<PAGE>

                                                                     EXHIBIT 2.1


                                                                         ANNEX A
                          AGREEMENT AND PLAN OF MERGER

                                  BY AND AMONG

                         ANADARKO PETROLEUM CORPORATION
                                  ("ANADARKO")

                              BELAIR MERGER CORP.
                  a wholly owned direct subsidiary of Anadarko
                                  ("SUBCORP")

                                      AND

                               HOWELL CORPORATION
                                   ("HOWELL")

                               SEPTEMBER 29, 2002
<PAGE>

                               TABLE OF CONTENTS

<Table>
<Caption>
                                                                      PAGE
                                                                      ----
<S>     <C>                                                           <C>
PRELIMINARY STATEMENTS..............................................   A-1
ARTICLE I.  THE MERGER..............................................   A-1
  1.1   The Merger..................................................   A-1
  1.2   Effective Time..............................................   A-1
  1.3   Effects of the Merger.......................................   A-2
  1.4   Certificate of Incorporation and By-laws....................   A-2
  1.5   Directors and Officers of the Surviving Corporation.........   A-2
  1.6   Additional Actions..........................................   A-2
ARTICLE II.  CONVERSION OF SECURITIES...............................   A-2
  2.1   Effect on Capital Stock.....................................   A-2
  2.2   Surrender and Payment.......................................   A-3
        (a)  Paying Agent...........................................   A-3
        (b)  Exchange Procedure.....................................   A-4
        (c)  Stock Transfer Books...................................   A-4
        (d)  No Liability...........................................   A-4
        (e)  Lost Certificates......................................   A-5
        (f)  No Further Ownership Rights in Howell Common Stock.....   A-5
        (g)  Withholding Rights.....................................   A-5
  2.3   Treatment of Stock Options; Restricted Stock................   A-5
ARTICLE III.  REPRESENTATIONS AND WARRANTIES OF ANADARKO AND
  SUBCORP...........................................................   A-6
  3.1   Organization and Standing...................................   A-6
  3.2   Corporate Power and Authority...............................   A-6
  3.3   Conflicts; Consents and Approvals...........................   A-6
  3.4   Brokerage and Finders' Fees.................................   A-6
  3.5   Proxy Statement.............................................   A-7
  3.6   Funds.......................................................   A-7
ARTICLE IV.  REPRESENTATIONS AND WARRANTIES OF HOWELL...............   A-7
  4.1   Organization and Standing...................................   A-7
  4.2   Subsidiaries................................................   A-7
  4.3   Corporate Power and Authority...............................   A-8
  4.4   Capitalization of Howell....................................   A-8
  4.5   Conflicts; Consents and Approvals...........................   A-9
  4.6   Brokerage and Finders' Fees; Expenses.......................  A-10
  4.7   Howell SEC Documents........................................  A-10
  4.8.  Proxy Statement.............................................  A-10
  4.9   Compliance with Law.........................................  A-10
  4.10  Litigation..................................................  A-11
  4.11  No Material Adverse Change..................................  A-11
  4.12  Taxes.......................................................  A-11
  4.13  Intellectual Property.......................................  A-12
  4.14  Title to and Condition of Properties........................  A-12
  4.15  Employee Benefit Plans......................................  A-13
</Table>

                                       A-i
<PAGE>

<Table>
<Caption>
                                                                      PAGE
                                                                      ----
<S>     <C>                                                           <C>
  4.16  Contracts...................................................  A-15
  4.17  Labor Matters...............................................  A-17
  4.18  Undisclosed Liabilities.....................................  A-17
  4.19  Operation of Howell's Business; Relationships...............  A-17
  4.20  Permits; Compliance.........................................  A-17
  4.21  Environmental Matters.......................................  A-17
  4.22  Accounts Receivable.........................................  A-18
  4.23  Insurance...................................................  A-18
  4.24  Opinion of Financial Advisor................................  A-18
  4.25  Board Recommendation; Required Vote.........................  A-18
  4.26  Section 203 of the DGCL.....................................  A-19
ARTICLE V.  COVENANTS OF THE PARTIES................................  A-19
  5.1   Mutual Covenants............................................  A-19
        (a)  HSR Act Filings; Reasonable Efforts; Notification......  A-19
        (b)  Public Announcements...................................  A-20
        (c)  Obligations of Anadarko and Howell.....................  A-21
        (d)  Conveyance Taxes.......................................  A-21
  5.2   Covenants of Anadarko.......................................  A-21
        (a)  Information for the Preparation of the Proxy             A-21
        Statement...................................................
        (b)  Indemnification; Directors' and Officers' Insurance....  A-21
        (c)  Employee Benefit Matters...............................  A-21
  5.3   Covenants of Howell.........................................  A-22
        (a)  Howell Stockholders Meeting............................  A-22
        (b)  Preparation of the Proxy Statement.....................  A-23
        (c)  Conduct of Howell's Operations.........................  A-23
        (d)  No Solicitation........................................  A-25
        (e)  Howell Convertible Preferred Stock.....................  A-26
        (f)  Access.................................................  A-26
        (g)  Advice of Changes; Subsequent Financial Statements.....  A-27
ARTICLE VI.  CONDITIONS TO THE MERGER...............................  A-27
  6.1   Conditions to the Obligations of Each Party.................  A-27
  6.2   Conditions to the Obligations of Anadarko and Subcorp.......  A-27
  6.3   Conditions to the Obligations Howell........................  A-28
ARTICLE VII.  TERMINATION AND AMENDMENT.............................  A-28
  7.1   Termination.................................................  A-28
  7.2   Effect of Termination.......................................  A-29
  7.3   Amendment...................................................  A-29
  7.4   Extension; Waiver...........................................  A-30
ARTICLE VIII.  MISCELLANEOUS........................................  A-30
  8.1   Survival of Representations and Warranties..................  A-30
  8.2   Notices.....................................................  A-30
  8.3   Interpretation..............................................  A-30
  8.4   Counterparts................................................  A-31
  8.5   Entire Agreement............................................  A-31
</Table>

                                       A-ii
<PAGE>

<Table>
<Caption>
                                                                      PAGE
                                                                      ----
<S>     <C>                                                           <C>
  8.6   Third-Party Beneficiaries...................................  A-31
  8.7   Governing Law...............................................  A-31
  8.8   Consent to Jurisdiction; Venue..............................  A-31
  8.9   Specific Performance........................................  A-32
  8.10  Assignment..................................................  A-32
  8.11  Expenses....................................................  A-32
</Table>

                                      A-iii
<PAGE>

                             INDEX OF DEFINED TERMS

<Table>
<Caption>
DEFINED TERM                                                  SECTION
- ------------                                                  -------
<S>                                                           <C>
Action......................................................  4.10
Affected Employees..........................................  5.2(c)(i)
Agreement...................................................  Preamble
AMI.........................................................  4.16(r)
Anadarko....................................................  Preamble
Anadarko Disclosure Schedule................................  3.3(d)(iii)
Antitrust Laws..............................................  5.1(a)(ii)
Applicable Laws.............................................  2.2(d)
Appraisal Shares............................................  2.1(f)
Certificate.................................................  2.1(b)
Certificate of Merger.......................................  1.2
Closing.....................................................  1.2
Closing Date................................................  1.2
Code........................................................  2.2(g)
Commission..................................................  4.7
Competing Transaction.......................................  5.3(d)
Confidentiality Agreement...................................  5.3(d)
Contract....................................................  4.16
Controlled Group Liability..................................  4.15(a)
Costs.......................................................  7.2
Delaware Secretary of State.................................  1.2
DGCL........................................................  1.1
Effective Time..............................................  1.2
Environmental Law...........................................  4.21
Environmental Permit........................................  4.21
ERISA.......................................................  4.15(a)
ERISA Affiliate.............................................  4.15(a)
Exchange Act................................................  4.7
Exchange Fund...............................................  2.2(a)
DGCL........................................................  1.1
GAAP........................................................  4.7
Governmental Authority......................................  3.3(d)
Hazardous Materials.........................................  4.21
Howell......................................................  Preamble
Howell Board Recommendation.................................  4.25
Howell By-laws..............................................  4.1
Howell Certificate..........................................  4.1
Howell Certificate of Designations..........................  4.4
Howell Common Stock.........................................  4.4
Howell Convertible Preferred Stock..........................  4.4
Howell Disclosure Schedule..................................  4.1
Howell Option...............................................  2.3(a)
Howell Optionholder.........................................  2.3(a)
</Table>

                                       A-iv
<PAGE>

<Table>
<Caption>
DEFINED TERM                                                  SECTION
- ------------                                                  -------
<S>                                                           <C>
Howell Permits..............................................  4.20
Howell Restricted Stock.....................................  4.4
Howell SEC Documents........................................  4.7
Howell Stock Plans..........................................  4.4
Howell Stockholders.........................................  2.2(a)
Howell Stockholders Meeting.................................  5.3(a)
HSR Act.....................................................  3.3(d)(i)
Indemnified Liabilities.....................................  5.2(b)(i)
Indemnified Party...........................................  5.2(b)(i)
Indemnified Parties.........................................  5.2(b)(i)
Intellectual Property Rights................................  4.13
Knowledge...................................................  8.3
Material Adverse Effect.....................................  8.3
Merger......................................................  Preliminary Statement A
Merger Consideration........................................  Preliminary Statement A
Multiemployer Plan..........................................  4.15(f)
Multiple Employer Plan......................................  4.15(f)
NYSE........................................................  4.7
Paying Agent................................................  2.2(a)
Plans.......................................................  4.15(a)
Preferred Certificate.......................................  2.1(b)
Preferred Merger Consideration..............................  Preliminary Statement A
Properties..................................................  4.14
Proxy Statement.............................................  5.3(b)
Qualified Plan..............................................  4.15(c)
Release.....................................................  4.21
Section 262.................................................  2.1(f)
Securities Act..............................................  4.7
Subcorp.....................................................  Preamble
Subcorp Common Stock........................................  2.1(a)
subsidiary..................................................  8.3
Superior Proposal...........................................  5.3(d)
Support Agreements..........................................  4.26
Surviving Corporation.......................................  1.1
Tax Returns.................................................  4.12(e)
Taxes.......................................................  4.12(f)
Withdrawal Liability........................................  4.15(a)
</Table>

                                       A-v
<PAGE>

                          AGREEMENT AND PLAN OF MERGER

     This Agreement and Plan of Merger (this "Agreement") is made and entered
into as of the 29th day of September 2002, by and among Anadarko Petroleum
Corporation, a Delaware corporation ("Anadarko"), Belair Merger Corp., a
Delaware corporation and a wholly owned subsidiary of Anadarko ("Subcorp"), and
Howell Corporation, a Delaware corporation ("Howell").

                             PRELIMINARY STATEMENTS

     A.  Anadarko desires to combine its businesses with the businesses operated
by Howell through the merger of Subcorp with and into Howell, with Howell as the
surviving corporation (the "Merger"), pursuant to which (i) each share of Howell
Common Stock (as defined in Section 4.4) issued and outstanding at the Effective
Time (as defined in Section 1.2), other than the shares of Howell Common Stock
owned by Anadarko, Subcorp or Howell (or any of their respective direct or
indirect wholly owned subsidiaries (as defined in Section 8.3) other than as
described in Section 2.1(e)) and other than the Appraisal Shares (as defined in
Section 2.1(f)) will be converted into the right to receive in cash, without
interest, $20.75 per share of Howell Common Stock (the "Merger Consideration")
and (ii) each share of Howell Convertible Preferred Stock (as defined in Section
4.4) issued and outstanding at the Effective Time other than the shares of
Howell Convertible Preferred Stock owned by Anadarko, Subcorp or Howell (or any
of their respective direct or indirect wholly owned subsidiaries) and other than
the Appraisal Shares will be converted into the right to receive in cash,
without interest, $76.15 per share of Howell Convertible Preferred Stock (the
"Preferred Merger Consideration"), all as more fully provided in this Agreement.

     B.  The respective Boards of Directors of Anadarko, Subcorp and Howell have
determined the Merger in the manner contemplated in this Agreement to be
advisable and in the best interests of their respective stockholders, and, by
resolutions duly adopted, have approved and adopted this Agreement.

     C.  Concurrently with the execution of this Agreement, and as a condition
and inducement to Anadarko's willingness to enter into this Agreement, certain
holders of Howell Common Stock and Howell Convertible Preferred Stock are
entering into Support Agreements (as defined in Section 4.26) with Anadarko.

                                   AGREEMENT

     Now, therefore, in consideration of these premises and the mutual and
dependent promises hereinafter set forth, the parties to this Agreement agree as
follows:

                                   ARTICLE I

                                   THE MERGER

     1.1.  The Merger.  Upon the terms and subject to the conditions of this
Agreement, and in accordance with the provisions of the Delaware General
Corporation Law (the "DGCL"), Subcorp shall be merged with and into Howell at
the Effective Time. As a result of the Merger, the separate corporate existence
of Subcorp shall cease and Howell shall continue its existence under the laws of
the State of Delaware. Howell, in its capacity as the corporation surviving the
Merger, is sometimes referred to as the "Surviving Corporation".

     1.2.  Effective Time.  As promptly as possible on the Closing Date (as
defined below), the parties to this Agreement shall cause the Merger to be
consummated by filing with the Secretary of State of the State of Delaware (the
"Delaware Secretary of State") a certificate of merger (the "Certificate of
Merger") in such form as is required by and executed in accordance with Section
251 of the DGCL. The Merger shall become effective when the Certificate of
Merger has been filed with the Delaware Secretary of State or at such later time
as shall be agreed upon by Anadarko and Howell and specified in the Certificate
of Merger (the "Effective Time"). Prior to the filing referred to in this
Section 1.2, a closing (the "Closing") shall be held at the offices of Anadarko,
or such other place as the parties to this Agreement may agree, as soon as
practicable

                                       A-1
<PAGE>

following the date upon which all conditions set forth in Article VI that are
capable of being satisfied prior to the Closing have been satisfied or waived,
or at such other date as Anadarko and Howell may agree; provided that the
conditions set forth in Article VI that are capable of being satisfied prior to
the Closing have been satisfied or waived at or prior to such date, and
provided, further, that the Closing shall be delayed if and only for so long as
necessary if a banking moratorium, act of terrorism or war (whether or not
declared) affecting United States banking or financial markets generally
prevents the Closing (such date, the "Closing Date").

     1.3.  Effects of the Merger.  From and after the Effective Time, the Merger
shall have the effects set forth in Section 259 of the DGCL.

     1.4.  Certificate of Incorporation and By-laws.  The Certificate of Merger
shall provide that, at the Effective Time, (a) the Surviving Corporation's
Certificate of Incorporation as in effect immediately prior to the Effective
Time shall continue as the Certificate of Incorporation of the Surviving
Corporation, and (b) Subcorp's By-laws in effect immediately prior to the
Effective Time shall be Surviving Corporation's By-laws; in each case, until
amended in accordance with the DGCL.

     1.5.  Directors and Officers of the Surviving Corporation.  From and after
the Effective Time, the officers of Subcorp immediately prior to the Effective
Time shall be the officers of the Surviving Corporation, and the directors of
Subcorp immediately prior to the Effective Time shall be the directors of the
Surviving Corporation, in each case, until their respective successors are duly
elected and qualified. On or prior to the Closing Date, Howell shall deliver to
Anadarko evidence satisfactory to Anadarko of the resignations of the directors
of Howell, such resignations to be effective as of the Effective Time.

     1.6.  Additional Actions.  If, at any time after the Effective Time, the
Surviving Corporation shall consider or be advised that any further deeds,
assignments or assurances in law or any other acts are necessary or desirable to
(a) vest, perfect or confirm, of record or otherwise, in the Surviving
Corporation its right, title or interest in, to or under any of the rights,
properties or assets of Howell or (b) otherwise carry out the provisions of this
Agreement, Howell and the officers and directors of Howell shall be deemed to
have granted to the Surviving Corporation an irrevocable power of attorney, and
the Surviving Corporation and the officers and directors of the Surviving
Corporation will be authorized in the name of and on behalf of Howell, to
execute and deliver all such deeds, assignments or assurances in law and to take
all acts necessary, proper or desirable to vest, perfect or confirm title to and
possession of such rights, properties or assets in the Surviving Corporation and
otherwise to carry out the provisions of this Agreement, and the officers and
directors of the Surviving Corporation are authorized in the name of Howell or
otherwise to take any and all such action.

                                   ARTICLE II

                            CONVERSION OF SECURITIES

     2.1.  Effect on Capital Stock.  At the Effective Time, by virtue of the
Merger and without any action on the part of Anadarko, Subcorp or Howell or
their respective stockholders, as applicable:

          (a) Each share of common stock, $0.01 par value, of Subcorp ("Subcorp
     Common Stock") issued and outstanding immediately prior to the Effective
     Time shall be converted into one fully paid and nonassessable share of
     common stock of the Surviving Corporation. Except as provided in Section
     2.1(e), such newly issued shares shall thereafter constitute all of the
     issued and outstanding Surviving Corporation capital stock.

