., other than
          any of the provisions of Section 17.555 of such Act, if such Act would
          for any reason be deemed applicable to the transactions contemplated
          hereby.

         SECTION 4.02. REPRESENTATIONS AND WARRANTIES OF SELLER. Seller
represents and warrants to Purchaser that:

                  (a) ORGANIZATION OF SELLER. Seller is a body politic and
         corporate, duly organized, validly existing and in good standing under
         the laws of the State of Nebraska.

                  (b) AUTHORIZATION OF TRANSACTION. Seller has all requisite
         corporate power and authority to enter in to this Agreement and perform
         its obligations hereunder. This Agreement has been duly authorized,
         executed and delivered by Seller and constitutes a legal, valid and
         binding obligation of Seller, enforceable against Seller in accordance
         with its terms, except as such enforceability may be limited by or
         subject to (i) any bankruptcy, insolvency, reorganization, moratorium
         or other similar laws relating to creditors' rights generally and (ii)
         general principles of equity (regardless of whether such enforceability
         is considered in a proceeding in equity or at law). Except for (A)
         consents of, or filings with, the United States Department of Interior
         or other governmental agency or the applicable state or Indian agencies
         or authorities in connection with the assignment of any federal, state,
         or Indian leases or any interest therein, and (B) other Transfer
         Requirements which are applicable to the transactions contemplated by
         this Agreement,

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         Seller need not give any notice to, make any filing with, or obtain any
         authorization, consent or approval of, any government or governmental
         agency or any other person or entity in order to consummate the
         transactions contemplated by this Agreement.

                  (c) NONCONTRAVENTON. There are no judicial or administrative
         actions, proceedings pending or, to the best of Seller's Knowledge,
         threatened that question the validity of this Agreement or any action
         taken or to be taken by Seller in connection with this Agreement or
         that, if adversely determined, would be a Material Adverse Event with
         respect to Seller's ability to perform its obligations under this
         Agreement.

                  (d) BROKER'S FEES. Seller has incurred no liability,
         contingent or otherwise, for broker's or finder's fees with respect to
         the transactions contemplated by this Agreement for which Purchaser
         shall have any responsibility whatsoever.

                  (e) LITIGATION AND CLAIMS. Except as shown on SCHEDULE
         4.02(e), since the Effective Date there have not been any, and as of
         the date of this Agreement, there are no lawsuits, orders, decrees,
         injunctions or administrative, arbitration or other proceedings,
         pending or, to the Knowledge of Seller, threatened against Seller
         related to the Purchased Assets ("Litigation and Claims").

                  (f) ENCUMBRANCES. Except as shown on SCHEDULE 4.02(f), Seller
         has not mortgaged, assigned, sold, or otherwise conveyed or encumbered
         title to the Purchased Assets; and will not do so prior to Closing
         except as permitted by the terms of this Agreement and Seller is not
         contesting any liens or charges referred to in SECTION 1.04(b) OR (f).

                  (g) TAXES. Seller has paid or caused to be paid all federal,
         state, and local taxes, rates and like assessments for periods prior to
         the Closing Date that have become due and payable which, if not so
         paid, could result in a lien or encumbrance upon the Purchased Assets,
         including excise, property, ad valorem, franchise, severance and
         production taxes; but not including (i) taxes, rates and like
         assessments which are being contested in good faith, as shown on
         SCHEDULE 4.02(g), (ii) taxes not yet due and payable and (iii) taxes
         which are the responsibility of Purchaser.

                  (h) NO VIOLATIONS. Except as listed on SCHEDULE 4.02(h), to
         Seller's knowledge, Seller has not violated or received notice of
         probable violation of any state or federal laws, regulations, rules or
         orders promulgated by any federal, state or local regulatory agency or
         governmental authority which, if adversely decided, would be a Material
         Adverse Event with respect to the Purchased Asset or the revenues
         attributable thereto;

                  (i) TAKE-OR-PAY. Seller has not made and will not make from
         the date hereof to the Closing Date, any agreement relating to the
         Purchased Assets which would require Purchaser, following Closing, to
         (i) deliver gas paid for, but not taken from production, prior to
         Closing, or (ii) make a cash payment to a buyer of gas for
         reimbursement or recoupment of prior take-or-pay payments which cannot
         be accomplished through such buyer taking gas production.

                                       7
<PAGE>   11

                  (j) ROYALTIES. Except as listed on SCHEDULE 4.02(j), to
         Seller's Knowledge, all rentals, royalties, overriding royalties and
         other payments in or measured by production to be paid by Seller with
         respect to the Purchased Assets have been timely, properly and fully
         paid, except for those funds held in or allocated to suspense accounts
         in the ordinary course of business which will be remitted to Purchaser
         pursuant to SECTION 13.01(b) hereof.

                  (k) PERMITS AND LICENSES. Except as listed on SCHEDULE
         4.02(k), to the Knowledge of Seller, Seller has obtained and currently
         holds all permits, licenses, approvals and authorizations which are
         required under federal, state or local law, rules and regulations in
         order to own and operate the Purchased Assets and, except for those
         items referred to in SCHEDULE 4.02(k), no such permit, license,
         approval or authorization restricts Seller from selling or otherwise
         transferring to Purchaser Seller's interest in the Purchased Assets.

                  (l) GOVERNMENTAL AUDITS. Except as listed on SCHEDULE 4.02(l),
         there are no pending or, to the Knowledge of Seller, threatened, audits
         related to Seller's activities with respect to the Purchased Assets by
         any local, state or federal department or agency.

                  (m) GAS BALANCES. To the best of Seller's Knowledge, SCHEDULE
         4.02(m) lists the status of the gas balances with respect to the
         Purchased Assets as of the Effective Date.

                  (n) ENVIRONMENTAL MATTERS. Except as listed on SCHEDULE
         4.02(n), to the best of Seller's knowledge without inquiry, there exist
         no Environmental Matters with respect to the Purchased Assets.

         SECTION 4.03. DISCLAIMER.

                  (a) Seller makes no warranty, and hereby disclaims any
         warranty, as to the amount, value, quality, or deliverability of
         petroleum, natural gas, or other reserves attributable to the Purchased
         Assets or any portions thereof, or any geological, engineering, or
         other interpretations or economic evaluations of any kind or nature
         whatsoever.

                  (b) Many of the leasehold estates being sold and purchased
         hereunder are in existence only by reason of production. While Seller
         believes said production to be in paying quantities, it makes no
         representation to that effect. Purchaser must make its own
         determination as to whether the Leases are currently in force and
         effect in accordance with their respective provisions.

                  (c) EXCEPT FOR THE WARRANTY PROVIDED IN SECTION 4.02(F) OF
         THIS AGREEMENT, THE PURCHASED ASSETS SHALL BE ASSIGNED AND CONVEYED BY
         SELLER TO PURCHASER WITHOUT ANY WARRANTY OF TITLE, EITHER EXPRESS OR
         IMPLIED, AND WHETHER BY COMMON LAW, STATUTE OR OTHERWISE, EXCEPT THAT
         SELLER WARRANTS ITS TITLE TO THE PURCHASED ASSETS AGAINST PERSONS OR
         PARTIES CLAIMING TITLE BY, THROUGH OR UNDER SELLER.

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                  (d) EXCEPT AS EXPRESSLY SET FORTH IN THIS AGREEMENT, ALL
         TANGIBLE PERSONAL PROPERTY, EQUIPMENT, FIXTURES, AND APPURTENANCES
         CONSTITUTING A PORTION OF THE PURCHASED ASSETS ARE SOLD BY SELLER TO
         PURCHASER "AS IS" AND "WHERE IS." WITHOUT LIMITATION OF THE GENERALITY
         OF THE IMMEDIATE PRECEDING SENTENCE, SELLER EXPRESSLY DISCLAIMS AND
         NEGATES AS TO TANGIBLE PERSONAL PROPERTY, IMPROVEMENTS, AND FIXTURES,
         ANY REPRESENTATION OR WARRANTY, WHETHER EXPRESS OR IMPLIED, AND WHETHER
         BY COMMON LAW, STATUTE OR OTHERWISE, AS TO THE MERCHANTABILITY, FITNESS
         FOR ANY PARTICULAR PURPOSE, CONFORMITY TO MODELS OR SAMPLES OF
         MATERIALS, AND/OR CONDITION THEREOF.

                  (e) SELLER MAKES NO WARRANTY OR REPRESENTATION, EXPRESS OR
         IMPLIED, WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF ANY
         INFORMATION, RECORDS OR DATA NOW, HERETOFORE, OR HEREAFTER MADE
         AVAILABLE TO PURCHASER IN CONNECTION WITH THE AGREEMENT, INCLUDING
         WITHOUT LIMITATION ANY DESCRIPTION OF THE PURCHASED ASSETS, PRICING
         ASSUMPTIONS, POTENTIAL FOR PRODUCTION OF HYDROCARBONS FROM THE
         PURCHASED ASSETS, OR ANY OTHER MATTERS CONTAINED IN ANY MATERIAL
         FURNISHED BY SELLER TO PURCHASER OR ITS OFFICERS, DIRECTORS, EMPLOYEES,
         AGENTS, ADVISORS OR REPRESENTATIVES.

                  (f) The Parties agree that the disclaimers of warranty are
         "conspicuous" disclaimers for purposes of any applicable law, rule or
         order.

                                   ARTICLE V

                      OPERATIONS PRIOR TO THE CLOSING DATE

         SECTION 5.01. OPERATION OF PROPERTIES PENDING THE CLOSING DATE.

                  (a) Prior to the Closing Date, Seller agrees, unless
         specifically waived by Purchaser in writing, to:

                           (i) maintain and operate the Purchased Assets, to the
                  extent Seller is an operator, or to use reasonable efforts to
                  cause the Purchased Assets to be maintained and operated by
                  the operator thereof, in a good and workmanlike manner and in
                  substantially the same manner as Seller has heretofore
                  operated the same, to the extent Seller is an operator;

                           (ii) notify Purchaser of any notice or threatened
                  notice of which Seller becomes aware relating to any default;

                                       9
<PAGE>   13

                           (iii) timely pay all costs and expenses incurred by
                  it in connection with the Purchased Assets subject to
                  repayment by Purchaser for all such costs and expenses
                  incurred by Seller after the Effective Date as set forth in
                  SECTION 7.02 and 14.01; and

                           (iv) not encumber, sell or otherwise dispose of any
                  of the Purchased Assets.

                  (b) Any Authorization for Expenditure ("AFE") circulated to
         Seller after the date of this Agreement will be transmitted to
         Purchaser. Seller and Purchaser shall thereafter determine, within the
         time required by the AFE, whether to consent or go non-consent to the
         AFE. If Seller determines to go non-consent but Purchaser determines to
         consent to any such AFE then Purchaser will assume all responsibility
         with respect to such AFE, including payments required thereunder,
         regardless of whether or not Purchaser consummates the transaction
         contemplated by this Agreement. Purchaser shall acquire no right to
         receive any interest or refund for amounts paid by it if the
         transaction is not consummated for any reason. However, Purchaser shall
         be responsible to Seller for any interest forfeited or penalty charged
         due to Purchaser's decision concerning an AFE.

                  (c) Seller will grant no waiver or consents with respect to
         any rule or regulation of the Railroad Commission of Texas.

                                   ARTICLE VI

              ACCESS TO PURCHASED ASSETS PRIOR TO THE CLOSING DATE

         SECTION 6.01. RECORDS AND PERSONNEL. Following the execution hereof,
Seller shall afford Purchaser and its duly authorized representatives access at
all reasonable times during normal business hours to all books, records,
documents and other information concerning the Purchased Assets or relating to
Seller's interest therein.

                                  ARTICLE VII

                            ASSUMPTION AND INDEMNITY

         SECTION 7.01. SELLER'S OBLIGATIONS AND LIABILITIES. Seller agrees to
pay, perform, fulfill and discharge all legitimate claims, obligations, taxes,
costs and expenses relating to Seller's ownership or operation of the Purchased
Assets arising prior to the Effective Date, and agrees to indemnify, defend and
hold Purchaser harmless from and against any and all Losses, claims, cause of
action or judgment of any kind or character with respect to all liabilities and
obligations arising out of the ownership or operation of the Purchased Assets
that are asserted prior to the Effective Date.

         SECTION 7.02. PURCHASER'S OBLIGATIONS AND LIABILITIES. From and after
the Effective Date, Purchaser shall assume all expenses and responsibility for
compliance with the terms of the Leases (including payment of all rentals,
minimum royalties or shut-in royalty payments), Wells, Equipment, Units,
Licenses, Contracts and any other agreements affecting the Purchased Assets and
Purchaser also shall assume all responsibility for compliance with regulatory
requirements

                                       10
<PAGE>   14

affecting the Purchased Assets, including Environmental Liabilities,
Environmental Matters and the obligation to properly plug and abandon the Wells
and perform all reclamation requirements (collectively, "Assumed Liabilities").
Purchaser shall provide proof of compliance with local, state and federal
bonding requirements at Closing and shall execute all forms required by any
governmental authority to transfer operations and responsibility to Purchaser.

         Purchaser agrees to pay, perform, fulfill and discharge all Losses,
claims and obligations relating to the ownership or operation of the Purchased
Assets arising from and after the Effective Date, and agrees to indemnify,
defend and hold Seller harmless from and against any and all claims, Losses,
cause of action or judgment of any kind or character with respect to all
liabilities and obligations arising out of the ownership or operation of the
Purchased Assets asserted on and after the Effective Date, including without
limitation, the Assumed Liabilities and Seller assigns and Purchaser shall be
subrogated to any and all claims, rights, causes of action, and warranties
against or by any other person or persons, arising out of, in connection with or
due under the Leases, Contracts and any other related agreement in existence on
the Effective Date.

                                  ARTICLE VIII

                                  TITLE MATTERS

         SECTION 8.01. WARRANTY OF TITLE. At the Closing, Seller shall convey to
Purchaser all of the Purchased Assets. Such conveyance shall be subject to the
Permitted Encumbrances and WITHOUT ANY WARRANTY OF TITLE, EITHER EXPRESS OR
IMPLIED, AND WHETHER BY COMMON LAW, STATUTE OR OTHERWISE, except for the
warranty provided in SECTION 4.02(f) of this Agreement and except for the
warranty of title as to persons claiming by, through and under Seller contained
in the Conveyance Documents delivered pursuant to SECTION 3.02.

         SECTION 8.02. TITLE DEFECTS. Seller has made available to Purchaser all
title data in Seller's possession and its lease and well files relating to the
Purchased Assets including title opinions, title curative data or any other
title data not now in Purchaser's possession. Purchaser shall be responsible for
satisfying itself as to the status of title to the Purchased Assets, and any
further title examination, investigation or curative efforts that Purchaser may
desire to make shall be at Purchaser's sole cost and expense. Purchaser shall
promptly notify Seller in writing of any Title Defect, but no later than seven
(7) days prior to the Closing Date ("Title Defect Notice"). Seller shall have
the right, but not the obligation, to attempt to cure any such Title Defect
prior to the Closing Date, and if requested to do so, Purchaser will cooperate
with Seller in such regard. Any such Title Defects which are not objected to in
writing by Purchaser as aforesaid or if objected to by Purchaser and are not
cured by Seller on or before the Closing Date, shall be deemed conclusively to
be Permitted Encumbrances. In Purchaser's discretion, however, and upon written
notice to Seller on or before the Closing Date, Purchaser can choose not to
close based upon its Title Defect Notice and this Agreement shall terminate AB
INITIO and Purchaser shall, in such case, be entitled to return of the Down
Payment.

                                       11
<PAGE>   15

                                   ARTICLE IX

                                  ENVIRONMENTAL

         SECTION 9.01. AVAILABILITY OF DATA TO PURCHASER; PHASE I ENVIRONMENTAL
AUDIT. Seller has made available to Purchaser information which is in the
possession or control of Seller or to which Seller has access (other than
publicly available information to which Purchaser has equal access) and which
relates to the environmental condition of the Purchased Assets, which
information includes, but shall not be limited to, information regarding crude
oil and produced water that may have been spilled or disposed of on-site and the
locations thereof, on-site pits and pit closures; on-site burial; land farming;
land spreading; underground injection; and on-site solid waste disposal sites.
Purchaser also shall have the right, prior to the Closing Date, at its own risk
and expense, to conduct or have conducted a Phase I Environmental Audit of the
Purchased Assets. To enable Purchaser to conduct the Phase I Environmental
Audit, Seller will provide Purchaser (and its representatives) with reasonable
access to the Purchased Assets, subject to any third party restrictions on
Seller with respect to access to the Purchased Assets, to Seller's books,
records, and files relating to the Purchased Assets, and to current employees of
Seller. If Purchaser determines to conduct a Phase I Environmental Audit,
Purchaser shall treat, and will cause all of its representatives, agents,
consultants, contractors, or subcontractors to treat, all information obtained
by Purchaser pursuant to the Phase I Environmental Audit as strictly
confidential (except to the extent such information is otherwise available to
the general public) and will not disclose the results without the prior written
consent of Seller, except to the extent that such results are legally required
to be disclosed by Purchaser (in which case, Purchaser shall provide Seller with
reasonable notice prior to making such disclosure). Seller shall have the right
to have a representative present during any inspection of the Purchased Assets
and during any interviews of Seller's employees, conducted as a part of the
Phase I Environmental Audit, and Purchaser shall coordinate these activities
with Seller so as to allow Seller to have a representative present if it so
desires. Purchaser shall provide Seller with copies of any Phase I Environmental
Audit report not more than five (5) days after Purchaser's receipt of same.
Purchaser agrees to release, indemnify, defend, and hold Seller harmless from
any fines, penalties or damage to persons or property caused by the activities
of Purchaser or its representatives, agents, consultants, contractors or
subcontractors in conducting a Phase I Environmental Audit.

         SECTION 9.02. ENVIRONMENTAL DEFECTS. If Purchaser has Knowledge of the
existence of an Environmental Matter discovered in the course of the Phase I
Environmental Audit or Purchaser's other environmental due diligence in
connection with this transaction, then Purchaser shall advise Seller in writing
of such Environmental Matter on or before seven (7) days prior to the Closing
Date. Such written notification shall contain a reasonable description of the
facts used by Purchaser in making its determination that a breach exists.
Purchaser agrees that such written notification to Seller shall be sent to
Seller by telecopy or personal delivery as well as by registered or certified
mail, return receipt requested and postage prepaid. Prior to Closing, Purchaser
and its employees, contractors and consultants shall treat all information
regarding any Environmental Matter as confidential and shall not disclose such
information to any governmental authority or other third party without Seller's
written consent, unless disclosure is required by applicable law (in which case,
Purchaser shall provide Seller with reasonable notice prior to making such
disclosure). Within three (3) days after Seller's receipt of

                                       12
<PAGE>   16

a notice with respect to each Environmental Matter, Seller in its discretion may
have the Purchased Asset affected thereby removed from the Purchased Assets and
Purchaser and Seller shall agree to adjust the Purchase Price by the value of
such Purchased Asset, or Seller may terminate this Agreement, in which event
this Agreement will be terminated and rendered void AB INITIO and Purchaser
shall in such case be entitled to the return of the Down Payment. However,
Purchaser shall have the right to waive all Environmental Matters by notifying
Seller in writing, within three (3) days after receipt of notice from Seller
relating to Environmental Matters, as set forth herein, that it unequivocally
waives all Environmental Matters and will close on the Closing Date. Also, in
Purchaser's discretion, however, and upon written notice to Seller and on or
before the Closing Date, Purchaser can choose not to close based upon its notice
of an Environmental Matter and this Agreement shall terminate AB INITIO and
Purchaser shall in such case be entitled to return of the Down Payment.
Notwithstanding anything provided in this Agreement to the contrary, the failure
of Purchaser to notify Seller in writing of any Environmental Matter as provided
herein shall be conclusively deemed waived by Purchaser.

                                   ARTICLE X

                        CONDITIONS TO OBLIGATION TO CLOSE

         SECTION 10.01. CONDITIONS TO OBLIGATION OF SELLER. The obligation of
Seller to consummate the transactions to be performed by it in connection with
the Closing is subject, at the option of Seller, to satisfaction on or prior to
the Closing Date of the following conditions:

                  (a) the representations and warranties set forth in SECTION
         4.01 above shall be true and correct in all material respects at and as
         of the Closing Date as though made as of such date;

                  (b) Purchaser shall have performed or complied with all of its
         covenants and agreements hereunder in all material respects through
         Closing;

                  (c) there shall not be any injunction, judgment, order,
         decree, ruling or charge in effect preventing consummation of any of
         the transactions contemplated by this Agreement;

                  (d) Purchaser shall have delivered to Seller a certificate to
         the effect that each of the conditions specified above in SECTION
         10.01(a) THROUGH (c) is satisfied;

                  (e) all actions to be taken by Purchaser in connection with
         consummation of the transactions contemplated hereby and all
         certificates, opinions, instruments, and other documents required to
         effect the transactions contemplated hereby will be reasonably
         satisfactory in form and substance to Seller;

                  (f) prior to the Closing Date, Purchaser shall not have given
         Seller Notice pursuant to SECTION 8.02, SECTION 9.02, SECTION 14.01(f)
         or SECTION 16.01 that it has chosen not to Close;

                  (g) as of the Closing Date, there shall not exist any matters
         that cause or result in unresolved Title Defects or Environmental
         Matters; and

                                       13
<PAGE>   17

                  (h) as of the Closing Date, the Parties shall have agreed to
         all of the adjustments to the Purchase Price which are set forth on the
         Preliminary Settlement Statement.

         SECTION 10.02. CONDITIONS TO OBLIGATION OF PURCHASER. The obligation of
Purchaser to consummate the transactions to be performed by it in connection
with the Closing is subject, at the option of Purchaser, to satisfaction on or
prior to the Closing Date of the following conditions:

                  (a) the representations and warranties set forth in SECTION
         4.02 shall be true and correct in all material respects at and as of
         the Closing Date as though made as of such date;

                  (b) Seller shall have performed or complied with all of its
         covenants and agreements hereunder in all material respects through the
         Closing;

                  (c) there shall not be any injunction, judgment, order,
         decree, ruling, or charge in effect preventing consummation of any of
         the transactions contemplated by this Agreement;

                  (d) Seller shall have delivered to Purchaser a certificate to
         the effect that each of the conditions specified above in SECTION
         10.02(a) THROUGH (c) is satisfied;

                  (e) all actions to be taken by Seller in connection with the
         consummation of the transactions contemplated hereby and all
         certificates, opinions, instruments, and other documents required to
         effect the transactions contemplated hereby will be reasonably
         satisfactory in form and substance to Purchaser;

                  (f) prior to the Closing Date, Purchaser shall not have given
         Seller Notice pursuant to SECTION 8.02, SECTION 9.02, SECTION 14.01(f)
         or SECTION 16.01 that it has chosen not to Close;

                  (g) as of the Closing Date, there shall not exist any matters
         that cause or result in unresolved Title Defects or Environmental
         Matters; and

                  (h) as of the Closing Date, the Parties shall have agreed to
         all of the adjustments to the Purchase Price which are set forth on the
         Preliminary Settlement Statement.

                                   ARTICLE XI

             REMEDIES FOR BREACHES OF THIS AGREEMENT OR FOR DEFECTS

         SECTION 11.01. SURVIVAL OF REPRESENTATIONS AND WARRANTIES. The
representations and warranties of Seller contained in SECTION 4.02 and of
Purchaser contained in SECTION 4.01 hereof shall survive the Closing for a
period of ninety (90) days from the Closing Date (the "Survival Period").

                                       14
<PAGE>   18

         SECTION 11.02. INDEMNIFICATION PROVISIONS FOR THE BENEFIT OF PURCHASER.
In the event that Seller breaches any of its representations and warranties in
SECTION 4.02, then Seller agrees to indemnify and hold harmless Purchaser and
its current, former, and future directors, officers, employees and agents, and
each of the successors, heirs and executors of any of the foregoing, from and
against the entirety of any Losses resulting from or attributable to the breach
which Purchaser (or any such other indemnified person in such person's capacity
set forth above) shall suffer, provided such claim for indemnification is
brought in accordance with the terms of this Agreement within the Survival
Period; and further provided that "Losses," as used in this sentence, shall not
include, and Seller shall not be responsible or liable for, any death, personal
injury or consequential damages in respect of such breach.

         SECTION 11.03. INDEMNIFICATION PROVISIONS FOR BENEFIT OF THE SELLER. In
the event that Purchaser breaches any of its representations and warranties
contained in SECTION 4.01 hereof, then Purchaser agrees to indemnify and hold
harmless Seller and its current, former, and future directors, officers,
employees and agents, and each of the successors, assigns, heirs, and executors
of any of the foregoing from and against the entirety of any Losses resulting
from or related or attributable to the breach which Seller (or any such other
indemnified person in such person's capacity set forth above) shall suffer,
provided such claim for indemnification is brought in accordance with the terms
of this Agreement within the Survival Period; and further provided that
"Losses," as used in this sentence, shall not include, and Purchaser shall not
be responsible or liable for, any death, personal injury, or consequential
damages in respect of such breach.

         SECTION 11.04. MATTERS INVOLVING THIRD PARTIES.

                  (a) If any third party shall notify either Party (the
         "Indemnified Party") with respect to any matter which may give rise to
         a claim for indemnification against the other Party (the "Indemnifying
         Party") under this ARTICLE XI or otherwise pursuant to this Agreement,
         then the Indemnified Party shall promptly (and in any event within ten
         (10) business days after receiving service of process in a lawsuit,
         administrative proceeding or arbitration proceeding with respect to the
         Third Party Claim) notify each Indemnifying Party thereof in writing.
         Each of the matters described in this SECTION 11.04(a) shall be
         referred to in this Agreement as a "Third Party Claim."

                  (b) Any Indemnifying Party will have the right to assume and
         thereafter conduct the defense of the Third Party Claim with counsel of
         its choice reasonably satisfactory to the Indemnified Party; provided,
         however, that the Indemnifying Party will not consent to the entry of
         any judgment or enter into any settlement with respect to the Third
         Party Claim without the prior written consent of the Indemnified Party
         (which consent shall not be unreasonably withheld) unless the judgment
         or proposed settlement involves only the payment of money damages and
         does not impose an injunction or other equitable relief upon (or
         constitute an admission of guilt, liability, fault or responsibility
         for) the Indemnified Party. The Indemnified Party shall have the right
         to employ separate counsel in any such action and to participate in the
         defense thereof, but the fees and expenses of such counsel shall be at
         the expense of the Indemnified Party unless (i) the employment thereof
         has been specifically authorized in writing by the Indemnifying Party
         or (ii) the Indemnifying Party failed to assume the defense and employ
         counsel.

                                       15
<PAGE>   19

                  (c) Unless and until an Indemnifying Party assumes the defense
         of the Third Party Claim as provided in SECTION 11.04(b) above, the
         Indemnified Party may defend against the Third Party Claim in any
         manner it deems reasonably appropriate.

                  (d) In no event will the Indemnified Party consent to the
         entry of any judgment or enter into any settlement with respect to the
         Third Party Claim without the prior written consent of the Indemnifying
         Party (which consent shall not be unreasonably withheld), unless the
         Indemnified Party waives indemnification with respect to the Third
         Party Claim so settled and adjudicated.

                  (e) The indemnification obligations of the Seller and
         Purchaser under this Agreement shall include court costs and attorneys'
         fees and expenses and costs of investigating, preparing or defending
         any action or proceeding with respect to any Third Party Claim to the
         extent such Third Party Claim may give rise to a claim for
         indemnification under such indemnification obligations of Seller or
         Purchaser, as the case may be.

         SECTION 11.05. DETERMINATION OF LOSSES. A claim of an alleged breach
will be recoverable only to the extent of Losses actually incurred or paid by
the Indemnified Party. The Parties shall make appropriate adjustments for
insurance recoveries actually received (net of all costs and expenses incurred
in connection with such recoveries) from non-Affiliates in determining Losses
for purposes of this ARTICLE XI or ARTICLE XIII.

         SECTION 11.06. EFFECT OF INDEMNIFICATION PROVISIONS. The Parties
acknowledge and agree that the foregoing indemnification provisions in this
ARTICLE XI and in ARTICLE XIII shall, following the Closing hereof, be the
exclusive remedy of either Party for any breach of the representations and
warranties in ARTICLE IV hereof; provided that the foregoing shall not limit the
Parties' obligations for any breach of a covenant or agreement contained in any
Article other than ARTICLE IV. If a claim for payment of a liquidated amount
covered by a Party's indemnification obligations under this Agreement is made in
accordance with the terms of this Agreement and is not paid within sixty (60)
days after such claim is received by the Party responsible for paying the same,
the liquidated amount of such claim shall bear interest at the Agreed Rate from
the date such claim was received until paid.

         SECTION 11.07. NEGLIGENCE, ETC. IT IS EXPRESSLY AGREED THAT SELLER'S
AND PURCHASER'S RESPECTIVE INDEMNIFICATION OBLIGATIONS UNDER THIS ARTICLE XI,
ARTICLE XIII, OR UNDER ANY OTHER ARTICLE OF THIS AGREEMENT INCLUDE, WITHOUT
LIMITATION, LOSSES AND ENVIRONMENTAL LIABILITIES, IF ANY, BASED ON NEGLIGENCE,
ALLEGED NEGLIGENCE, GROSS NEGLIGENCE OR ALLEGED GROSS NEGLIGENCE OF SELLER OR
PURCHASER, AND THEIR RESPECTIVE AFFILIATES, AND EACH OF THE RESPECTIVE CURRENT
OR FORMER DIRECTORS, OFFICERS, EMPLOYEES, AGENTS, STOCKHOLDERS AND CONTROLLING
PERSONS OF ANY OF THE FOREGOING.

         SECTION 11.08. CONCURRENT LIABILITY. THE INDEMNIFICATION AND ASSUMPTION
PROVISIONS OF SELLER AND PURCHASER CONTAINED IN THIS

                                       16
<PAGE>   20

AGREEMENT SHALL BE APPLICABLE WHETHER OR NOT THE LOSSES IN QUESTION AROSE SOLELY
OR IN PART FROM THE ACTIVE, PASSIVE OR CONCURRENT NEGLIGENCE, STRICT LIABILITY
OR OTHER FAULT OF ANY INDEMNIFIED PARTY. SELLER AND PURCHASER ACKNOWLEDGE THAT
THIS STATEMENT IS CONSPICUOUS.

                                  ARTICLE XII

                                   TERMINATION

         SECTION 12.01. TERMINATION OF AGREEMENT. The Parties may terminate this
Agreement at any time prior to the Closing as provided below:

                  (a) by mutual written consent;

                  (b) by written notice from Purchaser to Seller as provided in
         SECTION 8.02;

                  (c) by written notice from Purchaser to Seller as provided in
         SECTION 9.02;

                  (d) by written notice from Purchaser to Seller as provided in
         SECTION 14.01(f);

                  (e) by written notice from Purchaser to Seller as provided in
         SECTION 16.01; or

                  (f) in the event the Closing shall not occur on or before
         April 30, 2000, either Purchaser or Seller may terminate this Agreement
         by giving written notice thereof to the other Party on or after April
         30, 2000, and prior to Closing. If Closing fails to occur through no
         fault of Purchaser, then Purchaser shall be entitled to the return of
         its Down Payment.

         SECTION 12.02. EFFECT OF TERMINATION. If a Party terminates this
Agreement pursuant to SECTION 12.01 above, such termination shall be the
exclusive remedy for the breach by the other Party of any representations,
warranties or covenants hereunder, and all rights and obligations of the Parties
hereunder shall terminate without any liability or responsibility of a Party to
the other Party; provided, however, that the provisions of SECTION 5.01(b) and
ARTICLE XV shall survive termination.

                                  ARTICLE XIII

                             POST-CLOSING COVENANTS

         The Parties agree as follows with respect to the period following the
Closing:

         SECTION 13.01. SELLER'S OBLIGATIONS.

                  (a) RECORDS. As soon as practicable after Closing, Seller
         shall deliver to Purchaser all Records. Seller shall be entitled to
         retain, or to obtain from Purchaser at Seller's cost, copies of all
         such information for its records as may be reasonably necessary for
         Seller to address matters relative to ownership and operation of the

                                       17
<PAGE>   21

         Purchased Assets, including, without limitation, the preparation of
         accounting and financial information, the filing of tax returns and the
         pursuit or defense of litigation.

                  (b) SUSPENSE FUNDS. As soon as practicable after Closing,
         Seller shall provide Purchaser with a list showing all proceeds from
         production attributable to the Purchased Assets which are currently
         held in suspense, and Seller shall transfer to Purchaser all such
         proceeds. Purchaser shall be responsible for distribution of such
         proceeds to the parties lawfully entitled thereto and Purchaser agrees
         to indemnify, defend and hold harmless Seller from and against any and
         all Losses arising out of or relating to such proceeds.

                  (c) GOVERNMENTAL CONSENTS. At the Closing, Seller shall
         execute and deliver to Purchaser such assignment of federal, state and
         Indian leases as require consent to assignment, on the forms required
         by the governmental or tribal agency having jurisdiction thereof.
         Purchaser shall promptly file for and obtain the necessary approvals
         for such assignments. Until such approvals are obtained, Seller shall
         continue to hold governmental title to such leases as nominee for
         Purchaser.

                  (d) TRANSITION. Seller agrees to provide such information as
         may be reasonably requested by Purchaser's personnel to facilitate the
         orderly transition of accounting responsibilities and to provide
         information sufficient to enable Purchaser to record liquids revenue,
         gas revenue, operating expenses, capital expenditures and such other
         accounting transactions on a detailed property basis or such basis as
         maintained by Seller. In order to permit Purchaser to verify this
         information, Purchaser will have the right to review such reports and
         to conduct an audit of the underlying data for a period of one hundred
         and eighty (180) calendar days after the Effective Date.

         SECTION 13.02. PURCHASER'S OBLIGATIONS.

                  (a) RECORDING. Within thirty (30) days following Closing,
         Purchaser, at its expense, shall record those Conveyance Documents
         necessary to evidence on the public record that Purchaser has acquired
         the Purchased Assets and within a reasonable time thereafter, Purchaser
         shall supply Seller with a true and accurate photocopy of such recorded
         and filed Conveyance Documents. In the event that Purchaser fails to
         record any such Conveyance Documents within such time period, Seller
         may, but shall not be obligated to, record such Conveyance Documents on
         Purchaser's behalf and at Purchaser's cost (for which Purchaser shall
         immediately reimburse Seller upon demand).

                  (b) REMOVAL OF NAMES. As soon as reasonably practicable after
         the Closing, Purchaser shall cause to be removed the names and marks of
         "Nebraska Public Gas Agency," "NPGA" and any variations and derivations
         thereof and logos relating thereto from all of the Purchased Assets,
         and will not thereafter make any use whatsoever of such names, marks,
         and logos. Purchaser shall return to Seller any signs bearing Seller's
         name or logo. Purchaser shall indemnify Seller for any Losses Seller
         suffers as a result of the Purchaser's non-removal of such names or
         marks after the Closing.

                                       18
<PAGE>   22

                  (c) GEOLOGICAL AND GEOPHYSICAL INFORMATION. Seller reserves
         the right to use any and all geologic and geophysical information
         transferred to Purchaser hereunder and Purchaser agrees to cooperate
         with Seller in granting reasonable access to such information.

                  (d) RESPONSIBILITY FOR ASSUMED LIABILITIES. FROM AND AFTER THE
         CLOSING DATE, PURCHASER AGREES TO ASSUME AND TO INDEMNIFY AND HOLD
         HARMLESS SELLER, SELLER'S AFFILIATES, EACH OF THE RESPECTIVE CURRENT,
         FORMER, AND FUTURE DIRECTORS, OFFICERS, EMPLOYEES, AND AGENTS OF ANY OF
         THE FOREGOING, AND EACH OF THE SUCCESSORS, ASSIGNS, HEIRS, AND
         EXECUTORS OF ANY OF THE FOREGOING FROM AND AGAINST THE ENTIRETY OF ANY
         LOSSES RESULTING FROM, ARISING OUT OF, OR ATTRIBUTABLE TO THE ASSUMED
         LIABILITIES, EXCEPT TO THE EXTENT THE SAME ARE COVERED AND PAID BY BY
         SELLER'S INSURANCE.

                                  ARTICLE XIV

                                EFFECT OF CLOSING

         SECTION 14.01. POST-CLOSING ADJUSTMENTS. The following terms,
provisions and prorations shall be effective at the Closing:

                  (a) REVENUES. All proceeds from production, accounts
         receivables, notes receivables, income, revenues, monies and other
         items attributable to the Purchased Assets with respect to any period
         of time prior to the Effective Date shall belong to and be retained by
         or paid over to Seller, and all necessary reports with respect to such
         proceeds shall be filed by Seller. All proceeds from production,
         accounts receivables, notes receivables, income, revenues, monies and
         other items attributable to the Purchased Assets with respect to any
         period of time from and after the Effective Date shall belong to and be
         retained by or paid over to Purchaser, except for Hydrocarbons that, at
         the Effective Date, are attributable to the Purchased Assets and are in
         storage or are otherwise held in inventory and all proceeds
         attributable thereto, which shall belong to and be retained by or paid
         over to Seller.

                  (b) EXPENSES. All accounts payable and accrued liabilities for
         costs and expenses attributable to the Purchased Assets with respect to
         any period of time prior to the Effective Date, including excise,
         severance, and similar taxes based on production or royalties, shall be
         the obligation of and paid by Seller, and all necessary reports with
         respect to such costs and expenses shall be filed by Seller. All
         accounts payable and accrued liabilities for direct costs and expenses
         attributable to the Purchased Assets with respect to any period of time
         from and after the Effective Date shall be the obligation of and be
         paid by the Purchaser, and all necessary reports with respect to such
         costs and expenses shall be filed by Purchaser.

                  (c) AD VALOREM AND PROPERTY TAXES. All ad valorem taxes, real
         property taxes, personal property taxes and similar obligations shall
         be apportioned as of the

                                       19
<PAGE>   23

         Effective Date between Purchaser and Seller. All such taxes allocable
         to period prior to the Effective Date shall be paid by Seller, and all
         such Taxes allocable to the Effective Date and thereafter shall be paid
         by Purchaser. Any refunds of taxes allocable to periods prior to the
         Effective Date shall be the property of Seller. Purchaser shall file or
         cause to be filed all required reports and returns incident to such
         taxes which are due on or after the Effective Date, and shall pay or
         cause to be paid to the taxing authorities all such taxes reflected on
         such reports and returns.

                  (d) SALES TAXES, FILING FEES, ETC. The Purchase Price shall be
         net of any sales taxes or other transfer taxes and Purchaser shall be
         liable for any such tax, as well as any applicable conveyance, transfer
         and recording fees, and real estate transfer stamp or taxes imposed
         upon the sale of the Purchased Assets. If Seller is required by
         applicable state law to report and pay these taxes or fees, Purchaser
         shall promptly deliver a check to Seller in full payment thereof.

                  (e) OTHER TAXES. All production, severance or excise taxes,
         conservation fees and other similar such taxes or fees relating to
         production attributable to the Purchased Assets prior to the Effective
         Date shall be paid by Seller and all such taxes and fees relating to
         such production attributable to the Purchased Assets on and after the
         Effective Date shall be paid by Purchaser.

                  (f) GAS IMBALANCES. To the Knowledge of Seller, the gas
         balances as of the Effective Date are as set forth on SCHEDULE 4.02(n).
         Purchaser shall assume Seller's actual overproduced or underproduced
         position in the Wells as of the Effective Date, including the
         responsibility for the payment of royalties on the volume of gas Seller
         took in excess of its entitlement and any obligation to balance whether
         in cash or in kind. Upon review of SCHEDULE 4.02(n), Purchaser shall
         notify Seller in writing, but not later than seven (7) days prior to
         the Closing Date, if it objects to assuming Seller's actual
         overproduced or underproduced position in the Wells, as of the
         Effective Date. If such notice is delivered timely to Seller, Purchaser
         shall not be required to close and this Agreement shall terminate AB
         INITIO and Purchaser shall be entitled to return of its Down Payment.

                  (g) PAYMENTS; SHARED OBLIGATIONS. If amounts are received by
         either Party hereto which, under the terms of this ARTICLE XIV belong
         to the other Party, such amount shall immediately be paid over to the
         proper Party. If an invoice or other evidence of an obligation is
         received which under the terms of this ARTICLE XIV is partially the
         obligation of Seller and partially the obligation of Purchaser, then
         the Parties shall consult each other and each Party shall promptly pay
         its portion of such obligation to the obligee.

                  (h) POST-CLOSING ADJUSTMENTS. As soon as practicable after
         Closing and, in any event, no later than ninety (90) calendar days
         after Closing, Seller shall prepare and deliver to Purchaser, in
         accordance with this Agreement and generally accepted accounting
         principles, a statement (herein called the "Final Settlement
         Statement"), setting forth each adjustment proration, or payment that
         was not finally determined as of the Closing or in accordance with
         SECTION 14.01(g) above, and showing the calculation of such
         adjustments. The Final Settlement Statement shall be prepared in
         accordance with

                                       20
<PAGE>   24

         customary accounting principles used in the oil and gas industry. As
         soon as practicable after receipt of the Final Settlement Statement,
         Purchaser shall deliver to Seller a written report containing any
         changes that Purchaser proposes be made to the Final Settlement
         Statement. The Parties shall undertake to agree with respect to the
         amounts due pursuant to such post-Closing adjustment no later than one
         hundred and twenty (120) days after the Closing Date. If the parties
         are unable to reach agreement within ten (10) days of such date, the
         provisions of SECTION 14.01(i) relating to the arbitration shall
         control. The date upon which such agreement is reached or upon which
         the Closing Amount is finally established shall herein be called the
         "Final Settlement Date." In the event that the Closing Amount as
         finally established (i) is more than the Purchase Price, Purchaser
         shall pay Seller or to Seller's account (as designated by Seller) in
         immediately available federal funds the amount of such difference; or
         (ii) is less than the Purchase Price, Seller shall pay Purchaser or to
         Purchaser's account (as designated by Purchaser) in immediately
         available federal funds the amount of such difference. Payment by
         Purchaser or Seller shall be made within five (5) days after the Final
         Settlement Date.

                  (i) ARBITRATION OF FINAL SETTLEMENT STATEMENT. If Seller and
         Purchaser cannot agree upon the Final Settlement Statement, the parties
         shall retain the services of a "big six" accounting firm of certified
         public accountants to act as an arbitrator and to decide all points of
         disagreement with respect to the Final Settlement Statement, such
         decision to be binding on both parties. If the Parties are unable to
         agree upon the designation of such accounting firm, then Seller or
         Purchaser, or both of them, may in writing request the Judge of the
         United States District Court for the Northern District of Texas, Dallas
         Division senior in term of service to appoint an accounting firm as
         arbitrator. The arbitration shall be conducted under the Texas General
         Arbitration Act and the rules of the American Arbitration Association
         ("AAA") to the extent such rules do not conflict with the terms of such
         Act and the terms hereof. The costs and expenses of the arbitrator,
         whether the firm designated above, or a third party appointed pursuant
         to this SECTION 14.01(i), shall be shared equally by Seller and
         Purchaser.

                                   ARTICLE XV

                            CONFIDENTIALITY AGREEMENT

         SECTION 15.01. CONFIDENTIALITY. Each Party, its Affiliates and their
respective directors, officers, managers, partners, employees, agents,
representatives, consultants, investors and lenders, agree to keep the terms and
conditions of this Agreement and all proprietary and confidential information
exchanged between Purchaser and Seller in connection with this Agreement,
confidential, and to not disclose such information or the existence of this
Agreement without the prior written consent of the other Party, which consent
may be withheld at either Party's sole discretion, for a period of the later of
one (1) year from the Effective Date or one (1) year from the Closing Date. The
foregoing restriction shall not apply to disclosures and information which (a)
are required to comply with applicable statutes and regulations; (b) are
required to enforce this Agreement; (c) are required to obtain financing related
to the transactions contemplated hereby; (d) enter the public domain through a
third party who does not thereby breach an obligation of confidentiality; (e) is
ascertainable or obtained from public or published information; or (f) are made
in association with press releases issued in accordance with

                                       21
<PAGE>   25
 SECTION 17.03 hereof; or (g) are required in connection with the sale of all or
any part of the Purchased Assets by Purchaser.

                                  ARTICLE XVI

                         CASUALTY LOSS AND CONDEMNATION

         SECTION 16.01. CASUALTY LOSS. If, prior to the Closing Date, all or any
portion of the Purchased Assets is destroyed by fire or other casualty or is
taken in condemnation or under right of eminent domain or proceedings for such
purpose are pending or threatened in writing, Purchaser may elect (a) to have
the affected Purchased Asset or portion thereof removed from the Purchased
Assets, if and only if Purchaser and Seller are able to agree on an appropriate
reduction to the Purchase Price for the value of such Purchased Asset or portion
thereof and, in which case, Seller shall retain any amounts that have been or
will be paid to it by third parties (including insurers) by reason of such
destruction or taking; (b) to purchase such Purchased Assets or portions thereof
notwithstanding any such destruction, taking or pending or threatened taking
(without reduction in the Purchase Price with respect thereto), in which case
Seller shall, at the Closing, pay to Purchaser all sums paid to Seller by third
parties (including insurers) by reason of the destruction or taking of such
Purchased Assets, and shall assign, transfer and set over unto Purchaser all of
Seller's right, title and interest in and to any unpaid awards or other amounts
due from third parties (including insurers) arising out of the destruction,
taking or pending or threatened taking of such Purchased Assets or portions
thereof; or (c) upon written notice to Seller, Purchaser may in its discretion
terminate this Agreement, in which event this Agreement will be terminated and
rendered void AB INITIO and Purchaser shall in such case be entitled to the
return of the Down Payment. Prior to Closing, Seller shall not voluntarily
compromise, settle or adjust any amounts payable by reason of any destruction,
taking or pending or threatened taking as to the Purchased Assets or portions
thereof without first obtaining the written consent of Purchaser.

                                  ARTICLE XVII

                                  MISCELLANEOUS

         SECTION 17.01. TRIAL WAIVERS. TO THE EXTENT ALLOWED BY LAW, THE PARTIES
HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVE THE RIGHT EITHER OF THEM
MAY HAVE TO A TRIAL BY JURY WITH RESPECT TO ANY AND ALL ISSUES PRESENTED IN ANY
ACTION, PROCEEDING, CLAIM OR COUNTERCLAIM BROUGHT BY ANY OF THE PARTIES HERETO
AGAINST ANY OTHER PARTY OR ITS SUCCESSORS WITH RESPECT TO ANY MATTER ARISING OUT
OF OR IN CONNECTION WITH THIS AGREEMENT, THE TRANSACTIONS CONTEMPLATED HEREIN,
THE RELATIONSHIP OF SELLER AND PURCHASER, PURCHASER'S USE OF THE PURCHASED
ASSETS, ANY CLAIM FOR INJURY OR DAMAGE, AND/OR ANY EMERGENCY OR STATUTORY
REMEDY. THIS WAIVER BY THE PARTIES HERETO OF ANY RIGHT EITHER MAY HAVE TO A
TRIAL BY JURY HAS BEEN NEGOTIATED AND IS AN ESSENTIAL ASPECT OF THEIR BARGAIN.
FURTHERMORE, THE PARTIES HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVE
THE

                                       22
<PAGE>   26

RIGHT THEY MAY HAVE TO SEEK PUNITIVE DAMAGES, CONSEQUENTIAL DAMAGES OR EXEMPLARY
DAMAGES FROM THE OTHER WITH RESPECT TO ANY AND ALL ISSUES PRESENTED IN ANY
ACTION, PROCEEDING, CLAIM OR COUNTERCLAIM BROUGHT BY EITHER PARTY WITH RESPECT
TO ANY MATTER ARISING OUT OF OR IN CONNECTION WITH THIS AGREEMENT OR ANY
DOCUMENTS CONTEMPLATED HEREIN OR RELATED HERETO. THE WAIVER BY THE PARTIES OF
ANY RIGHT THEY MAY HAVE TO SEEK PUNITIVE DAMAGES, CONSEQUENTIAL DAMAGES OR
EXEMPLARY DAMAGES HAS BEEN NEGOTIATED BY THEM AND IS AN ESSENTIAL ASPECT OF
THEIR BARGAIN.

         SECTION 17.02. BINDING ARBITRATION.

                  (a) ARBITRATION OF DISPUTES. Except for matters necessitating
         injunctive or other equitable relief, on the request of any Party
         hereto, whether made before or after the institution of any legal
         proceeding, any action, dispute, claim or controversy of any kind now
         existing or hereafter arising between any of the Parties hereto in any
         way arising out of, pertaining to or in connection with this Agreement,
         any agreement executed in connection with this Agreement or the
         relationship between the Parties hereto (a "Dispute") shall be resolved
         by binding arbitration in accordance with the terms hereof. Any Party
         may, by summary proceedings, bring an action in court to compel
         arbitration of any Dispute.

                  (b) GOVERNING RULES. Any arbitration shall be administered by
         the AAA in accordance with the terms of this Section, the Commercial
         Arbitration Rules of the AAA, and, to the maximum extent applicable,
         the Federal Arbitration Act. Judgment on any award rendered by an
         arbitrator may be entered in any court having jurisdiction.

                  (c) ARBITRATORS. Any arbitration shall be conducted before one
         arbitrator. The arbitrator shall be a practicing attorney licensed to
         practice law in the State of Texas who is knowledgeable in the subject
         matter of the Dispute, selected by agreement between the Parties
         hereto. If the Parties cannot agree on an arbitrator within thirty (30)
         calendar days after the request for an arbitration, then the
         arbitration shall be conducted before three (3) arbitrators; one
         selected by Seller, one selected by Purchaser, and the third selected
         by the first two arbitrators. The arbitrator(s) may engage engineers,
         accountants or other consultants that the arbitrator(s) deem(s)
         necessary to render a conclusion in the arbitration proceeding.

                  (d) CONDUCT OF ARBITRATION. To the maximum extent practicable,
         an arbitration proceeding hereunder shall be concluded within one
         hundred and eighty (180) calendar days of the filing of the Dispute
         with the AAA. Arbitration proceedings shall be conducted in Dallas,
         Texas. Arbitrators shall be empowered to impose sanctions and to take
         such other actions as the arbitrators deem necessary to the same extent
         a judge could impose sanctions or take such other actions pursuant to
         the Federal Rules of Civil Procedure and applicable law. At the
         conclusion of any arbitration proceeding, the arbitrator(s) shall make
         specific written findings of fact and conclusions of law. The
         arbitrator(s) shall have the power to award recovery of all costs and
         fees (including

                                       23
<PAGE>   27

         reasonable attorneys' fees) to the prevailing party. Each party agrees
         to keep all Disputes and arbitration proceedings strictly confidential
         except for disclosure of information required by applicable law.

                  (e) COSTS OF ARBITRATION. All fees of the arbitrator(s) and
         any engineer, accountant or other consultant engaged by the
         arbitrator(s), shall be shared by the Parties equally unless otherwise
         awarded by the arbitrator(s).

         SECTION 17.03. PRESS RELEASES AND PUBLIC ANNOUNCEMENTS. Neither Party
shall issue any press release or make any public announcement relating to the
subject matter of this Agreement prior to the Closing without the prior approval
of the other Party, which approval shall not be unreasonably withheld; provided,
however, that either Party may make any public disclosure it believes in good
faith is required by applicable law or any listing or trading agreement
concerning its publicly traded securities (in which case the disclosing Party
will use its reasonable best efforts to advise the other Party prior to making
the disclosure).

         SECTION 17.04. ENTIRE AGREEMENT; AMENDMENT. This Agreement supersedes
all previous contracts and constitutes the entire agreement of whatsoever kind
or nature existing between or among the Parties representing the within subject
matter and no Party shall be entitled to benefits other than those specified
herein. As between or among the Parties, no oral statement or prior written
material not specifically incorporated herein shall be of any force and effect.
The Parties specifically acknowledge that in entering into and executing this
Agreement, the Parties are relying solely upon the representations and
agreements contained in this Agreement and no others. All prior representations
or agreements, whether written or verbal, not expressly incorporated herein are
superseded unless and until made in writing and signed by all Parties hereto.
The representations and warranties set forth in this Agreement shall survive
Closing and the execution and delivery of all other agreements described,
referenced or contemplated herein and shall not be merged herewith or therewith.

         SECTION 17.05. SUCCESSORS AND ASSIGNS. This Agreement shall inure to
the benefit of, and be binding upon, the Parties hereto and their respective
successors, heirs, representatives and assigns, as the case may be; provided,
however, that no Party shall assign or delegate this Agreement or any of the
rights or obligations created hereunder without the prior written consent of the
other. Nothing in this Agreement shall confer upon any Person not a Party to
this Agreement, or the legal representatives of such Person, any rights
(including, without limitation, rights as a third party beneficiary) or remedies
of any nature or kind whatsoever under or by reason of this Agreement.

         SECTION 17.06. FACSIMILE; COUNTERPARTS. Signatures on this Agreement
may be communicated by facsimile transmission and shall be binding upon the
Parties transmitting the same by facsimile transmission. Counterparts with
original signatures shall be provided to the other Party within five (5) days of
the applicable facsimile transmission; provided, however, that the failure to
provide the original counterpart shall have no effect on the validity or binding
nature of the Agreement. If executed in counterparts, the Agreement shall be
effective as if simultaneously executed.

                                       24
<PAGE>   28

         SECTION 17.07. HEADINGS. The section headings contained in this
Agreement are inserted for convenience only and shall not affect in any way the
meaning or interpretation of this Agreement.

         SECTION 17.08. GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the domestic laws of the State of Texas without
giving effect to any choice or conflict of law provision or rule (whether of the
State of Texas or any other jurisdiction) that would cause the application of
the laws of any jurisdiction other than the State of Texas.

         SECTION 17.09. LEGAL FEES AND COSTS. If either Party elects to incur
legal expenses to enforce or interpret any provision of this Agreement, the
prevailing Party (as determined by the trier of fact) shall be entitled to
recover such legal expenses, including, without limitation, attorneys' fees,
costs and necessary disbursements, in addition to any other relief to which such
Party shall be entitled.

