Document:

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                                                                    EXHIBIT 10.4

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                          PURCHASE AND SALE AGREEMENT

                             Dated: April 30, 2000

                                By and Between

                    MOUNTAINEER LIMITED PARTNERSHIP, SELLER

                                      and

                               AROC INC., BUYER

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                               TABLE OF CONTENTS
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ARTICLE I
     Definitions and References..............................................  1
          Section 1.1.   Certain Defined Terms...............................  1
          Section 1.2.   Certain Additional Defined Terms....................  8
          Section 1.3.   References, Titles and Construction.................  9

ARTICLE II
     Property to be Sold and Purchased....................................... 10

ARTICLE III
     Purchase Price.......................................................... 11

ARTICLE IV
     Representations and Warranties of Seller................................ 12
          Section 4.1.   Organization and Existence.......................... 12
          Section 4.2.   Authority Relative to This Agreement................ 12
          Section 4.3.   Valid and Binding Agreement......................... 12
          Section 4.4.   Non-Contravention................................... 12
          Section 4.5.   Approvals........................................... 13
          Section 4.6.   Pending Litigation.................................. 13
          Section 4.7.   Basic Documents..................................... 13
          Section 4.8.   Commitments, Abandonments or Proposals.............. 14
          Section 4.9.   Production Sales Contracts.......................... 14
          Section 4.10.  Plugging and Abandonment............................ 14
          Section 4.11.  Licenses and Permits................................ 14
          Section 4.12.  Area of Mutual Interest and Other Agreements;
                         Tax Partnerships.................................... 15
          Section 4.13.  Payment of Expenses................................. 15
          Section 4.14.  Compliance with Laws................................ 15
          Section 4.15.  Operated Properties................................. 15
          Section 4.16.  Physical Condition of Facilities.................... 16
          Section 4.17.  Environmental Matters............................... 16
          Section 4.18.  Production Data..................................... 16
          Section 4.19.  Ordinary Course Operations.......................... 16
          Section 4.20.  Sale of Production.................................. 17
          Section 4.21.  [Intentionally Omitted]............................. 17
          Section 4.22.  Brokerage Fees...................................... 17
          Section 4.24.  Bankruptcy.......................................... 17
          Section 4.25.  Full Disclosure..................................... 17
          Section 4.26.  Disclaimer of Warranties............................ 17
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ARTICLE V
     Representations and Warranties of Buyer................................. 18
          Section 5.1.   Organization and Existence.......................... 18
          Section 5.2.   Qualification....................................... 18
          Section 5.3.   Charter and Bylaws.................................. 18
          Section 5.4.   Capitalization of Buyer............................. 18
          Section 5.5.   Authority Relative to This Agreement................ 19
          Section 5.6.   No Conflict......................................... 19
          Section 5.7.   Consents and Approvals, Licenses, Etc............... 19
          Section 5.8.   Subsidiaries........................................ 20
          Section 5.9.   Preferred Shares; Conversion Shares................. 20
          Section 5.10.  Financial Statements................................ 21
          Section 5.11.  Securities Filings.................................. 21
          Section 5.12.  Absence of Undisclosed Liabilities.................. 22
          Section 5.13.  Absence of Certain Changes.......................... 22
          Section 5.14.  Tax Matters......................................... 22
          Section 5.15.  Environmental and Other Laws........................ 24
          Section 5.16.  Legal Proceedings................................... 24
          Section 5.17.  Title to Properties; Permits; Licenses; Condition of
                           Assets............................................ 24
          Section 5.18.  ERISA............................................... 25
          Section 5.19.  Agreements.......................................... 27
          Section 5.20.  Labor Disputes and Acts of God...................... 29
          Section 5.21.  Insurance........................................... 29
          Section 5.22.  Offering of Securities.............................. 29
          Section 5.23.  Government Regulation............................... 29
          Section 5.24.  Brokerage Fees...................................... 29
          Section 5.25.  Bankruptcy.......................................... 29
          Section 5.26.  Nature of Company Assets............................ 29
          Section 5.27.  Full Disclosure..................................... 29

ARTICLE VI
     Certain Covenants of Seller and Buyer Pending Closing................... 30
          Section 6.1.   Pre-Closing Covenants of Seller..................... 30
          Section 6.2.   Pre-Closing Covenants of Buyer...................... 32
          Section 6.3.   Pre-Closing Covenants of Seller and Buyer........... 34

ARTICLE VII
     Due Diligence Examination With Respect to the Properties................ 34
          Section 7.1.   Inspection and Assertion of Defects................. 34
          Section 7.2.   Certain Price Adjustments........................... 35
          Section 7.3.   Waiver.............................................. 36
          Section 7.4.   Casualty Loss....................................... 36
          Section 7.5.   Disputes............................................ 36

ARTICLE VIII
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     Conditions Precedent to the Obligations of the Parties.................. 38
          Section 8.1.   Conditions Precedent to the Obligations of Buyer.... 38
          Section 8.2.   Conditions Precedent to the Obligations of Seller... 39

ARTICLE IX
     Closing of Transaction.................................................. 40
          Section 9.1.   The Closing......................................... 40
          Section 9.2.   Seller's Closing Obligations........................ 40
          Section 9.3.   Buyer's Closing Obligations......................... 40
          Section 9.4.   Delivery of Files................................... 41

ARTICLE X
     Pre-Closing Termination................................................. 41
          Section 10.1.  Termination......................................... 41
          Section 10.2.  Effect of Termination............................... 41

ARTICLE XI
     Certain Accounting Adjustments in Respect of the Properties............. 42
          Section 11.1.  Adjustments......................................... 42
          Section 11.2.  Closing and Post-Closing Accounting Settlements..... 42

ARTICLE XII
     Assumption and Indemnification.......................................... 43

ARTICLE XIII
     Affirmative Post Closing Covenants of Buyer............................. 43
          Section 13.1.  Inspection Rights................................... 43
          Section 13.2.  Books, Financial Statements and Reports............. 44
          Section 13.3.  Notice of Material Events and Change of Address..... 45
          Section 13.4.  Maintenance of Properties........................... 46
          Section 13.5.  Maintenance of Existence and Qualifications......... 46
          Section 13.6.  Payment of Trade Liabilities, Taxes, etc............ 46
          Section 13.7.  Insurance........................................... 46
          Section 13.8.  Compliance with Agreements and Law.................. 46
          Section 13.9.  Charter Amendment Approval.......................... 46

ARTICLE XIV
     Post Closing Negative Covenants of Buyer................................ 47
          Section 14.1.  Indebtedness........................................ 47
          Section 14.2.  Limitation on Liens................................. 47
          Section 14.3.  Limitation on Mergers............................... 47
          Section 14.4.  Limitation on Sales of Property..................... 48
          Section 14.5.  Limitation on Investments and New Businesses........ 48
          Section 14.6.  Transactions with Affiliates........................ 48
          Section 14.7.  Restricted Payments................................. 48
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ARTICLE XV
     Events of Default and Remedies.......................................... 49
          Section 15.1.  Events of Default................................... 49
          Section 15.2.  Annulment of Defaults............................... 51
          Section 15.3.  Expiration.......................................... 51

ARTICLE XVI
     Notices................................................................. 51

ARTICLE XVII
     Miscellaneous Matters................................................... 52
          Section 17.1.  Survival of Provisions.............................. 52
          Section 17.2.  Public Announcements................................ 53
          Section 17.3.  Fees and Expenses................................... 53
          Section 17.4.  Costs of Enforcement................................ 53
          Section 17.5.  Indemnification..................................... 53
          Section 17.6.  Waiver and Amendment................................ 55
          Section 17.7.  Entire Agreement.................................... 56
          Section 17.8.  Binding Effect; Assignment; No Third Party Benefit.. 56
          Section 17.9.  Severability........................................ 56
          Section 17.10. Governing Law....................................... 56
          Section 17.11. Remedies Not Exclusive.............................. 56
          Section 17.12. Further Assurances.................................. 57
          Section 17.13. Counterparts........................................ 57
          Section 17.14. Injunctive Relief................................... 57
          Section 17.15. Consent to Jurisdiction............................. 57
          Section 17.17. Payments............................................ 57
          Section 17.18. Right to Purchase New Equity Securities............. 57
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                          PURCHASE AND SALE AGREEMENT

     THIS PURCHASE AND SALE AGREEMENT dated April 30, 2000, is made by and
between  MOUNTAINEER LIMITED PARTNERSHIP, a Texas limited partnership
("Seller"), and AROC INC., a Delaware corporation ("Buyer");

                              W I T N E S S E T H:
                              --------------------

     WHEREAS, Seller desires to sell, assign and convey to Buyer, and Buyer
desires to purchase and accept certain oil and gas properties and related
assets; and

     WHEREAS, Seller and Buyer deem it in their mutual best interests to execute
and deliver this Agreement;

     NOW, THEREFORE, in consideration of the foregoing Recitals and the mutual
covenants and agreements contained herein, Seller and Buyer do hereby agree as
follows:

                                   ARTICLE I

                           Definitions and References
                          ---------------------------

     Section 1.1.   Certain Defined Terms.  When used in this Agreement, the
                    ---------------------
following terms shall have the respective meanings assigned to them in this
Section 1.1 or in the section, subsections or other subdivisions referred to
below:

     "Affiliate" means, with respect to any Person, any other Person that,
directly or indirectly, through one or more intermediaries, controls, is
controlled by or is under common control with, such Person.  For the purposes of
this definition, "control" when used with respect to any Person means 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, by contract, or otherwise; and the terms
"controlling" and "controlled" have meanings correlative to the foregoing.

     "Agreement" means this Agreement, as hereafter changed, amended or modified
in accordance with the terms hereof.

     "Alliance Group" means Alliance Resources Group, Inc., a Delaware
corporation.

     "Alliance PLC" means Alliance Resources PLC, a public limited company
incorporated in England and Wales.

     "Alliance USA" means Alliance Resources (USA), Inc., a Delaware
     corporation.
<PAGE>

     "Ancillary Documents" means each agreement, certificate, document,
commitment and writing (other than this Agreement) executed or to be executed by
Buyer or Seller in connection with the transactions contemplated herein or
therein, including the Assignment.

     "Applicable Law" means any statute, law, rule or regulation, or any
judgment, order, writ, injunction or decree of, any Governmental Entity to which
a specified Person or property is subject.

     "AROC (Texas)" means AROC (Texas), Inc., a Texas corporation.

     "Certificate of Designation" means the document attached hereto as Exhibit
                                                                        -------
3.1.
---

     "Change of Control"  means the occurrence of any of the following events
after giving effect to the transactions contemplated by this Agreement, the
Other Acquisition Agreements and the Preferred Stock Purchase Agreement: (a) any
Person or two or more Persons, other than Buyer or any affiliate of Buyer,
acting as a group shall acquire beneficial ownership (within the meaning of Rule
13d-3 of the Securities and Exchange Commission under the Exchange Act, and
including holding proxies to vote for the election of directors other than
proxies held by Buyer's management or their designees to be voted in favor of
persons nominated by Buyer's Board of Directors) of 33% or more of the
outstanding voting securities of  Buyer, measured by voting power (including
both ordinary shares and any preferred stock or other equity securities
entitling the holders thereof to vote with the holders of common stock in
elections for directors of Buyer.), (b) Buyer shall fail beneficially to own,
directly or indirectly, 100% of the outstanding shares of voting capital stock
of Alliance PLC, Alliance Group, Source, Difco, AROC (Texas), Alliance USA,  LPC
or GOC, on a fully diluted basis, (c) one-third or more of the directors of
Buyer shall consist of persons not nominated by Buyer's Board of Directors (not
including as Board nominees any directors which the Board is obligated to
nominate pursuant to shareholders agreements, voting trust arrangements or
similar arrangements) or (d) within three years of the Closing Date, the
employment by  Buyer of John Keenan or Paul Fenemore terminates for any reason.

     "Charter Amendment Approval" means approval of the increase in authorized
shares of Common Stock of the Company to such level as shall permit the full and
complete conversion of the Preferred Shares into the Preferred Conversion Shares
in accordance with the Certificate of Designation, all in accordance with the
Organic Documents and Applicable Law.

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

     "Common Stock" means common stock, $0.001 par value per share, of Buyer and
any securities issued or issuable with respect to such shares by way of a stock
dividend or stock split or in connection with a combination of shares,
recapitalization, merger, consolidation or other reorganization.

     "Companies Act" means the Companies Act 1985 as amended.

                                       2
<PAGE>

     "Default" means an Event of Default and any default, event or condition
which would, with the giving of any requisite notices and the passage of any
requisite periods of time, constitute an Event of Default.

     "Difco" means Difco Limited, a private limited company incorporated under
the laws of England and Wales.

     "Environmental Laws" means any and all laws relating to the environment or
to emissions, discharges, releases or threatened releases of pollutants,
contaminants, chemicals, or industrial, toxic or hazardous substances or wastes
into the environment including ambient air, surface water, ground water, or
land, or otherwise relating to the manufacture, processing, distribution, use,
treatment, storage, disposal, transport, or handling of pollutants,
contaminants, chemicals, or industrial, toxic or hazardous substances or wastes.

     "Environmental Obligations" means responsibility and liability for any of
the following occurrences, events and activities relating to the Properties,
whether arising before or after the Effective Date:  (i) environmental pollution
or contamination; (ii) underground injection activities or waste disposal onsite
or offsite; (iii) cleanup responses, and the costs of remediation, control or
compliance with respect to surface and subsurface pollution caused by spills,
pits, ponds or lagoons; (iv) failure to comply with applicable land use, surface
disturbance, licensing or notification requirements; or (v) violation of
Environmental Laws.

     "ERISA" means the Employee Retirement Income Security Act of 1974, as
     amended.

     "Exchange Act" means the U.S. Securities Exchange Act of 1934, as amended.

     "Excluded Environmental Obligations" means responsibility and liability for
any matter asserted by Buyer to Seller as a breach of a representation and
warranty in Section 4.17 in accordance with, and subject to the provisions of,
Sections 17.1 and 17.5.

     "Fiscal Quarter"  means a three-month period ending on July 31, October 31,
January 31 or April 30 of any year.

     "Fiscal Year"  means the twelve-month period ending on April 30 of any
     year.

     "GOC" means Germany Oil Company, a Delaware corporation.

     "Governmental Entity" means any court or tribunal in any jurisdiction
(domestic or foreign) or any federal, state, municipal or other governmental
body, agency, authority, department, commission, board, bureau or
instrumentality (domestic or foreign).

     "Hazardous Materials" means any substance regulated under Environmental
Law, whether as pollutants, contaminants, or chemicals, or as industrial, toxic
or hazardous substances or wastes, or otherwise.

                                       3
<PAGE>

     "HSR Act" means the Hart-Scott-Rodino Antitrust Improvements Act of 1976,
as amended.

     "Indebtedness" of any Person means Liabilities in any of the following
categories: (a) Liabilities for borrowed money; (b) Liabilities constituting an
obligation to pay the deferred purchase price of property or services; (c)
Liabilities evidenced by a bond, debenture, note or similar instrument; (d)
Liabilities which  would under U.S. GAAP be shown on such Person's balance sheet
as a liability, and  is payable more than one year from the date of creation
thereof (other than reserves for taxes and reserves for contingent obligations);
(e) Liabilities arising under futures contracts, forward contracts, swap, cap or
collar contracts, option contracts, hedging contracts, other derivative
contracts, or similar agreements; (f) Liabilities constituting principal under
leases capitalized in accordance with U.S. GAAP; (g) Liabilities arising under
conditional sales or other title retention agreements; (h) Liabilities owing
under direct or indirect guaranties of Liabilities of any other Person or
constituting obligations to purchase or acquire or to otherwise protect or
insure a creditor against loss in respect of Liabilities of any other Person
(such as obligations under working capital maintenance agreements, agreements to
keep-well, or agreements to purchase Liabilities, assets, goods, securities or
services), but excluding endorsements in the ordinary course of business of
negotiable instruments in the course of collection; (i) Liabilities (for
example, repurchase agreements) consisting of an obligation to purchase
securities or other property, if such Liabilities arise out of or in connection
with the sale of the same or similar securities or property; (j) Liabilities
with respect to letters of credit or applications or reimbursement agreements
therefor; (k)  Liabilities with respect to payments received in consideration of
oil, gas, or other minerals yet to be acquired or produced at the time of
payment (including obligations under "take-or-pay" contracts to deliver gas in
return for payments already received and the undischarged balance of any
production payment created by such Person or for the creation of which such
Person directly or indirectly received payment); or (l) Liabilities with respect
to other obligations to deliver goods or services in consideration of advance
payments therefor; provided, however, that the "Indebtedness" of any Person
shall not include Liabilities that were incurred by such Person on ordinary
trade terms to vendors, suppliers, or other Persons providing goods and services
for use by such Person in the ordinary course of its business, unless and until
such Liabilities are outstanding more than 90 days past the original invoice or
billing date therefor.

     "IRS" means the Internal Revenue Service.

     "Key Employment Agreements" means (i) that certain Executive Employment
Agreement dated as of December 8, 1999 between Buyer and John A. Keenan, and
(ii) that certain Service Agreement dated September 20, 1996 between Alliance
PLC and Paul Raymond Fenemore, as amended by Supplemental Agreement dated
September 20, 1996, Second Supplemental Agreement dated December 1, 1998, and
letter agreement dated as of December 8, 1999.

     "Liabilities" means, as to any Person, all indebtedness, liabilities and
obligations of such Person, whether matured or unmatured, liquidated or
unliquidated, primary or secondary, direct or absolute, fixed or contingent, and
whether or not required to be considered pursuant to U.S. GAAP.

                                       4
<PAGE>

     "Lien"  means, with respect to any property or assets, any right or
interest therein of a creditor to secure Liabilities owed to such creditor or
any other arrangement with such creditor which provides for the payment of such
Liabilities out of such property or assets or which allows him to have such
Liabilities satisfied out of such property or assets prior to the general
creditors of any owner thereof, including any lien, mortgage, security interest,
pledge, deposit, production payment, rights of a vendor under any title
retention or conditional sale agreement or lease substantially equivalent
thereto, tax lien, mechanic's or materialman's lien, or any other charge or
encumbrance for security purposes, whether arising by law or agreement or
otherwise, but excluding any right of offset which arises without agreement in
the ordinary course of business.  "Lien" shall also mean any filed financing
statement, any registration of a pledge (such as with an issuer of
uncertificated securities), or any other arrangement or action which would serve
to perfect a Lien described in the preceding sentence, regardless of whether
such financing statement is filed, such registration is made, or such
arrangement or action is undertaken before or after such Lien exists.

     "Listing Rules" means the listing rules of the London Stock Exchange.

     "London Stock Exchange" means the London Stock Exchange Limited.

     "LPC" means LaTex Petroleum Corporation, an Oklahoma corporation.

     "LRI" means LaTex Resources, Inc., a Delaware corporation.

     "LRI Merger" means the merger of Alliance Resources (Delaware) Inc. with
and into LRI whereby Alliance PLC became the sole shareholder of LRI.

     "Material Adverse Effect" means (a) when used with respect to Buyer, a
material adverse change in, or a material adverse effect upon (i) the business,
assets, results of operations, condition (financial or otherwise) or prospects
of Buyer and its Subsidiaries on a consolidated basis, (ii) Buyer's ability to
timely pay the Obligations or to perform on a timely basis any material
obligation of Buyer under this Agreement or any agreement, instrument, or
document entered into or delivered in connection herewith or (iii) the
enforceability of the material terms of this Agreement or any Ancillary
Document; and (b) when used with respect to Seller,  a material adverse change
in, or a material adverse effect upon (i) the Properties or (ii) the
enforceability of the material terms of this Agreement or any Ancillary
Document.

     "Old LaTex Payables" means those current accounts payable to Buyer or its
consolidated Subsidiaries that meet one or more of the following tests and have
been certified to Seller by Buyer and applicable Subsidiary as being an Old
LaTex Payable:

          (a) accounts payable the collection of which is barred by the
applicable statute of limitations;

          (b) accounts payable the collection of which has been compromised or
forgiven in part, in either case to the extent of the amount that has been
compromised or forgiven; or

                                       5
<PAGE>

          (c) accounts payable in respect of which the indebtedness was incurred
prior to the LRI Merger and where each of the following is true: (i) no payment
has been made on an individual amount of indebtedness payable since the LRI
Merger, (ii) no contact has been received by Buyer or applicable Subsidiary from
the applicable creditor since the LRI Merger pertaining to such account or if
contact has been received, such account is being diligently contested in good
faith, (iii) no promise to pay such account has been made by Buyer or applicable
Subsidiary since the LRI Merger and (iv) no judgment has been obtained by, or
settlement agreement entered into with, such creditor with respect to such
indebtedness.

     "Other Acquisition  Agreements" means other agreements or proposed
agreements to which Buyer is a party and disclosed in writing to Seller, whereby
Buyer will issue shares of  Series A Preferred, in exchange for interests in
oil, gas and mineral properties and related assets.

     "Outstanding Common Stock" means, at any time, the aggregate of all Common
Stock then outstanding, including all shares of Common Stock which could be
acquired from the Company upon exercise  or conversion of any outstanding
warrants, options or other securities then exercisable or convertible into
Common Stock.

     "Permits" means licenses, permits, franchises, consents, approvals,
variances, exemptions and other authorizations of or from Governmental Entities.

     "Permitted Investment" means any investment, loan, advance, guaranty or
capital contribution by Buyer or any Subsidiary in any of the following: (a)
properties or assets to be used in the ordinary course of business of Buyer and
its Subsidiaries; (b) current assets arising from the sale of goods and services
in the ordinary course of business of Buyer and its Subsidiaries; (c)
investments in one or more of Buyer's Subsidiaries or in any Person that
concurrently with such investment becomes a Subsidiary; (d) any marketable
obligation maturing not later than one year after the date of acquisition
therefor, issued or guaranteed by the United States of America or by any agency
of the United States of America which has the full faith and credit of the
United States of America; (e) commercial paper which is given the highest rating
by a credit rating agency of recognized national standing and maturing not more
than 270 days from the date of creation thereof; and (f) any demand deposit or
time deposit (including certificates of deposit and money market or sweep
accounts) with a commercial bank or trust company organized and doing business
under the laws of the United States of America or any state thereof which has
capital, surplus and undivided profits of at least $250,000,000, provided that
such deposit must be either payable on demand or mature not more than twelve
months from the date of investment therein.

     "Person" means any individual, corporation, partnership, joint venture,
association, joint-stock company, trust, enterprise, unincorporated organization
or Governmental Entity.

     "Preferred Conversion Shares" means the shares of Common Stock issuable
upon conversion of the Preferred Shares.

                                       6
<PAGE>

     "Preferred Stock Purchase Agreement" means that certain Preferred Stock
Purchase Agreement dated as of May 1, 2000, by and among Buyer, Bank of America,
N.A., EnCap Equity 1996 Limited Partnership, Energy Capital Investment Company
PLC,  El Paso Capital Investments, L.L.C., EF-II Holdings, LLC, Picosa Creek
Limited Partnership and EnCap Investments L.L.C.

     "Proceedings" means all proceedings, actions, claims, suits, investigations
and inquiries by or before any arbitrator or Governmental Entity.

     "Reasonable best efforts" means a party's reasonable best efforts in
accordance with reasonable commercial practice and without the incurrence of
unreasonable expense.

     "Restricted Payment" means any Distribution (as defined below) in respect
of Buyer or any Subsidiary thereof (other than on account of capital stock or
other equity interests of a Subsidiary owned legally or beneficially by the
Seller or another Subsidiary), including any Distribution resulting in the
acquisition by Buyer of securities that would constitute treasury stock.  As
used in this definition, "Distribution" shall mean, in respect of any
corporation, partnership or other business entity (a) dividends or other
distributions or payments on capital stock or other equity interest of such
corporation, partnership or other business entity (except distributions in such
stock or other equity interest) and (b) the redemption or acquisition of such
stock or other equity interests or of warrants, rights or other options to
purchase such stock or other equity interests (except when solely in exchange
for such stock or other equity interests); provided, that "Distribution" shall
not mean any dividend or other distribution made, or redemption effected, in
accordance with the terms of the Certificate of Designation.

     "Securities Act" means the U.S. Securities Act of 1933, as amended.

     "Securities and Exchange Commission" means the U.S. Securities and Exchange
Commission.

     "Seller Disclosure Schedule" shall mean a schedule delivered by Seller to
Buyer which sets forth additional information regarding the representations and
warranties of Seller contained herein and information called for hereby.

     "Senior Credit Facility" means that certain Credit Agreement dated as of
May 1, 2000, by and among Buyer, Toronto Dominion (Texas), Inc., as Agent, and
the lenders signatory.

     "Series A Preferred" means shares of Buyer's Series A Preferred Stock,
$.001 par value per share.

     "Source" means Source Petroleum, Inc., a Louisiana corporation.

     "Subordinated Debt" means that certain Indebtedness of Buyer evidenced by
the Subordinated Debt Agreement.

                                       7
<PAGE>

     "Subordinated Debt Agreement" means that certain Purchase Agreement dated
as of May 1, 2000, by and among Buyer, EnCap Equity 1996 Limited Partnership and
El Paso Capital Investments, L.L.C.

     "Subsidiary" means any corporation more than 50% of whose outstanding
voting securities, or any general partnership, joint venture or similar entity
more than 50% of whose total equity interests, is owned, directly or indirectly,
by the Buyer, or any limited partnership of which Buyer or any Subsidiary is a
general partner.

     "Taxes" means any income taxes or similar assessments or any sales, excise,
occupation, use, ad valorem, property, production, severance, transportation,
employment, payroll, franchise, transfer, stamp, withholding or other tax
imposed by any United States federal, state or local (or any foreign or
provincial) taxing authority, including any interest, penalties or additions
attributable thereto.

     "Tax Return" means any return or report (including but not limited to any
related or supporting information, any amended return or report or any
information return or report) with respect to Taxes.

     "Treasury Regulations" means one or more treasury regulations promulgated
under the Code by the Treasury Department of the United States.

     "U.S. GAAP" means generally accepted accounting principles in the United
States of America from time to time.

      Section 1.2.  Certain Additional Defined Terms.  In addition to such terms
                    --------------------------------
as are defined in the opening paragraph and in Section 1.1 of this Agreement,
the following terms are used in this Agreement as defined in the Sections set
forth opposite such terms:

             Defined Term                                Section Reference
          ----------------------------------------      --------------------
          Asserted Defects........................                 7.1 (a)
          Assignment..............................                 9.2 (a)
          Audited Financial Statements............                 5.10
          Base Purchase Price.....................             Article III
          Basic Documents.........................                 4.7
          Closing.................................                 9.1
          Closing Date............................                 9.1
          Data....................................              Article II(f)
          Disbursement Properties.................                 4.15
          Effective Date..........................                 9.2 (a)
          Event of Default........................                15.1
          Financial Statements....................                 5.10
          Latest Balance Sheet....................                 5.10
          Net Title Adjustments...................                 7.2 (c)
          non-operators...........................                 4.15

                                       8
<PAGE>

             Defined Term                                Section Reference
          ----------------------------------------      --------------------
          Oil and Gas Properties..................           Article II
          Operated Properties.....................               4.15
          Organic Documents.......................               5.3
          Permitted Liens.........................              14.2
          Preferred Shares........................           Article II
          Properties..............................           Article II
          Purchase Price..........................           Article III
          Scheduled Production Sales Contracts....               4.9
          Unaudited Financial Statements..........               5.10

     Section 1.3.   References, Titles and Construction.
                    ------------------------------------

          (a)  All references in this Agreement to articles, sections,
subsections and other subdivisions refer to corresponding articles, sections,
subsections and other subdivisions of this Agreement unless expressly provided
otherwise.

          (b)  Titles appearing at the beginning of any of such subdivisions are
for convenience only and shall not constitute part of such subdivisions and
shall be disregarded in construing the language contained in such subdivisions.

          (c)  The words "this Agreement", "this instrument", "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.

          (d)  Words in the singular form shall be construed to include the
plural and vice versa, unless the context otherwise requires. Pronouns in
           ---- -----
masculine, feminine and neuter genders shall be construed to include any other
gender.

          (e)  Unless the context otherwise requires or unless otherwise
provided herein, the terms defined in this Agreement which refer to a particular
agreement, instrument or document also refer to and include all renewals,
extensions, modifications, amendments or restatements of such agreement,
instrument or document, provided that nothing contained in this subsection shall
be construed to authorize such renewal, extension, modification, amendment or
restatement.

          (f)  Examples shall not be construed to limit, expressly or by
implication, the matter they illustrate.

          (g)  The word "or" is not intended to be exclusive and the word
"includes" and its derivatives means "includes, but is not limited to" and
corresponding derivative expressions.

          (h)  No consideration shall be given to the fact or presumption that
one party had a greater or lesser hand in drafting this Agreement.

                                       9
<PAGE>

          (i)  All references herein to "$" or "dollars" shall refer to U.S.
Dollars.

                                  ARTICLE II

                       Property to be Sold and Purchased
                       ---------------------------------

     Seller agrees to sell and Buyer agrees to purchase, for the consideration
hereinafter set forth, and subject to the terms and provisions herein contained,
the following described properties, rights and interests:

          (a)  All of those properties described in Exhibit II attached
                                                    ----------
hereto and made a part hereof for all purposes;

          (b)  Without limitation of the foregoing, all other right, title and
interest (of whatever kind or character, whether legal or equitable, and whether
vested or contingent) of Seller in and to the oil, gas and other minerals in and
under or that may be produced from the lands described in Exhibit II hereto
                                                          ----------
(including interests in oil, gas and/or mineral leases covering such lands,
overriding royalties, production payments and net profits interests in such
lands or such leases, and fee mineral interests, fee royalty interests and other
interests in such oil, gas and other minerals), whether such lands are described
in a description set forth in such Exhibit II or are described in such Exhibit
                                   ----------                          -------
II by reference to another instrument (and without limitation by any depth
--
limitations that may be set forth in such Exhibit II or in any such instrument
                                          ----------
so referred to for description), even though Seller's interest in such oil, gas
and other minerals may be incorrectly described in, or omitted from, such
Exhibit II;
----------

          (c)  All rights, titles and interests of Seller in and to, or
otherwise derived from, all presently existing and valid oil, gas and/or mineral
unitization, pooling, and/or communitization agreements, declarations and/or
orders and in and to the properties covered and the units created thereby
(including all units formed under orders, rules, regulations, or other official
acts of any federal, state, or other authority having jurisdiction, voluntary
unitization agreements, designations and/or declarations) relating to the
properties described in paragraphs (a) and (b) above;

          (d)  All rights, titles and interests of Seller in and to all
presently existing and valid production sales (and sales related) contracts,
operating agreements, and other agreements and contracts which relate to any of
the properties described in paragraphs (a), (b) and (c) above, or which relate
to the exploration, development, operation, or maintenance thereof or the
treatment, storage, transportation or marketing of production therefrom (or
allocated thereto);

          (e)  All rights, titles and interests of Seller in and to all
materials, supplies, machinery, equipment, improvements and other personal
property and fixtures (including, but not by way of limitation, all wells,
wellhead equipment, pumping units, flowlines, tanks, buildings, injection
facilities, saltwater disposal facilities, compression facilities, gathering
systems, and other equipment), and all easements, rights-of-way, surface leases
and other surface rights, all permits and licenses, and all other appurtenances
being used or held for use in connection with, or otherwise related to, the

                                       10
<PAGE>

exploration, development, operation or maintenance of any of the properties
described in paragraphs (a), (b) and (c) above, or the treatment, storage,
transportation or marketing of production therefrom (or allocated thereto);

          (f)  All of Seller's lease files, abstracts and title opinions,
production records, well files, accounting records (but not including general
financial accounting records), seismic records and surveys, gravity maps,
electric logs, geological or geophysical data and records, and other files,
documents and records of every kind and description which relate to the
properties described above (collectively "Data"); and

          (g)  Without limiting the generality of the foregoing, all of Seller's
rights, titles, claims and interests in and to all of the properties, rights and
interests incident to the items specified in the foregoing paragraphs of this
Article II.

The properties and interests specified in the foregoing paragraphs (a), (b) and
(c) are herein sometimes collectively called the "Oil and Gas Properties," and
the properties and interests specified in the foregoing paragraphs (a), (b),
(c), (d), (e), (f) and (g) are herein sometimes collectively called the
"Properties".

                                  ARTICLE III

                                Purchase Price
                                ---------------

     In consideration of the sale of the Properties by Seller to Buyer, Buyer
shall pay to Seller at Closing an aggregate purchase price (the "Base Purchase
Price") consisting of  202,640 shares of Series A Preferred (the "Preferred
Shares").  The rights, designations, preferences and other terms and conditions
relating to the Preferred Shares shall be as set forth in the Certificate of
Designation attached hereto as Exhibit 3.1.  The Base Purchase Price may be
                               -----------
adjusted as provided in Article VII (the Base Purchase Price, as so adjusted,
and as the same may be otherwise adjusted by the mutual agreement of the
parties, being called the "Purchase Price").