          (b) Subject to the other provisions of this Article II, each share of
     Howell Common Stock issued and outstanding immediately prior to the
     Effective Time, excluding any shares of Howell Common Stock owned by
     Anadarko, Subcorp or Howell or any of their respective subsidiaries, shall
     be converted into and represent the right to receive in cash, without
     interest, an amount equal to the Merger Consideration. At the Effective
     Time, all shares of Howell Common Stock (other than shares owned by a
     subsidiary of Howell, which shares shall be converted into shares of the
     Surviving Corporation pursuant to Section 2.1(e) of this Agreement) no
     longer shall be outstanding and automatically shall be cancelled and shall
     cease to exist, and each holder of a certificate that immediately prior to
     the Effective Time

                                       A-2
<PAGE>

     represented any shares of Howell Common Stock (a "Certificate") shall cease
     to have any rights with respect thereto, except the right to receive the
     Merger Consideration.

          (c) Subject to the other provisions of this Article II, each share of
     Howell Convertible Preferred Stock issued and outstanding immediately prior
     to the Effective Time shall be converted into and represent the right to
     receive in cash, without interest, an amount equal to the Preferred Merger
     Consideration. At the Effective Time, all shares of Howell Convertible
     Preferred Stock no longer shall be outstanding and automatically shall be
     cancelled and shall cease to exist, and each holder of a certificate that
     immediately prior to the Effective Time represented any shares of Howell
     Convertible Preferred Stock (a "Preferred Certificate") shall cease to have
     any rights with respect thereto, except the right to receive the Preferred
     Merger Consideration.

          (d) Each share of Howell capital stock held in the treasury of Howell
     automatically shall be cancelled and retired, and no payment shall be made
     in respect thereof.

          (e) Each share of Howell Common Stock owned by a subsidiary of Howell
     shall be converted into a number of shares of fully paid and nonassessable
     shares of common stock of the Surviving Corporation equal to the product of
     (i) the number of shares of Subcorp Common Stock issued and outstanding
     immediately prior to the Effective Time and (ii) a fraction, the numerator
     of which is one and the denominator of which is equal to the excess of (A)
     the sum of (I) the total number of shares of Howell Common Stock issued and
     outstanding immediately prior to the Effective Time and (II) the total
     number of shares of Howell Common Stock into which all shares of Howell
     Convertible Preferred Stock are convertible pursuant to their terms
     immediately prior to the Effective Time over (B) the total number of shares
     of Howell Common Stock owned by subsidiaries of Howell in the aggregate
     immediately prior to the Effective Time.

          (f) Notwithstanding anything in this Agreement to the contrary, the
     shares of Howell Common Stock or Howell Convertible Preferred Stock issued
     and outstanding immediately prior to the Effective Time that are held by
     any Howell Stockholder that is entitled to demand and properly demands
     appraisal of shares of Howell Common Stock or Howell Convertible Preferred
     Stock, as the case may be, pursuant to, and that complies in all respects
     with, the provisions of Section 262 of the DGCL ("Section 262") (the
     "Appraisal Shares") shall not be converted into the right to receive the
     Merger Consideration or the Preferred Merger Consideration, as the case may
     be, as provided in Section 2.1(b) or (c), respectively, but, instead, such
     Howell Stockholder shall be entitled to such rights (but only such rights)
     as are granted by Section 262. At the Effective Time, all Appraisal Shares
     shall no longer be outstanding and automatically shall be cancelled and
     shall cease to exist, and, except as otherwise provided by Applicable Laws
     (as defined in Section 2.2(d)), each holder of Appraisal Shares shall cease
     to have any rights with respect to the Appraisal Shares other than such
     rights as are granted by Section 262. Notwithstanding the foregoing, if any
     such Howell Stockholder shall fail to validly perfect or shall otherwise
     waive, withdraw or lose the right to appraisal under Section 262 or if a
     court of competent jurisdiction shall determine that such Howell
     Stockholder is not entitled to the relief provided by Section 262, then the
     rights of such Howell Stockholder under Section 262 shall cease, and such
     Appraisal Shares shall be deemed to have been converted at the Effective
     Time into, and shall have become, the right to receive the Merger
     Consideration or the Preferred Merger Consideration, as the case may be, as
     provided in Section 2.1(b) or (c) respectively. Howell shall give prompt
     notice to Anadarko of any demands for appraisal of any shares of Howell
     Common Stock or Howell Convertible Preferred Stock, and Anadarko shall have
     the opportunity to participate in all negotiations and proceedings with
     respect to such demands. Prior to the Effective Time, Howell shall not,
     without the prior written consent of Anadarko, make any payment with
     respect to, or settle or offer to settle, any such demands, or agree to do
     any of the foregoing.

     2.2.  Surrender and Payment.

     (a) Paying Agent.  Prior to the Effective Time, for the benefit of the
holders of Howell Common Stock and Howell Convertible Preferred Stock (such
holders collectively, the "Howell Stockholders"), Anadarko shall designate, or
shall cause to be designated (pursuant to an agreement in form and substance
reasonably acceptable to Anadarko), Mellon Investor Services or another bank or
trust company to act as agent for the

                                       A-3
<PAGE>

payment of the Merger Consideration and the Preferred Merger Consideration in
respect of Certificates and Preferred Certificates, respectively, upon surrender
of Certificates and Preferred Certificates, respectively, in accordance with
this Article II from time to time after the Effective Time (the "Paying Agent").
Promptly after the Effective Time, Anadarko shall deposit, or cause Subcorp to
deposit, with the Paying Agent cash in amounts sufficient for the payment of the
Merger Consideration and the Preferred Merger Consideration, pursuant to Section
2.1(b) and (c), respectively, upon surrender of the Certificates and Preferred
Certificates, respectively (such cash, the "Exchange Fund"). The Paying Agent
shall invest any cash included in the Exchange Fund, as directed by Anadarko, on
a daily basis. Any interest and other income resulting from investments shall be
paid to Anadarko upon termination of the Exchange Fund pursuant to Section
2.2(d).

     (b) Exchange Procedure.  As soon as reasonably practicable after the
Effective Time, the Paying Agent shall mail to each holder of record of one or
more Certificates or Preferred Certificates (i) a form of letter of transmittal
(which shall specify that delivery shall be effected, and risk of loss and title
to the Certificates or the Preferred Certificates held by such Howell
Stockholder shall pass, only upon proper delivery of the Certificates or the
Preferred Certificates to the Paying Agent and shall be in such form and have
such other customary provisions as Anadarko may reasonably specify), and (ii)
instructions for use in effecting the surrender of the Certificates and the
Preferred Certificates in exchange for the Merger Consideration or the Preferred
Merger Consideration, as the case may be. Upon surrender of a Certificate or a
Preferred Certificate for cancellation to the Paying Agent or to such other
agent or agents as may be appointed by Anadarko, together with such letter of
transmittal, duly completed and validly executed, and such other documents as
may reasonably be required by the Paying Agent, the holder of such Certificate
or Preferred Certificates shall be entitled to receive in exchange therefor the
amount of cash into which the shares of Howell Common Stock or Howell
Convertible Preferred Stock, as the case may be, formerly represented by the
Certificate or the Preferred Certificate, respectively, shall have been
converted pursuant to Section 2.1(b) or (c), respectively, and the Certificate
or the Preferred Certificate so surrendered shall be cancelled. In the event of
a transfer of ownership of Howell Common Stock or Howell Convertible Preferred
Stock, as the case may be, that is not registered in the stock transfer books of
Howell, the proper amount of cash may be paid in exchange therefor to a person
other than the person in whose name the Certificate or the Preferred Certificate
so surrendered is registered if such Certificate or Preferred Certificate shall
be properly endorsed or otherwise be in proper form for transfer and the person
requesting such payment shall pay any transfer or other Taxes required by reason
of the payment to a person other than the registered holder of the Certificate
or the Preferred Certificate, as the case may be, or establish to the
satisfaction of Anadarko that the Tax has been paid or is not applicable. No
interest shall be paid or shall accrue on the cash payable upon surrender of any
Certificate or Preferred Certificate.

     (c) Stock Transfer Books.  At the close of business on the day on which the
Effective Time occurs, the stock transfer books of Howell shall be closed, and
there shall be no further registration of transfers on the stock transfer books
of the Surviving Corporation of the shares of Howell Common Stock or Howell
Convertible Preferred Stock that were outstanding immediately prior to the
Effective Time. If, after the Effective Time, Certificates or Preferred
Certificates are presented to the Surviving Corporation or the Paying Agent for
transfer or any other reason, they shall be cancelled and exchanged as provided
in this Article II.

     (d) No Liability.  None of Anadarko, Subcorp, Howell or the Paying Agent
shall be liable to any person in respect of any cash delivered to a public
official pursuant to any applicable abandoned property, escheat or similar law.
Any portion of the Exchange Fund held by the Paying Agent for payment to the
holders of unsurrendered Certificates and Preferred Certificates and unclaimed
four months after the Effective Time shall be returned to Anadarko, after which
time any holder of unsurrendered Certificates or Preferred Certificates shall
look as a general creditor only to Anadarko for payment of the funds which the
holder of unsurrendered Certificates or Preferred Certificates may be owed,
subject to Applicable Laws. If any Certificates or Preferred Certificates shall
not have been surrendered prior to seven years after the Effective Time, any
such cash, dividends or distributions in respect of such Certificates or
Preferred Certificates shall, to the extent permitted by all applicable laws,
statutes, orders, rules, regulations or policies promulgated by, or judgments,
decisions or orders entered by, any Governmental Authority (as defined in
Section 3.3(d)), in

                                       A-4
<PAGE>

each case, to the extent applicable (collectively, "Applicable Laws"), become
the property of Anadarko, free and clear of all claims or interest of any person
previously entitled thereto.

     (e) Lost Certificates.  If any Certificate or Preferred Certificate shall
have been lost, stolen or destroyed, upon the making of an affidavit of that
fact by the person claiming a Certificate or Preferred Certificate to be lost,
stolen or destroyed, and, if required by Anadarko or the Surviving Corporation,
the posting by such person of a bond in such reasonable amount as Anadarko or
the Surviving Corporation may reasonably direct as indemnity against any claim
that may be made against it with respect to such Certificate or Preferred
Certificate, the Paying Agent shall pay, in respect of the lost, stolen or
destroyed Certificate or Preferred Certificate, the Merger Consideration or the
Preferred Merger Consideration, respectively.

     (f) No Further Ownership Rights in Howell Common Stock.  The Merger
Consideration and the Preferred Merger Consideration paid in accordance with the
terms of this Article II in respect of Certificates or Preferred Certificates,
as the case may be, that have been surrendered in accordance with the terms of
this Agreement shall be deemed to have been paid in full satisfaction of all
rights pertaining to the shares of Howell Common Stock or Howell Convertible
Preferred Stock represented thereby.

     (g) Withholding Rights.  Each of the Surviving Corporation and Anadarko
shall be entitled to deduct and withhold, or cause the Paying Agent to deduct
and withhold, from the consideration otherwise payable pursuant to this
Agreement to any Howell Stockholders such amounts as it may be required to
deduct and withhold with respect to the making of such payment under the
Internal Revenue Code of 1986, as amended (together with the rules and
regulations thereunder, the "Code"), or any provision of state or local or
foreign Tax law. To the extent that amounts are so withheld by the Surviving
Corporation or Anadarko, as the case may be, the withheld amounts shall be
treated for all purposes of this Agreement as having been paid to the Howell
Stockholders in respect of which the deduction and withholding were made by the
Surviving Corporation or Anadarko, as the case may be.

     2.3.  Treatment of Stock Options; Restricted Stock.

     (a) At the Effective Time, each unexpired and unexercised outstanding
option to purchase shares of Howell Common Stock issued or granted as of the
date of this Agreement under the Howell Stock Plans (as defined in Section 4.4),
whether or not vested or exercisable in accordance with its terms, which is
listed in Section 4.4 to the Howell Disclosure Schedule (as defined in Section
4.1) (each, a "Howell Option") will by virtue of the Merger and without any
action on the part of any holder of a Howell Option (each, a "Howell
Optionholder") be cancelled as of the Effective Time solely in exchange for the
right to receive as soon as reasonably practicable following the Effective Time
an amount in cash (less any applicable withholding taxes) equal to the product
of (i) the number of shares of Howell Common Stock subject to such Howell Option
immediately prior to the Effective Time, and (ii) the amount by which (A) the
Merger Consideration exceeds (B) the exercise price per share of Howell Common
Stock subject to such Howell Option. Prior to the Effective Time, Howell shall
take any and all actions necessary to effectuate this Section 2.3(a).

     (b) At the Effective Time, by virtue of the Merger and without any action
on the part of any holder of shares of Howell Restricted Stock (as defined in
Section 4.4), each share of Howell Restricted Stock, whether or not vested or
forfeitable in accordance with its terms, which is listed in Section 4.4 to the
Howell Disclosure Schedule (including the name of the stockholder, number of
shares of Howell Restricted Stock and vesting schedule with respect thereto)
shall automatically be cancelled solely in exchange for the right to receive as
soon as reasonably practicable following the Effective Time an amount in cash
(less any applicable withholding taxes) equal to the Merger Consideration.

     (c) The Howell Stock Plans shall terminate as of the Effective Time, and
the provisions in any other Plan providing for the issuance, transfer or grant
of any capital stock of Howell or any interest in respect of any capital stock
of Howell (including any "phantom" stock or stock appreciation rights) shall be
deleted as of the Effective Time, and Howell shall ensure that following the
Effective Time no holder of a Howell Option or any participant in any Howell
Stock Plan or other Plan shall have any right thereunder to acquire any capital
stock (including any "phantom" stock or stock appreciation rights) of Howell or
the Surviving Corporation.

                                       A-5
<PAGE>

                                  ARTICLE III

             REPRESENTATIONS AND WARRANTIES OF ANADARKO AND SUBCORP

     In order to induce Howell to enter into this Agreement, Anadarko and
Subcorp represent and warrant to Howell that the statements contained in this
Article III are true, correct and complete.

     3.1.  Organization and Standing.  Each of Anadarko and Subcorp is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware with full corporate power and authority to own, lease,
use and operate its properties and to conduct its businesses as and where now
owned, leased, used, operated and conducted.

     3.2.  Corporate Power and Authority.  Each of Anadarko and Subcorp has all
requisite corporate power and authority to enter into and deliver this
Agreement, to perform its obligations under this Agreement, and to consummate
the transactions contemplated by this Agreement. The execution and delivery of
this Agreement and the consummation of the transactions contemplated by this
Agreement by Anadarko and Subcorp have been duly authorized by all necessary
corporate action on the part of each of Anadarko and Subcorp. This Agreement has
been duly executed and delivered by each of Anadarko and Subcorp and constitutes
the legal, valid and binding obligation of each of Subcorp and Anadarko
enforceable against each of Subcorp and Anadarko in accordance with its terms.

     3.3.  Conflicts; Consents and Approvals.  Neither the execution and
delivery of this Agreement by Anadarko or Subcorp nor the consummation of the
transactions contemplated by this Agreement will:

          (a) conflict with, or result in a breach of, any provision of
     Anadarko's Restated Certificate of Incorporation, as amended, or Anadarko's
     By-laws, as amended, or Subcorp's Certificate of Incorporation or Subcorp's
     By-laws;

          (b) violate, or conflict with, or result in a breach of any provision
     of, or constitute a default (or an event that, with the giving of notice,
     the passage of time or otherwise, would constitute a default) under, or
     entitle any individual or entity (with the giving of notice, the passage of
     time or otherwise) to terminate, accelerate, modify or call a default
     under, or result in the creation of any lien, security interest, charge or
     encumbrance upon any of the properties or assets of Anadarko or any of its
     subsidiaries under, any of the terms, conditions or provisions of any note,
     bond, mortgage, indenture, deed of trust, license, contract, undertaking,
     agreement, lease or other instrument or obligation to which Anadarko or any
     of its subsidiaries is a party;

          (c) violate any order, writ, injunction, decree, statute, rule or
     regulation applicable to Anadarko or any of its subsidiaries or their
     respective properties or assets; or

          (d) require any action or consent or approval of, or review by, or
     registration or filing by Anadarko or any of its affiliates with, any third
     party or any local, domestic, foreign or multinational court, arbitral
     tribunal, administrative agency or commission or other governmental or
     regulatory body, agency, instrumentality or authority (a "Governmental
     Authority"), other than (i) actions required by the Hart-Scott-Rodino
     Antitrust Improvements Act of 1976, as amended (together with the rules and
     regulations thereunder, the "HSR Act"), if applicable, (ii) registrations
     or other actions required under United States federal and state securities
     laws as are contemplated by this Agreement, or (iii) consents or approvals
     of any Governmental Authority set forth in Section 3.3 to the disclosure
     schedule delivered by Anadarko to Howell and dated the date of this
     Agreement (the "Anadarko Disclosure Schedule");

except in the case of Section 3.3(b) as is set forth in Section 3.3(b) to the
Anadarko Disclosure Schedule, and in the case of Sections 3.3(c) and 3.3(d) for
any of the foregoing that could not, individually or in the aggregate, have or
reasonably be expected to have a Material Adverse Effect (as defined in Section
8.3) on Anadarko or a material adverse effect on the ability of the parties to
this Agreement to consummate the transactions contemplated by this Agreement.