         SECTION 17.10. SCHEDULES, EXHIBITS AND OTHER INSTRUMENTS. Each
certificate, written disclosure required herein and the Schedules and Exhibits
hereto shall be considered a part hereof as if set forth herein in full. The
Schedules and Exhibits and all written disclosures hereto shall be updated by
Seller as of Closing and are subject to the written approval of Purchaser as of
Closing. Any other provision herein to the contrary notwithstanding, the
Schedules and all certificates, written disclosures or other instruments
provided for herein and not delivered at the time of execution of this Agreement
or which are incomplete at the time of execution of this Agreement shall be
delivered or completed on or before Closing, and it shall be deemed a condition
precedent to Closing hereunder that the Schedules and each such certificate,
written disclosure or other instrument shall meet with the approval of the Party
to whom the Schedules or such certificate, written disclosure or other
instrument is to be delivered hereunder.

         SECTION 17.11. WAIVER. Any of the terms, provisions, covenants,
representations, warranties or conditions hereof may be waived only by written
instrument executed by the Party waiving the compliance. The failure of either
Party at any time or times to require performance of any provisions hereof shall
in no manner affect such Party's right to enforce the same. No waiver by either
Party of any condition or of the breach of any term, provision, covenant,
representation or warranty contained in this Agreement, whether by conduct or
otherwise, in any one or more instances, shall be deemed to be construed as a
further or continuing waiver of any such condition or breach, or a waiver of any
other condition or of the breach of any other term, provision, covenant,
representation or warranty.

         SECTION 17.12. RESIGNATION AS OPERATOR. Within a reasonable period of
time following the Closing, Seller shall execute and deliver to Purchaser
appropriate letters resigning as the operator of any of the Purchased Assets
that Seller is operating and other appropriate documents concerning the transfer
of operations. Purchaser acknowledges and agrees that Seller cannot and does not
covenant or warrant that Purchaser shall become successor operator of all or any
portion of the Purchased Assets, since the Purchased Assets or portions thereof
may be subject to unit, pooling, communitization, operating or other agreements
which control the appointment of a successor operator; provided, however, that
Seller agrees to use its reasonable best efforts to assist Purchaser in becoming
successor operator.

                                       25
<PAGE>   29

         SECTION 17.13. NOTICES. All notices, requests, demands, claims and
other communications hereunder will be in writing. Any notice, request, demand,
claim or other communication hereunder shall be deemed duly given if (and then
two business days after) it is sent by registered or certified mail, return
receipt requested, postage prepaid, and addressed to the intended recipient as
set forth below:

         If to Purchaser:

                  Humphrey-Hill, L.P.
                  3500 Oak Lawn Avenue, Suite 590
                  Dallas, Texas  75219
                  Attention: Charles B. Humphrey
                             J.M. Hill
                  Telephone: (214) 528-9620 x101
                  Fax: (214) 528-9621

         If to Seller:

                  Nebraska Public Gas Agency
                  1111 "O" Street, 2nd floor
                  Lincoln, Nebraska  68508
                  Attention: Mr. Roger Mock
                  Telephone: (402) 474-4759
                  Fax: (402) 474-0473

         With Copies to:

                  Kutak Rock LLP
                  717 17th Street, Suite 2900
                  Denver, CO  80202
                  Attention: Robert C. Roth, Jr., Esq.
                  Telephone: (303) 297-2400
                  Fax: (303) 292-7799

Any Party may send any notice, request, demand, claim, or other communication
hereunder to the intended recipient at the address set forth above using any
other means (including personal delivery, expedited courier, messenger service,
telecopy, telex, ordinary mail, or electronic mail), but no such notice,
request, demand, claim, or other communication shall be deemed to have been duly
given unless and until it actually is received by the intended recipient. Any
Party may change the address to which notices, requests, demands, claims, and
other communications hereunder are to be delivered by giving the other Party
notice in the manner herein set forth.

         SECTION 17.14. SEVERABILITY. Any term or provision of this Agreement
that is invalid or unenforceable in any situation and in any jurisdiction shall
not affect the validity or enforceability of the remaining terms and provisions
hereof or the validity or enforceability of the offending term or provision in
any other situation or in any other jurisdiction.

                                       26
<PAGE>   30

         SECTION 17.15. NO THIRD-PARTY BENEFICIARIES. This Agreement shall not
confer any rights or remedies upon any Person other than the Parties and their
respective successors and permitted assigns, and other Persons given rights of
indemnification hereunder.

         SECTION 17.16. CONSTRUCTION. The Parties have participated jointly in
the negotiating and drafting of this Agreement. In the event ambiguity or
question of intent or interpretation arises, this Agreement shall be construed
as if drafted jointly by the Parties and no presumption or burden of proof shall
arise favoring or disfavoring either Party by virtue of the authorship of any of
the provisions of this Agreement. Any reference to any federal, state, local or
foreign statute or law shall be deemed also to refer to all rules and
regulations promulgated thereunder, unless the contexts requires otherwise. The
word "including" shall mean including, without limitation. If the date specified
in this Agreement for giving any notice or taking any action is not a business
day (or if the period during which any notices required to be given or any
action taken expires on a date which is not a business day) then the date for
giving such notice or taking such action (and the expiration date for such
period during which notice is required to be given or action taken) shall be the
next day which is a business day.

                  [Remainder of page intentionally left blank]

                                       27
<PAGE>   31

         IN WITNESS WHEREOF, the Parties hereto have executed this Agreement as
of the date first above written.

                                       PURCHASER:

                                       HUMPHREY-HILL, L.P.
                                       By Humphrey Oil Corp., General Partner

                                       /s/ CHARLES B. HUMPHREY
                                       ---------------------------------------
                                       Charles B. Humphrey, President

                                       SELLER:

                                       NEBRASKA PUBLIC GAS AGENCY

                                       By /s/ RICHARD M. DUXBURY
                                         -------------------------------------
                                       Richard M. Duxbury
                                       Executive Director

                                       28
<PAGE>   32

                             EXHIBITS AND SCHEDULES

         EXHIBITS
         --------

         Exhibit A         -        Definitions
         Exhibit B         -        Leases
         Exhibit C         -        Wells
         Exhibit D         -        Equipment
         Exhibit E         -        Contracts
         Exhibit F         -        Conveyance Documents
         Exhibit G         -        Seller's Deliveries at Closing
         Exhibit H         -        Purchaser's Deliveries at Closing

         SCHEDULES
         ---------

         Schedule 4.02(e)  Litigation and Claims
         Schedule 4.02(f)  Encumbrances
         Schedule 4.02(g)  Taxes
         Schedule 4.02(h)  Violations
         Schedule 4.02(j)  Royalties
         Schedule 4.02(k)  Permits and Licenses
         Schedule 4.02(l)  Governmental Audits
         Schedule 4.02(m)  Gas Balances
         Schedule 4.02(n)  Environmental Matters

                                       29
<PAGE>   33

                                    EXHIBIT A

         ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

                                   DEFINITIONS

         "AAA" has the meaning set forth in SECTION 14.01(i).

         "AFE" has the meaning set forth in SECTION 5.01(b).

         "AFFILIATE," "AFFILIATES" or "AFFILIATED" or any variation thereof
means, with respect to any Person, (a) a Person directly or indirectly
controlling, controlled by, or under common control with such Person; (b) a
Person having common ownership with such Person; (c) a person owning or
controlling ten percent (10%) or more of the outstanding voting interests of
such Person; (d) an officer, director, manager, or general partner of such
Person; or (e) a Person who is an officer, director, manager, general partner,
trustee or holder of ten percent (10%) or more of the voting interests of any
Person described in clauses (a) through (d) of this sentence. For purposes of
this definition, the term "control" refers to possession by a person of the
power, direct or indirect, to direct or cause the direction of the management
and policies of another person, whether through the ownership of voting
securities, by contract or otherwise.

         "AGREED RATE" means a per annum interest rate equal to the lesser of
(a) the Prime Rate of interest as quoted daily (or at such other interval of one
week or less) in The Wall Street Journal or (b) the maximum amount of interest
allowed by law. If The Wall Street Journal ceases to quote the Prime Rate of
interest at least weekly, the referenced rate of interest in (a) above shall be
the rate of interest from time to time announced as its prime commercial lending
rate by the bank which at the most recent point in time held all or the large
portion of the Purchaser's bank debt.

         "ASSUMED LIABILITIES" has the meaning set forth in SECTION 7.02.

         "CLOSING" has the meaning set forth in SECTION 3.01.

         "CLOSING AMOUNT" has the meaning set forth in SECTION 2.03.

         "CLOSING DATE" has the meaning set forth in SECTION 3.01.

         "CODE" means the Internal Revenue Code of 1986, as amended.

         "CONTRACTS" has the meaning set forth in SECTION 1.01(f).

         "CONVEYANCE DOCUMENTS" means those forms of assignments, bills of sale,
deeds and other instruments the Parties agree are necessary or appropriate to
convey title to the Purchased Assets from Seller to Purchaser.

         "DISPUTE" has the meaning set forth in SECTION 17.02(a).

<PAGE>   34

         "DOWN PAYMENT" has the meaning set forth in SECTION 2.01.

         "EFFECTIVE DATE" has the meaning ascribed thereto in SECTION 1.02.

         "ENVIRONMENTAL LAWS" means all federal, state, and local laws,
regulations, ordinances, rules, orders and permits relating to the control of
any pollutant or protection of the environment, including, without limitation,
laws, regulations, ordinances, rules, orders, and permits relating to the
emission, discharge, disposal, treatment, recycling, reclamation, permitting,
manufacture, processing, distribution, generation, storage, transportation,
release or threatened release of, or exposure of persons or property to,
Materials of Environment Concern.

         "ENVIRONMENTAL LIABILITIES" means any and all costs (including
remedial, removal, response, abatement, cleanup, investigative, and/or
monitoring costs), damages, settlements, expenses (including charges and
assessments, and expenses and costs of investigating, preparing or defending any
action or proceeding), liens, penalties, fines, taxes, pre-judgment and
post-judgment interest, court costs and attorneys' fees incurred or imposed (i)
pursuant to any agreement, order, notice of responsibility, directive (including
requirements embodied in Environmental Laws), injunction, judgment or similar
documents (including settlements) attributable to or arising out of or under
Environmental Laws, (ii) pursuant to any claim by a government authority or
other entity or person for personal injury, property damage, damage to natural
resources, remediation or response costs arising out of or associated with any
Environmental Matter, or (iii) pursuant to requirements as of the Closing Date
embodied in Environmental Laws. Environmental Liabilities do not include (i)
liabilities imposed under statutes enacted after the Closing Date (including the
elimination of the exclusion of petroleum from the definition of "hazardous
substance" under the Comprehensive Environmental Response, Compensation, and
Liability Act of 1980 and the elimination of the exclusion of oil and gas
exploration, development and production wastes from the definition of "hazardous
wastes" under the Resource Conservation and Recovery Act) or (ii) liabilities
imposed under regulations promulgated or amended after the Closing Date which
implement new requirements.

         "ENVIRONMENTAL MATTERS" means matters resulting from or attributable to
actual, threatened or alleged emissions, discharges or releases of Materials of
Environmental Concern into ambient air, surface water, groundwater, or land, or
otherwise resulting from or attributable to the manufacture, processing,
distribution, use, treatment, storage, disposal, transport or handling of
Materials of Environmental Concern.

         "EQUIPMENT" means all of the tangible personal property, tools,
machinery, materials, pipelines, equipment, fixtures and improvements, which are
incident or attributable to the Wells, Leases and/or Lands or with the
production, treatment, sale or disposal of Hydrocarbons or water produced
therefrom or attributable thereto, on the Effective Date.

         "EXCLUDED ASSETS" has the meaning set forth in SECTION 1.03.

         "FINAL SETTLEMENT DATE" has the meaning set forth in SECTION 14.01(h).

         "FINAL SETTLEMENT STATEMENT" has the meaning set forth in SECTION
14.01(h).

                                       2

<PAGE>   35

         "GOOD AND DEFENSIBLE TITLE" means, with respect to ownership of Leases
attributable to a Well or Unit, a record title that:

                  (a) entitles Seller to receive, throughout the life of a Well
         or Unit, at least the NRI for such Well or Unit shown in EXHIBIT C,
         except for decreases in connection with those operations as to which an
         election is made by Purchaser after Closing or with Purchaser's
         consent, to become a non-consenting co-owner and decreases resulting
         from those Wells or Units where Seller is obligated to allow others to
         make up past underproduction and except for horizontal/vertical Pugh
         clauses and continuous development clauses in the Leases or related
         agreements;

                  (b) obligates Seller to bear, throughout the life of a Well or
         Unit (and the plugging, abandonment and salvage thereof), no greater WI
         for such Well or Unit than the WI shown therefor in EXHIBIT C, except
         increases in such WI that result in at least a proportionate increase
         in Seller's NRI for such Well or Unit (including, without limitation,
         increases resulting from co-owner nonconsents) and increases that
         result from contribution requirements with respect to defaulting
         co-owners; and

                  (c) is free and clear of all liens, security interests,
         collateral assignments, encumbrances, irregularities and defects except
         for Permitted Encumbrances.

         "HYDROCARBONS" means crude oil, natural gas, casinghead gas, coalbed
methane, condensate, helium, sulphur, SO(2), CO(2), natural gas liquids and
other gaseous and liquid hydrocarbons or any combination thereof.

         "INDEMNIFIED PARTY" has the meaning set forth in SECTION 11.04.

         "INDEMNIFYING PARTY" has the meaning set forth in SECTION 11.04.

         "KNOWLEDGE" means, with respect to a Party hereto, the actual awareness
of facts or other information of any officer or manager of such Party in charge
of a discrete business area or function having responsibility for the referenced
matter, without due inquiry by such officer or manager.

         "LANDS" has the meaning set forth in SECTION 1.01(a).

         "LEASES" has the meaning set forth in SECTION 1.01(a).

         "LICENSES" has the meaning set forth in SECTION 1.01(e).

         "LITIGATION AND CLAIMS" has the meaning set forth in SECTION 4.02(e).

         "LOSS" or "LOSSES" means all damages, payments, penalties, fines,
assessments, costs, amounts paid in settlement, obligations, taxes, losses
(including reductions in the value of Purchased Assets), liabilities, expenses
and fees incurred, including court costs and attorneys' fees and expenses and
costs of investigating, preparing or defending any action or proceeding.

                                       3
<PAGE>   36

         "MATERIAL ADVERSE EVENT" means Losses or potential Losses that cause or
could cause a reduction in the Purchase Price of more than 25%.

         "MATERIALS OF ENVIRONMENTAL CONCERN" means any chemical pollutants,
contaminants, waste, petroleum waste, used oil, toxic substances, hazardous
substances and any other substances that are regulated by any governmental
entity under any Environmental Law.

         "NRI" means a fractional or percentage interest in and to all
Hydrocarbons produced from or allocated to a Well after deduction of all
lessor's royalties, overriding royalties, and other burdens and payments out of
production that burden such fractional or percentage interest in such Well.

         "ORGANIZATION" means a Person other than a natural person. Organization
includes, without limitation, corporations (both nonprofit and other
corporations), partnerships (including limited partnerships, general
partnerships, limited liability partnerships and limited liability limited
partnerships), joint ventures, limited liability companies, trusts, business
trusts, cooperatives, unincorporated associations and other business entities,
or any foreign trust or foreign business entities, but the term does not include
joint tenancies and tenancies by the entirety.

         "PARTIES" has the meaning set forth in the preface above.

         "PECOS COUNTY, TEXAS" has the meaning set forth in the Recitals.

         "PERMITTED ENCUMBRANCES" shall have the meaning ascribed thereto in
SECTION 1.04.

         "PERSON" means an individual, trust, estate or Organization.

         "PHASE I ENVIRONMENTAL AUDIT" means an assessment of Seller's
compliance with Environmental Laws relative to the Purchased Assets consisting
of examination of Seller's files and public documents, interviews of personnel
of Seller and of other appropriate persons visual inspection of the Purchased
Assets and NORM surveys.

         "PRELIMINARY SETTLEMENT STATEMENT" has the meaning set forth in SECTION
2.03.

         "PURCHASE PRICE" has the meaning ascribed thereto in SECTION 2.01.

         "PURCHASED ASSETS" shall have the meaning ascribed thereto in SECTION
1.01.

         "PURCHASER" has the meaning set forth in the preface to this Agreement.

         "RECORDS" means all originals, copies, computer tapes and discs, files,
records, information or data relating to the Purchased Assets in the possession
of Seller, including, without limitation, title records (including abstracts of
title, title opinions, certificates of title and title curative documents),
accounting records and files, contracts, correspondence, production records,
electric logs, core data, pressure data, decline curves, graphical production
curves, drilling reports, well completion reports, drill stem test charts and
reports, engineering reports, regulatory reports, and all related materials,
INSOFAR AND ONLY INSOFAR as the

                                       4
<PAGE>   37

foregoing items constitute materials that may be lawfully conveyed to Purchaser
(i.e. the materials are not subject to a proprietary agreement precluding their
transfer to Purchaser);

         "SELLER" has the meaning set forth in the preface. The term "Seller"
also shall include any wholly-owned subsidiary of Seller that has an interest in
the Purchased Assets.

         "SURVIVAL PERIOD" has the meaning set forth in SECTION 11.01.

         "THIRD PARTY CLAIM" has the meaning set forth in SECTION 11.04.

         "TITLE DEFECT" means any lien, security interest, collateral
assignment, charge, obligation, encumbrance, irregularity of title or other
condition that causes Seller's title to one or more of the Leases (or any
portions thereof) to be less than Good and Defensible Title.

         "TITLE DEFECT NOTICE" has the meaning set forth in SECTION 8.02(b).

         "TRANSFER REQUIREMENTS" means all consents, approvals, authorizations
or permits of, or filings with or notifications to, any third party which must
be obtained, made or complied with for or in connection with the transactions
contemplated by this Agreement in order (a) for such transactions to be
effective, (b) to prevent any termination, cancellation, default, acceleration
or change in terms (or any right thereof from arising) under any terms,
conditions or provisions of any Asset (or of any agreement, instrument or
obligation relating to or burdening any Purchased Asset or any interest therein
or portion thereof) as a result of such transactions, or (c) to prevent the
creation or imposition of any lien, charge, penalty, restriction, security
interest or encumbrance on or with respect to any Purchased Asset or any
interest therein or portion thereof (or any right thereof from arising) as a
result of such transactions.

         "UNITS" means all unitization, communitization,
pooling agreements, working interest units created by operating agreements, and
orders covering the Lands subject to the Leases, or any portion thereof, and the
units and pooled or communitized areas created thereby.

         "WELLS" has the meaning set forth in SECTION 1.1(b).

         "WI" means a fraction or percentage of the costs and expenses
associated with the maintenance, exploration, development, operation and
abandonment of a Well.

                                       5
<PAGE>   38

                                    EXHIBIT B-1

         ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

                                     LEASES

         All of the Seller's right, title and interest in and to the oil gas and
mineral leases described in or covered by the following described assignments
and unit agreements or covering lands described therein, as of the Effective
Date:

1.       Assignment, Bill of Sale and Conveyance from Union Pacific Oil and Gas
         Company to Nebraska Public Gas Agency recorded in Volume 688 at Page
         495 of the real property records of Pecos County, Texas.

2.       Correction Assignment, Bill of Sale and Conveyance from Union Pacific
         Oil and Gas Company to Nebraska Public Gas Agency recorded in Volume
         694 at Page 130 of said records.

3.       Assignment from Value Petroleum, Inc. to Nebraska Public Gas Agency
         recorded in Volume 694 at Page 144 of said records.

4.       Assignment from Headington Penn Corp. to Nebraska Public Gas Agency
         recorded in Volume 694 at Page 148 of said records.

5.       Assignment and Bill of Sale from The Clayton Williams Partnership, Ltd.
         to Nebraska Public Gas Agency recorded in Volume 702 at Page 497 of
         said records.

said leases being further described on Exhibit B-2 attached hereto.

                                      UNITS

6.       Gomez South Unit No. 1 - Unitization Agreement dated as of 6-21-72 and
         recorded in Volume 420 at Page 1 of the real property records of Pecos
         County, Texas.

                  Gomez #1-A                         Gomex #1(D)

7.       Gomez South Unit No. 2 - Declaration of Pooled Unit dated as of 4-2-73
         and recorded in Volume 430 at Page 81 of said records.

                  Gomez #2

8.       Gomez South Unit No. 3 - Declaration of Pooled Gas Unit dated as of
         3-1-74 and recorded in Volume 449 at Page 331 of said records.

                  Gomez #3A

<PAGE>   39

9.       FSOC - Leon Gas Unit No. 1 - Declaration of Pooled Unit dated as of
         7-28-70 and recorded in Volume 396 at Page 19 of said records and
         Unitization Agreement dated effective 7-10-70 and recorded in Volume
         394 at Page 109 of said records.

                  FSOC - Leon #1

10.      FSOC - Dixel Resources Unit No. 1 - Declaration of Pooled Unit dated as
         of 12-20-71 and recorded in Volume 412 at Page 598 of said records.

                  FSOC Dixel #1 (TA)

11.      FSOC - Dixel Resources Unit No. 2 - Declaration of Pooled Unit dated as
         of 7-15-71 and recorded in Volume 408 at Page III of said records and
         Unitization Agreement dated effective 7-8-71 and recorded in Volume 407
         at Page 567 of said records.

                  FSOC Dixel #2

12.      OXY - Sabine Gas Unit - Declaration of Pooled Unit dated as of August
         4, 1978 and recorded in Volume 531 at Pages 298, 303, 308, 313, 318 and
         323 of said records.

                  Sabine #1

13.      Phillips - Dixel Resources Unit - Unitization Agreement dated October
         8, 1973, and recorded in Volume 443, at Page 336 of said records.

                  Dixel Resource Unit

                                       2

<PAGE>   40

                                   EXHIBIT B-2

         ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

         ALL OF SELLER'S RIGHT, TITLE AND INTEREST IN AND TO THE FOLLOWING
DESCRIBED OIL AND GAS LEASES. ALL RECORDING REFERENCES HEREIN ARE TO THE REAL
PROPERTY RECORDS OF PECOS COUNTY, TEXAS.

<TABLE>
<CAPTION>
LESSOR                     LESSEE                      BOOK              PAGE                    WELL(S)
------                     ------                      ----              ----                    -------
<S>                        <C>                         <C>              <C>                     <C>
Jo Ann Montgomery          J.B. Wilkinson, Jr.         507               338                     Sabine #1
Moore

Jack B. Wilkinson          Oxy Petroleum,              546               585                     Sabine #1
                           Inc., et al

Sabine Corporation         Sabine Production           528                43                     Sabine #1
                           Company

Mary E. McCampbell         W.F. Kissling               524               105                     Sabine #1

Montebev, Inc.             Sam F. Hurt, Jr.            460               438                     Sabine #1

Louise Montgomery          Humble Oil &                424                59                     Sabine #1
Faulk, et al               Refining Company

Carl E. Haterius,          L.H.& S.A. Olson            215               135                     Gomez #1-A
et al                      Drilling Co.                                                          Gomez #1-D

Hugo B. Haterius,          L.H.& S.A. Olson            215               138                     Gomez #1-A
as Guardian of             Drilling Co.                                                          Gomez #1-D
the Estate of
Terrance Edward
Haterius

G.H. Crone, et ux          L.H.& S.A. Olson            208               239                     Gomez #1-A
                           Drilling Co.                                                          Gomez #1-D

G.H. Crone, et ux          L.H.& S.A. Olson            208               242                     Gomez #1-A
                           Drilling Co.                                                          Gomez #1-D
</TABLE>

<PAGE>   41

<TABLE>
<CAPTION>
LESSOR                     LESSEE                      BOOK              PAGE                    WELL(S)
------                     ------                      ----              ----                    -------
<S>                        <C>                         <C>              <C>                     <C>
Leon Land &                Pecos Exploration           203                69                     Gomez #1-A
Cattle Company             Company                                                               Gomez #1-D
                                                                                                 Leon #1
                                                                                                 Dixel #1
                                                                                                 Dixel #2

Leon Land &                C.H. Priddy                 196               281                     Leon #1
Cattle Company                                                                                   Dixel #2

Leon Land &                C.H. Priddy                 196               277                     Leon #1
Cattle Company

Leon Land &                Pecos Exploration           277               271                     Gomez #1-A
Cattle Company             Company                                                               Gomez #1-D

Edward Dickinson II        J.S. Meriwether, Jr.        234               458                     Gomez #2
                                                                                                 Gomez #3A-1

Edward Dickinson II        J.S. Meriwether, Jr.        234               464                     Gomez #2
                                                                                                 Gomez #3A-1

McMullen Oil               J.S. Meriwether,            237                23                     Gomez #2
Royalty Company            Jr.                                                                   Gomez #3A-1

Leon Land & Cattle         Ladd Petroleum              392               154                     Leon #1
Company                    Corporation                                                           Dixel #2

Ft. Stockton Oil           Ladd Petroleum              391               489                     Leon #1
Company                    Corporation                 393               211                     Dixel #1
                                                                                                 Dixel #2
                                                                                                 Gomez #1-A
                                                                                                 Gomez #1-D

USM Oil Company            Clayton W.                  392               459                     Gomez #2
                           Williams, Jr.                                                         Gomez #1-A
                                                                                                 Gomez #1-D
                                                                                                 Gomez #3A-1

Dixel Resources, Inc.      Ladd Petroleum              416               717                     Gomez #2
                           Corporation                                                           Gomez #3
                                                                                                 Gomez #1-A
                                                                                                 Gomez #1-D
</TABLE>

                                       2

<PAGE>   42
<TABLE>
<CAPTION>
LESSOR                     LESSEE                      BOOK              PAGE                    WELL(S)
------                     ------                      ----              ----                    -------
<S>                        <C>                         <C>              <C>                     <C>
Ft. Stockton Oil           Ladd Petroleum              416               713                     Gomez #2
Company                    Corporation                                                           Gomez #3
                                                                                                 Gomez #1-A
                                                                                                 Gomez #1-D

Dixel Resources, Inc.      Ladd Petroleum              418                57                     Gomez #1-A
                           Corporation                                                           Gomez #1-D

Eva M. Kirksey             Dan V. Rodgers              416               104                     Gomez #1-A
                                                                                                 Gomez #1-D

Weimer W. Kirksey          Dan V. Rodgers              416               108                     Gomez #1-A
et al                                                                                            Gomez #1-D

Della K. Nolen             Dan V. Rodgers              416               112                     Gomez #1-A
                                                                                                 Gomez #1-D

Zelda Boozer et al         Dan V. Rodgers              416               116                     Gomez #1-A
                                                                                                 Gomez #1-D

Dixel Resources, Inc.      Southern Union              435               190                     Dixel Res.
                           Production Company

Dixel Resources Inc.       Texas Oil & Gas Corp.       418                15                     Gomez #3A-1
                           Production Company
</TABLE>

                                       3

<PAGE>   43

                                    EXHIBIT C

         ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

                                SCHEDULE OF WELLS

<TABLE>
<CAPTION>
WELL                                   WORKING INTEREST                     NET REVENUE INTEREST
----                                   ----------------                     --------------------
<S>                                    <C>                                 <C>

*FSOC DIXEL RESOURCES #1                 .83846700                              .72207110

FSOC-DIXEL RESOURCES #2                  .73720000                              .65580490

GOMEZ SO. UNIT #1                        .80743940                              .65168940

GOMEZ SO. UNIT #1-A                      .80743940                              .65168940

GOMEZ SO. UNIT #2                        .82176000                              .62700390

GOMEZ SO. UNIT #3A-1                     .41053280                              .40110350

*DIXEL RESOURCES UNIT                    .01779480                              .01402510

FSOC-LEON #1                             .55000000                              .48424110

*SABINE #1                               .12685500                              .09900440
</TABLE>

* THE INTERESTS SET FORTH HEREIN ARE THOSE CONVEYED BY UNION PACIFIC OIL AND GAS
COMPANY TO SELLER BY ASSIGNMENT, BILL OF SALE AND CONVEYANCE RECORDED IN VOLUME
688 AT PAGE 495 OF THE REAL PROPERTY RECORDS OF PECOS COUNTY, TEXAS, AND BY
CORRECTION ASSIGNMENT, BILL OF SALE AND CONVEYANCE RECORDED IN VOLUME 694 AT
PAGE 130 OF SAID RECORDS. AS WITH ALL OF THE WELLS SET FORTH HEREIN, SELLER HAS
NOT INDEPENDENTLY VERIFIED THE AMOUNT OF SAID INTERESTS, AND PURCHASER
ACKNOWLEDGES AND AGREES THAT IT IS RELYING UPON ITS OWN INVESTIGATION AND DUE
DILIGENCE WITH RESPECT TO THE INTERESTS IN ALL OF THE WELLS.

<PAGE>   44

                                    EXHIBIT D

       ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

--------------------------------------------------------------------------------
                              SCHEDULE OF EQUIPMENT
--------------------------------------------------------------------------------

Seller has not independently verified its interest, if any, in the Equipment,
and Purchaser acknowledges and agrees that it is relying upon its own
investigation and due diligence with respect to the Equipment.

GOMEZ FIELD
PECOS COUNTY, TEXAS

FSOC-Dixel Resources #1
-----------------------
         10,000 # Well Head
         500 Bbl Steel Water Tank
         250 Bbl Open Top Fiberglass Water Tank

Gomez S. Unit #1
----------------
         10,000 # Well Head
         300 Bbl Fiberglass Open Top Tank

Gomez S. Unit #1-A
------------------
         10,000 # Well Head

Gomez S. Unit #2
----------------
         10,000 # Well Head

Gomez S. Unit # 3A-1
--------------------
         10,000 # Well Head
         300 Bbl Fiberglass open Top Water Tank

<PAGE>   45

                                    EXHIBIT E

       ATTACHED TO AND MADE A PART OF THAT CERTAIN PURCHASE AND SALE AGREEMENT
DATED FEBRUARY 22, 2000, BY AND BETWEEN NEBRASKA PUBLIC GAS AGENCY, AS SELLER,
AND HUMPHREY-HILL, L.P., AS PURCHASER.

                                    CONTRACTS

Seller has not independently verified its interest, if any, in the following
Contracts, and Purchaser acknowledges and agrees that it is relying upon its own
investigation and due diligence with respect to the Contracts.

1.       JOINT OPERATING AGREEMENT BY AND BETWEEN FOREST OIL CORPORATION, AS
         OPERATOR AND LADD PETROLEUM CORPORATION, ET AL, AS NON-OPERATORS DATED
         MARCH 5, 1971 AND AMENDED BY AMENDMENT TO OPERATING AGREEMENT DATED
         OCTOBER 3, 1985, COVERING THE FSOC-LEON #1 UNIT.

2.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR AND PETRO-LEWIS CORPORATION, AS NON-OPERATOR DATED JULY 13,
         1971, COVERING THE FSOC-DIXEL RESOURCES #1 AND #2.

3.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR, AND CLAYTON W. WILLIAMS, JR., ET AL, AS NON-OPERATORS DATED
         MAY 31, 1972 COVERING THE GOMEZ SOUTH UNIT #1.

4.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR AND FLUOR CORPORATION, AS NON-OPERATOR DATED JULY 19, 1972,
         COVERING THE GOMEZ SOUTH UNIT #1.

5.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR AND DIXEL RESOURCES INCORPORATED, AS NON-OPERATOR DATED
         NOVEMBER 1, 1972, COVERING THE FSOC-DIXEL RESOURCES UNIT #2 .

6.       JOINT OPERATING AGREEMENT BY AND BETWEEN AMOCO PRODUCTION COMPANY, AS
         OPERATOR, AND PHILLIPS PETROLEUM COMPANY, ET AL AS NON-OPERATORS DATED
         APRIL 26, 1973, COVERING THE DIXEL RESOURCES UNIT.

7.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR AND TEXAS OIL & GAS CORPORATION, ET AL, AS NON-OPERATORS DATED
         NOVEMBER 13, 1973, AS AMENDED BY AMENDMENT TO OPERATING AGREEMENT DATED
         DECEMBER 30, 1974, AS AMENDED BY AMENDMENT TO OPERATING AGREEMENT DATED
         FEBRUARY 4, 1976 AND AS AMENDED BY LETTER FROM GETTY OIL COMPANY TO
         LADD PETROLEUM CORPORATION DATED APRIL 23, 1974, COVERING THE GOMEZ
         SOUTH UNIT #3A-1.

8.       JOINT OPERATING AGREEMENT BY AND BETWEEN LADD PETROLEUM CORPORATION, AS
         OPERATOR AND FLUOR OIL AND GAS CORPORATION, ET AL, AS NON-OPERATORS
         DATED DECEMBER 1, 1973, COVERING THE GOMEZ SOUTH UNIT #2.

<PAGE>   46

9.       JOINT OPERATING AGREEMENT BY AND BETWEEN CITIES SERVICE OIL AND GAS
         CORPORATION, AS OPERATOR, AND EXXON CORPORATION, ET AL AS NON-OPERATORS
         DATED AUGUST 29, 1986, COVERING THE SABINE UNIT #1.

10.      AGREEMENT BY AND BETWEEN MORAN EXPLORATION, INC., AS OPERATOR, AND HUNT
         PETROLEUM CORPORATION, ET AL, AS NON-OPERATORS DATED MARCH 19, 1979.

11.      GAS PURCHASE AGREEMENT DATED MARCH 1, 1996, BY AND BETWEEN WESTERN GAS
         RESOURCES, INC., AS BUYER, AND NEBRASKA PUBLIC GAS AGENCY, AS SELLER.

12.      GAS SERVICE AGREEMENT DATED MAY 5, 1998, BY AND BETWEEN NEBRASKA PUBLIC
         GAS AGENCY AND WESTERN GAS RESOURCES, INC.

13.      GOMEZ FIELD MANAGEMENT AGREEMENT BY AND BETWEEN CIMA RESOURCES, L.L.C.
         AND NEBRASKA PUBLIC GAS AGENCY DATED SEPTEMBER 9, 1997.

14.      SALTWATER DISPOSAL AGREEMENT DATED MAY 22, 1998, FULLY EXECUTED ON JUNE
         9, 1998, BETWEEN NEBRASKA PUBLIC GAS AGENCY ("NPGA") AND DALLAS
         OPERATING COMPANY ("DOC"), ASSIGNED BY DOC TO DIAMOND G PRODUCTION
         EFFECTIVE JANUARY 1, 2000.

15.      GAS COMPRESSOR EQUIPMENT MASTER RENTAL AND SERVICING AGREEMENT DATED
         AUGUST 12, 1999, BETWEEN HANOVER COMPRESSOR COMPANY, AS LESSOR, AND
         NEBRASKA PUBLIC GAS AGENCY, AS LESSEE.

                                       2

<PAGE>   47

                                    EXHIBIT F

                              CONVEYANCE DOCUMENTS

                     ASSIGNMENT, BILL OF SALE AND CONVEYANCE

         THIS ASSIGNMENT, BILL OF SALE AND CONVEYANCE (this "Assignment")
executed by NEBRASKA PUBLIC GAS AGENCY, a public body corporate and politic
under the laws of the State of Nebraska, whose address is 1111 "O" Street, 2nd
Floor, Lincoln, Nebraska 68508 (hereinafter called "Assignor") to HUMPHREY-HILL,
L.P. a Texas limited partnership whose address is 3500 Oak Lawn Avenue, Suite
590, Dallas, TX 75219 (hereinafter called "Assignee"), dated effective at 7:00
a.m., Central Standard Time, on January 1, 2000 (hereinafter called the
"Effective Date"). Assignor and Assignee are sometimes referred to collectively
herein as the "Parties" or each individually as a "Party." Capitalized terms
used but not otherwise defined herein shall have the meanings set forth in that
certain Asset Purchase and Sale Agreement, dated February 22, 2000 (the
"Agreement"), by and between Assignor and Assignee.

                                    ARTICLE I

                              CONVEYANCE OF ASSETS

         SECTION 1.01. CONVEYANCE. Assignor, for $10.00 and other good and
valuable consideration in hand paid by Assignee, the receipt and sufficiency of
which are hereby acknowledged and confessed, by these presents does hereby
GRANT, BARGAIN, SELL, CONVEY, ASSIGN, TRANSFER, SET OVER AND DELIVER unto
Assignee:

         All of Assignor's right, title and interest in and to the hereinafter
described properties and interests in Pecos County, Texas, as such right, title
and interest existed on the Effective Date, excluding the Excluded Assets (as
defined below), but including the following assets (all such assets, rights,
title and interests being conveyed to Purchaser hereby are collectively called
the ("Purchased Assets"):

                  (a) Assignor's interests in any and all oil and gas leases
         covering land lying within the boundaries of the units described on
         EXHIBIT A attached hereto ("Lands"), whether such leases are described
         on EXHIBIT A, together with all mineral, royalty, overriding royalty or
         other interests in the oil, gas and other minerals in the Lands
         (collectively, the "Leases");

                  (b) Assignor's interests in the wells located on the Lands, as
         set forth in EXHIBIT B attached hereto (collectively, the "Wells");

                  (c) Assignor's interest in the Equipment located on the Lands
         as set forth on EXHIBIT C attached hereto (collectively, the
         "Equipment");

                  (d) Assignor's interests in the Units covering the Lands and
         subject to the Leases;

<PAGE>   48

                  (e) Assignor's interest in all licenses and permits which
         relate to the Leases, Wells, Lands, Equipment and Units (collectively,
         the "Licenses");

                  (f) Assignor's interest in contracts and other instruments
         (other than bonds posted by Assignor) which concern and relate to any
         of the Leases, Wells, Lands, Units and/or Equipment or the operation
         thereof, INSOFAR AND ONLY INSOFAR as the same concern or relate to the
         Purchased Assets, including without limitation, oil, gas and condensate
         purchase and sale contracts; permits; rights-of-way; easements;
         servitudes; estates; surface leases; farming and farmout agreements;
         division orders and transfer orders; bottom hole agreements; dry hole
         agreements; area-of mutual interest agreements; salt water disposal
         agreements; geologic and geophysical agreements; acreage contribution
         agreements; operating agreements; balancing agreements and unit
         agreements; pooling agreements; pooling orders; communitization
         agreements; processing, gathering, compression and transportation
         agreements; facilities or equipment leases relating thereto or used or
         held for use in connection with the ownership or operation thereof or
         with the production, treatment, sale or disposal of Hydrocarbons; and
         all other contracts and agreements related to the Purchased Assets,
         including but not limited to the contracts described on EXHIBIT D
         attached hereto (collectively, the "Contracts");

                  (g) Assignor's Records and, to the extent transferable, all
         other contract rights, intangible rights (excluding Assignor's
         trademarks and service marks), inchoate rights, choses in action,
         rights under warranties made by prior owners, manufacturers, vendors or
         other third parties, and rights accruing under applicable statutes of
         limitation or prescription, attributable to the Purchased Assets; and

                  (h) Assignor's interest in all payments, and all rights to
         receive payments, including without limitation, all royalties,
         overriding royalties and production payments, with respect to the
         ownership of the production of Hydrocarbons from or the conduct of
         operations with respect to the Purchased Assets and the interest to be
         conveyed to Assignee hereunder accruing after the Effective Date.

         SECTION 1.02. EXCLUDED ASSETS. Except as specifically set forth above,
the following assets, real, personal and mixed, tangible and intangible, owned
by Assignor or its Affiliates, whether or not associated with or employed in the
operations of the Purchased Assets (collectively, "Excluded Assets"), are not
intended by the Parties to be a part of the sale and purchase contemplated
hereunder and Assignor hereby EXCEPTS and RESERVES from this Assignment in favor
of itself, its successors and assigns, forever, the following Excluded Assets:

                  (a) all cash, deposits, checks, funds, accounts receivable,
         notes receivable or similar items attributable to the Purchased Assets
         with respect to any period of time prior to the Effective Date, except
         for those funds in suspense accounts to be delivered to Assignee
         pursuant to the Agreement; and

                  (b) all Hydrocarbon production from or attributable to the
         Purchased Assets with respect to all periods prior to the Effective
         Date and all proceeds attributable thereto,

                                       2

<PAGE>   49

         and all Hydrocarbons that, at the Effective Date, are owned by Assignor
         and are in storage or otherwise held in inventory and all proceeds
         attributable thereto.

                                   ARTICLE II

      DISCLAIMER OF REPRESENTATIONS AND WARRANTIES, PERMITTED ENCUMBRANCES

         SECTION 2.01. DISCLAIMER OF REPRESENTATIONS AND WARRANTIES.

                  (a) EXCEPT AS EXPRESSLY SET FORTH IN THE AGREEMENT, THE
         PURCHASED ASSETS ARE ASSIGNED AND CONVEYED TO ASSIGNEE WITHOUT ANY
         WARRANTY OF TITLE EITHER EXPRESS OR IMPLIED, AND WHETHER BY COMMON LAW,
         STATUTE OR OTHERWISE, EXCEPT THAT ASSIGNOR HEREBY WARRANTS ITS TITLE TO
         THE PURCHASED ASSETS AGAINST PERSONS OR PARTIES CLAIMING TITLE BY,
         THROUGH OR UNDER ASSIGNOR. EXCEPT AS EXPRESSLY SET FORTH IN THE
         AGREEMENT, ALL PERSONAL PROPERTY, EQUIPMENT, FIXTURES AND APPURTENANCES
         CONSTITUTING A PORTION OF THE PURCHASED ASSETS ARE ASSIGNED TO ASSIGNEE
         "AS IS", "WHERE IS," WITHOUT LIMITATION OF THE GENERALITY OF THE
         IMMEDIATELY PRECEDING SENTENCE, ASSIGNOR EXPRESSLY DISCLAIMS AND
         NEGATES AS TO PERSONAL PROPERTY, IMPROVEMENTS AND FIXTURES, ANY
         REPRESENTATION OR WARRANTY, WHETHER EXPRESS OR IMPLIED, AND WHETHER BY
         COMMON LAW, STATUTE OR OTHERWISE, AS TO (A) MERCHANTABILITY, (B)
         FITNESS FOR ANY PARTICULAR PURPOSE, (C) CONFORMITY TO MODELS OR SAMPLES
         OF MATERIALS AND/OR (D) CONDITION, THEREOF.

                  (b) ASSIGNOR MAKES NO WARRANTY OR REPRESENTATION, EXPRESS OR
         IMPLIED, WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF ANY
         INFORMATION, RECORDS OR DATA NOW, HERETOFORE, OR HEREAFTER MADE
         AVAILABLE TO ASSIGNEE IN CONNECTION WITH THE AGREEMENT, INCLUDING
         WITHOUT LIMITATION ANY DESCRIPTION OF THE PURCHASED ASSETS, PRICING
         ASSUMPTIONS, POTENTIAL FOR PRODUCTION OF HYDROCARBONS FROM THE
         PURCHASED ASSETS, OR ANY OTHER MATTERS CONTAINED IN ANY MATERIAL
         FURNISHED BY ASSIGNOR TO ASSIGNEE OR ITS OFFICERS, DIRECTORS,
         EMPLOYEES, AGENTS, ADVISORS OR REPRESENTATIVES.

         SECTION 2.02. PERMITTED ENCUMBRANCES. Without in any way limiting the
provisions of Section 2.01 above, the Purchased Assets are assigned and conveyed
by Assignor and accepted by Assignee expressly subject to the following (the
"Permitted Encumbrances"):

                  (a) liens for taxes not yet due or, if due, being challenged
         in good faith by appropriate proceedings;

                                       3

<PAGE>   50

                  (b) materialmen's, mechanic's and other similar liens or
         charges arising in the ordinary course of business for obligations that
         are not delinquent and that will be paid or discharged in the ordinary
         course of business or, if delinquent, that are being contested in good
         faith in the ordinary course of business;

                  (c) easements, rights-of-way, servitudes, permits, surface
         leases and other rights granted to or reserved for third parties in
         respect of surface operations that do not materially interfere with
         operations of the portion of the Purchased Assets burdened thereby;

                  (d) rights reserved to or vested in any governmental authority
         to control or regulate any of the Leases, Wells or Units and all
         applicable laws, rules, regulations and orders of such authorities;

                  (e) any Title Defects that Assignor may have expressly waived
         in writing or which are deemed to have been waived under the Agreement;

                  (f) liens arising under operating agreements, unitization and
         pooling agreements, order and statutes and production sales contracts
         securing amounts not yet due or, if due, being contested in good faith
         in the ordinary course of business;

                  (g) the terms and conditions of the Leases and the Contracts;

                  (h) royalties, overriding royalties, net profits interests,
         production payments, reversionary interests and similar interests;

                  (i) conventional rights of reassignment requiring notice to
         the holders of the rights prior to surrendering or releasing a
         leasehold interest;

                  (j) calls on production exercisable only at prices
         substantially equivalent to then current fair market value; and

                  (k) all rights to consent by, required notices to, filings
         with or other actions by governmental entities in connection with the
         conveyance of oil and gas leases or interests therein, if they are
         customarily obtained subsequent to the conveyance.

         By Assignee's acceptance of this Assignment, Assignee assumes and
agrees to keep and perform the obligations of Assignor under the Permitted
Encumbrances which accrue from and after the Effective Date.

                                   ARTICLE III

                                  MISCELLANEOUS

         SECTION 3.01. FURTHER ASSURANCES. Without limiting the provisions of
Article II above, Assignor covenants and agrees to execute and deliver to
Assignee all such other and additional instruments and other documents, and take
such other actions, as may be reasonably requested in order to more effectively
assure to Assignee and Assignee's successors and assigns all of the

                                       4

<PAGE>   51

respective properties, rights, interests, estates and privileges herein and
hereby granted or intended so to be granted.

         SECTION 3.02. SUCCESSORS AND ASSIGNS. All of the provisions hereof
shall inure to the benefit of and be binding upon the respective successors and
assigns of Assignor and Assignee. All references herein to either Assignor or
Assignee shall include their respective successors and assigns.

         SECTION 3.03. COUNTERPARTS. This Assignment is being executed in
several originals to be effective as of the Effective Date.

                                      ASSIGNOR:

                                      NEBRASKA PUBLIC GAS AGENCY

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

                                      ASSIGNEE:

                                      HUMPHREY-HILL, L.P.
                                      By Humphrey Oil Corp., General Partner

                                      -----------------------------------------
                                      Charles B. Humphrey, President

                                       5

<PAGE>   52

THE STATE OF______    )
                      ) ss.
COUNTY OF_________    )

         This instrument was acknowledged before me on __________, 2000 by
_______________, as _______________ for NEBRASKA PUBLIC GAS AGENCY, a body
corporate and politic under the laws of the State of Nebraska, on behalf of said
corporation.

                                                  -----------------------------
                                                  Notary Public

My Commission Expires:

------------------------------------

THE STATE OF________    )
                        ) ss.
COUNTY OF___________    )

         This instrument was acknowledged before me on __________, 2000 by
Charles B. Humphrey, as President of HUMPHREY OIL CORP., General Partner of
HUMPHREY-HILL, L.P. a Texas limited partnership, on behalf of said partnership.

                                                  -----------------------------
                                                  Notary Public

My Commission Expires:

------------------------------------

After recording, please return instrument to:

------------------------------------

------------------------------------

------------------------------------

------------------------------------

                                       6

<PAGE>   53

                                    EXHIBIT G

                         SELLER'S DELIVERIES AT CLOSING

1.       A certificate dated the Closing Date signed by the Secretary or an
         Assistant Secretary of Seller that Seller's Board of Directors has
         authorized the transaction contemplated by the Agreement and has
         authorized the executing officer or attorney in fact to execute all
         instruments contemplated by the transaction on behalf of Seller.

2.       A certificate dated the Closing Date signed by the President or a
         Vice-President certifying in such detail as Buyer may reasonably
         request as to the fulfillment of the conditions specified in Section
         10.02, Subsections (a) through (c).

3.       The opinion of Seller's counsel, Kutak Rock LLP or such other counsel
         designated by Seller as Purchaser may approve, dated the Closing Date
         in a form approved by Purchaser at least three days prior to the
         Closing Date, which approval shall not be unreasonably withheld.

4.       Letters-in-Lieu in a form approved by Seller at least three days prior
         to the Closing Date, executed by Seller.

<PAGE>   54

                                    EXHIBIT H

                        PURCHASER'S DELIVERIES AT CLOSING

1.       A certificate dated the Closing Date signed by the Secretary or an
         Assistant Secretary of Purchaser's General Partner that its Board of
         Directors has authorized the transaction contemplated by the Agreement
         and has authorized the executing officer or attorney in fact to execute
         all instruments contemplated by the transaction on behalf of the
         General Partner on behalf of Purchaser.

2.       A certificate dated the Closing Date signed by the President or a
         Vice-President of Purchaser's General Partner certifying in such detail
         as Seller may reasonably request as to the fulfillment of the
         conditions specified in Section 10.01, Subsections (a) through (c).

3.       The opinion of Purchaser's counsel, Mike Harrell or such other counsel
         designated by Purchaser as Seller may approve, dated the Closing Date
         in a form approved by Seller at least three days prior to the Closing
         Date, which approval shall not be unreasonably withheld.

<PAGE>   55

                                SCHEDULE 4.02(E)
                              LITIGATION AND CLAIMS

o    CASE #93-11958, 261ST COURT, TRAVIS COUNTY, TEXAS STYLED LADD PETROLEUM
     CORPORATION V. STATE OF TEXAS GENERAL LAND OFFICE AFFECTING STATE LEASES
     INCLUDED WITHIN THE GOMEZ SOUTH UNIT #1 (GOMEZ #1-D AND #1-A WELLS), THE
     FSOC - DIXEL GAS UNIT #2 (DIXEL #2 WELL), AND FSOC-LEON GAS UNIT (LEON #1
     WELL), PECOS COUNTY, TEXAS.

OTHER THAN THE ABOVE, NONE.

<PAGE>   56

                                SCHEDULE 4.02(F)
                                  ENCUMBRANCES

         NONE

<PAGE>   57

                                SCHEDULE 4.02(G)
                                      TAXES

         NONE

<PAGE>   58

                                SCHEDULE 4.02(H)
                                   VIOLATIONS

         NONE

<PAGE>   59

                                SCHEDULE 4.02(J)
                                    ROYALTIES

1.       UNDER COVER OF LETTER DATED OCTOBER 25, 1999, KUTAK ROCK, AS COUNSEL
         FOR NPGA, FORWARDED TO THE TEXAS GENERAL LAND OFFICE CHECK IN THE
         AMOUNT OF $8,766.84. THIS PAYMENT REPRESENTED ROYALTIES UNDERPAID TO
         THE STATE FOR REPORTING PERIODS SEPTEMBER, 1989 THROUGH AUGUST, 1993,
         UNDER LEASES #M-41697, M-51858 AND M-67014, AS DETERMINED BY LIMITED
         REVIEW CONDUCTED BY THE ROYALTY MANAGEMENT DIVISION OF THE TEXAS
         GENERAL LAND OFFICE. THIS PAYMENT LEFT PENDING PENALTIES IN THE AMOUNT
         OF $1,612.66 AND INTEREST IN THE AMOUNT OF $6,766.84, WHICH HE GLO WAS
         ASKED TO WAIVE. THERE HAS NOT BEEN FINAL DISPOSITION OF THIS REQUEST.

2.       UNDER COVER OF LETTER DATED FEBRUARY 25, 1999(SIC) (RECEIVED MARCH 3,
         2000), STYLED NOTICE OF UNDERPAYMENT ON STATE LEASE (M-41697, 51858,
         67014) NPGA WAS NOTIFIED OF AN UNDERPAYMENT OF ROYALTIES FOR THE
         REPORTING PERIODS SEPTEMBER, 1996 THROUGH AUGUST, 1998, UNDER LEASES
         #M-41697, M-51858 AND M-67014. THE TOTAL AMOUNT DUE FOR THIS REPORTED
         UNDERPAYMENT IS $37,817.24, BEING $28,891.64 IN ADDITIONAL ROYALTY,
         $3,300.83 IN PENALTY AND $5,624.77 IN INTEREST COMPUTED THROUGH MARCH
         25, 2000.

3.       STATE OF TEXAS GENERAL LAND OFFICE LEASES M-41697, M-51858, M-67014 AND
         M-39999 ARE INCLUDED IN LITIGATION BEING CASE #93-11958 IN THE 261ST
         COURT, TRAVIS COUNTY, TX, STYLED LADD PETROLEUM CORPORATION V. STATE OF
         TEXAS GENERAL LAND OFFICE. THE GENERAL LAND OFFICE HAS ADVISED THAT THE
         MAXIMUM EXPOSURE TO NPGA AND ASSIGNS IN REGARD TO THIS MATTER WOULD BE
         $281,000, INCLUDING PENALTIES AND INTEREST THROUGH JANUARY 31, 2000.

OTHER THAN THE ABOVE, NONE.

<PAGE>   60

                                SCHEDULE 4.02(K)
                              PERMITS AND LICENSES

         NONE

<PAGE>   61

                                SCHEDULE 4.02(L)
                               GOVERNMENTAL AUDITS

o        THERE ARE NO ONGOING OR PLANNED AUDITS. SEE SCHEDULE 4.02(J) REGARDING
         AUDITS PREVIOUSLY CONDUCTED BY THE STATE OF TEXAS GENERAL LAND OFFICE,
         ON WHICH ROYALTIES, AND OR PENALTIES AND INTEREST AMOUNTS ARE STILL
         OUTSTANDING.