                                  ARTICLE IV

                   Representations and Warranties of Seller
                   ----------------------------------------

     Subject to the Seller Disclosure Schedule, Seller represents and warrants
to Buyer as follows:

      Section 4.1.  Organization and Existence.  Seller is a limited partnership
                    --------------------------
duly formed and validly existing under the laws of the State of Texas.

      Section 4.2.  Authority Relative to This Agreement.  Seller has full power
                    ------------------------------------
and authority to execute, deliver, and perform this Agreement and the Ancillary
Documents and to consummate the transactions contemplated hereby and thereby.
The execution, delivery, and performance by

                                       11
<PAGE>

Seller of this Agreement and the Ancillary Documents and the consummation by it
of the transactions contemplated hereby and thereby, have been duly authorized
by all necessary action of Seller.

      Section 4.3.  Valid and Binding Agreement.  This Agreement has been duly
                    ---------------------------
executed and delivered by Seller and constitutes, and each Ancillary Document
has been, or when executed will be, duly executed and delivered by Seller and
constitutes, or when executed and delivered will constitute, a valid and legally
binding obligation of Seller, enforceable against it in accordance with their
respective terms, except that such enforceability may be limited by (a)
applicable bankruptcy, insolvency, reorganization, moratorium, and similar laws
affecting creditors' rights generally and (b) equitable principles which may
limit the availability of certain equitable remedies (such as specific
performance) in certain instances.

      Section 4.4.  Non-Contravention.  Other than requirements (if any) that
                    -----------------
there be obtained consents to assignment (or waivers of preferential rights to
purchase) from third parties, and except for approvals required to be obtained
from governmental entities who are lessors under leases forming a part of the
Oil and Gas Properties (or who administer such leases on behalf of such lessors)
which are customarily obtained post-closing, neither the execution, delivery,
and performance by Seller of this Agreement and each other agreement,
instrument, or document executed or to be executed by Seller in connection with
the transactions contemplated hereby nor the consummation by it of the
transactions contemplated hereby and thereby do and will (a) conflict with or
result in a violation of any provision of the partnership agreement or other
governing instruments of Seller, (b) conflict with or result in a violation of
any provision of, or constitute (with or without the giving of notice or the
passage of time or both) a default under, or give rise (with or without the
giving of notice or the passage of time or both) to any right of termination,
cancellation, or acceleration under, any bond, debenture, note, mortgage,
indenture, lease, contract, agreement, or other instrument or obligation to
which Seller is a party or by which Seller, any of its properties or the
Properties may be bound, (c) result in the creation or imposition of any lien or
other encumbrance upon the properties of Seller or the Properties, or (d)
violate any Applicable Law binding upon Seller.

      Section 4.5.  Approvals.  Other than requirements (if any) that there be
                    ---------
obtained consents to assignment (or waivers of preferential rights to purchase)
from third parties, and except for approvals required to be obtained from
governmental entities who are lessors under leases forming a part of the Oil and
Gas Properties (or who administer such leases on behalf of such lessors) which
are customarily obtained post-closing, no consent, approval, authorization.
license, order or permit of, or declaration, filing, or registration with, any
Governmental Entity or any other Person or entity is required to be obtained or
made by Seller in connection with the execution, delivery, or performance by
Seller of this Agreement  or any Ancillary Document and the consummation of the
transactions contemplated hereby and thereby.

      Section 4.6.  Pending Litigation.  There are no Proceedings pending, or to
                    ------------------
the best knowledge of Seller, threatened, which affect the Properties (including
any actions challenging or pertaining to Seller's title to any of the
Properties), or affecting the execution and delivery of this Agreement or the
consummation of the transactions contemplated hereby.  None of Seller or any of

                                       12
<PAGE>

the Properties is subject to any judgment, order, writ, injunction, or decree of
any Governmental Entity.

      Section 4.7.  Basic Documents.  The oil, gas and/or mineral leases,
                    ---------------
interests in which comprise parts of the Oil and Gas Properties, and all other
material contracts and agreements, licenses, permits and easements, rights-of-
way and other rights-of-surface use comprising any part of or otherwise relating
to the Properties (such leases and such material contracts, agreements,
licenses, permits, easements, rights-of-way and other rights-of-surface use,
including any amendments or modifications, being herein called the "Basic
Documents"), are in full force and effect and constitute valid and binding
obligations of the parties thereto and are enforceable in accordance with their
respective terms. All Basic Documents are disclosed on Exhibit II in connection
                                                       ----------
with the descriptions of the Oil and Gas Properties to which they relate or
otherwise in the Seller Disclosure Schedule.  Seller is not in breach or default
(and no situation exists which with the passing of time or giving of notice
would create a breach or default) of its obligations under the Basic Documents
or any regulations incorporated in or governing same, and (to the best of
Seller's knowledge) no breach or default by any third party (or situation which
with the passage of time or giving of notice would create a breach or default)
exists, to the extent such breach or default (whether by Seller or such a third
party) could materially adversely affect the ownership, operation, value or use
of any Oil and Gas Property of  Buyer after the Effective Date.  All payments
(including all delay rentals, royalties, shut-in royalties and valid calls for
payment or prepayment under operating agreements) owing under Basic Documents
have been and are being made (timely, and before the same became delinquent) by
Seller in all material respects (and, where the non-payment of same by a third
party could materially adversely affect the ownership, operation, value or use
of an Oil and Gas Property after the Effective Date, have been and are being
made, to the best knowledge of Seller, by such third parties).  For the purposes
of the representations contained in this Section (and without limitation of such
representations), the non-payment of an amount, or non-performance of an
obligation, where such non-payment, or non-performance, could result in the
forfeiture or termination of rights of Seller (or Buyer after Closing) under a
Basic Document, shall be considered material.  Seller is not a party to any
confidentiality agreements relating to the Properties.  Seller has rights in the
Data and has the power and authority to transfer the Data to Buyer pursuant to
this Agreement.  After Closing, Buyer shall have the power and authority to use
the Data in accordance with the terms of the Basic Documents in connection with
the exploration and development of the properties for oil and gas.

      Section 4.8.  Commitments, Abandonments or Proposals.  Except as set forth
                    --------------------------------------
on Seller's Disclosure Schedule 4.8: (a) Seller has incurred no expenses, and
has made no commitments to make expenditures (including Seller has not entered
into any agreements that would obligate Seller to make expenditures), in
connection with (and no other obligations or liabilities have been incurred
which would adversely affect) the ownership or operation of the Properties after
the Effective Date, other than routine expenses incurred in the normal operation
of existing wells on the Oil and Gas Properties;  (b) Seller has not abandoned,
and has not entered into any agreements or arrangements to abandon, any wells
(or removed any material items of equipment, except those replaced by items of
equal suitability and value) on the Oil and Gas Properties since the Effective
Date; and (c) no proposals are currently outstanding (whether made by Seller or
by any other party) to drill additional wells, or to deepen, plug back, or
rework existing wells, or to conduct other operations for which

                                       13
<PAGE>

consent is required under the applicable operating agreement, or to conduct any
other operations other than normal operation of existing wells on the Oil and
Gas Properties, or to abandon any wells, on the Oil and Gas Properties. There
are no operations involving any of the Properties with respect to which Seller
has become a non-consenting party.

      Section 4.9.  Production Sales Contracts.  There exist no agreements or
                    --------------------------
arrangements for the sale of production from the Oil and Gas Properties
(including without limitation, calls on, or other rights to purchase,
production, whether or not the same are currently being exercised) other than
(a) production sales contracts (in this Section, the "Scheduled Production Sales
Contracts") disclosed in Section 4.9 of the Seller Disclosure Schedule or (b)
agreements or arrangements which are cancelable on 60 days notice or less
without penalty or detriment.  Seller is presently receiving a price for all
production from (or attributable to) each Oil and Gas Property covered by a
Scheduled Production Sales Contract as computed in accordance with the terms of
such contract, and is not having deliveries of gas from any Oil and Gas Property
subject to a Scheduled Production Sale Contract curtailed substantially below
such property's delivery capacity.  There are no prepayments, advance payments,
take-or-pay payments or similar payments affecting the Properties.

      Section 4.10. Plugging and Abandonment.   There are no dry holes, or shut
                    ------------------------
in or otherwise inactive wells, located on the Oil and Gas Properties or on
lands pooled or unitized therewith (including any wells which would, if located
in Texas, require compliance with Railroad Commission Rule 14(b)(2)), except for
wells that have been properly plugged and abandoned, and except for wells
drilled to depths not included within the Oil and Gas Properties or within units
in which the Oil and Gas Properties participate which have never been completed
in such depths.

      Section 4.11. Licenses and Permits.  Seller has all Permits necessary or
                    --------------------
appropriate to own and operate the Properties as presently being owned and
operated, and such Permits  are in full force and effect (and are transferrable
to Buyer or are subject to being routinely replaced by a license or permit
issued to Buyer as a successor owner of the Properties), and Seller has not
received written notice of any violations in respect of any such Permits.

      Section 4.12. Area of Mutual Interest and Other Agreements; Tax
                    -------------------------------------------------
Partnerships.  No Oil and Gas Property is subject to (or has related to it) any
------------
area of mutual interest agreements.  No Oil and Gas Property is subject to (or
has related to it) any farm-out or farm-in agreement under which any party
thereto is entitled to receive assignments not yet made, or could earn
additional assignments after the Effective Date.  No Oil and Gas Property is
subject to (or has related to it) any tax partnership.

      Section 4.13. Payment of Expenses.  All expenses (including all bills for
                    -------------------
labor, materials and supplies used or furnished for use in connection with the
Properties, and all severance, production, ad valorem, windfall profit and other
similar taxes) and liabilities relating to the ownership or operation of the
Properties, have been, and are being, paid (timely, and before the same become
delinquent) by Seller.

                                       14
<PAGE>

      Section 4.14. Compliance with Laws.  The ownership and operation of
                    --------------------
Properties, to the extent that non-conformance could adversely affect the
ownership, operation, value or use thereof after the Effective Date (or
otherwise affect Buyer), has been in conformity, in all material respects, with
all Applicable Laws, except for such non-compliance which would not have a
Material Adverse Effect.  Without limitation of the foregoing, all oil and gas
wells comprising a part of the Properties have been drilled and completed within
the boundaries of the applicable leases or within limits otherwise permitted by
a valid and enforceable pooling, unit, or other agreement or contract or by
applicable law, and no well comprising a part of the Properties is or was
subject to any penalty on allowables after the Effective Date because of any
over-production (or any other judgments, orders or decrees of any court or
governmental authority or agency) which would (or did) prevent such well from
being entitled to its full legal and regular allowable (as prescribed by any
court or governmental body or agency) from and after the Effective Date.

      Section 4.15. Operated Properties.  Seller has listed in Section 4.15 of
                    -------------------
the Seller Disclosure Schedule all of the Oil and Gas Properties (in this
Section, the "Operated Properties") where Seller or an Affiliate thereof serves
as operator, for itself and such other parties (in this Section, "non-
operators").  All bills to non-operators for reimbursement of operating expenses
incurred with respect to the Operated Properties are being rendered, and (except
for amounts totaling less than $25,000) paid, on a current basis; Seller has
made no advance billings to non-operators for estimated costs which have not
heretofore been reconciled to actual costs with full credit having been given
for funds advanced (and Seller, therefore, holds no funds advanced by a non-
operator as pre-payment of estimated future costs).  Seller has listed in
Section 4.15 of the Seller Disclosure Schedule all wells with respect to which
it is disbursing proceeds of production to third parties owning interests in the
production from such wells (in this Section, the "Disbursement Properties").
All of such proceeds of production being so accounted for (except proceeds,
aggregating less than $25,000, attributable to interests being held in suspense
in accordance with prudent industry practice) have been, and are being,
accounted for under appropriate division orders, transfer orders or similar
documents signed by, or otherwise clearly binding on, the parties receiving such
proceeds and reflecting, as to each party, the decimal interest such party is
being paid upon; to the best of Seller's knowledge, Seller has been correctly
accounting to such third parties for such proceeds of production.

      Section 4.16. Physical Condition of Facilities.  The surface physical
                    --------------------------------
facilities on the Properties have been maintained in accordance with normal
industry maintenance practices and are in a state of repair (normal wear and
tear excepted) that Seller believes to be adequate for the normal use of such
facilities in the ordinary conduct of the business of Seller.  Without limiting
the foregoing, but subject to ordinary wear and tear, such facilities are not in
need of maintenance or improvements except for maintenance and improvements in
the ordinary course in accordance with normal industry practice.

      Section 4.17. Environmental Matters.  (i) Seller is in material compliance
                    ---------------------
with all applicable federal, state, local and foreign laws, regulations, rules,
orders, decrees, treaties, judicial decisions, judgments, injunctions, permits
and governmental restrictions relating to pollution or protection of human
health or the environment (including ambient air, surface water, ground water,
land surface or subsurface strata) (collectively "Environmental Laws"), except
for such non-

                                       15
<PAGE>

compliance as could not, individually or in the aggregate, reasonably be
expected to have a Material Adverse Effect, and, to the best knowledge of
Seller, there are no circumstances that are reasonably likely to materially
prevent or interfere with such compliance in the next three years, and (ii)
neither Seller nor any of its Subsidiaries has received written notice of or, to
the best knowledge of Seller, is the subject of, any actions, causes of action,
claims, investigations, demands, notices, requests for information, complaints,
suits or proceedings by any Person alleging liability under or non-compliance
with any Environmental Law that are reasonably likely, individually or in the
aggregate, to have a Material Adverse Effect. Buyer acknowledges that this
Section 4.17 is the exclusive representation and warranty made by Seller in this
Agreement with respect to applicable Environmental Laws and no other
representation and warranty in this Agreement shall be deemed to cover such
matters.

      Section 4.18. Production Data.  Seller has provided to representatives of
                    ---------------
Buyer aggregate production data on the Properties and data on lease operating
expenses incurred on the Properties. To the best knowledge of Seller, all of
such data is accurate and complete in all material respects as of the date
provided.

      Section 4.19. Ordinary Course Operations.  Except as set forth on Seller's
                    --------------------------
Disclosure Schedule 4.8, since January 1, 2000, Seller has not operated or in
any manner dealt with, incurred obligations with respect to, or undertaken any
transactions relating to, the Properties other than in the ordinary course of
business consistent with past practice and none of the Properties has suffered
any material destruction, damage, or loss (except depreciation of equipment
through ordinary wear and tear) or been subjected by Seller to any mortgage,
lien, encumbrance, claim, or security interest that has not previously been
disclosed to representatives of Buyer or that would constitute a Material
Adverse Effect.

      Section 4.20. Sale of Production.  Except as described in Section 4.20 of
                    ------------------
the Seller Disclosure Schedule, there is no well on the Properties with respect
to which Seller and its predecessors in title to the Properties have
collectively taken more (referred to herein as "overproduced") or less (referred
to herein as "underproduced") production from such well than the ownership of
Seller and such predecessors would entitle Seller and such predecessors (absent
any gas balancing agreement or arrangement) to receive.  The overproduced and
underproduced positions disclosed on Section 4.20 of the  Seller Disclosure
Schedule are, in each case, materially accurate as of the dates shown on such
schedule.

      Section 4.21. [Intentionally Omitted].
                    -----------------------

      Section 4.22. Brokerage Fees.  Neither Seller nor any of its affiliates
                    --------------
has retained any financial advisor, broker, agent or finder or paid or agreed to
pay any financial advisor, broker, agent or finder on account of this Agreement
or any transaction contemplated hereby, which action would subject Buyer or any
of its affiliates to any liability.  Seller shall indemnify and hold harmless
Buyer from and against any and all losses, claims, damages and liabilities
(including legal and other expenses reasonably incurred in connection with
investigating or defending any claims or actions) with respect to any finder's
fee, brokerage commission or similar payment in connection with any transaction

                                       16
<PAGE>

contemplated hereby asserted by any Person on the basis of any act or statement
made or alleged to have been made by Seller or any of its affiliates.

      Section 4.24. Bankruptcy.  There are no bankruptcy, reorganization or
                    ----------
arrangement proceedings pending, being contemplated by, or to the knowledge of
Seller, threatened against Seller.

      Section 4.25. Full Disclosure.  No representation or warranty made by
                    ---------------
Seller in this Agreement, and no statement of Seller contained in any document,
certificate or other writing furnished or to be furnished by Seller or its
representatives to Buyer pursuant hereto or in connection herewith, contains or
will contain, at the time of delivery, any untrue statement of a material fact
or omits or will omit, at the time of delivery, to state any material fact
(other than industry-wide risks normally associated with the type of business
conducted by Seller) necessary to make the statements contained therein, in
light of the circumstances in which they are made, not misleading.  There is no
fact known to Seller (other than industry-wide risks normally associated with
the type of business conducted by Seller) that has not been disclosed to Buyer
in writing which Seller reasonably anticipates would result in a Material
Adverse Effect.

      Section 4.26. Disclaimer of Warranties.  Other than those expressly set
                    ------------------------
out in this Article IV, Seller hereby expressly disclaims any and all
representations or warranties with respect to the Properties or the transaction
contemplated hereby, and Buyer agrees that the Properties are being sold by
Seller "where is" and "as is".  Specifically as a part of (but not in limitation
of) the foregoing, Buyer acknowledges that Seller has not made, and Seller
hereby expressly disclaims, any representation or warranty (express, implied,
under common law, by statute or otherwise) as to (a) the condition of the
Properties (INCLUDING WITHOUT LIMITATION, SELLER DISCLAIMS ANY IMPLIED OR
EXPRESS WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR
CONFORMITY TO MODELS OR SAMPLES OF MATERIALS), (b) the status of title to the
Properties or (c) as the extent of oil, gas or other mineral reserves, the
recoverability of or the cost of recovering any such reserves, the value of such
reserves, prices (or anticipated prices) at which production will be sold and
the ability to sell oil or gas production from the Properties.

                                   ARTICLE V

                     Representations and Warranties of Buyer
                    ----------------------------------------

      Section 5.1.  Organization and Existence.  Buyer is a  corporation duly
                    --------------------------
organized and validly existing under the laws of Delaware.

      Section 5.2.  Qualification.  Each of Buyer and the Subsidiaries is duly
                    -------------
qualified or licensed to do business and, with respect to non-U.K. entities, in
good standing in each of the jurisdictions in which it owns, leases or operates
property or in which such qualification or licensing is required for the conduct
of its business.

                                       17
<PAGE>

     Section 5.3.  Charter and Bylaws.  Buyer has made available to Seller
                   ------------------
accurate and complete copies of Buyer's certificate of incorporation and  bylaws
("Organic Documents") as currently in effect, and stock records of Buyer.
Neither Buyer nor any Subsidiary is in violation of its Organic Documents or its
partnership agreement or similar governing document, as the case may be.

     Section 5.4.  Capitalization of Buyer.  Subject to Schedule 5.4, the
                   -----------------------              ------------
authorized capital stock of Buyer, the number of shares outstanding and the
number of shares held in Buyer's treasury are set forth on Schedule 5.4 hereto.
                                                           ------------
All outstanding shares of capital stock of Buyer have been validly issued and
are fully paid and nonassessable, and no shares of capital stock of Buyer are
subject to, nor have any been issued in violation of, preemptive or similar
rights.  Except as set forth on Schedule 5.4 hereto, there are (and as of the
                                ------------
Closing Date there will be) outstanding (i) no shares of capital stock or other
voting securities of Buyer, (ii) no securities of Buyer convertible into or
exchangeable for shares of capital stock or other voting securities of Buyer,
(iii) no options or other rights to acquire from Buyer, and no obligation of
Buyer to issue or sell, any shares of capital stock or other voting securities
of Buyer or any securities of Buyer convertible into or exchangeable for such
capital stock or voting securities, and (iv) no equity equivalents, interests in
the ownership or earnings or other similar rights of or with respect to Buyer.
There are (and as of the Closing Date there will be) no outstanding obligations
of Buyer or any Subsidiary to repurchase, redeem, or otherwise acquire any of
the foregoing shares, securities, options, equity equivalents, interests, or
rights.  Except as set forth on Schedule 5.4, Buyer is not a party to, and is
                                ------------
not aware of, any voting agreement, voting trust, or similar agreement or
arrangement relating to any class or series of its capital stock.

     Section 5.5.  Authority Relative to This Agreement.  Subject to Charter
                   ------------------------------------
Amendment Approval as it pertains to Buyer's ability to permit the full
conversion of the Preferred Shares into the Preferred Conversion Shares, Buyer
has full power and authority to execute, deliver, and perform this Agreement and
the Ancillary Documents to which it is a party and to consummate the
transactions contemplated hereby and thereby.  The execution, delivery, and
performance by Buyer of this Agreement and the Ancillary Documents to which it
is a party, and the consummation by it of the transactions contemplated hereby
and thereby, have been duly authorized by all necessary action of Buyer.  This
Agreement has been duly executed and delivered by Buyer and constitutes, and
each Ancillary Document executed or to be executed by Buyer has been, or when
executed will be, duly executed and delivered by Buyer and constitutes, or when
executed and delivered will constitute, a valid and legally binding obligation
of Buyer, enforceable against Buyer in accordance with their respective terms,
except that such enforceability may be limited by (i) applicable bankruptcy,
insolvency, reorganization, moratorium, and similar laws affecting creditors'
rights generally and (ii) equitable principles which may limit the availability
of certain equitable remedies (such as specific performance) in certain
instances.

     Section 5.6.  No Conflict.  Assuming all consents, approvals,
                   -----------
authorizations and other actions described in Section 5.7 have been obtained and
all filings and notifications listed on Schedule 5.7 have been made and except
                                        ------------
as described on Schedule 5.6, the execution, delivery and performance of this
                ------------
Agreement by Buyer, the execution, delivery and performance by each Subsidiary

                                       18
<PAGE>

of the Ancillary Documents to which it is a party, and the consummation by them
of the transactions contemplated hereby and thereby do not and will not (a)
violate or conflict with the Organic Documents of Buyer or any Subsidiary,
subject to Charter Amendment Approval as it pertains to Buyer's ability to
permit the full conversion of the Preferred Shares into Preferred Conversion
Shares, (b) conflict with or result in any violation of any provision of, or
constitute (with or without the giving of notice or the passage of time or both)
a default under, or give rise (with or without the giving of notice or the
passage of time or both) to any right of termination, cancellation, or
acceleration under, or require any consent, approval, authorization or waiver
of, or notice to, any party to, any bond, debenture, note, mortgage, indenture,
lease, contract, agreement, or other instrument or obligation to which Buyer or
any Subsidiary is a party or by which Buyer or any Subsidiary or any of their
respective properties may be bound or any Permit held by Buyer or any
Subsidiary, (iii) result in the creation or imposition of any Lien upon the
properties of Buyer or any Subsidiary (other than as provided in the Senior
Credit Facility) or (iv) violate any Applicable Law binding upon Buyer or any
Subsidiary.

     Section 5.7.  Consents and Approvals, Licenses, Etc.  Except as set forth
                   -------------------------------------
on Schedule 5.7, no consent, approval, authorization, license, order or permit
   ------------
of, or declaration, filing or registration with, or notification to, any
Governmental Entity, or any other Person or entity, is required to be made or
obtained by Buyer or any Subsidiary in connection with the execution, delivery
and performance of this Agreement or any Ancillary Document and the consummation
of the transactions contemplated hereby and thereby.

     Section 5.8.  Subsidiaries.
                   ------------

          (a)  Buyer does not own, directly or indirectly, any capital stock or
equity securities of any corporation or have any direct or indirect equity or
ownership interest in any other Person, other than the Subsidiaries.  Schedule
                                                                      --------
5.8 lists each Subsidiary, the jurisdiction of incorporation or formation of
---
each Subsidiary and the authorized (in the case of capital stock) and
outstanding capital stock or other equity interests of each Subsidiary.  Each
U.K. Subsidiary is duly formed and validly existing under the laws of the
jurisdiction of its formation, and each other Subsidiary is a corporation duly
organized, validly existing and in good standing under the laws of the
jurisdiction of its incorporation.  Each Subsidiary has all requisite corporate
or other, as applicable, power and authority to own, lease, and operate its
properties and to carry on its business as now being conducted.  No actions or
proceedings to dissolve any Subsidiary are pending.

          (b)  Except as otherwise indicated on Schedule 5.8, all the
                                                ------------
outstanding capital stock or other equity interests of each Subsidiary are owned
directly or indirectly by Buyer, free and clear of all Liens. All outstanding
shares of capital stock of each corporate Subsidiary have been validly issued
and are fully paid and nonassessable. All equity interests of each other
Subsidiary have been validly issued and are fully paid (to the extent required
at such time). No shares of capital stock or other equity interests of any
Subsidiary are subject to, nor have any been issued in violation of, preemptive
or similar rights.

                                       19
<PAGE>

          (c)  Except as set forth on Schedule 5.8, there are (and as of the
                                      ------------
Closing Date there will be) outstanding (i) no shares of capital stock or other
voting securities of any Subsidiary, (ii) no securities of Buyer or any
Subsidiary convertible into or exchangeable for shares of capital stock or other
voting securities of any Subsidiary, (iii) no options or other rights to acquire
from Buyer or any Subsidiary, and no obligation of Buyer or any Subsidiary to
issue or sell, any shares of capital stock or other voting securities of any
Subsidiary or any securities convertible into or exchangeable for such capital
stock or voting securities and (iv) no equity equivalents, interests in the
ownership or earnings, or other similar rights of or with respect to any
Subsidiary.  There are (and as of the Closing Date there will be) no outstanding
obligations of Buyer or any Subsidiary to repurchase, redeem or otherwise
acquire any of the foregoing shares, securities, options, equity equivalents,
interests or rights.

     Section 5.9.  Preferred Shares; Conversion Shares.
                   -----------------------------------

     (a)  The Preferred Shares, when issued under the terms of this Agreement,
will be duly authorized, validly issued and fully paid and nonassessable.
Subject to Charter Amendment Approval as it pertains to Buyer's ability to
permit the full conversion of the Preferred Shares into the Preferred Conversion
Shares, the Preferred Conversion Shares, when issued against payment of the
conversion price for such shares, will be duly authorized, validly issued and
fully paid and nonassessable.

     (b)  Subject to Charter Amendment Approval as it pertains to Buyer's
ability to permit the full conversion of the Preferred Shares into the Preferred
Conversion Shares, sufficient shares of authorized but unissued Common Stock of
Buyer will have been reserved by appropriate action in connection with the
Preferred Conversion Shares.

     (c)  Neither the issuance of the Preferred Shares, nor the issuance of
shares of Common Stock upon the conversion of the Preferred Shares, is subject
to any unwaived preemptive or other similar statutory or contractual rights or
will conflict with any provision of any agreement or instrument to which the
Company or any Subsidiary is a party or by which it is bound.

     Section 5.10.  Financial Statements.  Buyer has delivered to Seller
                    --------------------
accurate and complete copies of (i) Alliance PLC's  audited consolidated balance
sheet as of April 30, 1999, and the related audited consolidated statements of
income, stockholders' equity and cash flows for the year then ended, and the
notes and schedules thereto, together with the unqualified report thereon of
KPMG Audit Plc, independent public accountants (the "Audited Financial
Statements") and (ii)  Buyer's unaudited consolidated balance sheet as of
January 31, 2000 (the "Latest Balance Sheet"), and the related unaudited
consolidated statements of income, stockholders' equity, and cash flows for the
three-month period then ended (the "Unaudited Financial Statements"), certified
by Buyer's chief financial officer (collectively, the "Financial Statements").
The Financial Statements (i) represent actual bona fide transactions, (ii) have
been prepared from the books and records of Alliance PLC and Buyer and their
respective consolidated Subsidiaries in conformity with U.S. GAAP accounting
principles applied on a basis consistent with preceding years throughout the
periods involved and (iii) fairly present Alliance PLC's and Buyer's (as
applicable) consolidated financial position as of the respective dates thereof
and Alliance PLC's and Buyer's (as applicable) consolidated results of

                                       20
<PAGE>

operations and cash flows for the periods then ended.  The statements of income
included in the Financial Statements do not contain any items of special or
nonrecurring income except as identified in the notes thereto, and the balance
sheets included in the Financial Statements do not reflect any write-up or
revaluation increasing the book value of any assets, nor have there been any
transactions since the date of the Latest Balance Sheet giving rise to special
or nonrecurring income or any such write-up or revaluation.

     Section 5.11.  Securities Filings.  Buyer and its Subsidiaries have filed
                    ------------------
with the Securities and Exchange Commission, the London Stock Exchange and the
Registrar of Companies all forms, reports, schedules, statements and other
documents required to be filed by them since May 1, 1997 under the Companies Act
and the Listing Rules and since April 30, 1997 under the Securities Act, the
Exchange Act and all other federal securities laws.  All final forms, reports,
schedules, statements and other documents (including all amendments thereto)
filed by Buyer and its Subsidiaries with the Securities and Exchange Commission
and the London Stock Exchange since such date are herein collectively referred
to as the "SEC Filings".  Buyer has delivered or made available to Seller
accurate and complete copies of all the SEC Filings in the form filed by Buyer
and its Subsidiaries with the Securities and Exchange Commission and the London
Stock Exchange.  The SEC Filings, at the time filed, complied in all material
respects with all applicable requirements of federal securities laws.  None of
the SEC Filings, including any financial statements or schedules included
therein, at the time filed, contained any untrue statement of a material fact or
omitted to state any material fact required to be stated therein or necessary in
order to make the statements contained therein, in light of the circumstances
under which they were made, not misleading.  All material contracts of Buyer and
the Subsidiaries have been included in the SEC Filings, except for those
contracts not required to be filed pursuant to the rules and regulations of the
Securities and Exchange Commission and the London Stock Exchange.  Buyer shall
deliver to Seller as soon as they become available accurate and complete copies
of all forms, reports, and other documents furnished by it to its shareholders
generally or filed by it with the Securities and Exchange Commission and the
London Stock Exchange subsequent to the date hereof and prior to the Closing
Date.

     Section 5.12.  Absence of Undisclosed Liabilities.  Neither Buyer nor any
                    ----------------------------------
Subsidiary has any liability or obligation (whether accrued, absolute,
contingent, unliquidated, or otherwise, whether or not known to Buyer or any
Subsidiary, and whether due or to become due), except (i) liabilities reflected
on the Latest Balance Sheet, (ii) liabilities which have arisen since the date
of the Latest Balance Sheet in the ordinary course of business (none of which is
a material liability for breach of contract, breach of warranty, tort, or
infringement), (iii) liabilities arising under executory contracts entered into
in the ordinary course of business (none of which is a material liability for
breach of contract) and (iv) liabilities specifically set forth on Schedule
                                                                   --------
5.12.
----

     Section 5.13.  Absence of Certain Changes.  Except as disclosed on Schedule
                    --------------------------                          --------
5.13, since the date of the Latest Balance Sheet, (i) there has not been any
----
material adverse change in, or any event or condition that might reasonably be
expected to result in a material adverse change in, the business assets, results
of operations, condition (financial or otherwise) or prospects of Buyer and the
Subsidiaries considered as a whole; (ii) the businesses of Buyer and the
Subsidiaries have been conducted only in the ordinary course consistent with
past practice; (iii) neither Buyer nor any

                                       21
<PAGE>

Subsidiary has incurred any material liability, engaged in any material
transaction or entered into any material agreement outside the ordinary course
of business consistent with past practice; (iv) neither Buyer nor any Subsidiary
has suffered any material loss, damage, destruction, or other casualty to any of
its assets (whether or not covered by insurance); and (v) neither Buyer nor any
Subsidiary has taken any of the actions set forth in Section 6.2 except as
permitted thereunder.

     Section 5.14.  Tax Matters.  Except as disclosed on Schedule 5.14:
                    -----------                          -------------

          (a)  Buyer and each Subsidiary has filed, or has had filed on its
behalf, in a timely manner (within any applicable extension periods) with the
appropriate taxing authority all Tax Returns with respect to Taxes of Buyer and
of each of the Subsidiaries, all of which Tax Returns are true, correct and
complete in all material respects;

          (b)  All Taxes due and payable (whether or not reflected in Tax
Returns as filed) with respect to all taxable periods of Buyer and the
Subsidiaries have been paid in full or adequate reserves have been provided for
on the Financial Statements;

          (c)  There are no outstanding agreements or waivers extending the
statutory period of limitations applicable to any federal, state, local or
foreign income or other material Tax Returns required to be filed by or with
respect to Buyer or any of the Subsidiaries;

          (d)  None of the Tax Returns of or with respect to Buyer or any of the
Subsidiaries is currently being audited or examined by any taxing authority;

          (e)  No material deficiency for any Taxes has been assessed with
respect Buyer or to any of the Subsidiaries that has not either (i) been abated
or (ii) paid in full or for which adequate reserves have been provided;

          (f)  No Tax litigation is currently pending;

          (g)  No waiver or extension of any statute of limitations to any
federal, state, local or foreign Tax matter has been given by or requested from
Buyer or any Subsidiary; and

          (h)  Neither Buyer nor any Subsidiary has filed a consent under
Section 341(f) of the Code.