     3.4.  Brokerage and Finders' Fees.  Except as set forth in Section 3.4 to
the Anadarko Disclosure Schedule, neither Anadarko nor any stockholder,
director, officer or employee of Anadarko has incurred or

                                       A-6
<PAGE>

will incur on behalf of Anadarko any brokerage, finders', advisory or similar
fee in connection with the transactions contemplated by this Agreement.

     3.5.  Proxy Statement.  None of the information supplied or to be supplied
in writing by Anadarko or Subcorp for inclusion or incorporation by reference in
the Proxy Statement (as defined in Section 5.3(b)) will, at the date the Proxy
Statement is mailed to holders of Howell Common Stock or at the time of the
Howell Stockholders Meeting (as defined in Section 5.3(a)), contain any untrue
statement of a material fact or omit to state any material fact required to be
stated therein or necessary, in order to make the statements therein in light of
the circumstances under which they are made, not misleading.

     3.6.  Funds.  Anadarko will have sufficient funds for the payment of the
Merger Consideration and the Preferred Merger Consideration in accordance with
the terms of this Agreement.

                                   ARTICLE IV

                    REPRESENTATIONS AND WARRANTIES OF HOWELL

     In order to induce Subcorp and Anadarko to enter into this Agreement,
Howell hereby represents and warrants to Anadarko and Subcorp that the
statements contained in this Article IV are true, correct and complete.

     4.1.  Organization and Standing.  Howell is a corporation duly organized,
validly existing and in good standing under the laws of the State of Delaware
with full corporate power and authority to own, lease, use and operate its
properties and to conduct its businesses as and where now owned, leased, used,
operated and conducted. Each of Howell's subsidiaries is an organization duly
incorporated, validly existing, and in good standing under the laws of its
jurisdiction of incorporation with full corporate power and authority to own,
lease, use and operate its properties and to conduct its businesses as and where
now owned, leased, used, operated and conducted. Howell and each of its
subsidiaries are duly qualified to do business and are in good standing in each
jurisdiction in which the nature of the business conducted by it or the property
it owns, leases or operates requires it to so qualify, except where the failure
to be so qualified or in good standing in such jurisdiction would not have a
Material Adverse Effect on Howell. Howell is not in default in the performance,
observance or fulfillment of any provision of Howell's Restated Certificate of
Incorporation, as amended, including the Howell Certificate of Designations (as
defined in Section 4.4), as in effect on the date of this Agreement (the "Howell
Certificate") or Howell's By-laws, as amended, as in effect on the date of this
Agreement (the "Howell By-laws"), and none of Howell's subsidiaries is in
default in the performance, observance or fulfillment of any provision of its
certificate of incorporation or by-laws. Howell has heretofore made available to
Anadarko in written form complete and correct copies of the Howell Certificate
and the Howell By-laws and the certificates of incorporation and by-laws for
each of its subsidiaries. Section 4.1 to the disclosure schedule delivered by
Howell to Anadarko and dated the date of this Agreement (the "Howell Disclosure
Schedule") sets forth a true and accurate list of each jurisdiction in which
Howell or any of its subsidiaries is qualified to do business and discloses
whether Howell (or any of its subsidiaries) is in good standing in such
jurisdiction.

     4.2.  Subsidiaries.  Except as set forth in Section 4.2 to the Howell
Disclosure Schedule, Howell owns, directly or indirectly, each of the
outstanding shares of capital stock (or other securities having by their terms
ordinary voting power to elect a majority of directors or others performing
similar functions with respect to such subsidiary) of each of its subsidiaries,
all of which are in corporate form. Howell does not own, directly or indirectly,
any equity or other ownership interest in any corporation, partnership, joint
venture or other entity or enterprise, except for the subsidiaries set forth in
Section 4.2 to the Howell Disclosure Schedule, and other interests which (i) are
immaterial in amount, (ii) are immaterial to the businesses or operations of
Howell or any of its subsidiaries, (iii) are immaterial to the ownership of
assets of Howell or any of its subsidiaries, and (iv) do not give rise to
liabilities or obligations of, or restrictions on, Howell or any of its
subsidiaries, except for those liabilities or obligations or restrictions which
are immaterial. Except as set forth in Section 4.2 to the Howell Disclosure
Schedule and except for nominal amounts due to electrical cooperatives, Howell
is not subject to any obligation or requirement to provide funds to or make any
investment (in the form of a loan,

                                       A-7
<PAGE>

capital contribution or otherwise) in any such entity or any other person. Each
of the outstanding shares of capital stock of each of Howell's subsidiaries is
duly authorized, validly issued, fully paid and nonassessable, and is owned,
directly or indirectly, by Howell free and clear of all liens, pledges, security
interests, claims or other encumbrances. The following information for each of
Howell's subsidiaries is set forth in Section 4.2 to the Howell Disclosure
Schedule, as applicable: (a) its name and jurisdiction of incorporation or
organization; (b) its authorized capital stock or share capital; and (c) the
number of issued and outstanding shares of capital stock or share capital and
the record owner(s) thereof. Other than as set forth in Section 4.2 to the
Howell Disclosure Schedule, there are no outstanding subscriptions, options,
warrants, puts, calls, phantom stock rights, stock appreciation rights,
stock-based performance units, agreements, understandings, claims or other
commitments or rights of any type relating to the issuance, sale or transfer of
any securities of any of Howell's subsidiaries or that give any person or entity
the right to receive any economic benefit or right similar to or derived from
the economic benefits or rights of the capital stock of one or more subsidiaries
of Howell, nor are there outstanding any securities that are convertible into or
exchangeable for any shares of capital stock of any of Howell's subsidiaries,
and neither Howell nor any of its subsidiaries has any obligation of any kind to
issue any additional securities or to pay for or repurchase any securities of
any of Howell's subsidiaries or any predecessor thereof.

     4.3.  Corporate Power and Authority.  Howell has all requisite corporate
power and authority to enter into and deliver this Agreement, to perform its
obligations under this Agreement, and, subject to adoption of this Agreement and
the transactions contemplated by this Agreement by the holders of Howell Common
Stock, to consummate the transactions contemplated by this Agreement. The
execution and delivery of this Agreement by Howell have been duly authorized by
all necessary corporate action on the part of Howell, subject to adoption of
this Agreement and the transactions contemplated by this Agreement by the
holders of Howell Common Stock. This Agreement has been duly executed and
delivered by Howell, and constitutes the legal, valid and binding obligation of
Howell enforceable against Howell in accordance with its terms.

     4.4.  Capitalization of Howell.  (a) As of the date of this Agreement,
Howell's authorized capital stock consisted solely of (a) 50,000,000 shares of
common stock, par value $1.00 per share ("Howell Common Stock"), of which (i)
6,499,210 shares were issued and outstanding (excluding the shares set forth in
clauses (ii) , (iii) and (iv) of this Section 4.4(a)), (ii) 11,900 shares were
issued and held by a subsidiary of Howell, (which does not include the shares
reserved for issuance set forth in clause (iii) below), (iii) 943,968 shares
were reserved for issuance upon the exercise of outstanding Howell Options
pursuant to Howell's 1988 Stock Option Plan, Omnibus Stock Awards and Incentive
Plan, Nonqualified Stock Option Plan for Non-Employee Directors, 1997
Nonqualified Stock Option Plan and any other plan pursuant to which any
outstanding options to purchase Howell Common Stock were or may be granted (the
"Howell Stock Plans"), (iv) 224,510 shares of Howell Common Stock were subject
to outstanding restricted stock awards issued under either the Howell Stock
Plans or issued pursuant to Howell's other restricted stock agreements (the
"Howell Restricted Stock"), and (v) 2,532,300 shares were reserved for issuance
upon conversion of the outstanding shares of Howell Convertible Preferred Stock,
and (b) 3,000,000 shares of preferred stock, par value $1.00 per share, of which
690,000 shares designated as $3.50 Convertible Preferred Stock, Series A (the
"Howell Convertible Preferred Stock") pursuant to the Certificate of
Designations dated April 19, 1993 (the "Howell Certificate of Designations"),
were issued and outstanding. Except as specified in the preceding sentence, no
shares of capital stock of Howell were authorized or were issued and outstanding
or reserved for future issuance under any agreement, arrangement or
understanding. The "Conversion Price" for each share of Howell Convertible
Preferred Stock, within the meaning of Section 3(b) of the Howell Certificate of
Designations, as determined and adjusted in accordance with the Howell
Certificate of Designations, is $13.64.

     (b) Each outstanding share of Howell capital stock is duly authorized and
validly issued, fully paid and nonassessable, and has not been issued in
violation of any preemptive or similar rights. Other than as set forth in the
first sentence of this Section 4.4, or in Section 4.4 to the Howell Disclosure
Schedule, there are no outstanding subscriptions, options, warrants, puts,
calls, phantom stock rights, stock appreciation rights, stock-based performance
units, agreements, understandings, claims or other commitments or rights of any
type granted or entered into by Howell or any of its subsidiaries relating to
the issuance, sale, repurchase or transfer

                                       A-8
<PAGE>

of any securities of Howell or that give any person or entity the right to
receive any economic benefit or right similar to or derived from the economic
benefits and rights of capital stock of Howell, nor are there outstanding any
securities that are convertible into or exchangeable for any shares of Howell
capital stock, and neither Howell nor any of its subsidiaries has any obligation
of any kind to issue any additional securities or to pay for or repurchase any
securities of Howell or any predecessor. Except as set forth in Section 4.4 to
the Howell Disclosure Schedule, no subsidiary of Howell owns any shares of
Howell Common Stock or Howell Convertible Preferred Stock, and no shares of
Howell Common Stock or Howell Convertible Preferred Stock are held in treasury.
Section 4.4 to the Howell Disclosure Schedule accurately sets forth (i) any
repurchases of shares of Howell capital stock since January 1, 2002, including
the date, price, quantity and, if known, identity of the selling stockholder,
and (ii) the aggregate repurchases of shares of Howell capital stock in 2001,
including the total quantity of shares repurchased and the aggregate price
thereof. The issuance, sale and repurchase by Howell of all of the shares of
capital stock described in this Section 4.4 have been in compliance with United
States federal and state securities laws and Delaware law.

     (c) Section 4.4 to the Howell Disclosure Schedule accurately sets forth the
names of all Howell Optionholders, and the number of shares of Howell capital
stock issuable upon exercise of all Howell Options (including for each Howell
Optionholder the exercise price and vesting schedule with respect to each Howell
Option and whether the Howell Option is intended to qualify as an "incentive
stock option" (within the meaning of Section 422 of the Code)). Section 4.4 to
the Howell Disclosure Schedule accurately sets forth the names of, and number of
shares of Howell Restricted Stock held by, all holders of shares of Howell
Restricted Stock (including the vesting schedule with respect thereto). Except
as set forth in Section 4.4 to the Howell Disclosure Schedule, neither Howell
nor any of its subsidiaries has agreed to register any securities under the
Securities Act (as defined in Section 4.7) or under any state securities law or
granted registration rights to any individual or entity; complete and correct
copies of any such registration rights or similar agreements previously have
been provided to Anadarko.

     4.5.  Conflicts; Consents and Approvals.  Neither the execution and
delivery of this Agreement by Howell, nor the consummation of the transactions
contemplated by this Agreement will:

          (a) conflict with, or result in a breach of any provision of, the
     Howell Certificate or the Howell By-laws or the certificate of
     incorporation or by-laws of any of Howell's subsidiaries;

          (b) violate, or conflict with, or result in a breach of any provision
     of, or constitute a default (or an event that, with the giving of notice,
     the passage of time or otherwise, would constitute a default) under, or
     entitle any person (with the giving of notice, the passage of time or
     otherwise) to terminate, accelerate, modify or call a default under, or
     result in the creation of any lien, security interest, charge or
     encumbrance upon any of the properties or assets of Howell or any of its
     subsidiaries under, any of the terms, conditions or provisions of any note,
     bond, mortgage, indenture, deed of trust, license, contract, undertaking,
     agreement, lease or other instrument or obligation to which Howell or any
     of its subsidiaries is a party;

          (c) violate any order, writ, injunction, decree, statute, rule or
     regulation applicable to Howell or any of its subsidiaries or any of their
     respective properties or assets; or

          (d) require any action or consent or approval of, or review by, or
     registration or filing by Howell or any of its subsidiaries with, any third
     party or any Governmental Authority, other than (i) adoption of this
     Agreement and the transactions contemplated by this Agreement by the
     holders of Howell Common Stock, (ii) actions required by the HSR Act, if
     applicable, (iii) registrations or other actions required under United
     States federal and state securities laws as are contemplated by this
     Agreement, and (iv) consents or approvals of any Governmental Authority set
     forth in Section 4.5 to the Howell Disclosure Schedule;

except in the case of Section 4.5(b) as is set forth in Section 4.5(b) to the
Howell Disclosure Schedule, and, in the case of Sections 4.5(c) and 4.5(d) for
any of the foregoing that could not, individually or in the aggregate, have or
reasonably be expected to have a Material Adverse Effect on Howell or a material
adverse

                                       A-9
<PAGE>

effect on the ability of the parties to this Agreement to consummate the
transactions contemplated by this Agreement.

     4.6.  Brokerage and Finders' Fees; Expenses.  Except as set forth in
Section 4.6 to the Howell Disclosure Schedule, neither Howell nor any
stockholder, director, officer, employee or affiliate of Howell, has incurred or
will incur on behalf of Howell or its subsidiaries, any brokerage, finders',
advisory or similar fee in connection with the transactions contemplated by this
Agreement. Section 4.6 to the Howell Disclosure Schedule discloses the maximum
aggregate amount of all fees and expenses that will be paid or will be payable
by Howell and its subsidiaries to all attorneys, accountants, financial advisors
or other consultants in connection with the Merger and the transactions
contemplated by this Agreement and includes copies of all agreements relating to
such fees and expenses entered into by or on behalf of Howell or any of its
subsidiaries.

     4.7.  Howell SEC Documents.  Howell and its subsidiaries have timely filed
with the Securities and Exchange Commission (the "Commission") all forms,
reports, schedules, statements and other documents (as supplemented and amended
since the time of filing, collectively, the "Howell SEC Documents") required to
be filed by it since January 1, 1999 under the Securities Exchange Act of 1934,
as amended (together with the rules and regulations thereunder, the "Exchange
Act") or under the Securities Act of 1933, as amended (together with the rules
and regulations thereunder, the "Securities Act"). The Howell SEC Documents,
including any financial statements or schedules included in the Howell SEC
Documents, at the time filed (and, in the case of registration statements and
proxy statements, on the dates of effectiveness and the dates of mailing,
respectively, and, in the case of any Howell SEC Document amended or superseded
by a filing prior to the date of this Agreement, then on the date of such
amending or superseding filing) (a) did not contain any untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary in order to make the statements therein, in light of the circumstances
under which they were made, not misleading, and (b) complied in all material
respects with the applicable requirements of the Exchange Act and the Securities
Act, as the case may be. The financial statements of Howell and its subsidiaries
included in the Howell SEC Documents at the time filed (and, in the case of
registration statements and proxy statements, on the dates of effectiveness and
the dates of mailing, respectively, and, in the case of any Howell SEC Document
amended or superseded by a filing prior to the date of this Agreement, then on
the date of such amending or superseding filing) complied as to form in all
material respects with applicable accounting requirements and with the published
rules and regulations of the Commission with respect thereto, were prepared in
accordance with United States generally accepted accounting principles ("GAAP")
applied on a consistent basis during the periods involved (except as may be
indicated in the notes thereto, or, in the case of unaudited statements, as
permitted by Form 10-Q of the Commission), and fairly present (subject, in the
case of unaudited statements, to normal, recurring audit adjustments) the
consolidated financial position of Howell and its consolidated subsidiaries as
at the dates thereof and the consolidated results of their operations and cash
flows for the periods then ended. None of Howell's subsidiaries is subject to
the periodic reporting requirements of the Exchange Act or required to file any
form, report or other document with the Commission, The New York Stock Exchange,
Inc. (the "NYSE"), any other stock exchange or any other comparable Governmental
Authority.

     4.8.  Proxy Statement.  None of the information provided by Howell for
inclusion in the Proxy Statement, at the date of mailing and at the date of the
Howell Stockholders Meeting, will contain any untrue statement of a material
fact or omit to state a material fact required to be stated therein or necessary
in order to make the statements therein, in light of the circumstances under
which they were made, not misleading. The Proxy Statement, except for such
portions thereof that relate only to Anadarko and its subsidiaries, will comply
as to form in all material respects with the provisions of the Exchange Act.