<PAGE>   62

                                SCHEDULE 4.02(M)
                                  GAS BALANCES

              FOLLOWING ARE GAS IMBALANCES AS OF DECEMBER 31, 1999

<TABLE>
<CAPTION>
 WELL                                                   IMBALANCE IN MCF
 ----                                                   ----------------
<S>                                                     <C>
 DIXEL RESOURCES NO. 2                                            (2,004)

 GOMEZ SOUTH UNIT #1-A                                           (69,928)

 GOMEZ SOUTH UNIT #1-A                                            24,616

 GOMEZ SOUTH UNIT #2                                             (23,756)

 GOMEZ SOUTH UNIT 3A #1                                             (309)

 DIXEL RESOURCES UNIT #1                                          (5,056)

 FSOC-LEON #1                                                      1,097

 SABINE #1                                                             0
                                                            ------------

 TOTAL IMBALANCE AT 12/31/99                                     (75,340)
</TABLE>

<PAGE>   63

                                SCHEDULE 4.02(N)
                              ENVIRONMENTAL MATTERS

         NONE<PAGE>   1
                                                                   EXHIBIT 10.27

                                CREDIT AGREEMENT

                                      among

                               HUMPHREY-HILL, L.P.
                                  as Borrower,

                             BANK OF AMERICA, N.A.,
                             as Administrative Agent

                                       and

             The Financial Institutions Listed on Schedule 1 Hereto,
                                    as Banks

                                   $25,000,000

                                      dated

                                 March 24, 2000

                         Banc of America Securities LLC
                     as Sole Lead Arranger and Book Manager

<PAGE>   2

                                TABLE OF CONTENTS

<TABLE>
<S>           <C>                                                                                       <C>
                                    ARTICLE 1
                                  TERMS DEFINED
SECTION 1.1   Definitions................................................................................1
SECTION 1.2   Accounting Terms and Determinations.......................................................19
SECTION 1.3   Petroleum Terms...........................................................................19
SECTION 1.4   Money.....................................................................................19

                                    ARTICLE 2
                                   THE CREDIT
SECTION 2.1   Commitments...............................................................................20
SECTION 2.2   Notes.....................................................................................24
SECTION 2.3   Interest Rates; Payments..................................................................24
SECTION 2.4   Mandatory Prepayments During Borrowing Base Deficiency....................................26
SECTION 2.5   Mandatory Prepayments from Cash Flow......................................................27
SECTION 2.6   Voluntary Reduction of Commitments........................................................27
SECTION 2.7   Termination of Commitments; Final Maturity of Revolving Loan..............................27
SECTION 2.8   Unused Commitment Fee.....................................................................27
SECTION 2.9   Borrowing Base Increase Fee...............................................................28
SECTION 2.10  Letter of Credit Fee......................................................................28
SECTION 2.11  Agency and other Fees.....................................................................28
SECTION 2.12  Closing Fee...............................................................................28

                                    ARTICLE 3
                               GENERAL PROVISIONS
SECTION 3.1   Delivery and Endorsement of Notes.........................................................28
SECTION 3.2   General Provisions as to Payments.........................................................29

                                    ARTICLE 4
                             CHANGE IN CIRCUMSTANCES
SECTION 4.1   Increased Cost and Reduced Return.........................................................30
SECTION 4.2   Limitation on Types of Revolving Loans....................................................31
SECTION 4.3   Illegality................................................................................31
SECTION 4.4   Treatment of Affected Loans...............................................................32
SECTION 4.5   Compensation..............................................................................32
SECTION 4.6   Taxes.....................................................................................33
SECTION 4.7   Discretion of Banks as to Manner of Funding...............................................34

                                   ARTICLE 5
                                 BORROWING BASE
SECTION 5.1   Reserve Report; Proposed Borrowing Base...................................................35
</TABLE>

                                        i

<PAGE>   3

<TABLE>
<S>           <C>                                                                                       <C>
SECTION 5.2   Scheduled Redeterminations of the Borrowing Base; Procedures
              and Standards.............................................................................35
SECTION 5.3   Special Redetermination...................................................................36
SECTION 5.4   Quarterly Reduction.......................................................................36
SECTION 5.5   Borrowing Base Deficiency.................................................................36
SECTION 5.6   Initial Borrowing Base....................................................................36

                                    ARTICLE 6
                            COLLATERAL AND GUARANTEES
SECTION 6.1   Security..................................................................................36
SECTION 6.2   Guarantees................................................................................37
SECTION 6.3   Supporting Documents......................................................................37

                                    ARTICLE 7
                              CONDITIONS PRECEDENT
SECTION 7.1   Conditions to Initial Borrowing and Participation in Letter of Credit Exposure............38
SECTION 7.2   Conditions to Each Borrowing and each Letter of Credit....................................42
SECTION 7.3   Materiality of Conditions.................................................................42

                                    ARTICLE 8
                         REPRESENTATIONS AND WARRANTIES
SECTION 8.1   Existence and Power.......................................................................43
SECTION 8.2   Necessary Authorization; Contravention....................................................43
SECTION 8.3   Binding Effect............................................................................43
SECTION 8.4   Financial Information.....................................................................43
SECTION 8.5   Litigation................................................................................44
SECTION 8.6   ERISA.....................................................................................45
SECTION 8.7   Taxes and Filing of Tax Returns...........................................................45
SECTION 8.8   Ownership of Properties Generally.........................................................46
SECTION 8.9   Mineral Interests.........................................................................46
SECTION 8.10  Licenses, Permits, Etc....................................................................46
SECTION 8.11  Compliance with Law.......................................................................46
SECTION 8.12  Full Disclosure...........................................................................46
SECTION 8.13  Organizational Structure; Nature of Business..............................................47
SECTION 8.14  Environmental Matters.....................................................................47
SECTION 8.15  Burdensome Obligations....................................................................48
SECTION 8.16  Fiscal Year...............................................................................48
SECTION 8.17  No Default................................................................................48
SECTION 8.18  Government Regulation.....................................................................48
SECTION 8.19  Insider...................................................................................48
SECTION 8.20  Gas Balancing Agreements and Advance Payment Contracts....................................48
SECTION 8.21  Nebraska Acquisition Documents............................................................48
</TABLE>

                                       ii

<PAGE>   4

<TABLE>
<S>           <C>                                                                                       <C>
                                    ARTICLE 9
                              AFFIRMATIVE COVENANTS
SECTION 9.1   Information...............................................................................49
SECTION 9.2.  Business of Borrower......................................................................51
SECTION 9.3   Maintenance of Existence..................................................................51
SECTION 9.4   Title Data................................................................................51
SECTION 9.5   Right of Inspection.......................................................................52
SECTION 9.6   Maintenance of Insurance..................................................................52
SECTION 9.7   Payment of Taxes and Claims...............................................................52
SECTION 9.8   Compliance with Laws and Documents........................................................53
SECTION 9.9   Operation of Properties and Equipment.....................................................53
SECTION 9.10  Environmental Law Compliance..............................................................53
SECTION 9.11  ERISA Reporting Requirements..............................................................53
SECTION 9.12  Additional Documents......................................................................55
SECTION 9.13  Environmental Review......................................................................55

                                   ARTICLE 10
                               NEGATIVE COVENANTS
SECTION 10.1  Incurrence of Debt........................................................................55
SECTION 10.2  Distributions.............................................................................55
SECTION 10.3  Negative Pledge...........................................................................55
SECTION 10.4  Consolidations and Mergers................................................................56
SECTION 10.5  Asset Dispositions........................................................................56
SECTION 10.6  Amendments to Organizational Documents; Other Material Agreements.........................56
SECTION 10.7  Use of Proceeds...........................................................................56
SECTION 10.8  Investments...............................................................................56
SECTION 10.9  Transactions with Affiliates..............................................................56
SECTION 10.10 ERISA.....................................................................................57
SECTION 10.11 Hedge Transactions........................................................................57
SECTION 10.12 Fiscal Year...............................................................................57
SECTION 10.13 Change in Business........................................................................57
SECTION 10.14 Restricted Payments.......................................................................57

                                   ARTICLE 11
                               FINANCIAL COVENANTS
SECTION 11.1  Current Ratio of Borrower.................................................................57
SECTION 11.2  Maximum General and Administrative Expenses...............................................57
</TABLE>

                                               iii

<PAGE>   5

<TABLE>
<S>           <C>                                                                                       <C>
                                   ARTICLE 12
                                    DEFAULTS
SECTION 12.1  Events of Default.........................................................................58

                                   ARTICLE 13
                                     AGENTS
SECTION 13.1  Appointment, Powers, and Immunities.......................................................60
SECTION 13.2  Reliance by Agents........................................................................60
SECTION 13.3  Defaults..................................................................................61
SECTION 13.4  Rights as Bank............................................................................61
SECTION 13.5  Indemnification...........................................................................61
SECTION 13.6  Non-Reliance on Agents and Other Banks....................................................62
SECTION 13.7  Resignation of Agents.....................................................................62

                                   ARTICLE 14
                                  MISCELLANEOUS
SECTION 14.1  Notices...................................................................................62
SECTION 14.2  No Waivers................................................................................63
SECTION 14.3  Expenses; Indemnification.................................................................63
SECTION 14.4  Right of Set-off; Adjustments.............................................................64
SECTION 14.5  Amendments and Waivers....................................................................64
SECTION 14.6  Survival..................................................................................65
SECTION 14.7  Limitation on Interest....................................................................65
SECTION 14.8  Invalid Provisions........................................................................65
SECTION 14.9  Waiver of Consumer Credit Laws............................................................66
SECTION 14.10 Assignments and Participations............................................................66
SECTION 14.11 TEXAS LAW.................................................................................68
SECTION 14.12 Consent to Jurisdiction; Waiver of Immunities.............................................68
SECTION 14.13 Counterparts; Effectiveness...............................................................68
SECTION 14.14 No Third Party Beneficiaries..............................................................69
SECTION 14.15 COMPLETE AGREEMENT........................................................................69
SECTION 14.16 WAIVER OF JURY TRIAL......................................................................69
</TABLE>

                                       iv

<PAGE>   6

                                    EXHIBITS

EXHIBIT A      FORM OF FACILITY GUARANTEES
EXHIBIT B      FORM OF NOTE
EXHIBIT C      FORM OF OPERATING AGREEMENT
EXHIBIT D      FORM OF SECURITY AGREEMENT
EXHIBIT E      FORM OF REQUEST FOR BORROWING
EXHIBIT F      FORM OF REQUEST FOR LETTER OF CREDIT
EXHIBIT G      FORM OF CONTINUATION AND CONVERSION NOTICE
EXHIBIT H      FORM OF CERTIFICATE OF OWNERSHIP INTERESTS
EXHIBIT I-1    FORM OF CERTIFICATE OF FINANCIAL OFFICER OF EXCO
EXHIBIT I-2    FORM OF CERTIFICATE OF FINANCIAL OFFICER OF BORROWER
EXHIBIT J      FORM OF ASSIGNMENT AND ACCEPTANCE AGREEMENT
EXHIBIT K      FORM OF PLEDGE AGREEMENT

                                    SCHEDULES

SCHEDULE 1     FINANCIAL INSTITUTIONS
SCHEDULE 2     LITIGATION
SCHEDULE 3     ORGANIZATION STRUCTURE; NATURE OF BUSINESS

                                        v

<PAGE>   7

                                CREDIT AGREEMENT

         THIS CREDIT AGREEMENT (this "Agreement") is entered into as of the 24th
day of March, 2000, among HUMPHREY-HILL, L.P., a Texas limited partnership
("Borrower"), Bank of America, N.A., as Administrative Agent ("Administrative
Agent"), and the financial institutions listed on Schedule 1 hereto as Banks
(individually a "Bank" and collectively "Banks").

                              W I T N E S S E T H:

         WHEREAS, Borrower has requested that Banks provide Borrower with a
revolving credit facility, and Banks are willing to provide such facility on the
terms and subject to the conditions hereinafter set forth; and

         WHEREAS, pursuant to Article 13 of this Agreement, Bank of America,
N.A. has been appointed Administrative Agent for Banks hereunder; and

         WHEREAS, Banc of America Securities LLC ("BAS") has been appointed Sole
Lead Arranger and Book Manager for the credit facility provided hereunder.

         NOW, THEREFORE, in consideration of the premises, the representations,
warranties, covenants and agreements contained herein, and other good and
valuable consideration, the receipt and adequacy of which are hereby
acknowledged, Borrower, Administrative Agent and Banks agree as follows:

                                    ARTICLE 1
                                  TERMS DEFINED

         SECTION 1.1 Definitions. The following terms, as used herein, have the
following meanings:

         "Adjusted Eurodollar Rate" means, for any Eurodollar Loan for any
Interest Period therefor, the rate per annum (rounded upwards, if necessary, to
the nearest 1/100 of 1%) determined by Administrative Agent to be equal to the
quotient obtained by dividing (a) the Eurodollar Rate for such Eurodollar Loan
for such Interest Period by (b) 1.00 minus the Reserve Requirement for such
Eurodollar Loan for such Interest Period.

         "Administrative Agent" means Bank of America, N.A. in its capacity as
Administrative Agent for Banks hereunder or any successor thereto.

         "Advance Payment Contract" means any contract whereby Borrower or any
Subsidiary of Borrower either (a) receives or becomes entitled to receive
(either directly or indirectly) any payment (an "Advance Payment") to be applied
toward payment of the purchase price of Hydrocarbons

                                        1

<PAGE>   8

produced or to be produced from Mineral Interests owned by Borrower or any
Subsidiary of Borrower and which Advance Payment is paid or to be paid in
advance of actual delivery of such production to or for the account of the
purchaser regardless of such production, or (b) grants an option or right of
refusal to the purchaser to take delivery of such production in lieu of payment,
and, in either of the foregoing instances, the Advance Payment is, or is to be,
applied as payment in full for such production when sold and delivered or is, or
is to be, applied as payment for a portion only of the purchase price thereof or
of a percentage or share of such production; provided that inclusion of the
standard "take or pay" provision in any gas sales or purchase contract or any
other similar contract shall not, in and of itself, constitute such contract as
an Advance Payment Contract for the purposes hereof.

         "Affiliate" means, as to any Person, any Subsidiary of such Person, or
any other Person which, directly or indirectly, controls, is controlled by, or
is under common control with, such Person and, with respect to Borrower or any
of its Subsidiaries, means any director or executive officer of Borrower or any
of its Subsidiaries and any Person who holds five percent (5%) or more of the
voting stock of Borrower or any of its Subsidiaries. For the purposes of this
definition, "control" (including, with correlative meanings, the terms
"controlled by" and "under common control with"), as used with respect to any
Person, shall mean the possession, directly or indirectly, of the power to
direct or cause the direction of the management and policies of such Person,
whether through the ownership of voting securities or partnership interests, or
by contract or otherwise.

         "Agent" means Administrative Agent, Sole Lead Arranger and Book
Manager, individually, and "Agents" means Administrative Agent, Sole Lead
Arranger and Book Manager, collectively.

         "Agreement" means this Agreement as the same may hereafter be modified,
amended or supplemented from time to time.

         "Applicable Environmental Law" means any Law, statute, ordinance, rule,
regulation, order or determination of any Tribunal or any board of fire
underwriters (or other body exercising similar functions), affecting any real or
personal property owned, operated or leased by Borrower or any of its
Subsidiaries or any other operation of Borrower or any of its Subsidiaries in
any way pertaining to health, safety or the environment, including, without
limitation, all applicable zoning ordinances and building codes, flood disaster
Laws and health, safety and environmental Laws and regulations, and further
including, without limitation, (a) the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980, as amended by the Superfund Amendments
and Reauthorization Act of 1986 (as amended from time to time, herein referred
to as "CERCLA"), (b) the Resource Conservation and Recovery Act of 1976, as
amended by the Used Oil Recycling Act of 1980, the Solid Waste Recovery Act of
1976, as amended by the Solid Waste Disposal Act of 1980, and the Hazardous and
Solid Waste Amendments of 1984 (as amended from time to time, herein referred to
as "RCRA"), (c) the Safe Drinking Water Act, as amended, (d) the Toxic
Substances Control Act, as amended, (e) the Clean Air Act, as amended, (f) the
Occupational Safety and Health Act of 1970, as amended, (g) the Laws, rules and
regulations of any state having jurisdiction over any real or personal property
owned, operated or leased by Borrower or any of its

                                        2

<PAGE>   9

Subsidiaries or any other operation of Borrower or any of its Subsidiaries which
relates to health, safety or the environment, as each may be amended from time
to time, and (h) any federal, state or municipal Laws, ordinances or regulations
which may now or hereafter require removal of asbestos or other hazardous wastes
or impose any liability related to asbestos or other hazardous wastes. The terms
"hazardous substance", "petroleum", "release" and "threatened release" have the
meanings specified in CERCLA, and the terms "solid waste" and "disposal" (or
"disposed") have the meanings specified in RCRA; provided, however, in the event
either CERCLA or RCRA is amended so as to broaden the meaning of any term
defined thereby, such broader meaning shall apply subsequent to the effective
date of such amendment with respect to all provisions of this Agreement; and
provided further that, to the extent the Laws of the state in which any real or
personal property owned, operated or leased by Borrower or any of its
Subsidiaries is located establish a meaning for "hazardous substance",
"petroleum", "release", "solid waste" or "disposal" which is broader than that
specified in either CERCLA or RCRA, such broader meaning shall apply in so far
as such broader meaning is applicable to the real or personal property owned,
operated or leased by Borrower or any of its Subsidiaries and located in such
state.

         "Applicable Lending Office" means, for each Bank and for each Type of
Revolving Loan, the Domestic Lending Office or Eurodollar Lending Office of such
Bank (or of an Affiliate of such Bank) designated for such Type of Revolving
Loan set forth on Schedule 1 hereto or such other office of such Bank (or an
Affiliate of such Bank) as such Bank may from time to time specify to
Administrative Agent and Borrower by written notice in accordance with the terms
hereof as the office by which its Revolving Loans of such Type are to be made
and maintained.

         "Applicable Margin" means, on any date, with respect to each Eurodollar
Loan, an amount determined by reference to the ratio of Outstanding Credit to
the Borrowing Base on such date in accordance with the table below:

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------
             Ratio of Outstanding                              Applicable Margin for
           Credit to Borrowing Base                              Eurodollar Loans
------------------------------------------------------------------------------------------------
<S>                                                           <C>
                   <.75 to 1                                           1.50%
------------------------------------------------------------------------------------------------
                  >=.75 to 1                                           1.75%
------------------------------------------------------------------------------------------------
</TABLE>

         "Approved Petroleum Engineer" means Lee Keeling and Associates, Inc. or
any other reputable firm of independent petroleum engineers as shall be selected
by Borrower and approved by Required Banks, such approval not to be unreasonably
withheld.

         "Assignment and Acceptance Agreement" has the meaning given such term
in Section 14.10(a).

         "Authorized Officer" means, as to any Person, its Chief Executive
Officer, its President, its Chief Financial Officer, any of its Vice Presidents,
its Treasurer or its corporate Secretary.

                                        3

<PAGE>   10

         "Availability" means, as of any date, the remainder of (a) the
Borrowing Base in effect on such date, minus (b) the Outstanding Credit on such
date.

         "Bank" means any financial institution reflected on Schedule 1 hereto
as having a Commitment and its successors and permitted Eligible Assignees, and
"Banks" shall mean all Banks.

         "Bank of America" means Bank of America, N.A., a national banking
association.

         "Base Rate" means, the floating rate of interest established from time
to time by Administrative Agent as its "prime rate" of interest, which rate may
not be the lowest rate of interest charged by Administrative Agent, each change
in the Base Rate to become effective without notice to Borrower on the effective
date of each such change.

         "Base Rate Loan" means the portion of the principal of the Revolving
Loan bearing interest with reference to the Base Rate.

         "Book Manager" means Banc of America Securities LLC in its capacity as
Book Manager for the credit facility provided hereunder or any successor
thereto.

         "Borrower" means Humphrey-Hill, L.P., a Texas limited partnership.

         "Borrowing" means any disbursement to Borrower under, or to satisfy the
obligations of Borrower or any of its Subsidiaries under, any of the Loan
Papers. Any Borrowing of Base Rate Loans is referred to herein as a "Base Rate
Borrowing," and any Borrowing of Eurodollar Loans is referred to herein as a
"Eurodollar Borrowing."

         "Borrowing Base" means the loan value attributable to certain of
Borrower's Mineral Interests as determined in accordance with Article 5 hereof.

         "Borrowing Base Deficiency" means, as of any date, the amount, if any,
by which the Outstanding Credit on such date exceeds the Borrowing Base in
effect on such date; provided, that, for purposes of determining the existence
and amount of any Borrowing Base Deficiency, Letter of Credit Exposure will not
be deemed to be outstanding to the extent it is secured by cash in the manner
contemplated by Section 2.1(b).

         "Borrowing Base Properties" means all Mineral Interests evaluated by
Banks for purposes of establishing the Borrowing Base. The Borrowing Base
Properties on the date hereof constitute all of the Mineral Interests described
in the Initial Reserve Report.

         "Borrowing Date" means the Eurodollar Business Day or the Domestic
Business Day, as the case may be, upon which the proceeds of any Borrowing are
made available to Borrower or to satisfy any obligation of Borrower or any of
its Subsidiaries.

                                        4

<PAGE>   11

         "Change of Control" means the occurrence of (a) any event or
circumstance which, for any reason (including by operation of law), results in
any of (i) Taurus ceasing to own on a fully diluted basis fifty percent (50%) of
the limited partnership interests in Borrower free and clear of all Liens (ii)
EXCO ceasing to own on a fully diluted basis one hundred percent (100%) of the
general partnership interests in Borrower free and clear of all Liens, (b) an
EXCO Change of Control, or (c) a Taurus Change of Control.

         "Closing Date" means March 24, 2000.

         "Code" means the Internal Revenue Code of 1986, as amended.

         "Commitment" means, with respect to any Bank, the commitment of such
Bank to lend its Commitment Percentage of the Total Commitment to Borrower
pursuant to Section 2.1 hereof. The amount of each Bank's Commitment is
initially the amount set forth opposite such Bank's name on Schedule 1 hereto,
as such Commitment may be terminated or reduced from time to time in accordance
with the provisions hereof; provided, that, after giving effect to any
Assignment and Acceptance Agreement, the Commitment of each Bank shall be the
amount set forth in the Register maintained by Administrative Agent pursuant to
Section 14.10(b).

         "Commitment Percentage" means, with respect to each Bank, initially,
the Commitment Percentage for such Bank set forth on Schedule 1 hereto;
provided, that, after giving effect to any Assignment and Acceptance Agreement,
the Commitment Percentage of each Bank shall be the amount set forth in the
Register maintained by Administrative Agent pursuant to Section 14.10(b).

         "Consolidated Current Assets" means, for any Person at any time, the
current assets of such Person and its Consolidated Subsidiaries at such time.

         "Consolidated Current Liabilities" means, for any Person at any time,
the current liabilities of such Person and its Consolidated Subsidiaries at such
time.

         "Consolidated Subsidiary" or "Consolidated Subsidiaries" means, for any
Person, any Subsidiary or other entity the accounts of which would be
consolidated with those of such Person in its consolidated financial statements.

         "Continue", "Continuation", and "Continued" shall refer to the
continuation pursuant to Section 2.3(c) hereof of a Eurodollar Loan from one
Interest Period to the next Interest Period.

         "Convert", "Conversion", and "Converted" shall refer to a conversion
pursuant to Section 2.3(c) hereof of one Type of Revolving Loan into another
Type of Revolving Loan.

         "Credit Parties" means Borrower, each Subsidiary of Borrower and EXCO,
collectively, and "Credit Party" means any such party.

                                        5

<PAGE>   12

         "Debt" means, for any Person at any time, without duplication, (a) all
obligations of such Person for borrowed money, (b) all obligations of such
Person evidenced by bonds, debentures, notes or other similar instruments, (c)
all other indebtedness (including capitalized lease obligations, other than
usual and customary oil and gas leases) of such Person on which interest charges
are customarily paid or accrued, (d) all Guarantees by such Person, (e) the
unfunded or unreimbursed portion of all letters of credit issued for the account
of such Person, (f) any amount owed by such Person representing the deferred
purchase price of property or services other than accounts payable incurred in
the ordinary course of business and in accordance with customary trade terms and
which have not been outstanding for more than ninety (90) days past the invoice
date, (g) all obligations of such Person secured by a Lien on any property or
asset owned or held by that Person regardless of whether the indebtedness
secured thereby shall have been assumed by that Person or is non-recourse to
the credit of that Person, and (h) all liability of such Person as a general
partner of a partnership for obligations of such partnership of the nature
described in (a) through (g) preceding.

         "Dedication Percentage" means (a) 75% during any Fiscal Quarter if the
daily average NYMEX near month price for natural gas (the "Average Index Price")
for the immediately preceding Fiscal Quarter was $3.00 per mmbtu or less, and
(b) 60% during any Fiscal Quarter if the Average Index Price for the immediately
preceding Fiscal Quarter was $3.00 or greater.

         "Default" means any condition or event which constitutes an Event of
Default or which with the giving of notice, lapse of time or both would, unless
cured or waived, become an Event of Default.

         "Distribution" by any Person, means (a) with respect to any stock
issued by such Person or any partnership, joint venture, limited liability
company, membership or other interest of such Person, the retirement,
redemption, purchase, or other acquisition for value of any such stock or
partnership, joint venture, limited liability company, membership or other
interest, (b) the declaration or payment of any dividend or other distribution
on or with respect to any stock, partnership, joint venture, limited liability
company, membership or other interest of any Person, (c) any other payment by
such Person with respect to such stock, partnership, joint venture, limited
liability company, membership or other interest of such Person, and (d) the
payment of any management fee, consulting fee, overhead reimbursement or other
fee or payment of any kind to any holder of any stock, partnership, joint
venture, limited liability company, membership or other interest of such Person
or to any Affiliate of such holder; provided, that "Distribution" will not
include payments made by Borrower to EXCO under the Operating Agreement

         "Dollars" means the lawful currency of the United States of America.

         "Domestic Business Day" means any day except a Saturday, Sunday or
other day on which national banks in Dallas, Texas, are authorized by Law to
close.

         "Domestic Lending Office" means, as to each Bank, its office located at
its address identified on Schedule 1 hereto as its Domestic Lending Office or
such other office as such Bank may hereafter designate as its Domestic Lending
Office by notice to Borrower and Administrative Agent.

                                        6

<PAGE>   13

         "Eligible Assignee" means (i) a Bank, (ii) an Affiliate of a Bank, and
(iii) any other Person approved by Administrative Agent and, unless an Event of
Default has occurred and is continuing at the time any assignment is effected in
accordance with Section 14.10, such approval not to be unreasonably withheld or
delayed by Borrower and such approval to be deemed given by Borrower if no
objection is received by the assigning Bank and Administrative Agent from
Borrower within two (2) Domestic Business Days after notice of such proposed
assignment has been provided by the assigning Bank to Borrower; provided,
however, that neither Borrower nor an Affiliate of Borrower shall qualify as an
Eligible Assignee.

         "Environmental Complaint" means any complaint, summons, citation,
notice, directive, order, claim, litigation, investigation, proceeding,
judgment, letter or other communication from any federal, state or municipal
authority or any other party against Borrower or any of its Subsidiaries
involving (a) a Hazardous Discharge from, onto or about any real property owned,
leased or operated at any time by Borrower or any of its Subsidiaries, (b) a
Hazardous Discharge caused, in whole or in part, by Borrower or any of its
Subsidiaries or by any Person acting on behalf of or at the instruction of
Borrower or any of its Subsidiaries, or (c) any violation of any Applicable
Environmental Law by Borrower or any of its Subsidiaries.

         "Environmental Liability" means any liability, loss, fine, penalty,
charge, Lien, damage, cost, or expense of any kind that results directly or
indirectly, in whole or in part (a) from the violation of any Applicable
Environmental Law, (b) from the release or threatened release of any Hazardous
Substance, (c) from removal, remediation, or other actions in response to the
release or threatened release of any Hazardous Substance, (d) from actual or
threatened damages to natural resources, (e) from the imposition of injunctive
relief or other orders, (f) from personal injury, death, or property damage
which occurs as a result of Borrower's or any of its Subsidiaries' use, storage,
handling, or the release or threatened release of a Hazardous Substance, or (g)
from any environmental investigation performed at, on, or for any real property
owned by Borrower or any of its Subsidiaries.

         "ERISA" means the Employee Retirement Income Security Act of 1974, as
amended, and the rulings and regulations issued thereunder as from time to time
in effect.

         "ERISA Affiliate" means any Person that for purposes of Title IV of
ERISA is under common control with Borrower as determined under Section 414(b),
(c), (m) or (o) of the Internal Revenue Code of 1986, as amended, and the
regulations and rulings issued thereunder.

         "ERISA Event" means, with respect to Borrower and any ERISA Affiliate,
(a) a "reportable event" as defined in section 4043 of ERISA (other than a
reportable event not subject to the provision for thirty (30) days notice to the
PBGC under regulations issued under section 4043 of ERISA), (b) the withdrawal
of Borrower or any ERISA Affiliate from a Plan during a plan year in which it
was a "substantial employer" as defined in section 4001(a)(2) of ERISA, (c) the
filing of a notice of intent to terminate a Plan under section 4041(c) of ERISA,
(d) the institution of proceedings to terminate a Plan by the PBGC, (e) the
failure to make required contributions which could result in the imposition of a
Lien under section 412 of the Internal Revenue Code of 1986, as amended or
section

                                        7

<PAGE>   14

302 of ERISA, or (f) any other event or condition which might reasonably be
expected to constitute grounds under section 4042 of ERISA for the termination
of, or the appointment of a trustee to administer, any Plan or the imposition of
any liability under Title IV of ERISA other than PBGC premiums due but not
delinquent under Section 4007 of ERISA.

         "Eurodollar Business Day" means any Domestic Business Day on which
commercial banks are open for international business (including dealings in
dollar deposits) in the applicable eurodollar interbank market.

         "Eurodollar Lending Office" means, as to each Bank, its office, branch
or Affiliate located at its address identified on Schedule 1 hereto as its
Eurodollar Lending Office or such other office, branch or Affiliate of such Bank
as it may hereafter designate as its Eurodollar Lending Office by notice to
Borrower and Administrative Agent.

         "Eurodollar Loans" means Revolving Loans that bear interest at rates
based upon the Adjusted Eurodollar Rate.

         "Eurodollar Rate" means, for any Eurodollar Loan for any Interest
Period therefor, the rate per annum (rounded upwards, if necessary, to the
nearest 1/100 of 1%) appearing on Telerate Page 3750 (or any successor page) as
the London interbank offered rate for deposits in Dollars at approximately 11:00
a.m. (London time) two (2) Eurodollar Business Days prior to the first day of
such Interest Period for a term comparable to such Interest Period. If for any
reason such rate is not available, the term "Eurodollar Rate" shall mean, for
any Eurodollar Loan for any Interest Period therefor, the rate per annum
(rounded upwards, if necessary, to the nearest 1/100 of 1%) appearing on Reuters
Screen LIBO Page as the London interbank offered rate for deposits in Dollars at
approximately 11:00 a.m. (London time) two (2) Eurodollar Business Days prior to
the first day of such Interest Period for a term comparable to such Interest
Period; provided, however, if more than one rate is specified on Reuters Screen
LIBO Page, the applicable rate shall be the arithmetic mean of all such rates
(rounded upwards, if necessary, to the nearest 1/100 of 1%).

         "Events of Default" has the meaning set forth in Section 12.1.

         "EXCO" means EXCO Resources, Inc., a Texas corporation.

         "EXCO Change of Control" will be deemed to have occurred if (a) as of
any date, more than fifty percent (50%) of the Persons comprising the Board of
Directors of EXCO were not members of the Board of Directors of EXCO one year
prior to such date, or (b) Douglas H. Miller shall cease, for any reason, to be
actively employed on a full time basis as the Chief Executive Officer of EXCO.

         "Exhibit" refers to an exhibit attached to this Agreement and
incorporated herein by reference, unless specifically provided otherwise.

                                        8

<PAGE>   15

         "Facility Guarantees" means Guarantees substantially in the form of
Exhibit A to be executed by EXCO and each Subsidiary of Borrower in favor of
Administrative Agent for the ratable benefit of the Banks pursuant to which each
EXCO and each Subsidiary of Borrower jointly and severally guarantees payment
and performance in full of the Obligations.

         "Federal Funds Rate" means, for any day, the rate per annum (rounded
upwards, if necessary, to the nearest 1/100 of 1%) equal to the weighted average
of the rates on overnight Federal funds transactions with members of the Federal
Reserve System arranged by Federal funds brokers on such day, as published by
the Federal Reserve Bank of New York on the Domestic Business Day next
succeeding such day; provided, that, (a) if such day is not a Domestic Business
Day, the Federal Funds Rate for such day shall be such rate on such transactions
on the next preceding Domestic Business Day as so published on the next
succeeding Domestic Business Day, and (b) if no such rate is so published on
such next succeeding Domestic Business Day, the Federal Funds Rate for such day
shall be the average rate charged to Administrative Agent (in its individual
capacity) on such day on such transactions as determined by Administrative
Agent.

         "Financial Officer" of any Person means its Chief Financial Officer;
provided, that if no Person serves in such capacity, "Financial Officer" shall
mean the highest ranking executive officer of such Person with responsibility
for accounting, financial reporting, cash management and similar functions.

         "Fiscal Quarter" means the three (3) month periods ending on March 31,
June 30, September 30 and December 31 of each Fiscal Year.

         "Fiscal Year" means a twelve (12) month period ending December 31.

         "GAAP" means those generally accepted accounting principles and
practices which are recognized as such by the American Institute of Certified
Public Accountants acting through its Accounting Principles Board or by the
Financial Accounting Standards Board or through other appropriate boards or
committees thereof and which are consistently applied for all periods after the
date hereof so as to properly reflect the financial condition, and the results
of operations and changes in financial position, of a Person and its
Consolidated Subsidiaries, except that any accounting principle or practice
required to be changed by the said Accounting Principles Board or Financial
Accounting Standards Board (or other appropriate board or committee of the said
Boards) in order to continue as a generally accepted accounting principle or
practice may be so changed.

         "Gas Balancing Agreement" means any agreement or arrangement whereby
Borrower or any of its Subsidiaries, or any other party having an interest in
any Hydrocarbons to be produced from Mineral Interests in which Borrower or any
of its Subsidiaries owns an interest, has a right to take more than its
proportionate share of production therefrom.

         "Governmental Authority" means any court or governmental department,
commission, board, bureau, agency, or instrumentality of any nation or of any
province, state, commonwealth, nation, territory, possession, county, parish, or
municipality, whether now or hereafter constituted or existing.

                                        9

<PAGE>   16

         "Guarantee" by any Person means any obligation, contingent or
otherwise, of such Person directly or indirectly guaranteeing any Debt or other
obligation of any other Person and, without limiting the generality of the
foregoing, any obligation, direct or indirect, contingent or otherwise, of such
Person (a) to purchase or pay (or advance or supply funds for the purchase or
payment of) such Debt or other obligation (whether arising by virtue of
partnership arrangements, by agreement to keep-well, to purchase assets, goods,
securities or services, to take-or-pay, or to maintain financial statement
conditions, by "comfort letter" or other similar undertaking of support or
otherwise), or (b) entered into for the purpose of assuring in any other manner
the obligee of such Debt or other obligation of the payment thereof or to
protect such obligee against loss in respect thereof (in whole or in part),
provided that the term Guarantee shall not include endorsements for collection
or deposit in the ordinary course of business.

         "Hazardous Discharge" means any releasing, spilling, leaking, pumping,
pouring, emitting, emptying, discharging, injecting, escaping, leaching,
disposing or dumping of any Hazardous Substance from or onto any real property
owned, leased or operated at any time by Borrower or any of its Subsidiaries or
any real property owned, leased or operated by any other party.

         "Hazardous Substance" means any pollutant, toxic substance, hazardous
waste, compound, element or chemical that is defined as hazardous, toxic,
noxious, dangerous or infectious pursuant to any Applicable Environmental Law or
which is otherwise regulated by any Applicable Environmental Law or is required
to be investigated and/or remediated by or pursuant to any Applicable
Environmental Law.

         "Hedge Transaction" means any commodity, interest rate, currency or
other swap, option, collar, futures contract or other contract pursuant to which
a Person hedges risks related to commodity prices, interest rates, currency
exchange rates, securities prices or financial market conditions. Hedge
Transactions expressly includes Oil and Gas Hedge Transactions.

         "Hill" means J.M. Hill.

         "Humphrey" means Charles Humphrey.

         "Humphrey Oil" means Humphrey Oil Corporation, a Texas corporation.

         "Hydrocarbons" means oil, gas, casinghead gas, drip gasolines, natural
gasoline, condensate, distillate, and all other liquid and gaseous hydrocarbons
produced or to be produced in conjunction therewith, and all products,
by-products and all other substances derived therefrom or the processing
thereof, and all other minerals and substances, including, but not limited to,
sulphur, lignite, coal, uranium, thorium, iron, geothermal steam, water, carbon
dioxide, helium, and any and all other

                                       10

<PAGE>   17

minerals, ores, or substances of value, and the products and proceeds therefrom,
including, without limitation, all gas resulting from the in-situ combustion of
coal or lignite.

         "Incremental Availability" means the incremental increase in
Availability resulting from any increase in the Borrowing Base hereunder.

         "Initial Borrowing Base" means a Borrowing Base in the amount of
$7,000,000, which shall be in effect during the period commencing on the Closing
Date and continuing until the first Redetermination after the Closing Date.

         "Initial Reserve Report" means an engineering analysis of the Nebraska
Properties, prepared by EXCO Resources, Inc. dated as of January 1, 2000, a copy
of which has been provided to Administrative Agent and each Bank.

         "Interest Period" means, with respect to each Eurodollar Borrowing, the
period commencing on the date of such Borrowing and ending one (1), two (2),
three (3), and, if available to all Banks, six (6) months thereafter, as
Borrower may elect in the applicable Request for Borrowing; provided that:

                  (i) any Interest Period which would otherwise end on a day
                  which is not a Eurodollar Business Day shall be extended to
                  the next succeeding Eurodollar Business Day unless such
                  Eurodollar Business Day falls in another calendar month, in
                  which case such Interest Period shall end on the next
                  preceding Eurodollar Business Day;

                  (ii) any Interest Period which begins on the last Eurodollar
                  Business Day of a calendar month (or on a day for which there
                  is no numerically corresponding day in the calendar month at
                  the end of such Interest Period) shall, subject to clause
                  (iii) below, end on the last Eurodollar Business Day of a
                  calendar month;

                  (iii) if any Interest Period includes a date on which any
                  payment of principal of any Eurodollar Loan is required to be
                  made hereunder, but does not end on such date, then (A) the
                  principal amount of each Eurodollar Loan required to be repaid
                  on such date shall have an Interest Period ending on such
                  date, and (B) the remainder of each such Eurodollar Loan shall
                  have an Interest Period determined as set forth above; and

                  (iv) no Interest Period applicable to a Eurodollar Loan shall
                  extend past the Termination Date.

         "Investment" means, with respect to any Person, any loan, advance,
extension of credit, capital contribution to, investment in or purchase of the
stock or other securities of, or interests in, any other Person; provided, that
"Investment" shall not include current customer and trade accounts which are
payable in accordance with customary trade terms.

                                       11

<PAGE>   18

         "Laws" means all applicable statutes, laws, ordinances, regulations,
orders, writs, injunctions, or decrees of any state, commonwealth, nation,
territory, possession, county, township, parish, municipality or Governmental
Authority.

         "Letters of Credit" means letters of credit issued for the account of
Borrower pursuant to Section 2.1(b).

         "Letter of Credit Exposure" of any Bank means such Bank's aggregate
participation in the unfunded portion and the funded but unreimbursed portion of
Letters of Credit outstanding at any time.

         "Lien" means, with respect to any asset, any mortgage, lien, pledge,
charge, financing statement, security interest or encumbrance of any kind in
respect of such asset. For the purposes of this Agreement, Borrower and its
Subsidiaries shall be deemed to own subject to a Lien any asset which is
acquired or held subject to the interest of a vendor or lessor under any
conditional sale agreement, capital lease or other title retention agreement
relating to such asset.

         "Loan Papers" means this Agreement, the Notes, the Facility Guarantees,
each Security Agreement, all Mortgages now or at any time hereafter delivered
pursuant to Section 6.1, and all other certificates, documents or instruments
delivered in connection with this Agreement, as the foregoing may be amended
from time to time.

         "Margin Regulations" means Regulations G, T, U and X of the Board of
Governors of the Federal Reserve System, as in effect from time to time.

         "Margin Stock" means "margin stock" as defined in Regulation U.

         "Material Adverse Change" means any circumstance or event that has had
or would reasonably be expected to have (a) a material and adverse effect on the
financial condition, business operations, prospects, properties or assets of any
Credit Party, including, without limitation, any circumstances or event that has
had, or would reasonably be expected to have a material adverse effect on the
Nebraska Properties, (b) an adverse effect on (i) the validity and
enforceability of any Loan Paper, or (ii) the perfection or priority of any Lien
purported to be created thereby, or (c) a material adverse effect on the right
or ability of any Credit Party to fully, completely and timely pay and perform
its obligations under the Loan Papers.

         "Material Agreement" means any material written or oral agreement,
contract, commitment, or understanding to which a Person is a party, by which
such Person is directly or indirectly bound, or to which any assets of such
Person may be subject, which involves the payment of $50,000 or more in any
Fiscal Year or goods or services with a value in any Fiscal Year of $50,000 or
more and is not cancelable by such Person upon notice of thirty (30) days or
less without liability for further payment other than nominal penalty.

                                       12

<PAGE>   19

         "Material Gas Imbalance" means, with respect to all Gas Balancing
Agreements to which Borrower or any of its Subsidiaries is a party or by which
any Mineral Interest owned by Borrower or any of its Subsidiaries is bound, a
net gas imbalance to Borrower or any of its Subsidiaries in excess of $250,000.

         "Maximum Lawful Rate" means, for each Bank, the maximum rate (or, if
the context so permits or requires, an amount calculated at such rate) of
interest which, at the time in question would not cause the interest charged on
the portion of the Revolving Loans owed to such Bank at such time to exceed the
maximum amount which such Bank would be allowed to contract for, charge, take,
reserve, or receive under applicable Laws after taking into account, to the
extent required by applicable Laws, any and all relevant payments or charges
under the Loan Papers. To the extent the Laws of the State of Texas are
applicable for purposes of determining the "Maximum Lawful Rate," such term
shall mean the "interest rate ceiling" from time to time in effect under Chapter
1D of the Texas Credit Title, Revised Civil Statutes of Texas, 1925, as amended,
substituted for or restated, or, if permitted by applicable Law and effective
upon the giving of the notices required by such Chapter 1D (or effective upon
any other date otherwise specified by applicable Law), the "quarterly ceiling"
or "annualized ceiling" from time to time in effect under such Chapter 1D,
whichever Administrative Agent (with the approval of Required Banks) shall elect
to substitute for the "interest rate ceiling," and vice versa, each such
substitution to have the effect provided in such Chapter 1D, and Administrative
Agent (with the approval of Required Banks) shall be entitled to make such
election from time to time and one or more times and, without notice to
Borrower, to leave any such substitute rate in effect for subsequent periods in
accordance with such Chapter 1D.

         "Mineral Interests" means rights, estates, titles, and interests in and
to oil and gas leases and any oil and gas interests, royalty and overriding
royalty interest, production payment, net profits interests, oil and gas fee
interests, and other rights therein, including, without limitation, any
reversionary or carried interests relating to the foregoing, together with
rights, titles, and interests created by or arising under the terms of any
unitization, communization, and pooling agreements or arrangements, and all
properties, rights and interests covered thereby, whether arising by contract,
by order, or by operation of Laws, which now or hereafter include all or any
part of the foregoing.

         "Monthly Date" means the last day of each calendar month.

         "Mortgages" means all mortgages, deeds of trusts, security agreements,
pledge agreements, collateral mortgages, collateral chattel mortgages, financing
statements and other documents, instruments and agreements evidencing, creating,
perfecting or otherwise establishing the Liens on Mineral Interests required by
Section 6.1 hereof. All Mortgages shall be in form and substance reasonably
satisfactory to Administrative Agent.

         "Nebraska Acquisition" means the proposed purchase by Borrower of the
Nebraska Properties pursuant to the Nebraska Acquisition Agreement.

                                       13

<PAGE>   20

         "Nebraska Acquisition Agreement" means that certain Purchase and Sale
Agreement dated February 22, 2000, by and between Borrower and Nebraska Public
Gas Agency, a body politic and corporation under the laws of the State of
Nebraska.

         "Nebraska Acquisition Documents" means the Nebraska Acquisition
Agreement and all agreements, assignments, deeds, conveyances, certificates and
other documents and instruments now or hereafter executed and delivered by or
between Borrower and Nebraska Public Gas Agency, a body politic and corporation
under the laws of the State of Nebraska, pursuant to the Nebraska Acquisition
Agreement or in connection with the Nebraska Acquisition.

         "Nebraska Properties" means the Mineral Interests to be acquired by
Borrower on the Closing Date from Nebraska Public Gas Agency, a body politic and
corporation under the laws of the State of Nebraska, pursuant to the Nebraska
Acquisition Agreement.

         "Net Revenues" means, for Borrower and its Consolidated Subsidiaries
for a month (a) the gross cash receipts of Borrower and its Consolidated
Subsidiaries for such month from whatever source derived, minus (b) the sum of
each of the following for such month (i) severance taxes payable in cash with
respect to Hydrocarbons produced from Borrower's and its Subsidiaries' Mineral
Interests during such month, (ii) lease operating expenses (including payments
under the Operating Agreement) paid by Borrower and its Subsidiaries in cash
during such month, and (iii) ad valorem tax expense accrual attributable to
Borrower and its Subsidiaries' Mineral Interests for such month.

         "Note" means a promissory note of Borrower payable to the order of a
Bank, in substantially the form of Exhibit B hereto, in the amount of such
Bank's Commitment, evidencing the obligation of Borrower to repay to such Bank
the Revolving Loans made by such Bank, together with all modifications,
extensions, renewals and rearrangement thereof, and "Notes" means all of such
Notes collectively.

         "Obligations" means all present and future indebtedness, obligations
and liabilities, and all renewals and extensions thereof, or any part thereof,
of any Credit Party to Administrative Agent or to any Bank or any Affiliate of
any Bank arising pursuant to the Loan Papers or pursuant to any Hedge
Transaction entered into with any Bank or any Affiliate of any Bank, and all
interest accrued thereon and costs, expenses, and attorneys' fees incurred in
the enforcement or collection thereof, regardless of whether such indebtedness,
obligations and liabilities are direct, indirect, fixed, contingent, liquidated,
unliquidated, joint, several or joint and several.

         "Oil & Gas Hedge Transaction" means a Hedge Transaction pursuant to
which any Person hedges the price to be received by it for future production of
Hydrocarbons.

         "Operating Agreement" means the existing Operating Agreements
encumbering the Nebraska Properties, a copy of each of which is attached hereto
as Exhibit C.

                                       14

<PAGE>   21

         "Outstanding Credit" means, on any date, the sum of (a) aggregate
outstanding principal balance of the Revolving Loan on such date, including the
amount of any Borrowing to be made on such date, and (b) the aggregate
outstanding Letter of Credit Exposure on such date, including Letter of Credit
Exposure attributable to Letters of Credit to be issued on such date.

         "PBGC" means the Pension Benefit Guaranty Corporation or any entity
succeeding to any or all of its functions under ERISA.

         "Permitted Encumbrances" means with respect to any asset:

                  (a) Liens (if any) securing the Obligations in favor of Banks;

                  (b) Minor defects in title which do not secure the payment of
                  money and otherwise have no material adverse effect on the
                  value or the operation of the subject property, and for the
                  purposes of this Agreement, a minor defect in title shall
                  include, but not be limited to, easements, rights-of-way,
                  servitudes, permits, surface leases and other similar rights
                  in respect of surface operations, and easements for pipelines,
                  streets, alleys, highways, telephone lines, power lines,
                  railways and other easements and rights-of-way, on, over or in
                  respect of any of the properties of Borrower or any of its
                  Subsidiaries that are customarily granted in the oil and gas
                  industry;

                  (c) Inchoate statutory or operators' liens securing
                  obligations for labor, services, materials and supplies
                  furnished to Mineral Interests in the ordinary course of
                  business which are not delinquent (except to the extent
                  permitted by Section 9.7);

                  (d) Mechanic's, materialmen's, warehouseman's, journeyman's
                  and carrier's liens and other similar liens arising by
                  operation of Law in the ordinary course of business which are
                  not delinquent (except to the extent permitted by Section
                  9.7);

                  (e) Liens for Taxes or assessments not yet due or not yet
                  delinquent, or, if delinquent, that are being contested in
                  good faith in the normal course of business by appropriate
                  action, as permitted by Section 9.7; and

                  (f) Lease burdens payable to third parties encumbering Mineral
                  Interests at the time such Mineral Interests are acquired by
                  Borrower or its Subsidiaries and which are deducted in the
                  calculation of discounted present value in the Reserve Report
                  including, without limitation, any royalty, overriding
                  royalty, net profits interest, production payment, carried
                  interest or reversionary working interest.

         "Permitted Investments" means (a) readily marketable direct obligations
of the United States of America (or investments in mutual funds or similar funds
which invest solely in such obligations), (b) fully insured time deposits and
certificates of deposit with maturities of one year or less of any commercial
bank operating in the United States having capital and surplus in excess of
$500,000,000,

                                       15

<PAGE>   22

and (c) commercial paper of a domestic issuer if at the time of purchase such
paper is rated in one of the two highest ratings categories of Standard and
Poor's Corporation or Moody's Investors Service.

         "Person" means an individual, a corporation, a partnership, an
association, a trust or any other entity or organization, including a Government
Authority.

         "Plan" means an employee benefit plan within the meaning of section
3(3) of ERISA, and any other similar plan, policy or arrangement, including an
employment contract, whether formal or informal and whether legally binding or
not, under which Borrower or an ERISA Affiliate of Borrower has any current or
future obligation or liability or under which any present or former employee of
Borrower or an ERISA Affiliate of Borrower, or such present or former employee's
dependents or beneficiaries, has any current or future right to benefits
resulting from the present or former employee's employment relationship with
Borrower or an ERISA Affiliate of Borrower.

         "Pledge Agreement" means a Pledge Agreement substantially in the form
of Exhibit K to be executed by Taurus pursuant to which Taurus pledges its
limited partnership interest in Borrower to Administrative Agent to secure the
Obligations.

         "Proved Mineral Interests" means, collectively, Proved Producing
Mineral Interests, Proved Nonproducing Mineral Interests, and Proved Undeveloped
Mineral Interests.

         "Proved Nonproducing Mineral Interests" means all Mineral Interests
which constitute proved developed nonproducing reserves.

         "Proved Producing Mineral Interests" means all Mineral Interests which
constitute proved developed producing reserves.

         "Proved Undeveloped Mineral Interests" means all Mineral Interests
which constitute proved undeveloped reserves.

         "Quarterly Date" means the last day of each March, June, September and
December.

         "Quarterly Reduction" means the scheduled reduction in the Borrowing
Base by the Quarterly Reduction Amount on each Quarterly Date pursuant to
Section 5.4 hereof.

         "Quarterly Reduction Amount" means an amount determined by
Administrative Agent in its sole discretion at the time of, and in connection
with, each Redetermination of the Borrowing Base; provided, that such reduction
shall not be less than $200,000. The initial Quarterly Reduction Amount shall be
$200,000.

         "Recognized Value" means, with respect to oil and gas properties, the
discounted present value of the estimated net cash flow to be realized from the
production of Hydrocarbons from such

                                       16

<PAGE>   23

oil and gas properties as determined by Bank of America for purposes of
determining the portion of the Borrowing Base which it attributed to such oil
and gas properties in connection with the most recent Redetermination of the
Borrowing Base as of the date "Recognized Value" is being determined.

         "Redetermination" means (i) any Scheduled Redetermination, or (ii) any
Special Redetermination.

         "Regulation U" means Regulation U of the Board of Governors of the
Federal Reserve System, 12 C.F.R. Part 221, as in effect from time to time.

         "Request for Borrowing" has the meaning set forth in Section 2.1(d).

         "Required Banks" means Banks holding at least sixty-six and sixty-seven
one hundredths of one percent (66.67%) of the Total Commitment.

         "Reserve Report" means an unsuperseded engineering analysis of the
Mineral Interests owned by Borrower, in form and substance reasonably acceptable
to Required Banks, prepared in accordance with customary and prudent practices
in the petroleum engineering industry and Financial Accounting Standards Board
Statement 69. Each Reserve Report required to be delivered by March 1 of each
year pursuant to Section 5.1 shall be prepared by the Approved Petroleum
Engineer. Each other Reserve Report shall be prepared by EXCO's in-house
engineering staff. Notwithstanding the foregoing, in connection with any Special
Redetermination requested by Borrower, the Reserve Report shall be in form and
scope mutually acceptable to Borrower and Required Banks. Until superseded the
Initial Reserve Report shall be considered a Reserve Report.

         "Reserve Requirement" means, at any time, the maximum rate at which
reserves (including, without limitation, any marginal, special, supplemental, or
emergency reserves) are required to be maintained under regulations issued from
time to time by the Board of Governors of the Federal Reserve System (or any
successor) by member banks of the Federal Reserve System against "Eurocurrency
liabilities" (as such term is used in Regulation D). Without limiting the effect
of the foregoing, the Reserve Requirement shall reflect any other reserves
required to be maintained by such member banks with respect to (i) any category
of liabilities which includes deposits by reference to which the Adjusted
Eurodollar Rate is to be determined, or (ii) any category of extensions of
credit or other assets which include Eurodollar Loans. The Adjusted Eurodollar
Rate shall be adjusted automatically on and as of the effective date of any
change in the Reserve Requirement.

         "Restricted Payment" means any payment (whether in cash or other
property) by Borrower or any of its subsidiaries of any type, and whether or not
paid to an Affiliate, and including any payment of expenses, costs, liabilities,
obligations, Distributions or Debt, other than (a) payments of the Obligations,
(b) payments of lease operating expenses, severance and ad valorem taxes, (c)
payments of Distributions expressly permitted by Section 10.2, (d) payments of
general and

                                       17

<PAGE>   24

administrative expenses expressly permitted by Section 11.2, and (e) other
payments in an amount not exceeding $25,000 in any Fiscal Year.

         "Revolving Loan" means the revolving credit loan in an aggregate amount
outstanding at any time not to exceed the amount of the Total Commitment then in
effect less the amount of the Letter of Credit Exposure then outstanding to be
made by Banks to Borrower in accordance with Section 2.1 hereof. The Revolving
Loan may be comprised of the Base Rate Loan and one or more Eurodollar Loans as
Borrower may select in a Request for Borrowing or a Notice of Continuation or
Conversion.

         "Schedule" means a "schedule" attached to this Agreement and
incorporated herein by reference, unless specifically indicated otherwise.

         "Scheduled Redetermination" means any Redetermination of the Borrowing
Base pursuant to Section 5.2.

         "Section" refers to a "section" or "subsection" of this Agreement
unless specifically indicated otherwise.

         "Security Agreement" means a Security Agreement substantially in the
form of Exhibit D to be executed by Borrower and Subsidiaries of Borrower to
Administrative Agent pursuant to which Borrower and such Subsidiaries grant
first and prior Liens in substantially all of their personal property assets to
Administrative Agent for the ratable benefit of the Banks to secure the
Obligations.

         "Sole Lead Arranger" means Banc of America Securities LLC in its
capacity as the Sole Lead Arranger for the credit facility provided hereunder
and any successor thereto.

         "Special Redetermination" means any Redetermination of the Borrowing
Base pursuant to Section 5.3.

         "Subsidiary" means, for any Person, any corporation or other entity of
which securities or other ownership interests having ordinary voting power to
elect a majority of the board of directors or other persons performing similar
functions (including that of a general partner) are at the time directly or
indirectly owned, collectively, by such Person and any Subsidiaries of such
Person. The term Subsidiary shall include Subsidiaries of Subsidiaries (and so
on).