          (i)  Buyer and the Subsidiaries have complied with all Applicable Laws
relating to the withholding of Taxes and the payment thereof (including
withholding of Taxes under Sections 1441 and 1442 of the Code, or similar
provisions under foreign laws), and has timely and properly withheld from the
appropriate party and paid over to the proper Governmental Entity all amounts
required to be withheld and be paid over under Applicable Law.

          (j)  Neither Buyer nor any Subsidiary is required to include in income
any adjustment under Section 481(a) of the Code by reason of a change in
accounting method, and neither

                                       22
<PAGE>

Buyer nor any Subsidiary, nor the Internal Revenue Service, has proposed any
such adjustment or change in accounting method. Buyer and the Subsidiaries do
not have pending any private letter ruling with the IRS.

          (k)  Other than as a result of this transaction, none of Buyer's or
any Subsidiary's tax attributes is subject to the limitations of Section 382,
383 or 384 of the Code or Temporary Treasury Regulation Sections 1.1502-15T or
1.1502-21T(c).

          (l)  There are no liens for Taxes upon any assets of Buyer or any
Subsidiary, except liens for Taxes not yet due and payable.

          (m)  The tax basis of each of the assets of Buyer and the Subsidiaries
as set forth on the books, accounts and records of Buyer and the Subsidiaries is
true, correct and complete in all material respects.

     Section 5.15.  Environmental and Other Laws.  Except as disclosed on
                    ----------------------------
Schedule 5.15 or in the SEC Filings filed prior to the date hereof, (a) Buyer
-------------
and the Subsidiaries are conducting their businesses in compliance in all
material respects with all Applicable Laws, including all Environmental Laws,
and are in material compliance with all licenses and permits required under any
such laws; (b) to the best of Buyer's knowledge, none of the operations or
properties of Buyer or any Subsidiary is the subject of foreign, federal, state
or local investigation evaluating whether any material remedial action is needed
to respond to a release of any Hazardous Materials into the environment or to
the improper storage or disposal (including storage or disposal at offsite
locations) of any Hazardous Materials; (c) neither Buyer nor any Subsidiary has
filed any notice under any Applicable Law indicating that it is responsible for
the improper release into the environment, or the improper storage or disposal,
of any material amount of any Hazardous Materials or that any Hazardous
Materials have been improperly released, or are improperly stored or disposed
of, upon any property of Buyer or any Subsidiary; (d) neither Buyer nor any
Subsidiary has transported or arranged for the transportation of any Hazardous
Material to any location which is (i) listed on the National Priorities List
under the Comprehensive Environmental Response, Compensation and Liability Act
of 1980, as amended, listed for possible inclusion on such National Priorities
List by the Environmental Protection Agency in its Comprehensive Environmental
Response, Compensation and Liability Information System List, or listed on any
similar state list or foreign jurisdiction list or (ii) the subject of foreign,
federal, state or local enforcement actions or other investigations which may
lead to material claims against Buyer or any Subsidiary for clean-up costs,
remedial work, damages to natural resources or for personal injury claims
(whether under Environmental Laws or otherwise); and (e) to the best of Buyer's
knowledge, neither Buyer or any Subsidiary has any material contingent liability
under any Environmental Laws or in connection with the release into the
environment, or the storage or disposal, of any Hazardous Materials.

     Section 5.16.  Legal Proceedings.  Except as disclosed on Schedule 5.16,
                    -----------------                          -------------
there are no Proceedings pending or, to the best knowledge of Buyer, threatened
against or involving Buyer or any Subsidiary (or any of their respective
directors or officers in connection with the business or affairs of Buyer or any
Subsidiary) or any properties or rights of Buyer or any Subsidiary which,

                                       23
<PAGE>

individually or in the aggregate, might reasonably be expected to have a
Material Adverse Effect. Neither Buyer nor any Subsidiary is subject to any
judgment, order, writ, injunction, or decree of any Governmental Entity which
has had or is reasonably likely to have a Material Adverse Effect.  There are no
Proceedings pending or, to the best knowledge of Buyer, threatened seeking to
restrain, prohibit, or obtain damages or other relief in connection with, or
questioning the legality or validity of, this Agreement or any Ancillary
Document or the transactions contemplated hereby or thereby.

     Section 5.17.  Title to Properties; Permits; Licenses; Condition of Assets.
                    -----------------------------------------------------------

          (a)  Each of Buyer and the Subsidiaries has good and defensible title
to all of its material properties and assets, free and clear of all Liens other
than Permitted Liens and of all material impediments to the use of such
properties and assets in the businesses of Buyer and the Subsidiaries.

          (b)  Each of Buyer and the Subsidiaries holds all material Permits
necessary or required for the conduct of its business.  Each of such Permits is
in full force and effect, Buyer and the Subsidiaries are in compliance with all
of its material obligations with respect thereto, and, to the best knowledge of
Buyer, no event has occurred which allows, or with or without the giving of
notice or the passage of time or both would allow, the revocation or termination
of any thereof.  No notice has been issued by any Governmental Entity and no
proceeding is pending or, to the best knowledge of Buyer, threatened with
respect to any alleged failure by Buyer or any Subsidiary to have any material
Permit.

          (c)  Buyer and the Subsidiaries possess all licenses, permits,
franchises, patents, copyrights, trademarks and trade names, and other
intellectual property (or otherwise possesses the right to use such intellectual
property without violation of the rights of any other Person) which are
necessary to carry out their businesses as presently conducted and as presently
proposed to be conducted hereafter, and neither Buyer nor any Subsidiary is in
violation in any material respect of the terms under which it possesses such
intellectual property or the right to use such intellectual property.

          (d)  The equipment and other tangible assets of Buyer and the
Subsidiaries are in good operating condition (except for reasonable wear and
tear), and have been reasonably maintained.

     Section 5.18.  ERISA.
                    -----

          (a)  Set forth on Schedule 5.18 is a list identifying each "employee
                            -------------
benefit plan", as defined in Section 3(3) of ERISA, (i) which is subject to any
provision of ERISA, (ii) which is maintained, administered, or contributed to by
Buyer or any affiliate of Buyer, and (iii) which covers any employee or former
employee of Buyer or any affiliate of Buyer or under which Buyer or any
affiliate of Buyer has any liability.  Buyer has delivered or made available to
Seller accurate and complete copies of such plans (and, if applicable, the
related trust agreements) and all amendments thereto and written interpretations
thereof, together with (i) the three most recent annual reports (Form 5500
including, if applicable, Schedule B thereto) prepared in connection with any
such plan

                                       24
<PAGE>

and (ii) the most recent actuarial valuation report prepared in connection with
any such plan. Such plans are referred to in this Section as the "Employee
Plans". For purposes of this Section only, an "affiliate" of any person means
any other person which, together with such person, would be treated as a single
employer under Section 414 of the Code. The only Employee Plans which
individually or collectively would constitute an "employee pension benefit plan"
as defined in Section 3(2) of ERISA are identified as such on Schedule 5.18.
                                                              -------------

          (b)  Except as otherwise identified on Schedule 5.18, (i) no Employee
                                                 -------------
Plan constitutes a "multiemployer plan", as defined in Section 3(37) of ERISA
(for purposes of this Section, a "Multiemployer Plan"), (ii) no Employee Plan is
maintained in connection with any trust described in Section 501(c)(9) of the
Code, (iii) no Employee Plan is subject to Title IV of ERISA or to the minimum
funding standards of ERISA and the Code, and (iv) during the past five years,
neither Buyer nor any of its affiliates have made or been required to make
contributions to any Multiemployer Plan.  There are no accumulated funding
deficiencies as defined in Section 412 of the Code (whether or not waived) with
respect to any Employee Plan.  The fair market value of the assets held with
respect to each Employee Plan which is an employee pension benefit plan, as
defined in Section 3(2) of ERISA, exceeds the actuarially determined present
value of all benefit liabilities accrued under such Employee Plan (whether or
not vested) determined using reasonable actuarial assumptions.  Neither Buyer
nor any affiliate of Buyer has incurred any material liability under Title IV of
ERISA arising in connection with the termination of, or complete or partial
withdrawal from, any plan covered or previously covered by Title IV of ERISA.
Buyer and all of the affiliates of Buyer have paid and discharged promptly when
due all liabilities and obligations arising under ERISA or the Code of a
character which if unpaid or unperformed might result in the imposition of a
lien against any of the assets of Buyer or any Subsidiary.  Nothing done or
omitted to be done and no transaction or holding of any asset under or in
connection with any Employee Plan has or will make Buyer or any Subsidiary or
any director or officer of Buyer or any Subsidiary subject to any liability
under Title I of ERISA or liable for any Tax pursuant to Section 4975 of the
Code that could have a Material Adverse Effect.  There are no threatened or
pending claims by or on behalf of the Employee Plans, or by any participant
therein, alleging a breach or breaches of fiduciary duties or violations of
Applicable Laws which could result in liability on the part of Buyer, its
officers or directors, or such Employee Plans, under ERISA or any other
Applicable Law and there is no basis for any such claim.

          (c)  Each Employee Plan which is intended to be qualified under
Section 401(a) of the Code is so qualified and has been so qualified since the
date of its adoption, and each trust forming a part thereof is exempt from Tax
pursuant to Section 501(a) of the Code. Set forth on Schedule 5.18 is a list of
                                                     -------------
the most recent IRS determination letters with respect to any such Plans,
accurate and complete copies of which letters have been delivered or made
available to Buyer. Each Employee Plan has been maintained in compliance with
its terms and with the requirements prescribed by all Applicable Laws, including
but not limited to ERISA and the Code, which are applicable to such Employee
Plans.

          (d)  Set forth on Schedule 5.18 is a list of each employment,
                            -------------
severance, or other similar contract, arrangement, or policy and each plan or
arrangement (written or oral) providing for

                                       25
<PAGE>

insurance coverage (including any self-insured arrangements), workers'
compensation, disability benefits, supplemental unemployment benefits, vacation
benefits, retirement benefits, deferred compensation, profit-sharing, bonuses,
stock options, stock appreciation rights, or other forms of incentive
compensation or post-retirement insurance, compensation, or benefits which (i)
is not an Employee Plan, (ii) is entered into, maintained, or contributed to, as
the case may be, by Buyer or any affiliate of Buyer, and (iii) covers any
employee or former employee of Buyer or any affiliate of Buyer or under which
Buyer or any affiliate of Buyer has any liability. Such contracts, plans, and
arrangements as are described in the preceding sentence are referred to for
purposes of this Section as the "Benefit Arrangements". Each Benefit Arrangement
has been maintained in substantial compliance with its terms and with the
requirements prescribed by Applicable Laws.

          (e)  Neither Buyer nor any affiliate of Buyer has performed any act or
failed to perform any act, and there is no contract, agreement, plan, or
arrangement covering any employee or former employee of Buyer or any affiliate
of Buyer, that, individually or collectively, could give rise to the payment of
any amount that would not be deductible pursuant to the terms of Section
162(a)(1) or 280G of the Code, or could give rise to any penalty or excise Tax
pursuant to Section 4980B or 4999 of the Code.

     Section 5.19.  Agreements.
                    ----------

          (a)  Set forth on Schedule 5.19 is a list of all the following
                            -------------
agreements, arrangements, and understandings (written or oral, formal or
informal) (collectively, for purposes of this Section, "agreements") to which
Buyer or any Subsidiary is a party or by which Buyer or any Subsidiary or any of
their respective properties is otherwise bound:

               (i)   collective bargaining agreements and similar agreements
     with employees as a group;

               (ii)  agreements with any current or former shareholder,
     director, officer, employee, consultant or advisor or any affiliate of any
     such Person;

               (iii) agreements between or among Buyer and any of the
     Subsidiaries;

               (iv)  exclusive of those relating to the Senior Credit Facility,
     indentures, mortgages, security agreements, notes, loan or credit
     agreements, or other agreements relating to the borrowing of money by Buyer
     or any Subsidiary or to the direct or indirect guarantee or assumption by
     Buyer or any Subsidiary of any obligation of others, including any
     agreement that has the economic effect although not the legal form of any
     of the foregoing;

               (v)   agreements relating to the acquisition or disposition of
     assets, other than those entered into in the ordinary course of business
     consistent with past practice;

               (vi)  agreements relating to the acquisition or disposition of
     any interest in any business enterprise;

                                       26
<PAGE>

               (vii)   exclusive of oil, gas and mineral leases, agreements with
     respect to the lease of real or personal property;

               (viii)  exclusive of oil and gas operating or similar agreements,
     agreements concerning the management or operation of any real property;

               (ix)    partnership, joint venture, and profit sharing
     agreements;

               (x)     agreements with any Governmental Entity;

               (xi)    agreements relating to the release or disposal of
     Hazardous Material;

               (xii)   agreements containing any covenant limiting the freedom
     of Buyer or any Subsidiary to engage in any line of business or compete
     with any other Person in any geographic area or during any period of time,
     other than those that would not have a Material Adverse Effect;

               (xiii)  agreements not made in the ordinary course of business;
     and

               (xiv)   other agreements, whether or not made in the ordinary
     course of business, that are material to the business, assets, results of
     operations, condition (financial or otherwise), or prospects of Buyer and
     the Subsidiaries considered as a whole.

          (b)  Buyer has delivered or made available to Seller accurate and
complete copies of the agreements listed in Schedule 5.19.  Each of such
                                            -------------
agreements is a valid and binding agreement of Buyer and the Subsidiaries (to
the extent each is a party thereto) and (to the best knowledge of Buyer) the
other party or parties thereto, enforceable against Buyer and the Subsidiaries
(to the extent each is a party thereto) and (to the best knowledge of Buyer)
such other party or parties in accordance with its terms.  Neither Buyer nor any
Subsidiary is in breach of or in default under, nor has any event occurred which
(with or without the giving of notice or the passage of time or both) would
constitute a default by Buyer or any Subsidiary under, any of such agreements,
and neither Buyer nor any Subsidiary has received any notice from, or given any
notice to, any other party indicating that Buyer or any Subsidiary is in breach
of or in default under any of such agreements. To the best knowledge of Buyer,
no other party to any of such agreements is in breach of or in default under
such agreements, nor has any assertion been made by Buyer or any Subsidiary of
any such breach or default.

          (c)  Neither Buyer nor any Subsidiary has received notice of any plan
or intention of any other party to any agreement to exercise any right of offset
with respect to, or any right to cancel or terminate, any agreement, and neither
Buyer nor any Subsidiary knows of any fact or circumstance that would justify
the exercise by any such other party of such a right other than the automatic
termination of such agreement in accordance with its terms.  Neither Buyer nor
any Subsidiary currently contemplates, or has reason to believe any other Person
currently contemplates,

                                       27
<PAGE>

any amendment or change to any agreement, which amendment or change could have a
Material Adverse Effect.

          (d)  Without limiting the generality of the other provisions in this
Section 5.19, the Key Employment Agreements are in full force and effect, and
each of John Keenan and Paul Fenemore is currently employed by Buyer pursuant to
a renewal term under such agreements.

     Section 5.20.  Labor Disputes and Acts of God.  Neither the business nor
                    ------------------------------
the properties of Buyer nor any Subsidiary has been affected by any fire,
explosion, accident, strike, lockout or other labor dispute, drought, storm,
hail, earthquake, embargo, act of God or of the public enemy or other casualty
(whether or not covered by insurance), which, individually or in the aggregate,
could cause a Material Adverse Effect.

     Section 5.21.  Insurance.  Buyer and each Subsidiary carries insurance
                    ---------
covering its properties and business adequate and customary for the type and
scope of its properties and business.

     Section 5.22.  Offering of Securities.  All securities which have been
                    ----------------------
offered or sold by Buyer and it Subsidiaries have been registered pursuant to
the Securities Act and applicable foreign and state securities laws or were
offered and sold pursuant to valid exemptions therefrom.

     Section 5.23.  Government Regulation.  Buyer  is not subject to regulation
                    ---------------------
under the Public Utility Holding Company Act of 1935.  Buyer is not an
"investment company" or a company "controlled" by an "investment company" within
the meaning of the Investment Company Act of 1940, as amended, or an "investment
advisor" within the meaning of the Investment Advisers Act of 1940, as amended.

     Section 5.24.  Brokerage Fees.  Neither Buyer nor any of its affiliates has
                    --------------
retained any financial advisor, broker, agent or finder or paid or agreed to pay
any financial advisor, broker, agent or finder on account of this Agreement or
any transaction contemplated hereby, which action would subject Seller or any of
its affiliates to any liability.  Buyer shall indemnify and hold harmless Seller
from and against any and all losses, claims, damages and liabilities (including
legal and other expenses reasonably incurred in connection with investigating or
defending any claims or actions) with respect to any finder's fee, brokerage
commission or similar payment in connection with any transaction contemplated
hereby asserted by any Person on the basis of any act or statement made or
alleged to have been made by Buyer or any of its affiliates.

     Section 5.25.  Bankruptcy.  There are no bankruptcy, reorganization or
                    ----------
arrangement proceedings pending, being contemplated by, or to the knowledge of
Seller, threatened against Seller.

     Section 5.26.  Nature of Company Assets.  The assets of the Buyer and its
                    ------------------------
Subsidiaries consist solely of (a) reserves of oil, rights to reserves of oil
and associated exploration and production assets with a fair market value not
exceeding $500,000,000 and (b) other assets with a fair market value not
exceeding $15,000,000.  For purposes of this Section 5.26, the term "associated
exploration

                                       28
<PAGE>

and production assets" shall have the meaning ascribed thereto in Section 802.3
of the Rules promulgated pursuant to the HSR Act.

     Section 5.27.  Full Disclosure.  No representation or warranty made by
                    ---------------
Buyer in this Agreement, and no statement of Buyer contained in any document,
certificate or other writing furnished or to be furnished by Buyer or its
representatives to Seller pursuant hereto or in connection herewith, contains or
will contain, at the time of delivery, any untrue statement of a material fact
or omits or will omit, at the time of delivery, to state any material fact
(other than industry-wide risks normally associated with the type of business
conducted by Buyer) necessary to make the statements contained therein, in light
of the circumstances in which they are made, not misleading.  There is no fact
known to Buyer (other than industry-wide risks normally associated with the type
of business conducted by Buyer) that has not been disclosed to Seller in writing
which Buyer reasonably anticipates would result in a Material Adverse Effect.

                                   ARTICLE VI

             Certain Covenants of  Seller and Buyer Pending Closing
             ------------------------------------------------------

     Section 6.1.   Pre-Closing Covenants of Seller.
                    -------------------------------

          (a)  From the date hereof until Closing, Seller will use its
reasonable best efforts to give Buyer, and its attorneys and other
representatives, access at all reasonable times to the Properties and to any
contract files, lease or other title files, production files, well files and
other files of Seller pertaining to the ownership and/or operation of the
Properties, and Seller will use its reasonable best efforts to arrange for
Buyer, and its attorneys and other representatives, to have access to any such
files. Seller shall not be obligated to provide Buyer with access to any records
or data which Seller cannot provide to Buyer without, in its opinion, breaching
confidentiality agreements with other parties.

          (b)  Seller  will use its reasonable best efforts to (i) continue the
routine operation of the Properties in the ordinary course of business and as
would a prudent operator, (ii) operate the Properties in conformity (in all
material respects) with all applicable laws, and all applicable rules,
regulations and orders of all governmental agencies having jurisdiction, and in
conformity with all oil, gas and/or mineral leases, and in conformity (in all
material respects) with all Basic Documents other than such leases, and (iii)
fulfill all obligations (including without limitation all obligations to make
payments under leases or other Basic Documents) under such leases, and (in all
material respects) under such other Basic Documents and (in all material
respects) under such laws, rules, regulations and orders (without limitation of
the foregoing, the failure to perform an obligation, when such failure could
result in forfeiture or termination of rights of Seller under a Basic Document,
shall be considered material).

          (c)  Seller will not, without Buyer's prior consent:

                                       29
<PAGE>

               (i)    expend any funds, or make any commitments to expend funds
     (including entering into new agreements which would obligate Seller to
     expend funds), or otherwise incur any other obligations or liabilities, in
     connection with the ownership or operation of the Properties after the date
     hereof, other than routine expenses incurred in the normal operation of the
     existing wells on the Oil and Gas Properties;

               (ii)   propose the drilling of any additional wells, or propose
     the deepening, plugging back or reworking of any existing wells, or propose
     the conducting of any other operations which require consent under the
     applicable operating agreement, or propose the conducting of any other
     operations other than the normal operation of the existing wells on the Oil
     and Gas Properties, or propose the abandonment of any wells on the Oil and
     Gas Properties (and Seller agrees that it will advise Buyer of any such
     proposals made by third parties and will respond to each such proposal made
     by a third party in the manner requested by Buyer);

               (iii)  sell, transfer or abandon any portion of the Properties
     other than items of materials, supplies, machinery, equipment, improvements
     or other personal property or fixtures forming a part of the Properties
     (and then only if the same is replaced with an item of equal suitability
     and value free of liens and security interests, which replacement item will
     then, for the purposes of this Agreement, become part of the Properties);
     or

               (iv)   release (or permit to terminate), or modify or reduce its
     rights under, any oil, gas and/or mineral lease forming a part of the Oil
     and Gas Properties, or any other Basic Document, or enter into any new
     agreements which would be Basic Documents, or modify any existing
     production sales contracts or enter into any new production sales
     contracts.

          (d)  Seller will cause all expenses (including all bills for labor,
materials and supplies used or furnished for use in connection with the Property
and all severance, production, windfall profit and similar taxes) and
liabilities relating to the ownership or operation of the Properties prior to
the date of Closing to be promptly paid and discharged.

          (e)  Seller will request, from the appropriate parties (and in
accordance with the documents creating such rights and/or requirements), waivers
of the preferential rights to purchase, or requirements that consent to
assignment be obtained, which are identified in Section 6.1(e) of the Seller
Disclosure Schedule.  Seller shall have no obligation hereunder other than to so
request such waivers (i.e., Seller shall have no obligation to assure that such
waivers are obtained), and if all such waivers (or any other waivers of
preferential rights to purchase or requirements that consent be obtained to
assignment, even if the same are not listed in Section 6.1(e) of the Seller
Disclosure Schedule) are not obtained, Buyer may treat any waiver which is not
obtained as a matter which causes Seller's title to not be sufficient to meet
the standards set forth in Article VII; provided, however, that if the
unobtained waiver is a waiver of a preferential right to purchase, and if both
Buyer and Seller agree to this treatment of such matter (and agree upon an
appropriate allocation of the Purchase Price), Seller will tender (at the agreed
allocated portion of the Purchase Price) the

                                       30
<PAGE>

required interest in the Property affected by such unwaived preferential right
to purchase to the holder, or holders, of such right who have elected not to
waive such preferential right to purchase, and if, and to the extent that, such
preferential right to purchase is exercised by such party or parties, such
interest in such Property will be excluded from the transaction contemplated
hereby and the Purchase Price will be reduced by the amount paid, or to be paid,
by the party exercising such preferential right to purchase (and Seller shall
collect such amount from such purchaser).

     Section 6.2.   Pre-Closing Covenants of Buyer.
                    ------------------------------

     (a)  During the period from the date hereof to the Closing, Buyer covenants
and agrees with Seller that Buyer and its Subsidiaries (i) shall each conduct
its operations according to its ordinary course of business consistent with past
practice and in compliance with Applicable Laws; (ii) shall each use its
reasonable best efforts to preserve, maintain and protect its properties; and
(iii) shall each use its reasonable best efforts to preserve intact its business
organization, to keep available the services of its officers and employees and
to maintain existing relationships with suppliers, operators, customers and
others having business relationships with it.

     (b)  During the period from the date hereof to the Closing, neither Buyer
nor any Subsidiary shall without the prior written consent of Seller:

               (i)    amend its Organic Documents or other governing
     instruments;

               (ii)   (A) issue, sell, or deliver (whether through the issuance
     or granting of options, warrants, commitments, subscriptions, rights to
     purchase or otherwise) any shares of its capital stock of any class or any
     other securities or equity equivalents, exclusive of any shares issued
     pursuant to options, warrants, commitments, subscriptions, rights to
     purchase or otherwise existing on the date hereof); or (B) amend in any
     respect any of the terms of any such securities outstanding as of the date
     hereof;

               (iii)  (A) split, combine, or reclassify any shares of its
     capital stock; or (B) adopt a plan of complete or partial liquidation or
     resolutions providing for or authorizing a liquidation or dissolution of
     Buyer or any Subsidiary;

               (iv)   except as provided in subsection (c) below, make any
     loans, advances, or capital contributions to, or investments in, any other
     Person (other than customary loans or advances to employees in amounts not
     material to the maker of such loan or advance);

               (v)    (A) enter into, adopt, or (except as may be required by
     law) amend or terminate any bonus, profit sharing, compensation, severance,
     termination, stock option, stock appreciation right, restricted stock,
     performance unit, stock equivalent, stock purchase, pension, retirement,
     deferred compensation, employment, severance or other employee benefit
     agreement, trust, plan, fund or other arrangement for the benefit or
     welfare of any director, officer or employee; (B) except for normal
     increases in the ordinary course of business consistent with past practice
     that, in the aggregate, do not result in a material increase in

                                       31
<PAGE>

     benefits or compensation expense to Buyer, increase in any manner the
     compensation or fringe benefits of any director, officer or employee; or
     (C) pay to any director, officer or employee any benefit not required by
     any employee benefit agreement, trust, plan, fund or other arrangement as
     in effect on the date hereof;

               (vi)   make any capital expenditure or expenditures which,
     individually, is in excess of $100,000  or, in the aggregate, are in excess
     of $250,000;

               (vii)  amend any Tax Return or make any Tax election or settle or
     compromise any federal, state, local, or foreign Tax liability material to
     Buyer and the Subsidiaries considered as a whole;

               (viii) pay, discharge, or satisfy any claims, liabilities, or
     obligations (whether accrued, absolute, contingent, unliquidated, or
     otherwise, and whether asserted or unasserted), other than the payment,
     discharge, or satisfaction in the ordinary course of business consistent
     with past practice, or in accordance with their terms, of liabilities
     reflected or reserved against in the Financial Statements or incurred since
     the date of the Latest Balance Sheet in the ordinary course of business
     consistent with past practice; provided, however, that in no event shall
     Buyer or any Subsidiary repay any long-term indebtedness except to the
     extent required by the terms thereof;

               (ix)   take any action which would or might make any of the
     representations or warranties of Buyer contained in this Agreement untrue
     or inaccurate as of any time from the date of this Agreement to the Closing
     or would or might result in any of the conditions set forth in this
     Agreement not being satisfied; or

               (x)    authorize or propose, or agree in writing or otherwise to
     take, any of the actions described in this Section.

          (c)  Notwithstanding anything in this Section 6.2 to the contrary, it
is expressly agreed that the execution and delivery by Buyer of (i) the Other
Acquisition Agreements, (ii) the Preferred Stock Purchase Agreement,  (iii) the
Senior Credit Facility and (iv) the Subordinated Debt Agreement, and the
consummation of the respective transactions contemplated thereunder will not be
deemed to be a breach by Buyer of any covenant and agreement contained in this
Section 6.2 or elsewhere herein.

          (d)  Between the date hereof and the Closing, Buyer (i) shall give
Seller and its authorized representatives reasonable access, during  regular
business hours, to all employees, all plants, offices, warehouses, and other
facilities, and all books and records, including work papers and other materials
prepared by Buyer's independent public accountants, of Buyer and the
Subsidiaries, (ii) shall permit Seller and its authorized representatives to
make such inspections as they may reasonably require and (iii) shall cause
Buyer's officers and those of the Subsidiaries to furnish Seller and its
authorized representatives with such financial and operating data and other
information with respect to Buyer and the Subsidiaries as Seller may from time
to time reasonably request; provided,

                                       32
<PAGE>

however, that Buyer shall have the right to have a representative present at all
times of any such inspections, interviews and examinations conducted at or on
the offices or other facilities or properties of Buyer or its affiliates or
representatives.

     Section 6.3.  Pre-Closing Covenants of Seller and Buyer.  Each party
                   -----------------------------------------
hereto agrees that it will not voluntarily undertake any course of action
inconsistent with the provisions or intent of this Agreement and will use its
reasonable best efforts to take, or cause to be taken, all action and to do, or
cause to be done, all things reasonably necessary, proper or advisable under
Applicable Law to consummate the transactions contemplated by this Agreement.

                                  ARTICLE VII

            Due Diligence Examination With Respect to the Properties
           ---------------------------------------------------------

     Section 7.1.  Inspection and Assertion of Defects.
                   -----------------------------------

          (a)  Buyer may, to the extent it deems appropriate, conduct, at its
sole cost, such title examination or investigation as it may choose to conduct
with respect to the Properties.  Should, as a result of such examination and
investigation, or otherwise, matters come to Buyer's attention which would
constitute "Defects" (as below defined), and should there be one or more of such
Defects which Buyer determines it is unwilling to waive and close the
transaction contemplated hereby notwithstanding the fact that such Defects
exist, Buyer shall notify Seller in writing of such Defects as soon as they are
identified by Buyer, but in no event later than two business days prior to
Closing.  Such Defects of which Buyer so provides notice are herein called
"Asserted Defects." All Defects with respect to which Buyer fails to so give
Seller notice will be deemed waived for all purposes.  In the event that Buyer
notifies Seller of Asserted Defects, Seller shall have the right (but not the
obligation) to attempt to cure,  prior to Closing, such Asserted Defects to the
reasonable satisfaction of Buyer (exclusive of a Defect in subsection (b)(iii)
below.

          (b)  The term "Defect" as used in this Section shall mean the
following:

               (i)    Seller's ownership of the Properties is such that, with
     respect to a well listed in Section 7.1(b)(i) of the Seller Disclosure
     Schedule, it  (A) entitles Seller to receive a percentage share of the oil,
     gas and other hydrocarbons produced from, or allocated to, such well which
     is less than the percentage share set forth in Section 7.1(b)(i) of the
     Seller Disclosure Schedule in connection with such well in the column
     headed "NRI" or (B) causes Seller to be obligated to bear a percentage
     share of the cost of operation of such well greater than the percentage
     share set forth in  Section 7.1(b)(i) of the Seller Disclosure Schedule in
     connection with such well in the column headed "WI" (unless the share of
     production from such well to which Seller is entitled is proportionately
     larger than the "NRI" shown for such well in Section 7.1(b)(i) of the
     Seller Disclosure Schedule); or

                                       33
<PAGE>

               (ii)   Seller's ownership of an Oil and Gas Property is subject
     to a lien other than (A) a lien for taxes not yet delinquent, or (B) a
     mechanic's or materialmen's lien (or other similar lien), or a lien under
     an operating agreement or similar agreement, to the extent the same relates
     to expenses incurred which are not yet due; or

               (iii)  Seller's ownership of an Oil and Gas Property is subject
     to a preferential right to purchase such property or a requirement that
     consent to assignment of such property be obtained, unless a waiver of such
     right has been obtained with respect to the transaction contemplated hereby
     or, in the case of a preferential right to purchase, an appropriate tender
     of the applicable interest has been made to the party holding such right
     and the period of time required for such party to exercise such right has
     expired without such party exercising such right; or

               (iv)   Seller's ownership of an Oil and Gas Property is subject
     to an imperfection in title which, if asserted, would cause a Defect, as
     defined in clause (i) above, to exist, and such imperfection in title is
     not such as would normally be waived by persons engaged in the oil and gas
     business who are purchasing producing properties.

     Section 7.2.  Certain Price Adjustments.
                   -------------------------

          (a)  In the event that, as a part of the due diligence review provided
for in Section 7.1 above, Asserted Defects are presented to Seller and Seller is
unable (or unwilling) to cure such Asserted Defects, or in the event that Buyer
has elected to treat an Oil and Gas Property affected by a casualty loss as if
it was an Oil and Gas Property affected by an Asserted Defect (as provided in
Section 7.4), then Buyer and Seller shall, with respect to each Oil and Gas
Property affected by one or more Asserted Defects, attempt in good faith to
agree upon an appropriate adjustment to the Purchase Price to account for such
Asserted Defects.   Notwithstanding the foregoing or anything herein to the
contrary, Seller may elect to specify as an appropriate adjustment to the
Purchase Price for a Defect of the type specified in Section 7.1(b)(ii), the
                                                     ------------------
amount required to discharge such lien.

          (b)  Should Seller determine (or should Buyer, in the course of its
due diligence review contemplated by Section 7.1, determine) that the ownership
of the Properties by Seller entitles Seller to a share of the production from a
well listed in Section 7.1(b)(i) of the Seller Disclosure Schedule greater than
the share shown for such well under the column headed "NRI" on Schedule
7.1(b)(i) of the Seller Disclosure Schedule, then Seller may propose an upward
adjustment to the Base Purchase Price to account for such fact, in which case
such adjustment shall be handled in a similar manner as provided above with
respect to adjustments for Asserted Defects; provided that the party making such
determination shall notify the other party no later than ten business days prior
to the Closing.