     4.9.  Compliance with Law.  Except as to environmental matters (as to which
representations and warranties have been made in Section 4.21) and except as set
forth in Section 4.9 to the Howell Disclosure Schedule, Howell and its
subsidiaries are in compliance in all material respects, and at all times since
January 1, 1998 have been in compliance in all material respects, with all
Applicable Laws relating to Howell and its subsidiaries or their businesses or
properties. To the knowledge of Howell, no investigation or review by any
Governmental Authority with respect to Howell or any of its subsidiaries is
pending or threatened, nor has

                                       A-10
<PAGE>

any Governmental Authority notified Howell in writing of an intention to conduct
such an investigation or review.

     4.10.  Litigation.  Except as set forth in Section 4.10 to the Howell
Disclosure Schedule, there is no suit, claim, action, proceeding, hearing,
notice of violation, demand letter (including audits pertaining to payment of
royalties on federal and state leases) or, to the knowledge of Howell,
investigation (each of the foregoing, an "Action") pending, or, to the knowledge
of Howell, threatened, against Howell or any of its subsidiaries or any
executive officer or director of Howell or any of its subsidiaries which, if
adversely determined, could be material to Howell or its subsidiaries or any of
their respective operations or businesses. Except as set forth in Section 4.10
to the Howell Disclosure Schedule, neither Howell nor any of its subsidiaries is
subject to any outstanding order, writ, injunction or decree that, individually
or in the aggregate, insofar as can be reasonably foreseen, could have a
Material Adverse Effect on Howell or a material adverse effect on the ability of
Howell to consummate the transactions contemplated by this Agreement. Except as
set forth in Section 4.10 to the Howell Disclosure Schedule, since January 1,
1998, neither Howell nor any of its subsidiaries has been subject to any order,
writ, injunction or decree relating to Howell's or any of its subsidiaries'
method of doing business with or its or their relationship with past, existing
or future customers, suppliers or co-venturers of Howell or any of its
subsidiaries.

     4.11.  No Material Adverse Change.  Except as set forth in Section 4.11 to
the Howell Disclosure Schedule, since December 31, 2001, there has not been any
state of facts, change, development, effect, condition, result, consequence,
occurrence or circumstance that, individually or in the aggregate, has had or
could reasonably be expected to have a Material Adverse Effect on Howell or a
material adverse effect on the ability of Howell to consummate the transactions
contemplated by this Agreement.

     4.12.  Taxes.

     (a) Howell and its subsidiaries have duly and timely filed all Tax Returns
(as defined in Section 4.12(e)) (including those filed on a consolidated,
combined or unitary basis) required to have been filed by Howell or any of its
subsidiaries. All of the foregoing Tax Returns are true, complete and correct
(except for such inaccuracies that are, individually or in the aggregate, not
material), and Howell and its subsidiaries have, within the time and manner
prescribed by Applicable Laws, paid or, prior to the Effective Time, will pay
all Taxes required to be paid in respect of the periods covered by such Tax
Returns or otherwise due to any United States federal, state and local and
foreign other taxing authority. Except with respect to certain state Tax Returns
for the 2001 tax year, none of Howell or any of its subsidiaries has requested
or filed any document having the effect of causing any extension of time within
which to file any Tax Returns in respect of any fiscal year that have not since
been filed. No deficiencies for any material Tax have been proposed in writing,
asserted or assessed (tentatively or definitely), in each case, by any taxing
authority, against Howell or any of its subsidiaries for which there have not
been provided adequate reserves in accordance with GAAP. All such proposed
deficiencies are set forth in Section 4.12(a) to the Howell Disclosure Schedule.
Except as set forth in Section 4.12(a) to the Howell Disclosure Schedule and
except for those that, individually or in the aggregate, could not reasonably be
expected to result in a liability of Howell or any of its subsidiaries of more
than $50,000, neither Howell nor any of its subsidiaries is the subject of any
currently ongoing Tax audit. There are no pending requests for waivers of the
time to assess any material Tax other than those made in the ordinary course and
for which payment has been made or for which there are adequate reserves
provided in accordance with GAAP. The United States federal and material state
income tax returns of Howell and each of its subsidiaries have been examined by
and settled with the Internal Revenue Service or other Governmental Authority
for all years through December 31, 1998. The relevant statute of limitations is
closed with respect to all United States federal and material state income tax
returns of Howell and its subsidiaries for all years through December 31, 1998.
Neither Howell nor any of its subsidiaries has waived any statute of limitations
in respect of Taxes or agreed to any extension of time with respect to a Tax
assessment or deficiency which waiver or agreement to extension of time has not
expired. All assessments for taxes due and owing by Howell or any of its
subsidiaries with respect to completed and settled examinations or concluded
litigation have been timely paid. There are no liens with respect to Taxes upon
any of the properties or assets, real or personal, tangible or intangible of
Howell or any of its subsidiaries (other than liens for Taxes not yet due). No
claim has ever been made in writing by an authority in a jurisdiction where none
of Howell and any

                                       A-11
<PAGE>

of its subsidiaries files Tax Returns that Howell or any of its subsidiaries is
or may be subject to taxation by that jurisdiction. None of Howell or any of its
subsidiaries (i) has filed an election under Section 341(f) of the Code to be
treated as a consenting corporation, or (ii) is a "personal holding company"
within the meaning of Section 542 of the Code.

     (b) Except as set forth in Section 4.12(b) to the Howell Disclosure
Schedule, neither Howell nor any of its subsidiaries is obligated by any
contract, agreement or other arrangement to indemnify any other person with
respect to Taxes. Since December 31, 1995, neither Howell nor any of its
subsidiaries has been a party to or bound by any agreement or arrangement
(whether or not written and including any arrangement required or permitted by
law) binding Howell or any of its subsidiaries that (i) requires Howell or any
of its subsidiaries to make any Tax payment to or for the account of any other
person, (ii) affords any other person the benefit of any net operating loss, net
capital loss, investment Tax credit, foreign Tax credit, charitable deduction or
any other credit or Tax attribute that could reduce Taxes (including deductions
and credits related to alternative minimum Taxes) of Howell or any of its
subsidiaries, or (iii) requires or permits, without Howell's consent, the
transfer or assignment of income, revenues, receipts or gains to Howell or any
of its subsidiaries, from any other person other than as set forth on Section
4.12(b) of the Howell Disclosure Schedule.

     (c) Neither Howell nor any of its subsidiaries has constituted either a
"distributing corporation" or a "controlled corporation" (within the meaning of
Section 355(a)(1)(A) of the Code) in a distribution of stock intended to qualify
for tax-free treatment under Section 355 of the Code (i) in the two years prior
to the date of this Agreement (or will constitute such a corporation in the two
years prior to the Closing Date) or (ii) in a distribution that otherwise
constitutes part of a "plan" or "series of related transactions" (within the
meaning of Section 355(e) of the Code) in conjunction with the Merger.

     (d) Howell and its subsidiaries have withheld and paid all Taxes required
to have been withheld and paid in connection with amounts paid or owing to any
employee, independent contractor, creditor, stockholder or other third party.
Neither Howell nor any of its subsidiaries is responsible for any Taxes of any
other person under Treasury Regulation Section 1.1502-6 (or any similar
provision of state, local or foreign law), as a transferee or successor, by
contract, or otherwise.

     (e) "Tax Returns" means returns, reports and forms required to be filed
with any Governmental Authority of the United States or any other jurisdiction
responsible for the imposition or collection of Taxes.

     (f) "Taxes" means (i) all taxes (whether United States federal, state or
local or foreign) based upon or measured by income and any other tax whatsoever,
including gross receipts, profits, sales, use, occupation, value added, ad
valorem, transfer, franchise, withholding, payroll, employment, excise, or real
or personal property taxes, together with any interest or penalties imposed with
respect thereto, and (ii) any obligations under any agreements or arrangements
with respect to any taxes described in clause (i) above.

     4.13.  Intellectual Property.  Howell and its subsidiaries own, or are
validly licensed or otherwise have the right to use, all patents, patent rights,
trademarks, trademark rights, trade names, trade name rights, service marks,
service mark rights, copyrights and other proprietary intellectual property
rights and computer programs (collectively, "Intellectual Property Rights")
which are material to the conduct of the business of Howell and its subsidiaries
taken as a whole. No material claims are pending or, to the knowledge of Howell,
threatened that Howell or any of its subsidiaries is infringing the rights of
any person with regard to any Intellectual Property Right. To the knowledge of
Howell, no person is infringing in any material respect the rights of Howell or
any of its subsidiaries with respect to any Intellectual Property Right.

     4.14.  Title to and Condition of Properties.  Howell and its subsidiaries
own or hold title under valid oil and gas leases, oil leases, gas leases, other
mineral leases, subleases, assignment of operating rights, farmout agreements,
royalty agreements, overriding royalty agreements, and other similar agreements,
surface leases, easements, rights-of-way and deeds, and own or lease under valid
leases the wells, compressors, pipelines, tanks, meters and similar equipment,
machinery and buildings (hereinafter referred to in this Section 4.14 as
"Properties") necessary for the conduct of the businesses of Howell and its
subsidiaries as presently conducted in all material respects. The buildings,
plants, machinery and equipment necessary for the conduct of the businesses of
Howell and its subsidiaries as presently conducted are in all material respects
in good operating

                                       A-12
<PAGE>

condition and repair, are, considering the circumstances of their use, adequate
for the uses to which they are being put, and are not in need of maintenance or
repairs, except for ordinary maintenance and repairs that are not material in
nature or cost.

     4.15.  Employee Benefit Plans.

     (a) For purposes of this Section 4.15, the following terms have the
definitions given below:

          "Controlled Group Liability" means any and all liabilities (i) under
     Title IV of ERISA (as defined below), (ii) under Section 302 of ERISA,
     (iii) under Sections 412 and 4971 of the Code, and (iv) resulting from a
     violation of the continuation coverage requirements of Section 601 et seq.
     of ERISA and Section 4980B of the Code or the group health plan
     requirements of Sections 9801 et seq. of the Code and Sections 701 et seq.
     of ERISA, in each case, other than pursuant to the Plans (as defined below)
     listed in Section 4.15(a) to the Howell Disclosure Schedule.

          "ERISA" means the Employee Retirement Income Security Act of 1974, as
     amended, together with the rules and regulations thereunder.

          "ERISA Affiliate" means, with respect to any entity, trade or
     business, any other entity, trade or business that is a member of a group
     described in Section 414(b), (c), (m) or (o) of the Code or Section
     4001(b)(1) of ERISA that includes the first entity, trade or business, or
     that is a member of the same "controlled group" as the first entity, trade
     or business pursuant to Section 4001(a)(14) of ERISA.

          "Plans" means all employee benefit plans, programs, policies,
     agreements and other arrangements providing compensation or benefits to any
     director, officer or employee or former director, officer or employee in
     respect of services provided to Howell or any of its subsidiaries or to any
     beneficiary or dependent thereof, and whether covering one individual or
     more than one individual, sponsored or maintained by Howell or any of its
     subsidiaries or to which Howell or any of its subsidiaries contributes or
     is obligated to contribute or could have any liability, whether or not
     written, other than any Multiemployer Plan (as defined below). Without
     limiting the generality of the foregoing, the term "Plans" includes any
     defined benefit or defined contribution pension plan, profit sharing plan,
     stock ownership plan, deferred compensation agreement or arrangement,
     vacation pay, sickness, disability or death benefit plan (whether provided
     through insurance, on a funded or unfunded basis or otherwise), employee
     stock option or stock purchase plan, bonus or incentive plan or program,
     severance pay, change of control, termination, reduction in force plan,
     agreement, arrangement or policy (including statutory severance and
     termination indemnity plans), practice or agreement, employment agreement,
     retiree medical benefits plan and each other employee benefit plan, program
     or arrangement including each "employee benefit plan" (within the meaning
     of Section 3(3) of ERISA) other than any Multiemployer Plan.

          "Withdrawal Liability" means liability to a Multiemployer Plan as a
     result of a complete or partial withdrawal from such Multiemployer Plan, as
     those terms are defined in Part I of Subtitle E of Title IV of ERISA.

     (b) Section 4.15(a) to the Howell Disclosure Schedule lists all Plans. With
respect to each Plan, Howell has provided to Anadarko a true, correct and
complete copy of the following (where applicable): (i) each writing constituting
a part of such Plan, including, without limitation, all plan documents
(including amendments), benefit schedules, trust agreements, and insurance
contracts and other funding vehicles; (ii) the three most recent Annual Reports
(Form 5500 Series) and accompanying schedules, if any; (iii) the current summary
plan description, if any; (iv) the most recent annual financial report, if any;
and (v) the most recent determination letter from the Internal Revenue Service,
if any. Except as specifically provided in the foregoing documents provided to
Anadarko, there are no amendments to any Plan that have been adopted or
approved, nor has Howell or any of its subsidiaries undertaken to make any such
amendments or to adopt or approve any new Plan.

     (c) Each Plan that is intended to be a "qualified plan" (within the meaning
of Section 401(a) of the Code) (a "Qualified Plan") has either been filed or
shall be filed with the Internal Revenue Service requesting a qualification
determination during the applicable remedial amendment period, and Howell has no

                                       A-13
<PAGE>

reason to believe that favorable letters will not be granted. There are no
existing circumstances nor any events that have occurred that could adversely
affect the qualified status of any Qualified Plan or the related trust.

     (d) Except as set forth in Section 4.15(d) to the Howell Disclosure
Schedule, all material contributions required to be made by Howell or any of its
subsidiaries or any of their respective ERISA Affiliates to any Plan by
Applicable Laws or by any plan document or other contractual undertaking, and
all material premiums due or payable with respect to insurance policies funding
any Plan, for any period through the date of this Agreement have been timely
made or paid in full and through the Closing Date will be timely made or paid in
full.

     (e) Howell and its subsidiaries and their respective ERISA Affiliates have
complied, and are now in compliance, in all material respects, with all
provisions of ERISA, the Code and all laws and regulations (including any local
Applicable Laws) applicable to the Plans. Each Plan has been operated in all
material respects in accordance with its terms. There is not now, and there are
no existing circumstances that could reasonably be expected to give rise to, any
requirement for the posting of security with respect to a Plan or the imposition
of any pledge, lien, security interest or encumbrance on the assets of Howell or
any of its subsidiaries or any of their respective ERISA Affiliates under ERISA
or the Code.

     (f) No Plan is subject to Title IV or Section 302 of ERISA or Section 412
or 4971 of the Code. No Plan is a "multiemployer plan" (within the meaning of
Section 4001(a)(3) of ERISA) (a "Multiemployer Plan") or a plan that has two or
more contributing sponsors at least two of whom are not under common control
(within the meaning of Section 4063 of ERISA) (a "Multiple Employer Plan"). None
of Howell and any of its subsidiaries nor any of their respective ERISA
Affiliates, at any time within six years before the date of this Agreement,
contributed to or has been obligated to contribute to any Multiemployer Plan or
Multiple Employer Plan. None of Howell and any of its subsidiaries nor any of
their respective ERISA Affiliates has incurred any Withdrawal Liability that has
not been satisfied in full.

     (g) To the knowledge of Howell, there does not now exist, and there are no
existing circumstances that could reasonably be expected to result in, any
material Controlled Group Liability that would be a liability of Howell or any
of its subsidiaries following the Closing. Without limiting the generality of
the foregoing, neither Howell nor any of its subsidiaries nor any of their
respective ERISA Affiliates has engaged in any transaction described in Section
4069 or Section 4204 of ERISA.

     (h) Except for health continuation coverage as required by Section 4980B of
the Code or Part 6 of Title I of ERISA, neither Howell nor any of its
subsidiaries has any material liability for life, health, medical or other
welfare benefits to former employees or beneficiaries or dependents thereof. To
the knowledge of Howell, there has been no communication to employees of Howell
or its subsidiaries that could reasonably be expected or interpreted to promise
or guarantee such employees retiree health or life insurance benefits or other
retiree death benefits on a permanent basis.

     (i) Except as disclosed in Section 4.15(i) to the Howell Disclosure
Schedule, neither the execution and delivery of this Agreement nor the
consummation of the transactions contemplated by this Agreement will result in,
cause the accelerated vesting or delivery of, or increase the amount or value
of, any payment or benefit to any employee, officer, director or consultant of
Howell or any of its subsidiaries (either alone or in conjunction with any other
event). Except as disclosed in Section 4.15(i) to the Howell Disclosure
Schedule, no amount paid or payable by Howell or any of its subsidiaries in
connection with the transactions contemplated by this Agreement, either solely
as a result thereof or as a result of the transactions contemplated by this
Agreement in conjunction with any other events, will be an "excess parachute
payment" (within the meaning of Section 280G of the Code). Section 4.15(i) of
the Howell Disclosure Schedule sets forth the maximum aggregate amount payable
to employees of Howell and its subsidiaries with respect to (i) severance, (ii)
"excess parachute payments," and (iii) gross-up payments in respect of excise
tax liabilities imposed under Section 280G of the Code.