         "Taurus" means Taurus Acquisition, Inc., a Texas corporation.

         "Taurus Change of Control" means the occurrence of any event or
circumstance which, for any reason (including by operation of law), results in
EXCO ceasing to own on a fully-diluted basis, one hundred percent (100%) of the
outstanding capital stock of Taurus of every class, free and clear of all Liens.

                                       18

<PAGE>   25

         "Taxes" means all taxes, assessments, filing or other fees, levies,
imposts, duties, deductions, withholdings, stamp taxes, capital transaction
taxes, foreign exchange taxes or other charges, or other charges of any nature
whatsoever, from time to time or at any time imposed by Law or any Governmental
Authority. "Tax" means any one of the foregoing.

         "Termination Date" means March 24, 2003.

         "Title Review Limit" has the meaning assigned to such term in Section
6.3.

         "Total Commitment" means the Commitments of all Banks in an initial
aggregate amount of $25,000,000 as such amount shall be reduced from time to
time pursuant to Section 2.6.

         "Tribunal" means any state, commonwealth, federal, foreign, territorial
or other court or governmental body, subdivision, agency, department,
commission, board, bureau or instrumentality of a governmental body.

         "Type" shall mean any type of Revolving Loan (i.e., the Base Rate Loan
or Eurodollar Loan).

         SECTION 1.2 Accounting Terms and Determinations. Unless otherwise
specified herein, all accounting terms used herein shall be interpreted, all
accounting determinations hereunder shall be made, and all financial statements
required to be delivered hereunder shall be prepared in accordance with GAAP,
applied on a basis consistent with the most recent audited consolidated
financial statements of Borrower delivered to Banks prior to the date hereof
except for changes concurred in by Borrower's independent certified public
accountants and which are disclosed to Administrative Agent on the next date on
which financial statements are required to be delivered to Banks pursuant to
Section 9.1.

         SECTION 1.3 Petroleum Terms. As used herein, the terms "proved
reserves," "proved developed reserves," "proved developed producing reserves,"
"proved developed nonproducing reserves," and "proved undeveloped reserves" have
the meaning given such terms from time to time and at the time in question by
the Society of Petroleum Engineers of the American Institute of Mining
Engineers.

         SECTION 1.4 Money. Unless expressly stipulated otherwise, all
references herein to "dollars," "money," "funds," "payments," "prepayments" or
other similar financial or monetary terms, are references to currency of the
United States of America.

                                       19

<PAGE>   26

                                    ARTICLE 2
                                   THE CREDIT

         SECTION 2.1 Commitments.

                  (a) Each Bank severally agrees, subject to Sections 2.1(c),
2.1(d), 7.1 and 7.2 and the other terms and conditions set forth in this
Agreement, to lend to Borrower from time to time prior to the Termination Date
amounts not to exceed in the aggregate at any one time outstanding, the amount
of such Bank's Commitment reduced by an amount equal to such Bank's Letter of
Credit Exposure. Each Borrowing shall be in an aggregate principal amount of
$500,000 or any larger integral multiple of $100,000 (except that any Base Rate
Borrowing may be in an amount equal to the Availability at such time), and (ii)
shall be made from Banks ratably in accordance with their respective Commitment
Percentages. Subject to the foregoing limitations and the other provisions of
this Agreement, prior to the Termination Date Borrower may borrow under this
Section 2.1(a), repay amounts borrowed and request new Borrowings to be made
under this Section 2.1.

                  (b) Administrative Agent will, from time to time prior to the
Termination Date, upon request by Borrower, issue Letters of Credit for the
account of Borrower, so long as (i) the sum of (A) the total Letter of Credit
Exposure then existing, and (B) the amount of the requested Letter of Credit
does not exceed $50,000, and (ii) Borrower would be entitled to a Borrowing
under Sections 2.1(a), 2.1(c) and 2.1(d) in the amount of the requested Letter
of Credit. Not less than three (3) Domestic Business Days prior to the requested
date of issuance of any such Letter of Credit, Borrower shall execute and
deliver to Administrative Agent, Administrative Agent's customary letter of
credit application. Each Letter of Credit shall be in the minimum amount of
$10,000 and shall be in form and substance acceptable to Administrative Agent.
No Letter of Credit shall have an expiration date later than the earlier of (i)
the Termination Date, or (ii) one (1) year from the date of issuance. Upon the
date of issuance of a Letter of Credit, Administrative Agent shall be deemed to
have sold to each other Bank, and each other Bank shall be deemed to have
unconditionally and irrevocably purchased from Administrative Agent, a
non-recourse participation in the related Letter of Credit and Letter of Credit
Exposure equal to such Bank's Commitment Percentage of such Letter of Credit and
Letter of Credit Exposure. Upon request of any Bank, but not less often than
quarterly, Administrative Agent shall provide notice to each Bank by telephone,
teletransmission or telex setting forth each Letter of Credit issued and
outstanding pursuant to the terms hereof and specifying the beneficiary and
expiration date of each such Letter of Credit, each Bank's percentage of each
such Letter of Credit and the actual dollar amount of each Bank's participation
held by Administrative Agent thereof for such Bank's account and risk.

         Immediately upon the occurrence of an Event of Default Borrower shall
deposit with Administrative Agent cash in such amounts as Administrative Agent
may request, up to a maximum amount equal to the aggregate existing Letter of
Credit Exposure of all Banks. Any amounts so deposited shall be held by
Administrative Agent for the ratable benefit of all Banks as security for the
outstanding Letter of Credit Exposure and the other Obligations, and Borrower
will, in connection therewith, execute and deliver such security agreements in
form and substance satisfactory to

                                       20

<PAGE>   27

Administrative Agent which it may, in its discretion, require. As drafts or
demands for payment are presented under any Letter of Credit, Administrative
Agent shall apply such cash to satisfy such drafts or demands. When all Letters
of Credit have expired and the Obligations have been repaid in full (and no Bank
has any obligation to lend or issue Letters of Credit hereunder) or such Event
of Default has been cured to the satisfaction of Required Banks, Administrative
Agent shall release to Borrower any remaining cash deposited under this Section
2.1(b). Whenever Borrower is required to make deposits under this Section 2.1(b)
and fails to do so on the day such deposit is due, Administrative Agent or any
Bank may, without notice to Borrower, make such deposit (whether by application
of proceeds of any collateral for the Obligations, by transfers from other
accounts maintained with any Bank or otherwise) using any funds then available
to any Bank of any Credit Party, any guarantor, or any other party liable for
repayment of the Obligations.

         Notwithstanding anything to the contrary contained herein, Borrower
hereby agrees to reimburse Administrative Agent immediately upon demand by
Administrative Agent, and in immediately available funds, for any payment or
disbursement made by Administrative Agent under any Letter of Credit issued by
it. Payment shall be made by Borrower with interest on the amount so paid or
disbursed by Administrative Agent from and including the date payment is made
under any Letter of Credit to and including the date of payment, at the lesser
of (i) the Maximum Lawful Rate, or (ii) the sum of (a) two percent (2%), plus
(b) the Base Rate in effect from day to day. The obligations of Borrower under
this paragraph will continue until all Letters of Credit have expired and all
reimbursement obligations with respect thereto have been paid in full by
Borrower and until all other Obligations shall have been paid in full.

         Borrower shall be obligated to reimburse Administrative Agent upon
demand for all amounts paid under Letters of Credit as set forth in the
immediately preceding paragraph hereof; provided, however, if Borrower for any
reason fails to reimburse Administrative Agent in full upon demand, Banks shall
reimburse Administrative Agent in accordance with each Banks' Commitment
Percentage for amounts due and unpaid from Borrower as set forth hereinbelow;
provided, however, that no such reimbursement made by Banks shall discharge
Borrower's obligations to reimburse Administrative Agent. All reimbursement
amounts payable by any Bank under this Section 2.1(b) shall include interest
thereon at the Federal Funds Rate, from the date of the payment of such amounts
by Administrative Agent to the date of reimbursement by such Bank. No Bank shall
be liable for the performance or nonperformance of the obligations of any other
Bank under this paragraph. The reimbursement obligations of Banks under this
paragraph shall continue after the Termination Date and shall survive
termination of this Agreement and the other Loan Papers.

         Borrower shall indemnify and hold Administrative Agent and each Bank,
and their respective officers, directors, representatives and employees harmless
from loss for any claim, demand or liability which may be asserted against any
or such indemnified party in connection with actions taken under Letters of
Credit or in connection therewith (including losses resulting from the
negligence of any or such indemnified party), and shall pay each indemnified
party for reasonable fees of attorneys and legal costs paid or incurred by each
indemnified party in connection with any matter related to Letters of Credit,
except for losses and liabilities incurred as a direct result of the gross
negligence or wilful

                                       21

<PAGE>   28

misconduct of such indemnified party, IT BEING THE EXPRESS INTENTION OF THE
PARTIES THAT EACH INDEMNIFIED PARTY SHALL BE INDEMNIFIED FOR THE CONSEQUENCES OF
ITS OWN ORDINARY NEGLIGENCE. If Borrower for any reason fails to indemnify or
pay such indemnified party as set forth herein in full, Banks shall indemnify
and pay such indemnified party upon demand, in accordance with each Bank's
Commitment Percentage of such amounts due and unpaid from Borrower. The
provisions of this paragraph shall survive the termination of this Agreement.

         Administrative Agent does not make any representation or warranty, and
does not assume any responsibility with respect to the validity, legality,
sufficiency or enforceability of any letter of credit application executed and
delivered in connection with any Letter of Credit issued hereunder or any
document relative thereto or to the collectability thereunder. Administrative
Agent does not assume any responsibility for the financial condition of Borrower
or for the performance of any obligation of Borrower. Administrative Agent may
use its discretion with respect to exercising or refraining from exercising any
rights, or taking or refraining from taking any action which may be vested in it
or which it may be entitled to take or assert with respect to any Letter of
Credit or any Letter of Credit application. FURTHERMORE, EXCEPT AS SET FORTH
HEREIN, ADMINISTRATIVE AGENT SHALL BE UNDER NO LIABILITY TO ANY BANK, WITH
RESPECT TO ANYTHING ADMINISTRATIVE AGENT MAY DO OR REFRAIN FROM DOING IN THE
EXERCISE OF ITS JUDGMENT, THE SOLE LIABILITY AND RESPONSIBILITY OF
ADMINISTRATIVE AGENT BEING TO HANDLE EACH BANK'S SHARE ON AS FAVORABLE A BASIS
AS ADMINISTRATIVE AGENT HANDLES ITS OWN SHARE. ADMINISTRATIVE AGENT SHALL NOT
HAVE ANY DUTIES OR RESPONSIBILITIES EXCEPT THOSE EXPRESSLY SET FORTH HEREIN AND
THOSE DUTIES AND LIABILITIES SHALL BE SUBJECT TO THE LIMITATIONS AND
QUALIFICATIONS SET FORTH HEREIN. FURTHERMORE, NEITHER ADMINISTRATIVE AGENT, NOR
ANY OF ITS DIRECTORS, OFFICERS, OR EMPLOYEES SHALL BE LIABLE FOR ANY ACTION
TAKEN OR OMITTED (WHETHER OR NOT SUCH ACTION TAKEN OR OMITTED IS EXPRESSLY SET
FORTH HEREIN) UNDER OR IN CONNECTION HEREWITH OR UNDER ANY OTHER INSTRUMENT OR
DOCUMENT IN CONNECTION HEREWITH, EXCEPT FOR GROSS NEGLIGENCE OR WILLFUL
MISCONDUCT. Administrative Agent shall not incur any liability to any Bank,
Borrower, or any Affiliate of any Bank, or Borrower, in acting upon any notice,
document, order, consent, certificate, warrant or other instrument reasonably
believed by Administrative Agent to be genuine or authentic and to be signed by
the proper party.

                  (c) No Bank will be obligated to lend to Borrower hereunder or
incur Letter of Credit Exposure, and Borrower shall not be entitled to borrow
hereunder or obtain Letters of Credit hereunder at any time that a Borrowing
Base Deficiency exists or in an amount which would cause the Outstanding Credit
to exceed the Borrowing Base then in effect. Nothing in this Section 2.1(c)
shall be deemed to limit any Bank's obligation to reimburse Administrative Agent
with respect to its participation in Letters of Credit as a result of the
drawing under any Letter of Credit pursuant to Section 2.1(c).

                                       22

<PAGE>   29

                  (d) proceeds of Borrowings hereunder and Letters of Credit
issued hereunder shall be used only (a) to pay up to $6,800,000 of the purchase
price for the Nebraska Acquisition (including related transaction costs), and
(b) for other general corporate purposes. Letters of Credit may be used for
general corporate purposes. Notwithstanding the foregoing, no Borrowing shall be
made or Letter of Credit issued for any purpose prohibited by Section 10.7
hereof.

                  (e) In order to request any Borrowing under this Section 2.1,
Borrower shall hand deliver, telex or telecopy to Administrative Agent a duly
completed Request for Borrowing (herein so called) prior to 12:00 noon (Dallas,
Texas time), (i) at least one (1) Domestic Business Day before the Borrowing
Date specified for a proposed Base Rate Borrowing, and (ii) at least three (3)
Eurodollar Business Days before the Borrowing Date of a proposed Eurodollar
Borrowing. Each such Request for Borrowing shall be substantially in the form of
Exhibit E hereto, and shall specify:

                           (i) the Borrowing Date of such Borrowing, which shall
                           be a Domestic Business Day in the case of a Base Rate
                           Borrowing or a Eurodollar Business Day in the case of
                           a Eurodollar Borrowing;

                           (ii) the aggregate amount of such Borrowing;

                           (iii) whether such Borrowing is to be a Base Rate
                           Borrowing or a Eurodollar Borrowing;

                           (iv) in the case of a Eurodollar Borrowing, the
                           duration of the Interest Period applicable thereto,
                           subject to the provisions of the definition of
                           Interest Period; and

                           (v) The use of proceeds of such Borrowing.

Upon receipt of a Request for Borrowing, Administrative Agent shall promptly
notify each Bank of the contents thereof and the amount of the Borrowing to be
loaned by such Bank pursuant thereto, and such Request for Borrowing shall not
thereafter be revocable by Borrower. Not later than 12:00 noon (Dallas, Texas
time) on the date of each Borrowing, each Bank shall make available its
Commitment Percentage of such Borrowing, in Federal or other funds immediately
available in Dallas, Texas to Administrative Agent at its address set forth on
Schedule 1 hereto. Notwithstanding the foregoing, if Borrower delivers to
Administrative Agent a Request for Borrowing prior to 10:00 a.m. (Dallas, Texas
time) on a Domestic Business Day requesting a Base Rate Borrowing on such day,
each Bank shall use its best efforts to make available to Administrative Agent
its Commitment Percentage of such Borrowing by 1:00 p.m. (Dallas, Texas time) on
the same day. Unless Administrative Agent determines that any applicable
condition specified in Section 7.2 has not been satisfied, Administrative Agent
will make the funds so received from Banks available to Borrower at
Administrative Agent's aforesaid address.

                                       23

<PAGE>   30

                  (f) In order to request any Letter of Credit hereunder,
Borrower shall hand deliver, telex or telecopy to Administrative Agent a duly
completed Request for Letter of Credit (herein so called) prior to 12:00 noon
(Dallas, Texas time) at least three (3) Domestic Business Days before the date
specified for issuance of such Letter of Credit. Each Request for Letter of
Credit shall be substantially in the form of Exhibit F hereto, shall be
accompanied by Administrative Agent's duly completed and executed letter of
credit application and agreement and shall specify:

                  (i) the requested date for issuance of such Letter of Credit;

                  (ii) the terms of such requested Letter of Credit, including
                  the name and address of the beneficiary, the stated amount,
                  the expiration date and the conditions under which drafts
                  under such Letter of Credit are to be available; and

                  (iii) the purpose of such Letter of Credit.

Upon receipt of a Request for Letter of Credit, Administrative Agent shall
promptly notify each Bank of the contents thereof, including the amount of the
requested Letter of Credit, and such Request for Letter of Credit shall not
thereafter be revocable by Borrower. No later than 12:00 noon (Dallas, Texas
time) on the date each Letter of Credit is requested, unless Administrative
Agent determines that any applicable condition precedent set forth in Section
7.2 hereof has not been satisfied, Administrative Agent will issue and deliver
such Letter of Credit pursuant to the instructions of Borrower.

         SECTION 2.2 Notes. Each Bank's Commitment Percentage of the Revolving
Loan shall be evidenced by a single Note payable to the order of such Bank in an
amount equal to such Bank's Commitment.

         SECTION 2.3 Interest Rates; Payments.

                  (a) The principal amount of the Base Rate Loan outstanding
from day to day shall bear interest at a rate per annum equal to the Base Rate
in effect from day to day; provided that in no event shall the rate charged
hereunder or under the Notes exceed the Maximum Lawful Rate. Interest on the
principal of the Base Rate Loan shall be payable as it accrues pursuant to
Section 2.5 and on each Quarterly Date, and on the Termination Date.

                  (b) The principal amount of each Eurodollar Loan shall bear
interest for the Interest Period applicable thereto at a rate per annum equal to
the sum of (i) the Applicable Margin, plus (ii) the applicable Adjusted
Eurodollar Rate; provided that in no event shall the rate charged hereunder or
under the Notes exceed the Maximum Lawful Rate. Interest on any portion of the
principal of each Eurodollar Loan shall be payable as it accrues pursuant to
Section 2.5 and, in the case of accrued interest which is not fully paid
pursuant to Section 2.5 and which (i) accrues on the outstanding principal
balance of a Eurodollar Loan subject to an Interest Period of one (1), two (2)
or three (3) months shall be payable on the last day of the Interest Period
applicable thereto, and (ii)

                                       24

<PAGE>   31

on the outstanding principal balance of any Eurodollar Loan having an Interest
Period of more than three (3) months shall be payable on the last day of the
Interest Period applicable thereto and on each Quarterly Date.

                  (c) So long as no Default or Event of Default shall be
continuing, subject to the provisions of this Section 2.3, Borrower shall have
the option of having all or any portion of the principal outstanding under the
Revolving Loan be a Base Rate Loan or one (1) or more Eurodollar Loans, which
shall bear interest at rates determined by reference to the Base Rate and the
Adjusted Eurodollar Rate, respectively; provided, that each Eurodollar Loan
shall be in a minimum amount of $500,000 and shall be in an amount which is an
integral multiple of $100,000. Prior to the termination of each Interest Period
with respect to each Eurodollar Loan, Borrower shall give written notice (a
"Notice of Continuation or Conversion") in the form of Exhibit G attached hereto
to Administrative Agent of the Type of Revolving Loan which shall be applicable
to the principal of such Eurodollar Loan upon the expiration of such Interest
Period. Such Notice of Continuation or Conversion shall be given to
Administrative Agent at least one (1) Domestic Business Day, in the case of a
Base Rate Loan selection and three (3) Eurodollar Business Days, in the case of
a Eurodollar Loan selection, prior to the termination of the Interest Period
then expiring. If Borrower shall specify a Eurodollar Loan, such Notice of
Continuation or Conversion shall also specify the length of the succeeding
Interest Period (subject to the definition of such term) selected by Borrower.
Each Notice of Continuation or Conversion shall be irrevocable and effective
upon notification thereof to Administrative Agent. If the required Notice of
Continuation or Conversion shall not have been timely received by Administrative
Agent, Borrower shall be deemed to have elected that the principal of the
Eurodollar Loan subject to the Interest Period then expiring be a part of the
Base Rate Loan upon the expiration of such Interest Period and Borrower will be
deemed to have given Administrative Agent notice of such election. Subject to
the limitations set forth in this Section 2.3(c) on the amount and number of
Eurodollar Loans, Borrower shall have the right to convert (a "Conversion") all
or any part of the Base Rate Loan to a Eurodollar Loan by giving Administrative
Agent a Notice of Continuation or Conversion of such election at least three (3)
Eurodollar Business Days prior to the date on which Borrower elects to make such
conversion (a "Conversion Date"). The Conversion Date selected by Borrower shall
be a Eurodollar Business Day. Notwithstanding anything in this Section 2.3 to
the contrary, no portion of the principal of the Base Rate Loan may be Converted
to a Eurodollar Loan and no Eurodollar Loan may be Continued as such when any
Default or Event of Default has occurred and is continuing, but each such
Eurodollar Loan shall be automatically Converted to the Base Rate Loan on the
last day of each applicable Interest Period. Borrower shall not be permitted to
have more than four (4) Eurodollar Loans in effect at any time.

                  (d) Notwithstanding anything to the contrary set forth in
Section 2.3(a) or 2.3(b) above, all overdue principal of the Obligations and, to
the extent permitted by law, overdue interest, shall bear interest from the date
due, payable on demand, for each day until paid at a rate per annum equal to the
lesser of (a) the sum of (i) two percent (2%), plus (ii) the Base Rate in effect
from day to day, and (b) the Maximum Lawful Rate.

                                       25

<PAGE>   32

                  (e) Administrative Agent shall determine each interest rate
applicable to the Revolving Loan in accordance with the terms hereof.
Administrative Agent shall promptly notify Borrower and Banks by telex, telecopy
or cable of each rate of interest so determined, and its determination thereof
shall be conclusive in the absence of manifest error.

                  (f) Notwithstanding the foregoing, if at any time the rate of
interest calculated with reference to the Base Rate or the Eurodollar Rate
hereunder (the "contract rate") is limited to the Maximum Lawful Rate, any
subsequent reductions in the contract rate shall not, to the extent permitted by
law, reduce the rate of interest on the affected Revolving Loan below the
Maximum Lawful Rate until the total amount of interest accrued equals the amount
of interest which would have accrued if the contract rate had at all times been
in effect. In the event that at maturity (stated or by acceleration), or at
final payment of any Note, the total amount of interest paid or accrued on such
Note is less than the amount of interest which would have accrued if the
contract rate had at all times been in effect with respect thereto, then at such
time, to the extent permitted by law, Borrower shall pay to the holder of such
Note an amount equal to the difference between (i) the lesser of the amount of
interest which would have accrued if the contract rate had at all times been in
effect and the amount of interest which would have accrued if the Maximum Lawful
Rate had at all times been in effect, and (ii) the amount of interest actually
paid on such Note.

                  (g) Interest payable hereunder computed by reference to the
Eurodollar Rate shall be computed based on the number of actual days elapsed
assuming that each calendar year consisted of 360 days. Interest payable
hereunder computed by reference to the Base Rate shall be computed based on the
actual number of days elapsed assuming that each calendar year consisted of 365
days.

         SECTION 2.4  Mandatory Prepayments During Borrowing Base Deficiency.

                  (a) In the event a Borrowing Base Deficiency exists after
giving effect to, and as a result of, any Redetermination, Borrower shall, at
its option, either (i) eliminate such Borrowing Base Deficiency by making a
single mandatory prepayment of principal on the Revolving Loan in an amount
equal to the entire amount of such Borrowing Base Deficiency on the first
Monthly Date following the date on which such Borrowing Base Deficiency is
determined to exist, or (ii) eliminate such Borrowing Base Deficiency by making
six (6) consecutive mandatory prepayments of principal on the Revolving Loan
each of which shall be in the amount of one sixth (1/6th) of the amount of such
Borrowing Base Deficiency commencing on the first Monthly Date following the
date on which such Borrowing Base Deficiency is determined to exist and
continuing on each Monthly Date thereafter. If a Borrowing Base Deficiency
cannot be eliminated pursuant to this clause (a) by prepayment of the Revolving
Loan in full (as a result of outstanding Letter of Credit Exposure), on each
Monthly Date, Borrower shall also deposit cash with Administrative Agent, to be
held by Administrative Agent to secure outstanding Letter of Credit Exposure in
the manner contemplated by Section 2.1(b), in an amount at least equal to one
sixth (1/6th) of the balance of such Borrowing Base Deficiency (i.e., one-sixth
of the difference between the Borrowing Base Deficiency and the remaining
outstanding principal of the Revolving Loan on the date such Borrowing Base
Deficiency is first determined to occur).

                                       26

<PAGE>   33

                  (b) In the event a Borrowing Base Deficiency occurs or an
existing Borrowing Base Deficiency increases as a result of any Quarterly
Reduction, then, on the date of such Quarterly Reduction, Borrower shall make a
prepayment of principal on the Revolving Loan in the amount of such Borrowing
Base Deficiency (or increase in any existing Borrowing Base Deficiency).

                  (c) For purposes of clause (a) and (b) preceding, if (i) the
date of any Redetermination is also the date of any Quarterly Reduction, and
(ii) the Borrowing Base in effect immediately prior to the date of such
Redetermination is higher than the amount of the Borrowing Base as reduced on
the date of such Redetermination, then the reduction in the Borrowing Base which
becomes effective on the date of such Redetermination will be deemed to have
resulted from the Quarterly Reduction to the extent of the Quarterly Reduction
Amount then in effect.

         SECTION 2.5 Mandatory Prepayments from Cash Flow. Commencing on August
15, 2000 and continuing on the 15th day of each November, February, May and
August thereafter until the Commitments are terminated and the Obligations are
paid in full, Borrower shall make a mandatory prepayment on the Revolving Loan
in an amount equal to the Dedication Percentage then in effect of Borrower's Net
Revenues for the immediately preceding Fiscal Quarter. Each such payment shall
be applied first to accrued but unpaid interest and then to principal. In the
event mandatory prepayments are required under this Section 2.5 at any time when
mandatory prepayments are required under Section 2.4(a), the mandatory
prepayments required by this Section 2.5 shall be applied to reduce the
prepayments Borrower is required to make pursuant to Section 2.4(a) in direct
order of maturity.

         SECTION 2.6 Voluntary Reduction of Commitments. Borrower may, by notice
to Administrative Agent five (5) Domestic Business Days prior to the effective
date of any such reduction, reduce the Total Commitment (and thereby reduce the
Commitment of each Bank ratably) in amounts not less than $5,000,000 and in an
amount which is an integral multiple of $1,000,000. On the effective date of any
such reduction, Borrower shall, to the extent required as a result of such
reduction, make a principal payment on the Revolving Loan in an amount
sufficient to cause the principal balance of the Revolving Loan to be equal to
or less than the Total Commitment as thereby reduced. Notwithstanding the
foregoing, Borrower shall not be permitted to voluntarily reduce the Total
Commitment to an amount less than the aggregate Letter of Credit Exposure of all
Banks.

         SECTION 2.7 Termination of Commitments; Final Maturity of Revolving
Loan. The Total Commitment (and the Commitment of each Bank) shall terminate,
and the entire outstanding principal balance of the Revolving Loan, all interest
accrued thereon, all accrued but unpaid fees hereunder and all other outstanding
Obligations shall be due and payable in full on the Termination Date.

         SECTION 2.8 Unused Commitment Fee. On the Termination Date, on each
Quarterly Date prior to the Termination Date, and, in the event the Commitments
are terminated in their entirety prior to the Termination Date, on the date of
such termination, Borrower shall pay to Administrative Agent, for the ratable
benefit of each Bank, a commitment fee equal to .375% (computed on a per annum
basis on the basis of actual days elapsed and as if each calendar year consisted
of 365 days)

                                       27

<PAGE>   34

of the average daily Availability for the Fiscal Quarter (or portion thereof)
ending on the date such payment is due.

         SECTION 2.9 Borrowing Base Increase Fee. Simultaneously with each
increase in the Borrowing Base, Borrower shall pay to Administrative Agent for
the ratable benefit of each Bank, a borrowing base increase fee in an amount to
be mutually agreed upon by Borrower and Administrative Agent in connection with
such increase.

         SECTION 2.10 Letter of Credit Fee.

                  (a) Borrower shall pay to Administrative Agent for its own
account a fee on the daily average amount of all Letter of Credit Exposure
computed at a per annum rate for each day of .125% of such daily average Letter
of Credit Exposure. Such fee shall be payable in arrears on each Quarterly Date.
Notwithstanding the foregoing, no fee shall accrue or be payable pursuant to
this Section 2.10(a) at any time that there is only one Bank which is a party to
this Credit Agreement.

                  (b) Borrower shall pay to Administrative Agent for the ratable
benefit of each Bank a fee on the daily average amount of all Letter of Credit
Exposure computed at a per annum rate for each day equal to the Applicable
Margin in effect for Eurodollar Loans on such day. Such fee shall be payable
quarterly in arrears on each Quarterly Date.

         SECTION 2.11 Agency and other Fees. Borrower shall pay to
Administrative Agent and its Affiliates such other reasonable fees and amounts
as Borrower shall be required to pay to Administrative Agent and its Affiliates
from time to time pursuant to any separate agreement between Borrower and
Administrative Agent or such Affiliates. Such fees and other amounts shall be
retained by Administrative Agent and its Affiliates, and no Bank (other than
Administrative Agent) shall have any interest therein.

         SECTION 2.12 Closing Fee. Borrower shall pay to Administrative Agent,
for the ratable benefit of each Bank, a non-refundable closing fee on the
Closing Date in the amount of $50,000.

                                    ARTICLE 3
                               GENERAL PROVISIONS

         SECTION 3.1 Delivery and Endorsement of Notes. Simultaneously with the
execution of this Agreement, Administrative Agent shall deliver to each Bank the
Note payable to such Bank. Each Bank may endorse (and prior to any transfer of
its Note shall endorse) on the schedules attached and forming a part thereof
appropriate notations to evidence the date and amount of its Commitment
Percentage of each Borrowing and Type of each Revolving Loan made by it, the
Interest Period applicable thereto, and the date and amount of each payment of
principal made by Borrower with respect thereto; provided that the failure by
any Bank to so endorse its Note shall not affect the liability of Borrower for
the repayment of all amounts outstanding under such Note together with

                                       28

<PAGE>   35

interest thereon. Each Bank is hereby irrevocably authorized by Borrower to
endorse its Note and to attach to and make a part of any Note a continuation of
any such schedule as required.

         SECTION 3.2 General Provisions as to Payments.

                  (a) Borrower shall make each payment of principal of, and
interest on, the Revolving Loan and all fees payable hereunder shall be paid not
later than 12:00 noon (Dallas, Texas time) on the date when due, in Federal or
other funds immediately available in Dallas, Texas, to Administrative Agent at
its address set forth on Schedule 1 hereto. Administrative Agent will promptly
(and if such payment is received by Administrative Agent by 10:00 a.m. (Dallas,
Texas time) and otherwise if reasonably possible, on the same Domestic Business
Day) distribute to each Bank its Commitment Percentage of each such payment
received by Administrative Agent for the account of Banks. Whenever any payment
of (a) principal of, or interest on, any portion of the Base Rate Loan, or (b)
fees shall be due on a day which is not a Domestic Business Day, the date for
payment thereof shall be extended to the next succeeding Domestic Business Day.
Whenever any payment of principal of, or interest on, any Eurodollar Loan shall
be due on a day which is not a Eurodollar Business Day, the date for payment
thereof shall be extended to the next succeeding Eurodollar Business Day
(subject to the definition of Interest Period). If the date for any payment of
principal is extended by operation of Law or otherwise, interest thereon shall
be payable for such extended time. Borrower hereby authorizes Administrative
Agent to charge from time to time against Borrower's accounts with
Administrative Agent any amount then due.

                  (b) Prior to the occurrence of an Event of Default, all
principal payments received by Banks shall be applied first to Eurodollar Loans
outstanding with Interest Periods ending on the date of such payment, then to
the Base Rate Loan, and then to Eurodollar Loans, next maturing until such
principal payment is fully applied.

                  (c) After the occurrence of an Event of Default, all amounts
collected or received by Administrative Agent or any Bank shall be applied first
to the payment of all proper costs incurred by Administrative Agent in
connection with the collection thereof (including reasonable expenses and
disbursements of Administrative Agent), second to the payment of all proper
costs incurred by Banks in connection with the collection thereof (including
reasonable expenses and disbursements of Banks), third to the reimbursement of
any advances made by Banks to effect performance of any unperformed covenants of
Borrower or any of its Subsidiaries under any of the Loan Papers, fourth to the
payment of any unpaid fees required pursuant to Section 2.11, fifth to the
payment of any unpaid fees required pursuant to Sections 2.8, 2.9, and 2.10,
sixth, to payment to each Bank of its Commitment Percentage of the outstanding
principal of the Revolving Loan and accrued but unpaid interest thereon, and
seventh to establish the deposits required in Section 2.1(b). All payments
received by a Bank after the occurrence of an Event of Default for application
to the principal of the Revolving Loan shall be applied by such Bank in the
manner provided in Section 3.2(b).

                                       29

<PAGE>   36

                                    ARTICLE 4
                             CHANGE IN CIRCUMSTANCES

         SECTION 4.1 Increased Cost and Reduced Return.

                  (a) If, after the date hereof, the adoption of any applicable
Law, rule, or regulation, or any change in any applicable Law, rule, or
regulation, or any change in the interpretation or administration thereof by any
Governmental Authority, central bank, or comparable agency charged with the
interpretation or administration thereof, or compliance by any Bank (or its
Applicable Lending Office) with any request or directive (whether or not having
the force of Law) of any such Governmental Authority, central bank, or
comparable agency:

                  (i) shall subject such Bank (or its Applicable Lending Office)
                  to any Tax, duty, or other charge with respect to any
                  Eurodollar Loans, its Note, or its obligation to make
                  Eurodollar Loans, or change the basis of taxation of any
                  amounts payable to such Bank (or its Applicable Lending
                  Office) under this Agreement or its Note in respect of any
                  Eurodollar Loans (other than Taxes imposed on the overall net
                  income of such Bank by the jurisdiction in which such Bank has
                  its principal office or such Applicable Lending Office);

                  (ii) shall impose, modify, or deem applicable any reserve,
                  special deposit, assessment, or similar requirement (other
                  than the Reserve Requirement utilized in the determination of
                  the Adjusted Eurodollar Rate) relating to any extensions of
                  credit or other assets of, or any deposits with or other
                  liabilities or commitments of, such Bank (or its Applicable
                  Lending Office), including the Commitment of such Bank
                  hereunder; or

                  (iii) shall impose on such Bank (or its Applicable Lending
                  Office) or on the London interbank market any other condition
                  affecting this Agreement or its Note or any of such extensions
                  of credit or liabilities or commitments;

and the result of any of the foregoing is to increase the cost to such Bank (or
its Applicable Lending Office) of making, Converting into, Continuing, or
maintaining any Eurodollar Loans or to reduce any sum received or receivable by
such Bank (or its Applicable Lending Office) under this Agreement or its Note
with respect to any Eurodollar Loans, then Borrower shall pay to such Bank on
demand such amount or amounts as will compensate such Bank for such increased
cost or reduction. If any Bank requests compensation by Borrower under this
Section 4.1(a), Borrower may, by notice to such Bank (with a copy to
Administrative Agent), suspend the obligation of such Bank to make or Continue
Eurodollar Loans, or to Convert all or part of the Base Rate Loan owing to such
Bank to Eurodollar Loans, until the event or condition giving rise to such
request ceases to be in effect (in which case the provisions of Section 4.4
shall be applicable); provided that such suspension shall not affect the right
of such Bank to receive the compensation so requested.

                                       30

<PAGE>   37

                  (b) If, after the date hereof, any Bank shall have determined
that the adoption of any applicable Law, rule, or regulation regarding capital
adequacy or any change therein or in the interpretation or administration
thereof by any Governmental Authority, central bank, or comparable agency
charged with the interpretation or administration thereof, or any request or
directive regarding capital adequacy (whether or not having the force of Law) of
any such Governmental Authority, central bank, or comparable agency, has or
would have the effect of reducing the rate of return on the capital of such Bank
or any corporation controlling such Bank as a consequence of such Bank's
obligations hereunder to a level below that which such Bank or such corporation
could have achieved but for such adoption, change, request, or directive (taking
into consideration its policies with respect to capital adequacy), then from
time to time upon demand Borrower shall pay to such Bank such additional amount
or amounts as will compensate such Bank for such reduction.

                  (c) Each Bank shall promptly notify Borrower and
Administrative Agent of any event of which it has knowledge, occurring after the
date hereof, which will entitle such Bank to compensation pursuant to this
Section 4.1 and will designate a different Applicable Lending Office if such
designation will avoid the need for, or reduce the amount of, such compensation
and will not, in the judgment of such Bank, be otherwise disadvantageous to it.
Any Bank claiming compensation under this Section 4.1 shall furnish to Borrower
and Administrative Agent a statement setting forth the additional amount or
amounts to be paid to it hereunder which shall be conclusive in the absence of
manifest error. In determining such amount, such Bank may use any reasonable
averaging and attribution methods.

         SECTION 4.2 Limitation on Types of Revolving Loans. If on or prior to
the first day of any Interest Period for any Eurodollar Loan:

                  (a) Administrative Agent determines (which determination shall
be conclusive) that by reason of circumstances affecting the relevant market,
adequate and reasonable means do not exist for ascertaining the Eurodollar Rate
for such Interest Period; or

                  (b) Required Banks determine (which determination shall be
conclusive) and notify Administrative Agent that the Adjusted Eurodollar Rate
will not adequately and fairly reflect the cost to Banks of funding Eurodollar
Loans for such Interest Period;

then Administrative Agent shall give Borrower prompt notice thereof specifying
the relevant amounts or periods, and so long as such condition remains in
effect, Banks shall be under no obligation to make additional Eurodollar Loans,
Continue Eurodollar Loans, or to Convert all or any part of the Base Rate Loan
into Eurodollar Loans and Borrower shall, on the last day(s) of the then current
Interest Period(s) for the outstanding Eurodollar Loans, either prepay such
Eurodollar Loans or Convert such Eurodollar Loans into the Base Rate Loan in
accordance with the terms of this Agreement.

         SECTION 4.3 Illegality. Notwithstanding any other provision of this
Agreement, in the event that it becomes unlawful for any Bank or its Applicable
Lending Office to make, maintain, or

                                       31

<PAGE>   38

fund Eurodollar Loans hereunder, then such Bank shall promptly notify Borrower
thereof and such Bank's obligation to make or Continue Eurodollar Loans and to
Convert all or any part of the Base Rate Loan into Eurodollar Loans shall be
suspended until such time as such Bank may again make, maintain, and fund
Eurodollar Loans (in which case the provisions of Section 2.7 shall be
applicable).

         SECTION 4.4 Treatment of Affected Loans. If the obligation of any Bank
to make a Eurodollar Loan or to Continue Eurodollar Loans, or to Convert all or
any part of the Base Rate Loan into Eurodollar Loans shall be suspended pursuant
to Section 4.1 or hereof, such Bank's Eurodollar Loans shall be automatically
Converted into the Base Rate Loan on the last day(s) of the then current
Interest Period(s) for such Eurodollar Loans (or, in the case of a Conversion
required by Section 4.3 hereof, on such earlier date as such Bank may specify to
Borrower with a copy to Administrative Agent) and, unless and until such Bank
gives notice as provided below that the circumstances specified in Section 4.1
or 4.3 hereof that gave rise to such Conversion no longer exist:

                  (a) to the extent that such Bank's Eurodollar Loans have been
so Converted, all payments and prepayments of principal that would otherwise be
applied to such Bank's Eurodollar Loans shall be applied instead to its
Commitment Percentage of the Base Rate Loan; and

                  (b) all Revolving Loans that would otherwise be made or
Continued by such Bank as Eurodollar Loans shall be made or Continued instead as
a part of the Base Rate Loan, and all or any part of the Base Rate Loan held by
such Bank that would otherwise be Converted into Eurodollar Loans shall remain
as part of the Base Rate Loan.

If such Bank gives notice to Borrower (with a copy to Administrative Agent) that
the circumstances specified in Section 4.1 or 4.3 hereof that gave rise to the
Conversion of such Bank's Eurodollar Loans pursuant to this Section 4.4 no
longer exist (which such Bank agrees to do promptly upon such circumstances
ceasing to exist) at a time when Eurodollar Loans made by other Banks are
outstanding, such Bank's portion of the Base Rate Loan shall be automatically
Converted, on the first day(s) of the next succeeding Interest Period(s) for
such outstanding Eurodollar Loans, to the extent necessary so that, after giving
effect thereto, all Eurodollar Loans held by Banks holding Eurodollar Loans are
held pro rata (as to principal amounts and Interest Periods) in accordance with
their respective Commitments.

         SECTION 4.5 Compensation. Upon the request of any Bank, Borrower shall
pay to such Bank such amount or amounts as shall be sufficient (in the
reasonable opinion of such Bank) to compensate it for any loss, cost, or expense
incurred by it as a result of:

                  (a) any payment, prepayment, or Conversion of a Eurodollar
Loan for any reason (including, without limitation, the acceleration of the
Revolving Loans pursuant to Section 12.1) on a date other than the last day of
the Interest Period for such Revolving Loan; or

                  (b) any failure by Borrower for any reason (including, without
limitation, the failure of any condition precedent specified in Article 7 to be
satisfied) to borrow, Convert, Continue,

                                       32

<PAGE>   39

or prepay a Eurodollar Loan on the date for such Borrowing, Conversion,
Continuation, or prepayment specified in the relevant Request for Borrowing, or
notice of prepayment, Continuation, or Conversion under this Agreement.

         SECTION 4.6 Taxes.

                  (a) Any and all payments by Borrower to or for the account of
any Bank or Administrative Agent hereunder or under any other Loan Paper shall
be made free and clear of and without deduction for any and all present or
future Taxes, and all liabilities with respect thereto, excluding, in the case
of each Bank and Administrative Agent, Taxes imposed on its income, and
franchise Taxes imposed on it, by the jurisdiction under the Laws of which such
Bank (or its Applicable Lending Office) or Administrative Agent (as the case may
be) is organized or any political subdivision thereof. If Borrower shall be
required by Law to deduct any Taxes from or in respect of any sum payable under
this Agreement or any other Loan Paper to any Bank or Administrative Agent, (i)
the sum payable shall be increased as necessary so that after making all
required deductions (including deductions applicable to additional sums payable
under this Section 4.6) such Bank or Administrative Agent receives an amount
equal to the sum it would have received had no such deductions been made, (ii)
Borrower shall make such deductions, (iii) Borrower shall pay the full amount
deducted to the relevant taxation authority or other authority in accordance
with applicable Law, and (iv) Borrower shall furnish to Administrative Agent, at
its address set forth on Schedule 1 hereto, the original or a certified copy of
a receipt evidencing payment thereof.

                  (b) In addition, Borrower agrees to pay any and all present or
future stamp or documentary Taxes and any other excise or property Taxes or
charges or similar levies which arise from any payment made under this Agreement
or any other Loan Paper or from the execution or delivery of, or otherwise with
respect to, this Agreement or any other Loan Paper (hereinafter referred to as
"Other Taxes").

                  (c) Borrower agrees to indemnify each Bank and Administrative
Agent for the full amount of Taxes and Other Taxes (including, without
limitation, any Taxes or Other Taxes imposed or asserted by any jurisdiction on
amounts payable under this Section 4.6) paid by such Bank or Administrative
Agent (as the case may be) and any liability (including penalties, interest, and
expenses) arising therefrom or with respect thereto.

                  (d) Each Bank organized under the Laws of a jurisdiction
outside the United States, on or prior to the date of its execution and delivery
of this Agreement in the case of each Bank listed on Schedule 1 hereto and on or
prior to the date on which it becomes a Bank in the case of each other Bank, and
from time to time thereafter if requested in writing by Borrower or
Administrative Agent (but only so long as such Bank remains lawfully able to do
so), shall provide Borrower and Administrative Agent with (i) Internal Revenue
Service Form 1001 or 4224, as appropriate, or any successor form prescribed by
the Internal Revenue Service, certifying that such Bank is entitled to benefits
under an income Tax treaty to which the United States is a party which reduces
the rate of withholding Tax on payments of interest or certifying that the
income receivable pursuant to this

                                       33

<PAGE>   40

Agreement is effectively connected with the conduct of a trade or business in
the United States, (ii) Internal Revenue Service Form W-8 or W-9, as
appropriate, or any successor form prescribed by the Internal Revenue Service,
and (iii) any other form or certificate required by any taxing authority
(including any certificate required by Sections 871(h) and 881(c) of the Code),
certifying that such Bank is entitled to an exemption from or a reduced rate of
Tax on payments pursuant to this Agreement or any of the other Loan Papers.

                  (e) For any period with respect to which a Bank has failed to
provide Borrower and Administrative Agent with the appropriate form pursuant to
Section 4.6(d) (unless such failure is due to a change in treaty, Law, or
regulation occurring subsequent to the date on which a form originally was
required to be provided), such Bank shall not be entitled to indemnification
under Section 4.6(a) or 4.6(b) with respect to Taxes imposed by the United
States; provided, however, that should a Bank, which is otherwise exempt from or
subject to a reduced rate of withholding Tax, become subject to Taxes because of
its failure to deliver a form required hereunder, Borrower shall take such steps
as such Bank shall reasonably request to assist such Bank to recover such Taxes.

                  (f) If Borrower is required to pay additional amounts to or
for the account of any Bank pursuant to this Section 4.6, then such Bank will
agree to use reasonable efforts to change the jurisdiction of its Applicable
Lending Office so as to eliminate or reduce any such additional payment which
may thereafter accrue if such change, in the judgment of such Bank, is not
otherwise disadvantageous to such Bank.

                  (g) Within thirty (30) days after the date of any payment of
Taxes Borrower is required to pay pursuant to this Section 4.6, Borrower shall
furnish to Administrative Agent the original or a certified copy of a receipt
evidencing such payment.

                  (h) Without prejudice to the survival of any other agreement
of Borrower hereunder, the agreements and obligations of Borrower contained in
this Section 4.6 shall survive the termination of the Commitments and the
payment in full of the Notes.

         SECTION 4.7 Discretion of Banks as to Manner of Funding.
Notwithstanding any provisions of this Agreement to the contrary, each Bank
shall be entitled to fund and maintain its funding of all or any part of its
Commitment in any manner it sees fit, it being understood, however, that for the
purposes of this Agreement all determinations hereunder shall be made as if such
Bank had actually funded and maintained each Eurodollar Loan through the
purchase of deposits having a maturity corresponding to the last day of the
Interest Period applicable to such Eurodollar Loan and bearing an interest rate
equal to the Adjusted Eurodollar Rate for such Interest Period.

                                       34

<PAGE>   41

                                    ARTICLE 5
                                 BORROWING BASE

         SECTION 5.1 Reserve Report; Proposed Borrowing Base. As soon as
available and in any event by March 1 and September 1 of each year commencing
September 1, 2000, Borrower shall deliver to each Bank a Reserve Report prepared
as of the immediately preceding December 31 and June 30 respectively.
Simultaneously with the delivery to Administrative Agent and each Bank of each
Reserve Report, Borrower shall notify each Bank of the amount of the Borrowing
Base which Borrower requests become effective on the next Redetermination Date
(or such date promptly following such Redetermination Date as Required Banks
shall elect).

         SECTION 5.2 Scheduled Redeterminations of the Borrowing Base;
Procedures and Standards. Based in part on the Reserve Reports made available to
Banks pursuant to Section 5.1, Banks shall redetermine the Borrowing Base (i) on
a date selected by Required Banks by written notice to Borrower which date shall
be on or around each April 1 and October 1 commencing October 1, 2000 (or, in
each such case, on a date promptly thereafter as reasonably possible based on
the engineering and other information available to Banks). Any Borrowing Base
which becomes effective as a result of any Redetermination of the Borrowing Base
shall be subject to the following restrictions: (a) such Borrowing Base shall
not exceed the Borrowing Base requested by Borrower pursuant to Sections 5.1 or
5.3 (as applicable), (b) such Borrowing Base shall not exceed the Total
Commitment then in effect, (c) to the extent such Borrowing Base represents an
increase from the Borrowing Base in effect prior to such Redetermination, such
Borrowing Base shall be approved by all Banks, and (d) any Borrowing Base which
represents a decrease in the Borrowing Base in effect prior to such
Redetermination, or a reaffirmation of such prior Borrowing Base, shall be
approved by Required Banks. Each Redetermination shall be made by Banks in their
sole discretion. Without limiting such discretion, Borrower acknowledges and
agrees that Banks (i) may make such assumptions regarding appropriate existing
and projected pricing for Hydrocarbons as they deem appropriate in their sole
discretion, (ii) may make such assumptions regarding projected rates and
quantities of future production of Hydrocarbons from the Mineral Interests owned
by Borrower as they deem appropriate in their sole discretion, (iii) may
consider the projected cash requirements of Borrower and its Subsidiaries, (iv)
are not required to consider any asset other than Proved Mineral Interests owned
by Borrower which are subject to first and prior Liens in favor of
Administrative Agent for the ratable benefit of Banks to the extent required by
Section 6.1 hereof, and (v) may make such other assumptions, considerations and
exclusions as each Bank deems appropriate in the exercise of its sole
discretion. It is further acknowledged and agreed that each Bank may consider
such other credit factors as it deems appropriate in the exercise of its sole
discretion and shall have no obligation in connection with any Redetermination
to approve any increase from the Borrowing Base in effect prior to such
Redetermination. Promptly following any Redetermination of the Borrowing Base,
Administrative Agent shall deliver written notice to Borrower specifying (a) the
amount of the Borrowing Base as redetermined (which Borrowing Base shall be
effective as of the date specified in such notice, and subject to Section 5.4
shall remain in effect for all purposes of this Agreement

                                       35

<PAGE>   42

until the next Redetermination), and (b) the Quarterly Reduction Amount to be in
effect until the next Redetermination.

         SECTION 5.3 Special Redetermination.

                  (a) In addition to Scheduled Redeterminations, Required Banks
shall be permitted to make a Special Redetermination of the Borrowing Base once
in each period between Scheduled Redeterminations. Any request by Required Banks
pursuant to this Section 5.3(a) shall be submitted to Administrative Agent and
Borrower.

                  (b) In addition to Scheduled Redeterminations, Borrower shall
be permitted to request a Special Redetermination of the Borrowing Base once in
each Fiscal Year. Such request shall be submitted to Administrative Agent and
Required Banks and at the time of such request Borrower shall deliver to each
Bank a Reserve Report. Together with such request, Borrower shall also notify
each Bank of the Borrowing Base requested by Borrower in connection with such
Special Redetermination.

                  (c) Any Special Redetermination shall be made by Banks in
accordance with the procedures and standards set forth in Section 5.2; provided,
that, no Reserve Report will be required to be delivered to Banks in connection
with any Special Determination requested by Required Banks pursuant to clause
(a) above.

         SECTION 5.4 Quarterly Reduction. Commencing on June 30, 2000 and
continuing on each Quarterly Date thereafter, the Borrowing Base in effect
hereunder shall reduce automatically and without notice to Borrower by the
Quarterly Reduction Amount then in effect.

         SECTION 5.5 Borrowing Base Deficiency. If a Borrowing Base Deficiency
exists after (a) giving effect to any Redetermination, or (b) as a result of any
Quarterly Reduction, Borrower shall be obligated to eliminate such Borrowing
Base Deficiency by making the mandatory prepayments of the Revolving Loans or
taking the actions required by Section 2.4.

         SECTION 5.6 Initial Borrowing Base. The Borrowing Base shall be
$7,000,000 for the period commencing on the Closing Date and ending on the
effective date of the first Redetermination after the Closing Date.

                                    ARTICLE 6
                            COLLATERAL AND GUARANTEES

         SECTION 6.1 Security.

                  (a) The Obligations shall be secured by first and prior Liens
(subject only to Permitted Encumbrances) covering and encumbering (i)
substantially all assets owned by Borrower

                                       36

<PAGE>   43

and each of its Subsidiaries, including, without limitation, all Mineral
Interests owned by Borrower and its Subsidiaries, and (ii) the outstanding
limited partnership interest in Borrower held by Taurus. On the Closing Date,
Borrower and Taurus shall deliver to Administrative Agent for the ratable
benefit of each Bank, a Pledge Agreement (to be executed by Taurus), a Security
Agreement and Mortgages (each to be executed by Borrower) in form and substance
acceptable to Administrative Agent and duly executed by Borrower and Taurus (as
applicable) together with such other assignments, conveyances, amendments,
agreements and other writings, including, without limitation, UCC-1 financing
statements (each duly authorized and executed) as Administrative Agent shall
deem necessary or appropriate to grant, evidence and perfect first and prior
Liens in substantially all assets owned by Borrower (including, without
limitation, all Mineral Interests owned by Borrower) and the limited partnership
interests in Borrower owned by Taurus.

                  (b) On or before each Redetermination Date and at such other
times as Administrative Agent or Required Banks shall request, Borrower shall
execute and deliver to Administrative Agent, and cause each of its Subsidiaries
to execute and deliver to Administrative Agent, for the ratable benefit of each
Bank, Mortgages granting, evidencing and perfecting the Liens required by
Section 6.1(a) preceding with respect to all Mineral Interests acquired by
Borrower or any Subsidiaries of Borrower on or subsequent to the last date on
which Borrower or any of its Subsidiaries were required to execute and deliver
Mortgages pursuant to this Section 6.1, or which, for any other reason are not
the subject of valid, enforceable, perfected first priority Liens (subject only
to Permitted Encumbrances) in favor of Administrative Agent for the ratable
benefit of Banks.

                  (c) On the date of the creation or acquisition by Borrower or
any Subsidiary of Borrower of any Subsidiary of Borrower (a "New Subsidiary"),
Borrower shall cause such New Subsidiary to execute and deliver to
Administrative Agent for the ratable benefit of the Banks, a Security Agreement
and one or more Mortgages, together with such other assignments, conveyances,
amendments, agreements and other writings, including, without limitations UCC-1
financing statements (each duly authorized and executed) as Administrative Agent
shall deem necessary or appropriate to grant, evidence and perfect first and
prior Liens on substantially all assets, including, without limitation, all
Mineral Interests, owed by such New Subsidiary.

         SECTION 6.2 Guarantees. The Obligations shall be jointly and severally
guaranteed by EXCO and each Subsidiary of Borrower pursuant to Facility
Guarantees duly executed and delivered by each such Person. On the date of the
creation or acquisition by Borrower or any Subsidiary of Borrower of any New
Subsidiary, Borrower shall cause such New Subsidiary to execute and deliver a
Facility Guaranty to Administrative Agent.