          (c)  If the Net Title Adjustments (as defined below) do not exceed
$100,000, then the Base Purchase Price shall not be adjusted.  If the Net Title
Adjustments do exceed $100,000, the Base Purchase Price shall be adjusted as
provided in subsection (d) or subsection (e) below by the

                                       34
<PAGE>

amount by which the Net Title Adjustments exceed $100,000. As used in this
subsection (c), the term "Net Title Adjustments" means the net amount of the
adjustments to the Base Purchase Price resulting from the procedures provided
for above or Section 7.5 and attributable to any of the Defects referenced in
subsections (i) through (iv) of Section 7.1(b).

          (d)      Any reduction to the Base Purchase Price under subsection (c)
shall be effected by a decrease in the number of Preferred Shares equal to A
minus B, where "A" equals the number of shares of Buyer's Series A Convertible
Preferred Stock specified in Article III, where "B" equals C divided by D, where
"C" equals the Net Title Adjustments minus $100,000, and where "D" equals
$50.00.

          (e)      Any increase in the Base Purchase Price under subsection (c)
shall be effected by an increase in the number of Preferred Shares equal to A
plus B, with "A" and "B" being determined as provided in subsection (d) above.

     Section 7.3.  Waiver.  Without limiting Section 7.1 and notwithstanding
                   ------
anything else herein to the contrary, all Defects not raised by Buyer within the
time period specified in Section 7.1 shall be waived by Buyer for all purposes,
and Buyer shall have no right to seek an adjustment to the Purchase Price, make
a claim against Seller or seek indemnification from Seller with respect thereto.

     Section 7.4.  Casualty Loss.  In the event of damage by fire or other
                   -------------
casualty to the Properties after the Effective Date and prior to the Closing,
then this Agreement shall remain in full force and effect, and (unless Buyer and
Seller shall otherwise agree) in such event

          (a)      as to each such Property so damaged which is an Oil and Gas
Property, then, at Buyer's election, either (i) such Property shall be treated
as if it had an Asserted Defect associated with it and the procedure provided
for in  this Article VII shall be applicable thereto, or (ii) the Purchase Price
will not be adjusted, and if Seller should be entitled to make any claims under
any insurance policy with respect to such damage, Seller shall, at Seller's
election, either collect (and when collected pay over to Buyer), or assign to
Buyer, such claims, and

          (b)      as to each such Property which is other than an Oil and Gas
Property, Seller shall, at Seller's election, either collect (and when collected
pay over to Buyer), or assign to Buyer, any and all insurance claims relating to
such loss, and Buyer shall take title to the Property affected by such loss
without reduction of the Purchase Price.

     Section 7.5.  Disputes.
                   --------

          (a)      In the event Buyer and Seller are unable to agree upon the
existence of one or more Defects affecting an Oil and Gas Property or one or
more adjustments claimed by Buyer or Seller pursuant to this Article VII as it
relates to an Oil and Gas Property, Seller shall have the option of excluding
such Oil and Gas Property from the transaction contemplated hereby, in which
case the Purchase Price will be reduced by the amount attributed in Section
7.1(b)(i) of the Seller Disclosure Schedule to such Oil and Gas Property.

                                       35
<PAGE>

          (b)      In the event Buyer and Seller are unable to agree prior to
the Closing upon the existence of one or more Defects affecting an Oil and Gas
Property or one or more adjustments claimed by Buyer or Seller pursuant to this
Article VII as it relates to an Oil and Gas Property (and provided that Seller
does not select the option set forth in subsection (a) above with respect to
such Oil and Gas Property), any such dispute (a "Disputed Claim") shall be
settled pursuant to this Section 7.5 and shall not prevent or delay the Closing.
At Closing, the Purchase Price shall not be adjusted on account of and no effect
shall be given to the Disputed Claim. Either Buyer or Seller shall have the
right to submit the Disputed Claim to final and binding arbitration in
accordance with the Commercial Arbitration Rules of the American Arbitration
Association (the "AAA Rules"). Buyer and Seller shall endeavor to select three
neutral arbitrators by mutual agreement. If such agreement cannot be reached
within 30 calendar days after the Closing, each party shall select its own
neutral arbitrator within 15 days of the expiration of such 30-day period and
the two neutral arbitrators so selected shall select a third neutral arbitrator
within 10 days of the expiration of such 15-day period. If they fail to do so,
either arbitrator or Buyer or Seller may request the judge of the United States
District Court for the Southern District of Texas having greatest tenure, but
not yet on retired or senior status, to appoint a third neutral arbitrator. The
three persons thus selected shall be the arbitrators for such arbitration. Each
arbitrator must be experienced in and knowledgeable about the oil and gas
exploration business and third arbitrator shall be required to meet the
qualification requirements of the AAA Rules, whether appointed by the
arbitrators or by the judge as provided above. The board of arbitrators may in
all matters act through a majority of its members on each Disputed Claim if
unanimity is not attained. The award as to any Disputed Claim shall be made
within 30 days following the close of the final hearing and the filing of any
post hearing briefs authorized by the arbitrator(s) in respect of such claim.
The award of the arbitrator shall be final and binding on the parties hereto and
the subject matter. Judgment upon the award rendered by the arbitrator(s) may be
entered by any court having jurisdiction. The place of arbitration shall be in
Houston, Texas. The amount of any reduction in the Purchase Price to which Buyer
becomes entitled under the final and binding decision of the arbitrators shall
be effected in a manner similar to that set forth in Section 7.2(d). Each party
shall be entitled to inspect and obtain a copy of relevant documents in the
possession or control of the other party and to take depositions of the other
parties' employees, agents, representatives and witnesses (including expert
witnesses). All such discovery shall be in accordance with procedures approved
by the arbitrators. Unless otherwise provided in the award, each party shall
bear its own costs of discovery. All discovery shall be expedited, consistent
with the nature and complexity of the Disputed Claim and consistent with
fairness and justice. The arbitrators shall have the power to compel any party
to comply with discovery requests of the other parties and to issue binding
orders relating to any discovery dispute which shall be enforceable in the same
manner as awards. The arbitrators also shall have the power to impose sanctions
for abuse or frustration of the arbitration process, including without
limitation, the refusal to comply with orders of the arbitrators relating to
discovery and compliance with subpoenas. Each of the parties hereto hereby
irrevocably submits to the jurisdiction of the courts of the State of Texas for
entry of any arbitration decision or to obtain any preliminary relief which may
be necessary and hereby consents to the enforcement by such courts of any award
rendered in such arbitration. The compensation and expenses of the arbitrators
shall be borne equally by the parties. Each party shall bear and pay any and all
costs and expenses incurred by it in connection with the arbitration.

                                       36
<PAGE>

                                 ARTICLE VIII

            Conditions Precedent to the Obligations of the Parties
            ------------------------------------------------------

     Section 8.1.  Conditions Precedent to the Obligations of Buyer.  The
                   ------------------------------------------------
obligations of Buyer under this Agreement are subject to each of the following
conditions being met:

          (a)      All the representations and warranties of Seller contained in
this Agreement, and in any agreement, instrument or document delivered pursuant
hereto or in connection herewith on or prior to the Closing Date, shall be true
and correct in all material respects on and as of the Closing Date as if made on
and as of such date, except as affected by transactions permitted by this
Agreement, and except to the extent that any such representation or warranty is
made as of a specified date, in which case such representation or warranty shall
have been true and correct in all material respects as of such specified date.
For the sole purpose of determining whether or not any of such representations
and warranties are true and correct as aforesaid on and as of the Closing Date,
no effect shall be given to any materiality qualification contained in such
representation or warranty.

          (b)      Seller shall have performed and complied in all material
respects with (or compliance therewith shall have been waived by Buyer) each and
every covenant, agreement and condition required by this Agreement to be
performed or complied with by Seller prior to or at the Closing.

          (c)      No suit, action or other proceedings shall, on the Closing
Date, be pending or threatened before any Governmental Entity seeking to
restrain, prohibit, or obtain damages or other relief in connection with the
consummation of the transactions contemplated by this Agreement.

          (d)      There shall have been obtained any and all consents,
approvals, authorizations, licenses, orders or permits set forth on Schedule
                                                                    --------
5.7; and no other consent, approval, authorization, license, order or permit of,
---
or declaration, filing or registration with, or notification to, any
Governmental Entity, or any other Person or entity, the failure to comply with
which would have a Material Adverse Effect, shall be required to be made or
obtained by Buyer or any Subsidiary in connection with the execution, delivery
and performance of this Agreement and the consummation of the transactions
contemplated hereby.

          (e)      All waiting periods (and any extensions thereof) applicable
to this Agreement and the transactions contemplated hereby under the HSR Act
shall have expired or been terminated.

     Section 8.2.  Conditions Precedent to the Obligations of Seller.  The
                   -------------------------------------------------
obligations of Seller under this Agreement are subject to each of the following
conditions being met:

          (a)      All the representations and warranties of Buyer contained in
this Agreement, and in any agreement, instrument or document delivered pursuant
hereto or in connection herewith on or prior to the Closing Date, shall be true
and correct in all material respects on and as of the Closing Date as if made on
and as of such date, except as affected by transactions permitted by this

                                       37
<PAGE>

Agreement, and except to the extent that any such representation or warranty is
made as of a specified date, in which case such representation or warranty shall
have been true and correct in all material respects as of such specified date.
For the sole purpose of determining whether or not any of such representations
and warranties are true and correct as aforesaid on and as of the Closing Date,
no effect shall be given to any materiality qualification contained in such
representation or warranty.

          (b)      Buyer shall have performed and complied in all material
respects with (or compliance therewith shall have been waived by Seller) each
and every covenant, agreement and condition required by this Agreement to be
performed or complied with by Buyer prior to or at the Closing.

          (c)      No suit, action or other proceedings shall, on the date of
Closing, be pending or threatened before any Governmental Entity seeking to
restrain, prohibit, or obtain damages or other relief in connection with the
consummation of the transactions contemplated by this Agreement.

          (d)      The total of the net Purchase Price reductions (if any) which
result from the application of Article VII do not exceed 30% of the original
aggregate stated value of the Preferred Shares.

          (e)      All waiting periods (and any extensions thereof) applicable
to this Agreement and the transactions contemplated hereby under the HSR Act
shall have expired or been terminated.

          (f)      There shall have been obtained any and all consents,
approvals, authorizations, licenses, orders or permits set forth on Schedule
                                                                    --------
5.7; and no other consent, approval, authorization, license, order or permit of,
---
or declaration, filing or registration with, or notification to, any
Governmental Entity, or any other Person or entity, the failure to comply with
which would have a Material Adverse Effect, shall be required to be made or
obtained by Buyer or any Subsidiary in connection with the execution, delivery
and performance of this Agreement and the consummation of the transactions
contemplated hereby.

          (g)      Since the date of this Agreement, there shall not have been
any material adverse change in the business, assets, results of operations,
condition (financial or otherwise) or prospects of Buyer and the Subsidiaries
considered as a whole.

                                  ARTICLE IX

                            Closing of Transaction
                            ----------------------

     Section 9.1.  The Closing.  The closing (herein called the "Closing") of
                   -----------
the transaction contemplated hereby shall take place in the offices of Thompson
Knight Brown Parker & Leahy L.L.P.,  at Two Allen Center, Suite 3600, Houston,
Texas, at 10:00 a.m. Central Standard  Time, on May 1, 2000, or at such other
date and time  as Buyer and Seller may mutually agree upon (such date and time
being herein called the "Closing Date").

                                       38
<PAGE>

     Section 9.2.  Seller's Closing Obligations.  At the Closing, Seller shall:
                   ----------------------------

          (a)      execute, acknowledge and deliver to Buyer (or its designated
Subsidiary) an assignment of the Properties (the "Assignment"), in the form
attached hereto as Exhibit 9.2(a), effective as to runs of oil and deliveries of
                   --------------
gas as of 12:01 o'clock a.m., Central Standard Time on May 1, 2000 (the
"Effective Date");

          (b)      to the extent requested by Buyer, execute and deliver to
Buyer (i) letters in lieu of transfer orders (or similar documentation), in form
acceptable to both parties, and, (ii) an affidavit or other certification (as
permitted by such code) that Seller is not a "foreign person" within the meaning
of Section 1445 (or similar provisions) of the Internal Revenue Code of 1986 as
amended (i.e., Seller is not a non-resident alien, foreign corporation, foreign
         ----
partnership, foreign trust or foreign estate as those terms are defined in such
code and regulations promulgated thereunder); and

          (c)      deliver to Buyer such other certificates, instruments, and
documents as may be reasonably requested by Buyer prior to the Closing Date to
carry out the intent and purposes of this Agreement.

     Section 9.3.  Buyer's Closing Obligations.  At the Closing, Buyer shall:
                   ---------------------------

          (a)      deliver to Seller a stock certificate evidencing the
Preferred Shares;

         (b)       execute and deliver to Seller a certificate executed on
behalf of Buyer by an authorized signatory of Buyer, dated the Closing Date,
representing and certifying, in such detail as Seller may reasonably request,
that the conditions set forth in Sections 8.2(a) and 8.2(b) have been fulfilled;

          (c)      deliver to Seller opinions of counsel, in form, scope and
content reasonably acceptable to Seller, of Jenkens & Gilchrist, counsel to
Buyer, dated the Closing Date;

          (d)      deliver to Seller the certificates, instruments and documents
listed below:

                   (i)   certified copy of a written consent or resolutions of
     the Board of Directors of Buyer authorizing the execution, delivery and
     performance by Buyer of this Agreement and the Ancillary Documents, as
     necessary;

                   (ii)  such other certificates, instruments, and documents as
     may be reasonably requested by Seller prior to the Closing Date to carry
     out the intent and purposes of this Agreement.

     Section 9.4.  Delivery of Files.  No later than 10 business days after the
                   -----------------
Closing, Seller shall deliver to Buyer such of Seller's contract files, lease
and other title files, production files, well files and other files pertaining
to the ownership and/or operation of the Properties as Buyer may request.

                                       39
<PAGE>

                                   ARTICLE X

                            Pre-Closing Termination
                            -----------------------

     Section 10.1. Termination.  This Agreement may be terminated and the
                   -----------
transactions contemplated hereby abandoned at any time prior to the Closing in
the following manner:

          (a) by mutual written consent of Seller and Buyer;

          (b) by either Seller or Buyer if any Governmental Entity with
jurisdiction over such matters shall have issued an order or injunction
restraining, enjoining or otherwise prohibiting the consummation of the
transactions contemplated hereunder, and such order, decree, ruling or other
action shall have become final and unappealable; or

          (c) by either Seller or Buyer if the Closing shall not have occurred
on or before May 30, 2000;  provided, however, that the right to terminate this
Agreement under this Section 10.1(c) shall not be available to any party whose
failure to fulfill any obligation under this Agreement shall have been the cause
of, or shall have resulted in, the failure of the Closing to occur prior to such
date.

     Section 10.2. Effect of Termination.  In the event of termination of this
                   ---------------------
Agreement pursuant to Section 10.1 by Seller, on the one hand, or Buyer, on the
other hand, written notice thereof shall forthwith be given to the other party
specifying the provision hereof pursuant to which such termination is made, and
this Agreement shall become void and have no effect, except that the agreements
contained in this Section and in Article XVII shall survive the termination
hereof. Nothing contained in this Section shall relieve any party from liability
for damages actually incurred as a result of any breach of this Agreement.

                                  ARTICLE XI

          Certain Accounting Adjustments in Respect of the Properties
         ------------------------------------------------------------

     Section 11.1. Adjustments.  Appropriate adjustments shall be made between
                   -----------
Buyer and Seller so that (a) all expenses (including all drilling costs, all
capital expenditures, and all overhead charges under applicable operating
agreements, and all other overhead charges actually charged by third parties)
which are incurred in the operation of the Properties after the Effective Date
will be borne by Buyer, and all proceeds (net of applicable production,
severance, and similar taxes) from the sale of oil, gas and/or other minerals
produced from the Oil and Gas Properties after the Effective Date will be
received by Buyer, and (b) all expenses which are incurred in the operation of
the Properties before the Effective Date will be borne by Seller and all
proceeds (net of applicable production, severance, and similar taxes) from the
sale of oil, gas and/or other minerals produced therefrom before the Effective
Date will be received by Seller.  It is agreed that, in making such adjustments:
(i) oil which was produced from the Oil and Gas Properties and which was, on the
Effective Date, stored in tanks located on the Oil and Gas Properties (or
located elsewhere but used

                                       40
<PAGE>

to store oil produced from the Oil and Gas Properties prior to delivery to oil
purchasers) and above pipeline connections shall be deemed to have been produced
before the Effective Date (it is recognized that such tanks were not gauged on
the Effective Date for the purposes of this Agreement and that determination of
the volume of such oil in storage will be based on the best available data,
which may include estimates), and (ii) ad valorem taxes assessed with respect to
a period which the Effective Date splits shall be prorated based on the number
of days in such period which fall on each side of the Effective Date (with the
day on which the Effective Date falls being counted in the period after the
Effective Date), and (iii) no consideration shall be given to the local, state
or federal income tax liabilities of any party.

     Section 11.2. Closing and Post-Closing Accounting Settlements.
                   -----------------------------------------------

          (a) At or before Closing, the parties shall determine, based upon the
best information reasonably available to them, the amount of the adjustments
provided for in Section 11.1.  If the amount of adjustments so determined which
would result in a credit to Buyer exceed the amount of adjustments so determined
which would result in a credit to Seller, Buyer shall receive a credit, for the
amount of such excess, against the number of Preferred Shares to be delivered at
Closing, and, if the converse is true, Buyer shall increase the number of
Preferred Shares delivered to Seller, at Closing (in addition to amounts
otherwise then owed), for the amount of such excess, in each case determined on
the basis of one Preferred Share for each $50 of adjustment.

          (b) On or before 90 days after Closing, Buyer and Seller shall review
any additional information which may then be available pertaining to the
adjustments provided for in Sections 11.1, shall determine if any additional
adjustments (whether the same be made to account for expenses or revenues not
considered in making the adjustments made at Closing, or to correct errors made
in such adjustments) should be made beyond those made at Closing, and shall make
any such adjustments in the manner provided in subsection (a) above.  Following
such additional adjustments, no further adjustments shall be made under this
Article XI.

                                  ARTICLE XII

                        Assumption and Indemnification
                        -------------------------------

     Subject to Article VII,  Section 11.2(b), the last sentence of this Article
XII and the other terms and provisions hereof, Seller shall, on the date of
Closing, agree (and, upon the delivery to Buyer of the Assignment, shall be
deemed to have agreed) to indemnify and hold Buyer harmless from and against any
and all claims, obligations, actions, liabilities, damages, or expenses arising
out of the ownership or operation of the Properties before the Effective Date
(exclusive of Environmental Obligations other than Excluded Environmental
Obligations).  Buyer shall, on the date of Closing, agree (and, upon the receipt
by Buyer of the Assignment from Seller, shall be deemed to have agreed) to (a)
assume, and to timely pay and perform all duties, obligations and liabilities
relating to the ownership or operation of the Properties after the Effective
Date (including those arising under the contracts and agreements described in
Article II(d)) and (b) assume full responsibility for Environmental Obligations
other than the Excluded Environmental Obligations. Buyer shall, on the

                                       41
<PAGE>

date of Closing, agree (and upon the receipt by Buyer of the Assignment from
Seller shall be deemed to have agreed) to indemnify and hold Seller harmless
from and against (i) any and all claims, obligations, actions, liabilities,
damages, or expenses arising out of the ownership or operation of the Properties
after the Effective Date and (ii) any Environmental Obligations other than the
Excluded Environmental Obligations.. In connection with (but not in limitation
of) the foregoing, it is specifically understood and agreed that matters arising
out of or otherwise relating to the ownership and/or operation of the Properties
after the Effective Date shall include all obligations to properly plug and
abandon, or replug and re-abandon, wells located on the Properties; it is
further understood and agreed that Seller shall have no liability to Buyer or
obligation to indemnify Buyer for any matter for which Buyer has received an
adjustment to the Base Purchase Price under this Agreement.

                                 ARTICLE XIII

                  Affirmative Post Closing Covenants of Buyer
                 --------------------------------------------

     To induce Seller to enter into this Agreement, Buyer warrants, covenants
and agrees  that it will comply with and observe the following covenants and
provisions, and will cause each Subsidiary to comply with and observe such of
the following covenants and provisions as are applicable to such Subsidiary:

     Section 13.1. Inspection Rights.  At any reasonable time and from time to
                   -----------------
time upon reasonable notice, Buyer will permit Seller or its agents or
representatives to examine and make copies of and extracts from the records and
books of account of, and visit and inspect the properties of Buyer and any
Subsidiary, and to discuss the affairs, finances and accounts of Buyer and any
Subsidiary with any of their officers or directors and independent accountants.

     Section 13.2. Books, Financial Statements and Reports.  Buyer and each of
                   ---------------------------------------
its Subsidiaries will at all times maintain full and accurate books of account
and records.  Buyer will maintain and will cause its Subsidiaries to maintain a
standard system of accounting, will maintain its Fiscal Year, and will furnish
the following statements and reports to Seller at Buyer's expense:

          (a)      As soon as available, and in any event within one hundred
five (105) days after the end of each Fiscal Year, complete consolidated
financial statements of Buyer together with all notes thereto, prepared in
reasonable detail in accordance with U.S. GAAP, together with an unqualified
opinion, based on an audit using generally accepted auditing standards, by
independent certified public accountants selected by Buyer and reasonably
acceptable to Seller, stating that such consolidated financial statements have
been so prepared. These financial statements shall contain a consolidated
balance sheet as of the end of such Fiscal Year and consolidated statements of
earnings, of cash flows, and of changes in owners' equity for such Fiscal Year,
each setting forth in comparative form the corresponding figures for the
preceding Fiscal Year.

          (b)      As soon as available, and in any event within fifty (50) days
after the end of each Fiscal Quarter, Buyer's consolidated  balance sheet as of
the end of such Fiscal Quarter and consolidated statements of Buyer's earnings
and cash flows for the period from the beginning of the

                                       42
<PAGE>

then current Fiscal Year to the end of such Fiscal Quarter, all in reasonable
detail and prepared in accordance with U.S. GAAP, subject to changes resulting
from normal year-end adjustments. In addition Buyer will, together with each
such set of financial statements and each set of financial statements furnished
under subsection (a) of this section, furnish a certificate in a form reasonably
acceptable to Seller signed by the chief financial officer of Buyer stating that
such financial statements are accurate and complete (subject to normal year-end
adjustments) and stating that no Default exists at the end of such Fiscal
Quarter or at the time of such certificate or specifying the nature and period
of existence of any such Default.

          (c) Promptly upon their becoming available, copies of all financial
statements, reports, notices and proxy statements sent by Buyer to its
stockholders and all registration statements, periodic reports and other
statements and schedules filed by Buyer with any securities exchange, the
Securities and Exchange Commission or any similar Governmental Entity.

          (d) Annually within 60 days after the end of each Fiscal Year
beginning with the Fiscal Year ending April 30, 2000, a report containing (i) an
estimation of the oil and gas reserves, classified by appropriate categories, as
of the end of the preceding fiscal year attributable to the interest of Buyer
therein, (ii) a projection of the rate of production of and net income from such
reserves with respect to each such interest, (iii) a calculation of the present
worth of such net income discounted at a rate of 10% and (iv) a schedule or
complete description of all assumptions, estimates and projections made or used
in the preparation of such report.  Each such report shall be prepared in
accordance with customary and generally accepted standards and practices for
petroleum engineers, and shall be based on (1) prices determined  by the Holders
of a Requisite Majority , (2) lease operating expenses and production taxes
derived from and consistent with those actually incurred by Buyer, escalated at
the same rate, if any, being applied to prices and (3) such other assumptions as
shall be designated by the Holders of a Requisite Majority.  In addition to the
foregoing, the Holders of a Requisite Majority shall have the right from time to
time to cause the independent petroleum engineer referenced below to prepare an
additional report of the type described above, not to exceed one additional
report in any one calendar year, in which event all fees and expenses incurred
in connection with obtaining such additional report shall be paid by Buyer. Each
report under this subsection shall be prepared by an independent petroleum
engineer designated by Buyer and approved by the Holders of a Requisite
Majority.  Each annual report referenced above shall also include an estimate of
Buyer's proved oil and gas reserves (as defined in Regulation S-X promulgated by
the Securities and Exchange Commission) and a calculation of the "present value
of estimated future net revenues" from such proved oil and gas reserves, with
such present worth calculation to be made in accordance with Regulation S-X, as
promulgated by the Securities and Exchange Commission.

          (e) Promptly, such other information with respect to the business and
operations of Buyer and its Subsidiaries, as Seller may reasonably request.

     Section 13.3. Notice of Material Events and Change of Address.  Buyer will
                   -----------------------------------------------
promptly notify Seller in writing, stating that such notice is being given
pursuant to this Agreement, of:

                                       43
<PAGE>

          (a) the occurrence of an event or circumstance that could reasonably
be expected to have a  Material Adverse Effect,

          (b)  the occurrence of any Default,

          (c) the acceleration of the maturity of any indebtedness owed by Buyer
or any Subsidiary thereof or of any default by any Buyer or any such Subsidiary
under any indenture, mortgage, agreement, contract or other instrument to which
any of them is a party or by which any of them or any of their properties is
bound, if such acceleration or default could reasonably be expected to have a
Material Adverse Effect,

          (d) any claim of $100,000 or more, any notice of potential liability
under any Environmental Laws which might exceed such amount, or any other
material adverse claim asserted against Buyer or any Subsidiary thereof or with
respect to Buyer or any of such Subsidiary's properties, and

          (e) the filing of any suit or proceeding against Buyer or any
Subsidiary thereof in which an adverse decision could cause a Material Adverse
Effect.

Upon the occurrence of any of the foregoing Buyer and any Subsidiary thereof
will take all necessary or appropriate steps to remedy promptly any such
Material Adverse Effect, Default, acceleration or default, to protect against
any such adverse claim, to defend any such suit or proceeding, and to resolve
all controversies on account of any of the foregoing.

     Section 13.4. Maintenance of Properties.  Buyer and each of its
                   -------------------------
Subsidiaries will maintain, preserve, protect, and keep all property used or
useful in the conduct of its business in good condition and in compliance with
all Applicable Laws, and will from time to time make all repairs, renewals and
replacements needed to enable the business and operations carried on in
connection therewith to be promptly and advantageously conducted at all times.

     Section 13.5. Maintenance of Existence and Qualifications.  Buyer and each
                   -------------------------------------------
of its Subsidiaries will maintain and preserve its existence and its rights and
franchises in full force and effect and will qualify to do business in all
states or jurisdictions where required by Applicable Law, except where the
failure so to qualify will not cause a Material Adverse Effect.

     Section 13.6. Payment of Trade Liabilities, Taxes, etc.  Buyer and each of
                   -----------------------------------------
its Subsidiaries will (a) timely file all required Tax Returns; (b) timely pay
all Taxes, assessments, and other governmental charges or levies imposed upon it
or upon its income, profits or property; (c) timely withhold and pay over to the
proper Governmental Entity all amounts required to be withheld and paid over
under Applicable Laws; (d) pay when due all Liabilities owed by it on ordinary
trade terms to vendors, suppliers and other Persons providing goods and services
used by it in the ordinary course of its business; (e) pay and discharge when
due all other Liabilities now or hereafter owed by it; and (f) maintain
appropriate accruals and reserves for all of the foregoing in accordance with
U.S. GAAP.  Buyer and each of its Subsidiaries may, however, delay paying or
discharging any of the foregoing

                                       44
<PAGE>

so long as it is in good faith contesting the validity thereof by appropriate
proceedings and has set aside on its books adequate reserves therefor.

     Section 13.7. Insurance.  Buyer and each of its Subsidiaries will keep or
                   ---------
cause to be kept insured by financially sound and reputable insurers its
properties in such forms and amounts and against such risks as are customary for
Persons engaged in the same or similar business of owning and operating similar
properties.

     Section 13.8. Compliance with Agreements and Law.  Buyer and each of its
                   ----------------------------------
Subsidiaries will perform all material obligations it is required to perform
under the terms of each indenture, mortgage, deed of trust, security agreement,
lease, franchise, agreement, contract or other instrument or obligation to which
it is a party or by which it or any of its properties is bound.  Buyer and each
of its Subsidiaries will conduct its business and affairs in compliance with all
Applicable Law.

     Section 13.9. Charter Amendment Approval.  Buyer shall cause Charter
                   --------------------------
Amendment Approval  by September 30, 2000.

                                 ARTICLE XIV

                   Post Closing Negative Covenants of Buyer
                   ----------------------------------------

     To induce Seller to enter into this Agreement, Buyer warrants, covenants
and agrees  that, until all of the Preferred Shares have been converted into
Preferred Conversion Shares, it will comply with and observe the following
covenants and provisions, and will cause each Subsidiary to comply with and
observe such of the following covenants and provisions as are applicable to such
Subsidiary:

     Section 14.1. Indebtedness.  Neither Buyer nor any Subsidiary thereof will
                   ------------
in any manner owe or be liable for Indebtedness except:

          (a)  the Senior Credit Facility;

          (b)  the Subordinated Debt;

          (c)  purchase money Indebtedness and Indebtedness under leases of
Buyer or such Subsidiary as lessee which are capitalized in accordance with U.S.
GAAP, in an aggregate principal amount not to exceed $100,000 at any time,
provided that such purchase money Indebtedness and Indebtedness under capital
leases do not in the aggregate exceed $250,000;

          (d)  gas overproduction or liabilities arising under futures
contracts, forward contracts, swap, cap or collar contracts, option contracts,
hedging contracts, other derivative contracts or similar contracts, to the
extent permitted by the Senior Credit Facility;

          (e)  Old Latex Payables.

                                       45
<PAGE>

     Section 14.2. Limitation on Liens.  Neither Buyer nor any Subsidiary
                   -------------------
thereof will create, assume or permit to exist any Lien upon any of the
properties or assets which it now owns or hereafter acquires, except the
following ("Permitted Liens"):

          (a) Liens which secure the Senior Credit Facility; and

          (b) Statutory Liens for taxes, statutory mechanics' and materialmen's
Liens incurred in the ordinary course of business, and other similar Liens
incurred in the ordinary course of business, provided such Liens do not secure
Indebtedness and secure only Indebtedness which is not delinquent or for which
adequate reserves have been set aside.

     Section 14.3. Limitation on Mergers.  Except as expressly provided in this
                   ---------------------
Section, neither Buyer nor any Subsidiary thereof will merge or consolidate with
or into any other business entity. Any Subsidiary of Buyer may, however, be
merged into or consolidated with either Buyer or another Subsidiary which is
wholly-owned by Buyer, so long as Buyer or the Subsidiary wholly-owned by Buyer
is the surviving business entity. Buyer will not issue any securities other than
(i) Common Stock (including the shares of Common Stock to be issued upon the
conversion of the Series A Preferred)  or (ii) any options or warrants giving
the holders thereof only the right to acquire such shares.  No Subsidiary of
Buyer will issue any additional shares of its capital stock or other securities
or any options, warrants or other rights to acquire such additional shares or
other securities except to Buyer or to another Subsidiary.  No Subsidiary of
Buyer which is a partnership will allow any diminution of Buyer's interest
(direct or indirect)  therein.

     Section 14.4. Limitation on Sales of Property.  Neither Buyer nor any
                   -------------------------------
Subsidiary thereof will sell, transfer, lease, exchange, alienate or dispose of
any of its assets or properties except:

          (a) equipment which is worthless or obsolete or which is replaced by
equipment of equal suitability and value;

          (b) inventory (including oil and gas sold as produced and seismic
data) which is sold in the ordinary course of business on ordinary trade terms;
or

          (c) other property which is sold for fair consideration not in the
aggregate in excess of $500,000 in any Fiscal Year (commencing with Fiscal Year
2000).

     Section 14.5. Limitation on Investments and New Businesses.  Neither Buyer
                   --------------------------------------------
nor any Subsidiary thereof will make any expenditure or commitment or incur any
obligation or enter into or engage in any transaction except in the ordinary
course of business (which ordinary course of business includes the acquisition,
directly or indirectly, of oil and gas properties), engage directly or
indirectly in any business or conduct any operations except in connection with
or incidental to its present businesses and operations, make any acquisitions of
or capital contributions to or other investments in any Person, other than
Permitted Investments, or  make any significant acquisitions or investments in
any properties other than oil and gas properties.

                                       46
<PAGE>

      Section 14.6. Transactions with Affiliates.  Neither Buyer nor any of its
                    ----------------------------
Subsidiaries will engage in any material transaction with any of its affiliates
on terms which are less favorable to it than those which would have been
obtainable at the time in arm's-length dealing with Persons other than such
affiliates.

