Document:

<PAGE>

                                                                    EXHIBIT 10.1

                                 March 31, 2001

Lloyd K. Everson, M.D.
US Oncology, Inc.
16825 Northchase Drive, Suite 1300
Houston, Texas  77060

            Re: Termination of Employment Agreement

Dear Dr. Everson:

     In connection with the termination of your current employment agreement and
the entering into of a new employment agreement between you and US Oncology,
Inc., you and US Oncology hereby agree as follows:

     1.  Termination.  The employment agreement dated January 1, 2000, by and
between US Oncology, Inc. and Lloyd K. Everson, M.D. ("Old Employment
Agreement") is hereby terminated, effective upon Dr. Everson's execution of this
letter, and neither party shall have any further rights or obligations with
respect to or arising out of such employment agreement except as provided in
this letter.  Notwithstanding Section 4(c) of the Old Employment Agreement, only
Sections 8, 9, 10, and 11 thereof, and the rights and obligations created
therein, shall survive except as provided in this letter.

     2.  Resignation.  Dr. Everson hereby resigns from all officer positions he
holds with US Oncology, Inc.  In addition, Dr. Everson hereby resigns from all
officer and director positions he holds with each of US Oncology, Inc.'s direct
and indirect subsidiaries.

     3.  Termination and Severance Benefits.  Section 4(b) of the Old Employment
Agreement, and the rights and obligations created therein, shall survive the
termination of the Old Employment Agreement and the benefits set forth therein
shall be provided to Dr. Everson as if the Old Employment Agreement shall have
been terminated by the Company without cause pursuant to Section 4(a)(iv)
thereof.  The "Base Salary" as defined in Section 4(b) shall be the base salary
of Dr. Everson as in effect on the date hereof.

     4.  New Employment Agreement.  Dr. Everson will enter into a new employment
agreement with US Oncology, Inc. substantially in the form attached hereto.  The
new
<PAGE>

Lloyd K. Everson, M.D.
March 31, 2001
Page 2

employment agreement will be effective simultaneously with the termination
of the Old Employment Agreement.

     Please indicate your acknowledgement and acceptance of the terms of this
letter by executing where indicated below.

                              US ONCOLOGY, INC.

                              By:
                                  -------------------------------

                              Name: -----------------------------

                              Title:
                                     ----------------------------

Accepted and agreed to on this 31st day of March, 2001.

-------------------------------------
Lloyd K. Everson, M.D.<PAGE>

                                                                     Exhibit 4.1

                                    AROC INC.                          [LOGO]

                               OFFER TO PURCHASE
                    ANY AND ALL SHARES OF OUR COMMON STOCK
                                   FOR CASH
                  AT A PURCHASE PRICE OF $0.06 NET PER SHARE

--------------------------------------------------------------------------------
THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME ON
JUNE 12, 2001, UNLESS THE OFFER IS EXTENDED.
--------------------------------------------------------------------------------

     We, AROC Inc., a Delaware corporation, hereby offer to purchase any and all
of our shares of common stock $0.001 par value per share, for a purchase price
of $0.06 per share net to the seller in cash, without interest thereon, upon the
terms and subject to the conditions set forth in this Offer to Purchase and in
the related Letter of Transmittal, which, together with any amendments or
supplements are referred to in this Offer to Purchase as the "Offer."  The Offer
is not conditioned upon any minimum number of shares being tendered, however, it
is subject to certain other conditions.  See "The Tender Offer--Certain
Conditions of the Offer."

     A SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF AROC, CONSISTING OF THE
INDEPENDENT MEMBER OF THE BOARD OF DIRECTORS, HAS DETERMINED THAT THE OFFER IS
FAIR TO, AND IN THE BEST INTERESTS OF, AROC AND ITS UNAFFILIATED STOCKHOLDERS,
AND RECOMMENDS THAT AROC's UNAFFILIATED STOCKHOLDERS TENDER THEIR SHARES OF AROC
COMMON STOCK PURSUANT TO THE OFFER.

     Neither AROC nor its board of directors makes any recommendation to any
stockholder as to whether to tender or refrain from tendering their shares.
AROC has been advised by MPAC Energy, LLC, our majority shareholder, that it
does not intend to tender any shares pursuant to the Offer.  MPAC owns 30.8% of
our outstanding shares of common stock and 100% of our outstanding shares of
convertible preferred stock.  On a fully diluted basis, MPAC owns 95.6% of our
outstanding shares of common stock.