         SECTION 6.3 Supporting Documents. At any time Borrower or any of its
Subsidiaries are required to execute and deliver Mortgages, Security Agreements,
Pledge Agreements or Facility Guarantees to Administrative Agent pursuant to
this Article 6, Borrower shall also deliver or cause to be delivered to
Administrative Agent such other documents, instruments and agreements,
including, without limitation, certificates of officers of Borrower, Taurus,
EXCO, and Subsidiaries of Borrower, certificates of Governmental Authorities,
opinions of counsel (addressed to

                                       37

<PAGE>   44

Administrative Agent) and other documents, instruments and agreements
Administrative Agent shall deem necessary or appropriate to verify (i) the valid
organization and existence of the Credit Party executing and delivering such
Loan Papers, (ii) the due authorization, execution and delivery of such Loan
Papers, (iii) Taurus', EXCO's, Borrower's or such Subsidiaries' title to the
property (including Mineral Interests) purported to be subject to the Liens
created by such Loan Papers; provided, that, in the absence of any Default or
Borrowing Base Deficiency, Borrower shall not be required to provide opinions or
other evidence of title with respect to Mineral Interests with an aggregate
Recognized Value in excess of ninety percent (90%) of the aggregate Recognized
Value of all Mineral Interests owned by Borrower (such limitation is referred to
herein as the "Title Review Limit"); and (iv) the validity, perfection and
priority of the Liens created by such Loan Papers and such other matters related
thereto as Administrative Agent shall reasonably request.

                                    ARTICLE 7
                              CONDITIONS PRECEDENT

         SECTION 7.1 Conditions to Initial Borrowing and Participation in Letter
of Credit Exposure. The obligation of each Bank to loan its Commitment
Percentage of the initial Borrowing made hereunder, and the obligation of
Administrative Agent to issue (or cause another Bank to issue) the initial
Letter of Credit issued hereunder is subject to the satisfaction of each of the
following conditions prior to or simultaneously with the initial Borrowing made
hereunder:

                  (a) Closing Deliveries. Administrative Agent shall have
received each of the following documents, instruments and agreements, each of
which shall be in form and substance and executed in such counterparts as shall
be acceptable to Administrative Agent and each Bank and each of which shall,
unless otherwise indicated, be dated the Closing Date:

                  (i) a Note payable to the order of each Bank, each in the
                  amount of such Bank's Commitment, duly executed by Borrower;

                  (ii) Mortgages duly executed and delivered by Borrower
                  creating first and prior Liens on all Mineral Interests owned
                  by Borrower, including, without limitation, the Nebraska
                  Properties;

                  (iii) a Security Agreement duly executed and delivered by
                  Borrower;

                  (iv) a Pledge Agreement duly executed by Taurus;

                  (v) such financing statements on form UCC-1 (or any other form
                  required by Lender in its reasonable discretion) as
                  Administrative Agent shall require to evidence and perfect the
                  Liens created by the Mortgages, Pledge Agreement and the
                  Security Agreement referenced in clauses (ii),(iii) and (iv)
                  above, each of which shall be

                                       38

<PAGE>   45

                  executed and delivered by Borrower or Taurus (as applicable)
                  and filed of record in such jurisdictions as Administrative
                  Agent shall require in its sole discretion;

                  (vi) Facility Guaranty duly executed and delivered by EXCO;

                  (vii) a copy of the Articles of Incorporation and all
                  amendments thereto of EXCO and Taurus accompanied by a
                  certificate that such copy is true, correct and complete, and
                  dated within ten (10) days of the Closing Date, issued by the
                  appropriate Governmental Authority of the jurisdiction of
                  incorporation or organization of each of EXCO and Taurus and
                  accompanied by a certificate of the Secretary or comparable
                  Authorized Officer of EXCO that such copy is true, correct and
                  complete on the Closing Date;

                  (viii) a copy of the Bylaws and all amendments thereto of each
                  of EXCO and Taurus accompanied by a certificate of the
                  Secretary or comparable Authorized Officer of EXCO and Taurus
                  that such copy is true, correct and complete as of the date
                  hereof;

                  (ix) a copy of the Certificate of Formation and all amendments
                  thereto of Borrower accompanied by a certificate that such
                  copy is true, correct and complete and dated within ten (10)
                  days of the Closing Date, issued by the appropriate
                  Governmental Authority of the jurisdiction of incorporation or
                  organization of Borrower, and accompanied by a certificate of
                  the Secretary or comparable Authorized Officer of Borrower
                  that such copy is true, correct and complete on the Closing
                  Date;

                  (x) a copy of the Limited Partnership Agreement for Borrower
                  together with a certificate from an Authorized Officer of
                  Borrower stating that such copy is a true and correct copy of
                  the Limited Partnership Agreement for Borrower and that such
                  Limited Partnership Agreement has not been amended or modified
                  in any respect and is in full force and effect on the Closing
                  Date;

                  (xi) certain certificates and other documents issued by the
                  appropriate Governmental Authorities of such jurisdictions as
                  Administrative Agent has requested relating to the existence
                  of each of EXCO, Taurus and Borrower and to the effect that of
                  each of EXCO, Taurus and Borrower is in good standing with
                  respect to the payment of franchise and similar Taxes and is
                  duly qualified to transact business in such jurisdictions;

                  (xii) a certificate of incumbency of all officers of each of
                  EXCO, Taurus and Borrower who will be authorized to execute or
                  attest to any Loan Paper on behalf of EXCO, Taurus or Borrower
                  dated the date hereof, executed by the Secretary or comparable
                  Authorized Officer of such Person;

                                       39

<PAGE>   46

                  (xiii) copies of resolutions or comparable authorizations
                  approving the Loan Papers and authorizing the transactions
                  contemplated by this Agreement and the other Loan Papers, duly
                  adopted by the Board of Directors of each of EXCO and Taurus
                  and the Partners of Borrower; accompanied by certificates of
                  the Secretary or comparable Authorized Officer of each of
                  EXCO, Taurus and Borrower that such copies are true and
                  correct copies of resolutions duly adopted at a meeting of or
                  (if permitted by applicable Law and, if required by such Law,
                  by the Bylaws of EXCO or Taurus and the Limited Partnership
                  Company Agreement of Borrower) by the unanimous written
                  consent of the Board of Directors of each of EXCO and Taurus
                  and the Partners of Borrower; and that such resolutions
                  constitute all the resolutions adopted with respect to such
                  transactions, have not been amended, modified, or revoked in
                  any respect, and are in full force and effect as of the date
                  hereof;

                  (xiv) an opinion of Haynes & Boone, L.L.P., counsel for
                  Borrower, EXCO and Taurus, dated the date hereof, favorably
                  opining as to the enforceability of each of the Loan Papers
                  and otherwise in form and substance satisfactory to
                  Administrative Agent and Banks;

                  (xv) such UCC-11 search reports as Administrative Agent shall
                  require, prepared as of a date not more than twenty (20) days
                  prior to the Closing Date, conducted in such jurisdictions and
                  reflecting such names as Administrative Agent shall request;

                  (xvi) a certificate signed by an Authorized Officer of
                  Borrower stating that (A) the representations and warranties
                  contained in this Agreement and the other Loan Papers are true
                  and correct in all material respects, (B) no Default or Event
                  of Default has occurred and is continuing, and (C) all
                  conditions set forth in this Section 7.1 and Section 7.2 have
                  been satisfied;

                  (xvii) a Certificate of Ownership Interests signed by an
                  Authorized Officer of Borrower in the form of Exhibit H
                  attached hereto;

                  (xviii) a report or reports in form, scope and detail
                  acceptable to Administrative Agent from environmental
                  engineering firms acceptable to Administrative Agent setting
                  forth the results of a current phase I environmental review of
                  the Mineral Interests, which report(s) shall not reflect the
                  existence of facts or circumstances which would constitute a
                  material violation of any Applicable Environmental Law or
                  which are likely to result in a material liability to Borrower
                  or any of its Subsidiaries; and

                  (xix) certificates from Borrower's insurance broker setting
                  forth the insurance maintained by Borrower, stating that such
                  insurance is in full force and effect, that all premiums due
                  have been paid and stating that such insurance is adequate and
                  complies with the requirements of Section 9.6.

                                       40

<PAGE>   47

                  (b) Title Review. Administrative Agent or its counsel shall
have completed a review of title (including opinions of title) to the Nebraska
Properties (subject to the Title Review Limit), and such review shall not have
revealed any condition or circumstance which would reflect that the
representations and warranties contained in Section 8.9 hereof are inaccurate in
any respect.

                  (c) Amendment of Limited Partnership Agreement. Borrower's
Limited Partnership Agreement shall have been amended and restated on terms and
conditions acceptable to Administrative Agent such that after giving effect
thereto (i) Taurus will own on a fully diluted basis at least fifty percent
(50%) of the limited partnership interests in Borrower free and clear of all
Liens, and (ii) EXCO will own on a fully diluted basis one hundred percent
(100%) of the general partnership interests in Borrower free and clear of all
Liens.

                  (d) Partner Contributions. EXCO directly or indirectly through
Taurus shall have contributed at least $3,500,000 in cash to the partnership
capital of Borrower.

                  (e) Completion of Nebraska Acquisition. Borrower shall have
completed (or simultaneously with the funding of the initial Borrowing
hereunder, Borrower shall complete) the Nebraska Acquisition for a total
purchase price of not more than $10,200,000 and otherwise on the terms and
conditions substantially in accordance with the Nebraska Acquisition Agreement
as in effect on the date hereof, and as a result thereof Borrower shall have
acquired, or simultaneously with the funding of such Borrowing Borrower shall
acquire, good and defensible title to all such Nebraska Properties, free and
clear of all Liens except Permitted Encumbrances.

                  (f) No Material Adverse Change. In the sole discretion of each
Bank, since January 1, 2000, no Material Adverse Change shall have occurred.

                  (g) No Legal Prohibition. The transactions contemplated by
this Agreement shall be permitted by applicable Law and regulation and shall not
subject Administrative Agent, any Bank, or any Credit Party to any Material
Adverse Change.

                  (h) No Litigation. No litigation, arbitration or similar
proceeding shall be pending or threatened which calls into question the validity
or enforceability of this Agreement, the other Loan Papers or the transactions
contemplated hereby or thereby.

                  (i) Closing Fees. Borrower shall have paid to Administrative
Agent for the ratable benefit of each Bank, and shall have paid to
Administrative Agent, the fees to be paid on the Closing Date pursuant to
Section 2.12.

                  (j) Other Matters. All matters related to this Agreement, the
other Loan Papers and the Credit Parties shall be acceptable to each Bank in its
sole discretion, and Borrower shall have delivered to Administrative Agent and
each Bank such evidence as they shall request to substantiate any matters
related to this Agreement and the other Loan Papers, as Administrative Agent or
any Bank shall request.

                                       41

<PAGE>   48

         SECTION 7.2 Conditions to Each Borrowing and each Letter of Credit. The
obligation of each Bank to loan its Commitment Percentage of each Borrowing and
the obligation of Administrative Agent to issue a Letter of Credit on the date
such Letter of Credit is to be issued is subject to the further satisfaction of
the following conditions:

                  (a) timely receipt by Administrative Agent of a Request for
Borrowing or a Request for Letter of Credit (as applicable);

                  (b) immediately before and after giving effect to such
Borrowing or issuance of such Letter of Credit, no Default or Event of Default
shall have occurred and be continuing and the funding of such Borrowing or the
issuance of the requested Letter of Credit (as applicable) shall not cause a
Default or Event of Default;

                  (c) the representations and warranties of Borrower contained
in this Agreement and the other Loan Papers shall be true and correct in all
material respects on and as of the date of such Borrowing or issuance of such
Letter of Credit (as applicable), with the same effect as though such
representations and warranties had been made on and as of the date of such
Borrowing or issuance of such Letter of Credit (as applicable) or, if such
representations and warranties are expressly limited to particular dates, as of
such particular dates;

                  (d) after giving effect to such Borrowing or issuance of such
Letter of Credit, the Outstanding Credit shall not exceed the Borrowing Base;

                  (e) no Material Adverse Change shall have occurred;

                  (f) the funding of such Borrowing or the issuance of such
Letter of Credit (as applicable) shall be permitted by applicable Law; and

                  (g) such Borrowing in such Letter of Credit shall be used only
for a purpose permitted under the Agreement.

The funding of each Borrowing and the issuance of each Letter of Credit
hereunder shall be deemed to be a representation and warranty by Borrower on the
date of such Borrowing and the date of issuance of each Letter of Credit as to
the facts specified in Sections 7.2(b) through 7.2(e).

         SECTION 7.3 Materiality of Conditions. Each condition precedent herein
is material to the transactions contemplated herein, and time is of the essence
in respect of each thereof.

                                       42

<PAGE>   49

                                    ARTICLE 8
                         REPRESENTATIONS AND WARRANTIES

         Borrower represents and warrants to Administrative Agent and each Bank
that each of the following statements is true and correct on the date hereof,
and will be true and correct on the occasion of each Borrowing and the issuance
of each Letter of Credit:

         SECTION 8.1 Existence and Power. Each Credit Party (a) is a
corporation, limited liability company or partnership duly incorporated or
organized (as applicable), validly existing and in good standing under the laws
of its jurisdiction of incorporation or organization (as applicable), (b) has
all corporate, limited liability company or partnership power (as applicable)
and all material governmental licenses, authorizations, consents and approvals
required to carry on its businesses as now conducted and as proposed to be
conducted, and (c) is duly qualified to transact business as a foreign
corporation, foreign limited liability company or foreign partnership (as
applicable) in each jurisdiction where a failure to be so qualified could result
in a Material Adverse Change.

         SECTION 8.2 Necessary Authorization; Contravention. The execution,
delivery and performance of this Agreement and the other Loan Papers by each
Credit Party (to the extent each Credit Party is a party thereto), are within
such Credit Party's corporate, limited liability company or partnership power,
have been duly authorized by all necessary corporate, limited liability company
or partnership action, require no action by or in respect of, or filing with,
any Governmental Authority and do not contravene, or constitute a default under,
any provision of applicable Law (including, without limitation, the Margin
Regulations) or of the articles or certificate of incorporation, bylaws,
partnership agreement, limited liability company agreement or other
organizational documents of any Credit Party, or of any agreement, judgment,
injunction, order, decree or other instrument binding upon any Credit Party or
result in the creation or imposition of any Lien on any asset of any Credit
Party other than the Liens securing the Obligations.

         SECTION 8.3 Binding Effect. This Agreement constitutes a valid and
binding agreement of Borrower; the other Loan Papers when executed and delivered
in accordance with this Agreement, will constitute the valid and binding
obligations of each Credit Party (to the extent each Credit Party is a party
thereto), and each Loan Paper is, or when executed and delivered, will be,
enforceable against each Credit Party (to the extent each Credit Party is a
party thereto), in accordance with its terms except as (i) the enforceability
thereof may be limited by bankruptcy, insolvency or similar laws affecting
creditors rights generally, and (ii) the availability of equitable remedies may
be limited by equitable principles of general applicability.

         SECTION 8.4 Financial Information.

                  (a) The most recent annual audited consolidated balance sheets
of each of Borrower, EXCO and Taurus and the related consolidated statements of
operations and cash flows for the Fiscal Year then ended, copies of which have
been delivered to each Bank, fairly present, in conformity with GAAP, the
consolidated financial position of each of Borrower, EXCO and Taurus

                                       43

<PAGE>   50

as of the end of such Fiscal Year and its consolidated results of operations and
cash flows for such Fiscal Year. (Notwithstanding the foregoing, the
representation and warranty contained in this Section 8.4(a) will not be deemed
to be made with respect to Borrower and Taurus until such time as annual audited
consolidated balance sheets, statements of operations and cash flows for
Borrower for the Fiscal Year ended December 31, 2000 are delivered to each Bank
in accordance with Section 9.1(a)).

                  (b) The most recent quarterly unaudited consolidated balance
sheet of Borrower, EXCO and Taurus delivered to Banks, and the related unaudited
consolidated statements of operations and cash flows for the portion of
Borrower's, EXCO's and Taurus's Fiscal Year then ended, fairly present, in
conformity with GAAP applied on a basis consistent with the financial statements
referred to in Section 8.4(a), the consolidated financial position of Borrower,
EXCO and Taurus as of such date and its consolidated results of operations and
cash flows for such portion of Borrower's, EXCO's and Taurus's Fiscal Year.
(Notwithstanding the foregoing, the representation and warranty contained in
this Section 8.4(b) will not be deemed to be made with respect to Borrower until
such time as quarterly unaudited consolidated balance sheets, statements of
operations and cash flows for Borrower for the Fiscal Quarter ending March 31,
2000 are delivered to each Bank in accordance with Section 9.1(b)).

                  (c) No Material Adverse Change has occurred.

                  (d) After giving effect to the transactions contemplated by
this Agreement, (i) the fair value of the property of each Credit Party is
greater than the total amount of liabilities, including, without limitation,
contingent liabilities, of each Credit Party , (ii) the present fair saleable
value of the assets of each Credit Party is not less than the amount that will
be required to pay the liability of such Credit Party on its debts as they
become absolute and matured, (iii) each Credit Party is able to realize upon its
assets and pay its debts and other liabilities, contingent obligations and other
commitments as they mature in the normal course of business, (iv) no Credit
Party intends to, and no Credit Party believes that it will, incur debts or
liabilities beyond its ability to pay as such debts and liabilities mature, and
(v) no Credit Party is engaged in a business or transaction, and no Credit Party
is about to engage in business or a transaction for which such Credit Party's
property would constitute unreasonably small capital after giving due
consideration to the prevailing practice in the industry in which such Credit
Party is engaged.

                  (e) Borrower was formed on February 17, 2000 for the purpose
of acquiring and developing the Nebraska Properties and producing and marketing
Hydrocarbons therefrom. Prior to giving effect to the acquisition of the
Nebraska Properties, Borrower had no assets, operations, employees or
liabilities of any nature (contingent or otherwise) other than rights and
obligations arising under the Nebraska Acquisition Agreement, this Agreement and
the other Loan Papers.

         SECTION 8.5 Litigation. Except for matters disclosed on Schedule 2
attached hereto, there is no action, suit or proceeding pending against, or to
the knowledge of Borrower, threatened against or affecting Borrower or any of
its Subsidiaries before any Governmental Authority in which there

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<PAGE>   51

is a reasonable possibility of an adverse decision which could result in a
Material Adverse Change or which could in any manner draw into question the
validity of the Loan Papers.

         SECTION 8.6 ERISA. Neither Borrower nor any ERISA Affiliate of Borrower
maintains or has ever maintained or been obligated to contribute to any Plan
covered by Title IV of ERISA or subject to the funding requirements of Section
412 of the Code or Section 302 of ERISA. Each Plan maintained by Borrower or any
ERISA Affiliate of Borrower is in compliance in all material respects with all
applicable Laws. Except in such instances where an omission or failure would not
result in a Material Adverse Change on the business, financial condition or
prospects of Borrower, (a) all returns, reports and notices required to be filed
with any regulatory agency with respect to any Plan have been filed timely, and
(b) neither Borrower nor any ERISA Affiliate of Borrower has failed to make any
contribution or pay any amount due or owing as required by the terms of any
Plan. There are no pending or, to the best of Borrower's knowledge, threatened
claims, lawsuits, investigations or actions (other than routine claims for
benefits in the ordinary course) asserted or instituted against, and neither
Borrower nor any ERISA Affiliate of Borrower has knowledge of any threatened
litigation or claims against, the assets of any Plan or its related trust or
against any fiduciary of a Plan with respect to the operation of such Plan that
are likely to result in liability of Borrower causing a Material Adverse Change.
Except in such instances where an omission or failure would not result in a
Material Adverse Change, each Plan that is intended to be "qualified" within the
meaning of section 401(a) of the Code is, and has been during the period from
its adoption to date, so qualified, both as to form and operation and all
necessary governmental approvals, including a favorable determination as to the
qualification under the Code of such Plan and each amendment thereto, have been
or will be timely obtained. Neither Borrower nor any ERISA Affiliate of Borrower
has engaged in any prohibited transactions, within the meaning of section 406 of
ERISA or section 4975 of the Code, in connection with any Plan which would
result in liability of Borrower causing a Material Adverse Change. Neither
Borrower nor any ERISA Affiliate of Borrower maintains or contributes to any
Plan that provides a post-employment health benefit, other than a benefit
required under Section 601 of ERISA, or maintains or contributes to a Plan that
provides health benefits that is not fully funded except where the failure to
fully fund such Plan would not result in a Material Adverse Change. Neither
Credit Party nor any ERISA Affiliate of Borrower maintains, has established or
has ever participated in a multiple employer welfare benefit arrangement within
the meaning of section 3(40)(A) of ERISA.

         SECTION 8.7 Taxes and Filing of Tax Returns. Borrower and each of its
Subsidiaries has filed all tax returns required to have been filed and has paid
all Taxes shown to be due and payable on such returns, including interest and
penalties, and all other Taxes which are payable by such party, to the extent
the same have become due and payable. Borrower does not know of any proposed
material Tax assessment against it or any of its Subsidiaries and all Tax
liabilities of Borrower and its Subsidiaries are adequately provided for. Except
as disclosed in writing to Banks prior to the date hereof, no income tax
liability of Borrower or any of its Subsidiaries has been asserted by the
Internal Revenue Service or other Governmental Authority for Taxes in excess of
those already paid.

                                       45

<PAGE>   52

         SECTION 8.8 Ownership of Properties Generally. Borrower and each of its
Subsidiaries has good and valid fee simple or leasehold title to all material
properties and assets purported to be owned by it, including, without
limitation, all assets reflected in the balance sheets referred to in Section
8.4(a) and 8.4(b) and all assets which are used by Borrower and its Subsidiaries
in the operation of their respective businesses, and none of such properties or
assets is subject to any Lien other than Permitted Encumbrances.

         SECTION 8.9 Mineral Interests. Borrower has good and defensible title
to all Mineral Interests described in the Reserve Report, including, after
giving effect to the Nebraska Acquisition, the Nebraska Properties, free and
clear of all Liens except Permitted Encumbrances. All such Mineral Interests are
valid, subsisting, and in full force and effect, and all rentals, royalties, and
other amounts due and payable in respect thereof have been duly paid. Without
regard to any consent or non-consent provisions of any joint operating agreement
covering any of Borrower's Proved Mineral Interests, Borrower's share of (a) the
costs for each Proved Mineral Interest described in the Reserve Report is not
greater than the decimal fraction set forth in the Reserve Report, before and
after payout, as the case may be, and described therein by the respective
designations "working interests", "WI", "gross working interest", "G.I.", or
similar terms, and (b) production from, allocated to, or attributed to each such
Proved Mineral Interest is not less than the decimal fraction set forth in the
Reserve Report, before and after payout, as the case may be, and described
therein by the designations net revenue interest, NHI, or similar terms. Each
well drilled in respect of each Proved Producing Mineral Interest described in
the Reserve Report (y) is capable of, and is presently, producing Hydrocarbons
in commercially profitable quantities, and Borrower is currently receiving
payments for its share of production, with no funds in respect of any thereof
being presently held in suspense, other than any such funds being held in
suspense pending delivery of appropriate division orders, and (z) has been
drilled, bottomed, completed, and operated in compliance with all applicable
Laws and no such well which is currently producing Hydrocarbons is subject to
any penalty in production by reason of such well having produced in excess of
its allowable production.

         SECTION 8.10 Licenses, Permits, Etc. Borrower and each of its
Subsidiaries possesses such valid franchises, certificates of convenience and
necessity, operating rights, licenses, permits, consents, authorizations,
exemptions and orders of Governmental Authorities, as are necessary to carry on
its business as now conducted and as proposed to be conducted, except to the
extent a failure to obtain any such item would not result in a Material Adverse
Change.

         SECTION 8.11 Compliance with Law. The business and operations of
Borrower and its Subsidiaries have been and are being conducted in accordance
with all applicable Laws other than violations of Laws which do not (either
individually or collectively) result in a Material Adverse Change.

         SECTION 8.12 Full Disclosure. All information heretofore furnished by
any Credit Party to Administrative Agent or any Bank for purposes of or in
connection with this Agreement, any Loan Paper or any transaction contemplated
hereby or thereby is, and all such information hereafter furnished by or on
behalf of Borrower to Administrative Agent or any Bank will be, true, complete

                                       46

<PAGE>   53

and accurate in every material respect. Borrower has disclosed or has caused to
be disclosed to Banks in writing any and all facts (other than facts of general
public knowledge) which might reasonably be expected to result in a Material
Adverse Change.

         SECTION 8.13 Organizational Structure; Nature of Business. Borrower is
engaged only in the business of acquiring, owning, exploring, developing and
operating the Nebraska Properties and other Mineral Interests contained in the
AMI (as defined in the Amended and Restated Agreement of Limited Partnership of
Humphrey-Hill, L.P. dated March 24, 2000), and the production, marketing,
processing and transporting of Hydrocarbons therefrom. Schedule 3 hereto
accurately reflects (i) the jurisdiction of organization of Borrower, (ii) each
jurisdiction in which Borrower is qualified to transact business as a foreign
limited partnership, (iii) the authorized, issued and outstanding limited
partnership interests of Borrower (and the legal and beneficial owners of such
interests), and (iv) all outstanding warrants, options, subscription rights,
convertible securities or other rights to purchase limited partnership interests
of Borrower. Borrower has no Subsidiaries on the Closing Date.

         SECTION 8.14 Environmental Matters. No operation conducted by Borrower
or any Subsidiary of Borrower and no real or personal property now or previously
owned or leased by Borrower or any Subsidiary of Borrower (including, without
limitation, the Nebraska Properties) and no operations conducted thereon, and to
Borrower's knowledge, no operations of any prior owner, lessee or operator of
any such properties, is or has been in violation of any Applicable Environmental
Law other than violations which neither individually nor in the aggregate could
result in a Material Adverse Change. Neither Borrower, any Subsidiary of
Borrower, nor any such property or operation is the subject of any existing,
pending or, to Borrower's knowledge, threatened Environmental Complaint which
could, individually or in the aggregate, result in Material Adverse Change. All
notices, permits, licenses, and similar authorizations, required to be obtained
or filed in connection with the ownership of each tract of real property or
operations of Borrower or any Subsidiary of Borrower thereon and each item of
personal property owned, leased or operated by Borrower or any Subsidiary of
Borrower, including, without limitation, notices, licenses, permits and
authorizations required in connection with any past or present treatment,
storage, disposal, or release of Hazardous Substances into the environment, have
been duly obtained or filed except to the extent the failure to obtain or file
such notices, licenses, permits and authorizations would not result in a
Material Adverse Change. All Hazardous Substances, generated at each tract of
real property and by each item of personal property owned, leased or operated by
Borrower or any Subsidiary of Borrower have been transported, treated, and
disposed of only by carriers or facilities maintaining valid permits under RCRA
and all other Applicable Environmental Laws for the conduct of such activities
except in such cases where the failure to obtain such permits could not,
individually or in the aggregate, result in a Material Adverse Change. There
have been no Hazardous Discharges which were not in compliance with Applicable
Environmental Laws other than Hazardous Discharges which would not, individually
or in the aggregate, result in a Material Adverse Change. Neither Borrower nor
any Subsidiary of Borrower has any contingent liability in connection with any
Hazardous Discharge which could reasonably be expected to result in a Material
Adverse Change.

                                       47

<PAGE>   54

         SECTION 8.15 Burdensome Obligations. Neither Borrower, nor any
Subsidiary of Borrower, nor any of their respective properties is subject to any
Law or any pending or threatened change of Law or subject to any restriction
under its articles (or certificate) of incorporation, bylaws, regulations,
partnership agreement or comparable charter or other organizational documents or
under any agreement or instrument to which Borrower or any Subsidiary of
Borrower or by which Borrower or any Subsidiary of Borrower or any of their
respective properties may be subject or bound, which is so unusual or burdensome
as to be likely in the foreseeable future to result in a Material Adverse
Change. Without limiting the foregoing, neither Borrower nor any Subsidiary of
Borrower is a party to or bound by any agreement or subject to any order of any
Governmental Authority which prohibits or restricts in any way the right of
Borrower or any Subsidiary of Borrower to make Distributions.

         SECTION 8.16 Fiscal Year. Borrower's Fiscal Year is January 1 through
December 31.

         SECTION 8.17 No Default. Neither a Default nor an Event of Default has
occurred or will exist after giving effect to the transactions contemplated by
this Agreement or the other Loan Papers.

         SECTION 8.18 Government Regulation. Neither Borrower nor any Subsidiary
of Borrower is subject to regulation under the Public Utility Holding Company
Act of 1935, the Federal Power Act, the Interstate Commerce Act (as any of the
preceding acts have been amended), the Investment Company Act of 1940 or any
other law which regulates the incurring by Borrower or any Subsidiary of
Borrower of Debt, including, but not limited to laws relating to common contract
carriers or the sale of electricity, gas, steam, water or other public utility
services.

         SECTION 8.19 Insider. Neither Borrower nor any Subsidiary of Borrower
is, and no Person having "control" (as that term is defined in 12 U.S.C. Section
375(b) or regulations promulgated thereunder) of Borrower or any Subsidiary of
Borrower is an "executive officer", "director" or "shareholder" of any Bank or
any bank holding company of which any Bank is a Subsidiary or of any Subsidiary
of such bank holding company.

         SECTION 8.20 Gas Balancing Agreements and Advance Payment Contracts. On
the date of this Agreement, (a) there is no Material Gas Imbalance, and (b) the
aggregate amount of all Advance Payments received by Borrower under Advance
Payment Contracts which have not been satisfied by delivery of production does
not exceed $50,000.

         SECTION 8.21 Nebraska Acquisition Documents. Borrower has provided each
Bank with a true and correct copy of each of the Nebraska Acquisition Documents
including all amendments and modifications thereto. No material rights or
obligations of any party to any of such Nebraska Acquisition Documents have been
waived and neither Borrower nor any of its Subsidiaries, nor to the best
knowledge of Borrower or any other party to any of such Nebraska Acquisition
Documents, is in default of its obligations thereunder. Each of the Nebraska
Acquisition Documents is a valid, binding and enforceable obligation of the
parties thereto in accordance with its terms and is in full force and effect.
Each representation and warranty made by Borrower, and to the best knowledge

                                       48

<PAGE>   55

of Borrower, by Sellers in the Nebraska Acquisition Agreement and the other
Nebraska Acquisition Documents (a) was true and correct when made, and (b) will
be true and correct on the Closing Date.

                                    ARTICLE 9
                              AFFIRMATIVE COVENANTS

         Borrower covenants and agrees that, so long as any Bank has any
commitment to lend or participate in Letter of Credit Exposure hereunder or any
amount payable under any Note remains unpaid or any Letter of Credit remains
outstanding:

         SECTION 9.1 Information. Borrower will deliver, or cause to be
delivered, to each Bank:

                  (a) as soon as available and in any event within one hundred
twenty (120) days after the end of each Fiscal Year, a consolidated balance
sheet of each of Borrower, EXCO and Taurus as of the end of such Fiscal Year and
the related consolidated statements of income and statements of cash flow for
such Fiscal Year, setting forth in each case in comparative form the figures for
the previous Fiscal Year, all reported by Borrower, EXCO and Taurus in
accordance with GAAP and audited by a firm of independent public accountants of
nationally recognized standing and acceptable to Administrative Agent;

                  (b) (i) as soon as available and in any event within
forty-five (45) days after the end of each of the first three (3) Fiscal
Quarters of each Fiscal Year, consolidated balance sheets of Borrower, EXCO and
Taurus as of the end of such Fiscal Quarter and the related consolidated
statements of income and statements of cash flow for such quarter and for the
portion of Borrower's, EXCO's and Taurus's Fiscal Year ended at the end of such
Fiscal Quarter, setting forth in each case in comparative form the figures for
the corresponding quarter and the corresponding portion of Borrower's, EXCO's
and Taurus's previous Fiscal Year;

                  (c) simultaneously with the delivery of each set of financial
statements referred to in Sections 9.1(a) and 9.1(b), a certificate of a
Financial Officer of each of EXCO and Borrower in the form of Exhibit I-1 or I-2
(as applicable) attached hereto, (i) setting forth, in the case of the
certificate delivered by the Financial Officer of Borrower, in reasonable detail
the calculations required to establish whether Borrower was in compliance with
the requirements of Article 11 on the date of such financial statements, (ii)
stating whether there exists on the date of such certificate any Default and, if
any Default then exists, setting forth the details thereof and the action which
the Credit Parties are taking or propose to take with respect thereto, (iii)
stating whether or not such financial statements fairly reflect in all material
respects the results of operations and financial condition of Borrower, EXCO and
Taurus as of the date of the delivery of such financial statements and for the
period covered thereby, (iv) setting forth (A) whether as of such date there is
a Material Gas Imbalance and, if so, setting forth the amount of net gas
imbalances under Gas Balancing Agreements to which Borrower or any of its
Subsidiaries is a party or by which any Mineral Interests owned by Borrower or
any of its Subsidiaries are bound, and (B) the aggregate amount of all Advance

                                       49

<PAGE>   56

Payments received under Advance Payment Contracts to which Borrower or any of
its Subsidiaries is a party or by which any Mineral Interests owned by Borrower
or any of its Subsidiaries are bound which have not been satisfied by delivery
of production, if any, and (v) a summary of the Hedge Transactions to which
Borrower or any of its Subsidiaries is a party on such date;

                  (d) as soon as available and in any event within forty-five
(45) days after the end of each Fiscal Quarter, a report of Borrower's Financial
Officer setting forth in reasonable detail Borrower's Net Revenues for the
preceding Fiscal Quarter;

                  (e) promptly upon the delivery thereof to Borrower's partners
or their Affiliates generally, copies of all financial statements, material
reports and proxy statements so mailed;

                  (f) promptly upon the filing thereof, copies of all final
registration statements, post effective amendments thereto and annual, quarterly
or special reports which any Credit Party shall have filed with the Securities
and Exchange Commission; provided that Borrower must deliver, or cause to be
delivered, any annual reports which any Credit Party shall have filed with the
Securities and Exchange Commission, within ninety (90) days after the end of
each Fiscal Year of such Credit Party, and any quarterly reports which Borrower
shall have filed with the Securities and Exchange Commission, within forty-five
(45) days after the end of each of the first three (3) Fiscal Quarters of each
Fiscal Year of such Credit Party;

                  (g) promptly upon receipt of same, any notice or other
information received by Borrower or any Subsidiary of Borrower indicating any
potential, actual or alleged (i) non- compliance with or violation of the
requirements of any Applicable Environmental Law which could result in liability
to Borrower or any Subsidiary of Borrower for fines, clean up or any other
remediation obligations or any other liability in excess of $100,000 in the
aggregate; (ii) threatened Hazardous Discharge which Hazardous Discharge would
impose on Borrower or any Subsidiary of Borrower a duty to report to a
Governmental Authority or to pay cleanup costs or to take remedial action under
any Applicable Environmental Law which could result in liability to Borrower or
any Subsidiary of Borrower for fines, clean up and other remediation obligations
or any other liability in excess of $100,000 in the aggregate; or (iii) the
existence of any Lien arising under any Applicable Environmental Law securing
any obligation to pay fines, clean up or other remediation costs or any other
liability in excess of $100,000 in the aggregate. Without limiting the
foregoing, Borrower or any Subsidiary of Borrower shall provide to Banks
promptly upon receipt of same by Borrower or any Subsidiary of Borrower copies
of all environmental consultants or engineers reports received by Borrower or
any Subsidiary of Borrower which would render the representation and warranty
contained in Section 8.14 untrue or inaccurate in any respect;

                  (h) in the event any notification is provided to any Bank or
Administrative Agent pursuant to Section 9.1(f) hereof or Administrative Agent
or any Bank otherwise learns of any event or condition under which any such
notice would be required, then, upon request of Required Banks, Borrower shall
within thirty (30) days of such request, cause to be furnished to Administrative
Agent and each Bank a report by an environmental consulting firm acceptable to
Administrative Agent and

                                       50

<PAGE>   57

Required Banks, stating that a review of such event, condition or circumstance
has been undertaken (the scope of which shall be acceptable to Administrative
Agent and Required Banks) and detailing the findings, conclusions and
recommendations of such consultant. Borrower shall bear all expenses and costs
associated with such review and updates thereof;

                  (i) immediately upon any Authorized Officer becoming aware of
the occurrence of any Default, a certificate of an Authorized Officer setting
forth the details thereof and the action which Borrower is taking or proposes to
take with respect thereto;

                  (j) no later than March 1, and September 1 of each year,
reports of production volumes, revenue, expenses and product prices for all
Mineral Interests owned by Borrower for the periods of six (6) months ending the
preceding December 31, and June 30, respectively; such reports shall be prepared
on an accrual basis and shall be reported on a field by field basis;

                  (k) promptly notify Banks of any Material Adverse Change;

                  (l) on or before May 24, 2000 an engineering analysis of the
Nebraska Properties in form and substance satisfactory to Administrative Agent
and prepared by Lee Keeling and Associates, Inc.; and

                  (m) from time to time such additional information regarding
the financial position or business of Borrower and its Subsidiaries as
Administrative Agent, at the request of any Bank, may reasonably request.

         SECTION 9.2. Business of Borrower. The sole business of Borrower is and
shall continue to be solely the acquisition, ownership, exploration, development
and operation of the Nebraska Properties and other Mineral Interests contained
in the AMI (as defined in the Amended and Restated Agreement of Limited
Partnership of Humphrey-Hill, L.P. dated March 24, 2000), and the production,
marketing, processing and transportation of Hydrocarbons therefrom.

         SECTION 9.3 Maintenance of Existence. Borrower shall, and shall cause
each Credit Party to, at all times (a) maintain its corporate, partnership or
limited liability company existence in its state of incorporation or
organization, and (b) maintain its good standing and qualification to transact
business in all jurisdictions where the failure to maintain good standing or
qualification to transact business could result in a Material Adverse Change.

         SECTION 9.4 Title Data. In addition to the title information required
by Article 7, but subject to the Title Review Limit, Borrower shall, upon the
request of Required Banks, cause to be delivered to Administrative Agent such
title opinions and other information regarding title to Mineral Interests owned
by Borrower and the perfection and priority of Administrative Agent's Liens
therein as are appropriate to determine the status thereof.

                                       51

<PAGE>   58

         SECTION 9.5 Right of Inspection. Borrower will permit, and will cause
each of its Subsidiaries to permit, any officer, employee or Administrative
Agent of Administrative Agent or of any Bank to visit and inspect any of the
assets of Borrower and its Subsidiaries, examine Borrower's and its
Subsidiaries' books of record and accounts, take copies and extracts therefrom,
and discuss the affairs, finances and accounts of Borrower and its Subsidiaries
with Borrower's and its Subsidiaries' officers, accountants and auditors, all at
such reasonable times and as often as Administrative Agent or any Bank may
reasonably request, all at the expense of Borrower; provided, that, in the
absence of a Default or Event of Default, neither Administrative Agent nor any
Bank will require Borrower to incur any unreasonable cost or expense under this
Section 9.5.

         SECTION 9.6 Maintenance of Insurance. Borrower will, and will cause
each of its Subsidiaries to, at all times maintain or cause to be maintained
insurance covering such risks as are customarily carried by businesses similarly
situated, including, without limitation, the following: (a) workmen's
compensation insurance; (b) employer's liability insurance; (c) comprehensive
general public liability and property damage insurance; (d) comprehensive
automobile liability insurance, and (e) such other perils as are customarily
insured against in the oil and gas industry. All loss payable clauses or
provisions in all policies of insurance maintained by Borrower and its
Subsidiaries pursuant to this Section 9.6 shall be endorsed in favor of and made
payable to Administrative Agent for the ratable benefit of Banks, as their
interests may appear. Administrative Agent shall have the right, for the ratable
benefit of the Banks, to collect, and Borrower hereby assigns to Administrative
Agent for the ratable benefit of Banks (and hereby agrees to cause each
Subsidiary of Borrower to assign), any and all monies that may become payable
under any such policies of insurance by reason of damage, loss or destruction of
any of property which stands as security for the Obligations or any part
thereof, and Administrative Agent may, at its election, either apply for the
ratable benefit of Banks all or any part of the sums so collected toward payment
of the Obligations, whether or not such Obligations are then due and payable, in
such manner as Administrative Agent may elect or release same to Borrower or the
applicable Subsidiary of Borrower.

         SECTION 9.7 Payment of Taxes and Claims. Borrower will, and will cause
each of its Subsidiaries to, pay (a) all Taxes imposed upon it or any of its
assets or with respect to any of its franchises, business, income or profits
before any material penalty or interest accrues thereon, and (b) all material
claims (including, without limitation, claims for labor, services, materials and
supplies) for sums which have become due and payable and which by Law have or
might become a Lien (other than a Permitted Encumbrance) on any of its assets;
provided, however, no payment of Taxes or claims shall be required if (i) the
amount, applicability or validity thereof is currently being contested in good
faith by appropriate action promptly initiated and diligently conducted in
accordance with good business practices and no material part of the property or
assets of Borrower or any of its Subsidiaries is subject to any pending levy or
execution, (ii) Borrower and its Subsidiaries, as and to the extent required in
accordance with GAAP, shall have set aside on their books reserves (segregated
to the extent required by GAAP) deemed by them to be adequate with respect
thereto, and (iii) the Borrower has notified Administrative Agent of such
circumstances in detail satisfactory to Administrative Agent.

                                       52

<PAGE>   59

         SECTION 9.8 Compliance with Laws and Documents. Borrower will, and will
cause each of its Subsidiaries to, comply with all Laws, their respective
partnership agreements, certificates (or articles) of incorporation, bylaws,
regulations and similar organizational documents and all Material Agreements to
which Borrower or any of its Subsidiaries is a party, if a violation, alone or
when combined with all other such violations, could result in a Material Adverse
Change.

         SECTION 9.9 Operation of Properties and Equipment.

                  (a) Borrower will, and will cause each of the other Credit
Parties to, maintain, develop and operate (or cause the operator to maintain and
operate to the extent Borrower or any other Credit Party is not the operator)
its Mineral Interests in a good and workmanlike manner, and observe and comply
with all of the terms and provisions, express or implied, of all oil and gas
leases relating to such Mineral Interests so long as such Mineral Interests are
capable of producing Hydrocarbons and accompanying elements in paying
quantities.

                  (b) Borrower will, and will cause each of the other Credit
Parties to, comply in all respects with all contracts and agreements applicable
to or relating to its Mineral Interest or the production and sale of
Hydrocarbons and accompanying elements therefrom.

                  (c) Borrower will, and will cause each of the other Credit
Parties to, at all times maintain, preserve and keep all operating equipment
used with respect to its Mineral Interests in proper repair, working order and
condition, and make all necessary or appropriate repairs, renewals,
replacements, additions and improvements thereto so that the efficiency of such
operating equipment shall at all times be properly preserved and maintained;
provided that, no item of operating equipment need be so repaired, renewed,
replaced, added to or improved if Borrower shall in good faith determine that
such action is not necessary or desirable for the continued efficient and
profitable operation of the business of Borrower and the other Credit Parties.

         SECTION 9.10 Environmental Law Compliance. Borrower will, and will
cause each of the other Credit Parties to, comply with all Applicable
Environmental Laws, including, without limitation, (a) all licensing,
permitting, notification and similar requirements of Applicable Environmental
Laws, and (b) all provisions of all Applicable Environmental Laws regarding
storage, discharge, release, transportation, treatment and disposal of Hazardous
Substances. Borrower will, and will cause each of the other Credit Parties to,
promptly pay and discharge when due all legal debts, claims, liabilities and
obligations with respect to any clean-up or remediation measures necessary to
comply with Applicable Environmental Laws.

         SECTION 9.11 ERISA Reporting Requirements. Borrower shall furnish, or
cause to be furnished, to Administrative Agent:

                  (a) Promptly and in any event (i) within thirty (30) days
after Borrower or any ERISA Affiliate knows or has reason to know that any ERISA
Event described in clause (a) of the definition of ERISA Event or any event
described in section 4063(a) of ERISA with respect to any

                                       53

<PAGE>   60

Plan of Borrower or any ERISA Affiliate has occurred, and (ii) within fifteen
(15) days after Borrower or any ERISA Affiliate knows or has reason to know that
any other ERISA Event with respect to any Plan of Borrower or any ERISA
Affiliate has occurred or a request for minimum funding waiver under section 412
of the Code with respect to any Plan of Borrower or any ERISA Affiliate has been
made, a written notice describing such event and describing what action is being
taken or is proposed to be taken with respect thereto, together with a copy of
any notice of event that is given to the PBGC;

                  (b) Promptly and in any event within five (5) Domestic
Business Days after receipt thereof by Borrower or any ERISA Affiliate from the
PBGC, copies of each notice received by Borrower or any ERISA Affiliate of the
PBGC's intention to terminate any Plan or to have a trustee appointed to
administer any Plan;

                  (c) Promptly and in any event within thirty (30) days after
the receipt by Borrower of a request therefor by a Bank, copies of any annual
and other report (including Schedule B thereto) with respect to a Plan filed by
Borrower or any ERISA Affiliate with the United States Department of Labor, the
Internal Revenue Service or the PBGC;

                  (d) Promptly, and in any event within ten (10) Domestic
Business Days after receipt thereof, a copy of any correspondence Borrower or
any ERISA Affiliate receives from the Plan Sponsor (as defined by section
4001(a)(10) of ERISA) of any Plan asserting withdrawal liability pursuant to
section 4219 or 4202 of ERISA upon Borrower or any ERISA Affiliate, and a
statement from the chief financial officer of Borrower or such ERISA Affiliate
setting forth details as to the events giving rise to such withdrawal liability
and the action which Borrower or such ERISA Affiliate is taking or proposes to
take with respect thereto;

                  (e) Notification within thirty (30) days of the effective date
thereof of any material increases in the benefits of any existing Plan which is
not a multiemployer plan (as defined in section 4001(a)(3) of ERISA), or the
establishment of any new Plans, or the commencement of contributions to any Plan
to which Borrower or any ERISA Affiliate was not previously contributing;

                  (f) Notification within five (5) Domestic Business Days after
Borrower or any ERISA Affiliate knows or has reason to know that Borrower or any
such ERISA Affiliate has or intends to file a notice of intent to terminate any
Plan under a distress termination within the meaning of section 4041(c) of ERISA
and a copy of such notice; and

                  (g) Promptly after receipt of written notice of commencement
thereof, notice of all (i) claims made by participants or beneficiaries with
respect to any Plan and (ii) actions, suits and proceedings before any court or
governmental department, commission, board, bureau, agency or instrumentality,
domestic or foreign, affecting Borrower or any ERISA Affiliate with respect to
any Plan, except those which, in the aggregate, if adversely determined would
not result in a Material Adverse Change.

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         SECTION 9.12 Additional Documents. Borrower will, and will cause each
other Credit Party (to the extent each is party thereto) to, cure promptly any
defects in the creation and issuance of each Note, and the execution and
delivery of this Agreement and the other Loan Papers and, at Borrower's expense,
Borrower shall promptly and duly execute and deliver to each Bank, and cause
each other Credit Party to promptly and duly execute and deliver to each Bank,
upon reasonable request, all such other and further documents, agreements and
instruments in compliance with or accomplishment of the covenants and agreements
of Borrower and each other Credit Party in this Agreement and the other Loan
Papers as may be reasonably necessary or appropriate in connection therewith.

         SECTION 9.13 Environmental Review. Not later than thirty (30) days
prior to the date of any acquisition by Borrower of Mineral Interests or related
assets, other than an acquisition of additional interests in Mineral Interests
in which Borrower previously held an interest, Borrower shall deliver to
Administrative Agent a report in form, scope and detail acceptable to
Administrative Agent from environmental engineering firms acceptable to
Administrative Agent, which report or reports shall set forth the results of a
Phase I environmental review of such Mineral Interests and related assets.

                                   ARTICLE 10
                               NEGATIVE COVENANTS

         Borrower agrees that, so long as any Bank has any commitment to lend or
participate in Letter of Credit Exposure hereunder or any amount payable under
any Note remains unpaid or any Letter of Credit remains outstanding:

         SECTION 10.1 Incurrence of Debt. Borrower will not, nor will Borrower
permit any of its Subsidiaries to, incur, become or remain liable for any Debt
other than (a) the Obligations, and (b) other Debt in an aggregate amount
outstanding at any time not to exceed $25,000.

         SECTION 10.2 Distributions. Borrower will not, nor will Borrower permit
any of its Subsidiaries to, directly or indirectly, declare or pay, or incur any
liability to declare or pay, any Distribution; provided, that, so long as no
Default or Borrowing Base Deficiency has then occurred which is continuing
Borrower shall be permitted to make Distributions to EXCO, Hill, Humphrey,
Humphrey Oil and Taurus.

         SECTION 10.3 Negative Pledge. Borrower will not, nor will Borrower
permit any of its Subsidiaries to, create, assume or suffer to exist any Lien on
any asset of Borrower or any of its Subsidiaries other than Permitted
Encumbrances. Borrower will not, nor will Borrower permit any of its
Subsidiaries to, enter into or become bound by any agreement (other than this
Agreement) that prohibits or otherwise restricts the right of Borrower or any of
its Subsidiaries to create, assume or suffer to exist any Lien on any of
Borrower's or any of its Subsidiaries' assets in favor of Administrative Agent
for the ratable benefit of Banks.

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         SECTION 10.4 Consolidations and Mergers. Borrower will not, nor will
Borrower permit any Subsidiary to, consolidate or merge with or into any other
Person.

         SECTION 10.5 Asset Dispositions. Borrower will not, nor will Borrower
permit any of its Subsidiaries to, sell, lease, transfer, abandon or otherwise
dispose of assets with an aggregate value of $25,000 or greater in any Fiscal
Year other than sales of Hydrocarbons produced from Borrower's Mineral Interests
in the ordinary course of business. In no event will Borrower sell, transfer or
dispose of any capital stock or other equity interest, in any Subsidiary of
Borrower nor will any Subsidiary of Borrower issue or sell, any capital stock or
other equity interest or any option, warrant or other right to acquire such
capital stock or equity interest or security convertible into such capital stock
or equity interest to any Person other than the direct parent of such issuer on
the Closing Date.

         SECTION 10.6 Amendments to Organizational Documents; Other Material
Agreements. Borrower will not, nor will Borrower permit any of its Subsidiaries
to, enter into or permit any modification or amendment of, or waive any right or
obligation of any Person under, (a) the Operating Agreement, or (b) its
certificate or articles of incorporation, bylaws, partnership agreement, limited
liability company agreement, regulations or other organizational documents.

         SECTION 10.7 Use of Proceeds. The proceeds of Borrowings will not be
used for any purpose other than the purposes expressly permitted by Section
2.1(d) hereof. Without limiting the foregoing, none of such proceeds (including,
without limitation, proceeds of Letters of Credit issued hereunder) will be
used, directly or indirectly, for any other purpose, including, without
limitation, the purpose, whether immediate, incidental or ultimate, of
purchasing or carrying any Margin Stock, and none of such proceeds will be used
in violation of applicable Law (including, without limitation, the Margin
Regulations). Letters of Credit will be issued hereunder only for the purpose of
securing bids, tenders, bonds, contracts and other obligations entered into in
the ordinary course of Borrower's business. Without limiting the foregoing no
Letters of Credit will be issued hereunder for the purpose of providing credit
enhancement with respect to any Debt or equity security of Borrower or any
Subsidiary of Borrower or to secure Borrower's or any of its Subsidiaries'
obligations with respect to Hedge Transactions other than Hedge Transactions
with a Bank.

         SECTION 10.8 Investments. Borrower will not, nor will Borrower permit
any of its Subsidiaries to, directly or indirectly, make or have outstanding any
Investment other than (a) Permitted Investments, and (b) other Investments to
the extent permitted pursuant to clause (e) of the definition of Restricted
Payments. Borrower will not create or acquire any Subsidiary.

         SECTION 10.9 Transactions with Affiliates. Borrower will not, nor will
Borrower permit any of its Subsidiaries to, engage in any transaction with an
Affiliate unless such transaction is as favorable to such party as could be
obtained in an arm's length transaction with an unaffiliated Person in
accordance with prevailing industry customs and practices. Without limiting the
foregoing, Borrower will not, and Borrower will not permit any of its
Subsidiaries to, pay or become obligated to pay any Distribution to either EXCO,
Hill, Humphrey, or Taurus or any Affiliate of EXCO, Hill, Humphrey and Taurus
other than Distributions expressly permitted by Section 10.2 hereof.

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<PAGE>   63

Notwithstanding the foregoing, Borrower shall be permitted to enter into the
Operating Agreement and make the payments to EXCO expressly contemplated
thereof.

         SECTION 10.10 ERISA. Except in such instances where an omission or
failure would not result in a Material Adverse Change, Borrower will not, nor
will Borrower permit any of its Subsidiaries to (a) take any action or fail to
take any action which would result in a violation of ERISA, the Code or other
laws applicable to the Plans maintained or contributed to by it or any ERISA
Affiliate, or (b) modify the term of, or the funding obligations or contribution
requirements under any existing Plan, establish a new Plan, or become obligated
or incur any liability under a Plan that is not maintained or contributed to by
a Borrower or any ERISA Affiliate as of the Closing Date.

         SECTION 10.11 Hedge Transactions. Borrower will not, nor will Borrower
permit any of its Subsidiaries to, enter into Oil and Gas Hedge Transactions
which would cause the volume of Hydrocarbons with respect to which a settlement
payment is calculated under such Oil and Gas Hedge Transactions to exceed
seventy-five percent (75%) of Borrower's anticipated production from Proved
Producing Mineral Interests during the period from the immediately preceding
settlement date (or the commencement of such Hedge Transaction if there is no
prior settlement date) to such settlement date.

         SECTION 10.12 Fiscal Year. Borrower will not change its fiscal year.

         SECTION 10.13 Change in Business. Borrower will not engage in any
business other than the business engaged in by Borrower on the date hereof as
described in Section 8.13 hereof.

         SECTION 10.14 Restricted Payments. Borrower will not make, and Borrower
will not permit any of its Subsidiaries to, make any Restricted Payment.

                                   ARTICLE 11
                               FINANCIAL COVENANTS

         Borrower agrees that so long as any Bank has any commitment to lend or
participate in Letter of Credit Exposure hereunder or any amount payable under
any Note remains unpaid or any Letter of Credit remains outstanding:

         SECTION 11.1 Current Ratio of Borrower. Borrower will not permit its
ratio of Consolidated Current Assets to its Consolidated Current Liabilities to
be less than 1.0 to 1.0 at any time.

         SECTION 11.2 Maximum General and Administrative Expenses. Borrower will
not incur or pay, nor will Borrower permit any of its Subsidiaries to incur or
pay, general and administrative expenses in an aggregate amount exceeding (a)
$75,000 during the period commencing on the

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<PAGE>   64

Closing Date and ending December 31, 2000, or (b) $100,000 during any Fiscal
Year ending on or after December 31, 2001.