      Section 14.7. Restricted Payments.  Buyer will not, and will not permit
                    -------------------
any of its Subsidiaries to, declare or make, or incur any liability to declare
or make, any Restricted Payment.

                                  ARTICLE XV

                        Events of Default and Remedies
                        ------------------------------

      Section 15.1. Events of Default. If any of the following events ("Events
                    -----------------
of Default") shall occur and be continuing:

          (a)  Buyer fails to pay any dividends on the Preferred Shares when due
as required under the terms of the Certificate of Designation;

          (b)  Buyer fails to redeem the Preferred Shares when due as required
under the terms of the Certificate of Designation;

          (c)  a default in the performance or observation of any covenant,
agreement or condition contained in (i) Article XIII or Article XIV, (ii) the
Organic Documents with respect to the Series A Preferred (exclusive of a default
described in subsection (a) or subsection (b) above, or (iii) any other
Ancillary Document, which default is not remedied within 15 days after the
earlier of (A) the day on which Buyer first obtains knowledge of such default or
(B) the day on which written notice thereof is given to Buyer by any registered
holder of the Preferred Shares;

         (d)  any representation or warranty previously, presently or hereafter
made in writing by or on behalf of Buyer or any Subsidiary thereof  in
connection with this Agreement or any Ancillary Document shall prove to have
been false or incorrect in any material respect on any date on or as of which
made, which default is not remedied within 30 days after the earlier of (i) the
day on which Buyer first obtains knowledge of such default or (ii) the day on
which written notice thereof is given to Buyer by any registered  holder of the
Preferred Shares;

          (e)  Buyer or any Subsidiary fails to duly observe, perform or comply
with any term or condition of any loan document relating to the Senior Credit
Facility, the Subordinated Debt Agreement or any other agreement or instrument
with any Person, if such agreement or instrument is materially significant to
Buyer or such Subsidiary, and such failure is not remedied within the applicable
period of grace (if any) provided in such agreement or instrument (it being
agreed that each of the Other Acquisition Agreements and the Preferred Stock
Purchase Agreement is materially significant to Buyer);

                                       47
<PAGE>

          (f)  Buyer or any Subsidiary thereof fails to pay any portion, when
such portion is due, of any of its Indebtedness in excess of $100,000 (exclusive
of the Old LaTex Payables), or breaches or defaults in the performance of any
Agreement or instrument by which any such Indebtedness is issued, evidenced,
governed, or secured, and any such failure, breach or default continues beyond
any applicable period of grace provided therefor;

          (g)  Buyer or any Subsidiary thereof:

               (i)   suffers the entry against it of a judgment, decree or order
     for relief by a tribunal of competent jurisdiction in an involuntary
     proceeding commenced under any applicable bankruptcy, insolvency or other
     similar Applicable Law of any jurisdiction now or hereafter in effect,
     including the United States federal Bankruptcy Code or similar foreign law,
     as from time to time amended, or has any such proceeding commenced against
     it which remains undismissed for a period of thirty days; or

               (ii)  commences a voluntary case under any applicable bankruptcy,
     insolvency or similar Applicable Law now or hereafter in effect, including
     the United States federal Bankruptcy Code or similar foreign law, as from
     time to time amended; or applies for or consents to the entry of an order
     for relief in an involuntary case under any such Applicable Law; or makes a
     general assignment for the benefit of creditors; or fails generally to pay
     (or admits in writing its inability to pay) its debts as such debts become
     due; or takes corporate or other action to authorize any of the foregoing;
     or

               (iii) suffers the appointment of or taking possession by a
     receiver, liquidator, assignee, custodian, trustee, sequestrator or similar
     official of all or a substantial part of its assets in a proceeding brought
     against or initiated by it, and such appointment or taking possession is
     neither made ineffective nor discharged within thirty days after the making
     thereof, or such appointment or taking possession is at any time consented
     to, requested by, or acquiesced to by it; or

               (iv)  suffers the entry against it of a final judgment for the
     payment of money in excess of $250,000 (not covered by insurance), unless
     the same is discharged within thirty days after the date of entry thereof
     or an appeal or appropriate proceeding for review thereof is taken within
     such period and a stay of execution pending such appeal is obtained; or

               (v)   suffers a writ or warrant of attachment or any similar
     process to be issued by any tribunal against all or any substantial part of
     its assets, and such writ or warrant of attachment or any similar process
     is not stayed or released within thirty days after the entry or levy
     thereof or after any stay is vacated or set aside;

          (h)  Any Change in Control occurs; and

          (i)  Any Material Adverse Effect occurs.

                                       48
<PAGE>

     Upon the occurrence of an Event of Default, (x) Seller or any other holder
of the Preferred Shares holding a majority of the Outstanding Common Stock may,
by notice to the Company, request that Buyer redeem all of the Preferred Shares
at a per share purchase price of $50.00 plus all accrued and unpaid dividends
thereon; (y) Seller shall have such rights as provided in the Organic Documents;
and (z) Seller may proceed to protect and enforce its rights by suit in equity
(including a suit for recission), action at law or other appropriate proceeding
either for specific performance of any covenant, provision or condition
contained or incorporated by reference to this Agreement or in aid of the
exercise of any power granted in this Agreement.

     Without limiting the rights of the holders of the Series A Preferred, Buyer
and the Subsidiaries  hereby agree that the holders of the Series A Preferred
would have no adequate remedy at law, for monetary compensation or otherwise,
for the damages that would be suffered if Buyer or the Subsidiaries were to fail
to comply with its obligations under Article IX, and that Buyer and the
Subsidiaries therefore agree that the holders of the Series A Preferred shall be
entitled to obtain specific performance of Buyer's obligations under this
Agreement.

      Section 15.2. Annulment of Defaults.  Section 15.1 is subject to the
                    ---------------------
condition that if, at any time after a dividend shall have become due and
payable, and before any judgment or decree for the payment of the moneys so due,
or any thereof, shall have been entered, then and in every such case Seller may,
by written instrument filed with Buyer, rescind and annul such declaration and
its consequences; but no such recission or annulment shall extend to or affect
and subsequent default or Event of Default or impair any right consequent
thereon.

      Section 15.3. Expiration.  The provisions of Sections 15.1 and 15.2 shall
                    ----------
automatically expire and be of no further force or effect upon such date as all
of the Preferred Shares have been converted into Preferred Conversion Shares.

                                  ARTICLE XVI

                                    Notices
                                    -------

     All notices, requests, demands, and other communications required or
permitted to be given or made hereunder by any party hereto shall be in writing
and shall be deemed to have been duly given or made if (i) delivered personally,
(ii) transmitted by first class registered or certified mail, postage prepaid,
return receipt requested, (iii) sent by prepaid overnight courier service, or
(iv) sent by telecopy or facsimile transmission, answer back requested, to the
parties at the following addresses (or at such other addresses as shall be
specified by the parties by like notice):

                                       49
<PAGE>

     If to Seller:       Mountaineer Limited Partnership
     ------------
                         207 West McKay
                         Carlsbad, New Mexico 88220
                         Attention: Perry L. Hughes

     with a copy to:     c/o EnCap Investments L.L.C.
     --------------
                         1100 Louisiana, Suite 3150
                         Houston, Texas 77002
                         Attention: Robert L. Zorich
                         Fax No.: 713-659-6130

     If to Buyer:        AROC Inc.
     -----------
                         4200 East Skelly Drive, Suite 1000
                         Tulsa, Oklahoma 74135
                         Attention: John A. Keenan
                         Fax No.: 918-494-4918

     with a copy to:     Jenkens & Gilchrist, a Professional Corporation
                         1445 Ross Avenue, Suite 3200
                         Dallas, Texas 75202
                         Attention: W. Alan Kailer
                         Fax No.: 214-855-4300

Such notices, requests, demands, and other communications shall be effective (i)
if delivered personally or sent by courier service, upon actual receipt by the
intended recipient, (ii) if mailed, upon the earlier of five days after deposit
in the mail or the date of delivery as shown by the return receipt therefor or
(iii) if sent by telecopy or facsimile transmission, when the answer back is
received.

                                 ARTICLE XVII

                             Miscellaneous Matters
                             ---------------------

      Section 17.1. Survival of Provisions.
                    ----------------------

          (a)  All representations and warranties made herein by Buyer and
Seller shall be continuing and shall be true and correct on and as of the date
of Closing with the same force and effect as if made at that time and, except as
provided below, all of such representations and warranties shall survive the
Closing and the delivery of the Assignment. The representations of Seller
contained in Section 4.7 through 4.20 (the "Limited Survival Representations")
shall survive the Closing until the six-month anniversary of the Closing (the
"Survival Date"). The provisions of, and the obligations of the parties under,
Article IX (to the extent the same are, by mutual agreement, not performed at
Closing), Section 6.4 and Articles X through XVII inclusive shall survive the
Closing and the delivery of the Assignment.

                                       50
<PAGE>

          (b)  Seller shall not have any indemnification obligation pursuant to
Section 17.5(b) or otherwise in respect of any Limited Survival Representation
unless before the Survival Date it shall have received from Buyer written notice
of the existence of the claim for or in respect of which indemnification in
respect of such Limited Survival Representation is sought.  Such notice shall
set forth with reasonable specificity (i) the basis under this Agreement, and
the facts that otherwise form the basis, of such claim, (ii) an estimate of the
amount of such claim (which estimate shall not be conclusive of the final amount
of such claim) and an explanation of the calculation of such estimate, including
a statement of any significant assumptions employed therein, and (iii) the date
on and manner in which Buyer became aware of the existence of such claim.

      Section 17.2. Public Announcements.  Except as may be required by
                    --------------------
Applicable Law, neither Seller, on the one hand, nor Buyer, on the other, shall
issue any press release or otherwise make any public statement with respect to
this Agreement or the transactions contemplated hereby without the prior written
consent of the other party (which consent shall not be unreasonably withheld).
Any such press release or public statement required by Applicable Law shall only
be made after reasonable notice to the other party, and in such case the party
proposing to make such a press release or public statement shall consult with
the other party.

      Section 17.3. Fees and Expenses.
                    -----------------

          (a)  Except as otherwise expressly provided in this Agreement, all
fees and expense, including fees and expenses of counsel, incurred in connection
with this Agreement and the transactions contemplated hereby shall be paid by
the party incurring such fee or expense.

          (b)  Notwithstanding anything to the contrary herein, since the
transaction contemplated hereby is an isolated transaction, no sales tax will be
collected from Buyer.  If, however, this transaction is later deemed to be other
than an occasional sale, Buyer agrees to be solely responsible, and shall
indemnify and hold Seller (and their respective partners, and each of their and
each such partners' parent and subsidiary companies and other affiliates, and
shareholders, managers, owners, directors, officers, employees, consultants, and
agents, respectively) harmless, from any and all sales or transfer taxes or fees
(including related penalty, interest or legal costs) due by virtue of this
transaction on the Properties transferred pursuant hereto and Buyer shall remit
such sales or transfer taxes at that time.  Seller and Buyer agree to cooperate
with each other in demonstrating that the requirements for an occasional or
isolated sale or any other sales tax exemption have been met.

          (c)  Buyer shall be solely responsible for all filings and recordings
of assignments and other documents related to the Properties and for all fees
connected therewith, and Buyer shall furnish Seller with pertinent recording
data.  Seller shall not be responsible for any loss to Buyer because of Buyer's
failure to file or record documents correctly or promptly.

          (d)  All sales, transfer, filing, recordation, registration, stamp and
similar Taxes and fees arising from or associated with the issue and sale of the
Preferred Shares contemplated hereunder, whether levied on Seller or Buyer,
shall be borne by Buyer, and Buyer shall file all

                                       51
<PAGE>

necessary documentation with respect to, and make all payments of, such Taxes
and fees on a timely basis.

      Section 17.4. Costs of Enforcement.  If any party hereto is required to
                    --------------------
take action to enforce its rights under this Agreement, the prevailing party
shall be entitled to its reasonable expenses, including attorneys' fees and
expenses, in connection with any such action.

      Section 17.5. Indemnification.
                    ---------------

          (a)  Subject to the terms and conditions of this Section 17.5, Buyer
shall indemnify, defend and hold harmless Seller from and against any and all
claims, actions, causes of action, demands, assessments, losses, damages,
liabilities, judgments, settlements, penalties, costs and expenses (including
reasonable attorneys' fees and expenses), of any nature (collectively,
"Damages") whatsoever, asserted against, resulting to, imposed upon, or incurred
by Seller, directly or indirectly, by reason of or resulting from any breach by
Buyer of any of its representations, warranties, covenants or agreements
contained in this Agreement or in any certificate, instrument or document
delivered pursuant hereto.

          (b)  Subject to the terms and conditions of this Section 17.5 (and
Section 17.1(b)), Seller shall indemnify, defend and hold harmless Buyer from
and against any and all Damages, asserted against, resulting to, imposed upon,
or incurred by Buyer, directly or indirectly, by reason of or resulting from any
breach by Seller of any of its representations, warranties, covenants or
agreements contained in this Agreement or in any certificate, instrument or
document delivered pursuant hereto (collectively, "Buyer Claims").

          (c)  No indemnification shall be required to be made by Seller
pursuant to this Section 17.5 with respect to any Buyer Claims except to the
extent that the aggregate amount of Damages incurred by Buyer with respect to
all Buyer Claims exceeds $50,000.

          (d)  Seller's liability to Buyer for indemnification pursuant to this
Section 17.5 or elsewhere in this Agreement (including Article XII) shall in no
event exceed the aggregate stated value of the Preferred Shares issued to
Seller; further, the sole manner by which Seller shall be required to satisfy
any indemnification obligation to Buyer pursuant to this Section 17.5 or
elsewhere in this Agreement, including Article XII (in this subsection, an
"Indemnification Obligation") shall be by Seller tendering to Buyer either
Preferred Shares or Preferred Conversion Shares. In connection therewith, (i)
the number of Preferred Shares to be tendered shall be equal to the
Indemnification Obligation (or portion thereof to be satisfied with Preferred
Shares) divided by the greater of (A) $50.00 or (B) the aggregate Current Market
Price of the shares of Common Stock into which such Preferred Shares are then
convertible divided by the number of Preferred Shares to be tendered; and (ii)
the number of Preferred Conversion Shares to be tendered shall be equal to the
Indemnification Obligation (or portion thereof to be satisfied with Preferred
Conversion Shares) divided by the Current Market Price. As used herein, the term
"Current Market Price" shall mean the average of the last reported sales prices
for the Common Stock for the 10 consecutive Trading Days ending on the second
Trading Day prior to delivery in satisfaction of the subject Indemnification
Obligation.

                                       52
<PAGE>

The last reported sales price for each day shall be the last reported sales
price of the Common Stock on such date on the exchange where it is primarily
traded, or, if the Common Stock is not traded on an exchange, the Common Stock
shall be valued at the last reported sales price on such date on the NASDAQ
National Market System, or, if the Common Stock is not traded on the NASDAQ
National Market System or any similar system of automated dissemination of
quotations of securities prices, the Common Stock shall be valued at the closing
bid price (or average of bid prices) last quoted on such date as reported on an
established quotation service for over-the-counter securities. As used in this
subsection (d), the term "Trading Days" shall mean (1) if the Common Stock is
listed or admitted for trading on any generally recognized U.S. securities
exchange, days on which such securities exchange is open for business and (2) if
the Common Stock is quoted on the NASDAQ National Market System or any similar
system of automated dissemination of quotations of securities prices, days on
which trades may be made on such system.

          (e)  Promptly after receipt by an indemnified party under Section
17.5(a) or Section 17.5(b) of notice of the commencement of any action, such
indemnified party shall, if a claim in respect thereof is to be made against an
indemnifying party under such Section, give written notice to the indemnifying
party of the commencement thereof , but the failure so to notify the
indemnifying party shall not relieve it of any liability that it may have to any
indemnified party except to the extent the indemnifying party demonstrates that
the defense of such action is prejudiced thereby. In case any such action shall
be brought against an indemnified party and it shall give written notice to the
indemnifying party of the commencement thereof, the indemnifying party shall be
entitled to participate therein and, to the extent that it may wish, to assume
the defense thereof with counsel reasonably satisfactory to such indemnified
party. If the indemnifying party elects to assume the defense of such action,
the indemnified party shall have the right to employ separate counsel at its own
expense and to participate in the defense thereof. If the indemnifying party
elects not to assume (or fails to assume) the defense of such action, the
indemnified party shall be entitled to assume the defense of such action with
counsel of its own choice, at the expense of the indemnifying party. If the
action is asserted against both the indemnifying party and the indemnified party
and there is a conflict of interests which renders it inappropriate for the same
counsel to represent both the indemnifying party and the indemnified party, the
indemnifying party shall be responsible for paying for separate counsel for the
indemnified party; provided, however, that if there is more than one indemnified
party, the indemnifying party shall not be responsible for paying for more than
one separate firm of attorneys to represent the indemnified parties, regardless
of the number of indemnified parties. If the indemnifying party elects to assume
the defense of such action, (a) no compromise or settlement thereof may be
effected by the indemnifying party without the indemnified party's written
consent (which shall not be unreasonably withheld) unless the sole relief
provided is monetary damages that are paid in full by the indemnifying party and
(b) the indemnifying party shall have no liability with respect to any
compromise or settlement thereof effected without its written consent (which
shall not be unreasonably withheld).

          (f)  It is the express intention of the parties hereto that each
               -----------------------------------------------------------
person to be indemnified pursuant to this Section 17.5 or Article XII shall be
------------------------------------------------------------------------------
indemnified and held harmless from and against all Damages as to which indemnity
--------------------------------------------------------------------------------
is provided for under this Section 17.5 or Article XII notwithstanding that any
-------------------------------------------------------------------------------
such Damages arise out of or result from the ordinary,
------------------------------------------------------

                                       53
<PAGE>

strict, sole, or contributory negligence of such person and regardless of
-------------------------------------------------------------------------
whether any other person (including the other party to this Agreement) is or is
-------------------------------------------------------------------------------
not also negligent.
------------------

      Section 17.6.  Waiver and Amendment.  No failure or delay (whether by
                     --------------------
course of conduct or otherwise) by any party hereto in exercising any right,
power or remedy which such holder may have under the Agreement or any of the
Ancillary Documents shall operate as a waiver thereof or of any other right,
power or remedy, nor shall any single or partial exercise thereof preclude any
other or further exercise thereof or of any other right, power or remedy.  No
waiver of any provision of this Agreement or any Ancillary Document and no
consent to any departure therefrom shall ever be effective unless it is in
writing and signed as provided below in this section, and then such waiver or
consent shall be effective only in the specific instances and for the purposes
for which given and to the extent specified in such writing.  No waiver,
consent, release, modification or amendment of or supplement to this Agreement
or any of the Ancillary Documents shall be valid or effective against any party
hereto unless the same is in writing and signed by such party.

      Section 17.7.   Entire Agreement.  This Agreement, together with the
                      ----------------
Schedules and other writings referred to herein or delivered pursuant hereto,
constitute the entire agreement between the parties hereto with respect to the
subject matter hereof and supersede all prior agreements and understandings,
both written and oral, between the parties with respect to the subject matter
hereof.

      Section 17.8.   Binding Effect; Assignment; No Third Party Benefit.  This
                      --------------------------------------------------
Agreement shall be binding upon and inure to the benefit of the parties hereto
and their respective successors and assigns;  provided, however, that prior to
Closing, neither party may assign its rights or delegate any of its duties and
obligations under this Agreement or the Ancillary Documents without the prior
written consent of the other; provided, further, that after the Closing, Buyer
may not assign its rights or delegate any of its duties and obligations under
this Agreement and the Ancillary Documents without the prior written consent of
Seller.  Except as expressly provided herein, nothing in this Agreement, express
or implied, is intended to or shall confer upon any Person other than the
parties hereto, and their respective successors and permitted assigns, any
rights, benefits, or remedies of any nature whatsoever under or by reason of
this Agreement.

      Section 17.9.   Severability. If any provision of this Agreement is held
                      ------------
to be unenforceable, this Agreement shall be considered divisible and such
provision shall be deemed inoperative to the extent it is deemed unenforceable,
and in all other respects this Agreement shall remain in full force and effect;
provided, however, that if any such provision may be made enforceable by
limitation thereof, then such provision shall be deemed to be so limited and
shall be enforceable to the maximum extent permitted by Applicable Law.

      Section 17.10.  Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND
                      -------------
CONSTRUED AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS,
WITHOUT REGARD TO THE PRINCIPLES OF CONFLICTS OF LAWS THEREOF.

                                       54
<PAGE>

      Section 17.11.  Remedies Not Exclusive.  The rights and remedies herein
                      ----------------------
provided shall be cumulative and not exclusive of any rights or remedies
provided by law.  The rights and remedies of any party based upon, arising out
of, or otherwise in respect of any inaccuracy in or breach of any
representation, warranty, covenant, or agreement contained in this Agreement
shall in no way be limited by the fact that the act, omission, occurrence, or
other state of facts upon which any claim of any such inaccuracy or breach is
based may also be the subject matter of any other representation, warranty,
covenant, or agreement contained in this Agreement (or in any other agreement
between the parties) as to which there is no inaccuracy or breach.

      Section 17.12.  Further Assurances.  From time to time following the
                      ------------------
Closing, at the request of any party hereto and without further consideration,
the other party or parties hereto shall execute and deliver to such requesting
party such instruments and documents and take such other action (but without
incurring any material financial obligation) as such requesting party may
reasonably request in order to consummate more fully and effectively the
transactions contemplated hereby.

      Section 17.13.  Counterparts.  This Agreement may be executed by the
                      ------------
parties hereto in any number of counterparts, each of which shall be deemed an
original, but all of which shall constitute one and the same agreement.  Each
counterpart may consist of a number of copies hereof each signed by less than
all, but together signed by all, the parties hereto.

      Section 17.14.  Injunctive Relief.  The parties hereto acknowledge and
                      -----------------
agree that irreparable damage would occur in the event any of the provisions of
this Agreement were not performed in accordance with their specific terms or
were otherwise breached.  It is accordingly agreed that the parties shall be
entitled to an injunction or injunctions to prevent breaches of the provisions
of this Agreement, and shall be entitled to enforce specifically the provisions
of this Agreement, in any court of the United States or any state thereof having
jurisdiction, in addition to any other remedy to which the parties may be
entitled under this Agreement or at law or in equity.

      Section 17.15.  Consent to Jurisdiction.  Subject to Section 7.5, the
                      -----------------------
parties hereto hereby irrevocably submit to the jurisdiction of the courts of
the State of Texas and the federal courts of the United States of America
located in Harris County, Texas, and appropriate appellate courts therefrom,
over any dispute arising out of or relating to this Agreement or any of the
transactions contemplated hereby, and each party hereby irrevocably agrees that
all claims in respect of such dispute or proceeding shall be heard and
determined in such courts.  Subject to Section 7.5, the parties hereby
irrevocably waive, to the fullest extent permitted by Applicable Law, any
objection which they may now or hereafter have to the laying of venue of any
dispute arising out of or relating to this Agreement or any of the transactions
contemplated hereby brought in such court or any defense of inconvenient forum
for the maintenance of such dispute.  Each of the parties hereto agrees that a
judgment in any such dispute may be enforced in other jurisdictions by suit on
the judgment or in any other manner provided by law.  This consent to
jurisdiction is being given solely for purposes of this Agreement and is not
intended to, and shall not, confer consent to jurisdiction with respect to any
other dispute in which a party to this Agreement may become involved.

                                       55
<PAGE>

      Section 17.17.  Payments.  All payments to be made hereunder shall be in
                      --------
lawful money of the United States of America.

      Section 17.18.  Right to Purchase New Equity Securities.  Buyer grants to
                      ---------------------------------------
Seller the same rights as provided to the "Purchasers" under Section 2.03 of the
Preferred Stock Purchase Agreement, and the terms and conditions of such Section
are hereby incorporated herein, mutatis mutandis.
                                ----------------

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                       56
<PAGE>

     IN WITNESS WHEREOF, this Agreement is executed by the parties hereto on the
date set forth above.

                              SELLER:

                              MOUNTAINEER LIMITED PARTNERSHIP

                              By:   SHAHARA OIL, LLC

                              By:   _________________________________
                                    Name: Perry L. Hughes
                                    Title: Executive Officer

                              BUYER:

                              AROC INC.

                              By:   _________________________________
                                    Name:____________________________
                                    Title:___________________________

                                       57<PAGE>

                                                                    EXHIBIT 10.5

________________________________________________________________________________

                              Purchase Agreement

                                by and between

                                  Aroc  Inc.

                                      and

                     EnCap Equity 1996 Limited Partnership

                                      and

                     Energy Capital Investment Company PLC

                                      and

                      El Paso Capital Investments, L.L.C.

                                  May 1, 2000

________________________________________________________________________________
<PAGE>

<TABLE>
<CAPTION>
                                                                                        Page
<S>                                                                                     <C>
ARTICLE I
     DEFINITIONS........................................................................   1
          1.1  Certain Defined Terms....................................................   1
          1.2  Certain Additional Defined Terms.........................................   8
          1.3  References and Construction..............................................   9

ARTICLE II
     TERMS OF THE TRANSACTION...........................................................   9
          2.1  Agreement to Sell and to Purchase Notes and Warrants.....................   9
          2.2. Payment.................................................................   10
          2.3. Placement Fee............................................................  10

ARTICLE III
     CLOSING............................................................................  10
          3.1  Closing..................................................................  10
          3.2  Deliveries by the Company................................................  11
          3.3  Deliveries by Buyer......................................................  11

ARTICLE IV
     REPRESENTATIONS AND WARRANTIES OF SELLER...........................................  12
          4.1  Corporate Organization...................................................  12
          4.2  Qualification............................................................  12
          4.3  Charter and Bylaws.......................................................  12
          4.4  Capitalization of the Company............................................  12
          4.5  Authority Relative to This Agreement.....................................  13
          4.6  No Conflict..............................................................  13
          4.7  Consents and Approvals, Licenses, Etc....................................  14
          4.8  Subsidiaries.............................................................  14
          4.9  Warrants.................................................................  15
         4.10  Financial Statements.....................................................  15
         4.11  SEC Filings..............................................................  16
         4.12  Absence of Undisclosed Liabilities.......................................  16
         4.13  Absence of Certain Changes...............................................  16
         4.14  Tax Matters..............................................................  17
         4.15  Environmental and Other Laws.............................................  18
         4.16  Legal Proceedings........................................................  19
         4.17  Title to Properties; Permits; Licenses; Condition of Assets..............  19
         4.18  ERISA....................................................................  20
         4.19  Agreements...............................................................  21
         4.20  Labor Disputes and Acts of God...........................................  23
</TABLE>

                                      -i-
<PAGE>

<TABLE>
<S>                                                                                       <C>
         4.21  Registration Rights......................................................  23
         4.22  Offering of Securities...................................................  23
         4.23  Government Regulation....................................................  23
         4.24  Brokerage Fees...........................................................  24
         4.25  Solvency.................................................................  24
         4.26  Insurance................................................................  24
         4.27  Full Disclosure..........................................................  24

ARTICLE V
     REPRESENTATIONS AND WARRANTIES OF BUYER............................................  24
          5.1  Organization.............................................................  24
          5.2  Authority Relative to This Agreement.....................................  24
          5.3  Investment Intent; Investment Experience;
                 Restricted Securities..................................................  25
          5.4  Brokerage Fees...........................................................  25

ARTICLE VI
     CONDUCT OF COMPANY PENDING CLOSING.................................................  25

ARTICLE VII
     CONDITIONS TO OBLIGATIONS OF THE COMPANY...........................................  26
          7.1  Representations and Warranties True......................................  26
          7.2  Covenants and Agreements Performed.......................................  26
          7.3  HSR Act..................................................................  26
          7.4  Legal Proceedings........................................................  26

ARTICLE VIII
     CONDITIONS TO OBLIGATIONS OF BUYER.................................................  27
          8.1  Representations and Warranties True......................................  27
          8.2  Covenants and Agreements Performed.......................................  27
          8.3  HSR Act..................................................................  27
          8.4  Legal Proceedings........................................................  27
          8.5  Consents.................................................................  27
          8.6  No Material Adverse Change...............................................  27
          8.7  Subordination Agreement..................................................  28
          8.8  Registration Rights Agreement............................................  28
          8.9. Closing of the Senior Credit Facility....................................  28

ARTICLE IX
     PRE-CLOSING TERMINATION............................................................  28
          9.1  Termination..............................................................  28
          9.2  Effect of Termination....................................................  28

ARTICLE X
</TABLE>

                                      -ii-
<PAGE>

<TABLE>
<S>                                                                                       <C>
     AFFIRMATIVE COVENANTS OF THE COMPANY...............................................  29
         10.1  Payment and Performance..................................................  29
         10.2  Books, Financial Statements and Reports..................................  29
         10.3  Notice of Material Events and Change of Address..........................  30
         10.4  Maintenance of Properties................................................  31
         10.5  Maintenance of Existence and Qualifications..............................  31
         10.6  Payment of Trade Liabilities, Taxes, etc.................................  31
         10.7  Insurance................................................................  31
         10.8  Compliance with Agreements and Law.......................................  32
         10.9  Guaranties of Company's Subsidiaries.....................................  32
        10.10  Inspection Rights........................................................  32
        10.11  Charter Amendment Approval...............................................  32

ARTICLE XI
     NEGATIVE COVENANTS OF THE COMPANY..................................................  32
         11.1  Indebtedness.............................................................  32
         11.2  Limitation on Liens......................................................  33
         11.3  Limitation on Mergers....................................................  33
         11.4  Limitation on Sales of Property..........................................  33
         11.5  Limitation on Investments and New Businesses.............................  34
         11.6  Transactions with Affiliates.............................................  34
         11.7  Restricted Payments......................................................  34

ARTICLE XII
     PREPAYMENT OF THE NOTES............................................................  34

ARTICLE XIII
     EVENTS OF DEFAULT AND REMEDIES.....................................................  35
         13.1  Events of Default........................................................  35
         13.2  Remedies.................................................................  37

ARTICLE XIV
     ADDITIONAL AGREEMENTS..............................................................  37
         14.1  Third Party Consents.....................................................  37
         14.2  Access to Information....................................................  37
         14.3  Use of Proceeds..........................................................  38
         14.4  Public Announcements.....................................................  38
         14.5  Fees and Expenses........................................................  38
         14.6  Costs of Enforcement.....................................................  38
         14.7  Indemnification..........................................................  38

ARTICLE XV
     MISCELLANEOUS......................................................................  38
         15.1  Notices..................................................................  38
</TABLE>

                                     -iii-
<PAGE>

<TABLE>
<S>                                                                                       <C>
         15.2  Waiver and Amendment.....................................................  40
         15.3  Survival.................................................................  40
         15.4  Entire Agreement.........................................................  40
         15.5  Binding Effect; Assignment; No Third Party Benefit.......................  40
         15.6  Severability.............................................................  41
         15.7  GOVERNING LAW............................................................  41
         15.8  Remedies Not Exclusive...................................................  41
         15.9  Further Assurances.......................................................  41
        15.10  Counterparts.............................................................  41
        15.11  Injunctive Relief........................................................  41
        15.12  Consent to Jurisdiction..................................................  42
        15.13  Payments.................................................................  42
        15.14. Master Subordination Agreement...........................................  42
</TABLE>

                                      -iv-
<PAGE>

                              PURCHASE AGREEMENT

     THIS PURCHASE AGREEMENT (this "Agreement"), dated as of May 1, 2000, is
made by and between AROC Inc., a Delaware corporation (the "Company"),  EnCap
Equity 1996 Limited Partnership, a Texas limited partnership ("EnCap LP"),
Energy Capital Investment Company PLC, an English investment company ("ECIC"),
and El Paso Capital Investments, L.L.C., a Delaware limited liability company
("El Paso") (with EnCap LP, ECIC and El Paso sometimes being herein collectively
called "Buyer").

     WHEREAS, the Company desires to issue and sell to Buyer, and Buyer desires
to purchase from the Company, (i) the Company's 12% Subordinated Notes due 2007
in the aggregate principal amount of $17,000,000 (the "Notes") and (ii) warrants
to purchase the Company's Common Stock (as defined herein);

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
and agreements herein contained, and intending to be legally bound hereby, the
Company and Buyer hereby agree as follows:

                                   ARTICLE I

                                  DEFINITIONS

     1.1  Certain Defined Terms.  As used in this Agreement, each of the
          ---------------------
following terms has the meaning given it below:

          "Affiliate" means, with respect to any Person, any other Person that,
     directly or indirectly, through one or more intermediaries, controls, is
     controlled by or is under common control with, such Person.  For the
     purposes of this definition, "control" when used with respect to any Person
     means 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, by contract, or otherwise; and
     the terms "controlling" and "controlled" have meanings correlative to the
     foregoing.

          "Agreement" means this Agreement, as hereafter changed, amended or
     modified in accordance with the terms hereof.

          "Alliance Group" means Alliance Resources Group, Inc., a Delaware
     corporation.