     (j) There are no pending, or, to the knowledge of Howell, threatened,
Actions (other than claims for benefits in the ordinary course) that have been
asserted or instituted against any Plan, any fiduciaries thereof with respect to
their duties to any Plan or the assets of any of the trusts under any Plan that
could reasonably

                                       A-14
<PAGE>

be expected to result in any material liability of Howell or any of its
subsidiaries to the Pension Benefit Guaranty Corporation, the United States
Department of Treasury, the United States Department of Labor or any
Multiemployer Plan.

     (k) Section 4.15(k) to the Howell Disclosure Schedule sets forth the names
of all directors and officers of Howell and any increase or change in the total
salary, bonus, and fringe benefits and perquisites (to the extent such fringe
benefits or perquisites would have to be disclosed under Rule 402(b) of
Regulation S-K under the Exchange Act, assuming each such individual was a named
executive officer) each will be eligible to receive for the fiscal year ending
December 31, 2002 as compared to the amounts thereof which are disclosed in
Howell's proxy statement for its 2002 annual meeting of stockholders, and any
changes to the foregoing that will occur as a matter of entitlement subsequent
to December 31, 2002. Section 4.15(k) to the Howell Disclosure Schedule also
sets forth the liability of Howell and its subsidiaries for deferred
compensation under any deferred compensation plan, excess plan or similar
arrangement (other than pursuant to Qualified Plans) to each such director,
officer and employee and to all other employees as a group, together with the
value, as of the date specified thereon, of the assets (if any) set aside in any
grantor trust(s) to fund such liabilities. Except as disclosed in Section
4.15(k) to the Howell Disclosure Schedule, there are no other material forms of
compensation paid to any such director, officer or employee of Howell. Except as
set forth in Section 4.15(k) to the Howell Disclosure Schedule, no officer,
director, or employee of Howell or any of its affiliates, or any immediate
family member of any of the foregoing, provides or causes to be provided to
Howell any material assets, services or facilities, and Howell does not provide
or cause to be provided to any such officer, director, employee or affiliate, or
any immediate family member of any of the foregoing, any material assets,
services or facilities.

     (l) None of Howell and its subsidiaries nor to the knowledge of Howell any
other person, including any fiduciary, has engaged in any "prohibited
transaction" (as defined in Section 4975 of the Code or Section 406 of ERISA),
which could subject any of the Plans or their related trusts, Howell, any of its
subsidiaries or any person that Howell or any of its subsidiaries has an
obligation to indemnify, to any material tax or penalty imposed under Section
4975 of the Code or Section 502 of ERISA.

     (m) No Plan is subject to the laws of any jurisdiction outside of the
United States and no director, officer, employee or consultant of Howell or any
of its subsidiaries is subject to the laws of any jurisdiction outside of the
United States in connection with such individual's performance of services for
Howell or any of its subsidiaries in any such jurisdiction.

     (n) Except as disclosed in Section 4.15(n) to the Howell Disclosure
Schedule, no disallowance of a deduction under Section 162(m) of the Code for
employee reimbursement of any amount paid or payable by Howell or any of its
subsidiaries has occurred or is reasonably expected to occur.

     (o) Section 4.15(o) to the Howell Disclosure Schedule sets forth a list of
all individuals with whom Howell or any of its subsidiaries has entered into
employment agreements and none of such employment agreements have been entered
into, amended or supplemented during the 12-month period prior to the date of
this Agreement, except to the extent disclosed in Section 4.15(o) to the Howell
Disclosure Schedule. Howell has not waived any of its rights under such
employment agreements.

     (p) Howell and its subsidiaries have in the past been and are in compliance
in all material respects with Applicable Laws respecting employment, employment
practices, employee classification, labor relations, safety and health, wages,
hours and terms and conditions of employment. Howell and its subsidiaries have
complied in all material respects with their payment obligations to all
employees of Howell and its subsidiaries in respect of all wages, salaries,
commissions, bonuses, benefits and other compensation due and payable to such
employees under each Howell policy, practice, agreement, plan, program or
Applicable Laws.

     (q) Neither Howell nor any of its subsidiaries, directly or indirectly,
maintains any loan to or for any of its directors or executive officers (or
equivalents thereof).

     4.16.  Contracts.  Section 4.16 to the Howell Disclosure Schedule lists, as
of the date of this Agreement, all written or oral contracts, agreements,
guarantees, leases and executory commitments, other than Plans, to which Howell
or any of its subsidiaries is a party and that fall within any of the following

                                       A-15
<PAGE>

categories, excluding any of the foregoing which is no longer in effect and
which cannot result in any liability or obligation of or by Howell or any of its
subsidiaries (each, a "Contract"): (a) Contracts not entered into in the
ordinary course of Howell's or any of its subsidiaries' business other than
those that are not material to the business of Howell or any of its
subsidiaries, (b) joint venture, partnership and similar agreements, including
joint operating agreements relating to assets and operations in Wyoming and in
the portion of the Elk Basin Field located in Montana, and excluding joint
operating agreements relating to assets and operations elsewhere, and excluding
tax partnership agreements entered into in connection with operating
agreements), (c) Contracts that are service contracts or equipment leases
involving payments by Howell and any of its subsidiaries, in the aggregate, of
more than $100,000 per year, (d) Contracts containing covenants purporting to
limit the freedom of Howell or any of its subsidiaries to compete in any line of
business in any geographic area or to hire any individual or group of
individuals, (e) Contracts that, after the Effective Time, would have the effect
of limiting the freedom of Anadarko or any of its subsidiaries (other than
Howell and any of its subsidiaries) to compete in any line of business in any
geographic area or to hire any individual or group of individuals, (f) Contracts
that contain minimum purchase conditions in excess of $100,000 or requirements
or other terms that restrict or limit the purchasing relationships of Howell or
any of its affiliates, (g) Contracts relating to any outstanding commitment for
any expenditures, including capital expenditures, in excess of $100,000, (h)
Contracts relating to the lease (excluding oil, gas and other mineral leases) or
sublease of or sale or purchase of real or personal property not cancelable by
Howell or any of its subsidiaries (without premium or penalty) within one month
involving payments over its term in excess of $100,000, (i) Contracts with any
labor organization or union, (j) indentures, mortgages, promissory notes, loan
agreements, guarantees of borrowed money in excess of $100,000, letters of
credit or other agreements or instruments of Howell or any of its subsidiaries
or commitments for the borrowing or the lending of amounts in excess of $100,000
by Howell or any of its subsidiaries or providing for the creation of any
charge, security interest, financial encumbrance or lien upon any of the assets
of Howell or any of its subsidiaries, (k) Contracts involving annual revenues to
the businesses of Howell or any of its subsidiaries in excess of $1,000,000, (l)
Contracts providing for "earn-outs", "savings guarantees", "performance
guarantees", or other contingent payments by Howell or any of its subsidiaries
involving more than $100,000 over the term of the Contract, (m) Contracts with
or for the benefit of any of Howell's affiliates or immediate family member
thereof (other than Howell's subsidiaries) involving more than an aggregate of
$50,000 per year, (n) Contracts outside the ordinary course of business
involving payments by Howell or any of its subsidiaries of more than $100,000
per year, (o) Contracts with respect to sales, transportation or processing of
oil, gas or other hydrocarbons or products which by their terms may not be
terminated without premium or penalty on thirty (30) days prior written notice
by Howell or any of its subsidiaries, (p) any hedging agreement, being any
commodity, interest rate, currency swap, cap, floor, collar, forward agreement
or other exchange or protection agreements or any option with respect to any
such transaction, (q) any confidentiality agreements, (r) Contracts that contain
an area of mutual interest ("AMI") provision, where such AMI provision is
applicable to assets and operations in Wyoming and in the portion of the Elk
Basin Field located in Montana, (s) Contracts obligating Howell or any of its
subsidiaries, by virtue of any prepayment arrangement, take or pay agreement or
similar arrangement to deliver oil, gas, other hydrocarbons, or any other
associated substances produced from the properties of Howell or its subsidiaries
at some future time without then receiving full payment therefor in all material
respects, other than gas imbalances (i) less than $50,000 or (ii) between Howell
or any of its subsidiaries and Anadarko or any of its subsidiaries, (t)
Contracts providing an entity with a call upon, option to purchase, or similar
right to purchase any assets or goods (including any portion of oil, gas, other
hydrocarbons or any other minerals) from Howell or its subsidiaries' properties
at a price less than the prevailing market price therefor, (u) Contracts, other
than to Anadarko, obligating Howell or its subsidiaries to sell, transfer,
assign, or otherwise convey any oil and gas leases, overriding royalty
interests, royalty interests or other mineral leases or interests covering in
excess of 40 gross acres, and (v) Contracts obligating Howell or its
subsidiaries to purchase, obtain or otherwise acquire any interests in
Properties (as that term is defined in Section 4.14) where consideration to be
paid is greater than $100,000. All such Contracts and all other Contracts that
are material to the businesses or operations of Howell or any of its
subsidiaries are valid and binding obligations of Howell or of its subsidiary,
and, to the knowledge of Howell or its subsidiary, the valid and binding
obligation of each other party thereto, except such Contracts that, if not so
valid and binding, could not, individually or in the aggregate, have a Material
Adverse Effect on Howell. None of Howell, any of

                                       A-16
<PAGE>

its subsidiaries, and, to the knowledge of Howell, any other party thereto, is
in violation of or in default in respect of, nor has there occurred an event or
condition that with the passage of time or giving of notice (or both) could
constitute a default under or permit the termination of, any such Contract or of
any other Contract that is material to the business or operations of Howell or
any of its subsidiaries, except such violations or defaults under or
terminations which, individually or in the aggregate, could not have a Material
Adverse Effect on Howell.

     4.17.  Labor Matters.  Neither Howell nor any of its subsidiaries have any
collective bargaining agreements or employment (except as set forth in Section
4.15(o) to the Howell Disclosure Schedule) or consulting agreements with any
persons employed by Howell or any of its subsidiaries or any persons otherwise
performing services primarily for Howell or any of its subsidiaries. There is no
labor strike, dispute or stoppage pending, or, to the knowledge of Howell or any
of its subsidiaries, threatened, against Howell or any of its subsidiaries, and
neither Howell nor any of its subsidiaries has experienced any labor strike,
dispute or stoppage or other material labor difficulty involving its employees
since January 1, 1998. To the knowledge of Howell, since January 1, 1998, no
campaign or other attempt for recognition has been made by any labor
organization or employees with respect to employees of Howell or any of its
subsidiaries.

     4.18.  Undisclosed Liabilities.  Except (a) as and to the extent disclosed
or reserved against on the balance sheet of Howell as of December 31, 2001
included in the Howell SEC Documents, or (b) as incurred after the date thereof
in the ordinary course of business consistent with prior practice and not
prohibited by this Agreement, neither Howell nor its subsidiaries have any
liabilities or obligations of any nature, whether known or unknown, absolute,
accrued, contingent or otherwise and whether due or to become due, that,
individually or in the aggregate, have or could reasonably be expected to have a
Material Adverse Effect on Howell.

     4.19.  Operation of Howell's Business; Relationships.

     (a) Except as set forth in Section 4.19(a) to the Howell Disclosure
Schedule, since December 31, 2001 through the date of this Agreement, neither
Howell nor any of its subsidiaries has engaged in any transaction that, if done
after execution of this Agreement, would violate Section 5.3(c) (other than
clauses (xiii), (xiv) and (xvii) of Section 5.3(c)).

     (b) Except as set forth in Section 4.19(b) to the Howell Disclosure
Schedule, since December 31, 2001, no material customer of Howell or any of its
subsidiaries has indicated that it will stop or materially decrease purchasing
products from Howell or its subsidiary, or is otherwise involved in, or is
threatening, a material dispute with Howell or its subsidiaries. Section 4.19(b)
to the Howell Disclosure Schedule describes each termination or nonrenewal
(excluding any expiration in the ordinary course of business) that has occurred
during the 2001 calendar year with respect to any Contract with any customer
involving payments in excess of $250,000 per year. Section 4.19(b) to the Howell
Disclosure Schedule also describes each termination or nonrenewal (excluding any
expiration in the ordinary course of business) that has occurred between January
1, 2002 and the date of this Agreement with respect to any Contract with any
customer involving payments reasonably expected to be in excess of $250,000 for
the 2002 calendar year or with any customer that made payments in excess of
$250,000 during any of the three calendar years ending December 31, 2001.

     4.20.  Permits; Compliance.  Except as to environmental matters (as to
which representations and warranties have been made in Section 4.21), Howell and
its subsidiaries are in possession of all material franchises, grants,
authorizations, licenses, permits, easements, variances, exemptions, consents,
certificates, approvals and orders required by Applicable Laws to own, lease and
operate its properties and to carry on its businesses as they are now being
conducted (collectively, the "Howell Permits"), and there is no Action pending,
or, to the knowledge of Howell, threatened, regarding any of the Howell Permits.
Howell is in material compliance with the Howell Permits.

     4.21.  Environmental Matters.  Except as disclosed in Section 4.21 to the
Howell Disclosure Schedule, (a) the properties, operations and activities of
Howell and its subsidiaries are in compliance in all material respects with all
applicable Environmental Law (as defined below) and all past noncompliance of
Howell or any of its subsidiaries with any Environmental Law or Environmental
Permits (as defined below) has been

                                       A-17
<PAGE>

resolved without any pending or, to the knowledge of Howell, future material
cost or liability to Howell or any of its subsidiaries; (b) Howell and its
subsidiaries and the properties and operations of Howell and its subsidiaries
are not subject to any material existing, pending, or, to the knowledge of
Howell, threatened, Action by or before any Governmental Authority under any
Environmental Law; (c) there has been no Release (as defined below) of any
chemicals, contaminants, or industrial, toxic, hazardous or radioactive
substances, wastes or other pollutants (including petroleum or petroleum
distillates, asbestos or asbestos-containing material) regulated by
Environmental Law (collectively, "Hazardous Materials") by Howell or its
subsidiaries in connection with their current or former properties or operations
for which Howell or any of its subsidiaries could reasonably be expected to
incur material liability under Environmental Law; and (d) there has been no
material exposure of any person to Hazardous Materials in connection with the
current or former properties, operations and activities of Howell and its
subsidiaries other than those the consequences of which would not be material to
Howell or any of its subsidiaries. "Release" means any actual or threatened
release, spill, emission, leaking, dumping, injection, pouring, disposal,
discharge, leaching or migration into or through the environment (including
ambient air, surface water, groundwater, land surface or subsurface strata).
"Environmental Law" means all Applicable Laws (excluding policies) governing
pollution or protection of the environment or human health or the environment
and safety. "Environmental Permit" means any permit, approval, grant, consent,
exemption, certificate, order, easement, variance, franchise, license or other
authorization required under or issued pursuant to any applicable Environmental
Laws.

     4.22.  Accounts Receivable.  All accounts and notes receivable of Howell
and any of its subsidiaries represent valid obligations arising from sales
actually made or services actually performed and have arisen in the ordinary
course of business, and the accounts receivable reserve reflected in the balance
sheet of Howell as of December 31, 2001 included in the Howell SEC Documents is
as of such date adequate and established in accordance with GAAP consistently
applied. Since December 31, 2001, to the knowledge of Howell there has been no
event or occurrence that, when considered individually or together with all such
other events or occurrences, would cause such accounts receivable reserve to be
inadequate, and that could, individually or in the aggregate, reasonably be
expected to have a Material Adverse Effect on Howell.

     4.23.  Insurance.  Except as set forth in Section 4.23 to the Howell
Disclosure Schedule, each of Howell and its subsidiaries is, and has been
continuously since January 1, 1998, insured with financially responsible
insurers or under other financially responsible arrangements in such amounts and
against such risks and losses as are customary for companies engaged in a
similar business and acting in accordance with good business practice. Howell's
and its subsidiaries' insurance policies are in all material respects in full
force and effect in accordance with their terms, no notice of cancellation has
been received, and there is no existing default or event that, with the giving
of notice or lapse of time or both, would constitute a default thereunder; all
premiums thereunder to date have been paid in full. Set forth in Section 4.23 to
the Howell Disclosure Schedule is the amount of the annual premium currently
paid by Howell and its subsidiaries for its directors' and officers' liability
insurance.

     4.24.  Opinion of Financial Advisor.  The Board of Directors of Howell has
received the written opinion of BMO Nesbitt Burns, Howell's financial advisor,
to the effect that, as of the date of this Agreement, the consideration to be
received by Howell Stockholders pursuant to the Merger is fair to Howell
Stockholders from a financial point of view, Howell has provided a copy of such
opinion to Anadarko, and such opinion has not been withdrawn or revoked or
otherwise modified. Howell has received the consent of BMO Nesbitt Burns to
include such written opinion in the Proxy Statement.

     4.25.  Board Recommendation; Required Vote.  The Board of Directors of
Howell, at a meeting duly called and held, has, by unanimous vote of those
directors present (who constituted 100% of the directors then in office), (a)
approved this Agreement, and deem this Agreement, the Merger and the
transactions contemplated by this Agreement advisable, fair to and in the best
interests of Howell Stockholders; (b) approved this Agreement and the
transactions contemplated by this Agreement, including the Merger, in all
respects, and such approval constitutes approval of this Agreement, the Merger
and the Support Agreements for purposes of Section 203 of the DGCL; and (c)
resolved to recommend that the holders of Howell Common Stock approve and adopt
this Agreement, including the Merger (the "Howell Board Recommendation"). The
affirmative vote of holders of a majority of the outstanding shares of Howell

                                       A-18
<PAGE>

Common Stock to adopt this Agreement is the only vote of the holders of any
class or series of Howell capital stock necessary to adopt this Agreement and
approve the transactions contemplated by this Agreement, including the Merger.