                                   ARTICLE 12
                                    DEFAULTS

         SECTION 12.1 Events of Default. If one or more of the following events
(collectively "Events of Default" and individually an "Event of Default") shall
have occurred and be continuing:

                  (a) Borrower shall fail to pay when due any principal on any
Note;

                  (b) Borrower shall fail to pay when due accrued interest on
any Note or any fees or any other amount payable hereunder and such failure
shall continue for a period of three (3) days following the due date;

                  (c) Borrower shall fail to observe or perform any covenant or
agreement contained in Article 10 or Article 11 of this Agreement;

                  (d) Borrower or any other Credit Party shall fail to observe
or perform any covenant or agreement contained in this Agreement or any other
Loan Papers (other than those referenced in Sections 12.1(a), 12.1(b) and
12.1(c)) and such failure continues for a period of twenty (20) days after the
earlier of (i) the date any Authorized Officer of Borrower acquires knowledge of
such failure, or (ii) written notice of such failure has been given to Borrower
by Administrative Agent or any Bank;

                  (e) any representation, warranty, certification or statement
made or deemed to have been made by Borrower or any other Credit Party in any
certificate, financial statement or other document delivered pursuant to this
Agreement shall prove to have been incorrect in any material respect when made;

                  (f) Borrower or any other Credit Party shall fail to make any
payment when due on any Debt of such Person in a principal amount equal to or
greater than $10,000 or any other event or condition shall occur which (i)
results in the acceleration of the maturity of any such Debt, or (ii) entitles
the holder of such Debt to accelerate the maturity thereof;

                  (g) Borrower or any other Credit Party shall commence a
voluntary case or other proceeding seeking liquidation, reorganization or other
relief with respect to itself or its debts under any bankruptcy, insolvency or
other similar law now or hereafter in effect or seeking the appointment of a
trustee, receiver, liquidator, custodian or other similar official of it or any
substantial part of its property, or shall consent to any such relief or to the
appointment of or taking possession by any such official in an involuntary case
or other proceeding commenced against it, or shall make a general

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<PAGE>   65

assignment for the benefit of creditors, or shall fail generally to pay its
debts as they become due, or shall take any corporate action to authorize any of
the foregoing;

                  (h) an involuntary case or other proceeding shall be commenced
against Borrower or any other Credit Party seeking liquidation, reorganization
or other relief with respect to it or its debts under any bankruptcy, insolvency
or other similar law now or hereafter in effect or seeking the appointment of a
trustee, receiver, liquidator, custodian or other similar official of it or any
substantial part of its property, and such involuntary case or other proceeding
shall remain undismissed and unstayed for a period of sixty (60) days; or an
order for relief shall be entered against Borrower or any other Credit Party
under the federal bankruptcy Laws as now or hereafter in effect;

                  (i) one (1) or more final judgments or orders for the payment
of money aggregating in excess of $100,000 shall be rendered against Borrower or
any other Credit Party and such judgment or order shall continue unsatisfied and
unstayed for thirty (30) days;

                  (j) any event occurs with respect to any Plan or Plans
pursuant to which Borrower and/or any ERISA Affiliate incur a liability due and
owing at the time of such event, without existing funding therefor, for benefit
payments under such Plan or Plans in excess of $250,000; or (ii) Borrower, any
ERISA Affiliate, or any other "party-in-interest" or "disqualified person", as
such terms are defined in section 3(14) of ERISA and section 4975(e)(2) of the
Code, shall engage in transactions which in the aggregate would reasonably
result in a direct or indirect liability to Borrower or any ERISA Affiliate in
excess of $250,000 under section 409 or 502 of ERISA or section 4975 of the
Code;

                  (k) Borrower or any Subsidiary of Borrower shall incur
Environmental Liabilities which, individually or when considered in the
aggregate, exceed $250,000;

                  (l) this Agreement or any other Loan Paper shall cease to be
in full force and effect or shall be declared null and void or the validity or
enforceability thereof shall be contested or challenged by Borrower or any other
Credit Party , or Borrower or any other Credit Party shall deny that it has any
further liability or obligation under any of the Loan Papers to which it is a
party, or any Lien created by the Loan Papers shall for any reason (other than
the release thereof in accordance with the Loan Papers) cease to be a valid,
first priority, perfected Lien upon any of the Proved Mineral Interests
purported to be covered thereby;

                  (m) a Material Adverse Change shall occur; or

                  (n) a Change of Control shall occur;

then, and in every such event, Administrative Agent shall without presentment,
notice or demand (unless expressly provided for herein) of any kind (including,
without limitation, notice of intention to accelerate and acceleration), all of
which are hereby waived, (a) if requested by Required Banks, terminate the
Commitments and they shall thereupon terminate, and (b) if requested by Required

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<PAGE>   66

Banks, take such other actions as may be permitted by the Loan Papers including,
declaring the Notes (together with accrued interest thereon) to be, and the
Notes shall thereupon become, immediately due and payable; provided that in the
case of any of the Events of Default specified in Sections 12.1(g) or 12.1(h),
without any notice to Borrower or any other act by Administrative Agent or
Banks, the Commitments shall thereupon terminate and the Notes (together with
accrued interest thereon) shall become immediately due and payable.

                                   ARTICLE 13
                                     AGENTS

         SECTION 13.1 Appointment, Powers, and Immunities. Each Bank hereby
irrevocably appoints and authorizes each Agent to act as its agent under this
Agreement and the other Loan Papers with such powers and discretion as are
specifically delegated to each such Agent by the terms of this Agreement and the
other Loan Papers (and any separate agreements entered into among the parties
regarding same), together with such other powers as are reasonably incidental
thereto. No Agent (which term as used in this sentence and in Section 13.5 and
the first sentence of Section 13.6 hereof shall include their Affiliates and
their own and their Affiliates' officers, directors, employees, and agents): (a)
shall have any duties or responsibilities except those expressly set forth in
this Agreement and the other Loan Papers and no Agent shall be a trustee or
fiduciary for any Bank; (b) shall be responsible to Banks for any recital,
statement, representation, or warranty (whether written or oral) made in or in
connection with any Loan Paper or any certificate or other document referred to
or provided for in, or received by any of them under, any Loan Paper, or for the
value, validity, effectiveness, genuineness, enforceability, or sufficiency of
any Loan Paper, or any other document referred to or provided for therein or for
any failure by any Credit Party or any other Person to perform any of its
obligations thereunder; (c) shall be responsible for or have any duty to
ascertain, inquire into, or verify the performance or observance of any
covenants or agreements by any Credit Party or the satisfaction of any condition
or to inspect the property (including the books and records) of any Credit Party
or any of its Subsidiaries or Affiliates; (d) shall be required to initiate or
conduct any litigation or collection proceedings under any Loan Paper; and (e)
shall be responsible for any action taken or omitted to be taken by it under or
in connection with any Loan Paper, except for its own gross negligence or
willful misconduct. Each Agent may employ agents and attorneys-in-fact and shall
not be responsible for the negligence or misconduct of any such agents or
attorneys-in-fact selected by any such Agent with reasonable care.

         SECTION 13.2 Reliance by Agents. Each Agent shall be entitled to rely
upon any certification, notice, instrument, writing, or other communication
(including, without limitation, any thereof by telephone or telecopy) believed
by it to be genuine and correct and to have been signed, sent or made by or on
behalf of the proper Person or Persons, and upon advice and statements of legal
counsel (including counsel for any Credit Party), independent accountants, and
other experts selected by any such Agent. Each Agent may deem and treat the
payee of any Note as the holder thereof for all purposes hereof unless and until
Administrative Agent receives and accepts an Assignment and Acceptance Agreement
executed in accordance with Section 14.10 hereof. As to any matters not
expressly provided for by this Agreement, no Agent shall be required to exercise
any

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discretion or take any action, but shall be required to act or to refrain from
acting (and shall be fully protected in so acting or refraining from acting)
upon the instructions of Required Banks, and such instructions shall be binding
on Banks; provided, however, that no Agent shall be required to take any action
that exposes such Agent to personal liability or that is contrary to any Loan
Paper or applicable Law unless it shall first be indemnified to its satisfaction
by Banks against any and all liability and expense which may be incurred by it
by reason of taking any such action.

         SECTION 13.3 Defaults. No Agent shall be deemed to have knowledge or
notice of the occurrence of a Default or Event of Default unless Administrative
Agent has received written notice from a Bank, Parent or Borrower specifying
such Default or Event of Default and stating that such notice is a "Notice of
Default". In the event that Administrative Agent receives such a notice of the
occurrence of a Default or Event of Default, Administrative Agent shall give
prompt notice thereof to Banks. Administrative Agent shall (subject to Section
13.2 hereof) take such action with respect to such Default or Event of Default
as shall reasonably be directed by Required Banks; provided that, unless and
until Administrative Agent shall have received such directions, Administrative
Agent may (but shall not be obligated to) take such action, or refrain from
taking such action, with respect to such Default or Event of Default as it shall
deem advisable in the best interest of Banks.

         SECTION 13.4 Rights as Bank. With respect to its Commitment and the
Revolving Loans made by it, Bank of America (and any successor acting as
Administrative Agent) in its capacity as a Bank hereunder shall have the same
rights and powers hereunder as any other Bank and may exercise the same as
though it were not acting as Administrative Agent, and the term "Bank" or
"Banks" shall, unless the context otherwise indicates, include Administrative
Agent in its individual capacity. Bank of America (and any successor acting as
Administrative Agent), each other Agent and their Affiliates may (without having
to account therefor to any Bank) accept deposits from, lend money to, make
investments in, provide services to, and generally engage in any kind of
lending, trust, or other business with any Credit Party or Affiliates as if it
were not acting as Agent, and Bank of America (and any successor acting as
Administrative Agent), each other Agent and their Affiliates may accept fees and
other consideration from any Credit Party or Affiliates for services in
connection with this Agreement or otherwise without having to account for the
same to Banks.

         SECTION 13.5 Indemnification. Banks agree to indemnify each Agent (to
the extent not reimbursed by Parent and/or Borrower hereof, but without limiting
the obligations of Parent and Borrower to so reimburse) ratably in accordance
with their respective Commitments, for any and all liabilities, obligations,
losses, damages, penalties, actions, judgments, suits, costs, expenses
(including attorneys' fees), or disbursements of any kind and nature whatsoever
that may be imposed on, incurred by or asserted against any such Agent
(including by any Bank) in any way relating to or arising out of any Loan Paper
or the transactions contemplated thereby or any action taken or omitted by any
Agent under any Loan Paper (INCLUDING ANY OF THE FOREGOING ARISING FROM THE
NEGLIGENCE OF ANY AGENT); provided that no Bank shall be liable for any of the
foregoing to the extent they arise from the gross negligence or willful
misconduct of the Person to be indemnified. Without limitation of the foregoing,
each Bank agrees to reimburse each Agent

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promptly upon demand for its ratable share of any costs or expenses payable by
Parent and/or Borrower hereunder, to the extent that any such Agent is not
promptly reimbursed for such costs and expenses by Parent and/or Borrower. The
agreements contained in this Section 13.5 shall survive payment and performance
in full of the Obligations and all other amounts payable under this Agreement.

         SECTION 13.6 Non-Reliance on Agents and Other Banks. Each Bank agrees
that it has, independently and without reliance on any Agent or any other Bank,
and based on such documents and information as it has deemed appropriate, made
its own credit analysis of each Credit Party and decision to enter into this
Agreement and that it will, independently and without reliance upon any Agent or
any other Bank, and based on such documents and information as it shall deem
appropriate at the time, continue to make its own analysis and decisions in
taking or not taking action under the Loan Papers. Except for notices, reports,
and other documents and information expressly required to be furnished to Banks
by Administrative Agent hereunder, no Agent shall have any duty or
responsibility to provide any Bank with any credit or other information
concerning the affairs, financial condition, or business of any Credit Party or
their Affiliates that may come into the possession of any such Agent or any of
their Affiliates.

         SECTION 13.7 Resignation of Agents. Any Agent may resign at any time by
giving notice thereof to Banks and Borrower. Upon any such resignation, Required
Banks shall have the right to appoint a successor Agent. If no successor Agent
shall have been so appointed by Required Banks and shall have accepted such
appointment within thirty (30) days after the retiring Agent's giving of notice
of resignation, then the retiring Agent may, on behalf of Banks, appoint a
successor Agent which shall be a commercial bank organized under the Laws of the
United States of America having combined capital and surplus of at least
$100,000,000. Upon the acceptance of any appointment as Agent hereunder by a
successor, such successor shall thereupon succeed to and become vested with all
the rights, powers, discretion, privileges, and duties of the retiring Agent,
and the retiring Agent shall be discharged from its duties and obligations
hereunder. After any retiring Agent's resignation hereunder as Agent, the
provisions of this Article 13 shall continue in effect for its benefit in
respect of any actions taken or omitted to be taken by it while it was acting as
Agent.

                                   ARTICLE 14
                                  MISCELLANEOUS

         SECTION 14.1 Notices. All notices, requests and other communications to
any party hereunder shall be in writing (including bank wire, telecopy or
similar writing) and shall be given, if to Administrative Agent or any Bank, at
its address or telecopier number set forth on Schedule 1 hereto, and if given to
Borrower, at its address or telecopy number set forth on the signature pages
hereof (or in either case, at such other address or telecopy number as such
party may hereafter specify for the purpose by notice to the other parties
hereto). Each such notice, request or other communication shall be effective (a)
if given by telecopy, when such telecopy is transmitted to the telecopy number
specified in this Section 14.1 and the appropriate answerback is received or
receipt

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is otherwise confirmed, (b) if given by mail, three (3) Domestic Business Days
after deposit in the mails with first class postage prepaid, addressed as
aforesaid or (c) if given by any other means, when delivered at the address
specified in this Section 14.1; provided that notices to Administrative Agent
under Article 2 or 3 shall not be effective until received.

         SECTION 14.2 No Waivers. No failure or delay by Administrative Agent or
any Bank in exercising any right, power or privilege hereunder or under any Note
or other Loan Paper shall operate as a waiver thereof nor shall any single or
partial exercise thereof preclude any other or further exercise thereof or the
exercise of any other right, power or privilege. The rights and remedies herein
provided shall be cumulative and not exclusive of any rights or remedies
provided by Law or in any of the other Loan Papers.

         SECTION 14.3 Expenses; Indemnification.

                  (a) Borrower agrees to pay on demand all reasonable costs and
expenses of Administrative Agent in connection with the syndication,
preparation, execution, delivery, modification, and amendment of this Agreement,
the other Loan Papers, and the other documents to be delivered hereunder,
including, without limitation, the reasonable fees and expenses of counsel for
Administrative Agent (including the cost of internal counsel) with respect
thereto and with respect to advising Administrative Agent as to its rights and
responsibilities under the Loan Papers. Borrower further agrees to pay on demand
all reasonable costs and expenses of Administrative Agent and Banks, if any
(including, without limitation, reasonable attorneys' fees and expenses and the
cost of internal counsel), in connection with the enforcement (whether through
negotiations, legal proceedings, or otherwise) of the Loan Papers and the other
documents to be delivered hereunder.

                  (b) Borrower agrees to indemnify and hold harmless
Administrative Agent and each Bank and each of their Affiliates and their
respective officers, directors, employees, Administrative Agents, and advisors
(each, an "Indemnified Party") from and against any and all claims, damages,
losses, liabilities, costs, and expenses (including, without limitation,
reasonable attorneys' fees) that may be incurred by or asserted or awarded
against any Indemnified Party, in each case arising out of or in connection with
or by reason of (including, without limitation, in connection with any
investigation, litigation, or proceeding or preparation of defense in connection
therewith) the Loan Papers, any of the transactions contemplated herein or the
actual or proposed use of the proceeds of the Revolving Loan (INCLUDING ANY OF
THE FOREGOING ARISING FROM THE NEGLIGENCE OF THE INDEMNIFIED PARTY), except to
the extent such claim, damage, loss, liability, cost, or expense is found in a
final, non-appealable judgment by a court of competent jurisdiction to have
resulted from such Indemnified Party's gross negligence or willful misconduct.
In the case of an investigation, litigation or other proceeding to which the
indemnity in this Section 14.3 applies, such indemnity shall be effective
whether or not such investigation, litigation or proceeding is brought by
Borrower, its directors, shareholders or creditors or an Indemnified Party or
any other Person or any Indemnified Party is otherwise a party thereto and
whether or not the transactions contemplated hereby are consummated. Borrower
agrees not to assert any claim against Administrative Agent, any Bank, any of
their Affiliates, or any of their respective directors, officers,

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employees, attorneys, Administrative Agents, and advisers, on any theory of
liability, for special, indirect, consequential, or punitive damages arising out
of or otherwise relating to the Loan Papers, any of the transactions
contemplated herein or the actual or proposed use of the proceeds of the
Revolving Loan.

                  (c) Without prejudice to the survival of any other agreement
of Borrower hereunder, the agreements and obligations of Borrower contained in
this Section 14.3 shall survive the payment in full of the Revolving Loans and
all other amounts payable under this Agreement.

         SECTION 14.4 Right of Set-off; Adjustments.

                  (a) Upon the occurrence and during the continuance of any
Event of Default, each Bank (and each of its Affiliates) is hereby authorized at
any time and from time to time, to the fullest extent permitted by Law, to set
off and apply any and all deposits (general or special, time or demand,
provisional or final) at any time held and other indebtedness at any time owing
by such Bank (or any of its Affiliates) to or for the credit or the account of
Borrower against any and all of the Obligations, irrespective of whether such
Bank shall have made any demand under this Agreement or Note held by such and
although such obligations may be unmatured. Each Bank agrees promptly to notify
Borrower after any such set-off and application made by such Bank; provided,
however, that the failure to give such notice shall not affect the validity of
such set-off and application. The rights of each Bank under this Section 14.4
are in addition to other rights and remedies (including, without limitation,
other rights of set-off) that such Bank may have.

                  (b) If any Bank (a "benefitted Bank") shall at any time
receive any payment of all or part of the Revolving Loans owing to it, or
interest thereon, or receive any collateral in respect thereof (whether
voluntarily or involuntarily, by set-off, or otherwise), in a greater proportion
than any such payment to or collateral received by any other Bank, if any, in
respect of such other Bank's Revolving Loans owing to it, or interest thereon,
such benefitted Bank shall purchase for cash from the other Banks a
participating interest in such portion of each such other Bank's Revolving Loans
owing to it, or shall provide such other Banks with the benefits of any such
collateral, or the proceeds thereof, as shall be necessary to cause such
benefitted Bank to share the excess payment or benefits of such collateral or
proceeds ratably with each Banks; provided, however, that if all or any portion
of such excess payment or benefits is thereafter recovered from such benefitted
Bank, such purchase shall be rescinded, and the purchase price and benefits
returned, to the extent of such recovery, but without interest. Borrower agrees
that any Bank so purchasing a participation from a Bank pursuant to this Section
14.4 may, to the fullest extent permitted by Law, exercise all of its rights of
payment (including the right of set-off) with respect to such participation as
fully as if such Person were the direct creditor of Borrower in the amount of
such participation.

         SECTION 14.5 Amendments and Waivers. Any provision of this Agreement or
any other Loan Paper may be amended or waived if, but only if, such amendment or
waiver is in writing and is signed by Borrower and the Required Banks (and, if
Article 13 or the rights or duties of any Agent are affected thereby, by such
Agent); provided that no such amendment or waiver shall, unless signed

                                       64

<PAGE>   71

by each Bank directly affected thereby, (i) increase the Commitments of Banks,
(ii) reduce the principal of or rate of interest on any Revolving Loan or any
fees or other amounts payable hereunder, (iii) postpone any date fixed for the
payment of any scheduled installment of principal of or interest on any
Revolving Loan or any fees or other amounts payable hereunder or for termination
of any Commitment, (iv) change the percentage of the Commitments or of the
unpaid principal amount of the Notes, or the number of Banks, which shall be
required for Banks or any of them to take any action under this Section 14.5 or
any other provision of this Agreement, or (v) release any guarantor of the
Obligations or all or substantially all of the collateral securing the
Obligations.

         SECTION 14.6 Survival. All representations, warranties and covenants
made by Borrower or any of its Subsidiaries herein or in any certificate or
other instrument delivered by it or in its behalf under the Loan Papers shall be
considered to have been relied upon by Banks and shall survive the delivery to
Banks of such Loan Papers or the extension of the Revolving Loans (or any part
thereof), regardless of any investigation made by or on behalf of Banks. The
indemnity provided in Section 14.3 herein shall survive the repayment of all
credit advances hereunder and/or the discharge or release of any Lien granted
hereunder or in any other Loan Paper, contract or agreement between Borrower or
any of its Subsidiaries and Administrative Agent or any Bank.

         SECTION 14.7 Limitation on Interest. Regardless of any provision
contained in the Loan Papers, Banks shall never be entitled to receive, collect,
or apply, as interest on the Revolving Loan, any amount in excess of the Maximum
Lawful Rate, and in the event any Bank ever receives, collects or applies as
interest any such excess, such amount which would be deemed excessive interest
shall be deemed a partial prepayment of principal and treated hereunder as such;
and if the Revolving Loan is paid in full, any remaining excess shall promptly
be paid to Borrower. In determining whether or not the interest paid or payable
under any specific contingency exceeds the Maximum Lawful Rate, Borrower and
Banks shall, to the extent permitted under applicable Law, (a) characterize any
nonprincipal payment as an expense, fee or premium rather than as interest, (b)
exclude voluntary prepayments and the effects thereof and (c) amortize, prorate,
allocate and spread, in equal parts, the total amount of the interest throughout
the entire contemplated term of the Notes, so that the interest rate is the
Maximum Lawful Rate throughout the entire term of the Notes; provided, however,
that if the unpaid principal balance thereof is paid and performed in full prior
to the end of the full contemplated term thereof, and if the interest received
for the actual period of existence thereof exceeds the Maximum Lawful Rate,
Banks shall refund to Borrower the amount of such excess and, in such event,
Banks shall not be subject to any penalties provided by any laws for contracting
for, charging, taking, reserving or receiving interest in excess of the Maximum
Lawful Rate.

         SECTION 14.8 Invalid Provisions. If any provision of the Loan Papers is
held to be illegal, invalid, or unenforceable under present or future Laws
effective during the term thereof, such provision shall be fully severable, the
Loan Papers shall be construed and enforced as if such illegal, invalid, or
unenforceable provision had never comprised a part thereof, and the remaining
provisions thereof shall remain in full force and effect and shall not be
affected by the illegal, invalid, or unenforceable provision or by its severance
therefrom. Furthermore, in lieu of such illegal, invalid, or unenforceable
provision there shall be added automatically as a part of the Loan Papers a
provision

                                       65

<PAGE>   72

as similar in terms to such illegal, invalid, or unenforceable provision as may
be possible and be legal, valid and enforceable.

         SECTION 14.9 Waiver of Consumer Credit Laws. Pursuant to Article
15.10(b) of Chapter 15, Subtitle 79, Revised Civil Statutes of Texas, 1925, as
amended, Borrower agrees that such Chapter 15 shall not govern or in any manner
apply to the Revolving Loan.

         SECTION 14.10 Assignments and Participations.

                  (a) Each Bank may assign to one or more Eligible Assignees all
or a portion of its rights and obligations under this Agreement (including,
without limitation, all or a portion of its interest in the Revolving Loan, its
Note, and its Commitment); provided, however, that

                  (i) each such assignment shall be to an Eligible Assignee;

                  (ii) except in the case of an assignment to another Bank or an
                  assignment of all of a Bank's rights and obligations under
                  this Agreement, any such partial assignment shall be in an
                  amount at least equal to $5,000,000 or an integral multiple of
                  $100,000 in excess thereof;

                  (iii) each such assignment by a Bank shall be of a constant,
                  and not varying, percentage of all of its rights and
                  obligations under this Agreement and its Note; and

                  (iv) the parties to such assignment shall execute and deliver
                  to Administrative Agent for its acceptance an Assignment and
                  Acceptance Agreement (herein so called) in the form of Exhibit
                  J hereto, together with any Note subject to such assignment
                  and a processing fee of $3,500.

Upon execution, delivery, and acceptance of such Assignment and Acceptance
Agreement, the assignee thereunder shall be a party hereto and, to the extent of
such assignment, have the obligations, rights, and benefits of a Bank hereunder
and the assigning Bank shall, to the extent of such assignment, relinquish its
rights and be released from its obligations under this Agreement. Upon the
consummation of any assignment pursuant to this Section 14.10(a), the assignor,
Administrative Agent and Borrower shall make appropriate arrangements so that,
if required, new Notes are issued to the assignor and the assignee. If the
assignee is not incorporated under the Laws of the United States of America or a
state thereof, it shall deliver to Borrower and Administrative Agent
certification as to exemption from deduction or withholding of Taxes in
accordance with Section 4.6(d).

                  (b) Administrative Agent shall maintain at its address set
forth on Schedule 1 hereto, a copy of each Assignment and Acceptance Agreement
delivered to and accepted by it and a register for the recordation of the names
and addresses of Banks and the Commitment of, and principal amount of the
Revolving Loan owing to, each Bank and the Commitment Percentage of

                                       66

<PAGE>   73

each Bank from time to time (the "Register"). The entries in the Register shall
be conclusive and binding for all purposes, absent manifest error, and Borrower,
Administrative Agent and Banks may treat each Person whose name is recorded in
the Register as a Bank hereunder for all purposes of this Agreement. The
Register shall be available for inspection by Borrower or any Bank at any
reasonable time and from time to time upon reasonable prior notice.

                  (c) Upon its receipt of an Assignment and Acceptance Agreement
executed by the parties thereto, together with any Note subject to such
assignment and payment of the processing fee, Administrative Agent shall, if
such Assignment and Acceptance Agreement has been completed and is in
substantially the form of Exhibit J hereto, (i) accept such Assignment and
Acceptance Agreement, (ii) record the information contained therein in the
Register, and (iii) give prompt notice thereof to the parties thereto.

                  (d) Each Bank may sell participations to one or more Persons
in all or a portion of its rights and obligations under this Agreement
(including all or a portion of its Commitment and its interest in the Revolving
Loan); provided, however, that (i) such Bank's obligations under this Agreement
shall remain unchanged, (ii) such Bank shall remain solely responsible to the
other parties hereto for the performance of such obligations, (iii) the
participant shall be entitled to the benefit of the yield protection provisions
contained in Article 4 and the right of set-off contained in Section 14.4, and
(iv) Borrower shall continue to deal solely and directly with such Bank in
connection with such Bank's rights and obligations under this Agreement, and
such Bank shall retain the sole right to enforce the obligations of Borrower
relating to its interest in the Revolving Loan and its Note and to approve any
amendment, modification, or waiver of any provision of this Agreement (other
than amendments, modifications, or waivers decreasing the amount of principal of
or the rate at which interest is payable on the Revolving Loan or Note,
extending any scheduled principal payment date or date fixed for the payment of
interest on the Revolving Loan or Note, or extending its Commitment).

                  (e) Notwithstanding any other provision set forth in this
Agreement, any Bank may at any time assign and pledge all or any portion of its
interest in the Revolving Loan and its Note to any Federal Reserve Bank as
collateral security pursuant to Regulation A and any Operating Circular issued
by such Federal Reserve Bank. No such assignment shall release the assigning
Bank from its obligations hereunder.

                  (f) Any Bank may furnish any information concerning Borrower
or any of its Subsidiaries in the possession of such Bank from time to time to
assignees and participants (including prospective assignees and participants).

                  (g) Borrower shall not assign or transfer any rights or
obligations under any Loan Paper or permit any Credit Party to assign or
transfer any rights or obligations under any Loan Paper without first obtaining
all Banks' consent, and any purported assignment or transfer without all Bank's
consent is void.

                                       67

<PAGE>   74

         SECTION 14.11 TEXAS LAW. THIS AGREEMENT, EACH NOTE AND THE OTHER LOAN
PAPERS SHALL BE CONSTRUED IN ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE
STATE OF TEXAS AND THE LAWS OF THE UNITED STATES OF AMERICA, EXCEPT TO THE
EXTENT THAT THE LAWS OF ANY STATE IN WHICH ANY PROPERTY INTENDED AS SECURITY FOR
THE OBLIGATIONS IS LOCATED NECESSARILY GOVERN (A) THE PERFECTION AND PRIORITY OF
THE LIENS IN FAVOR OF ADMINISTRATIVE AGENT AND BANKS WITH RESPECT TO SUCH
PROPERTY, AND (B) THE EXERCISE OF ANY REMEDIES (INCLUDING FORECLOSURE) WITH
RESPECT TO SUCH PROPERTY.

         SECTION 14.12 Consent to Jurisdiction; Waiver of Immunities.

                  (a) Borrower hereby irrevocably submits to the jurisdiction of
any Texas State or Federal court sitting in the Northern District of Texas over
any action or proceeding arising out of or relating to this Agreement or any
other Loan Papers, and Borrower hereby irrevocably agrees that all claims in
respect of such action or proceeding may be heard and determined in such Texas
State or Federal court. As an alternative, Borrower irrevocably consents to the
service of any and all process in any such action or proceeding by the mailing
of copies of such process to such Person at its address specified in Section
14.1. Borrower agrees that a final unappealable judgment on any such action or
proceeding shall be conclusive and may be enforced in other jurisdictions by
suit on the judgment or in any other manner provided by law.

                  (b) Nothing in this Section 14.12 shall affect any right of
Banks to serve legal process in any other manner permitted by law or affect the
right of any Bank to bring any action or proceeding against Borrower or its
Subsidiaries or their respective properties in the courts of any other
jurisdictions.

                  (c) To the extent that Borrower has or hereafter may acquire
any immunity from jurisdiction of any court or from any legal process (whether
through service or notice, attachment prior to judgment, attachment in aid of
execution, execution or otherwise) with respect to itself or its property,
Borrower hereby irrevocably waives such immunity in respect of its obligations
under this Agreement and the other Loan Papers.

         SECTION 14.13 Counterparts; Effectiveness. This Agreement may be signed
in any number of counterparts, each of which shall be an original, with the same
effect as if the signatures thereto and hereto were upon the same instrument.
This Agreement shall become effective when Administrative Agent shall have
received counterparts hereof signed by all of the parties hereto or, in the case
of any Bank as to which an executed counterpart shall not have been received,
Administrative Agent shall have received telegraphic or other written
confirmation from such Bank of execution of a counterpart hereof by such Bank.

                                       68

<PAGE>   75

         SECTION 14.14 No Third Party Beneficiaries. It is expressly intended
that there shall be no third party beneficiaries of the covenants, agreements,
representations or warranties herein contained other than third party
beneficiaries permitted pursuant to Section 14.10.

         SECTION 14.15 COMPLETE AGREEMENT. THIS AGREEMENT AND THE OTHER LOAN
PAPERS COLLECTIVELY REPRESENT THE FINAL AGREEMENT BY AND AMONG BANKS,
ADMINISTRATIVE AGENT AND BORROWER AND MAY NOT BE CONTRADICTED BY EVIDENCE OF
PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF BANKS, ADMINISTRATIVE
AGENT AND BORROWER. THERE ARE NO UNWRITTEN ORAL AGREEMENTS AMONG BANKS,
ADMINISTRATIVE AGENT AND BORROWER.

         SECTION 14.16 WAIVER OF JURY TRIAL. BORROWER, ADMINISTRATIVE AGENT AND
BANKS HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVE TRIAL BY JURY IN ANY LEGAL
ACTION OR PROCEEDING RELATING TO THIS AGREEMENT OR ANY OF THE OTHER LOAN PAPERS
AND FOR ANY COUNTERCLAIM THEREIN.

                     (signature page to immediately follow)

                                       69

<PAGE>   76

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed by their respective Authorized Officers on the day and year first
above written.

BORROWER:

HUMPHREY-HILL, L.P.,
a Texas limited partnership

By:      EXCO Resources, Inc.
         a Texas corporation,
         its general partner

         By: /s/ T.W. EUBANK
             ------------------------------------
         Name:  T.W. Eubank
         Title: President

Address for Notice:

5735 Pineland, Suite 235
Dallas, TX 75231
Attn: Douglas H. Miller
Fax No.: (214) 368-2087

<PAGE>   77

BANKS:

Bank of America, N.A.,
a national banking association

By: /s/ DENISE A. SMITH
    -----------------------------------------
Name:  Denise A. Smith
Title: Managing Director

Administrative Agent:

Bank of America, N.A.,
a national banking association

By: /s/ DENISE A. SMITH
    -----------------------------------------
Name:  Denise A. Smith
Title: Managing Director

<PAGE>   78

                                    EXHIBIT A

                                FACILITY GUARANTY

         THIS FACILITY GUARANTY (this "Guaranty") is dated as of the ____ day of
__________, ____, by [___________, A ____________] ("Guarantor"), in favor of
BANK OF AMERICA, N.A. (Bank of America, N.A., acting as a Bank but not as
Administrative Agent, and each of its successors and assigns are collectively
referred to herein as "Noteholders").

                              W I T N E S S E T H:

         WHEREAS, Humphrey-Hill, L.P. ("Borrower"), Bank of America, N.A., as
Administrative Agent ("Administrative Agent") and the financial institutions
parties thereto as Banks, are parties to that certain Credit Agreement (as from
time to time amended, the "Agreement") dated as of March 24, 2000, pursuant to
which Noteholders have made a revolving credit loan to Borrower and agreed to
issue and participate in letters of credit issued on behalf of Borrower (unless
otherwise defined herein, all terms used herein with their initial letter
capitalized shall have the meaning given such terms in the Agreement); and

         WHEREAS, Noteholders have required, as a condition to the extension
and/or the continued extension of credit under the Agreement, that Guarantor
execute and deliver this Guaranty; and

         WHEREAS, Guarantor has determined that valuable benefits will be
derived by it as a result of the Agreement and the extension of credit made
(and/or to be made) by Noteholders thereunder; and

         WHEREAS, Guarantor has further determined that the benefits accruing to
it from the Agreement exceed Guarantor's anticipated liability under this
Guaranty.

         NOW, THEREFORE, for valuable consideration, the receipt and sufficiency
of which are hereby acknowledged and confessed, Guarantor hereby covenants and
agrees as follows:

         1. Guarantor hereby absolutely and unconditionally guarantees the
prompt, complete and full payment when due, no matter how such shall become due,
of the Obligations, and further guarantees that Borrower will properly and
timely perform the Obligations. Notwithstanding any contrary provision in this
Guaranty, however, Guarantor's maximum liability under this Guaranty is limited,
to the extent, if any, required so that its liability is not subject to
avoidance under applicable Debtor Relief Laws (as such term is defined in
Paragraph 8 hereof). [PRECEDING SENTENCE WILL NOT BE INCLUDED IN THE FACILITY
GUARANTY EXECUTED BY EXCO.]

                                       A-1

<PAGE>   79

         2. If Guarantor is or becomes liable for any indebtedness owing by
Borrower to any Noteholder by endorsement or otherwise than under this Guaranty,
such liability shall not be in any manner impaired or affected hereby, and the
rights of Noteholders hereunder shall be cumulative of any and all other rights
that Noteholders may ever have against Guarantor. The exercise by any Noteholder
of any right or remedy hereunder or under any other instrument, at law or in
equity, shall not preclude the concurrent or subsequent exercise of any other
right or remedy.

         3. In the event of default by Borrower in payment of the Obligations,
or any part thereof, when such Obligations become due, either by their terms or
as the result of the exercise of any power to accelerate, Guarantor shall, on
demand, and without further notice of dishonor and without any notice having
been given to Guarantor previous to such demand of the acceptance by Noteholders
of this Guaranty, and without any notice having been given to such Guarantor
previous to such demand of the creating or incurring of such Obligations, pay
the amount due thereon to Noteholders at Administrative Agent's office as set
forth in the Agreement, and it shall not be necessary for any Noteholder, in
order to enforce such payment by Guarantor, first, to institute suit or exhaust
its remedies against Borrower or others liable on such Obligations, to have
Borrower joined with Guarantor in any suit brought under this Guaranty or to
enforce their rights against any security which shall ever have been given to
secure such indebtedness; provided, however, that in the event any Noteholder
elects to enforce and/or exercise any remedies they may possess with respect to
any security for the Obligations prior to demanding payment from Guarantor,
Guarantor shall nevertheless be obligated hereunder for any and all sums still
owing to Noteholders on the Obligations and not repaid or recovered incident to
the exercise of such remedies.

         4. Notice to Guarantor of the acceptance of this Guaranty and of the
making, renewing or assignment of the Obligations and each item thereof, are
hereby expressly waived by Guarantor.

         5. Each payment on the Obligations shall be deemed to have been made by
Borrower unless express written notice is given to Noteholders at the time of
such payment that such payment is made by Guarantor as specified in such notice.

         6. If all or any part of the Obligations at any time are secured,
Guarantor agrees that Administrative Agent and/or Noteholders may at any time
and from time to time, at their discretion and with or without valuable
consideration, allow substitution or withdrawal of collateral or other security
and release collateral or other security or compromise or settle any amount due
or owing under the Agreement or amend or modify in whole or in part the
Agreement or any Loan Paper executed in connection with same without impairing
or diminishing the obligations of Guarantor hereunder. Guarantor further agrees
that if Borrower executes in favor of any Noteholder any collateral agreement,
mortgage or other security instrument, the exercise by any Noteholder of any
right or remedy thereby conferred on such Noteholder shall be wholly
discretionary with such Noteholder, and that the exercise or failure to exercise
any such right or remedy shall in no way impair or diminish the obligation of
Guarantor hereunder. Guarantor further agrees that Noteholders and
Administrative Agent shall not be liable for their failure to use diligence in
the collection of the Obligations or in preserving the liability of any Person
liable for the Obligations, and Guarantor

                                       A-2

<PAGE>   80

hereby waives presentment for payment, notice of nonpayment, protest and notice
thereof (including, notice of acceleration), and diligence in bringing suits
against any Person liable on the Obligations, or any part thereof.

         7. Guarantor agrees that Noteholders, in their discretion, may a) bring
suit against all guarantors (including, without limitation, Guarantor hereunder)
of the Obligations jointly and severally or against any one or more of them, b)
compound or settle with any one or more of such guarantors for such
consideration as Noteholders may deem proper, and c) release one or more of such
guarantors from liability hereunder, and that no such action shall impair the
rights of Noteholders to collect the Obligations (or the unpaid balance thereof)
from other such guarantors of the Obligations, or any of them, not so sued,
settled with or released. Guarantor agrees, however, that nothing contained in
this paragraph, and no action by Noteholders permitted under this paragraph,
shall in any way affect or impair the rights or obligations of such guarantors
among themselves.

         8. Guarantor represents and warrants to each Noteholder that a)
Guarantor is a corporation, limited liability company or partnership duly
organized and validly existing under the laws of the jurisdiction of its
incorporation or formation; and b) Guarantor possesses all requisite authority
and power to authorize, execute, deliver and comply with the terms of this
Guaranty; this Guaranty has been duly authorized and approved by all necessary
action on the part of Guarantor and constitutes a valid and binding obligation
of Guarantor enforceable in accordance with its terms, except as the enforcement
thereof may be limited by applicable Debtor Relief Laws; and no approval or
consent of any court or governmental entity is required for the authorization,
execution, delivery or compliance with this Guaranty which has not been obtained
(and copies thereof delivered to Noteholders). As used in this Guaranty, the
term "Debtor Relief Laws" means the Bankruptcy Code of the United States of
America and all other applicable liquidation, conservatorship, bankruptcy,
moratorium, rearrangement, receivership, insolvency, reorganization, suspension
of payments or similar debtor relief Laws from time to time in effect affecting
the rights of creditors generally.

         9. Guarantor covenants and agrees that until the Obligations are paid
and performed in full, except as otherwise provided in the Agreement or unless
Noteholders give their prior written consent to any deviation therefrom, it will
a) at all times maintain its existence and authority to transact business in any
State or jurisdiction where Guarantor has assets and operations, b) promptly
deliver to Noteholders and to Administrative Agent such information respecting
its business affairs, assets and liabilities as Noteholders may reasonably
request, and c) duly and punctually observe and perform all covenants applicable
to Guarantor under the Agreement and the other Loan Papers. The failure of
Guarantor to comply with the terms of this paragraph shall be an Event of
Default under the Agreement.

         10. This Guaranty is for the benefit of Noteholders, their successors
and assigns, and in the event of an assignment by Noteholders (or their
successors or assigns) of the Obligations, or any part thereof, the rights and
benefits hereunder, to the extent applicable to the Obligations so assigned,

                                       A-3

<PAGE>   81

may be transferred with such Obligations. This Guaranty is binding upon
Guarantor and its successors and assigns.

         11. No modification, consent, amendment or waiver of any provision of
this Guaranty, nor consent to any departure by Guarantor therefrom, shall be
effective unless the same shall be in writing and signed by each Noteholder, and
then shall be effective only in the specific instance and for the purpose for
which given. No notice to or demand on Guarantor in any case shall, of itself,
entitle Guarantor to any other or further notice or demand in similar or other
circumstances. No delay or omission by Noteholders in exercising any power or
right hereunder shall impair any such right or power or be construed as a waiver
thereof or any acquiescence therein, nor shall any single or partial exercise of
any such power preclude other or further exercise thereof, or the exercise of
any other right or power hereunder. All rights and remedies of Noteholders
hereunder are cumulative of each other and of every other right or remedy which
Noteholders may otherwise have at law or in equity or under any other contract
or document, and the exercise of one or more rights or remedies shall not
prejudice or impair the concurrent or subsequent exercise of other rights or
remedies.

         12. No provision herein or in any promissory note, instrument or any
other Loan Paper executed by Borrower or Guarantor evidencing the Obligations
shall require the payment or permit the collection of interest in excess of the
Maximum Lawful Rate. If any excess of interest in such respect is provided for
herein or in any such promissory note, instrument, or any other Loan Paper, the
provisions of this paragraph shall govern, and neither Borrower nor Guarantor
shall be obligated to pay the amount of such interest to the extent that it is
in excess of the amount permitted by law. The intention of the parties being to
conform strictly to any applicable federal or state usury Laws now in force, all
promissory notes, instruments and other Loan Papers executed by Borrower or
Guarantor evidencing the Obligations shall be held subject to reduction to the
amount allowed under said usury Laws as now or hereafter construed by the courts
having jurisdiction.

         13. If Guarantor should breach or fail to perform any provision of this
Guaranty, Guarantor agrees to pay Noteholders all costs and expenses (including
court costs and reasonable attorneys fees) incurred by Noteholders in the
enforcement hereof.

         14. (a) The liability of Guarantor under this Guaranty shall in no
manner be impaired, affected or released by the insolvency, bankruptcy, making
of an assignment for the benefit of creditors, arrangement, compensation,
composition or readjustment of Borrower, or any proceedings affecting the
status, existence or assets of Borrower or other similar proceedings instituted
by or against Borrower and affecting the assets of Borrower.

             (b) Guarantor acknowledges and agrees that any interest on any
portion of the Obligations which accrues after the commencement of any
proceeding referred to in clause (a) above (or, if interest on any portion of
the Obligations ceases to accrue by operation of law by reason of the
commencement of said proceeding, such interest as would have accrued on such
portion of the Obligations if said proceedings had not been commenced) shall be
included in the Obligations because it is the intention of Guarantor,
Administrative Agent and Noteholders that the Obligations which are

                                       A-4

<PAGE>   82

guaranteed by Guarantor pursuant to this Guaranty should be determined without
regard to any rule of law or order which may relieve Borrower of any portion of
such Obligations. Guarantor will permit any trustee in bankruptcy, receiver,
debtor in possession, assignee for the benefit of creditors or similar Person to
pay Noteholders or Administrative Agent, or allow the claim of Noteholders or
Administrative Agent in respect of, any such interest accruing after the date on
which such proceeding is commenced.

                  (c) In the event that all or any portion of the Obligations
are paid by Borrower, the obligations of Guarantor hereunder shall continue and
remain in full force and effect or be reinstated, as the case may be, in the
event that all or any part of such payment(s) are rescinded or recovered
directly or indirectly from Administrative Agent or any Noteholder as a
preference, fraudulent transfer or otherwise, and any such payments which are so
rescinded or recovered shall constitute Obligations for all purposes under this
Guaranty.

         15. Guarantor understands and agrees that any amounts of Guarantor on
account with any Noteholder may be offset to satisfy the obligations of
Guarantor hereunder.

         16. Guarantor hereby subordinates and makes inferior any and all
indebtedness now or at any time hereafter owed by Borrower to Guarantor to the
Obligations evidenced by the Agreement and agrees after the occurrence of a
Default or Event of Default under the Agreement, not to permit Borrower to
repay, or to accept payment from Borrower of, such indebtedness or any part
thereof without the prior written consent of Noteholders. Without limiting the
foregoing, Guarantor hereby acknowledges and agrees that it will not accept from
Borrower or any of its Subsidiaries any, distribution, dividend, reimbursement,
repayment, payment or transfer of cash or assets of any type which is prohibited
under or pursuant to the terms of the Agreement (a "Prohibited Payment") and to
the extent any such Prohibited Payment is received by Guarantor, Guarantor will
hold the same in trust for the benefit of the Noteholders and promptly pay the
same to Administrative Agent for application to the Obligations.

         17. During the period that Noteholders have any commitment to lend or
participate in Letter of Credit Exposure under the Loan Papers, or any amount
payable under any Note remains unpaid or any Letter of Credit remains
outstanding, and throughout any additional preferential period subsequent
thereto, Guarantor hereby waives any and all rights of subrogation to which
Guarantor may otherwise be entitled against Borrower, or any other guarantor of
the Obligations, as a result of any payment made by Guarantor pursuant to this
Guaranty.

         18. As of the date hereof, the fair saleable value of the property of
Guarantor is greater than the total amount of liabilities (including contingent
and unliquidated liabilities) of Guarantor, and Guarantor is able to pay all of
its liabilities as such liabilities mature and Guarantor does not have
unreasonably small capital within the meaning of Section 548, Title 11, United
States Code, as amended. In computing the amount of contingent or liquidated
liabilities, such liabilities have been computed at the amount which, in light
of all the facts and circumstances existing as of the date

                                       A-5

<PAGE>   83

hereof, represents the amount that can reasonably be expected to become an
actual or matured liability.

         19. If any provision of this Guaranty is held to be illegal, invalid,
or unenforceable, such provision shall be fully severable; this Guaranty shall
be construed and enforced as if such illegal, invalid, or unenforceable
provision had never comprised a part hereof; and the remaining provisions hereof
shall remain in full force and effect and shall not be affected by the illegal,
invalid, or unenforceable provision or by its severance herefrom. Furthermore,
in lieu of such illegal, invalid, or unenforceable provision there shall be
added automatically as a part of this Guaranty a provision as similar in terms
to such illegal, invalid, or unenforceable provision as may be possible and be
legal, valid and enforceable.

         20. (a) Except to the extent required for the exercise of the remedies
provided in the other security instruments, Guarantor hereby irrevocably submits
to the nonexclusive jurisdiction of any Texas state or federal court over any
action or proceeding arising out of or relating to this Guaranty or any other
Loan Paper, and Guarantor hereby irrevocably agrees that all claims in respect
of such action or proceeding may be heard and determined in such Texas state or
federal court. Guarantor hereby irrevocably waives, to the fullest extent
permitted by Law, any objection which it may now or hereafter have to the laying
of venue of any Litigation (as hereinafter defined) arising out of or in
connection with this Guaranty or any of the Loan Papers brought in district
courts of Dallas County, Texas, or in the United States District Court for the
Northern District of Texas, Dallas Division. Guarantor hereby irrevocably waives
any claim that any Litigation brought in any such court has been brought in an
inconvenient forum. Guarantor hereby irrevocably consents to the service of
process out of any of the aforementioned courts in any such Litigation by the
mailing of copies thereof by certified mail, return receipt requested, postage
prepaid, to Guarantor's office at __________________________________________.
Guarantor irrevocably agrees that any legal proceeding against Noteholders shall
be brought in the district courts of Dallas County, Texas, or in the United
States District Court for the Northern District of Texas, Dallas Division.
Nothing herein shall affect the right of any Noteholder to commence legal
proceedings or otherwise proceed against Guarantor in any jurisdiction or to
serve process in any manner permitted by applicable Law. As used herein, the
term "Litigation" means any proceeding, claim, lawsuit or investigation (1)
conducted or threatened by or before any court or governmental department,
commission, board, bureau, agency or instrumentality of the United States or of
any state, commonwealth, nation, territory, possession, county, parish, or
municipality, whether now or hereafter constituted or existing, or (2) pending
before any public or private arbitration board or panel.

             (b) Nothing in this Paragraph 20 shall affect any right of any
Noteholder to serve legal process in any other manner permitted by Law or affect
the right of any Noteholder to bring any action or proceeding against Guarantor
in the courts of any other jurisdictions.

                                       A-6

<PAGE>   84

                  (c) To the extent that Guarantor has or hereafter may acquire
any immunity from jurisdiction of any court or from any legal process (whether
through service or notice, attachment prior to judgment, attachment in aid of
execution, execution or otherwise) with respect to itself or its property,
Guarantor hereby irrevocably waives such immunity in respect of its obligations
under this Guaranty and the other Loan Papers.

         21. THIS GUARANTY AND THE OTHER LOAN PAPERS COLLECTIVELY REPRESENT THE
FINAL AGREEMENT BY AND AMONG NOTEHOLDERS, ADMINISTRATIVE AGENT, AND GUARANTOR
AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS, OR SUBSEQUENT
ORAL AGREEMENTS OF NOTEHOLDERS, ADMINISTRATIVE AGENT, AND GUARANTOR. THERE ARE
NO UNWRITTEN ORAL AGREEMENTS AMONG NOTEHOLDERS, ADMINISTRATIVE AGENT, AND
GUARANTOR.

         22. GUARANTOR, FOR ITSELF, ITS SUCCESSORS AND ASSIGNS, HEREBY
IRREVOCABLY WAIVES, TO THE FULLEST EXTENT PERMITTED BY LAW, ITS RIGHT TO A JURY
TRIAL, IN ANY LITIGATION ARISING OUT OF OR IN CONNECTION WITH THIS GUARANTY OR
ANY OF THE OTHER LOAN PAPERS.

         23. THIS GUARANTY AND THE OTHER LOAN PAPERS SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF TEXAS.

         EXECUTED and effective as of the date first above written.

                                     GUARANTOR:

                                     ------------------------------------------

                                     By:
                                         --------------------------------------

                                     Name:
                                           ------------------------------------

                                     Title:
                                           ------------------------------------

                                       A-7

<PAGE>   85

                                    EXHIBIT B

                                      NOTE

$25,000,000                       Dallas, Texas                  March 24, 2000

         FOR VALUE RECEIVED, the undersigned, Humphrey-Hill, L.P., a Texas
limited partnership ("Borrower"), promises to pay to the order of Bank of
America, N.A. ("Bank"), at the offices of Bank of America, N.A., as
Administrative Agent ("Administrative Agent"), at 901 Main Street, 64th Floor,
Dallas, Texas 75202, the principal sum of Twenty-Five Million Dollars
($25,000,000), or so much thereof as may be advanced and outstanding, together
with interest, as hereinafter described.

         This Note has been executed and delivered pursuant to, and is subject
to and governed by, the terms of that certain Credit Agreement dated as of March
24, 2000 (as hereafter renewed, extended, amended, or supplemented, the
"Agreement") among Borrower, Bank, certain other financial institutions listed
on Schedule 1 thereto and Administrative Agent. Unless otherwise defined herein
or unless the context hereof otherwise requires, each term used herein with its
initial letter capitalized has the meaning given to such term in the Agreement.

         Borrower also promises to pay interest on the unpaid principal amount
hereof in like money at the offices of Administrative Agent above referenced
from the date hereof at the rates applicable to amounts outstanding under the
Revolving Loan provided in the Agreement and on the dates specified in the
Agreement.

         The principal balance of this Note shall be paid at the times and in
the amounts required by the Agreement. The entire outstanding principal balance
hereof and all accrued but unpaid interest thereon shall be due and payable in
full on the Termination Date.

         Upon and subject to the terms and conditions of the Agreement, Borrower
shall be entitled to prepay the principal of or interest on this Note from time
to time and at any time, in whole or in part.

         Upon the occurrence and continuance of an Event of Default, and upon
the conditions stated in the Agreement, Administrative Agent may, at its option,
and shall, to the extent required in accordance with the terms of the Agreement,
declare the entire unpaid principal of and accrued interest on this Note
immediately due and payable (provided that, upon the occurrence of certain
Events of Default, and upon the conditions stated in the Agreement, such
acceleration shall be automatic), without notice (except as otherwise required
by the Agreement), demand, or presentment, all of which are hereby waived, and
the holder hereof shall have the right to offset against this Note any sum or
sums owed by the holder hereof to Borrower. All past-due principal of and, to
the extent permitted by law, accrued interest on this Note shall, at the option
of the holder hereof, bear interest

                                       B-1

<PAGE>   86

at the lesser of (a) the Maximum Lawful Rate, or (b) the Base Rate plus 2% until
paid from the due date.

         Notwithstanding the foregoing, if at any time, any rate of interest
calculated under Section 2.3 of the Agreement (the "Contract Rate") exceeds the
Maximum Lawful Rate, the rate of interest hereunder shall be limited to the
Maximum Lawful Rate, but any subsequent reductions in the Contract Rate shall
not reduce the rate of interest on this Note below the Maximum Lawful Rate until
the total amount of interest accrued equals the amount of interest which would
have accrued (including the amount of interest which would have accrued prior to
the payment or prepayment of any portion of this Note) if the Contract Rate had
at all times been in effect. In the event that at maturity (stated or by
acceleration), or at final payment of this Note, the total amount of interest
paid or accrued on this Note is less than the amount of interest which would
have accrued if the Contract Rate had at all times been in effect with respect
thereto, then at such time Borrower shall pay to the holder of this Note an
amount equal to the difference between (a) the lesser of the amount of interest
which would have accrued if the Contract Rate had at all times been in effect
and the amount of interest which would have accrued if the Maximum Lawful Rate
had at all times been in effect, and (b) the amount of interest actually paid or
accrued on this Note.