          "Alliance PLC" means Alliance Resources PLC, a public limited company
     incorporated in England and Wales.

          "Alliance USA" means Alliance Resources (USA), Inc., a Delaware
     corporation.
<PAGE>

          "Ancillary Documents" means each agreement, certificate, document,
     commitment and writing (other than this Agreement) executed or to be
     executed by the Company or Buyer in connection with the transactions
     contemplated herein or therein, including the Notes and the Subsidiary
     Guarantees.

          "Applicable Law" means any statute, law, rule or regulation, or any
     judgment, order, writ, injunction or decree of, any Governmental Entity to
     which a specified Person or property is subject.

          "AROC (Texas)" means AROC (Texas), Inc., a Texas corporation.

          "Change of Control" means the occurrence of any of the following
     events: (a) any Person or two or more Persons, other than the Company or
     any affiliate of the Company, acting as a group shall acquire beneficial
     ownership (within the meaning of Rule 13d-3 of the Securities and Exchange
     Commission under the Exchange Act, and including holding proxies to vote
     for the election of directors other than proxies held by the Company's
     management or their designees to be voted in favor of persons nominated by
     the Company's Board of Directors) of 33% or more of the outstanding voting
     securities of the Company, measured by voting power (including both
     ordinary shares and any preferred stock or other equity securities
     entitling the holders thereof to vote with the holders of common stock in
     elections for directors of the Company), (b) the Company shall fail
     beneficially to own, directly or indirectly, 100% of the outstanding shares
     of voting capital stock of Alliance PLC, Alliance Group, Difco, Source,
     AROC (Texas), Alliance USA, LPC or GOC on a fully-diluted basis, (c) one-
     third or more of the directors of the Company shall consist of persons not
     nominated by the Company's Board of Directors (not including as Board
     nominees any directors which the Board is obligated to nominate pursuant to
     shareholders agreements, voting trust arrangements or similar arrangements)
     or (d) within three years of the Closing Date, the employment by the
     Company of John Keenan or Paul Fenemore terminates for any reason.

          "Charter Amendment Approval" means approval of the Charter Matters in
     accordance with the Articles of Incorporation of the Company and Applicable
     Laws.

          "Charter Matters" means an amendment to the Articles of Incorporation
     of the Company to increase the number of authorized shares of Common Stock
     to a level as shall permit the full and complete exercise of the Warrants
     into Common Stock.

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

          "Common Stock" means common stock, $0.001 par value per share, of
     Buyer and any securities issued or issuable with respect to such shares by
     way of a stock dividend or stock split or in connection with a combination
     of shares, recapitalization, merger, consolidation or other reorganization.

          "Companies Act" means the Companies Act 1985 as amended.

                                      -2-
<PAGE>

          "Default" means an Event of Default and any default, event or
     condition which would, with the giving of any requisite notices and the
     passage of any requisite periods of time, constitute an Event of Default.

          "Difco" means Difco Limited, a private limited company incorporated
     under the laws of England and Wales

          "Environmental Laws" means any and all laws relating to the
     environment or to emissions, discharges, releases or threatened releases of
     pollutants, contaminants, chemicals, or industrial, toxic or hazardous
     substances or wastes into the environment including ambient air, surface
     water, ground water, or land, or otherwise relating to the manufacture,
     processing, distribution, use, treatment, storage, disposal, transport, or
     handling of pollutants, contaminants, chemicals, or industrial, toxic or
     hazardous substances or wastes.

          "ERISA" means the Employee Retirement Income Security Act of 1974, as
     amended.

          "Exchange Act" means the U.S. Securities Exchange Act of 1934, as
     amended.

          "Fiscal Quarter" means a three-month period ending on July 31, October
     31, January 31 or April 30 of any year.

          "Fiscal Year" means the twelve-month period ending on April 30 of any
     year.

          "GOC" means Germany Oil Company, a Delaware corporation.

          "Governmental Entity" means any court or tribunal in any jurisdiction
     (domestic or foreign) or any federal, state, municipal or other
     governmental body, agency, authority, department, commission, board, bureau
     or instrumentality (domestic or foreign).

          "Hazardous Materials" means any substance regulated under
     Environmental Law, whether as pollutants, contaminants, or chemicals, or as
     industrial, toxic or hazardous substances or wastes, or otherwise.

          "HSR Act" means the Hart-Scott-Rodino Antitrust Improvements Act of
     1976, as amended.

          "Indebtedness" of any Person means Liabilities in any of the following
     categories: (a) Liabilities for borrowed money; (b) Liabilities
     constituting an obligation to pay the deferred purchase price of property
     or services; (c) Liabilities evidenced by a bond, debenture, note or
     similar instrument; (d) Liabilities which  would under U.S. GAAP be shown
     on such Person's balance sheet as a liability, and  is payable more than
     one year from the date of creation thereof (other than reserves for taxes
     and reserves for contingent obligations); (e) Liabilities arising under
     futures contracts, forward contracts, swap, cap or collar contracts, option
     contracts, hedging contracts, other derivative contracts, or similar
     agreements; (f)

                                      -3-
<PAGE>

     Liabilities constituting principal under leases capitalized in accordance
     with U.S. GAAP; (g) Liabilities arising under conditional sales or other
     title retention agreements; (h) Liabilities owing under direct or indirect
     guaranties of Liabilities of any other Person or constituting obligations
     to purchase or acquire or to otherwise protect or insure a creditor against
     loss in respect of Liabilities of any other Person (such as obligations
     under working capital maintenance agreements, agreements to keep-well, or
     agreements to purchase Liabilities, assets, goods, securities or services),
     but excluding endorsements in the ordinary course of business of negotiable
     instruments in the course of collection; (i) Liabilities (for example,
     repurchase agreements) consisting of an obligation to purchase securities
     or other property, if such Liabilities arises out of or in connection with
     the sale of the same or similar securities or property; (j) Liabilities
     with respect to letters of credit or applications or reimbursement
     agreements therefor; (k) Liabilities with respect to payments received in
     consideration of oil, gas, or other minerals yet to be acquired or produced
     at the time of payment (including obligations under "take-or-pay" contracts
     to deliver gas in return for payments already received and the undischarged
     balance of any production payment created by such Person or for the
     creation of which such Person directly or indirectly received payment); or
     (l) Liabilities with respect to other obligations to deliver goods or
     services in consideration of advance payments therefor; provided, however,
     that the "Indebtedness" of any Person shall not include Liabilities that
     were incurred by such Person on ordinary trade terms to vendors, suppliers,
     or other Persons providing goods and services for use by such Person in the
     ordinary course of its business, unless and until such Liabilities are
     outstanding more than 90 days past the original invoice or billing date
     therefor.

          "IRS" means the Internal Revenue Service.

          "Key Employment Agreements" means (i) that certain Executive
     Employment Agreement dated as of December 8, 1999 between the Company and
     John A. Keenan, and (ii) that certain Service Agreement dated September 20,
     1996 between Alliance PLC and Paul Raymond Fenemore, as amended by
     Supplemental Agreement dated September 20, 1996, Second Supplemental
     Agreement dated December 1, 1998, and letter agreement dated as of December
     8, 1999.

          "Liabilities" means, as to any Person, all indebtedness, liabilities
     and obligations of such Person, whether matured or unmatured, liquidated or
     unliquidated, primary or secondary, direct or absolute, fixed or
     contingent, and whether or not required to be considered pursuant to U.S.
     GAAP.

          "Lien" means, with respect to any property or assets, any right or
     interest therein of a creditor to secure Liabilities owed to such creditor
     or any other arrangement with such creditor which provides for the payment
     of such Liabilities out of such property or assets or which allows him to
     have such Liabilities satisfied out of such property or assets prior to the
     general creditors of any owner thereof, including any lien, mortgage,
     security interest, pledge, deposit, production payment, rights of a vendor
     under any title retention or conditional sale agreement or lease
     substantially equivalent thereto, tax lien, mechanic's or materialman's
     lien,

                                      -4-
<PAGE>

     or any other charge or encumbrance for security purposes, whether arising
     by law or agreement or otherwise, but excluding any right of offset which
     arises without agreement in the ordinary course of business. "Lien" also
     means any filed financing statement, any registration of a pledge (such as
     with an issuer of uncertificated securities), or any other arrangement or
     action which would serve to perfect a Lien described in the preceding
     sentence, regardless of whether such financing statement is filed, such
     registration is made, or such arrangement or action is undertaken before or
     after such Lien exists.

          "Listing Rules" means the listing rules of the London Stock Exchange.

          "London Stock Exchange" means the London Stock Exchange Limited.

          "LPC" means LaTex Petroleum Corporation, an Oklahoma corporation.

          "LRI" means LaTex Resources, Inc., a Delaware corporation.

          "LRI Merger" means the merger of Alliance Resources (Delaware) Inc.
     with and into LRI whereby the Company became the sole shareholder of LRI.

          "Majority of the Noteholders" means those holder(s) of the Notes who
     hold a majority in aggregate principal amount of the Notes at the time
     outstanding, exclusive of any Notes held by the Company or any Subsidiary.

          "Material Adverse Effect" means a material adverse change in, or a
     material adverse effect upon (i) the business, assets, results of
     operations, condition (financial or otherwise) or prospects of the Company
     and its Subsidiaries on a consolidated basis, (ii) the Company's or any
     Subsidiary Guarantor's ability to timely pay the Obligations or to perform
     on a timely basis any material obligation of the Company under this
     Agreement or any agreement, instrument, or document entered into or
     delivered in connection herewith or (iii) the enforceability of the
     material terms of this Agreement or any Ancillary Document.

          "Obligations" means all Liabilities owing Buyer or, if different, the
     holder(s) of the Notes, pursuant to the this Agreement, the Notes or any of
     the other Ancillary Documents.

          "Old LaTex Payables" means those current accounts payable of the
     Company or its consolidated Subsidiaries that meet one or more of the
     following tests and have been certified to Buyer by the Company and
     applicable Subsidiary as being an Old LaTex Payable:

               (a) accounts payable the collection of which is barred by the
          applicable statute of limitations;

               (b) accounts payable the collection of which has been compromised
          or forgiven in part, in either case to the extent of the amount that
          has been compromised or forgiven; or

                                      -5-
<PAGE>

               (c) accounts payable in respect of which the indebtedness was
          incurred prior to the LRI Merger and where each of the following is
          true: (i) no payment has been made on an individual amount of
          indebtedness payable since the LRI Merger, (ii) no contact has been
          received by the Company or applicable Subsidiary from the applicable
          creditor since the LRI Merger pertaining to such account or if contact
          has been received, such account is being diligently contested in good
          faith, (iii) no promise to pay such account has been made by the
          Company or applicable Subsidiary since the LRI Merger and (iv) no
          judgment has been obtained by, or settlement agreement entered into
          with, such creditor with respect to such indebtedness.

          "Permits" means licenses, permits, franchises, consents, approvals,
     variances, exemptions and other authorizations of or from Governmental
     Entities.

          "Permitted Investment" means any investment, loan, advance, guaranty
     or capital contribution by the Company or any Subsidiary in any of the
     following: (a) properties or assets to be used in the ordinary course of
     business of the Company and its Subsidiaries; (b) current assets arising
     from the sale of goods and services in the ordinary course of business of
     the Company and its Subsidiaries; (c) investments in one or more of the
     Company's Subsidiaries or in any Person that concurrently with such
     investment becomes a Subsidiary; (d) any marketable obligation maturing not
     later than one year after the date of acquisition therefor, issued or
     guaranteed by the United States of America or by any agency of the United
     States of America which has the full faith and credit of the United States
     of America; (e) commercial paper which is given the highest rating by a
     credit rating agency of recognized national standing and maturing not more
     than 270 days from the date of creation thereof; and (f) any demand deposit
     or time deposit (including certificates of deposit and money market or
     sweep accounts) with a commercial bank or trust company organized and doing
     business under the laws of the United States of America or any state
     thereof which has capital, surplus and undivided profits of at least
     $250,000,000, provided that such deposit must be either payable on demand
     or mature not more than twelve months from the date of investment therein.

          "Person" means any individual, corporation, partnership, joint
     venture, association, joint-stock company, trust, enterprise,
     unincorporated organization or Governmental Entity.

          "Proceedings" means all proceedings, actions, claims, suits,
     investigations and inquiries by or before any arbitrator or Governmental
     Entity.

          "reasonable best efforts" means a party's reasonable best efforts in
     accordance with reasonable commercial practice and without the incurrence
     of unreasonable expense.

          "Restricted Payment" means any Distribution (as defined below) in
     respect of the Company or any Subsidiary thereof (other than on account of
     capital stock or other equity interests of a Subsidiary owned legally or
     beneficially by the Company or another Subsidiary), including any
     Distribution resulting in the acquisition by the Company of securities that
     would

                                      -6-
<PAGE>

     constitute treasury stock. As used in this definition, "Distribution"
     means, in respect of any corporation, partnership or other business entity
     (a) dividends or other distributions or payments on capital stock or other
     equity interest of such corporation, partnership or other business entity
     (except distributions in such stock or other equity interest) and (b) the
     redemption or acquisition of such stock or other equity interests or of
     warrants, rights or other options to purchase such stock or other equity
     interests (except when solely in exchange for such stock or other equity
     interests).

          "Securities" means the Notes and the Warrants issued pursuant to
     Article II.

          "Securities Act" means the U.S. Securities Act of 1933, as amended.

          "Securities and Exchange Commission" means the U.S. Securities and
     Exchange Commission.

          "Senior Credit Facility" means that certain Credit Agreement dated as
     of May 1, 2000, by and among the Company, Toronto-Dominion (Texas), Inc.,
     as Agent, and the lenders signatory thereto.

          "Source" means Source Petroleum, Inc., a Louisiana corporation.

          "Subsidiary" means any corporation more than 50% of whose outstanding
     voting securities, or any general partnership, joint venture or similar
     entity more than 50% of whose total equity interests, is owned, directly or
     indirectly, by the Company, or any limited partnership of which the Company
     or any Subsidiary is a general partner.

          "Subsidiary Guarantors" means Alliance PLC, Difco, Alliance Group,
     Source, AROC (Texas), Alliance USA, LPC and GOC.

          "Taxes" means any income taxes or similar assessments or any sales,
     excise, occupation, use, ad valorem, property, production, severance,
     transportation, employment, payroll, franchise, transfer, stamp,
     withholding or other tax imposed by any United States federal, state or
     local (or any foreign or provincial) taxing authority, including any
     interest, penalties or additions attributable thereto.

          "Tax Return" means any return or report (including but not limited to
     any related or supporting information, any amended return or report or any
     information return or report) with respect to Taxes.

          "Treasury Regulations" means one or more treasury regulations
     promulgated under the Code by the Treasury Department of the United States.

          "U.S. GAAP" means generally accepted accounting principles in the
     United States of America from time to time.

                                      -7-
<PAGE>

          "Warrant" means a warrant to purchase Common Stock issued pursuant to
     the terms hereof.

      1.2 Certain Additional Defined Terms.  In addition to such terms as are
          --------------------------------
defined in the opening paragraph of and the recitals to this Agreement and in
Section 1.1, the following terms are used in this Agreement as defined in the
Sections or Articles set forth opposite such terms:

     Defined Term                               Section  or Article Reference
     ------------                               -----------------------------

agreements......................................              4.19
Audited Financial Statements....................              4.10
Closing.........................................               3.1
Closing Date....................................               3.1
Event of Default................................              13.1
Latest Balance Sheet............................              4.10
Notes...........................................          preamble
Organic Documents...............................               4.3
Permitted Liens.................................              11.2
Purchase Price..................................                II
Registration Rights Agreement...................               3.2(c)
SEC Filings.....................................              4.11
Subsidiary Guarantees...........................               3.2(c)

     1.3  References and Construction.
          ---------------------------

     (a)  All references in this Agreement to articles, sections, subsections
and other subdivisions refer to corresponding articles, sections, subsections
and other subdivisions of this Agreement unless expressly provided otherwise.

     (b)  Titles appearing at the beginning of any of such subdivisions are for
convenience only and shall not constitute part of such subdivisions and shall be
disregarded in construing the language contained in such subdivisions.

     (c)  The words "this Agreement", "this instrument", "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.

     (d)  Words in the singular form shall be construed to include the plural
and vice versa, unless the context otherwise requires. Pronouns in masculine,
    ---- -----
feminine and neuter genders shall be construed to include any other gender.

     (e)  Unless the context otherwise requires or unless otherwise provided
herein, the terms defined in this Agreement which refer to a particular
agreement, instrument or document also refer to and include all renewals,
extensions, modifications, amendments or restatements of such

                                      -8-
<PAGE>

agreement, instrument or document, provided that nothing contained in this
subsection shall be construed to authorize such renewal, extension,
modification, amendment or restatement.

     (f)  Examples shall not be construed to limit, expressly or by implication,
the matter they illustrate.

     (g)  The word "includes" and its derivatives means "includes, but is not
limited to" and corresponding derivative expressions.

     (h)  No consideration shall be given to the fact or presumption that one
party had a greater or lesser hand in drafting this Agreement.

     (i)  Unless otherwise indicated, all references herein to "$" or "dollars"
shall refer to U.S. Dollars.

                                  ARTICLE II

                           TERMS OF THE TRANSACTION

     2.1  Agreement to Sell and to Purchase Notes and Warrants.  At the Closing,
          ----------------------------------------------------
and on the terms and subject to the conditions set forth in this Agreement, the
Company shall issue, allot, sell and deliver to EnCap LP, ECIC and El Paso, and
EnCap LP, ECIC and El Paso shall severally purchase and accept from the Company,
the securities set forth opposite its name below:

          EnCap LP            (1)  $9,000,000 principal amount of Notes; and

                              (2)  Warrant to purchase 20,933,594 shares of
                                   Common Stock

          ECIC                (1)  $3,000,000 principal amount of Notes; and

                              (2)  Warrant to purchase 6,977,865 shares of
                                   Common Stock

          El Paso             (1)  $5,000,000 principal amount of Notes; and

                              (2)  Warrant to purchase 11,629,774 shares of
                                   Common Stock

     2.2. Payment. EnCap LP, ECIC and El Paso, respectively, shall severally pay
          -------
to the Company at the Closing the aggregate amount set forth opposite its name
below (collectively, the "Purchase Price"):

                                      -9-
<PAGE>

          EnCap LP                 $ 9,000,000

          ECIC                     $ 3,000,000

          El Paso                  $ 5,000,000

     2.3. Placement Fee. At the Closing, the Company shall pay to each of EnCap
          -------------
LP, ECIC and El Paso, respectively, a placement fee in cash equal to 2% of the
amount set forth opposite its name in Section 2.2.

                                  ARTICLE III

                                    CLOSING

     3.1  Closing.  The closing of the transactions contemplated hereby (the
          -------
"Closing") shall take place at the offices of Thompson Knight Brown Parker &
Leahy, LLP, 1200 Smith, Suite 3600, Houston, Texas, at 10 a.m., local time, on
May 1, 2000, or at such other time or place or on such other date as the parties
hereto shall agree.  The date on which the Closing is required to take place is
herein referred to as the "Closing Date."  All Closing transactions shall be
deemed to have occurred simultaneously.

     3.2  Deliveries by the Company.  At the Closing, the Company will deliver
          -------------------------
the following documents to Buyer:

     (a)  A certificate executed on behalf of the Company by an authorized
signatory of the Company, dated the Closing Date, representing and certifying,
in such detail as Buyer may reasonably request, that the conditions set forth in
Sections 8.1 and 8.2 have been fulfilled.

     (b)  Opinion, in form, scope and content reasonably acceptable to Buyer, of
Jenkens & Gilchrist, counsel to the Company, dated the Closing Date.

     (c)  The certificates, instruments and documents listed below:

          (i)   The Notes, substantially in the form of Exhibit 3.2(c)(i) in all
                                                        -----------------
     material respects, duly executed by the Company.

          (ii)  Subsidiary guarantees substantially in the form of Exhibit
                                                                   -------
     3.2(c)(ii) in all material respects (the "Subsidiary Guarantees") of each
     ----------
     of the Subsidiary Guarantors, duly executed by the Subsidiary Guarantors.

          (iii) The Warrants, substantially in the form of Exhibit 3.2(c)(iii)
                                                           -------------------
     in all material respects, duly executed by the Company.

                                      -10-
<PAGE>

          (iv)  A counterpart of that certain Amended and Restated Registration
     Rights Agreement substantially in the form of Exhibit 3.2(c)(iv) in all
                                                   ------------------
     material respects (the "Registration Rights Agreement") duly executed by
     the Company.

          (v)   Certified copy of a written consent or resolutions of the Board
     of Directors of the Company and the Subsidiary Guarantors authorizing the
     execution, delivery and performance by the Company and the Subsidiary
     Guarantors of this Agreement and the Ancillary Documents, as necessary.

          (vi)  Certificates of existence and, for non-U.K. entities, good
     standing with respect to the Company and the Subsidiary Guarantors, dated
     within a number of days prior to the Closing Date reasonably acceptable to
     Buyer.

          (vii) Such other certificates, instruments, and documents as may be
     reasonably requested by Buyer prior to the Closing Date to carry out the
     intent and purposes of this Agreement.

     3.3  Deliveries by Buyer.  At the Closing, Buyer will deliver the following
          -------------------
to the Company:

     (a)  A certificate executed by an authorized signatory of Buyer, dated the
Closing Date, representing and certifying, in such detail as the Company may
reasonably request, that the conditions set forth in Sections 7.1 and 7.2 have
been fulfilled.

     (b)  The Purchase Price in immediately available funds by a confirmed wire
transfer to a bank account designated in writing by the Company to Buyer no
later than two business days prior to the Closing Date.

     (c)  The certificates, instruments, and documents listed below:

          (i)  A counterpart of the Registration Rights Agreement duly executed
     by Buyer.

          (ii) Such other certificates, instruments, and documents as may be
     reasonably requested by the Company prior to the Closing Date to carry out
     the intent and purposes of this Agreement.

                                  ARTICLE IV

                   REPRESENTATIONS AND WARRANTIES OF SELLER

     The Company represents and warrants to Buyer that:

     4.1  Corporate Organization. The Company is a corporation duly organized
          ----------------------
and validly existing under the laws of the State of Delaware.

                                      -11-
<PAGE>

      4.2  Qualification.  Each of the Company and the Subsidiaries is duly
           -------------
qualified or licensed to do business and, with respect to non-U.K. entities, in
good standing in each of the jurisdictions in which it owns, leases or operates
property or in which such qualification or licensing is required for the conduct
of its business.

      4.3  Charter and Bylaws.  The Company has made available to Buyer accurate
           ------------------
and complete copies of the Company's certificate of incorporation, bylaws,
memorandum and articles of association or equivalent organizational documents
("Organic Documents") as currently in effect, and stock records of the Company.
Neither the Company nor any Subsidiary is in violation of its Organic Documents
or its partnership agreement or similar governing document, as the case may be.

      4.4  Capitalization of the Company.  The authorized capital stock of the
           -----------------------------
Company, the number of shares outstanding and the number of shares held in the
Company's treasury are set forth on Schedule 4.4 hereto.  All outstanding shares
                                    ------------
of capital stock of the Company have been validly issued and are fully paid and
nonassessable, and no shares of capital stock of the Company are subject to, nor
have any been issued in violation of, preemptive or similar rights.  Except as
set forth on Schedule 4.4 hereto, there are (and as of the Closing Date there
             ------------
will be) outstanding (i) no shares of capital stock or other voting securities
of the Company, (ii) no securities of the Company convertible into or
exchangeable for shares of capital stock or other voting securities of the
Company, (iii) no options or other rights to acquire from the Company, and no
obligation of the Company to issue or sell, any shares of capital stock or other
voting securities of the Company or any securities of the Company convertible
into or exchangeable for such capital stock or voting securities, and (iv) no
equity equivalents, interests in the ownership or earnings or other similar
rights of or with respect to the Company.  Except as set forth on Schedule 4.4
                                                                  ------------
hereto, there are (and as of the Closing Date there will be) no outstanding
obligations of the Company or any Subsidiary to repurchase, redeem, or otherwise
acquire any of the foregoing shares, securities, options, equity equivalents,
interests, or rights.  Except as set forth on Schedule 4.4, the Company is not a
                                              ------------
party to, and is not aware of, any voting agreement, voting trust, or similar
agreement or arrangement relating to any class or series of its capital stock.

      4.5  Authority Relative to This Agreement.  The Company has full power and
           ------------------------------------
authority to execute, deliver, and perform this Agreement and the Ancillary
Documents, including the Notes, to which it is a party and to consummate the
transactions contemplated hereby and thereby. The execution, delivery, and
performance by the Company of this Agreement and the Ancillary Documents,
including the Notes, to which it is a party, and the consummation by it of the
transactions contemplated hereby and thereby, have been duly authorized by all
necessary action of the Company. This Agreement has been duly executed and
delivered by the Company and constitutes, and each Ancillary Document, including
the Notes, executed or to be executed by the Company has been, or when executed
will be, duly executed and delivered by the Company and constitutes, or when
executed and delivered will constitute, a valid and legally binding obligation
of the Company, enforceable against the Company in accordance with their
respective terms, except that such enforceability may be limited by (i)
applicable bankruptcy, insolvency, reorganization, moratorium, and similar laws
affecting creditors' rights generally and (ii) equitable principles which may
limit the availability of certain equitable remedies (such as specific
performance) in certain instances.

                                      -12-
<PAGE>

     4.6  No Conflict.  Assuming all consents, approvals, authorizations and
          -----------
other actions described in Section 4.7 have been obtained and all filings and
notifications listed on Schedule 4.7 have been made, and except as described on
                        ------------
Schedule 4.6, the execution, delivery and performance of this Agreement by the
------------
Company, the execution, delivery and performance by each Subsidiary of the
Ancillary Documents to which it is a party, and the consummation by them of the
transactions contemplated hereby and thereby do not and will not (a) violate or
conflict with the Organic Documents of the Company or any Subsidiary, (b)
conflict with or result in any violation of any provision of, or constitute
(with or without the giving of notice or the passage of time or both) a default
under, or give rise (with or without the giving of notice or the passage of time
or both) to any right of termination, cancellation, or acceleration under, or
require any consent, approval, authorization or waiver of, or notice to, any
party to, any bond, debenture, note, mortgage, indenture, lease, contract,
agreement, or other instrument or obligation to which the Company or any
Subsidiary is a party or by which the Company or any Subsidiary or any of their
respective properties may be bound or any Permit held by the Company or any
Subsidiary, (iii) result in the creation or imposition of any Lien upon the
properties of the Company or any Subsidiary (other than as provided in the
Senior Credit Facility) or (iv) violate any Applicable Law binding upon the
Company or any Subsidiary.

     4.7  Consents and Approvals, Licenses, Etc.  Except as set forth on
          --------------------------------------
Schedule 4.7, no consent, approval, authorization, license, order or permit of,
------------
or declaration, filing or registration with, or notification to, any
Governmental Entity, or any other Person or entity, is required to be made or
obtained by the Company or any Subsidiary in connection with the execution,
delivery and performance of this Agreement or any Ancillary Document and the
consummation of the transactions contemplated hereby and thereby.

     4.8  Subsidiaries.
          ------------

     (a)  The Company does not own, directly or indirectly, any capital stock or
equity securities of any corporation or have any direct or indirect equity or
ownership interest in any other Person, other than the Subsidiaries.  Schedule
                                                                      --------
4.8 lists each Subsidiary, the jurisdiction of incorporation or formation of
---
each Subsidiary and the authorized (in the case of capital stock) and
outstanding capital stock or other equity interests of each Subsidiary.  Each
U.K. Subsidiary is a duly formed and validly existing under the laws of the
jurisdiction of its formation, and each other Subsidiary is a corporation duly
organized, validly existing and in good standing under the laws of the
jurisdiction of its incorporation.  Each Subsidiary has all requisite corporate
or other, as applicable, power and authority to own, lease, and operate its
properties and to carry on its business as now being conducted.  No actions or
proceedings to dissolve any Subsidiary are pending.

     (b)  Except as otherwise indicated on Schedule 4.8, all the outstanding
                                           ------------
capital stock or other equity interests of each Subsidiary are owned directly or
indirectly by the Company, free and clear of all Liens.  All outstanding shares
of capital stock of each corporate Subsidiary have been validly issued and are
fully paid and nonassessable.  All equity interests of each other Subsidiary
have been validly issued and are fully paid (to the extent required at such
time).  No shares of capital stock

                                      -13-
<PAGE>

or other equity interests of any Subsidiary are subject to, nor have any been
issued in violation of, preemptive or similar rights.

     (c)  Except as set forth on Schedule 4.8, there are (and as of the Closing
                                 ------------
Date there will be) outstanding (i) no shares of capital stock or other voting
securities of any Subsidiary, (ii) no securities of the Company or any
Subsidiary convertible into or exchangeable for shares of capital stock or other
voting securities of any Subsidiary, (iii) no options or other rights to acquire
from the Company or any Subsidiary, and no obligation of the Company or any
Subsidiary to issue or sell, any shares of capital stock or other voting
securities of any Subsidiary or any securities convertible into or exchangeable
for such capital stock or voting securities and (iv) no equity equivalents,
interests in the ownership or earnings, or other similar rights of or with
respect to any Subsidiary. There are (and as of the Closing Date there will be)
no outstanding obligations of the Company or any Subsidiary to repurchase,
redeem or otherwise acquire any of the foregoing shares, securities, options,
equity equivalents, interests or rights.

     (d)  Each of the Subsidiary Guarantors has full power and authority to
execute, deliver, and perform the Subsidiary Guarantee and other Ancillary
Documents to which it is a party and to consummate the transactions contemplated
thereby.  The execution, delivery, and performance by each of the Subsidiary
Guarantors of the Subsidiary Guarantee and other Ancillary Documents to which it
is a party, and the consummation by it of the transactions contemplated thereby,
have been duly authorized by all necessary action of such Subsidiary Guarantor.
The Subsidiary Guarantees and each Ancillary Document executed or to be executed
by the Subsidiary Guarantors has been, or when executed will be, duly executed
and delivered by the Subsidiary Guarantors and constitutes, or when executed and
delivered will constitute, a valid and legally binding obligation of the
Subsidiary Guarantors, enforceable against the Subsidiary Guarantors in
accordance with their respective terms, except that such enforceability may be
limited by (i) applicable bankruptcy, insolvency, reorganization, moratorium,
and similar laws affecting creditors' rights generally and (ii) equitable
principles which may limit the availability of certain equitable remedies (such
as specific performance) in certain instances.

     4.9  Warrants.  The Warrants to be issued by the Company at the Closing
          --------
have been duly authorized for issuance and, when issued and delivered by the
Company in accordance with the provisions of this Agreement, will be validly
issued and will constitute valid and legally binding obligations of the Company
enforceable against the Company, except that such enforceability may be limited
by (i) applicable bankruptcy, insolvency, reorganization, moratorium, and
similar laws affecting creditors' rights generally and (ii) equitable principles
which may limit the availability of certain equitable remedies (such as specific
performance) in certain instances. Upon Charter Amendment Approval, the shares
of Common Stock issuable upon exercise of the Warrants will have been duly
authorized for issuance and, when issued and delivered by the Company in
accordance with the provisions of the Warrants, will be validly issued, fully
paid and nonassessable.

     4.10 Financial Statements. The Company has delivered to Buyer accurate and
          --------------------
complete copies of (i) Alliance PLC's audited consolidated balance sheet as of
April 30, 1999, and the related audited consolidated statements of income,
stockholders' equity and cash flows for the year then

                                      -14-
<PAGE>

ended, and the notes and schedules thereto, together with the unqualified report
thereon of KPMG Audit Plc, independent public accountants (the "Audited
Financial Statements") and (ii) the Company's unaudited consolidated balance
sheet as of January 31, 2000 (the "Latest Balance Sheet"), and the related
unaudited consolidated statements of income, stockholders' equity, and cash
flows for the three-month period then ended (the "Unaudited Financial
Statements"), certified by the Company's chief financial officer (collectively,
the "Financial Statements"). The Financial Statements (i) represent actual bona
fide transactions, (ii) have been prepared from the books and records of
Alliance PLC and the Company and their respective consolidated Subsidiaries in
conformity with U.S. GAAP accounting principles applied on a basis consistent
with preceding years throughout the periods involved and (iii) fairly present
Alliance PLC's and the Company's (as applicable) consolidated financial position
as of the respective dates thereof and Alliance PLC's and the Company's (as
applicable) consolidated results of operations and cash flows for the periods
then ended. The statements of income included in the Financial Statements do not
contain any items of special or nonrecurring income except as identified in the
notes thereto, and the balance sheets included in the Financial Statements do
not reflect any write-up or revaluation increasing the book value of any assets,
nor have there been any transactions since the date of the Latest Balance Sheet
giving rise to special or nonrecurring income or any such write-up or
revaluation.