     4.26.  Section 203 of the DGCL.  Prior to the date of this Agreement, the
Board of Directors of Howell has taken all action necessary to exempt under or
make not subject to (a) the provisions of Section 203 of the DGCL and (b) any
other applicable state takeover law or state law that purports to limit or
restrict business combinations or the ability to acquire or vote shares: (i) the
execution of this Agreement and the Support/ Voting Agreements, dated as of the
date hereof, between Anadarko and certain Howell Stockholders (collectively, the
"Support Agreements"), (ii) the Merger, and (iii) the transactions contemplated
by this Agreement and the Support Agreements.

                                   ARTICLE V

                            COVENANTS OF THE PARTIES

     The parties to this Agreement agree that:

     5.1.  Mutual Covenants.

     (a) HSR Act Filings; Reasonable Efforts; Notification.

     (i) Each of Anadarko and Howell shall (A) make or cause to be made the
filings required of such party to this Agreement or any of its subsidiaries or
affiliates under the HSR Act, if applicable, with respect to the transactions
contemplated by this Agreement as promptly as practicable and in any event
within seven business days after the date of this Agreement, (B) comply at the
earliest practicable date with any request under the HSR Act, if applicable, for
additional information, documents, or other materials received by such party to
this Agreement or any of its subsidiaries from the United States Federal Trade
Commission or the United States Department of Justice or any other Governmental
Authority in respect of such filings or such transactions, and (C) cooperate
with the other parties to this Agreement in connection with any such filing, if
applicable (including, with respect to the party to this Agreement making a
filing, providing copies of all such documents to the non-filing parties to this
Agreement and its advisors prior to filing and, if requested, to accept all
reasonable additions, deletions or changes suggested in connection therewith)
and in connection with resolving any investigation or other inquiry of any such
agency or other Governmental Authority under any Antitrust Laws (as defined in
Section 5.1(a)(ii)) with respect to any such filing or any such transaction.
Each party hereto shall use all reasonable efforts to furnish to each other all
information required for any application or other filing to be made pursuant to
any Applicable Laws in connection with the Merger and the other transactions
contemplated by this Agreement. Each party hereto shall promptly inform the
other parties hereto of any communication with, and any proposed understanding,
undertaking, or agreement with, any Governmental Authority regarding any such
filings or any such transaction. No party hereto shall independently participate
in any meeting, or engage in any substantive conversation, with any Governmental
Authority in respect of any such filings, investigation, or other inquiry
without giving the other party hereto prior notice of the meeting and, to the
extent permitted by such Governmental Authority, the opportunity to attend
and/or participate. The parties hereto will consult and cooperate with one
another, in connection with any analyses, appearances, presentations, memoranda,
briefs, arguments, opinions and proposals made or submitted by or on behalf of
any party hereto in connection with proceedings under or relating to the HSR
Act, if applicable, or other Antitrust Laws. Anadarko and Howell may, as each
deems advisable and necessary, reasonably designate any competitively sensitive
material provided to the other under this Section 5.1 for review by "outside
counsel only." Such materials and the information contained therein shall be
given only to the outside legal counsel of the recipient and will not be
disclosed by such outside counsel to employees, officers or directors of the
recipient unless express permission is obtained in advance from the source of
the materials (Anadarko or Howell, as the case may be) or its legal counsel,
provided, however, that materials concerning the valuation of Howell may be
redacted.

     (ii) Each of Anadarko and Howell shall use commercially reasonable efforts
to resolve such objections, if any, as may be asserted by any Governmental
Authority with respect to the transactions contemplated by

                                       A-19
<PAGE>

this Agreement under the HSR Act, the Sherman Act, as amended, the Clayton Act,
as amended, the Federal Trade Commission Act, as amended, and any other United
States federal or state or foreign statutes, rules, regulations, orders,
decrees, administrative or judicial doctrines or other laws that are designed to
prohibit, restrict or regulate actions having the purpose or effect of
monopolization or restraint of trade (collectively, "Antitrust Laws"). In
connection therewith, if any Action is instituted (or threatened to be
instituted) challenging any of the transactions contemplated by this Agreement
as violative of any Antitrust Laws, each of Anadarko and Howell shall cooperate
and use commercially reasonable efforts vigorously to contest and resist any
such Action, and to have vacated, lifted, reversed, or overturned any decree,
judgment, injunction or other order whether temporary, preliminary or permanent,
that is in effect and that prohibits, prevents, or restricts consummation of the
Merger or any other transactions contemplated by this Agreement, including by
vigorously pursuing all available avenues of administrative and judicial appeal
and all available legislative action unless, by mutual agreement, Anadarko and
Howell decide that litigation is not in their respective best interests.
Notwithstanding the foregoing or any other provision of this Agreement, nothing
in this Section 5.1(a) shall limit a party hereto's right to terminate this
Agreement pursuant to Section 7.1, so long as such party hereto has, up to then,
complied in all material respects with its obligations under this Section
5.1(a).

     (iii) Each of the parties hereto agrees to use commercially reasonable
efforts to take, or cause to be taken, all actions, and to do, or cause to be
done, and to assist and cooperate with the other parties hereto in doing, all
things necessary, proper or advisable to consummate and make effective, in the
most expeditious manner reasonably practicable, the Merger and the transactions
contemplated by this Agreement, including (A) the obtaining of all other
necessary actions or nonactions, waivers, consents, licenses, permits,
authorizations, orders and approvals from Governmental Authorities and the
making of all other necessary registrations and filings (including other filings
with Governmental Authorities, if any), (B) the obtaining of all consents,
approvals or waivers from third parties related to or required in connection
with the Merger that are necessary to consummate the Merger and the transactions
contemplated by this Agreement or required to prevent a Material Adverse Effect
on Howell from occurring prior to or after the Effective Time, (C) the
preparation of the Proxy Statement, and (D) the execution and delivery of any
additional instruments necessary to consummate the transactions contemplated by,
and to fully carry out the purposes of, this Agreement, and, unless prohibited
by Applicable Laws, the providing of all such information concerning such party,
its subsidiaries, its affiliates and its subsidiaries' officers, directors,
employees and partners as may be reasonably requested in connection with any of
the matters set forth in this subclause (iii).

     (iv) Notwithstanding anything to the contrary in this Agreement, (A)
neither Anadarko nor any of its subsidiaries shall be required to hold separate
(including by trust or otherwise) or to divest any of their respective
businesses or assets (including, following the Effective Time, any of the
businesses or assets of the Surviving Corporation and its subsidiaries), or to
take or agree to take any action or agree to any limitation with respect to the
ownership or holding of any of their respective businesses or assets (including,
following the Effective Time, any of the businesses or assets of the Surviving
Corporation and its subsidiaries), (B) prior to the Effective Time, neither
Howell nor any of its subsidiaries shall be required to hold separate (including
by trust or otherwise) or to divest any of their respective businesses or
assets, or to take or agree to take any other action or agree to any limitation
with respect to the ownership or holding of any of their respective businesses
or assets, (C) neither any party hereto nor their respective subsidiaries shall
be required to take any action that would, or could reasonably be expected to,
substantially impair the benefits expected, as of the date of this Agreement, to
be realized by Anadarko from consummation of the Merger, and (D) no party to
this Agreement shall be required to waive any of the conditions to the Merger
set forth in Article VI as they apply to such party to this Agreement.

     (b) Public Announcements.  Unless otherwise required by Applicable Laws or
requirements of the NYSE (and, in that event, only if time does not permit), at
all times prior to the earlier of the Effective Time or termination of this
Agreement pursuant to Section 7.1, Howell and Anadarko shall consult with each
other before issuing any press release with respect to the Merger and the
transactions contemplated by this Agreement, and shall use all reasonable
efforts not to issue any such press release prior to such consultation.

                                       A-20
<PAGE>

     (c) Obligations of Anadarko and Howell.  Whenever this Agreement requires
any of Anadarko's subsidiaries (including Subcorp) to take any action, such
requirement shall be deemed to include an undertaking on the part of Anadarko to
cause such subsidiary to take such action. Whenever this Agreement requires any
of Howell's subsidiaries to take any action, such requirement shall be deemed to
include an undertaking on the part of Howell to cause such subsidiary to take
such action and, after the Effective Time, on the part of the Anadarko and the
Surviving Corporation to cause such subsidiary to take such action.

     (d) Conveyance Taxes.  Howell and Anadarko shall cooperate in the
preparation, execution and filing of all Tax Returns, questionnaires,
applications or other documents regarding any real property transfer or gains,
sales, use, transfer, value added, stock transfer and stamp taxes, any transfer,
recording, registration and other fees, and any similar Taxes that become
payable in connection with the transactions contemplated by this Agreement that
are required or permitted to be filed on or before the Effective Time.

     5.2.  Covenants of Anadarko.

     (a) Information for the Preparation of the Proxy Statement.  Anadarko shall
promptly furnish Howell with all information concerning it as may be required
for inclusion in the Proxy Statement. Anadarko shall cooperate with Howell in
the preparation of the Proxy Statement. If, at any time prior to the Effective
Time, Anadarko shall obtain knowledge of any information pertaining to Anadarko
contained in or omitted from the Proxy Statement that would require an amendment
or supplement to the Proxy Statement, Anadarko will so advise Howell in writing.
Anadarko shall promptly furnish to Howell all information concerning it as may
be required for supplementing the Proxy Statement. Anadarko shall use all
reasonable efforts to assist Howell in clearing the Proxy Statement with the
Staff of the Commission.

     (b) Indemnification; Directors' and Officers' Insurance.

     (i) From and after the Effective Time, Anadarko shall cause the Surviving
Corporation to indemnify and hold harmless the present and former officers and
directors of Howell (each an "Indemnified Party" and, collectively, the
"Indemnified Parties") in respect of acts or omissions occurring prior to the
Effective Time (whether asserted or claimed prior to, at or after the Effective
Time and including actions and omissions in respect of this Agreement, the
Merger and the other transactions contemplated by this Agreement) (the
"Indemnified Liabilities")) to the extent provided under the Howell Certificate
or the Howell By-laws. Each Indemnified Party shall be entitled to the
advancement of expenses to the extent provided under the Howell Certificate or
the Howell By-laws in connection with any such action; provided, however, that
any person to whom expenses are advanced provides an undertaking to repay such
advances if it is ultimately determined that such person is not entitled to
indemnification;

     (ii) Anadarko shall cause the Surviving Corporation to honor in accordance
with their respective terms the indemnification agreements set forth in Section
5.2(b) to the Howell Disclosure Schedule, complete and correct copies of which
have been provided to Anadarko prior to the execution of this Agreement; and

     (iii) Anadarko shall use reasonable efforts to cause the Surviving
Corporation or Anadarko to obtain and maintain in effect, for a period of six
years after the Effective Time, from Howell's current insurers or others,
policies of directors' and officers' liability insurance at no cost to the
beneficiaries thereof with respect to acts or omissions occurring prior to the
Effective Time and shall use reasonable efforts to obtain substantially the same
coverage and substantially similar terms and conditions as existing policies;
provided, however, that neither the Surviving Corporation nor Anadarko shall be
required to pay an aggregate premium for such insurance coverage in respect of
any policy year which is in excess of 150% of the amount paid in respect of the
policy year ending August 10, 2003 for such insurance coverage set forth in
Section 4.23 to the Howell Disclosure Schedule, but, in such case, shall
purchase the best available coverage which it determines is reasonably available
for such amount.

     (c) Employee Benefit Matters.

     (i) For purposes hereof, "Affected Employees" shall mean those individuals
who are employees of Howell and its subsidiaries (including those employees who
are on vacation, leave of absence, disability or maternity leave) as of the
Effective Time.

                                       A-21
<PAGE>

     (ii) Anadarko shall, and shall cause the Surviving Corporation to, give the
Affected Employees credit, for purposes of eligibility to participate and
vesting, but not for accrual of benefits, under any employee welfare benefit
plans (other than for purposes of retiree welfare benefit plans), including,
without limitation, such plans as defined in Section 3(1) of ERISA, maintained
by Anadarko, the Surviving Corporation and their respective subsidiaries for the
Affected Employees' service with Howell and its subsidiaries to the same extent
recognized by Howell and its subsidiaries immediately prior to the Effective
Time in any Plans in which such Affected Employees participate immediately prior
to the Effective Time.

     (iii) Anadarko shall cause the Surviving Corporation to waive or continue
to waive any preexisting-condition exclusions to coverage, any
evidence-of-insurability requirements, and any waiting-period requirements, with
respect to participation and coverage requirements applicable to the Affected
Employees under any employee welfare benefit plans in which such employees may
be eligible to participate after the Effective Time to the extent waived under
substantially similar Plans immediately prior to the Effective Time; provided
that, with respect to participation in any employee welfare benefit plan of
Anadarko after the Effective Time, the Affected Employee must enroll within
thirty-one days of first eligibility.

     (iv) Anadarko shall, and shall cause the Surviving Corporation to, give the
Affected Employees credit for purposes of eligibility and vesting, but not for
accrual of benefits, under any employee pension benefit plans, as defined in
Section 3(2) of ERISA, maintained by Anadarko and its subsidiaries.

     (v) Anadarko currently intends to cause the Surviving Corporation to
provide benefits to each employee of Howell and its subsidiaries who continues
employment with the Surviving Corporation and its subsidiaries after the
Effective Time that are no less favorable in the aggregate to such employees
than the benefits provided to similarly situated employees of Anadarko and its
subsidiaries. Nothing herein shall be construed as (i) guaranteeing any Affected
Employee the right to continued employment following the Effective Time or (ii)
limiting Anadarko's right to amend, modify or terminate any Plan, in which
Affected Employees are eligible to participate following the Effective Time
(except as provided in clause (vi) below).

     (vi) Anadarko hereby agrees to honor, as of the Effective Time, the
provisions of Howell's: Severance Program for Executives; Retention and
Severance Program for Employees Not Based in Houston, Texas; Retention and
Severance Program for Employees Based in Houston, Texas; Retention and Severance
Program for Key Employees -- Field; and Retention and Severance Program for Key
Employees -- Non-Field, as each is attached to Sections 5.2(c)(vi)(1),
5.2(c)(vi)(2), 5.2(c)(vi)(3), 5.2(c)(vi)(4) and 5.2(c)(vi)(5), respectively, to
the Howell Disclosure Schedule.

     (vii) Immediately prior to the Effective Time, Howell shall amend as of the
Effective Time its 401(k) Plan and Trust to provide that, notwithstanding any
vesting schedule therein, all contributions made to such plan, whether made by
Howell or by the participants, and all earnings thereon shall be fully vested
(non-forfeitable) to the participants and shall no longer be subject to the
vesting schedule contained therein.

     5.3.  Covenants of Howell.

     (a) Howell Stockholders Meeting.  Howell shall take all action in
accordance with the United States federal securities laws, the DGCL, the Howell
Certificate and the Howell By-laws necessary to duly call, give notice of,
convene and hold a special meeting of the holders of Howell Common Stock (the
"Howell Stockholders Meeting") to be held on the earliest practicable date
determined in consultation with Anadarko to consider and vote upon approval of
the Merger, this Agreement and the transactions contemplated by this Agreement.
Howell shall take all lawful actions to solicit the approval of the Merger, this
Agreement and the transactions contemplated by this Agreement, by the holders of
Howell Common Stock, and the Board of Directors of Howell shall recommend
approval of the Merger, this Agreement and the transactions contemplated by this
Agreement by the holders of Howell Common Stock. Howell shall, through the Board
of Directors of Howell, recommend to the holders of Howell Common Stock,
approval and adoption of this Agreement, and approval of the Merger and the
transactions contemplated by this Agreement, and, except as expressly permitted
by this Agreement, shall not withdraw, amend or modify in a manner adverse to
Anadarko the Howell Board Recommendation. Howell shall ensure that the Howell
Stockholders Meeting is called, noticed, convened, held and conducted, and that
all proxies solicited in connection with the Howell

                                       A-22
<PAGE>

Stockholders Meeting are solicited, in compliance with all Applicable Laws.
Without limiting the generality of the foregoing, (i) Howell agrees that its
obligation to duly call, give notice of, convene and hold the Howell
Stockholders Meeting, as required by this Section 5.3, shall not be affected by
the withdrawal, amendment or modification of the Howell Board Recommendation,
and (ii) Howell agrees that its obligations pursuant to this Section 5.3 shall
not be affected by the commencement, public proposal, public disclosure or
communication to Howell of any Superior Proposal (as defined in Section 5.3(d)).