                                     HUMPHREY-HILL, L.P.,
                                     a Texas limited partnership

                                     By:      EXCO Resources, Inc.
                                              a Texas corporation,
                                              its general partner

                                     By:
                                         --------------------------------------

                                     Name:
                                           ------------------------------------

                                     Title:
                                           ------------------------------------

                                       B-2

<PAGE>   87

                             LOANS, MATURITIES, AND
                       PAYMENTS OF PRINCIPAL AND INTEREST

<TABLE>
<CAPTION>
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                         Bank's                             Rate of
                       Commitment        Expiration         Interest        Amount of         Amount         Unpaid
    Borrowing          Percentage       of Interest       Applicable to     Principal      of Interest      Principal      Notation
       Date           of Borrowing         Period           Borrowing         Paid             Paid           Balance      Made By
------------------------------------------------------------------------------------------------------------------------------------
<S>                   <C>               <C>               <C>               <C>            <C>              <C>            <C>

------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------

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------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------

------------------------------------------------------------------------------------------------------------------------------------

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====================================================================================================================================
</TABLE>

                                       B-3

<PAGE>   88

                                    EXHIBIT C

                               OPERATING AGREEMENT

                                [to be attached]

                                       C-1

<PAGE>   89

                                    EXHIBIT D

                               SECURITY AGREEMENT

         THIS SECURITY AGREEMENT (this "Agreement") is executed and effective as
of March 24, 2000, by Humphrey-Hill, L.P., a Texas limited partnership
("Debtor"), in favor of Bank of America, N.A., as Administrative Agent for the
Banks are parties to the Credit Agreement (as herein defined) ("Secured Party").

                              W I T N E S S E T H :

         WHEREAS, Secured Party, Debtor and the financial institutions listed
under the designation "Banks" on the signature pages thereto (the "Banks") are
parties to that certain Credit Agreement dated as of March 24, 2000 pursuant to
which the Banks have agreed to provide Debtor with a multiple advance term
credit facility, all on the terms more particularly set forth therein (such
Credit Agreement, as the same may be modified, amended, renewed, extended or
restated from time to time is hereinafter referred to as the "Credit Agreement";
unless otherwise defined herein, terms used herein with their initial letter
capitalized shall have the meaning given such terms in the Credit Agreement);
and

         WHEREAS, the Banks have required, as a condition precedent to making
the Initial Borrowing under the Credit Agreement, that Debtor execute and
deliver this Agreement to Secured Party for the ratable benefit of the Banks.

         NOW, THEREFORE, in consideration of these premises and for other good
and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged and confessed, and intending to be legally bound hereby, Debtor
hereby agrees with Secured Party, for the ratable benefit of Banks as follows:

         1. Defined Terms. As used herein, the following terms shall have the
following meanings:

                  "Account Debtor" means, with respect to any Account (as herein
         defined) of Debtor, the party that is liable to Debtor with respect to
         such Account.

                  "Accounts" has the meaning assigned in the UCC.

                  "Chattel Paper" has the meaning assigned in the UCC.

                  "Collateral" has the meaning assigned to it in Section 2 of
         this Agreement.

                                       D-1

<PAGE>   90

                  "Contracts" means any and all contracts between Debtor and any
         other party as the same may from time to time be amended, supplemented
         or otherwise modified, including, without limitation, (a) all rights of
         Debtor to receive monies due and to become due to it thereunder or in
         connection therewith, (b) all rights of Debtor to damages arising out
         of, or for, breach or default in respect thereof, and (c) all rights of
         Debtor to perform and to exercise all remedies thereunder. Without
         limiting the foregoing, "Contracts" shall include that certain
         Operating Agreement, and all rights of Debtor thereunder.

                  "Copyright License" means any written agreement now or
         hereafter in existence granting to Debtor any right to use any
         Copyright.

                  "Copyrights" means (a) all copyrights, rights and interests in
         copyrights, works protectable by copyright, copyright registrations and
         copyright applications now owned or hereafter created or acquired by
         Debtor, (b) all renewals of any of the foregoing, (c) all income,
         royalties, damages and payments now or hereafter due and/or payable
         under any of the foregoing, including, without limitation, damages or
         payments for past or future infringements of any of the foregoing, (d)
         the right to sue for past, present and future infringements of any of
         the foregoing, (e) all rights corresponding to any of the foregoing
         throughout the world, and (f) all goodwill associated with and
         symbolized by any of the foregoing.

                  "Deposit Account" has the meaning assigned in the UCC.

                  "Document" has the meaning assigned in the UCC.

                  "Equipment" has the meaning assigned in the UCC.

                  "General Intangibles" has the meaning assigned in the UCC.

                  "Instrument" has the meaning assigned in the UCC.

                  "Intellectual Property" means collectively all of the
         following: Copyrights, Copyright Licenses, Patents, Patent Licenses,
         Trademarks and Trademark Licenses.

                  "Inventory" has the meaning assigned in the UCC.

                  "Mortgage" means that certain Mortgage, Deed of Trust,
         Security Agreement, Financing Statement and Assignment of Production of
         even date herewith, granted by Debtor to Secured Party and filed (or to
         be filed) of record in the real property records of Pecos County,
         Texas.

                  "Patent License" means any written agreement now or hereafter
         in existence granting to Debtor any right to use any invention on which
         a Patent is in existence.

                                       D-2

<PAGE>   91

                  "Patents" means (a) all patents and patent applications now
         owned or hereafter created or acquired by Debtor and the inventions and
         improvements described and claimed therein, and patentable inventions,
         (b) the examinations, reissues, divisions, continuations, renewals,
         extensions and continuations-in-part of any of the foregoing, (c) all
         income, royalties, damages or payments now and hereafter due and/or
         payable under any of the foregoing with respect to any of the
         foregoing, including, without limitation, damages or payments for past
         or future infringements of any of the foregoing, (d) the right to sue
         for past, present and future infringements of any of the foregoing, (e)
         all rights corresponding to any of the foregoing throughout the world,
         (f) all inventions, designs, proprietary or technical information,
         know-how, other data or information, software, databases, all
         embodiments or fixations thereof and related documentation, and all
         other trade secret rights not described above, and (g) all goodwill
         associated with any of the foregoing.

                  "Permitted Encumbrances" has the meaning given such term in
         the Credit Agreement.

                  "Proceeds" means all "Proceeds" as such term is defined in the
         UCC.

                  "Trademark License" means any written agreement now or
         hereafter in existence granting to Debtor any right to use any
         Trademark.

                  "Trademarks" means (a) all trademarks, trade names, corporate
         names, company names, business names, fictitious business names, all
         elements of package or trade dress goods and all general intangibles of
         like nature together with the goodwill of Debtor's business connected
         with the use thereof and symbolized thereby, service marks, logos,
         other business identifiers, prints and labels on which any of the
         foregoing have appeared or appear, all registrations and recordings
         thereof, and all applications in connection therewith including
         registrations, recordings and applications in the United States Patent
         and Trademark Office or in any similar office or agency of the United
         States, any State thereof or any other country or any political
         subdivision thereof, (b) all reissues, extensions or renewals thereof,
         (c) all income, royalties, damages and payments now or hereafter due
         and/or payable under any of the foregoing or with respect to any of the
         foregoing including damages or payments for past or future
         infringements of any of the foregoing, (d) the right to sue for past,
         present and future infringements of any of the foregoing, (e) all
         rights corresponding to any of the foregoing throughout the world, and
         (f) all goodwill associated with and symbolized by any of the
         foregoing.

                  "UCC" means the Uniform Commercial Code as from time to time
         in effect in each of the jurisdictions where the Collateral or a
         portion thereof is situated.

                  "Vehicles" means all cars, trucks, trailers, construction and
         earth moving equipment and other vehicles covered by a certificate of
         title under the law of any state and all tires and other appurtenances
         to any of the foregoing.

                                       D-3

<PAGE>   92

         2. Grant of Security Interest. As collateral security for the prompt
and complete payment and performance when due (whether at the stated maturity,
by acceleration or otherwise) of the Obligations, Debtor hereby assigns,
mortgages, pledges and hypothecates to Secured Party, and hereby grants to
Secured Party for the ratable benefit of the Banks, a continuing first and prior
lien and security interest in all of the following property wherever located and
now owned or at any time hereafter acquired by Debtor or in which Debtor now has
or at any time in the future may acquire any right, title or interest
(collectively, the "Collateral"), subject to no prior Liens other than Permitted
Encumbrances:

                  (1)  all Accounts;

                  (2)  all Chattel Paper;

                  (3)  all Contracts;

                  (4)  all Copyrights;

                  (5)  all Copyright Licenses;

                  (6)  all Deposit Accounts;

                  (7)  all Documents;

                  (8)  all Equipment;

                  (9)  all General Intangibles;

                  (10) all Instruments;

                  (11) all Inventory;

                  (12) all Patents;

                  (13) all Patent Licenses;

                  (14) all Trademarks;

                  (15) all Trademark Licenses;

                  (16) all Vehicles;

                  (17) all books and records of Debtor (including, without
         limitation, customer lists, credit files, computer programs, printouts,
         and other computer materials and records);

                                       D-4

<PAGE>   93

                  (18) all other deposit accounts, monies and other property and
         assets of Debtor of any kind, whether in Debtor's possession or under
         the control of Secured Party or a bailee; and

                  (19) to the extent not otherwise included, all accessions to,
         substitutions for and all replacements, betterments, Proceeds and
         products of any and all of the foregoing, including, without
         limitation, proceeds of and unearned premiums with respect to insurance
         policies insuring any of the foregoing.

         3. Rights of Secured Party; Limitations on Secured Party's and Bank's
Obligations. (a) Debtor Remains Liable under Accounts, Chattel Paper and
Contracts. Anything herein to the contrary notwithstanding, Debtor shall remain
liable under each Account, each item of Chattel Paper, and each Contract to
observe and perform all the conditions and obligations to be observed and
performed by it thereunder, all in accordance with the terms of any agreement
constituting a part of or giving rise to each such Account or item of Chattel
Paper and in accordance with and pursuant to the terms and provisions of each
such Contract. Neither Secured Party nor any Bank shall have any obligation or
liability under any Account or item of Chattel Paper (or any agreement or item
of Chattel Paper giving rise thereto) or Contract by reason of or arising out of
this Agreement or the receipt by Secured Party or any Bank of any payment
relating to such Account, item of Chattel Paper or Contract pursuant hereto, nor
shall Secured Party be obligated in any manner to perform any of the obligations
of Debtor under or pursuant to any Account or item of Chattel Paper (or any
agreement giving rise thereto) or under or pursuant to any Contract, to make any
payment, to make any inquiry as to the nature or the sufficiency of any payment
received by it or as to the sufficiency of any performance by any party under
any Account (or any agreement giving rise thereto) or under any Contract, to
present or file any claim, to take any action to enforce any performance or to
collect the payment of any amounts which may have been assigned to it or to
which it may be entitled at any time or times.

         (b) Notice to Account Debtor, Obligors under Chattel Paper and
Contracting Parties. At any time during the existence of an Event of Default,
Secured Party may (and upon request of Secured Party, Debtor shall) notify
Account Debtors on the Accounts, obligors with respect to Chattel Paper and
parties to the Contracts that the Accounts, the Chattel Paper and the Contracts
have been assigned to Secured Party and that payments in respect thereof shall
be made directly to Secured Party. At any time during the continuance of an
Event of Default, or at any time before an Event of Default and with the prior
consent of Debtor, which consent shall not be unreasonably withheld, Secured
Party may in its own name or in the name of others, communicate with Account
Debtors on the Accounts, obligors with respect to the Chattel Paper and parties
to the Contracts to verify with them to its satisfaction the existence, amount
and terms of any Accounts, Chattel Paper or Contracts.

         (c) Collections on Accounts and Contracts. Secured Party hereby
authorizes Debtor to collect the Accounts, Chattel Paper and Contracts, subject
to Secured Party's direction and control, and Secured Party may curtail or
terminate said authority at any time that an Event of Default has

                                       D-5

<PAGE>   94

occurred which is continuing. All Proceeds while held by Secured Party (or by
Debtor in trust for Secured Party) shall continue to be collateral security for
all of the Obligations and shall not constitute payment thereof until applied as
hereinafter provided. At Secured Party's request after an Event of Default,
Debtor shall deliver to Secured Party all original and other documents
evidencing, and relating to, the agreements and transactions which gave rise to
the Accounts and Contracts, including, without limitation, all original orders,
invoices and shipping receipts. At Secured Party's request prior to an Event of
Default, Debtor shall deliver to Secured Party certified copies of any and all
such documents.

         4. Representations and Warranties. Debtor hereby represents and
warrants that:

         (a) Title; No Other Liens. Except for the Permitted Encumbrances,
Debtor is the legal and beneficial owner of each item of the Collateral free and
clear of any and all Liens or claims of others, and no other person or entity
has any right, title or interest therein. No security agreement, financing
statement or other public notice with respect to all or any part of the
Collateral is on file or of record in any public office, except such as may have
been filed in favor of Secured Party or in connection with a Permitted
Encumbrance. No item of Chattel Paper contains any legend or other notation
indicating that it is subject to a Lien in favor of any Person other than
Secured Party or constitutes property or assets of any Person other than Debtor.

         (b) Perfected First Priority Liens. Except for and subject only to the
Permitted Encumbrances, the Liens and security interests evidenced hereby
constitute first priority perfected Liens on the Collateral in favor of Secured
Party, which are prior to all other Liens on the Collateral created by Debtor
and in existence on the date hereof and which are enforceable as such against
all creditors of and purchasers from Debtor and against any owner or purchaser
of the real property where any of the Collateral is located and any present or
future creditor obtaining a Lien on such real property.

         (c) No Defenses. No dispute, right of setoff, counterclaim or defense
exists with respect to all or any part of the Collateral.

         (d) Consents. No consent of any party (other than Debtor) to any
Contract any obligor with respect to any Chattel Paper or any Account Debtor in
respect of any Account is required in connection with the execution, delivery
and performance of this Agreement. Each Account, each item of Chattel Paper and
each Contract is in full force and effect and constitutes a valid and legally
enforceable obligation of the obligor in respect thereof or the parties thereto,
except as (i) the enforceability thereof may be limited by bankruptcy,
insolvency or similar laws affecting creditors' rights generally, and (ii) the
availability of equitable remedies may be limited by equitable principals of
general applicability. No consent or authorization of, filing with or other act
by or in respect of any Governmental Authority is required in connection with
the execution, delivery, performance, validity or enforceability of any of the
Accounts, Chattel Paper or Contracts by any party thereto other than those which
have been duly obtained, made or performed, and the same are in full force and
effect and do not subject the scope of any such Account, item of Chattel Paper
or Contract to

                                       D-6

<PAGE>   95

any material adverse limitation, either specific or general in nature. Neither
Debtor, nor (to the best of Debtor's knowledge) any other party to any Account,
item of Chattel Paper or Contract is in default or is likely to become in
default in the performance or observance of any of the terms thereof. The right,
title and interest of Debtor in, to and under each Account, each item of Chattel
Paper and each Contract are not subject to any defense, offset, counterclaim or
other claim, nor have any of the foregoing been asserted or alleged against
Debtor as to any of the foregoing. Debtor has delivered to Secured Party a
complete and correct copy of each Contract, including all amendments,
supplements and other modifications thereto. No amount payable to Debtor under
or in connection with any Account, item of Chattel Paper or Contract referred to
above is evidenced by any Instrument which has not been delivered to Secured
Party.

         (e) [Intentionally Deleted].

         (f) Chief Executive Office; Employer ID Number. Debtor's principal
place of business (or, if Debtor has more than one principal place of business,
Debtor's chief executive office) is located at the address set forth on Schedule
I hereto. Debtor's Employer Identification Number is set forth on Schedule I
hereto.

         (g) Farm Products. None of the Collateral constitutes, or is the
Proceeds of, farm products.

         (h) Intellectual Property. Debtor does not own or hold any right or
interest in Intellectual Property with a value (considered in the aggregate) in
excess of $25,000.

         (i) Chattel Paper. Debtor does not own or hold any Chattel Paper.

         (j) Instruments. Debtor does not own or hold any Instruments.

         (k) Vehicles. Debtor does not own or hold any Vehicles.

         (l) Deposit Accounts. Schedule II hereto is a true and correct list of
all Deposit Accounts maintained by Debtor on the date hereof.

         (m) Power and Authority; Authorization. Debtor has the power and
authority and the legal right to execute and deliver, to perform its obligations
under, and to grant the Liens and security interests on the Collateral pursuant
to, this Agreement and has taken all necessary action to authorize its
execution, delivery and performance of, and grant of the Liens and security
interests on the Collateral pursuant to, this Agreement.

         (n) Enforceability. This Agreement constitutes a legal, valid and
binding obligation of Debtor enforceable in accordance with its terms, except as
(i) the enforceability hereof may be limited by bankruptcy, insolvency or
similar laws affecting the enforcement of creditors' rights generally, and (ii)
the availability of equitable remedies may be limited by equitable principles of
general applicability.

                                       D-7

<PAGE>   96

         (o) No Conflict. The execution, delivery and performance of this
Agreement will not violate any provision of any Law or contractual obligation of
Debtor and will not result in the creation or imposition of any Lien on any of
the properties or revenues of Debtor pursuant to any Law or contractual
obligation of Debtor, except as contemplated hereby.

         (p) No Consents, etc. No consent or authorization of, filing with, or
other act by or in respect of, any Governmental Authority and no consent of any
other party (including, without limitation, any creditor of Debtor), is required
in connection with the execution, delivery, performance, validity or
enforceability of this Agreement.

         5. Covenants. Debtor covenants and agrees with Secured Party for the
ratable benefit of the Banks that, from and after the date of this Agreement
until the Obligations are paid in full:

         (a) Further Documentation; Pledge of Instruments. At any time and from
time to time, upon the written request of Secured Party, and at the sole expense
of Debtor, Debtor will promptly and duly execute and deliver such further
assignments, certificates, supplemental writings, instruments and documents and
take such further action as Secured Party may reasonably request for the purpose
of obtaining or preserving the full benefits of this Agreement and of the rights
and powers herein granted, including, without limitation, the filing of any
financing or continuation statements under the UCC in effect in any jurisdiction
with respect to the Liens and security interests evidenced hereby. Debtor also
hereby authorizes Secured Party to file any such financing or continuation
statement without the signature of Debtor to the extent permitted by applicable
law. A carbon, photographic or other reproduction of this Agreement shall be
sufficient as a financing statement for filing in any jurisdiction. If any
amount payable under or in connection with any of the Collateral shall be or
become evidenced by any promissory note or other Instrument, such Instrument
shall be immediately delivered to Secured Party, shall be duly endorsed in a
manner satisfactory to Secured Party, and shall constitute Collateral pursuant
to this Agreement.

         (b) Indemnification. Debtor agrees to pay, and to indemnify, defend and
hold Secured Party and each Bank harmless from, any and all liabilities, costs
and expenses (including, without limitation, reasonable legal fees and expenses)
(i) with respect to, or resulting from, any delay in paying any and all excise,
sales or other taxes which may be payable or determined to be payable with
respect to any of the Collateral, (ii) with respect to, or resulting from, any
delay in complying with any Laws applicable to any of the Collateral or (iii) in
connection with any of the transactions contemplated by this Agreement. In any
suit, proceeding or action brought by Secured Party under any Account or
Contract for any sum owing thereunder, or to enforce any provisions of any
Account or Contract, Debtor will save, indemnify, defend and hold Secured Party
and each Bank harmless from and against all expense, loss or damage suffered by
reason of any defense, setoff, counterclaim, recoupment or reduction or
liability whatsoever of the Account Debtor or obligor thereunder, arising out of
a breach by Debtor of any obligation thereunder or arising out of any other
agreement, indebtedness or liability at any time owing to or in favor of such
Account Debtor or obligor or its successors from Debtor.

                                       D-8

<PAGE>   97

         (c) Maintenance of Records. Debtor will keep and maintain at its own
cost and expense satisfactory and complete records of the Collateral, including,
without limitation, a record of all payments received and all credits granted
with respect to the Accounts, Chattel Paper and Contracts. Debtor will mark its
books and records pertaining to the Collateral to evidence this Agreement and
the Liens and security interests evidenced hereby. For the further security of
Secured Party and the Banks, Secured Party shall have a security interest,
subject to no Liens other than Permitted Encumbrances, in all of Debtor's books
and records pertaining to the Collateral, and, after and during the continuance
of an Event of Default, Debtor shall turn over any such books and records to
Secured Party or to its representatives at the request of Secured Party.

         (d) Right of Inspection. Secured Party, each Bank and their respective
representatives shall at all times have full and free access upon reasonable
notice and during normal business hours to all the books, correspondence and
records of Debtor, and Secured Party, each Bank and their respective
representatives may examine the same, take extracts therefrom and make
photocopies thereof. Secured Party, each Bank and their respective
representatives shall at all times also have the right upon reasonable notice
and during normal business hours to enter into and upon any premises where any
of the Inventory or Equipment is located for the purpose of inspecting the same,
observing its use or otherwise protecting its interests therein. Debtor shall
pay the costs incurred by Secured Party and each Bank in connection with any
such exercise of its rights pursuant to this Section 5(d) to the extent required
by the Credit Agreement.

         (e) Compliance with Laws, etc. Debtor will comply with all Laws
applicable to the Collateral or any part thereof or to the operation of Debtor's
business.

         (f) Compliance with Terms of Chattel Paper and Contracts, etc. Debtor
will perform and comply in all material respects with all of its obligations
under the Chattel Paper and Contracts and all its other contractual obligations
relating to the Collateral.

         (g) Payment of Obligations. To the extent required pursuant to Section
8.7 of the Credit Agreement, Debtor will pay promptly when due all Taxes,
assessments and governmental charges or levies imposed upon the Collateral or in
respect of its income or profits therefrom, as well as all claims of any kind
(including, without limitation, claims for labor, materials and supplies)
against or with respect to the Collateral.

         (h) Limitation on Liens on Collateral. Debtor will not create, assume
or permit to exist, will defend the Collateral against, and will take such other
action as is necessary to remove, any Lien or claim on or to the Collateral,
other than the Permitted Encumbrances, and will defend the right, title and
interest of Secured Party and the Banks in and to any of the Collateral against
the claims and demands of all parties whomsoever other than holders of Permitted
Encumbrances with respect to such Permitted Encumbrances.

         (i) Limitations on Dispositions of Collateral. Debtor will not sell,
transfer, lease, abandon or otherwise dispose of any of the Collateral, or
attempt, offer or contract to do so, except as may

                                       D-9

<PAGE>   98

be permitted by the Credit Agreement. Upon the sale, transfer, lease,
abandonment or disposition of any of the Collateral as permitted under the
Credit Agreement, the Lien granted by this Agreement shall continue with respect
to any Proceeds received by Debtor upon such sale, transfer, lease, abandonment
or disposition.

         (j) Limitations on Modifications, Waivers, Extensions of Agreements
Giving Rise to Accounts and Material Agreements. Debtor will not (i) amend,
modify, terminate or waive any provision of any Contract, any item of Chattel
Paper or any agreement giving rise to or forming a part of an Account or a
Deposit Account or any item of Chattel Paper in any manner, (ii) fail to
exercise promptly and diligently each and every material right which it may have
under each Contract, each item of Chattel Paper and each agreement giving rise
to an Account or a Deposit Account, or (iii) fail to deliver to Secured Party a
copy of each material demand, notice or document received by it relating in any
way to any Contract required to be delivered to Secured Party pursuant to the
terms of the Credit Agreement, Chattel Paper or any agreement giving rise to an
Account or a Deposit Account.

         (k) Limitations on Discounts, Compromises, Extensions of Accounts.
Without the prior consent of Secured Party, Debtor will not grant any extension
of the time of payment of any item of Chattel Paper or any Account, compromise,
compound or settle the same for less than the full amount thereof, release,
wholly or partially, any party liable for the payment thereof, or allow any
credit or discount whatsoever thereon, provided that Debtor may, during any
fiscal year, grant credits or discounts of up to $25,000 in the aggregate on
Accounts.

         (l) Maintenance of Equipment. Debtor will maintain each item of
Equipment as provided in the Credit Agreement and Mortgage.

         (m) Maintenance of Insurance. Debtor will at all times maintain the
insurance required by the Mortgage.

         (n) Further Identification of Collateral. Debtor will furnish to
Secured Party and each Bank from time to time upon request statements and
schedules further identifying and describing the Collateral and such other
reports in connection with the Collateral as Secured Party may reasonably
request, all in reasonable detail and in form satisfactory to Secured Party.

         (o) Notices. Debtor will advise Secured Party and each Bank promptly,
in reasonable detail, at their respective addresses set forth for notice in the
Credit Agreement, (i) of any Lien (other than Permitted Encumbrances) on, or
claim asserted against, any of the Collateral and (ii) of the occurrence of any
other event which could reasonably be expected to have a Material Adverse Effect
on the aggregate value of the Collateral hereunder.

         (p) Changes in Locations, Name, etc. Debtor will not change the
location of its chief executive office from that specified in Schedule I, and
Debtor will not change its name, identity or corporate structure to such an
extent that any financing statement filed by Secured Party in

                                      D-10

<PAGE>   99

connection with this Agreement would become seriously misleading, unless it
shall give prior written notice as soon as practicable thereof and prior to
effecting any such change take such steps as Secured Party may deem necessary or
advisable to continue the perfection and priority of the security interest
granted pursuant hereto; provided, that nothing contained herein shall be deemed
to permit anything prohibited by the Credit Agreement.

         (q) Vehicles. Debtor will maintain each vehicle in good operating
condition, ordinary wear and tear and immaterial impairments of value and damage
by the elements excepted, and will provide all maintenance, service and repairs
necessary for such purpose. No Vehicle shall be removed from the state which has
issued the certificate of title therefor for a period in excess of thirty (30)
consecutive days. With respect to any Vehicle acquired by Debtor subsequent to
the date hereof, within five (5) days after the date of acquisition thereof, if
requested by Secured Party an application for certificate of title indicating
Secured Party's Lien on the Vehicle covered by such certificate, and any other
necessary documentation, shall be filed in each office in each jurisdiction
which Secured Party shall deem advisable to perfect its Lien on the Vehicle.

         (s) Deposit Accounts. Debtor will not amend, modify, terminate or waive
any provision of any agreement giving rise to or forming a part of any Deposit
Account, and Debtor will not open any new Deposit Account or enter into any
agreement giving rise to or forming a part of any new Deposit Account unless,
within thirty (30) days after such event, Debtor advises Secured Party, in
reasonable detail, as to the name of the institution or organization in which
such Deposit Account shall be maintained together with such Deposit Account
number.

         (t) Tax I.D. Debtor will not change its employer identification number
set forth on Schedule I of this Agreement unless it shall have given prior
written notice to Secured Party.

         6. Secured Party's Appointment as Attorney-in-Fact.

         (a) Powers. Debtor hereby irrevocably constitutes and appoints Secured
Party and any officer or agent thereof, with full power of substitution, as its
true and lawful attorney-in-fact with full irrevocable power and authority in
the place and stead of Debtor and in the name of Debtor or in its own name, from
time to time in Secured Party's discretion, for the purpose of carrying out the
terms of this Agreement, but only during the existence of an Event of Default,
to take any and all appropriate action and to execute any and all documents and
instruments which may be necessary or desirable to accomplish the purposes of
this Agreement, and, without limiting the generality of the foregoing, Debtor
hereby gives Secured Party the power and right, on behalf of Debtor, without
notice to or assent by Debtor, but only during the existence of an Event of
Default, to do the following:

                  (1) in the case of any Collateral in the name of Debtor or its
                  own name, or otherwise, to take possession of and indorse and
                  collect any checks, drafts, notes, acceptances or other
                  instruments for the payment of monies due under, or with
                  respect to, any Collateral and to file any claim or to take
                  any other action or

                                      D-11

<PAGE>   100

                  proceeding in any court of law or equity or otherwise deemed
                  appropriate by Secured Party for the purpose of collecting any
                  and all such monies due or with respect to such Collateral
                  whenever payable;

                  (2) to pay or discharge Taxes and Liens, other than Permitted
                  Encumbrances, levied or placed on or threatened against the
                  Collateral, to effect any repairs or any insurance called for
                  by the terms of this Agreement and to pay all or any part of
                  the premiums therefor and the costs thereof; and

                  (3) (a) to direct any party liable for any payment under any
                  of the Collateral to make payment of any and all monies due or
                  to become due thereunder directly to Secured Party or as
                  Secured Party shall direct; (b) to ask or demand for, collect,
                  receive payment of and receipt for, any and all monies, claims
                  and other amounts due or to become due at any time in respect
                  of or arising out of any Collateral; (c) to sign and indorse
                  any invoices, freight or express bills, bills of lading,
                  storage or warehouse receipts, drafts against debtors,
                  assignments, verifications, notices and other documents in
                  connection with any of the Collateral; (d) to commence and
                  prosecute any suits, actions or proceedings at law or in
                  equity in any court of competent jurisdiction to collect the
                  Collateral or any portion thereof and to enforce any other
                  right in respect of any Collateral; (e) to defend any suit,
                  action or proceeding brought against Debtor with respect to
                  any Collateral; (f) to settle, compromise or adjust any suit,
                  action or proceeding described in the preceding clause and, in
                  connection therewith, to give such discharges or releases as
                  Secured Party may deem appropriate; (g) to assign any
                  Trademark (along with the goodwill of the business to which
                  any such Trademark pertains), throughout the world for such
                  term or terms, on such conditions, and in such manner, as
                  Secured Party shall in its sole discretion determine; and (h)
                  generally, to sell, transfer, pledge and make any agreement
                  with respect to or otherwise deal with any of the Collateral
                  as fully and completely as though Secured Party were the
                  absolute owner thereof for all purposes, and to do, at Secured
                  Party's option and Debtor's expense, at any time, or from time
                  to time, all acts and things which Secured Party deems
                  necessary to protect, preserve or realize upon the Collateral
                  and to effect the intent of this Agreement, all as fully and
                  effectively as Debtor might do.

Debtor hereby ratifies all that said attorneys shall lawfully do or cause to be
done by virtue hereof. This power of attorney is power coupled with an interest
and shall be irrevocable until the Obligations shall have been paid in full or
this Agreement shall have been terminated.

         (b) Other Powers. Debtor also authorizes Secured Party, at any time and
from time to time, during the continuance of an Event of Default, to execute, in
connection with the sale provided for in this Section 6, any endorsements,
assignments or other instruments of conveyance or transfer with respect to the
Collateral.

                                      D-12

<PAGE>   101

         (c) No Duty on the Part of Secured Party. The powers conferred on
Secured Party hereunder are solely to protect the interests of Secured Party and
the Banks in the Collateral and shall not impose any duty upon Secured Party or
any Bank to exercise any such powers. The Banks shall be accountable only for
amounts that they actually receive as a result of the exercise of such powers,
and no Bank nor any Bank's officers, directors, employees or agents shall be
responsible to Debtor for any act or failure to act hereunder, except for its
own gross negligence or willful misconduct, it being the intent of the parties
hereto that Secured Party shall not be accountable for its own negligence.

         7. Performance by Secured Party of Company's Obligations. If Debtor
fails to perform or comply with any of its agreements contained herein and
Secured Party, as provided for by the terms of this Agreement, or any Bank shall
itself perform or comply, or otherwise cause performance or compliance, with
such agreement, the expenses of Secured Party and any such Bank incurred in
connection with such performance or compliance, together with interest thereon
at the Maximum Lawful Rate on demand shall be payable by Debtor to Secured
Party, and shall constitute obligations secured hereby.

         8. Proceeds. Upon request of Secured Party, during the continuance of
an Event of Default (a) all Proceeds received by Debtor consisting of cash,
checks and other non-cash items shall be held by Debtor in trust for Secured
Party, segregated from other funds of Debtor and shall, forthwith upon receipt
by Debtor be turned over to Secured Party for the ratable benefit of the Banks
in the exact form received by Debtor (duly endorsed by Debtor to Secured Party,
if required), and (b) any and all such Proceeds received by Secured Party
(whether from Debtor or otherwise) may, in the sole discretion of Secured Party,
be held by Secured Party as collateral security for, and/or then or at any time
thereafter may be applied by Secured Party against, the Obligations (whether
matured or unmatured), such application to be in such order as Secured Party
shall elect. Any balance of such Proceeds remaining after the Obligations shall
have been paid in full shall be paid over to Debtor or to whomsoever may be
lawfully entitled to receive the same.

         9.       Remedies.

         (a) General. If an Event of Default shall occur and be continuing,
Secured Party may exercise, in addition to all other rights and remedies granted
to it in this Agreement and in the other Loan Papers, all rights and remedies of
a secured party under the UCC. Without limiting the generality of the foregoing,
or any other right available to Secured Party hereunder, Secured Party, without
demand of performance or other demand, presentment, protest, advertisement or
notice of any kind (except any notice required by law referred to below) to or
upon Debtor or any other party (all and each of which demands, offenses,
advertisements and notices are hereby waived), may in such circumstances
forthwith collect, receive, appropriate and realize upon the Collateral, or any
part thereof, and/or may forthwith sell, lease, assign, give option or options
to purchase, or otherwise dispose of and deliver the Collateral or any part
thereof (or contract to do any of the foregoing), in one or more parcels at
public or private sale or sales, at any exchange, broker's board or office of
Secured Party or elsewhere upon such terms and conditions as it may deem
advisable and at such

                                      D-13

<PAGE>   102

prices as it may deem best, for cash or on credit or for future delivery without
assumption of any credit risk. Secured Party and each Bank shall have the right
upon any such public sale or sales, and, to the extent permitted by law, upon
any such private sale or sales, to purchase the whole or any part of the
Collateral so sold, free of any right or equity of redemption in Debtor, which
right or equity is hereby waived and released. Debtor further agrees, at Secured
Party's request, to assemble, or cause the assembly of, the Collateral and make
it available to Secured Party at places which Secured Party shall reasonably
select, whether at Debtor's premises or elsewhere. Secured Party shall apply the
net Proceeds of any such collection, recovery, receipt, appropriation,
realization or sale, after deducting all reasonable costs and expenses of every
kind incurred therein or incidental to the care or safekeeping of any of the
Collateral or in any way relating to the Collateral or the rights of Secured
Party hereunder, including, without limitation, reasonable attorneys' fees and
disbursements, to the payment in whole or in part of the Obligations, in the
manner provided by the Credit Agreement, and only after such application and
after the payment by Secured Party of any other amount required by any provision
of law, need Secured Party account for the surplus, if any, to Debtor. To the
extent permitted by applicable law, Debtor waives all claims, damages and
demands it may acquire against Secured Party arising out of the exercise by them
of any rights hereunder. If any notice of a proposed sale or other disposition
of Collateral shall be required by law, such notice shall be deemed reasonable
and proper if given at least five (5) days before such sale or other
disposition. Debtor shall remain liable for any deficiency if the Proceeds of
any sale or other disposition of the Collateral are insufficient to pay the
Obligations and the fees and disbursements of any attorneys employed by Secured
Party to collect such deficiency.

         10. Secured Party's Responsibility With Respect to Collateral. Neither
Secured Party nor any Bank shall have any duty to fix or preserve rights against
prior parties to the Collateral, and neither Secured Party nor any Bank shall
ever be liable for failure to use diligence to collect any amount payable with
respect to the Collateral, or any part thereof, but shall be liable only to
account to Debtor any amount Secured Party or any Bank may actually collect or
receive thereon and for acts constituting gross negligence or willful
misconduct. Secured Party's sole duty with respect to the custody, safekeeping
and physical preservation of the Collateral in its possession, under the UCC or
otherwise, shall be to deal with it in the same manner as Secured Party deals
with similar property for its own account. Neither Secured Party, nor any Bank
nor any of their directors, officers, employees or agents shall be liable for
failure to demand, collect or realize upon all or any part of the Collateral or
for any delay in doing so or shall be under any obligation to sell or otherwise
dispose of any Collateral upon the request of Debtor or otherwise other than
acts constituting gross negligence or willful misconduct.

         11. Waiver of Certain Rights. To the full extent that it may lawfully
so agree, Debtor agrees that it will not at any time plead, claim or take the
benefit of any appraisement, valuation, stay, extension, moratorium or
redemption law nor or hereafter in force in order to prevent or delay the
enforcement of this Agreement, or the absolute sale of all or any part of the
Collateral or the possession thereof by any purchaser at any sale hereunder, and
Debtor hereby waives the benefit of all such laws to the extent it lawfully may.

                                      D-14

<PAGE>   103

         12. Powers Coupled with an Interest. All authorizations and agencies
herein contained with respect to the Collateral are irrevocable and powers
coupled with an interest.

         13. Performance at Debtor's Expense. The cost and expense of performing
or complying with any and all of the Obligations shall be borne solely by
Debtor, subject to any specific limitations thereon provided for in the Credit
Agreement, and no portion of such cost and expense shall be, in any way and to
any extent, credited against any installment on or portion of the Obligations.

         14. Survival. Each and all of the Obligations and each and all of
Debtor's representations and warranties hereunder shall survive the execution
and delivery of this Agreement, and shall continue in full force and effect
until the Obligations shall have been paid in full.

         15. Severability. If any provision of this Agreement is held to be
illegal, invalid, or unenforceable under present or future laws effective during
the term hereof, such provision shall be fully severable, this Agreement shall
be construed and enforced as if such illegal, invalid, or unenforceable
provision had never comprised a part thereof, and the remaining provisions
thereof shall remain in full force and effect and shall not be affected by the
illegal, invalid, or unenforceable provision or by its severance therefrom so as
to achieve the original intent of Debtor and Secured Party. Furthermore, in lieu
of such illegal, invalid, or unenforceable provision there shall be added
automatically as part of this Agreement a provision as similar in terms to such
illegal, invalid, or unenforceable provision as may be possible and be legal,
valid and enforceable.

         16. Paragraph Headings. The paragraph headings used in this Agreement
are for convenience of reference only and are not to affect the construction
hereof or be taken into consideration in the interpretation hereof.

         17. Cumulative Remedies. The rights and remedies herein provided shall
be cumulative and not exclusive of any rights or remedies provided by law or in
any of the other Loan Papers.

         18. Successors and Assigns. The provisions of this Agreement shall be
binding upon and inure to the benefit of the parties hereto, the Banks parties
to the Credit Agreement and each such Persons' respective successors and
assigns; except, that Debtor may not assign or otherwise transfer any of its
rights under this Agreement.

         19. Limitation on Interest. Regardless of any provision contained in
this Agreement or in the other Loan Papers, no Bank shall be entitled to
receive, collect, or apply, as interest on the Revolving Loans, any amount in
excess of the Maximum Lawful Rate, and in the event any Bank ever receives,
collects or applies as interest any such excess, such amount which would be
deemed excessive interest shall be deemed a partial prepayment of principal and
treated hereunder as such; and if the Revolving Loan is paid in full, any
remaining excess shall promptly be paid to Debtor. In determining whether or not
the interest paid or payable under any specific contingency exceeds the Maximum
Lawful Rate, Debtor, Secured Party and each Bank shall, to the extent permitted
under applicable law, (a) characterize any nonprincipal payment as an expense,
fee or premium rather than

                                      D-15

<PAGE>   104

as interest, (b) exclude voluntary prepayments and the effects thereof and (c)
amortize, prorate, allocate and spread, in equal parts, the total amount of the
interest throughout the entire contemplated term of the Notes, so that the
interest rate is the Maximum Lawful Rate throughout the entire term of the
Notes; provided, however, that if the unpaid principal balance thereof is paid
and performed in full prior to the end of the full contemplated term thereof,
and if the interest received for the actual period of existence thereof exceeds
the Maximum Lawful Rate, the Banks shall refund to Debtor the amount of such
excess and, in such event, neither Secured Party nor any Bank shall be subject
to any penalties provided by any laws for contracting for, charging, taking,
reserving or receiving interest in excess of the Maximum Lawful Rate.

         20. GOVERNING LAW. THIS AGREEMENT, THE NOTES, AND THE OTHER LOAN PAPERS
HAVE BEEN EXECUTED AND DELIVERED IN THE STATE OF TEXAS AND SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF TEXAS AND THE LAWS OF
THE UNITED STATES OF AMERICA, EXCEPT TO THE EXTENT THAT THE LAWS OF A STATE IN
WHICH COLLATERAL IS LOCATED NECESSARILY GOVERNS (A) THE PERFECTION AND PRIORITY
OF THE LIEN AND SECURITY INTEREST CREATED HEREBY WITH RESPECT TO SUCH
COLLATERAL, AND (B) THE EXERCISE OF ANY REMEDIES (INCLUDING THE FORECLOSURE OF
SUCH LIEN AND SECURITY INTEREST) SUCH WITH RESPECT TO SUCH COLLATERAL.

         21. Notices. All notices, requests and other communications to any
party hereunder shall be in writing (including bank wire, telex, telecopy or
similar writing) and shall be given to such party at its address, telex or
telecopy number set forth in the Credit Agreement or such other address, telex
or telecopy number as such party may hereafter specify by notice to the other
party. Each such notice, request or other communication shall be effective (i)
if given by telex or telecopy, when such telex or telecopy is transmitted to the
telex or telecopy number specified in this Section 21 and the appropriate answer
back is received or receipt is otherwise confirmed, (ii) if given by mail, three
(3) Business Days after deposit in the mails with first class postage prepaid,
addressed as aforesaid or (iii) if given by any other means, when delivered at
the address specified in this Section 21.

         22. Multiple Counterparts. This Agreement may be executed in a number
of identical counterparts, each of which for all purposes is to be deemed an
original, and all of which constitute collectively, one Agreement; but in making
proof of this Agreement, it shall not be necessary to produce or account for
more than one such counterpart. It is not necessary that each party hereto
execute the same counterpart so long as identical counterparts are executed by
each such party hereto.

         23. No Waiver. No course of dealing between any Bank, Secured Party and
Debtor, nor any failure to exercise, nor any delay in exercising on the part of
Secured Party of any right hereunder or under the Loan Papers shall operate as a
waiver hereof or thereof; nor shall any single or partial exercise of any right
hereunder or thereunder preclude any other or further exercise thereof or the
exercise of any other right.

                                      D-16

<PAGE>   105

         24. Amendments and Modifications. This Agreement shall be modified or
amended only in a written document, signed by Secured Party and Debtor.

         25. FINAL AGREEMENT. THIS AGREEMENT AND THE OTHER LOAN PAPERS
COLLECTIVELY 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 BETWEEN THE PARTIES.

         26. WAIVER OF JURY TRIAL. DEBTOR, FOR ITSELF, ITS SUCCESSORS AND
ASSIGNS AND SECURED PARTY HEREBY IRREVOCABLY AND UNCONDITIONALLY WAIVE TRIAL BY
JURY IN ANY LEGAL ACTION OR PROCEEDING RELATING TO THIS AGREEMENT AND FOR ANY
COUNTERCLAIM THEREIN.

         27. SUBMISSION TO JURISDICTION; WAIVER OF SERVICE AND VENUE.

         (A) DEBTOR CONSENTS AND AGREES TO THE JURISDICTION OF ANY STATE COURT
SITTING IN THE COUNTY OF DALLAS, STATE OF TEXAS, AND TO THE JURISDICTION OF ANY
FEDERAL COURT SITTING IN THE NORTHERN DISTRICT OF TEXAS, AND WAIVES ANY
OBJECTION BASED ON VENUE OR FORUM NON CONVENIENS WITH RESPECT TO ANY ACTION
INSTITUTED THEREIN, AND AGREES THAT ANY DISPUTE CONCERNING THE RELATIONSHIP
BETWEEN SECURED PARTY OR ANY BANK, ON THE ONE HAND, AND DEBTOR, ON THE OTHER
HAND, OR THE CONDUCT OF ANY PARTY IN CONNECTION WITH THIS AGREEMENT OR OTHERWISE
SHALL BE HEARD ONLY IN THE COURTS DESCRIBED ABOVE.

         (B) DEBTOR HEREBY WAIVES PERSONAL SERVICE OF ANY AND ALL PROCESS UPON
IT AND CONSENTS THAT ALL SUCH SERVICE OF PROCESS MAY BE MADE BY CERTIFIED MAIL
OR HAND DELIVERY TO DEBTOR AT ITS ADDRESS SET FORTH IN THE SIGNATURE PAGE
HERETO. DEBTOR HEREBY CONSENTS TO SERVICE OF PROCESS AS AFORESAID.

         (C) NOTHING IN THIS SECTION 27 SHALL AFFECT THE RIGHT OF SECURED PARTY
OR ANY BANK TO SERVE LEGAL PROCESS IN ANY OTHER MANNER PERMITTED BY LAW OR
AFFECT THE RIGHT OF SECURED PARTY OR ANY BANK TO BRING ANY ACTION OR PROCEEDING
AGAINST DEBTOR OR ANY OF ITS PROPERTY IN THE COURTS OR ANY OTHER JURISDICTION.

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

                                   Debtor:

                                   HUMPHREY-HILL, L.P.,
                                   a Texas limited partnership

                                   By:  EXCO Resources, Inc.,
                                        a Texas corporation,
                                        its general partner

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

                                      D-17

<PAGE>   106

                                   SCHEDULE I

               PRINCIPAL PLACE OF BUSINESS/CHIEF EXECUTIVE OFFICE
                       AND EMPLOYER IDENTIFICATION NUMBER

EXCO Resources, Inc.
5735 Pineland, Suite 235
Dallas, Texas 75231
Taxpayer Identification Number: 75-2825676

                                      D-18

<PAGE>   107

                                   SCHEDULE II

                                DEPOSIT ACCOUNTS

                                      D-19

<PAGE>   108

                                    EXHIBIT E

                              REQUEST FOR BORROWING

         Reference is made to that certain Credit Agreement dated as of March
24, 2000 (as from time to time amended, the "Agreement"), among Humphrey-Hill,
L.P. ("Borrower"), Bank of America, N.A., as Administrative Agent
("Administrative Agent"), and the financial institutions listed on Schedule 1
thereto, as Banks ("Banks"). Terms which are defined in the Agreement and which
are used but not defined herein are used herein with the meanings given them in
the Agreement. Pursuant to the terms of the Agreement, Borrower hereby requests
a Borrowing in the amount of $_____________ to be advanced on          ,      .

         Borrower requests that the Borrowing to be made hereunder shall be [A
BASE RATE BORROWING] [A EURODOLLAR BORROWING] and shall have the Interest
Periods all as set forth below:

<TABLE>
<CAPTION>
         Type of Borrowing                           Aggregate Amount                   Interest Period
         -----------------                           ----------------                   ---------------
<S>                                                 <C>                                <C>

---------------------------------                -----------------------             ----------------------

---------------------------------                -----------------------             ----------------------

---------------------------------                -----------------------             ----------------------
</TABLE>

         Borrower and the Authorized Officer of Borrower signing this instrument
hereby certify that:

                  (a) Such officer is the duly elected, qualified and acting
         officer of Borrower as indicated below such officers signature hereto.

                  (b) The representations and warranties of Borrower set forth
         in the Agreement and the Loan Papers delivered to Administrative Agent
         and Banks are true and correct on and as of the date hereof, with the
         same effect as though such representations and warranties had been made
         on and as of the date hereof or, if such representations and warranties
         are expressly limited to particular dates, as of such particular dates.
         Since the date of the last financial reports of Borrower delivered to
         each Bank pursuant to Section 9.1 of the Agreement, there has not
         occurred any event or condition which has resulted in, or could
         reasonably be expected to result in, a Material Adverse Change.

                  (c) There does not exist on the date hereof, any condition or
         event which constitutes a Default or Event of Default, nor will any
         such Default or Event of Default exist

                                       E-1

<PAGE>   109

         upon Borrower's receipt and application of the proceeds requested
         hereby. Borrower will use the proceeds hereby requested in compliance
         with the applicable provisions of the Agreement.

                  (d) Borrower has performed and complied with all agreements
         and conditions in the Agreement and the other Loan Papers required to
         be performed or complied with by Borrower on or prior to the date
         hereof, and each of the conditions precedent to the Borrowing contained
         in the Agreement remain satisfied in all material respects.

                  (e) After giving effect to the Borrowing requested hereby, the
         Outstanding Credit will not be in excess of the Borrowing Base on the
         date requested for the making of such Borrowing.

                  (f) The Availability on the date hereof, and prior to giving
         effect to the Borrowing requested hereby, is $_______________________.

                  (g) The Borrowing requested herein will be used for the
         following purposes:

                           [ ]      Pay a portion of the Purchase Price for the
                                    Nebraska Acquisition [NOT TO EXCEED
                                    $6,800,000].

                           [ ]      Other general corporate purposes in the
                                    amount of $____________ [NOT TO EXCEED THE
                                    AVAILABILITY].

         IN WITNESS WHEREOF, this instrument is executed as of March 24, 2000.

                                     HUMPHREY-HILL, L.P.,
                                     a Texas limited partnership

                                     By:   EXCO Resources, Inc.,
                                           a Texas corporation,
                                           its general partner

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

                                       E-2

<PAGE>   110

                                    EXHIBIT F

                          REQUEST FOR LETTER OF CREDIT

         Reference is made to that certain Credit Agreement dated as of March
24, 2000 (as from time to time amended, the "Agreement"), among Humphrey-Hill,
L.P. ("Borrower"), Bank of America, N.A., as Administrative Agent
("Administrative Agent"), and the financial institutions listed on Schedule 1
thereto, as Banks ("Banks"). Terms which are defined in the Agreement and which
are used but not defined herein are used herein with the meanings given them in
the Agreement.

         Pursuant to the terms of the Agreement, Borrower hereby requests
Administrative Agent to issue a Letter of Credit for the account of Borrower as
follows:

<TABLE>
<S>                                                           <C>
                  Type of Commitment:
                  ------------------

                  Requested Amount                            $
                                                                ------------------------
                  Requested Date of Issuance
                                                                ------------------------
                  Requested Expiration Date
                                                                ------------------------
                  Summary of Terms
                  (provide a brief description
                  of the purpose of such Letter
                  of Credit and the conditions
                  under which the drafts under
                  such Letter of Credit are
                  to be available)
                                                                ------------------------
                  Beneficiary (Name/Address)
                                                                ------------------------
                                                                ------------------------
                                                                ------------------------
                                                                ------------------------
                                                                ------------------------
</TABLE>

         Such Letter of Credit is more particularly described in the Letter of
Credit Application and Agreement of Administrative Agent which is attached
hereto.

         Borrower and the Authorized Officer of Borrower signing this instrument
hereby certify that:

                  (a) Such officer is the duly elected, qualified and acting
         officer of Borrower as indicated below such officer's signature hereto.

                  (b) The representations and warranties of Borrower set forth
         in the Agreement and the other Loan Papers delivered to Administrative
         Agent and each Bank are true and correct on and as of the date hereof,
         with the same effect as though such representations and warranties had
         been made on and as of the date hereof, or if such representations and
         warranties are expressly limited to particular dates, as of such
         particular dates. No Material

                                       F-1

<PAGE>   111

         Adverse Change has occurred since the date of the last financial
         reports of Borrower delivered to Banks pursuant to Section 9.1 of the
         Agreement.

                  (c) There does not exist on the date hereof any condition or
         event which constitutes a Default or Event of Default, nor will any
         such Default or Event of Default exist upon the issuance of the Letter
         of Credit requested hereby. Borrower will use the Letter of Credit
         solely for purposes permitted by the Agreement.

                  (d) Borrower has performed and complied with all agreements
         and conditions in the Agreement and the other Loan Papers required to
         be performed or complied with by Borrower on or prior to the date
         hereof, and each of the conditions precedent to the issuance of Letters
         of Credit contained in the Agreement remain satisfied in all material
         respects.

                  (e) After the issuance of the Letter of Credit requested
         hereby, the Outstanding Credit will not be in excess of the Borrowing
         Base in effect on the date requested for the issuance of such Letter of
         Credit.

         IN WITNESS WHEREOF, this instrument is executed as of March 24, 2000.

                                     HUMPHREY-HILL, L.P.,
                                     a Texas limited partnership

                                     By:   EXCO Resources, Inc.,
                                           a Texas corporation,
                                           its general partner

                                           By:
                                               --------------------------------
                                           Its:
                                                -------------------------------

                                       F-2

<PAGE>   112

                                    EXHIBIT G

                  NOTICE OF CONTINUATION AND CONVERSION NOTICE

         Reference is made to that certain Credit Agreement dated as of March
24, 2000 (as from time to time amended, the "Agreement"), among Humphrey-Hill,
L.P. ("Borrower"), Bank of America, N.A., as Administrative Agent
("Administrative Agent"), and the financial institutions listed on Schedule 1
thereto, as Banks ("Banks"). Terms which are defined in the Agreement and which
are used but not defined herein are used herein with the meanings given them in
the Agreement.

         [ ]      Reference is hereby made to the existing Eurodollar Loan
                  outstanding under the Agreement in the amount of $________
                  which is subject to an Interest Period expiring on
                  _________________, _____. Borrower hereby requests that on the
                  expiration of such Interest Period the portion of the
                  principal of such Eurodollar Loan which is subject to such
                  Interest Period be made the subject of [ ] the Base Rate Loan
                  or [ ] a Eurodollar Loan having an Interest Period of
                  ____ months.

         [ ]      Borrower hereby requests that on ____________, _____, a
                  portion of the principal of the Base Rate Loan in the amount
                  of $__________ be made the subject of a Eurodollar Loan having
                  an Interest Period of ______ (__) months.

         Borrower and the Authorized Officer of Borrower signing this instrument
hereby certify that:

                  (a) Such officer is the duly elected, qualified and acting
         officer of Borrower as indicated below such officer's signature hereto;

                  (b) There does not exist on the date hereof any condition or
         event which constitutes a Default or Event of Default; and

                  (c) The representations and warranties of Borrower set forth
         in the Agreement and the Loan Papers delivered to Administrative Agent
         and each Bank are true and correct on and as of the date hereof, with
         the same effect as though such representations and warranties had been
         made on and as of the date hereof or, if such representations and
         warranties are expressly limited to particular dates, as of such
         particular dates.

                                       G-1

<PAGE>   113

         IN WITNESS WHEREOF, this instrument is executed as of _____________,
_____.

                                     HUMPHREY-HILL, L.P.,
                                     a Texas limited partnership

                                     By:   EXCO Resources, Inc.,
                                           a Texas corporation,
                                           its general partner

                                           By:
                                               --------------------------------
                                           Its:
                                                -------------------------------

                                       G-2

<PAGE>   114

                                    EXHIBIT H

                       CERTIFICATE OF OWNERSHIP INTERESTS

         This Certificate of Ownership Interests (this "Certificate") is
executed and delivered pursuant to that certain Credit Agreement dated as of
March 24, 2000 (as amended from time to time, the "Agreement"), among
Humphrey-Hill, L.P. ("Borrower"), Bank of America, N.A., as Administrative Agent
("Administrative Agent"), and the financial institutions listed on Schedule I
thereto, as Banks ("Banks"). Unless otherwise defined herein, all capitalized
terms shall have the meanings given such terms in the Agreement.