     4.11  SEC Filings.  The Company and its Subsidiaries have filed with the
           -----------
Securities and Exchange Commission, the London Stock Exchange and the Registrar
of Companies all forms, reports, schedules, statements and other documents
required to be filed by it since May 1, 1997 under the Companies Act and the
Listing Rules and since April 30, 1997 under the Securities Act, the Exchange
Act and all other federal securities laws. All final forms, reports, schedules,
statements and other documents (including all amendments thereto) filed by the
Company and its Subsidiaries with the Securities and Exchange Commission and the
London Stock Exchange since such date are herein collectively referred to as the
"SEC Filings". The Company has delivered to Buyer accurate and complete copies
of all the SEC Filings in the form filed by the Company and its Subsidiaries
with the Securities and Exchange Commission and the London Stock Exchange. The
SEC Filings, at the time filed, complied in all material respects with all
applicable requirements of federal securities laws. None of the SEC Filings,
including any financial statements or schedules included therein, at the time
filed, contained any untrue statement of a material fact or omitted to state any
material fact required to be stated therein or necessary in order to make the
statements contained therein, in light of the circumstances under which they
were made, not misleading. All material contracts of the Company and the
Subsidiaries have been included in the SEC Filings, except for those contracts
not required to be filed pursuant to the rules and regulations of the Securities
and Exchange Commission and the London Stock Exchange. The Company shall deliver
to Buyer as soon as they become available accurate and complete copies of all
forms, reports, and other documents furnished by it to its shareholders
generally or filed by it with the Securities and Exchange Commission and the
London Stock Exchange subsequent to the date hereof and prior to the Closing
Date.

     4.12  Absence of Undisclosed Liabilities.  Neither the Company nor any
           ----------------------------------
Subsidiary has any liability or obligation (whether accrued, absolute,
contingent, unliquidated, or otherwise, whether or not known to the Company or
any Subsidiary, and whether due or to become due), except (i) liabilities
reflected on the Latest Balance Sheet, (ii) liabilities which have arisen since
the date of the

                                      -15-
<PAGE>

Latest Balance Sheet in the ordinary course of business (none of which is a
material liability for breach of contract, breach of warranty, tort, or
infringement), (iii) liabilities arising under executory contracts entered into
in the ordinary course of business (none of which is a material liability for
breach of contract) and (iv) liabilities specifically set forth on Schedule
                                                                   --------
4.12.
----

     4.13  Absence of Certain Changes.  Except as disclosed on Schedule 4.13,
           --------------------------                          -------------
since the date of the Latest Balance Sheet, (i) there has not been any material
adverse change in, or any event or condition that might reasonably be expected
to result in a material adverse change in, the business assets, results of
operations, condition (financial or otherwise) or prospects of the Company and
the Subsidiaries considered as a whole; (ii) the businesses of the Company and
the Subsidiaries have been conducted only in the ordinary course consistent with
past practice; (iii) neither the Company nor any Subsidiary has incurred any
material liability, engaged in any material transaction or entered into any
material agreement outside the ordinary course of business consistent with past
practice; (iv) neither the Company nor any Subsidiary has suffered any material
loss, damage, destruction, or other casualty to any of its assets (whether or
not covered by insurance); and (v) neither the Company nor any Subsidiary has
taken any of the actions set forth in Article VI except as permitted thereunder.

     4.14  Tax Matters.  Except as disclosed on Schedule 4.14:
           -----------                          -------------

     (a)   The Company and each Subsidiary has filed, or has had filed on its
behalf, in a timely manner (within any applicable extension periods) with the
appropriate taxing authority all Tax Returns with respect to Taxes of the
Company and of each of  the Subsidiaries, all of which Tax Returns are true,
correct and complete in all material respects;

     (b)   All Taxes due and payable (whether or not reflected in Tax Returns as
filed) with respect to all taxable periods of the Company and the Subsidiaries
have been paid in full or adequate reserves have been provided for on the
Financial Statements;

     (c)   There are no outstanding agreements or waivers extending the
statutory period of limitations applicable to any federal, state, local or
foreign income or other material Tax Returns required to be filed by or with
respect to the Company or any of the Subsidiaries;

     (d)   None of the Tax Returns of or with respect to the Company or any of
the Subsidiaries is currently being audited or examined by any taxing authority;

     (e)   No material deficiency for any Taxes has been assessed with respect
the Company or to any of the Subsidiaries that has not either (i) been abated or
(ii) paid in full or for which adequate reserves have been provided;

     (f)   No Tax litigation is currently pending;

     (g)   No waiver or extension of any statute of limitations to any federal,
state, local or foreign Tax matter has been given by or requested from the
Company or any Subsidiary; and

                                      -16-
<PAGE>

     (h)   Neither the Company nor any Subsidiary has filed a consent under
Section 341(f) of the Code.

     (i)   The Company and the Subsidiaries have complied with all Applicable
Laws relating to the withholding of Taxes and the payment thereof (including
withholding of Taxes under Sections 1441 and 1442 of the Code, or similar
provisions under foreign laws), and has timely and properly withheld from the
appropriate party and paid over to the proper Governmental Entity all amounts
required to be withheld and be paid over under Applicable Law.

     (j)   Neither the Company nor any Subsidiary is required to include in
income any adjustment under Section 481(a) of the Code by reason of a change in
accounting method, and neither the Company nor any Subsidiary, nor the Internal
Revenue Service, has proposed any such adjustment or change in accounting
method. The Company and the Subsidiaries do not have pending any private letter
ruling with the IRS.

     (k)   Other than as a result of this transaction, none of the Company's or
any Subsidiary's tax attributes is subject to the limitations of Section 382,
383 or 384 of the Code or Temporary Treasury Regulation Sections 1.1502-15T or
1.1502-21T(c).

     (l)   There are no liens for Taxes upon any assets of the Company or any
Subsidiary, except liens for Taxes not yet due and payable.

     (m)   The tax basis of each of the assets of the Company and the
Subsidiaries as set forth on the books, accounts and records of the Company and
the Subsidiaries is true, correct and complete in all material respects.

     4.15  Environmental and Other Laws.  Except as disclosed on Schedule 4.15
           ----------------------------                          -------------
or in the SEC Filings filed prior to the date hereof, (a) the Company and the
Subsidiaries are conducting their businesses in compliance in all material
respects with all Applicable Laws, including all Environmental Laws, and are in
material compliance with all licenses and permits required under any such laws;
(b) to the best of the Company's knowledge, none of the operations or properties
of the Company or any Subsidiary is the subject of foreign, federal, state or
local investigation evaluating whether any material remedial action is needed to
respond to a release of any Hazardous Materials into the environment or to the
improper storage or disposal (including storage or disposal at offsite
locations) of any Hazardous Materials; (c) neither the Company nor any
Subsidiary has filed any notice under any Applicable Law indicating that it is
responsible for the improper release into the environment, or the improper
storage or disposal, of any material amount of any Hazardous Materials or that
any Hazardous Materials have been improperly released, or are improperly stored
or disposed of, upon any property of the Company or any Subsidiary; (d) neither
the Company nor any Subsidiary has transported or arranged for the
transportation of any Hazardous Material to any location which is (i) listed on
the National Priorities List under the Comprehensive Environmental Response,
Compensation and Liability Act of 1980, as amended, listed for possible
inclusion on such National Priorities List by the Environmental Protection
Agency in its Comprehensive Environmental Response, Compensation and Liability
Information System List, or listed on any similar state list or

                                      -17-
<PAGE>

foreign jurisdiction list or (ii) the subject of foreign, federal, state or
local enforcement actions or other investigations which may lead to material
claims against the Company or any Subsidiary for clean-up costs, remedial work,
damages to natural resources or for personal injury claims (whether under
Environmental Laws or otherwise); and (e) to the best of the Company's
knowledge, neither the Company or any Subsidiary has any material contingent
liability under any Environmental Laws or in connection with the release into
the environment, or the storage or disposal, of any Hazardous Materials.

     4.16  Legal Proceedings.  Except as disclosed on Schedule 4.16, there are
           -----------------                          -------------
no Proceedings pending or, to the best knowledge of the Company, threatened
against or involving the Company or any Subsidiary (or any of their respective
directors or officers in connection with the business or affairs of the Company
or any Subsidiary) or any properties or rights of the Company or any Subsidiary
which, individually or in the aggregate, might reasonably be expected to have a
Material Adverse Effect. Neither the Company nor any Subsidiary is subject to
any judgment, order, writ, injunction, or decree of any Governmental Entity
which has had or is reasonably likely to have a Material Adverse Effect. There
are no Proceedings pending or, to the best knowledge of the Company, threatened
seeking to restrain, prohibit, or obtain damages or other relief in connection
with, or questioning the legality or validity of, this Agreement or any
Ancillary Document or the transactions contemplated hereby or thereby.

     4.17  Title to Properties; Permits; Licenses; Condition of Assets.
           -----------------------------------------------------------

     (a)   Each of the Company and the Subsidiaries has good and defensible
title to all of its material properties and assets, free and clear of all Liens
other than Permitted Liens and of all material impediments to the use of such
properties and assets in the businesses of the Company and the Subsidiaries.

     (b)   Each of the Company and the Subsidiaries holds all material Permits
necessary or required for the conduct of its business. Each of such Permits is
in full force and effect, the Company and the Subsidiaries are in compliance
with all of its material obligations with respect thereto, and, to the best
knowledge of the Company, no event has occurred which allows, or with or without
the giving of notice or the passage of time or both would allow, the revocation
or termination of any thereof. No notice has been issued by any Governmental
Entity and no proceeding is pending or, to the best knowledge of the Company,
threatened with respect to any alleged failure by the Company or any Subsidiary
to have any material Permit.

     (c)   The Company and the Subsidiaries possess all licenses, permits,
franchises, patents, copyrights, trademarks and trade names, and other
intellectual property (or otherwise possesses the right to use such intellectual
property without violation of the rights of any other Person) which are
necessary to carry out their businesses as presently conducted and as presently
proposed to be conducted hereafter, and neither the Company nor any Subsidiaries
is in violation in any material respect of the terms under which it possesses
such intellectual property or the right to use such intellectual property.

                                      -18-
<PAGE>

     (d)   The equipment and other tangible assets of the Company and the
Subsidiaries are in good operating condition (except for reasonable wear and
tear), and have been reasonably maintained.

     4.18  ERISA.
           -----

     (a)   Set forth on Schedule 4.18 is a list identifying each "employee
                        -------------
benefit plan", as defined in Section 3(3) of ERISA, (i) which is subject to any
provision of ERISA, (ii) which is maintained, administered, or contributed to by
the Company or any affiliate of the Company, and (iii) which covers any employee
or former employee of the Company or any affiliate of the Company or under which
the Company or any affiliate of the Company has any liability.  The Company has
delivered or made available to Buyer accurate and complete copies of such plans
(and, if applicable, the related trust agreements) and all amendments thereto
and written interpretations thereof, together with (i) the three most recent
annual reports (Form 5500 including, if applicable, Schedule B thereto) prepared
in connection with any such plan and (ii) the most recent actuarial valuation
report prepared in connection with any such plan.  Such plans are referred to in
this Section as the "Employee Plans".  For purposes of this Section only, an
"affiliate" of any person means any other person which, together with such
person, would be treated as a single employer under Section 414 of the Code.
The only Employee Plans which individually or collectively would constitute an
"employee pension benefit plan" as defined in Section 3(2) of ERISA are
identified as such on Schedule 4.18.
                      -------------

     (b)   Except as otherwise identified on Schedule 4.18, (i) no Employee Plan
                                             -------------
constitutes a "multiemployer plan", as defined in Section 3(37) of ERISA (for
purposes of this Section, a "Multiemployer Plan"), (ii) no Employee Plan is
maintained in connection with any trust described in Section 501(c)(9) of the
Code, (iii) no Employee Plan is subject to Title IV of ERISA or to the minimum
funding standards of ERISA and the Code, and (iv) during the past five years,
neither the Company nor any of its affiliates have made or been required to make
contributions to any Multiemployer Plan.  There are no accumulated funding
deficiencies as defined in Section 412 of the Code (whether or not waived) with
respect to any Employee Plan.  The fair market value of the assets held with
respect to each Employee Plan which is an employee pension benefit plan, as
defined in Section 3(2) of ERISA, exceeds the actuarially determined present
value of all benefit liabilities accrued under such Employee Plan (whether or
not vested) determined using reasonable actuarial assumptions.  Neither the
Company nor any affiliate of the Company has incurred any material liability
under Title IV of ERISA arising in connection with the termination of, or
complete or partial withdrawal from, any plan covered or previously covered by
Title IV of ERISA.  The Company and all of the affiliates of the Company have
paid and discharged promptly when due all liabilities and obligations arising
under ERISA or the Code of a character which if unpaid or unperformed might
result in the imposition of a lien against any of the assets of the Company or
any Subsidiary.  Nothing done or omitted to be done and no transaction or
holding of any asset under or in connection with any Employee Plan has or will
make the Company or any Subsidiary or any director or officer of the Company or
any Subsidiary subject to any liability under Title I of ERISA or liable for any
Tax pursuant to Section 4975 of the Code that could have a Material Adverse
Effect. There are no threatened or pending claims by or on behalf of the
Employee Plans, or by any participant therein, alleging a breach or breaches of
fiduciary duties or violations of Applicable Laws which could result

                                      -19-
<PAGE>

in liability on the part of the Company, its officers or directors, or such
Employee Plans, under ERISA or any other Applicable Law and there is no basis
for any such claim.

     (c)   Each Employee Plan which is intended to be qualified under Section
401(a) of the Code is so qualified and has been so qualified since the date of
its adoption, and each trust forming a part thereof is exempt from Tax pursuant
to Section 501(a) of the Code. Set forth on Schedule 4.18 is a list of the most
                                            -------------
recent IRS determination letters with respect to any such Plans, accurate and
complete copies of which letters have been delivered or made available to Buyer.
Each Employee Plan has been maintained in compliance with its terms and with the
requirements prescribed by all Applicable Laws, including but not limited to
ERISA and the Code, which are applicable to such Employee Plans.

     (d)   Set forth on Schedule 4.18 is a list of each employment, severance,
                        -------------
or other similar contract, arrangement, or policy and each plan or arrangement
(written or oral) providing for insurance coverage (including any self-insured
arrangements), workers' compensation, disability benefits, supplemental
unemployment benefits, vacation benefits, retirement benefits, deferred
compensation, profit-sharing, bonuses, stock options, stock appreciation rights,
or other forms of incentive compensation or post-retirement insurance,
compensation, or benefits which (i) is not an Employee Plan, (ii) is entered
into, maintained, or contributed to, as the case may be, by the Company or any
affiliate of the Company, and (iii) covers any employee or former employee of
the Company or any affiliate of the Company or under which the Company or any
affiliate of the Company has any liability. Such contracts, plans, and
arrangements as are described in the preceding sentence are referred to for
purposes of this Section as the "Benefit Arrangements". Each Benefit Arrangement
has been maintained in substantial compliance with its terms and with the
requirements prescribed by Applicable Laws.

     (e)   Neither the Company nor any affiliate of the Company has performed
any act or failed to perform any act, and there is no contract, agreement, plan,
or arrangement covering any employee or former employee of the Company or any
affiliate of the Company, that, individually or collectively, could give rise to
the payment of any amount that would not be deductible pursuant to the terms of
Section 162(a)(1) or 280G of the Code, or could give rise to any penalty or
excise Tax pursuant to Section 4980B or 4999 of the Code.

     4.19  Agreements.
           ----------

     (a)   Set forth on Schedule 4.19 is a list of all the following agreements,
                        -------------
arrangements, and understandings (written or oral, formal or informal)
(collectively, for purposes of this Section, "agreements") to which the Company
or any Subsidiary is a party or by which the Company or any Subsidiary or any of
their respective properties is otherwise bound:

           (i)    collective bargaining agreements and similar agreements with
     employees as a group;

                                      -20-
<PAGE>

           (ii)   agreements with any current or former shareholder who owns or
     owned 1% or more of the issued and outstanding shares of capital stock of
     such Person or any director, officer, employee, consultant or advisor or
     any affiliate of any such Person;

           (iii)  agreements between or among the Company and any of the
     Subsidiaries;

           (iv)   exclusive of those relating to the Senior Credit Facility,
     indentures, mortgages, security agreements, notes, loan or credit
     agreements, or other agreements relating to the borrowing of money by the
     Company or any Subsidiary or to the direct or indirect guarantee or
     assumption by the Company or any Subsidiary of any obligation of others,
     including any agreement that has the economic effect although not the legal
     form of any of the foregoing;

           (v)    agreements relating to the acquisition or disposition of
     assets, other than those entered into in the ordinary course of business
     consistent with past practice;

           (vi)   agreements relating to the acquisition or disposition of any
     interest in any business enterprise;

           (vii)  exclusive of oil, gas and mineral leases, agreements with
     respect to the lease of real or personal property;

           (viii) exclusive of oil and gas operating or similar agreements,
     agreements concerning the management or operation of any real property;

           (ix)   partnership, joint venture, and profit sharing agreements;

           (x)    agreements with any Governmental Entity;

           (xi)   agreements relating to the release or disposal of Hazardous
     Material;

           (xii)  agreements containing any covenant limiting the freedom of the
     Company or any Subsidiary to engage in any line of business or compete with
     any other Person in any geographic area or during any period of time, other
     than those that would not have a Material Adverse Effect;

           (xiii) agreements not made in the ordinary course of business; and

           (xiv)  other agreements, whether or not made in the ordinary course
     of business, that are material to the business, assets, results of
     operations, condition (financial or otherwise), or prospects of the Company
     and the Subsidiaries considered as a whole.

     (b)   The Company has delivered or made available to Buyer accurate and
complete copies of the agreements listed in Schedule 4.19.  Each of such
                                            -------------
agreements is a valid and binding agreement of the Company and the Subsidiaries
(to the extent each is a party thereto) and (to the best knowledge

                                      -21-
<PAGE>

of the Company) the other party or parties thereto, enforceable against the
Company and the Subsidiaries (to the extent each is a party thereto) and (to the
best knowledge of the Company) such other party or parties in accordance with
its terms. Neither the Company nor any Subsidiary is in breach of or in default
under, nor has any event occurred which (with or without the giving of notice or
the passage of time or both) would constitute a default by the Company or any
Subsidiary under, any of such agreements, and neither the Company nor any
Subsidiary has received any notice from, or given any notice to, any other party
indicating that the Company or any Subsidiary is in breach of or in default
under any of such agreements. To the best knowledge of the Company, no other
party to any of such agreements is in breach of or in default under such
agreements, nor has any assertion been made by the Company or any Subsidiary of
any such breach or default.

     (c)   Neither the Company nor any Subsidiary has received notice of any
plan or intention of any other party to any agreement to exercise any right of
offset with respect to, or any right to cancel or terminate, any agreement, and
neither the Company nor any Subsidiary knows of any fact or circumstance that
would justify the exercise by any such other party of such a right other than
the automatic termination of such agreement in accordance with its terms.
Neither the Company nor any Subsidiary currently contemplates, or has reason to
believe any other Person currently contemplates, any amendment or change to any
agreement, which amendment or change could have a Material Adverse Effect.

     (d)   Without limiting the generality of the other provisions in this
Section 4.19, the Key Employment Agreements are in full force and effect, and
each of John Keenan and Paul Fenemore is currently employed by the Company
pursuant to a renewal term under such agreements.

     4.20  Labor Disputes and Acts of God.  Neither the business nor the
           ------------------------------
properties of the Company nor any Subsidiary has been affected by any fire,
explosion, accident, strike, lockout or other labor dispute, drought, storm,
hail, earthquake, embargo, act of God or of the public enemy or other casualty
(whether or not covered by insurance), which, individually or in the aggregate,
could cause a Material Adverse Effect.

     4.21  Registration Rights.  Except as set forth on Schedule 4.21, the
           -------------------                          -------------
Company has no obligation to register any of its securities under the Securities
Act, the Listing Rules or applicable similar foreign laws or regulations.

     4.22  Offering of Securities. All securities which have been offered or
           ----------------------
or sold by the Company have been registered pursuant to the Securities Act and
applicable foreign and state securities laws or were offered and sold pursuant
to valid exemptions therefrom.

     4.23  Government Regulation.  The Company  is not subject to regulation
           ---------------------
under the Public Utility Holding Company Act of 1935.  The Company is not an
"investment company" or a company "controlled" by an "investment company" within
the meaning of the Investment Company Act of 1940, as amended, or an "investment
advisor" within the meaning of the Investment Advisers Act of 1940, as amended.

                                      -22-
<PAGE>

     4.24  Brokerage Fees.  Neither the Company nor any of its affiliates
           --------------
has retained any financial advisor, broker, agent or finder or paid or agreed to
pay any financial advisor, broker, agent or finder on account of this Agreement
or any transaction contemplated hereby, which action would subject Buyer or any
of its affiliates to any liability. The Company shall indemnify and hold
harmless Buyer from and against any and all losses, claims, damages and
liabilities (including legal and other expenses reasonably incurred in
connection with investigating or defending any claims or actions) with respect
to any finder's fee, brokerage commission or similar payment in connection with
any transaction contemplated hereby asserted by any Person on the basis of any
act or statement made or alleged to have been made by the Company or any of its
affiliates.

     4.25  Solvency.  There are no bankruptcy, reorganization or arrangement
           --------
proceedings pending, being contemplated by, or to the knowledge of Seller,
threatened against Seller.

     4.26  Insurance.  The Company and each Subsidiary carries insurance
           ---------
covering its properties and business adequate and customary for the type and
scope of its properties and business.

     4.27  Full Disclosure.  No representation or warranty made by the Company
           ---------------
Company in this Agreement, and no statement of the Company contained in any
document, certificate or other writing furnished or to be furnished by the
Company or its representatives to Buyer pursuant hereto or in connection
herewith taken as a whole, contains or will contain, at the time of delivery,
any untrue statement of a material fact or omits or will omit, at the time of
delivery, to state any material fact (other than industry-wide risks normally
associated with the type of business conducted by the Company) necessary to make
the statements contained therein, in light of the circumstances in which they
are made, not misleading. There is no fact known to the Company (other than
industry-wide risks normally associated with the type of business conducted by
the Company) that has not been disclosed to Buyer in writing which the Company
reasonably anticipates would result in a Material Adverse Effect.

                                   ARTICLE V

                    REPRESENTATIONS AND WARRANTIES OF BUYER

     Each of EnCap LP, ECIC and El Paso hereby severally and as to itself
represents and warrants to the Company that (as used in this Article V the term
"Buyer" shall be deemed to mean only the person making such representation):

     5.1   Organization.  Buyer is duly organized and validly existing under the
           ------------
laws of the jurisdiction of its formation.

     5.2   Authority Relative to This Agreement.  Buyer has full power and
           ------------------------------------
authority to execute, deliver, and perform this Agreement and the Ancillary
Documents to which it is a party and to consummate the transactions contemplated
hereby and thereby.  The execution, delivery, and performance by Buyer of this
Agreement and the Ancillary Documents to which it is a party, and the

                                      -23-
<PAGE>

consummation by it of the transactions contemplated hereby and thereby, have
been duly authorized by all necessary action of Buyer. This Agreement has been
duly executed and delivered by Buyer and constitutes, and each Ancillary
Document executed or to be executed by Buyer has been, or when executed will be,
duly executed and delivered by Buyer and constitutes, or when executed and
delivered will constitute, a valid and legally binding obligation of Buyer,
enforceable against Buyer in accordance with their respective terms, except that
such enforceability may be limited by (i) applicable bankruptcy, insolvency,
reorganization, moratorium, and similar laws affecting creditors' rights
generally and (ii) equitable principles which may limit the availability of
certain equitable remedies (such as specific performance) in certain instances.

     5.3  Investment Intent; Investment Experience; Restricted Securities.
          ---------------------------------------------------------------
Buyer is acquiring the Securities for its own account for investment and not
with a view to, or for sale or other disposition in connection with, any
distribution of all or any part thereof. In acquiring the Securities, Buyer is
not offering or selling, and will not offer or sell, for the Company in
connection with any distribution of the Securities, and Buyer does not have a
participation and will not participate in any such undertaking or in any
underwriting of such an undertaking except in compliance with applicable federal
and state securities laws. Buyer acknowledges that it is able to fend for
itself, can bear the economic risk of its investment in the Securities, and has
such knowledge and experience in financial and business matters that it is
capable of evaluating the merits and risks of an investment in the Securities.
Buyer understands that the Securities will not have been registered pursuant to
the Securities Act or any applicable state securities laws, that the Securities
will be characterized as a "restricted security" under federal securities laws
and that under such laws and applicable regulations the Securities cannot be
sold or otherwise disposed of without registration under the Securities Act or
an exemption therefrom.

     5.4  Brokerage Fees.  Neither Buyer nor any of its affiliates has retained
          --------------
any financial advisor, broker, agent or finder or paid or agreed to pay any
financial advisor, broker, agent or finder on account of this Agreement or any
transaction contemplated hereby, which action would subject the Company or any
of its affiliates to any liability.  Buyer shall indemnify and hold harmless the
Company from and against any and all losses, claims, damages and liabilities
(including legal and other expenses reasonably incurred in connection with
investigating or defending any claims or actions) with respect to any finder's
fee, brokerage commission or similar payment in connection with any transaction
contemplated hereby asserted by any Person on the basis of any act or statement
made or alleged to have been made by Buyer or any of its affiliates.

                                  ARTICLE VI

                      CONDUCT OF COMPANY PENDING CLOSING

     The Company hereby covenants and agrees with Buyer that except as expressly
provided in this Agreement, during the period from the date hereof to the
Closing, the Company and the Subsidiaries (a) shall each conduct its operations
according to its ordinary course of business consistent with past practice and
in compliance with all Applicable Laws; (b) shall each use its

                                      -24-
<PAGE>

reasonable best efforts to preserve, maintain and protect its properties; and
(c) shall each use its reasonable best efforts to preserve intact its business
organization, to keep available the services of its officers and employees, and
to maintain existing relationships with licensors, licensees, suppliers,
contractors, distributors, customers and others having business relationships
with it.

                                  ARTICLE VII

                   CONDITIONS TO OBLIGATIONS OF THE COMPANY

     The obligations of the Company to consummate the transactions contemplated
by this Agreement shall be subject to the fulfillment on or prior to the Closing
Date of each of the following conditions:

     7.1  Representations and Warranties True.  All the representations and
          -----------------------------------
warranties of Buyer contained in this Agreement, and in any agreement,
instrument or document delivered pursuant hereto or in connection herewith on or
prior to the Closing Date, shall be true and correct in all material respects on
and as of the Closing Date as if made on and as of such date, except as affected
by transactions permitted by this Agreement, and except to the extent that any
such representation or warranty is made as of a specified date, in which case
such representation or warranty shall have been true and correct in all material
respects as of such specified date.  For the sole purpose of determining whether
or not any of such representations and warranties are true and correct as
aforesaid on and as of the Closing Date, no effect shall be given to any
materiality qualification contained in such representation or warranty.

     7.2  Covenants and Agreements Performed.  Buyer shall have performed and
          ----------------------------------
complied with in all material respects all covenants and agreements required by
this Agreement to be performed or complied with by it on or prior to the Closing
Date, and all deliveries contemplated by Section 3.3 shall have been made.

     7.3  HSR Act.  All waiting periods (and any extensions thereof) applicable
          -------
to this Agreement and the transactions contemplated hereby under the HSR Act
shall have expired or been terminated.

     7.4  Legal Proceedings.  No preliminary or permanent injunction or other
          -----------------
order, decree or ruling issued by a Governmental Entity or any securities
exchange, and no statute, rule, regulation or executive order promulgated,
enacted or issued by a Governmental Entity or any securities exchange, shall be
in effect which restrains, enjoins, prohibits or otherwise makes illegal or
improper the consummation of the transactions contemplated hereby.

                                 ARTICLE VIII

                      CONDITIONS TO OBLIGATIONS OF BUYER

                                      -25-
<PAGE>

     The obligations of Buyer to consummate the transactions contemplated by
this Agreement shall be subject to the fulfillment on or prior to the Closing
Date of each of the following conditions:

     8.1  Representations and Warranties True.  All the representations and
          -----------------------------------
warranties of the Company contained in this Agreement, and in any agreement,
instrument or document delivered pursuant hereto or in connection herewith on or
prior to the Closing Date, shall be true and correct in all material respects on
and as of the Closing Date as if made on and as of such date, and except to the
extent that any such representation or warranty is made as of a specified date,
in which case such representation or warranty shall have been true and correct
in all material respects as of such specified date. For the sole purpose of
determining whether or not any of such representations and warranties are true
and correct as aforesaid on and as of the Closing Date, no effect shall be given
to any materiality qualification contained in such representation or warranty.

     8.2  Covenants and Agreements Performed.  The Company shall have performed
          ----------------------------------
and complied with in all material respects all covenants and agreements required
by this Agreement to be performed or complied with by it on or prior to the
Closing Date, and all deliveries contemplated by Section 3.2 shall have been
made.

     8.3  HSR Act.  All waiting periods (and any extensions thereof) applicable
          -------
to this Agreement and the transactions contemplated hereby under the HSR Act
shall have expired or been terminated.

     8.4  Legal Proceedings.  No preliminary or permanent injunction or other
          -----------------
order, decree or ruling issued by a Governmental Entity or any securities
exchange, and no statute, rule, regulation or executive order promulgated,
enacted or issued by a Governmental Entity or any securities exchange, shall be
in effect which restrains, enjoins, prohibits or otherwise makes illegal the
consummation of the transactions contemplated hereby.

     8.5  Consents.  There shall have been obtained any and all consents,
          --------
approvals, authorizations, licenses, orders or permits set forth on Schedule
                                                                    --------
4.7; and no other consent, approval, authorization, license, order or permit of,
---
or declaration, filing or registration with, or notification to, any
Governmental Entity, or any other Person or entity, the failure to comply with
which would have a Material Adverse Effect, shall be required to be made or
obtained by the Company or any Subsidiary in connection with the execution,
delivery and performance of this Agreement and the consummation of the
transactions contemplated hereby.

     8.6  No Material Adverse Change.  Since the date of this Agreement, there
          --------------------------
shall not have been any material adverse change in the business, assets, results
of operations, condition (financial or otherwise) or prospects of the Company
and the Subsidiaries considered as a whole.

     8.7  Subordination Agreement.  Buyer and the lender under the Senior Credit
          -----------------------
Facility shall have executed and delivered a mutually acceptable subordination
agreement.

                                      -26-
<PAGE>

      8.8   Registration Rights Agreement.  The Company and the other parties to
            -----------------------------
the Registration Rights Agreement shall have executed and delivered such
agreement.

      8.9.  Closing of the Senior Credit Facility.  All conditions precedent to
            -------------------------------------
the closing of the Senior Credit Facility (other than transactions with respect
to the consummation, simultaneously with such closing, of the transactions
contemplated hereby) shall have been satisfied at or prior to the Closing, and
such closings shall have occurred prior to or be occurring simultaneously with
the Closing.

                                  ARTICLE IX

                            PRE-CLOSING TERMINATION

      9.1   Termination.  This Agreement may be terminated and the transactions
            -----------
contemplated hereby abandoned at any time prior to the Closing in the following
manner:

            (a)  by mutual written consent of the Company and Buyer; or

            (b)  by either the Company or Buyer, if any Governmental Entity with
      jurisdiction over such matters shall have issued an order or injunction
      restraining, enjoining or otherwise prohibiting the issuance of the Notes
      hereunder and such order, decree, ruling or other action shall have become
      final and unappealable;

            (c)  by either Company or Buyer, if the Closing shall not have
      occurred on or before May 30, 2000; provided, however, that the right to
      terminate this Agreement under this Section 9.1(c) shall not be available
      to any party whose failure to fulfill any obligation under this Agreement
      shall have been the cause of, or shall have resulted in, the failure of
      the Closing to occur prior to such date.

      9.2   Effect of Termination.  In the event of the termination of this
            ---------------------
Agreement pursuant to Section 9.1 by the Company, on the one hand, or Buyer, on
the other, written notice thereof shall forthwith be given to the other party
specifying the provision hereof pursuant to which such termination is made, and
this Agreement shall become void and have no effect, except that the agreements
contained in this Section, in Sections 14.4 and 14.5 and in Article XV shall
survive the termination hereof.  Nothing contained in this Section shall relieve
any party from liability for damages actually incurred as a result of any breach
of this Agreement.

                                   ARTICLE X

                     AFFIRMATIVE COVENANTS OF THE COMPANY

                                      -27-
<PAGE>

      To induce Buyer to enter into this Agreement, the Company warrants,
covenants and agrees that until the full and final payment of the Obligations:

      10.1  Payment and Performance.  The Company will pay all amounts due under
            -----------------------
the Notes in accordance with the terms thereof and will observe, perform and
comply with every covenant, term and condition expressed or implied in this
Agreement. The Company will cause each of its Subsidiaries to observe, perform
and comply with every such term, covenant and condition to the extent applicable
to such Subsidiary.