     (b) Preparation of the Proxy Statement.  Howell shall, as soon as
reasonably practicable, prepare the proxy statement to be filed with the
Commission in connection with the Howell Stockholders Meeting (the "Proxy
Statement") and shall file the preliminary Proxy Statement with the Commission
as promptly as practical, but in no event later than 15 days after the date of
this Agreement. Howell shall cooperate with Anadarko in the preparation and
filing of the Proxy Statement with the Commission. Howell shall use its best
efforts to get clearance for the Proxy Statement by the Commission as soon as is
practicable. Consistent with the timing for the Howell Stockholders Meeting, as
determined in consultation with Anadarko, Howell shall use its best efforts to
mail at the earliest practicable date to the holders of Howell Common Stock the
Proxy Statement, which Proxy Statement shall include all information required
under Applicable Laws to be furnished to the holders of Howell Common Stock in
connection with the Merger and the transactions contemplated by this Agreement,
and shall include the Howell Board Recommendation to the extent not previously
withdrawn in compliance with Section 5.3(d) and the full text of the written
opinion of BMO Nesbitt Burns described in Section 4.24. Prior to filing or
mailing the Proxy Statement (or any amendment or supplement thereto) or
responding to any comments of the Commission with respect thereto, Howell (i)
shall provide Anadarko reasonable opportunity to review and comment on such
document or response and (ii) shall accept all reasonable comments proposed by
Anadarko.

     (c) Conduct of Howell's Operations.  During the term of this Agreement,
Howell shall conduct its operations in the ordinary course, except as expressly
contemplated by this Agreement, and shall use all reasonable efforts to maintain
and preserve its business organization and its material rights and franchises
and to retain the services of its officers and key employees and maintain
relationships with customers, suppliers, lessees, joint venture partners,
licensees and other third parties, and to maintain all of its operating assets
in their current condition, normal wear and tear excepted under the
circumstances of their use to the end that their goodwill and ongoing business
shall not be impaired in any material respect. Without limiting the generality
of the foregoing, during the term of this Agreement, Howell shall not, except as
otherwise expressly contemplated by this Agreement or as set forth in Section
5.3(c) to the Howell Disclosure Schedule, without the prior written consent of
Anadarko:

          (i)  do or effect any of the following actions with respect to its
     securities or the securities of its subsidiaries: (A) adjust, split,
     combine or reclassify Howell capital stock or that of its subsidiaries, (B)
     make, declare or pay any dividend or distribution on, or, directly or
     indirectly, redeem, purchase or otherwise acquire, any shares of Howell
     capital stock or that of its subsidiaries or any securities or obligations
     convertible into or exchangeable for any shares of Howell capital stock or
     that of its subsidiaries, except for the regular quarterly common stock
     dividend of $0.04 per share in cash on the outstanding shares of Howell
     Common Stock or the regular quarterly dividend of $0.875 per share in cash
     on the outstanding shares of Howell Convertible Preferred Stock in
     accordance with the customary record and payment dates specified in the
     Howell Certificate of Designations, provided that the regular quarterly
     dividend of $0.875 per share in cash on the outstanding shares of Howell
     Convertible Preferred Stock which would be paid on December 31, 2002 shall
     not be declared prior to December 1, 2002, shall not have a record date
     prior to December 11, 2002 and shall not be paid if the Merger is
     consummated on or prior to December 10, 2002, and utilized by Howell in the
     ordinary course of business consistent with past practice, (C) grant any
     person any right or option to acquire any shares of Howell capital stock or
     that of its subsidiaries, (D) issue, deliver or sell or agree to issue,
     deliver or sell any additional shares of Howell capital stock or any
     securities or obligations convertible into or exchangeable or exercisable
     for any shares of Howell capital stock or such securities (except pursuant
     to the exercise in accordance with their terms of Howell Options that are
     outstanding as of the date of this Agreement or upon conversion of the
     Howell Convertible Preferred Stock) or the capital stock or such securities
     or obligations of its

                                       A-23
<PAGE>

     subsidiaries, or (E) enter into any agreement, understanding or arrangement
     with respect to the sale, voting, registration or repurchase of Howell
     capital stock or that of its subsidiaries;

          (ii) directly or indirectly, sell, transfer, lease, pledge, mortgage,
     encumber, farmout or otherwise dispose of any of Howell's property or
     assets other than dispositions of oil and gas production in the ordinary
     course of business, consistent with past practice, under contracts of sale
     which may be terminated by Howell or its subsidiaries without penalty or
     premium upon 60 days prior written notice;

          (iii) make or propose any changes in, or amendments to, the Howell
     Certificate or the Howell By-laws;

          (iv) adopt a plan of complete or partial liquidation, dissolution,
     merger, consolidation, restructuring, recapitalization or other
     reorganization or alter through merger, liquidation, reorganization,
     restructuring or in any other fashion the corporate structure of Howell or
     any of its subsidiaries;

          (v) acquire a material amount of assets or capital stock of any other
     person;

          (vi) incur, create, assume or otherwise become liable for any
     indebtedness for borrowed money (other than draws under Howell's existing
     credit facilities in the ordinary course of business consistent with past
     practice) or issue or sell any debt securities or options, warrants or
     calls or other rights to acquire any debt securities of Howell or any of
     its subsidiaries, or assume, guarantee, endorse or otherwise as an
     accommodation become responsible or liable for the obligations of any other
     individual, corporation or other entity or enter into any "keep well" or
     other agreement to maintain any financial condition of any other
     individual, corporation or other entity or enter into any arrangement
     having the economic effect of any of the foregoing, or make any loans,
     advances or capital contributions to, or investments in, any person or
     entity except for any wholly owned subsidiary of Howell;

          (vii) create any subsidiaries;

          (viii) enter into, amend or modify any employment, severance,
     termination or similar agreements or arrangements with, or grant any
     bonuses, salary increases, severance or termination pay to, any current or
     former officer, director, consultant or employee, other than increases in
     cash compensation in the ordinary course of business consistent with past
     practice with respect to non-officer employees; or otherwise increase the
     compensation or benefits provided to, or pay any amounts not otherwise due
     to, any current or former officer, director, consultant or employee, except
     as may be required by Applicable Laws; or grant, reprice, or accelerate the
     exercise or payment of any Howell Options or other equity-based awards or
     accelerate eligibility for benefits or the vesting or payment of any
     compensation or benefit under any Plan or compensation agreement or
     arrangement (notwithstanding the foregoing or any provision of the Annual
     Bonus Award Program to the contrary, (A) in no event shall the aggregate
     bonuses payable to all employees under the Annual Bonus Award Program with
     respect to the fiscal year 2002 exceed $2,800,000, and (B) such bonuses
     shall be payable in calendar year 2002, it being agreed that Howell shall
     take all such actions which are necessary or appropriate to effectuate the
     obligations set forth in subclauses (A) and (B));

          (ix) enter into, adopt or amend any Plan, except as shall be required
     by Applicable Laws; take any action to fund, or in any other way secure the
     payment of compensation or benefits under any Plan or compensation
     agreement or arrangement; or change any actuarial or other assumption used
     to calculate funding obligations with respect to any pension plan or change
     the timing or manner in which contributions to any pension plan are made or
     the basis on which such contributions are determined;

          (x) take any action that could give rise to severance benefits payable
     to any officer, director, or employee of Howell as a result of consummation
     of any of the transactions contemplated by this Agreement;

          (xi) change any method or principle of Tax or financial accounting in
     a manner that is inconsistent with past practice, except to the extent
     required by GAAP as advised by Howell's regular independent accountants
     following delivery of prior written notice to Anadarko;

                                       A-24
<PAGE>

          (xii) make any material changes or modifications to any method of
     doing business;

          (xiii) settle any Actions, whether now pending or hereafter made or
     brought involving, individually or in the aggregate, an amount in excess of
     $100,000;

          (xiv) modify, amend or terminate, or waive, release or assign any
     material rights or claims with respect to, any Contract set forth in
     Section 4.16 to the Howell Disclosure Schedule, any other material Contract
     to which Howell or any of its subsidiaries is a party or any
     confidentiality, standstill or similar agreement to which Howell or any of
     its subsidiaries is a party;

          (xv) enter into, fail to enforce or consent to any matter with respect
     to which its consent is required under, any confidentiality, standstill or
     similar agreements or arrangements (other than as permitted by Section
     5.3(d));

          (xvi) write up, write down or write off the book value of any assets,
     individually or in the aggregate, in excess of $250,000, except for
     depreciation and amortization in accordance with GAAP consistently applied
     following delivery of prior written notice to Anadarko;

          (xvii) incur or commit to any capital expenditures in excess of
     $100,000 individually or $1,000,000 in the aggregate;

          (xviii) make any payments in respect of policies of directors' and
     officers' liability insurance (premiums or otherwise), other than premiums
     paid in respect of its current policies in the ordinary course of business
     consistent with past practice;

          (xix) take any action to exempt or make not subject to or to otherwise
     waive or cause to be inapplicable (A) the provisions of Section 203 of the
     DGCL, or (B) any other state takeover law or state law that purports to
     limit or restrict business combinations or the ability to acquire or vote
     shares, any individual or entity (other than Anadarko or its subsidiaries),
     or any action taken thereby, which individual, entity or action would have
     otherwise been subject to the restrictive provisions thereof and not exempt
     therefrom;

          (xx) take any action that could reasonably be expected to result in
     any representation or warranty of Howell set forth in Article IV becoming
     not true or not accurate in any respect or in any condition to the Merger
     set forth in Article VI not being satisfied;

          (xxi) enter into or carry out any other transaction other than in the
     ordinary and usual course of business;

          (xxii) make, revoke or amend any Tax election, settle or compromise
     any claim or assessment with respect to Taxes, execute or consent to any
     waivers extending the statutory period of limitations with respect to the
     collection or assessment of any Taxes or amend any material Tax Returns;

          (xxiii) enter into any agreement which contains an area of mutual
     interest provision covering in excess of 320 acres;

          (xxiv) enter into any agreement which contains a non-compete
     provision;

          (xxv) permit or cause any of its subsidiaries to do any of the
     foregoing or agree or commit to do any of the foregoing; or

          (xxvi) agree in writing or otherwise to take any of the foregoing
     actions.

     (d) No Solicitation.  Howell agrees that, during the term of this
Agreement, it shall not, and shall not authorize or permit any of its
subsidiaries or any of its or its subsidiaries' directors, officers, employees,
agents or representatives, directly or indirectly, to solicit, initiate,
encourage or facilitate, or furnish or disclose nonpublic information in
furtherance of, any inquiries or the making of any proposal with respect to any
recapitalization, merger, consolidation or other business combination involving
Howell, or acquisition of any capital stock (other than upon exercise of Howell
Options that are outstanding as of the date of this Agreement or conversion of
the Howell Convertible Preferred Stock) or a material amount of the assets of

                                       A-25
<PAGE>

Howell and its subsidiaries, taken as a whole, in a single transaction or a
series of related transactions, or any acquisition by Howell of any material
assets or capital stock of any other person, or any combination of the foregoing
(a "Competing Transaction"), or negotiate, explore or otherwise engage in
discussions with any person (other than Anadarko, Subcorp or their respective
directors, officers, employees, agents and representatives) with respect to any
Competing Transaction or enter into any agreement, arrangement or understanding
requiring it to abandon, terminate or fail to consummate the Merger or any other
transactions contemplated by this Agreement; provided that, at any time prior to
the approval of the Merger by the holders of Howell Common Stock, Howell may
furnish information to, and negotiate or otherwise engage in discussions with,
any person that delivers a written proposal for a Competing Transaction that was
not solicited or encouraged after the date of this Agreement if and so long as
the Board of Directors of Howell determines in good faith by a majority vote,
after receiving the advice of its outside legal counsel, that failing to take
such action would constitute a breach of its fiduciary duties under Applicable
Laws and determines that such a proposal is, after consulting with BMO Nesbitt
Burns (or any other reputable investment banking firm), more favorable to Howell
Stockholders than the transactions contemplated by this Agreement (after taking
into consideration any adjustment to the terms and conditions proposed by
Anadarko in response to such Competing Transaction) (a "Superior Proposal");
provided, further, that, prior to furnishing any information to such person,
Howell shall enter into a confidentiality agreement that is no less restrictive
than the confidentiality agreement between Anadarko and Howell, dated May 13,
2002 (the "Confidentiality Agreement"). Howell will immediately cease all
existing activities, discussions and negotiations with any persons conducted on
or prior to the date of this Agreement with respect to any proposal for a
Competing Transaction and request the return or destruction of all confidential
information regarding Howell provided to any such persons on or prior to the
date of this Agreement pursuant to the terms of any confidentiality agreements
or otherwise. In the event that, prior to the approval of the Merger by the
holders of Howell Common Stock, the Board of Directors of Howell receives a
Superior Proposal that was not solicited or encouraged after the date of this
Agreement and the Board of Directors of Howell is advised by outside legal
counsel that failure to do so would constitute a breach of the fiduciary duties
of the Board of Directors of Howell under Applicable Laws, the Board of
Directors of Howell may (subject to this and the following sentences) withdraw,
modify or change, in a manner adverse to Anadarko, the Howell Board
Recommendation and/or comply with Rule 14e-2 under the Exchange Act with respect
to a Competing Transaction, provided that Howell gives Anadarko five business
days' prior written notice of its intention to do so (provided that the
foregoing shall in no way limit or otherwise affect Anadarko's right to
terminate this Agreement pursuant to Section 7.1(d)). Any such withdrawal,
modification or change of the Howell Board Recommendation shall not change the
approval of the Board of Directors of Howell for purposes of causing any state
takeover statute or other state law to be inapplicable to the transactions
contemplated by this Agreement, including the Merger or the Support Agreements,
or change the obligation of Howell to present this Agreement for adoption at the
duly called Howell Stockholders Meeting on the earliest practicable date
determined in consultation with Howell. From and after the execution of this
Agreement, Howell shall as promptly as practicable advise Anadarko in writing of
the receipt, directly or indirectly, of any inquiries, discussions,
negotiations, or proposals relating to a Competing Transaction (including the
specific terms thereof and the identity of the other person or persons involved)
and promptly furnish to Anadarko a copy of any such written proposal in addition
to any information provided to or by any third party relating thereto. In
addition, Howell shall as promptly as practicable advise Anadarko, in writing,
if the Board of Directors of Howell shall make any determination as to any
Competing Transaction as contemplated by the proviso to the first sentence of
this Section 5.3(d).

     (e) Howell Convertible Preferred Stock.  Howell shall, in accordance with
securities laws and the DGCL, provide to the holders of Howell Convertible
Preferred Stock the notice required under Section 3(h) of the Howell Certificate
of Designations.

     (f) Access.  Howell shall permit representatives of Anadarko to have access
at all reasonable times to Howell's premises, properties, assets, books,
records, Tax Returns, contracts, documents, commitments, directors, officers,
employees, attorneys, accountants, auditors, other advisors and other
representatives, shall use reasonable efforts to make available to Anadarko
Howell's customers, suppliers and co-venturers, and shall make available to
Anadarko on a prompt basis all information concerning its business, properties
and personnel as Anadarko may reasonably request (including the work papers of
Deloitte & Touche LLP if

                                       A-26
<PAGE>

reasonably available). Anadarko will keep the information obtained pursuant to
this Section 5.3(f) confidential pursuant to the terms of the Confidentiality
Agreement, except as may otherwise be required by Applicable Laws. No
investigation conducted pursuant to this Section 5.3(f) shall affect or be
deemed to modify any representation or warranty made in this Agreement.

     (g) Advice of Changes; Subsequent Financial Statements.  Howell shall (i)
confer with Anadarko on a regular and frequent basis to report on operational
matters and other matters reasonably requested by Anadarko and (ii) promptly
advise Anadarko orally and in writing of any state of facts, change,
development, effect, condition, result, consequence, occurrence or circumstance
that, individually or in the aggregate, has had or could reasonably be expected
to have a Material Adverse Effect on Howell or a material adverse effect on the
ability of Howell to consummate the transactions contemplated by this Agreement
or to cause a condition to the Merger set forth in Article VI not to be
satisfied; provided, however, that no such advice shall affect the
representations, warranties, covenants or agreements of the parties or the
conditions to the obligations of the parties under this Agreement. Howell shall
consult with Anadarko prior to making publicly available its financial results
after the date of this Agreement and a reasonable time prior to filing any
Howell SEC Documents after the date of this Agreement.

                                   ARTICLE VI

                            CONDITIONS TO THE MERGER

     6.1.  Conditions to the Obligations of Each Party.  The obligations of
Howell, Anadarko and Subcorp to consummate the Merger shall be subject to the
satisfaction (or, to the extent legally permissible, waiver) of the following
conditions:

          (a) This Agreement, the Merger and the transactions contemplated by
     this Agreement shall have been approved and adopted by the holders of
     Howell Common Stock.

          (b) Any waiting periods under the HSR Act relating to the Merger and
     the transactions contemplated by this Agreement, if applicable, shall have
     expired or been terminated, and any other approvals of any Governmental
     Authority relating to the Merger and the transactions contemplated by this
     Agreement shall have been obtained.