         In order to induce Banks to extend credit to Borrower under the
Agreement, Borrower hereby represents and warrants to Administrative Agent and
each Bank that (a) Exhibit A attached hereto is a complete and accurate
description of all Mineral Interests described in the Initial Reserve Report
including all Nebraska Properties (the "Initial Borrowing Base Properties"), (b)
after giving effect to the closing of the Nebraska Acquisition, Borrower will
hold good and defensible title, subject only to Permitted Encumbrances, to the
Initial Borrowing Base Properties, (c) Borrower's share of (i) the costs for
each of the Initial Borrowing Base Properties is not greater than the decimal
fraction set forth in the Initial Reserve Report before and after payout, as the
case may be, and described therein by the respective designations "working
interests," "WI," "gross working interest," "GWI," or similar terms (except in
such cases where there is a corresponding increase in the net revenue interest),
and (ii) production from, allocated to, or attributed to each of such Initial
Borrowing Base Properties is not less than the decimal fraction set forth in the
Initial Reserve Report before and after payout, as the case may be, and
described therein by the designations net revenue interest, NRI, or similar
terms, and (d) to Borrower's actual knowledge after due inquiry, each well
drilled in respect of each of the Initial Borrowing Base Properties described in
the Initial Reserve Report (A) is capable of, and is presently, producing
Hydrocarbons in commercially profitable quantities, and Borrower is receiving
(or will receive) payments for its share of production, with no funds in respect
of any thereof being presently held in suspense, other than any such funds being
held in suspense pending delivery of appropriate division orders, and (B) has
been drilled, bottomed, completed and operated in compliance with all applicable
Laws and no such well which is currently producing Hydrocarbons is subject to
any penalty in production by reason of such well having produced in excess of
its allowable production.

                                       H-1

<PAGE>   115

         Borrower acknowledges and agrees that each Bank is relying on this
Certificate and the representations and warranties herein contained in extending
credit under the Agreement and but for Borrower's execution and delivery of this
Certificate, Banks would not extend credit under the Agreement.

         Executed as of the 24th day of March, 2000.

                                     HUMPHREY-HILL, L.P.,
                                     a Texas limited partnership

                                     By:   EXCO Resources, Inc.,
                                           a Texas corporation,
                                           its general partner

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

                                       H-2

<PAGE>   116

                                    EXHIBIT A

                                [To be attached]

                                       H-3

<PAGE>   117

                                   EXHIBIT I-1

                         FINANCIAL OFFICER'S CERTIFICATE

         The undersigned, the Chief Financial Officer of EXCO Resources, Inc., a
Texas corporation ("EXCO") hereby (a) delivers this Certificate pursuant to
Section 9.1(c) of that certain Credit Agreement (the "Agreement") dated as of
March 24, 2000, among Humphrey-Hill, L.P., Bank of America, N.A., as
Administrative Agent ("Administrative Agent"), and the financial institutions
listed on Schedule 1 thereto, as Banks ("Banks"), and (b) certifies to each
Bank, with the knowledge and intent that Banks may, without any independent
investigation, rely fully on the matters herein in connection with the
Agreement, as follows:

         1. Attached hereto as Schedule I are the financial statements of EXCO
as of and for the Fiscal [ ] Year [ ] Quarter (check one) ended ____________,
____.

         2. Such financial statements are true and correct in all materials
respects, have been prepared on a consistent basis in accordance with GAAP
(except as otherwise noted therein) and fairly present the financial condition
of EXCO as of the date indicated therein and the results of operations for the
respective periods indicated therein.

         3. Except as described on Schedule II hereto, the representations and
warranties of EXCO set forth in the Loan Papers delivered to Administrative
Agent and each Bank are true and correct on and as of the date hereof, with the
same effect as though such representations and warranties had been made on and
as of the date hereof or, if such representations and warranties are expressly
limited to particular dates, as of such particular dates.

         Unless otherwise defined herein, all capitalized terms used herein
shall have the meaning given such terms in the Agreement.

         IN WITNESS WHEREOF, the undersigned has duly executed this Financial
Officer's Certificate as of March 24, 2000.

                                     EXCO Resources, Inc., a Texas corporation

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

                                      I-1-1

<PAGE>   118

                                   Schedule I

                              Financial Statements
                                (to be attached)

                                      I-1-2

<PAGE>   119

                                   Schedule II

                Qualifications to Representations and Warranties

                                      I-1-3

<PAGE>   120

                                   EXHIBIT I-2

                         FINANCIAL OFFICER'S CERTIFICATE

         The undersigned, the Chief Financial Officer of EXCO Resources, Inc.,
the General Partner of Humphrey-Hill, L.P., a Texas limited partnership
("Borrower") hereby (a) delivers this Certificate pursuant to Section 9.1(c) of
that certain Credit Agreement (the "Agreement") dated as of March 24, 2000,
among Borrower, Bank of America, N.A., as Administrative Agent ("Administrative
Agent"), and the financial institutions listed on Schedule 1 thereto, as Banks
("Banks"), and (b) certifies to each Bank, with the knowledge and intent that
Banks may, without any independent investigation, rely fully on the matters
herein in connection with the Agreement, as follows:

         1. Attached hereto as Schedule I are the financial statements of
Borrower as of and for the Fiscal [ ] Year [ ] Quarter (check one) ended
____________, ____.

         2. Such financial statements are true and correct in all materials
respects, have been prepared on a consistent basis in accordance with GAAP
(except as otherwise noted therein) and fairly present the financial condition
of Borrower as of the date indicated therein and the results of operations for
the respective periods indicated therein.

         3. Attached hereto as Schedule II are detailed calculations used by
Borrower to establish that Borrower was in compliance with the requirements of
Article 11 of the Agreement on the date of the financial statements attached as
Schedule I hereto.

         4. Unless otherwise disclosed on Schedule III attached hereto and
incorporated herein by reference for all purposes, neither a Default nor an
Event of Default has occurred which is in existence on the date hereof;
provided, that for any Default or Event of Default disclosed on Schedule III
attached hereto, Borrower is taking or proposes to take the action to cure such
Default or Event of Default set forth on Schedule III.

         5. On the date of the financial statements attached hereto as Schedule
I (a) (check one) [ ] there is no Material Gas Imbalance or [ ] the amount of
the net gas imbalances under Gas Balancing Agreements to which Borrower or any
of its Subsidiaries is a party or by which any Mineral Interests owned by
Borrower or any of its Subsidiaries is bound is ____________, and (b) the
aggregate amount of all Advance Payments received under Advance Payment
Contracts to which Borrower or any of its Subsidiaries is a party or by which
any Mineral Interests owned by Borrower or any of its Subsidiaries is bound
which have not been satisfied by delivery of production, if any, is
______________.

         6. Attached hereto as Schedule IV is a summary of the Hedge
Transactions to which Borrower or any of its Subsidiaries is a party on the date
of the financial statements attached hereto as Schedule I.

                                      I-2-1

<PAGE>   121

         7. Except as described on Schedule V hereto, the representations and
warranties of Borrower set forth in the Agreement and the Loan Papers delivered
to Administrative Agent and each Bank are true and correct on and as of the date
hereof, with the same effect as though such representations and warranties had
been made on and as of the date hereof or, if such representations and
warranties are expressly limited to particular dates, as of such particular
dates.

         Unless otherwise defined herein, all capitalized terms used herein
shall have the meaning given such terms in the Agreement.

         IN WITNESS WHEREOF, the undersigned has duly executed this Financial
Officer's Certificate as of March 24, 2000.

                                             EXCO RESOURCES, INC.,
                                             a Texas corporation

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

                                      I-2-2

<PAGE>   122

                                   Schedule I

                              Financial Statements
                                (to be attached)

                                      I-2-3

<PAGE>   123

                                   Schedule II

                             Compliance Calculations
                                (to be attached)

                                      I-2-4

<PAGE>   124

                                  Schedule III

                            Defaults/Remedial Action
                                (to be attached)

                                      I-2-5

<PAGE>   125

                                   Schedule IV

                          Summary of Hedge Transactions
                                (to be attached)

                                      I-2-6

<PAGE>   126

                                   Schedule V

                Qualifications to Representations and Warranties

                                      I-2-7

<PAGE>   127

                                    EXHIBIT J

                            ASSIGNMENT AND ACCEPTANCE

         Reference is made to that certain Credit Agreement dated as of March
24, 2000 (the "Agreement") among Humphrey-Hill, L.P. ("Borrower"), Bank of
America, N.A., as Administrative Agent ("Administrative Agent") and the
financial institutions listed on Schedule 1 thereto, as Banks ("Banks"). Terms
defined in the Agreement are used herein with the same meaning.

         The "Assignor" and the "Assignee" referred to on Schedule 1 agree as
follows:

         1. Assignor hereby sells and assigns to Assignee, without recourse and
without representation or warranty except as expressly set forth herein, and
Assignee hereby purchases and assumes from Assignor, an interest in and to
Assignor's rights and obligations under the Agreement and the other Loan Papers
as of the date hereof equal to the percentage interest specified on Schedule 1
of all outstanding rights and obligations under the Agreement and the other Loan
Papers. After giving effect to such sale and assignment, Assignee's Commitment,
Assignee's Commitment Percentage and the principal amount of the Revolving Loan
owing to Assignee will be as set forth on Schedule 1.

         2. 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 Loan Papers or
the execution, legality, validity, enforceability, genuineness, sufficiency or
value of the Loan Papers 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 Borrower or the performance or
observance by Borrower of any of its obligations under the Loan Papers or any
other instrument or document furnished pursuant thereto; and (iv) attaches the
Note held by Assignor and requests that Administrative Agent exchange such Note
for new Notes payable to the order of Assignee in an amount equal to the
Commitment assumed by Assignee pursuant hereto and to Assignor in an amount
equal to the Commitment retained by Assignor, if any, as specified on Schedule
1.

         3. Assignee (i) confirms that it has received a copy of the Agreement,
together with copies of the financial statements referred to in Section 9.1
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
Administrative Agent, Assignor or any other Bank 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 Agreement; (iii)
confirms that it is an Eligible Assignee; (iv) appoints and authorizes
Administrative Agent to take such action as agent on its behalf and to exercise
such powers and

                                       J-1

<PAGE>   128

discretion under the Agreement as are delegated to the Administrative 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 Agreement are required to
be performed by it as a Bank; and (vi) attaches any U.S. Internal Revenue
Service or other forms required under Section 4.6(d).

         4. Following the execution of this Assignment and Acceptance, it will
be delivered to Administrative Agent for acceptance and recording by
Administrative Agent. The effective date for this Assignment and Acceptance (the
"Effective Date") shall be the date of acceptance hereof by Administrative
Agent, unless otherwise specified on Schedule 1.

         5. Upon such acceptance and recording by Administrative Agent, as of
the Effective Date, (i) Assignee shall be a party to the Agreement and, to the
extent provided in this Assignment and Acceptance, have the rights and
obligations of a Bank thereunder, and (ii) Assignor shall, to the extent
provided in this Assignment and Acceptance, relinquish its rights and be
released from its obligations under the Agreement.

         6. Upon such acceptance and recording by Administrative Agent, from and
after the Effective Date, Administrative Agent shall make all payments under the
Agreement and the Notes in respect of the interest assigned hereby (including,
without limitation, all payments of principal, interest and commitment fees with
respect thereto) to Assignee. Assignor and Assignee shall make all appropriate
adjustments in payments under the Agreement and the 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 State of Texas.

         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 Schedule 1 to this Assignment and Acceptance by telecopier shall
be effective as delivery of a manually executed counterpart of this Assignment
and Acceptance.

         IN WITNESS WHEREOF, Assignor and Assignee have caused Schedule 1 to
this Assignment and Acceptance to be executed by their officers thereunto duly
authorized as of the date specified thereon.

                                       J-2

<PAGE>   129

                                   SCHEDULE 1
                                       to
                            ASSIGNMENT AND ACCEPTANCE

<TABLE>
<S>                                                          <C>
Percentage interest assigned:                                         %
                                                              --------

Assignee's Commitment:                                        $
                                                               -------

Assignee's Commitment Percentage:                                     %
                                                              --------

Aggregate outstanding principal amount
  of Revolving Loans assigned:                                $
                                                               -------

Principal amount of Note payable to Assignee:                 $
                                                               -------

Principal amount of Note payable to Assignor:                 $
                                                               -------

         Effective Date (if other than date
            of acceptance by Administrative Agent):                    *       , 19
                                                                        -------    --
</TABLE>

                                             [NAME OF ASSIGNOR], as Assignor

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

                                             Dated:                    , 19
                                                   --------------------    ---

                                             [NAME OF ASSIGNEE], as Assignee

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

                                             Domestic Lending Office:

                                             Eurodollar Lending Office:

                                       J-3

<PAGE>   130

* This date should be no earlier than five Domestic Business Days after the
  delivery of this Assignment and Acceptance to the Administrative Agent.

Accepted and Approved
this 24th day of March, 2000

BANK OF AMERICA, N.A., as Administrative Agent

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

Approved this ____ day
of ____________, _____

HUMPHREY-HILL, L.P.,
a Texas limited partnership

By:      EXCO Resources, Inc.,
         a Texas corporation,
         its general partner

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

                                       J-4

<PAGE>   131

                                    EXHIBIT K

                                PLEDGE AGREEMENT

THIS PLEDGE AGREEMENT (this "Agreement") is made as of March 24, 2000 by Taurus
Acquisition, Inc., a Texas corporation (herein called "Pledgor"), in favor of
Bank of America, N.A., as Administrative Agent for the ratable benefit of Banks
(as defined below) (herein called "Pledgee").

                              W I T N E S S E T H:

         WHEREAS, Pledgor, Humphrey-Hill, L.P., a Texas limited partnership
("Borrower"), Pledgee, Bank of America, N.A., as Administrative Agent, and Banks
are parties to a Credit Agreement dated as of March 24, 2000, pursuant to which
Banks have made (or will make) a revolving credit loan to Borrower and agreed to
issue and participate in letters of credit issued on behalf of Borrower (as from
time to time amended, herein called the "Credit Agreement");

         WHEREAS, it is a condition to the agreement of Banks to extend credit
under the Credit Agreement that Pledgor execute and deliver this Agreement in
favor of Pledgee for the benefit of Banks; and

         WHEREAS, the board of directors of Pledgor has determined that
Pledgor's execution, deliver and performance of this Agreement may reasonably be
expected to benefit Pledgor, directory or indirectly, and are in the best
interests of Pledgor.

         NOW, THEREFORE, in consideration of the premises and in order to induce
Banks to extend credit under the Credit Agreement, Pledgor hereby agrees with
Pledgee as follows:

                                   ARTICLE I.

                           Definitions and References

         Section 1.1 General Definitions. As used herein, the terms "Agreement,"
"Borrower," "Credit Agreement," "Pledgee," and "Pledgor," shall have the
meanings indicated above, and the following terms shall have the following
meanings:

         "Bank" means any financial institution reflected on Schedule 1 to the
Credit Agreement and its successors and assigns, and "Banks" shall mean all
Banks.

         "Code" means the Uniform Commercial Code in effect in the State of
Texas on the date hereof.

                                       K-1

<PAGE>   132

         "Collateral" means all property of whatever type, in which Pledgee at
any time has a security interest pursuant to Section 2.1.

         "Commitment" means the agreement or commitment by Banks to make loans
or otherwise extend credit to Borrower under the Credit Agreement, and any other
agreement, commitment, statement of terms or other document contemplating the
making of loans or advances or other extension of credit by Banks to or for the
account of Borrower which is now or at any time hereafter intended to be secured
by the Collateral under this Agreement.

         "Equity" means shares of capital stock or a partnership, profits,
capital or member interest, or options, warrants or any other right to
substitute for or otherwise acquire the capital stock or a partnership, profits,
capital or member interest of Borrower.

         "Obligation Documents" means the Credit Agreement, the Notes, the other
Loan Papers, and all other documents and instruments under, by reason of which,
or pursuant to which, any or all of the Obligations are evidenced, governed,
secured, or otherwise dealt with, and all other agreements, certificates, and
other documents, instruments and writings heretofore or hereafter delivered in
connection herewith or therewith.

         "Obligations" means all present and future indebtedness, obligations
and liabilities of whatever type which are or shall be secured pursuant to
Section 2.2.

         "Other Liable Party" means any Person, other than Borrower, who may now
or may at any time hereafter be primarily or secondarily liable for any of the
Obligations or who may now or may at any time hereafter have granted to Pledgee
or Banks a Lien upon any property as security for the Obligations.

         "Pledged Equity" has the meaning given it in Section 2.1.

         Section 1.2 Other Definitions. Reference is hereby made to the Credit
Agreement for a statement of the terms thereof. All capitalized terms used in
this Agreement which are defined in the Credit Agreement and not otherwise
defined herein shall have the same meanings herein as set forth therein. All
terms used in this Agreement which are defined in the Code and not otherwise
defined herein or in the Credit Agreement shall have the same meanings herein as
set forth therein, except where the context otherwise requires.

         Section 1.3 Exhibits. All exhibits attached to this Agreement are a
part hereof for all purposes.

         Section 1.4 Amendment of Defined Instruments. Unless the context
otherwise requires or unless otherwise provided herein, references in this
Agreement to a particular agreement, instrument or document also refer to and
include all renewals, extensions, amendments, modifications, supplements or
restatements of any such agreement, instrument or document,

                                       K-2

<PAGE>   133

provided that nothing contained in this Section 1.4 shall be construed to
authorize any Person to execute or enter into any such renewal, extension,
amendment, modification, supplement or restatement.

         Section 1.5 References and Titles. All references in this Agreement to
Exhibits, Articles, Sections, subsections, and other subdivisions refer to the
Exhibits, Articles, Sections, subsections and other subdivisions of this
Agreement unless expressly provided otherwise. Titles appearing at the beginning
of any subdivision are for convenience only and do not constitute any part of
any such subdivision and shall be disregarded in construing the language
contained in this Agreement. The words "this Agreement," "herein," "hereof,"
"hereby," "hereunder" and words of similar import refer to this Agreement as a
whole and not to any particular subdivision unless expressly so limited. The
phrases "this Section" and "this subsection" and similar phrases refer only to
the Sections or subsections hereof in which the phrase occurs. The word "or" is
not exclusive, and the word "including" (in all of its forms) means "including
without limitation". Pronouns in masculine, feminine and neuter gender shall be
construed to include any other gender, and words in the singular form shall be
construed to include the plural and vice versa unless the context otherwise
requires.

                                   ARTICLE II.

                                Security Interest

         Section 2.1 Grant of Security Interest. As collateral security for all
of the Obligations, Pledgor hereby pledges and assigns to Pledgee and grants to
Pledgee a continuing first priority security interest for the benefit of Banks
in and to all of the following rights, interests and property:

         (a) all of the issued and outstanding Equity of Borrower now owned or
hereafter acquired by Pledgor including, without limitation, the Equity of
Borrower owned by Pledgor on the date hereof (all of the foregoing being herein
sometimes called the "Pledged Equity");

         (b) any and all proceeds or other sums arising from or by virtue of,
and all dividends and distributions (cash or otherwise) payable and/or
distributable with respect to, all or any of the Pledged Equity described in
clause (a) preceding; and

         (c) all cash, securities, dividends and other property at any time and
from time to time receivable or otherwise distributed in respect of or in
exchange for any or all of the Pledged Equity described in clause (a) hereof and
any other property substituted or exchanged therefor.

         Section 2.2 Obligations Secured. The security interest created hereby
in the Collateral constitutes continuing collateral security for all of the
following obligations, indebtedness and liabilities, whether now existing or
hereafter incurred:

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         (a) Credit Agreement Indebtedness. The payment by Borrower, as and when
due and payable, of all amounts from time to time owing by Borrower under or in
respect of the Credit Agreement, the Notes or any of the other Obligation
Documents.

         (b) Renewals. All renewals, extensions, amendments, modifications,
supplements, or restatements of, or substitutions for, any of the foregoing.

         (c) Performance. The due performance and observance by Borrower of all
of its other obligations from time to time existing under or in respect of any
of the Obligation Documents.

         (d) Hedge Transactions. The payment and performance of any and all
present or future obligations of Borrower according to the terms of any present
or future Hedge Transaction, including, without limitation, any present or
future swap agreements, cap, floor, collar, exchange, transaction, forward
agreement or other exchange or protection agreements relating to crude oil,
natural gas or other Hydrocarbons, or any option with respect to any such
transaction now existing or hereafter entered into between and/or among Pledgor,
Borrower, Pledgee, any Bank or any affiliate of any of the foregoing.

                                  ARTICLE III.

                    Representations Warranties and Covenants

         Section 3.1 Representations and Warranties. Pledgor represents and
warrants as follows:

         (a) Ownership and Liens. Pledgor has good and marketable title to the
Collateral free and clear of all Liens, encumbrances or adverse claims, except
for the security interest created by this Agreement. No effective financing
statement or other instrument similar in effect covering all or any part of the
Collateral is on file in any recording office except such as have been filed in
favor of Pledgee relating to this Agreement.

         (b) No Conflicts or Consents. Neither the ownership or the intended use
of the Collateral by Pledgor, nor the grant of the security interest by Pledgor
to Pledgee herein, nor the exercise by Pledgee of its rights or remedies
hereunder, will (i) conflict with any provision of (a)any domestic or foreign
law, statute, rule or regulation, (b) the articles of incorporation, certificate
of limited partnership, partnership agreement, regulations, charter or bylaws of
Pledgor, or (c) any agreement, judgment, license, order or permit applicable to
or binding upon Pledgor, or (ii) result in or require the creation of any Lien,
charge or encumbrance upon any assets or properties of Pledgor except as
expressly contemplated in the Obligation Documents. Except as expressly
contemplated in the Obligation Documents, no consent, approval, authorization or
order of, and no notice to or filing with, any court, Governmental Authority or
third party is required in

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connection with the grant by Pledgor of the security interest herein, or the
exercise by Pledgee of its rights and remedies hereunder.

         (c) Security Interest. Pledgor has and will have at all times full
right, power and authority to grant a security interest in the Collateral to
Pledgee in the manner provided herein, free and clear of any Lien, adverse
claim, or encumbrance. This Agreement creates a valid and binding security
interest in favor of Pledgee in the Collateral securing the Obligations. The
taking possession by Pledgee (for the ratable benefit of Banks) of all
certificates, instruments and cash constituting Collateral from time to time and
the filing of the financing statements delivered concurrently herewith by
Pledgor to Pledgee will perfect, and establish the first priority of, Pledgee's
security interest hereunder in the Collateral securing the Obligations. No
further or subsequent filing, recording, registration, other public notice or
other action is necessary or desirable to perfect or otherwise continue,
preserve or protect such security interest except for continuation statements or
filings as contemplated in Section 3.3(b).

         (d) Pledged Equity. (i) Pledgor is the legal and beneficial owner of
the Pledged Equity issued by Borrower, (ii) the Pledged Equity is duly
authorized and issued, fully paid and non-assessable, and all documentary, stamp
or other Taxes or fees owing in connection with the issuance, transfer and/or
pledge thereof hereunder have been paid, (iii) no dispute, right of setoff,
counterclaim or defense exists with respect to all or any part of the Pledged
Equity, (iv) the Pledged Equity is free and clear of all Liens, options,
warrants, puts, calls or other rights of third Persons, and restrictions, other
than (a) those Liens arising under this Agreement or any other of the Loan
Papers and Liens for Taxes not yet due and payable, and (b) restrictions on
transferability imposed by applicable state and federal securities Laws, (v)
Pledgor has full right and authority to pledge the Pledged Equity for the
purposes and upon the terms set out herein, (vi) certificates (or other evidence
acceptable to Pledgee) representing the Pledged Equity have been delivered to
Pledgee, together with a duly executed blank stock power (as applicable) with
signatures guaranteed, for each certificate, and (vii) Borrower has not issued,
and there are not outstanding, any options, warrants or other rights to acquire
capital stock, membership interests, or partnership interests of Borrower.

         Section 3.2 Affirmative Covenants. Unless Pledgee shall otherwise
consent in writing, Pledgor will at all times comply with the covenants
contained in this Section 3.2 from the date hereof and so long as any part of
the Obligations or Commitments is outstanding.

         (a) Ownership and Liens. Pledgor will maintain good and marketable
title to all Collateral free and clear of all Liens encumbrances or adverse
claims, except for the security interest created by this Agreement and the
security interests and other encumbrances expressly permitted by the Credit
Agreement. Pledgor will cause to be terminated any financing statement or other
registration with respect to the Collateral, except such as may exist or as may
have been filed in favor of Pledgee. Pledgor will defend Pledgee's right, title
and special property and security interest in and to the Collateral against the
claims of any Person.

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         (b) Further Assurances. Pledgor will, at its expense and at any time
and from time to time, promptly execute and deliver all further instruments and
documents and take all further action that may be necessary or desirable or that
Pledgee may request in order (i) to perfect and protect the security interest
created or purported to be created hereby and the first priority of such
security interest; (ii) to enable Pledgee to exercise and enforce its rights and
remedies hereunder in respect of the Collateral; or (iii) to otherwise effect
the purposes of this Agreement, including, without limitation: (a) executing and
filing such financing or continuation statements, or amendments thereto, as may
be necessary or desirable or that Pledgee may request in order to perfect and
preserve the security interest created or purported to be created hereby; and
(b) furnishing to Pledgee from time to time statements and schedules further
identifying and describing the Collateral and such other reports in connection
with the Collateral as Pledgee may reasonably request, all in reasonable detail.

         (c) Delivery of Pledged Equity. All certificates, instruments and
writings evidencing the Pledged Equity shall be delivered to Pledgee on or prior
to the execution and delivery of this Agreement. All other certificates,
instruments and writings hereafter evidencing or constituting Pledged Equity
shall be delivered to Pledgee promptly upon the receipt thereof by or on behalf
of Pledgor. All such Pledged Equity shall be held by or on behalf of Pledgee
pursuant hereto and shall be delivered in the same manner and with the same
effect as described in Section 2.1 and Section 3.1 hereof. Upon delivery, such
equity interests shall thereupon constitute "Pledged Equity" and shall be
subject to the Liens herein created, for the purposes and upon the terms and
conditions set forth in this Agreement and the other Loan Papers.

         (d) Proceeds of Pledged Equity. If Pledgor shall receive, by virtue of
its being or having been an owner of any Pledged Equity, any (i) shares of
capital stock, membership interests and/or partnership interests (including any
certificate representing any shares of capital stock, membership interests
and/or partnership interests or distribution in connection with any increase or
reduction of capital, reorganization, reclassification, merger, consolidation,
sale of assets, or spinoff or split-off), promissory note or other instrument or
writing; (ii) option or right, whether as an addition to, substitution for, or
in exchange for, any Pledged Equity or otherwise; (iii) dividends payable in
cash (except such dividends permitted to be retained by Pledgor pursuant to
Section 4.7 hereof) or in securities or other property; or (iv) dividends or
other distributions in connection with a partial or total liquidation or
dissolution or in connection with a reduction of capital, capital surplus or
paid-in surplus, Pledgor shall receive the same in trust for the benefit of
Pledgee, shall segregate it from Pledgor's other property, and shall promptly
deliver it to Pledgee in the exact form received, with any necessary endorsement
or appropriate stock powers duly executed in blank, to be held by Pledgee as
Collateral.

         (e) Status of Pledged Equity. The certificates (or other instruments
and writings) evidencing the Pledged Equity shall at all times be valid and
genuine and shall not be altered. The Pledged Equity at all times shall be duly
authorized, validly issued, fully paid, and non- assessable, shall not be issued
in violation of the pre-emptive rights of any Person or of any agreement by
which Pledgor or Borrower bound, and, except for the partnership agreement,
regulations or

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bylaws of Borrower, shall not be subject to any restrictions or conditions with
respect to the transfer, voting or capital of any Pledged Equity.

         Section 3.3 Negative Covenants. Unless Pledgee shall otherwise consent
in writing, Pledgor will at all times comply with the covenants contained in
this Section 3.3 from the date hereof and so long as any part of the Obligations
or the Commitments is outstanding.

         (a) Transfer or Encumbrance. Pledgor will not sell, assign (by
operation of law or otherwise), transfer, exchange, lease or otherwise dispose
of any of the Collateral, nor will Pledgor grant a Lien upon or execute, file or
record any financing statement or other registration with respect to the
Collateral, nor will Pledgor allow any such Lien, financing statement, or other
registration to exist or deliver actual or constructive possession of the
Collateral to any other Person other than Liens in favor of Pledgee.

         (b) Financing Statement Filings. Pledgor recognizes that financing
statements pertaining to the Collateral have been or may be filed where Pledgor
maintains any Collateral, has its records concerning any Collateral or has its
chief executive office or chief place of business. Without limitation of any
other covenant herein, Pledgor will not cause or permit any change to be made in
its name, identity or corporate, partnership or limited liability company
structure, or any change to be made to a jurisdiction other than as represented
in Section 3.1 hereof in (i) the location of any records concerning any
Collateral, or (ii) in the location of its chief executive office or chief place
of business, unless Pledgor shall have notified Pledgee of such change at least
thirty (30) days prior to the effective date of such change, and shall have
first taken all action required by Pledgee for the purpose of further perfecting
or protecting the security interest in favor of Pledgee in the Collateral. In
any notice furnished pursuant to this subsection, Pledgor will expressly state
that the notice is required by this Agreement and contains facts that may
require additional filings of financing statements or other notices for the
purposes of continuing perfection of Pledgee's security interest in the
Collateral.

         (c) Impairment of Security Interest. Pledgor will not take or fail to
take any action which would in any manner impair the enforceability of Pledgee's
security interest in any Collateral.

         (d) Restrictions on Pledged Equity. Except for the partnership
agreement, regulations or bylaws of Borrower, Pledgor will not enter into any
agreement creating, or otherwise permit to exist, any restriction or condition
upon the transfer, voting or control of any Pledged Equity.

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                                   ARTICLE IV.

                       Remedies, Powers and Authorizations

         Section 4.1 Provisions Concerning the Collateral.

         (a) Additional Financing Statement Filings. Pledgor hereby authorizes
Pledgee to file, without the signature of Pledgor where permitted by law, one
(1) or more financing or continuation statements, and amendments thereto,
relating to the Collateral. Pledgor further agrees that a carbon, photographic
or other reproduction of this Agreement or any financing statement describing
any Collateral is sufficient as a financing statement and may be filed in any
jurisdiction Pledgee may deem appropriate.

         (b) Power of Attorney. Pledgor hereby irrevocably appoints Pledgee as
Pledgor's attorney-in-fact and proxy, with full authority in the place and stead
of Pledgor and in the name of Pledgor or otherwise, from time to time in
Pledgee's discretion, to take any action (except for the exercise of any voting
rights pertaining to the Pledged Equity or any part thereof) and to execute any
instrument, certificate or notice which Pledgee may deem necessary or advisable
to accomplish the purposes of this Agreement including, without limitation: (i)
to request or instruct Pledgor (and each registrar, transfer agent, or similar
Person acting on behalf of Pledgor) to register the pledge or transfer of the
Collateral to Pledgee; (ii) to otherwise give notification to Pledgor,
registrar, transfer agent, financial intermediary, or other Person of Pledgee's
security interests hereunder; (iii) to ask, demand, collect, sue for, recover,
compound, receive and give acquittance and receipts for moneys due and to become
due under or in respect of any of the Collateral; (iv) to receive, indorse and
collect any drafts or other instruments, documents and chattel paper; and (v) to
file any claims or take any action or institute any proceedings which Pledgee
may deem necessary or desirable for the collection of any of the Collateral or
otherwise to enforce the rights of Pledgee with respect to any of the
Collateral.

         (c) Performance by Pledgee. If Pledgor fails to perform any agreement
or obligation contained herein, Pledgee may itself perform, or cause performance
of, such agreement or obligation, and the expenses of Pledgee incurred in
connection therewith shall be payable by Pledgor under Section 4.4.

         (d) Collection Rights. Pledgee shall have the right at any time, upon
the occurrence and during the continuance of an Event of Default, to notify any
or all obligors (including without limitation Pledgor) under any accounts or
general intangibles included among the Collateral of the assignment thereof to
Pledgee and to direct such obligors to make payment of all amounts due or to
become due to Pledgor thereunder directly to Pledgee and, upon such notification
and at the expense of Pledgor and to the extent permitted by law, to enforce
collection thereof and to adjust, settle or compromise the amount or payment
thereof, in the same manner and to the same extent as Pledgor could have done.
After Pledgor receives notice that Pledgee has given any notice referred to
above in this subsection, (i) all amounts and proceeds (including instruments
and writings) received by Pledgor in respect of such accounts or general
intangibles shall be received in trust for the benefit of Pledgee hereunder,
shall be segregated from other funds of Pledgor and shall be forthwith paid over
to Pledgee in the same form as so received (with any necessary indorsement) to
be held as cash collateral and (a) released to Pledgor upon the remedy of all
Defaults or Events of Default, or (b) if any Event of Default shall have
occurred and be continuing, applied as specified in Section 4.3, and (ii)
Pledgor will not adjust, settle or

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compromise the amount or payment of any such account or general intangible or
release wholly or partly any account debtor or obligor thereof (including
without limitation Pledgor) or allow any credit or discount thereon.

         Section 4.2 Event of Default Remedies. If an Event of Default shall
have occurred and be continuing, Pledgee may from time to time in its
discretion, without limitation and without notice except as expressly provided
below:

         (a) exercise in respect of the Collateral, in addition to other rights
and remedies provided for herein, under the other Obligation Documents or
otherwise available to it, all the rights and remedies of a secured party on
default under the Code (whether or not the Code applies to the affected
Collateral);

         (b) require Pledgor to, and Pledgor hereby agrees that it will at its
expense and upon request of Pledgee forthwith, assemble all or part of the
Collateral as directed by Pledgee and make it available to Pledgee at a place to
be designated by Pledgee which is reasonably convenient to both parties;

         (c) reduce its claim to judgment against Pledgor or foreclose or
otherwise enforce, in whole or in part, the security interest created hereby by
any available judicial procedure;

         (d) dispose of, at its office, on the premises of Pledgor or elsewhere,
all or any part of the Collateral, as a unit or in parcels, by public or private
proceedings, and by way of one or more contracts (it being agreed that the sale
of any part of the Collateral shall not exhaust Pledgee's power of sale, but
sales may be made from time to time, and at any time, until all of the
Collateral has been sold or until the Obligations have been paid and performed
in full), and at any such sale it shall not be necessary to exhibit any of the
Collateral;

         (e) buy (or allow any Bank to buy) the Collateral, or any part thereof,
at any public sale;

         (f) buy (or allow any Bank to buy) the Collateral, or any part thereof,
at any private sale if the Collateral is of a type customarily sold in a
recognized market or is of a type which is the subject of widely distributed
standard price quotations;

         (g) apply by appropriate judicial proceedings for appointment of a
receiver for the Collateral, or any part thereof, and Pledgor hereby consents to
any such appointment; and

         (h) at its discretion, retain the Collateral in satisfaction of the
Obligations whenever the circumstances are such that Pledgee is entitled to do
so under the Code or otherwise (provided that Pledgee shall in no circumstances
be deemed to have retained the Collateral in satisfaction of the Obligations in
the absence of an express notice by Pledgee to Pledgor that Pledgee has either
done so or intends to do so).

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Pledgor agrees that, to the extent notice of sale shall be required by law, at
least five (5) days' notice to Pledgor of the time and place of any public sale
or the time after which any private sale is to be made shall constitute
reasonable notification. Pledgee shall not be obligated to make any sale of
Collateral regardless of notice of sale having been given. Pledgee may adjourn
any public or private sale from time to time by announcement at the time and
place fixed therefor, and such sale may, without further notice, be made at the
time and place to which it was so adjourned.

         Section 4.3 Application of Proceeds. If any Event of Default shall have
occurred and be continuing, Pledgee may in its discretion apply any cash held by
Pledgee as Collateral, and any cash proceeds received by Pledgee in respect of
any sale of, collection from, or other realization upon all or any part of the
Collateral, to any or all of the following in such order as Pledgee may elect:

         (a) to the repayment of the reasonable costs and expenses, including
reasonable attorneys' fees and legal expenses, incurred by Pledgee in connection
with (i) the administration of this Agreement, (ii) the custody, preservation,
use or operation of, or the sale of, collection from, or other realization upon,
any Collateral, (iii) the exercise or enforcement of any of the rights of
Pledgee hereunder, or (iv) the failure of Pledgor to perform or observe any of
the provisions hereof;

         (b) to the payment or other satisfaction of any Liens, encumbrances, or
adverse claims upon or against any of the Collateral;

         (c) to the reimbursement of Pledgee for the amount of any obligations
of Pledgor or any Other Liable Party paid or discharged by Pledgee pursuant to
the provisions of this Agreement or the other Obligation Documents, and of any
expenses of Pledgee payable by Pledgor hereunder or under the other Obligation
Documents;

         (d) to the satisfaction of any other Obligations or any other
indebtedness of Pledgor and/or Borrower to Banks or Pledgee;

         (e) by holding the same as Collateral;

         (f) to the payment of any other amounts required by applicable law
(including, without limitation, Section 9.504(a)(3) of the Code or any successor
or similar, applicable statutory provision); and

         (g) by delivery to Pledgor or to whomsoever shall be lawfully entitled
to receive the same or as a court of competent jurisdiction shall direct.

         Section 4.4 Release and Expenses. In addition to, and not in
qualification of, any similar obligations under other Obligation Documents:

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         (a) Pledgor agrees to release and forever discharge Pledgee and each
Bank from and against any and all claims, losses and liabilities growing out of
or resulting from this Agreement (including, without limitation, enforcement of
this Agreement). The foregoing release and discharge shall apply whether or not
such claims, losses and liabilities are in any way or to any extent owed, in
whole or in part, under any claim or theory of strict liability or are, to any
extent caused, in whole or in part, by any negligent act or omission of any kind
by Pledgee or any Bank.

         (b) Pledgor will upon demand pay to Pledgee the amount of any and all
costs and expenses, including the fees and disbursements of Pledgee's counsel
and of any experts and agents, which Pledgee may incur in connection with (i)
the transactions which give rise to this Agreement; (ii) the preparation of this
Agreement and the perfection and preservation of the security interest created
under this Agreement; (iii) the administration of this Agreement; (iv) the
custody, preservation, use or operation of, or the sale of, collection from, or
other realization upon, any Collateral; (v) the exercise or enforcement of any
of the rights of Pledgee hereunder; or (vi) the failure by Pledgor to perform or
observe any of the provisions hereof, except expenses resulting from Pledgee's
gross negligence or willful misconduct.

         Section 4.5 Non-Judicial Remedies. In granting to Pledgee the power to
enforce its rights hereunder without prior judicial process or judicial hearing,
Pledgor expressly waives, renounces and knowingly relinquishes any legal right
which might otherwise require Pledgee to enforce its rights by judicial process.
In so providing for non-judicial remedies, Pledgor recognizes and concedes that
such remedies are consistent with the usage of trade, are responsive to
commercial necessity, and are the result of a bargain at arm's length. Nothing
herein is intended to prevent Pledgee or Pledgor from resorting to judicial
process at either party's option.

         Section 4.6 Other Recourse. Pledgor waives any right to require Pledgee
or Banks to proceed against any other Person, exhaust any Collateral or other
security for the Obligations, or to have any Other Liable Party joined with
Pledgor in any suit arising out of the Obligations or this Agreement, or pursue
any other remedy in Pledgee's power. Pledgor further waives any and all notice
of acceptance of this Agreement and of the creation, modification,
rearrangement, renewal or extension for any period of any of the Obligations of
any Other Liable Party from time to time. Pledgor further waives any defense
arising by reason of any disability or other defense of any Other Liable Party
or by reason of the cessation from any cause whatsoever of the liability of any
Other Liable Party. Until all of the Obligations shall have been paid in full,
Pledgor shall have no right to subrogation and Pledgor waives the right to
enforce any remedy which Pledgee or any Bank has or may hereafter have against
any Other Liable Party, and waives any benefit of and any right to participate
in any other security whatsoever now or hereafter held by Pledgee. Pledgor
authorizes Pledgee and each Bank, without notice or demand and without any
reservation of rights against Pledgor and without affecting Pledgor's or
Borrower's liability hereunder or on the Obligations, from time to time to (a)
take or hold any other property of any type from any other Person as security
for the Obligations, and exchange, enforce, waive and release any or all of such
other property,(b) apply the Collateral or such other property and direct the
order or manner of sale thereof as Pledgee may in its discretion determine, (c)
renew, extend for any period,

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accelerate, modify, compromise, settle or release any of the obligations of any
Other Liable Party in respect to any or all of the Obligations or other security
for the Obligations, (d) waive, enforce, modify, amend or supplement any of the
provisions of any Obligation Document with any Person other than Pledgor, and
(e) release or substitute any Other Liable Party.

         Section 4.7 Voting Rights, Dividends Etc. in Respect of Pledged Equity.

         (a) So long as no Event of Default shall have occurred and be
continuing Pledgor may receive and retain any and all dividends or interest paid
in respect of the Pledged Equity; provided, however, that any and all

                  (i) dividends and interest paid or payable other than in cash
         in respect of, and instruments and other property received, receivable
         or otherwise distributed in respect of or in exchange for, any Pledged
         Equity,

                  (ii) dividends and other distributions paid or payable in cash
         in respect of any Pledged Equity in connection with a partial or total
         liquidation or dissolution or in connection with a reduction of
         capital, capital surplus or paid-in surplus, and

                  (iii) cash paid, payable or otherwise distributed in
         redemption of, or in exchange for, any Pledged Equity,

shall be, and shall forthwith be delivered to Pledgee to hold as, Pledged Equity
and shall, if received by Pledgor, be received in trust for the benefit of
Pledgee, be segregated from the other property or funds of Pledgor, and be
forthwith delivered to Pledgee in the exact form received with any necessary
indorsement or appropriate stock powers duly executed in blank, to be held by
Pledgee as Collateral.

         (b) Upon the occurrence and during the continuance of an Event of
Default:

                  (i) all rights of Pledgor to receive and retain the dividends
         and interest payments which Pledgor would otherwise be authorized to
         receive and retain pursuant to subsection (a) of this Section shall
         automatically cease, and all such rights shall thereupon become vested
         in Pledgee which shall thereupon have the right to receive and hold as
         Pledged Equity such dividends and interest payments;

                  (ii) without limiting the generality of the foregoing, Pledgee
         may at its option exercise any and all rights of conversion, exchange,
         subscription or any other rights, privileges or options pertaining to
         any of the Pledged Equity (except voting rights) as if it were the
         absolute owner thereof, including, without limitation, the right to
         exchange, in its discretion, any and all of the Pledged Equity upon the
         merger, consolidation, reorganization, recapitalization or other
         adjustment of Pledgor or Borrower, or upon the exercise by Pledgor or
         Borrower of any right, privilege or option pertaining to any

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         Pledged Equity, and, in connection therewith, to deposit and deliver
         any and all of the Pledged Equity with any committee, depository,
         transfer agent, registrar or other designated agent upon such terms and
         conditions as it may determine; and

                  (iii) all dividends and interest payments which are received
         by Pledgor contrary to the provisions of subsection (b) (i) of this
         Section shall be received in trust for the benefit of Pledgee, shall be
         segregated from other funds of Pledgor, and shall be forthwith paid
         over to Pledgee as Pledged Equity in the exact form received, to be
         held by Pledgee as Collateral.

Anything herein to the contrary notwithstanding, Pledgee may not exercise any
voting rights pertaining to the Pledged Equity and Pledgor may at all times
exercise any and all voting rights pertaining to the Pledged Equity or any part
thereof for any purpose not inconsistent with the terms of this Agreement or any
other Obligation Document; provided, however, upon the occurrence and during the
continuance of a Default or an Event of Default, Pledgor will not exercise or
refrain from exercising any such right, as the case may be, if Pledgee gives
notice that, in Pledgee's judgment, such action would result in a Material
Adverse Change with respect to the value of the Pledged Equity or the benefits
to Pledgee of its security interest hereunder.

         Section 4.8 Private Sale of Pledged Equity. Pledgor recognizes that
Pledgee may deem it impracticable to effect a public sale of all or any part of
the Pledged Equity and that Pledgee may, therefore, determine to make one or
more private sales of any such securities to a restricted group of purchasers
who will be obligated to agree, among other things, to acquire such securities
for their own account, for investment and not with a view to the distribution or
resale thereof. Pledgor acknowledges that any such private sale may be at prices
and on terms less favorable to the seller than the prices and other terms which
might have been obtained at a public sale and, notwithstanding the foregoing,
agrees that such private sales shall be deemed to have been made in a
commercially reasonable manner and that Pledgee shall have no obligation to
delay the sale of any such securities for the period of time necessary to permit
Pledgor to register such securities (with no obligation of Pledgor to accomplish
such registration) for public sale under the Securities Act of 1933, as amended.
Pledgor further acknowledges and agrees that any offer to sell such securities
which has been (a) publicly advertised on a bona fide basis in a newspaper or
other publication of general circulation in the financial community of Dallas,
Texas (to the extent that such an offer may be so advertised without prior
registration under the Securities Act), or (b) made privately in the manner
described above to not less than fifteen (15) bona fide offerees shall be deemed
to involve a "public sale" for the purposes of Section 9.504(c) of the Code (or
any successor or similar, applicable statutory provision) as then in effect in
the State of Texas, notwithstanding that such sale may not constitute a "public
offering" under the Securities Act of 1933, as amended, and that Pledgee may, in
such event, bid for the purchase of such securities.

                                      K-13

<PAGE>   144

                                   ARTICLE V.

                                  Miscellaneous

         Section 5.1 Notices. Any notice or communication required or permitted
hereunder shall be given in writing, sent by personal delivery, by telecopy, by
delivery service with proof of delivery, or by registered or certified United
States mail, postage prepaid, addressed to the appropriate party as follows:

To Pledgor:                    Taurus Acquisition, Inc.
                               c/o EXCO Resources, Inc.
                               5735 Pineland Drive, Suite 233
                               Dallas, Texas 75231
                               Fax No.: (214) 368-2087

To Pledgee:                    Bank of America, N.A., as Administrative Agent
                               901 Main Street, 64th Floor
                               Dallas, Texas 75202
                               Fax No. (214) 209-1285

or to such other address or to the attention of such other individual as
hereafter shall be designated in writing by the applicable party sent in
accordance herewith. Any such notice or communication shall be deemed to have
been given (a) in the case of personal delivery or delivery service, as of the
date of first attempted delivery at the address or in the manner provided
herein, (b) in the case of telecopy, upon receipt, or (c) in the case of
registered or certified United States mail, three (3) days after deposit in the
mail.

         Section 5.2 Amendments. No amendment of any provision of this Agreement
shall be effective unless it is in writing and signed by Pledgor, Pledgee and
Banks, and no waiver of any provision of this Agreement, and no consent to any
departure by Pledgor therefrom, shall be effective unless it is in writing and
signed by Pledgee and Banks, and then such waiver or consent shall be effective
only in the specific instance and for the specific purpose for which given and
to the extent specified in such writing.

         Section 5.3 Preservation of Rights. No failure on the part of Pledgee
or any Bank to exercise, and no delay in exercising, any right hereunder or
under any other Obligation Document shall operate as a waiver thereof; nor shall
any single or partial exercise of any such right preclude any other or further
exercise thereof or the exercise of any other right. Neither the execution nor
the delivery of this Agreement shall in any manner impair or affect any other
security for the Obligations. The rights and remedies of Pledgee and Banks
provided herein and in the other Obligation Documents are cumulative of and are
in addition to, and not exclusive of, any rights or remedies provided by law.
The rights of Pledgee and Banks under any Obligation Document against any party
thereto are not conditional or contingent on any attempt by Pledgee or Banks to

                                      K-14

<PAGE>   145

exercise any of its rights under any other Obligation Document against such
party or against any other Person.

         Section 5.4 Unenforceability. Any provision of this Agreement which is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or invalidity without
invalidating the remaining portions hereof or thereof or affecting the validity
or enforceability of such provision in any other jurisdiction.

         Section 5.5 Survival of Agreements. All representations and warranties
of Pledgor herein, and all covenants and agreements herein shall survive the
execution and delivery of this Agreement, the execution and delivery of any
other Obligation Documents and the creation of the Obligations.

         Section 5.6 Other Liable Party. Neither this Agreement nor the exercise
by Pledgee or any Bank or the failure of Pledgee or any Bank to exercise any
right, power or remedy conferred herein or by law shall be construed as
relieving any Other Liable Party from liability on the Obligations or any
deficiency thereon. This Agreement shall continue irrespective of the fact that
the liability of any Other Liable Party may have ceased or irrespective of the
validity or enforceability of any other Obligation Document to which Pledgor or
any Other Liable Party may be a party, and notwithstanding the reorganization,
death, incapacity or bankruptcy of any Other Liable Party, and notwithstanding
the reorganization or bankruptcy or other event or proceeding affecting any
Other Liable Party.

         Section 5.7 Binding Effect and Assignment. This Agreement creates a
continuing security interest in the Collateral and (a) shall be binding on
Pledgor and its successors and permitted assigns, and (b) shall inure, together
with all rights and remedies of Pledgee hereunder, to the benefit of Pledgee and
Banks and their respective successors, transferees and assigns. Without limiting
the generality of the foregoing, Pledgee and Banks may pledge, assign or
otherwise transfer any or all of their respective rights under any or all of the
Obligation Documents to any other Person, and such other Person shall thereupon
become vested with all of the benefits in respect thereof granted herein or
otherwise. None of the rights or duties of Pledgor hereunder may be assigned or
otherwise transferred without the prior written consent of Pledgee and Banks.

         Section 5.8 Termination. It is contemplated by the parties hereto that
there may be times when no Obligations are outstanding, but notwithstanding such
occurrences, this Agreement shall remain valid and shall be in full force and
effect as to subsequent outstanding Obligations. Upon the satisfaction in full
of the Obligations, upon the termination or expiration of the Credit Agreement
and any other Commitment of Banks to extend credit to Borrower, and upon written
request for the termination hereof delivered by Pledgor to Pledgee and Banks,
this Agreement and the security interest created hereby shall terminate and all
rights to the Collateral shall revert to Pledgor. Pledgee will, upon Pledgor's
request and at Pledgor's expense, (a) return to Pledgor such of the Collateral
as shall not have been sold or otherwise disposed of or applied pursuant to

                                      K-15

<PAGE>   146

the terms hereof, and (b) execute and deliver to Pledgor such documents as
Pledgor shall reasonably request to evidence such termination.

         Section 5.9 Governing Law. THIS AGREEMENT SHALL BE CONSTRUED IN
ACCORDANCE WITH AND GOVERNED BY THE LAWS OF THE STATE OF TEXAS AND THE LAWS OF
THE UNITED STATES OF AMERICA.

         Section 5.10 Counterparts. This Agreement may be separately executed in
any number of counterparts, all of which when so executed shall be deemed to
constitute one and the same Agreement.

         Section 5.11 Loan Paper. This Agreement is a "Loan Paper", as defined
in the Credit Agreement, and, except as expressly provided herein to the
contrary, this Agreement is subject to all provisions of the Credit Agreement
governing such Loan Paper.

                                      K-16

<PAGE>   147

         IN WITNESS WHEREOF, Pledgor has caused this Agreement to be executed
and delivered by its officer thereunto duly authorized, as of the date first
above written.

                                 TAURUS ACQUISITION, INC.,
                                 a Texas corporation

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

                                      K-17

<PAGE>   148

                                   SCHEDULE 1

                             FINANCIAL INSTITUTIONS

<TABLE>
<CAPTION>
===================================================================================================================================
                      Bank                                  Commitment Amount                        Commitment Percentage
-----------------------------------------------------------------------------------------------------------------------------------
<S>                                                          <C>                                     <C>
Bank of America, N.A.                                          $25,000,000                                    100%
===================================================================================================================================
</TABLE>

<TABLE>
<CAPTION>
===================================================================================================================================
     Domestic Lending                 Eurodollar Lending
          Office                            Office                      Address for Notice          Administrative Agent - Address
-----------------------------------------------------------------------------------------------------------------------------------
<S>                                <C>                              <C>                               <C>
901 Main Street, 64th              901 Main Street, 64th            901 Main Street, 64th             901 Main Street, 64th Floor
Floor                              Floor                            Floor                             Dallas, Texas 75202
Dallas, Texas 75202                Dallas, Texas 75202              Dallas, Texas 75202               Fax No. (214) 508-1285
Fax No. (214) 508-1285             Fax No. (214) 508-1285           Fax No. (214) 508-1285
===================================================================================================================================
</TABLE>

                                   Schedule 1

<PAGE>   149

                                   SCHEDULE 2

                             LITIGATION AND CLAIMS

o  Case #93-11958, 261st Court, Travis County, Texas styled Ladd Petroleum
   Corporation v. State of Texas General Land Office affecting State leases
   included within the Gomez South Unit #1 (Gomez #1-D and #1-A Wells), the FSOC
   - Dixel Gas Unit #2 (Dixel #2 Well), and FSOC-Leon Gas Unit (Leon #1 Well),
   Pecos County, Texas.

OTHER THAN THE ABOVE, NONE.

                                   Schedule 2

<PAGE>   150

                                   SCHEDULE 3

                   ORGANIZATION STRUCTURE; NATURE OF BUSINESS

1.       Borrower is a Texas limited partnership.

3.       Borrower's Partners:

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
                                                                           CAPITAL ACCOUNT
                                                                          AFTER REEVALUATION
                                                                           OF THE NEBRASKA
                                                    INITIAL                  PROPERTIES,
                  PARTNER                           CAPITAL               ADMISSION OF EXCO           PARTNERSHIP
            (AND CLASSIFICATION)                  CONTRIBUTION             RESOURCES, INC.             INTEREST
--------------------------------------------------------------------------------------------------------------------
<S>                                               <C>                     <C>                         <C>
J.M. Hill (L.P.)                                     $50,000.00              $1,731,372.00               24.5%
Charles Humphrey (L.P.)                              $47,960.00               1,660,607.00               23.5%
EXCO Resources, Inc. (G.P.)                          $68,628.00                 $68,628.00                  1%
Taurus Acquisition, Inc. (L.P.)                   $3,431,372.00              $3,431,372.00                 50%
Humphrey Oil Corporation (L.P.)                       $2,040.00                 $70,766.00                  1%
--------------------------------------------------------------------------------------------------------------------
</TABLE>

4.       EXCO is the sole owner of all legal and beneficial interest in and to
         100% of the issued outstanding capital stock of Taurus of every class.

5.       There are no outstanding warrants, options, subscription rights,
         convertible securities or other rights to purchase interests in
         Borrower or Taurus.

                                   Schedule 3

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