      10.2  Books, Financial Statements and Reports.  The Company and each of
            ---------------------------------------
its Subsidiaries will at all times maintain full and accurate books of account
and records.  The Company will maintain and will cause its Subsidiaries to
maintain a standard system of accounting, will maintain its Fiscal Year, and
will furnish the following statements and reports to Buyer at the Company's
expense:

      (a)   As soon as available, and in any event within one hundred five (105)
days after the end of each Fiscal Year, complete consolidated financial
statements of the Company together with all notes thereto, prepared in
reasonable detail in accordance with U.S. GAAP, together with an unqualified
opinion, based on an audit using generally accepted auditing standards, by
independent certified public accountants selected by the Company and reasonably
acceptable to Buyer, stating that such consolidated financial statements have
been so prepared.  These financial statements shall contain a consolidated
balance sheet as of the end of such Fiscal Year and consolidated statements of
earnings, of cash flows, and of changes in owners' equity for such Fiscal Year,
each setting forth in comparative form the corresponding figures for the
preceding Fiscal Year.

      (b)   As soon as available, and in any event within fifty (50) days after
the end of each Fiscal Quarter, the Company's consolidated balance sheet as of
the end of such Fiscal Quarter and consolidated statements of the Company's
earnings and cash flows for the period from the beginning of the then current
Fiscal Year to the end of such Fiscal Quarter, all in reasonable detail and
prepared in accordance with U.S. GAAP, subject to changes resulting from normal
year-end adjustments. In addition the Company will, together with each such set
of financial statements and each set of financial statements furnished under
subsection (a) of this section, furnish a certificate in a form reasonably
acceptable to Buyer signed by the chief financial officer of the Company stating
that such financial statements are accurate and complete (subject to normal
year-end adjustments) and stating that no Default exists at the end of such
Fiscal Quarter or at the time of such certificate or specifying the nature and
period of existence of any such Default.

      (c)   Promptly upon their becoming available, copies of all financial
statements, reports, notices and proxy statements sent by the Company to its
stockholders and all registration statements, periodic reports and other
statements and schedules filed by the Company with any securities exchange, the
Securities and Exchange Commission or any similar Governmental Entity.

      (d)   Annually within 60 days after the end of each Fiscal Year beginning
with the Fiscal Year ending April 30, 2000, a report containing (i) an
estimation of the oil and gas reserves, classified by appropriate categories, as
of the end of the preceding fiscal year attributable to the interest of the

                                      -28-
<PAGE>

Company therein, (ii) a projection of the rate of production of and net income
from such reserves with respect to each such interest, (iii) a calculation of
the present worth of such net income discounted at a rate of 10% and at any
other rates designated from time to time by a Majority of the Noteholders and
(iv) a schedule or complete description of all assumptions, estimates and
projections made or used in the preparation of such report.  Each such report
shall be prepared in accordance with customary and generally accepted standards
and practices for petroleum engineers, and shall be based on (1) prices
determined by a Majority of the Noteholders, (2) lease operating expenses and
production taxes derived from and consistent with those actually incurred by the
Company, escalated at the same rate, if any, being applied to prices and (3)
such other assumptions as shall be designated by a Majority of the Noteholders.
In addition to the foregoing, a Majority of the Noteholders shall have the right
from time to time to cause the independent petroleum engineer referenced below
to prepare an additional report of the type described above, not to exceed one
additional report in any one calendar year, in which event all fees and expenses
incurred in connection with obtaining such additional report shall be paid by
the Company. Each report under this subsection shall be prepared by an
independent petroleum engineer designated by the Company and approved by a
Majority of the Noteholders  Each annual report referenced above shall also
include an estimate of the Company's proved oil and gas reserves (as defined in
Regulation S-X promulgated by the Securities and Exchange Commission) and a
calculation of the "present value of estimated future net revenues" from such
proved oil and gas reserves, with such present worth calculation to be made in
accordance with Regulation S-X, as promulgated by the Securities and Exchange
Commission.

      (e)   Promptly, such other information with respect to the business and
operations of the Company and its Subsidiaries, as Buyer may reasonably request.

      10.3  Notice of Material Events and Change of Address.  The Company
            -----------------------------------------------
will promptly notify Buyer in writing, stating that such notice is being given
pursuant to this Agreement, of:

            (a)  the occurrence of any Material Adverse Effect,

            (b)  the occurrence of any Default,

            (c)  the acceleration of the maturity of any indebtedness owed by
      the Company or any Subsidiary thereof or of any default by any the Company
      or any such Subsidiary under any indenture, mortgage, agreement, contract
      or other instrument to which any of them is a party or by which any of
      them or any of their properties is bound, if such acceleration or default
      could reasonably be expected to have a Material Adverse Effect,

            (d)  any claim of $250,000 or more, any notice of potential
      liability under any Environmental Laws which might exceed such amount, or
      any other material adverse claim asserted against the Company or any
      Subsidiary thereof or with respect to the Company or any of such
      Subsidiary's properties, and

            (e)  the filing of any suit or proceeding against the Company or any
      Subsidiary thereof in which an adverse decision could cause a Material
      Adverse Effect.

                                      -29-
<PAGE>

Upon the occurrence of any of the foregoing the Company and any Subsidiary
thereof will take all necessary or appropriate steps to remedy promptly any such
Material Adverse Effect, Default, acceleration or default, to protect against
any such adverse claim, to defend any such suit or proceeding, and to resolve
all controversies on account of any of the foregoing.

      10.4  Maintenance of Properties.  The Company and each of its Subsidiaries
            -------------------------
will maintain, preserve, protect, and keep all property used or useful in the
conduct of its business in good condition and in compliance with all Applicable
Laws, and will from time to time make all repairs, renewals and replacements
needed to enable the business and operations carried on in connection therewith
to be promptly and advantageously conducted at all times.

      10.5  Maintenance of Existence and Qualifications.  The Company and each
            -------------------------------------------
of its Subsidiaries will maintain and preserve its existence and its rights and
franchises in full force and effect and will qualify to do business in all
states or jurisdictions where required by Applicable Law, except where the
failure so to qualify will not cause a Material Adverse Effect.

      10.6  Payment of Trade Liabilities, Taxes, etc.  The Company and each of
            -----------------------------------------
its Subsidiaries will (a) timely file all required Tax Returns; (b) timely pay
all Taxes, assessments, and other governmental charges or levies imposed upon it
or upon its income, profits or property; (c) timely withhold and pay over to the
proper Governmental Entity all amounts required to be withheld and paid over
under Applicable Laws; (d) pay when due all Liabilities owed by it on ordinary
trade terms to vendors, suppliers and other Persons providing goods and services
used by it in the ordinary course of its business; (e) pay and discharge when
due all other Liabilities now or hereafter owed by it; and (f) maintain
appropriate accruals and reserves for all of the foregoing in accordance with
U.S. GAAP. The Company and each of its Subsidiaries may, however, delay paying
or discharging any of the foregoing so long as it is in good faith contesting
the validity thereof by appropriate proceedings and has set aside on its books
adequate reserves therefor.

      10.7  Insurance.  The Company and each of its Subsidiaries will keep or
            ---------
cause to be kept insured by financially sound and reputable insurers its
properties in such forms and amounts and against such risks as are customary for
Persons engaged in the same or similar business of owning and operating similar
properties.

      10.8  Compliance with Agreements and Law.  The Company and each of its
            ----------------------------------
Subsidiaries will perform all material obligations it is required to perform
under the terms of each indenture, mortgage, deed of trust, security agreement,
lease, franchise, agreement, contract or other instrument or obligation to which
it is a party or by which it or any of its properties is bound. The Company and
each of its Subsidiaries will conduct its business and affairs in compliance
with all Applicable Law.

      10.9  Guaranties of Company's Subsidiaries.  Each Subsidiary (other than
            ------------------------------------
the Subsidiary Guarantors) of the Company now existing or created, acquired or
coming into existence after the date hereof shall, promptly upon request by
Buyer, execute and deliver to Buyer an absolute and unconditional guaranty of
the timely repayment of the Notes and the due and punctual performance of the
obligations of the Company hereunder, which guaranty shall be satisfactory to
Buyer in form

                                      -30-
<PAGE>

and substance. The Company will cause each of its Subsidiaries to deliver to
Buyer, simultaneously with its delivery of such a guaranty, written evidence
satisfactory to Buyer and its counsel that such Subsidiary has taken all
corporate or partnership action necessary to duly approve and authorize its
execution, delivery and performance of such guaranty and any other documents
which it is required to execute.

      10.10  Inspection Rights. At any reasonable time and from time to time
             -----------------
upon reasonable notice, the Company will permit Buyer or its agents or
representatives to examine and make copies of and extracts from the records and
books of account of, and visit and inspect the properties of the Company and any
Subsidiary, and to discuss the affairs, finances and accounts of the Company and
any Subsidiary with any of their officers or directors and independent
accountants.

      10.11  Charter Amendment Approval.  The Company shall cause the Charter
             --------------------------
Amendment Approval by September 30,2000.

                                  ARTICLE XI

                       NEGATIVE COVENANTS OF THE COMPANY

      To induce Buyer to enter into this Agreement, the Company warrants,
covenants and agrees that until the full and final payment of the Obligations:

      11.1   Indebtedness.  Neither the Company nor any Subsidiary thereof will
             ------------
in any manner owe or be liable for Indebtedness except:

      (a)  the Obligations;

      (b)  the Senior Credit Facility;

      (c)  Indebtedness owed by the Company or any Subsidiary thereof which is
subordinated to the Obligations upon terms and conditions satisfactory to the
holder(s) of the Notes in its (or their) sole and absolute discretion;

      (d)  purchase money Indebtedness and Indebtedness under leases of the
Company or such Subsidiary as lessee which are capitalized in accordance with
U.S. GAAP, in an aggregate principal amount not to exceed $250,000 at any time,
provided that such purchase money Indebtedness and Indebtedness under capital
leases do not in the aggregate exceed $500,000;

      (e)  gas overproduction or liabilities arising under futures contracts,
forward contracts, swap, cap or collar contracts, option contracts, hedging
contracts, other derivative contracts or similiar contracts, to the extent
permitted by the Senior Credit Facility; and

                                      -31-
<PAGE>

      (f)   Old Latex Payables.

      11.2  Limitation on Liens.  Neither the Company nor any Subsidiary thereof
            -------------------
will create, assume or permit to exist any Lien upon any of the properties or
assets which it now owns or hereafter acquires, except the following ("Permitted
Liens"):

      (a)   Liens which secure Obligations only;

      (b)   Liens which secure the Senior Credit Facility; and

      (c)   Statutory Liens for taxes, statutory mechanics' and materialmen's
Liens incurred in the ordinary course of business, and other similar Liens
incurred in the ordinary course of business, provided such Liens do not secure
Indebtedness or secure only Indebtedness which is not delinquent or for which
adequate reserves have been set aside.

      11.3  Limitation on Mergers.  Except as expressly provided in this
            ---------------------
Section, neither the Company nor any Subsidiary thereof will merge or
consolidate with or into any other business entity. Any Subsidiary of the
Company may, however, be merged into or consolidated with either the Company or
another Subsidiary which is wholly-owned by the Company, so long as the Company
or the Subsidiary wholly-owned by the Company is the surviving business entity.
The Company will not issue any securities other than (i) Common Stock or (ii)
any options or warrants giving the holders thereof only the right to acquire
such shares.  No Subsidiary of the Company will issue any additional shares of
its capital stock or other securities or any options, warrants or other rights
to acquire such additional shares or other securities except to the Company or
to another Subsidiary. No Subsidiary of the Company which is a partnership will
allow any diminution of the Company's interest (direct or indirect)  therein.

      11.4  Limitation on Sales of Property.  Neither the Company nor any
            -------------------------------
Subsidiary thereof will sell, transfer, lease, exchange, alienate or dispose of
any of its assets or properties except:

      (a)   equipment which is worthless or obsolete or which is replaced by
equipment of equal suitability and value;

      (b)   inventory (including oil and gas sold as produced and seismic data)
which is sold in the ordinary course of business on ordinary trade terms; or

      (c)   other property which is sold for fair consideration not in the
aggregate in excess of $500,000 in any Fiscal Year (commencing with Fiscal Year
1999).

      11.5  Limitation on Investments and New Businesses.  Neither the Company
            --------------------------------------------
nor any Subsidiary thereof will make any expenditure or commitment or incur any
obligation or enter into or engage in any transaction except in the ordinary
course of business (which ordinary course of business includes the acquisition,
directly or indirectly, of oil and gas properties), engage directly or
indirectly

                                      -32-
<PAGE>

in any business or conduct any operations except in connection with or
incidental to its present businesses and operations, make any acquisitions of or
capital contributions to or other investments in any Person, other than
Permitted Investments, or make any significant acquisitions or investments in
any properties other than oil and gas properties.

      11.6  Transactions with Affiliates.  Neither the Company nor any of its
            ----------------------------
Subsidiaries will engage in any material transaction with any of its affiliates
on terms which are less favorable to it than those which would have been
obtainable at the time in arm's-length dealing with Persons other than such
affiliates.

      11.7  Restricted Payments.  The Company will not, and will not permit
            -------------------
any of its Subsidiaries to, declare or make, or incur any liability to declare
or make, any Restricted Payment.

                                  ARTICLE XII

                            PREPAYMENT OF THE NOTES

      At any time on or after January 1, 2001, the Company may, upon not less
than thirty days' notice to the holders of the Notes, from time to time and
without premium or penalty prepay the Notes in cash, in whole or in part, so
long as the aggregate amount of each partial prepayment of principal on the
Notes equals at least $1,000,000 or any higher integral multiple of $1,000,000.
Each prepayment of principal under this Section 12.1 shall be accompanied by all
interest then accrued and unpaid on the principal so prepaid.  All principal and
interest prepaid pursuant to this Section 12.1 shall be in addition to, but not
in lieu of, all payments otherwise required to be paid under the Agreement or
the Ancillary Documents at the time of such prepayment.  Any prepayments made
under this Article XII shall be applied against each Note outstanding pro rata,
based upon the ratio that the then outstanding principal amount of a Note bears
to the then total outstanding principal amount of all of the Notes.

                                 ARTICLE XIII

                        EVENTS OF DEFAULT AND REMEDIES

      13.1  Events of Default.  Each of the following constitutes an "Event of
            -----------------
Default" for purposes of the Notes and this Agreement:

      (a)   a default in the payment of principal of any Note when and as the
same shall become due and payable;

      (b)   a default in the payment of any interest upon any Note when such
interest becomes due and payable;

                                      -33-
<PAGE>

      (c)  a default in the performance or observation of any covenant,
agreement or condition contained in either Article X or Article XI, which
                                           ---------    ----------
default is not remedied within 30 days after the earlier of (i) the day on which
the Company first obtains knowledge of such default or (ii) the day on which
written notice thereof is given to the Company by the holder of any Note;

      (d)  any "default" or "event of default" occurs under any this Agreement
or any Ancillary Document which defines either such term, and the same is not
remedied within the applicable period of grace (if any) provided in this
Agreement or such Ancillary Document;

      (e)  any representation or warranty previously, presently or hereafter
made in writing by or on behalf of the Company or any Subsidiary thereof in
connection with this Agreement or any Ancillary Document shall prove to have
been false or incorrect in any material respect on any date on or as of which
made, which default is not remedied within 30 days after the earlier of (i) the
day on which the Company first obtains knowledge of such default or (ii) the day
on which written notice thereof is given to the Company by the holder of any
Note;

      (f)  the Company or any Subsidiary fails to duly observe, perform or
comply with any agreement with any Person or any term or condition of any loan
document relating to the Senior Credit Facility or any other agreement or
instrument, if such agreement or instrument is materially significant to the
Company or such Subsidiary, and such failure is not remedied within the
applicable period of grace (if any) provided in such agreement or instrument;

      (g)  the Company or any Subsidiary thereof fails to pay any portion, when
such portion is due, of any of its Indebtedness in excess of $250,000 (exclusive
of the Old Latex Payables), or breaches or defaults in the performance of any
Agreement or instrument by which any such Indebtedness is issued, evidenced,
governed, or secured, and any such failure, breach or default continues beyond
any applicable period of grace provided therefor;

      (h)  the Company or any Subsidiary thereof:

           (i)  suffers the entry against it of a judgment, decree or order for
      relief by a tribunal of competent jurisdiction in an involuntary
      proceeding commenced under any applicable bankruptcy, insolvency or other
      similar Applicable Law of any jurisdiction now or hereafter in effect,
      including the United States federal Bankruptcy Code or similar foreign
      law, as from time to time amended, or has any such proceeding commenced
      against it which remains undismissed for a period of thirty days; or

           (ii) commences a voluntary case under any applicable bankruptcy,
      insolvency or similar Applicable Law now or hereafter in effect, including
      the United States federal Bankruptcy Code or similar foreign law, as from
      time to time amended; or applies for or consents to the entry of an order
      for relief in an involuntary case under any such Applicable Law; or makes
      a general assignment for the benefit of creditors; or fails

                                      -34-
<PAGE>

      generally to pay (or admits in writing its inability to pay) its debts as
      such debts become due; or takes corporate or other action to authorize any
      of the foregoing; or

            (iii)  suffers the appointment of or taking possession by a
      receiver, liquidator, assignee, custodian, trustee, sequestrator or
      similar official of all or a substantial part of its assets in a
      proceeding brought against or initiated by it, and such appointment or
      taking possession is neither made ineffective nor discharged within thirty
      days after the making thereof, or such appointment or taking possession is
      at any time consented to, requested by, or acquiesced to by it; or

            (iv)   suffers the entry against it of a final judgment for the
      payment of money in excess of $250,000 (not covered by insurance
      satisfactory to the holder of the Notes in their sole discretion), unless
      the same is discharged within thirty days after the date of entry thereof
      or an appeal or appropriate proceeding for review thereof is taken within
      such period and a stay of execution pending such appeal is obtained; or

            (v)    suffers a writ or warrant of attachment or any similar
      process to be issued by any tribunal against all or any substantial part
      of its assets, and such writ or warrant of attachment or any similar
      process is not stayed or released within thirty days after the entry or
      levy thereof or after any stay is vacated or set aside;

      (i)   Any Change in Control occurs; and

      (j)   Any Material Adverse Effect occurs.

Upon the occurrence of an Event of Default described in subsection (h)(i),
(h)(ii) or (h)(iii) of this section with respect to the Company or a Subsidiary
thereof, all of the Obligations shall thereupon be immediately due and payable,
without demand, presentment, notice of demand or of dishonor and nonpayment,
protest, notice of protest, notice of intention to accelerate, declaration or
notice of acceleration, or any other notice or declaration of any kind, all of
which are hereby expressly waived by the Company and each such Subsidiary.  Upon
the occurrence of an Event of Default described in subsection (a) or subsection
(b) of this section, any holder of a Note may during its continuance, by written
notice to the Company, declare the Note held by it to be due and payable,
whereupon such Note shall forthwith mature and become due and payable.  Upon the
occurrence of any other Event of Default, the Majority of the Noteholders may at
any time during its continuance, declare all of the Notes to be due and payable,
whereupon all of the Notes shall forthwith mature and become due and payable.

      13.2  Remedies.  If any Default shall occur and be continuing, the
            --------
holder of any Note may protect and enforce its rights under the this Agreement
and the Ancillary Documents by any appropriate proceedings, including
proceedings for specific performance of any covenant or agreement contained in
this Agreement or any Ancillary Document, and the holder of any Note may enforce
the payment of any Obligations due it or enforce any other legal or equitable
right

                                      -35-
<PAGE>

which it may have. All rights, remedies and powers conferred upon the holder of
the Notes under this Agreement and the Ancillary Documents shall be deemed
cumulative and not exclusive of any other rights, remedies or powers available
under this Agreement or the Ancillary Documents or at law or in equity.

                                  ARTICLE XIV

                             ADDITIONAL AGREEMENTS

      14.1  Third Party Consents.  The Company shall use its reasonable best
            --------------------
efforts to obtain all consents, approvals, orders, authorizations, and waivers
of, and to effect all declarations, filings, and registrations with, all third
parties (including Governmental Entities) that are necessary, required, or
deemed by Buyer to be desirable to enable the Company to issue the Notes to
Buyer as contemplated by this Agreement and to otherwise consummate the
transactions contemplated hereby. All costs and expenses of obtaining or
effecting any and all of the consents, approvals, orders, authorizations,
waivers, declarations, filings, and registrations referred to in this Section
shall be borne by the Company.

      14.2  Access to Information.  Between the date hereof and the Closing,
            ---------------------
the Company (i) shall give Buyer and its authorized representatives reasonable
access, during regular business hours, to all employees, all plants, offices,
warehouses, and other facilities, and all books and records, including work
papers and other materials prepared by the Company's independent public
accountants, of the Company and the Subsidiaries, (ii) shall permit Buyer and
its authorized representatives to make such inspections as they may reasonably
require and (iii) shall cause the Company's officers and those of the
Subsidiaries to furnish Buyer and its authorized representatives with such
financial and operating data and other information with respect to the Company
and the Subsidiaries as Buyer may from time to time reasonably request;
provided, however, that the Company shall have the right to have a
representative present at all times of any such inspections, interviews and
examinations conducted at or on the offices or other facilities or properties of
the Company or its affiliates or representatives.

      14.3  Use of Proceeds.  The Company will use the Purchase Price for
            ---------------
general corporate purposes.

      14.4  Public Announcements.  Except as may be required by Applicable
            --------------------
Law, neither Buyer, on the one hand, nor the Company, on the other, shall issue
any press release or otherwise make any public statement with respect to this
Agreement or the transactions contemplated hereby without the prior written
consent of the other party (which consent shall not be unreasonably withheld).
Any such press release or public statement required by Applicable Law shall only
be made after reasonable notice to the other party, and in such case the party
proposing to make such a press release or public statement shall consult with
the other party.

                                      -36-
<PAGE>

      14.5  Fees and Expenses.  The Company shall bear its costs and expenses
            -----------------
in connection with the negotiation, preparation, execution and delivery of this
Agreement and the Ancillary Documents and the other documents and instruments
contemplated hereby and thereby, as well as the consummation of the transactions
contemplated hereby and thereby.  The Company shall promptly (and in any event
within 30 days after any invoice or other statement or notice) pay the
reasonable costs and expenses incurred by or on behalf of Buyer, including
attorneys' fees, consultants' fees and engineering fees, travel costs and
miscellaneous expenses in connection with the negotiation, preparation,
execution and delivery of this Agreement and the Ancillary Documents and the
other documents and instruments contemplated hereby and thereby, as well as the
related due diligence and consummation of the transactions contemplated hereby
and thereby.

      14.6  Costs of Enforcement.  If any party hereto is required to take
            --------------------
action to enforce its rights under this Agreement, the prevailing party shall be
entitled to its reasonable expenses, including attorneys' fees and expenses, in
connection with any such action.

      14.7  Indemnification.  The Company shall indemnify, defend and hold
            ---------------
harmless Buyer from and against any and all claims, actions, causes of action,
demands, assessments, losses, damages, liabilities, judgments, settlements,
penalties, costs and expenses (including reasonable attorneys' fees and
expenses), of any nature whatsoever, asserted against, resulting to, imposed
upon, or incurred by Buyer, directly or indirectly, by reason of or resulting
from any breach by the Company of any of its representations, warranties,
covenants or agreements contained in this Agreement or in any certificate,
instrument or document delivered pursuant hereto.

                                  ARTICLE XV

                                 MISCELLANEOUS

      15.1  Notices.  All notices, requests, demands, and other communications
            -------
required or permitted to be given or made hereunder by any party hereto shall be
in writing and shall be deemed to have been duly given or made if (a) delivered
personally, (b) transmitted by first class registered or certified mail, postage
prepaid, return receipt requested, (c) sent by prepaid overnight courier
service, or (d) sent by telecopy or facsimile transmission, answer back
requested, to the parties at the following addresses (or at such other addresses
as shall be specified by the parties by like notice):

                                      -37-
<PAGE>

          If to EnCap LP or ECIC:

               c/o EnCap Investments L.L.C.
               1100 Louisiana, Suite 3150
               Houston, Texas  77002
               Attention:  Robert L. Zorich
               Fax No.:  713-659-6130

          If to El Paso:

               c/o El Paso Energy Corporation
               1001 Louisiana Street
               Houston, Texas  77002
               Attention:  Bob Baker
               Fax No.: 713-420-2813

          with a copy to:

               Thompson Knight Brown Parker & Leahy LLP
               1200 Smith, Suite 3600
               Houston, TX  77002
               Attention:  Michael K. Pierce
               Telefax: 713-217-2828

          If to the Company or any Subsidiary:

               AROC Inc.
               4200 East Skelly Drive, Suite 1000
               Tulsa, Oklahoma  74135
               Attention:  John A. Keenan
               Telefax: 918-494-4918

          with a copy to:

               Jenkens & Gilchrist, a Professional Corporation
               1445 Ross Avenue, Suite 3200
               Dallas, Texas  75202
               Attention: W. Alan Kailer
               Telefax: 214-855-4300

Such notices, requests, demands, and other communications shall be effective (i)
if delivered personally or sent by courier service, upon actual receipt by the
intended recipient, (ii) if mailed, upon the earlier of five days after deposit
in the mail or the date of delivery as shown by the return receipt

                                      -38-
<PAGE>

therefor or (iii) if sent by telecopy or facsimile transmission, when the answer
back is received.

      15.2  Waiver and Amendment.  No failure or delay (whether by course of
            --------------------
conduct or otherwise) by any party hereto in exercising any right, power or
remedy which such holder may have under the Agreement or any of the Ancillary
Documents shall operate as a waiver thereof or of any other right, power or
remedy, nor shall any single or partial exercise thereof preclude any other or
further exercise thereof or of any other right, power or remedy.  No waiver of
any provision of this Agreement or any Ancillary Document and no consent to any
departure therefrom shall ever be effective unless it is in writing and signed
as provided below in this section, and then such waiver or consent shall be
effective only in the specific instances and for the purposes for which given
and to the extent specified in such writing.  No waiver, consent, release,
modification or amendment of or supplement to this Agreement or any of the
Ancillary Documents shall be valid or effective against any party hereto unless
the same is in writing and signed by such party.

      15.3  Survival.  The representations and warranties of the parties hereto
            --------
contained in this Agreement or in any certificate, instrument or document
delivered pursuant hereto shall survive the Closing, regardless of any
investigation made by or on behalf of any party without contractual limitation.
Except as otherwise provided herein or therein, all agreements and/or covenants
of the Company contained in this Agreement or in any of the Ancillary Documents
shall survive the execution and delivery of this Agreement and the Ancillary
Documents and the performance hereof and thereof, and shall further survive
until all of the Obligations are paid in full and all of Buyer's obligations to
the Company are terminated.

      15.4  Entire Agreement.  This Agreement, together with the Schedules and
            ----------------
other writings referred to herein or delivered pursuant hereto, constitute the
entire agreement between the parties hereto with respect to the subject matter
hereof and supersede all prior agreements and understandings, both written and
oral, between the parties with respect to the subject matter hereof.

      15.5  Binding Effect; Assignment; No Third Party Benefit.  This Agreement
            --------------------------------------------------
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns; provided, however, that prior to Closing,
neither party may assign its rights or delegate any of its duties and
obligations under this Agreement or the Ancillary Documents without the prior
written consent of the other; provided, further, that after the Closing, the
Company may not assign its rights or delegate any of its duties and obligations
under this Agreement and the Ancillary Documents without the prior written
consent of the holder of the Notes. Except as expressly provided herein, nothing
in this Agreement, express or implied, is intended to or shall confer upon any
Person other than the parties hereto, and their respective successors and
permitted assigns, any rights, benefits, or remedies of any nature whatsoever
under or by reason of this Agreement.

      15.6  Severability.  If any provision of this Agreement is held to be
            ------------
unenforceable, this Agreement shall be considered divisible and such provision
shall be deemed inoperative to the extent it is deemed unenforceable, and in all
other respects this Agreement shall remain in full force and effect; provided,
however, that if any such provision may be made enforceable by limitation
thereof, then such provision shall be deemed to be so limited and shall be
enforceable to the maximum extent

                                      -39-
<PAGE>

permitted by Applicable Law.

      15.7   GOVERNING LAW.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED
             -------------
AND ENFORCED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS, WITHOUT REGARD
TO THE PRINCIPLES OF CONFLICTS OF LAWS THEREOF.

      15.8   Remedies Not Exclusive.  The rights and remedies herein provided
             ----------------------
shall be cumulative and not exclusive of any rights or remedies provided by law.
The rights and remedies of any party based upon, arising out of, or otherwise in
respect of any inaccuracy in or breach of any representation, warranty,
covenant, or agreement contained in this Agreement shall in no way be limited by
the fact that the act, omission, occurrence, or other state of facts upon which
any claim of any such inaccuracy or breach is based may also be the subject
matter of any other representation, warranty, covenant, or agreement contained
in this Agreement (or in any other agreement between the parties) as to which
there is no inaccuracy or breach.

      15.9   Further Assurances.  From time to time following the Closing, at
             ------------------
the request of any party hereto and without further consideration, the other
party or parties hereto shall execute and deliver to such requesting party such
instruments and documents and take such other action (but without incurring any
material financial obligation) as such requesting party may reasonably request
in order to consummate more fully and effectively the transactions contemplated
hereby.

      15.10  Counterparts.  This Agreement may be executed by the parties
             ------------
hereto in any number of counterparts, each of which shall be deemed an original,
but all of which shall constitute one and the same agreement.  Each counterpart
may consist of a number of copies hereof each signed by less than all, but
together signed by all, the parties hereto.

      15.11  Injunctive Relief.  The parties hereto acknowledge and agree that
             -----------------
irreparable damage would occur in the event any of the provisions of this
Agreement were not performed in accordance with their specific terms or were
otherwise breached.  It is accordingly agreed that the parties shall be entitled
to an injunction or injunctions to prevent breaches of the provisions of this
Agreement, and shall be entitled to enforce specifically the provisions of this
Agreement, in any court of the United States or any state thereof having
jurisdiction, in addition to any other remedy to which the parties may be
entitled under this Agreement or at law or in equity.

      15.12  Consent to Jurisdiction.  The parties hereto hereby irrevocably
             -----------------------
submit to the jurisdiction of the courts of the State of Texas and the federal
courts of the United States of America located in Harris County, Texas, and
appropriate appellate courts therefrom, over any dispute arising out of or
relating to this Agreement or any of the transactions contemplated hereby, and
each party hereby irrevocably agrees that all claims in respect of such dispute
or proceeding shall be heard and determined in such courts.  The parties hereby
irrevocably waive, to the fullest extent permitted by Applicable Law, any
objection which they may now or hereafter have to the laying of venue of any
dispute arising out of or relating to this Agreement or any of the transactions
contemplated hereby brought in such court or any defense of inconvenient forum
for the maintenance of such dispute.

                                      -40-
<PAGE>

Each of the parties hereto agrees that a judgment in any such dispute may be
enforced in other jurisdictions by suit on the judgment or in any other manner
provided by law. This consent to jurisdiction is being given solely for purposes
of this Agreement and is not intended to, and shall not, confer consent to
jurisdiction with respect to any other dispute in which a party to this
Agreement may become involved.

      15.13. Payments.  All payments to be made hereunder shall be in lawful
             --------
money of the United States of America.

      15.14. Master Subordination Agreement.  The terms of this Agreement are
             ------------------------------
subject to the terms of that certain Master Subordination Agreement, dated as of
May 1, 2000, made by and between the "Junior Creditor" therein (including
Buyers) and AROC Inc., a Delaware corporation, Alliance Resources Group, Inc., a
Delaware corporation, LaTex Petroleum Corporation, an Oklahoma corporation, AROC
(Texas), Inc., a Texas corporation, Germany Oil Company, a Delaware corporation,
Alliance Resources (USA), Inc., a Delaware corporation, Source Petroleum, Inc.,
a Louisiana corporation, Alliance Resources PLC, a public limited company
incorporated under the laws of England and Wales (collectively, the "Aroc
Parties"), in favor of Toronto Dominion (Texas), Inc., as Agent, for the lenders
("Lenders") parties to the credit agreement among the Aroc Parties, the Agent
and the Lenders.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

                                      -41-
<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Agreement, or caused
this Agreement to be executed by their duly authorized representatives, all as
of the day and year first above written.

                             AROC INC.

                              By:  _________________________________________
                                   Name:  Francis M. Munchinski
                                   Title: Vice President

                              ENCAP EQUITY 1996 LIMITED PARTNERSHIP

                              By:  ENCAP INVESTMENTS L.L.C.

                              By:  _________________________________________
                                   Name:  __________________________________
                                   Title: Managing Director

                              ENERGY CAPITAL INVESTMENT COMPANY PLC

                              By:  _________________________________________
                                   Name:  Gary R. Petersen
                                   Title: Director

                              EL PASO CAPITAL INVESTMENTS, L.L.C.

                              By:  _________________________________________
                                   Name:  __________________________________
                                   Title: __________________________________

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