          (c) No provision of Applicable Laws and no temporary restraining
     order, preliminary or permanent injunction or other order or decree issued
     by any court of competent jurisdiction that has the effect of preventing
     the consummation of the Merger or the transactions contemplated by this
     Agreement shall be in effect.

     6.2.  Conditions to the Obligations of Anadarko and Subcorp.

     (a) Each of the representations and warranties of Howell set forth in
Article IV (other than the representations and warranties of Howell set forth in
Section 4.4) shall be true and correct in all respects (but without regard to
any materiality qualifications or references to Material Adverse Effect
contained in any specific representation or warranty) (i) on the date of this
Agreement and (ii) on and as of the Closing Date as though made on and as of the
Closing Date (except for representations and warranties made as of a specified
date, the accuracy of which will be determined as of the specified date),
except, in the cases of clauses (i) and (ii), where any such failure of the
representations and warranties in the aggregate to be true and correct in all
respects could not reasonably be expected to have a Material Adverse Effect on
Howell. The representations and warranties of Howell set forth in Section 4.4
shall be true and correct on the date of this Agreement and on and as of the
Closing Date as though made on and as of the Closing Date (except for
representations and warranties made as of a specified date, the accuracy of
which will be determined as of the specified date).

     (b) There shall not be pending any Action instituted by any Governmental
Authority or other reputable person or entity (i) challenging or seeking to
restrain or prohibit the consummation of the Merger or any of the other
transactions contemplated by this Agreement, (ii) seeking to prohibit or limit
the ownership or operation by Anadarko, Howell or any of their respective
subsidiaries of, or to compel Anadarko, Howell or

                                       A-27
<PAGE>

any of their respective subsidiaries to dispose of or hold separate, any
material portion of the businesses or assets of Anadarko, Howell or any of their
respective subsidiaries, as a result of the Merger or any of the other
transactions contemplated by this Agreement, (iii) seeking to impose limitations
on the ability of Anadarko to acquire or hold, or exercise full rights of
ownership of, any shares of the Surviving Corporation capital stock, including
the right to vote the Surviving Corporation capital stock on all matters
properly presented to the stockholders of the Surviving Corporation or (iv)
seeking to prohibit Anadarko or any of its subsidiaries from effectively
controlling in any material respect the businesses or operations of Anadarko or
the Surviving Corporation or any of their respective subsidiaries.

     (c) No provision of Applicable Laws and no judgment, injunction, order or
decree shall limit the ownership or operation by Anadarko, Howell or any of
their respective subsidiaries of any material portion of the businesses or
assets of Anadarko or Howell.

     (d) Howell shall have performed in all material respects each obligation
and agreement and shall have complied in all material respects with each
covenant to be performed and complied with by it under this Agreement at or
prior to the Effective Time.

     (e) Howell shall have furnished Anadarko with a certificate dated the
Closing Date signed on its behalf by its Chairman, President or any Vice
President to the effect that the conditions set forth in Sections 6.2(a) and
6.2(d) have been satisfied.

     (f) Since the date of this Agreement, except to the extent provided by
Section 4.11 to the Howell Disclosure Schedule, there has not been any state of
facts, change, development, effect, condition, result, consequence, occurrence
or circumstance that, individually or in the aggregate, has had or could
reasonably be expected to have a Material Adverse Effect on Howell or a material
adverse effect on the ability of Howell to consummate the transactions
contemplated by this Agreement.

     6.3.  Conditions to the Obligations of Howell.

     (a) Each of the representations and warranties of each of Anadarko and
Subcorp set forth in Article III shall be true and correct in all respects (but
without regard to any materiality qualifications or references to Material
Adverse Effect contained in any specific representation or warranty) (i) on the
date of this Agreement and (ii) on and as of the Closing Date as though made on
and as of the Closing Date (except for representations and warranties made as of
a specified date, the accuracy of which will be determined as of the specified
date), except, in the cases of clauses (i) and (ii), where any such failure of
the representations and warranties in the aggregate to be true and correct in
all respects would not prevent Anadarko and Subcorp from consummating the
Merger.

     (b) Anadarko shall have performed in all material respects each obligation
and agreement and shall have complied in all material respects with each
covenant to be performed and complied with by it under this Agreement at or
prior to the Effective Time.

     (c)  Anadarko shall have furnished Howell with a certificate dated the
Closing Date signed on its behalf by its Chairman, President or any Vice
President to the effect that the conditions set forth in Sections 6.3(a) and
6.3(b) have been satisfied.

                                  ARTICLE VII
                           TERMINATION AND AMENDMENT

     7.1.  Termination.  This Agreement may be terminated and the Merger may be
abandoned at any time prior to the Effective Time (notwithstanding any approval
of this Agreement by the holders of Howell Common Stock):

          (a) by mutual written consent of Anadarko and Howell;

          (b) by either Anadarko or Howell if there shall be any law or
     regulation that makes consummation of the Merger illegal or otherwise
     prohibited, or if there shall be entered any judgment, injunction, order or
     decree of a court or other competent Governmental Authority enjoining
     Anadarko or Howell from

                                       A-28
<PAGE>

     consummating the Merger and such judgment, injunction, order or decree
     shall have become final and nonappealable;

          (c) by either Anadarko or Howell if the Merger shall not have been
     consummated by February 28, 2003, provided that termination pursuant to
     this Section 7.1(c) shall not be permitted prior to the 60th day following
     the date the Proxy Statement is cleared by the Commission unless such
     clearance is not obtained by May 31, 2003; provided further, however, that
     the right to terminate this Agreement under this Section 7.1(c) shall not
     be available to any party to this Agreement whose failure or whose
     affiliate's failure to perform any covenant or obligation under this
     Agreement has been the cause of or resulted in the failure of the Merger to
     occur on or before such date;

          (d) by Anadarko if the Board of Directors of Howell shall withdraw,
     modify or change the Howell Board Recommendation in a manner adverse to
     Anadarko, if the Board of Directors of Howell approves or recommends any
     Competing Transaction, or if the Board of Directors of Howell shall have
     refused to affirm the Howell Board Recommendation within five business days
     of any written request from Anadarko;

          (e) by Anadarko or Howell if, at the Howell Stockholders Meeting
     (including any adjournment or postponement thereof), the requisite vote of
     the holders of Howell Common Stock to adopt this Agreement and to approve
     the Merger and the transactions contemplated by this Agreement shall not
     have been obtained; or

          (f) by Anadarko or Howell if there shall have been a material breach
     by the other of any of its representations, warranties, covenants or
     agreements contained in this Agreement which would result in the conditions
     to the Merger set forth in Article VI not being satisfied, and such breach
     shall not have been cured within 30 days after notice thereof shall have
     been received by the party to this Agreement claimed to be in breach.

     7.2.  Effect of Termination.  In the event of the termination of this
Agreement pursuant to Section 7.1, this Agreement, except for the provisions of
the second sentence of Section 5.3(f) and the provisions of this Section 7.2 and
Section 8.11, shall become void and have no effect, without any liability on the
part of any party to this Agreement or its directors, officers, or stockholders,
as the case may be. Notwithstanding the foregoing, nothing in this Section 7.2
shall relieve any party to this Agreement of liability for a material breach of
any provision of this Agreement and provided, further, however, that, if it
shall be judicially determined that termination of this Agreement was caused by
an intentional breach of this Agreement, then, in addition to other remedies at
law or equity for breach of this Agreement, the party to this Agreement so found
to have intentionally breached this Agreement shall indemnify and hold harmless
the other parties to this Agreement for their respective out-of-pocket costs,
fees and expenses of their counsel, accountants, financial advisors and other
experts and advisors as well as fees and expenses incident to negotiation,
preparation and execution of this Agreement and related documentation and
stockholders' meeting and consents (collectively, "Costs"). If this Agreement is
terminated pursuant to Sections 7.1(c) (following the public announcement or
disclosure of a Competing Transaction), 7.1(d) or 7.1(e), then Howell will, in
the case of a termination by Anadarko, within two business days following any
such termination or, in the case of a termination by Howell, concurrently with
such termination, pay to Anadarko in cash by wire transfer in immediately
available funds to an account designated by Anadarko (a) in reimbursement for
Anadarko's Costs an amount in cash equal to the aggregate amount of Anadarko's
Costs incurred in connection with pursuing the transactions contemplated by this
Agreement, including legal, accounting and investment banking fees, up to but
not in excess of an amount equal to $1,000,000 in the aggregate and (b) a
termination fee in an amount equal to $9,000,000.

     7.3.  Amendment.  This Agreement may be amended by the parties to this
Agreement, by action taken or authorized by their respective Boards of
Directors, at any time before or after approval of this Agreement by the holders
of Howell Common Stock, but, after any such approval, no amendment shall be made
that by law requires further approval or authorization by Howell Stockholders
entitled to vote thereon without such further approval or authorization.
Notwithstanding the foregoing, this Agreement may not be amended, except by an
instrument in writing signed on behalf of all of the parties to this Agreement.

                                       A-29
<PAGE>

     7.4.  Extension; Waiver.  At any time prior to the Effective Time, Anadarko
(with respect to Howell) and Howell (with respect to Anadarko and Subcorp) by
action taken or authorized by their respective Boards of Directors, may, to the
extent legally allowed, (a) extend the time for the performance of any of the
obligations or other acts of such party to this Agreement, (b) waive any
inaccuracies in the representations and warranties contained in this Agreement
or in any document delivered pursuant to this Agreement and (c) waive compliance
with any of the agreements or conditions contained in this Agreement. Any
agreement on the part of a party to this Agreement to any such extension or
waiver shall be valid only if set forth in a written instrument signed on behalf
of such party to this Agreement.

                                  ARTICLE VIII

                                 MISCELLANEOUS

     8.1.  Survival of Representations and Warranties.  The representations and
warranties made in this Agreement by the parties to this Agreement shall not
survive the Effective Time. This Section 8.1 shall not limit any covenant or
agreement of the parties to this Agreement, which by its terms contemplates
performance after the Effective Time or after the termination of this Agreement.

     8.2.  Notices.  All notices and other communications under this Agreement
shall be in writing and shall be deemed given if delivered personally,
telecopied (which is confirmed) or dispatched by a nationally recognized
overnight courier service to the parties to this Agreement at the following
addresses (or at such other address for a party to this Agreement as shall be
specified by like notice):

     (a) if to Anadarko or Subcorp:

       Anadarko Petroleum Corporation
       1201 Lake Robbins Drive
       The Woodlands, Texas 77380
       Attention: General Counsel
       Telecopy No.: (832) 636-8232

         with a copy to

       Daniel A. Neff, Esq.
       David A. Katz, Esq.
       Wachtell, Lipton, Rosen & Katz
       51 West 52nd Street
       New York, New York 10019
       Telecopy No.: (212) 403-2000

     (b) if to Howell:

        Howell Corporation
        1111 Fannin, Suite 1500
        Houston, Texas 77002
        Attention: General Counsel
        Telecopy No.: (713) 658-4007

        with a copy to

        John R. Brantley, Esq.
        Bracewell & Patterson L.L.P.
        711 Louisiana, Suite 2900
        Houston, Texas 77002
        Telecopy No.: (713) 221-1212

     8.3.  Interpretation.  When a reference is made in this Agreement to an
Article or Section, such reference shall be to an Article or Section of this
Agreement unless otherwise indicated. The headings, the

                                       A-30
<PAGE>

table of contents and the index of defined terms contained in this Agreement are
for reference purposes only and shall not affect in any way the meaning or
interpretation of this Agreement. Whenever the words "include", "includes", or
"including" are used in this Agreement, they shall be deemed to be followed by
the words "without limitation". "Knowledge" means, when used with respect to
Howell in this Agreement, the actual knowledge of the persons set forth in
Section 8.3 to the Howell Disclosure Schedule. "Material Adverse Effect" shall
mean any state of facts, change, development, effect, condition, result,
consequence, occurrence or circumstance that has been or could reasonably be
expected to be materially adverse to the business, assets, liabilities,
properties, profitability, financial condition or results of operations of
Howell and its subsidiaries or Anadarko and its subsidiaries, as applicable, in
each case taken as a whole, except such state of facts, change, development,
effect, condition, result, consequence, occurrence or circumstance which is
attributable to changes in oil and/or gas prices. A "subsidiary" means, when
used with respect to any party to this Agreement, any corporation or other
organization, incorporated or unincorporated, (a) of which such party to this
Agreement or any of its subsidiaries is a general partner (excluding
partnerships, the general partnership interests of which held by such party to
this Agreement or any of its subsidiaries do not have 50% or more of the voting
interests in such partnership) or (b) 50% or more of the securities or other
interests of which having by their terms ordinary voting power to elect at least
50% of the board of directors or others performing similar functions with
respect to such corporation or other organization is, directly or indirectly,
owned or controlled by such party to this Agreement or one or more of its
subsidiaries (or, if there are no such voting securities or interests, 50% or
more of the equity interests of which is, directly or indirectly, owned or
controlled by such party to this Agreement or one or more of its subsidiaries).

     8.4.  Counterparts.  This Agreement may be executed in counterparts, which
together shall constitute one and the same Agreement. The parties to this
Agreement may execute more than one copy of this Agreement, each of which shall
constitute an original.

     8.5.  Entire Agreement.  This Agreement (including the documents and the
instruments relating to the Merger referred to in this Agreement), the Support
Agreements, the Confidentiality Agreement and the Letter Agreement dated July 9,
2002 constitute the entire agreement among the parties to this Agreement and
supersede all prior agreements and understandings, agreements or representations
by or among the parties to this Agreement, written and oral, with respect to the
subject matter of this Agreement and thereof.

     8.6.  Third-Party Beneficiaries.  Except for the agreement set forth in
Section 5.2(b), nothing in this Agreement, express or implied, is intended or
shall be construed to create any third-party beneficiaries.

     8.7.  Governing Law.  Except to the extent that the laws of the
jurisdiction of organization of any party to this Agreement, or any other
jurisdiction, are mandatorily applicable to the Merger or to matters arising
under or in connection with this Agreement, this Agreement shall be governed by
the laws of the State of Delaware without regard to the principles of conflicts
of laws thereof. All actions and proceedings arising out of or relating to this
Agreement shall be heard and determined in any state or federal court sitting in
the State of Delaware.

     8.8.  Consent to Jurisdiction; Venue.

     (a) Each of the parties to this Agreement irrevocably submits to the
exclusive jurisdiction of the state courts of Delaware and to the jurisdiction
of the United States District Court for the District of Delaware, for the
purpose of any action or proceeding arising out of or relating to this Agreement
and each of the parties to this Agreement irrevocably agrees that all claims in
respect to such action or proceeding may be heard and determined exclusively in
any Delaware state or federal court sitting in the State of Delaware. Each of
the parties to this Agreement agrees that a final judgment in any action or
proceeding shall be conclusive and may be enforced in other jurisdictions by
suit on the judgment or in any other manner provided by law.

     (b) Each of the parties to this Agreement irrevocably consents to the
service of any summons and complaint and any other process in any other action
or proceeding relating to the Merger, on behalf of itself or its property, by
the personal delivery of copies of such process to such party to this Agreement.
Nothing in this Section 8.8 shall affect the right of any party to this
Agreement to serve legal process in any other manner permitted by law.

                                       A-31
<PAGE>

     8.9.  Specific Performance.  The transactions contemplated by this
Agreement are unique. Accordingly, each of the parties to this Agreement
acknowledges and agrees that, in addition to all other remedies to which it may
be entitled, each of the parties to this Agreement is entitled to a decree of
specific performance, provided that such party to this Agreement is not in
material default under this Agreement.

     8.10.  Assignment.  Neither this Agreement nor any of the rights, interests
or obligations under this Agreement shall be assigned by any of the parties to
this Agreement (whether by operation of law or otherwise) without the prior
written consent of the other parties to this Agreement, except that Anadarko
may, without Howell's consent, substitute another of its wholly owned
subsidiaries for Subcorp under this Agreement. Subject to the preceding
sentence, this Agreement shall be binding upon, inure to the benefit of and be
enforceable by the parties to this Agreement and their respective successors and
assigns.

     8.11.  Expenses.  Subject to the provisions of Section 7.2, all costs and
expenses incurred in connection with this Agreement and the transactions
contemplated by this Agreement and thereby shall be paid by the party to this
Agreement incurring such expenses.

     IN WITNESS WHEREOF, Anadarko, Subcorp and Howell have signed this Agreement
as of the date first written above.

                                          ANADARKO PETROLEUM CORPORATION

                                          By:      /s/ JAMES R. LARSON
                                            ------------------------------------
                                            Name: James R. Larson
                                            Title:   Senior Vice President

                                          BELAIR MERGER CORP.

                                          By:      /s/ JAMES R. LARSON
                                            ------------------------------------
                                            Name: James R. Larson
                                            Title:   Vice President

                                          HOWELL CORPORATION

                                          By:     /s/ RICHARD K. HEBERT
                                            ------------------------------------
                                            Name: Richard K. Hebert
                                            Title:   President & Chief Executive
                                                     Officer

                                       A-32