     Quotations for AROC's common stock are posted on the Pink Sheets Electronic
Quotation Service.  On April 18, 2001, the last trading day of the shares of
AROC's common stock before AROC filed its Annual Report on Form 10-K for the
Year Ended December 31, 2000, which disclosed the approval of this Offer, the
closing market bid quotation on Pink Sheets was $0.01 per share.  The sales
price per share for AROC's common stock, as reported on May 2, 2001, was $0.025.
On March 1, 2001, there were 55,278,837 shares of AROC's common stock
outstanding.  As of March 22, 2001, there were 4,866 stockholders of record for
AROC's common stock.

     If you desire to tender all or any portion of your shares of AROC common
stock, you should either (1) complete and sign the Letter of Transmittal in
accordance with its instructions, mail or deliver the Letter of Transmittal and
any other required documents to the Depositary, along with the certificate(s)
evidencing the tendered shares, or (2) request your broker, dealer, commercial
bank, trust company or other nominee to effect the transaction for the
stockholder.  If your shares are registered in the name of a broker, dealer,
commercial bank, trust company or other nominee, often referred to as held in
"street name," you must contact your broker, dealer, commercial bank, trust
company or other nominee if you desire to tender your shares.  Any stockholder
who desires to tender shares and whose certificates evidencing such shares are
not immediately available may tender such shares by following the procedure for
guaranteed delivery.  See "The Tender Offer--Procedures for Accepting the Offer
and Tendering Shares."

     THIS TRANSACTION HAS NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION, NOR HAS THE SEC OR ANY
STATE SECURITIES COMMISSION PASSED UPON THE MERITS OR FAIRNESS OF THE
TRANSACTION OR THE ADEQUACY OR ACCURACY OF THE INFORMATION CONTAINED IN THIS
DOCUMENT.  ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

                             _____________________

                                 May 14, 2001
<PAGE>

                                 TABLE OF CONTENTS

SUMMARY TERM SHEET.....................................................    1

CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS..............    4

INTRODUCTION...........................................................    5

SPECIAL FACTORS........................................................    7
     Background of the Offer; Alternatives Considered..................    7
     Reasons for and Purpose of the Offer..............................    8
     Interests of Certain Persons in the Offer.........................    8
     The Board's Approval and the Special Committee's Recommendation...    9
     Opinion of the Financial Advisor to the Special Committee.........   10
     Effects of the Offer..............................................   13
     Plans of AROC After the Offer.....................................   14
     Dissenters' or Appraisal Rights of Stockholders...................   14
     Conduct of AROC's Business After the Offer........................   14
     Material Federal Income Tax Consequences..........................   15

THE TENDER OFFER.......................................................   18
     Terms of the Offer; Expiration Date...............................   18
     Acceptance for Payment and Payment for Shares.....................   19
     Procedures for Accepting the Offer and Tendering Shares...........   20
     Withdrawal Rights.................................................   22
     Dividends and Distributions.......................................   23
     Certain Conditions of the Offer...................................   23
     Source of Funds for and Expenses of the Offer.....................   24
     Certain Legal Matters and Regulatory Approvals....................   25
     Miscellaneous.....................................................   26

THE COMPANY............................................................   27
     Background and Business...........................................   27
     Officers and Directors............................................   27
     Beneficial Ownership of Certain Stockholders......................   28
     Additional Information About AROC in Form 10-K....................   29

AVAILABLE INFORMATION..................................................   30
Appendix A:  Opinion of Financial Advisor
Appendix B:  Directors, Executive Officers or Controlling Persons of MPAC
             Energy, LLC
<PAGE>

                                 SUMMARY TERM SHEET

     We are offering to purchase all the outstanding shares of our common stock
at a purchase price of $0.06 per share net to the seller in cash.  Through a
question and answer format, this Summary Term Sheet will explain to you, the
common stockholders of AROC, the important terms of the Offer.  This explanation
will assist you in deciding whether to tender your shares of AROC common stock
to us.  This Summary Term Sheet serves only as an introduction, and we urge you
to read carefully the remainder of this Offer to Purchase and the accompanying
Letter of Transmittal in order to educate yourself fully on the details of the
Offer.  Cross-referenced text refers to sections within this Offer to Purchase,
unless otherwise noted.

Q:  WHO IS OFFERING TO BUY MY SHARES OF STOCK?

A:  We are AROC Inc., a Delaware corporation, and we are offering to buy back
    our own common stock in a self-tender offer. See "The Tender Offer--Certain
    Information Concerning AROC."

Q:  WHAT SECURITIES AND AMOUNTS OF SECURITIES ARE SOUGHT IN THE OFFER?

A:  We are making the offer to purchase all of the outstanding shares of our
    common stock. Although the Offer is being made to all holders of common
    stock, MPAC who holds approximately 30.8% of our outstanding common stock
    and 100% of our convertible preferred stock, has advised us that it does not
    intend to tender any of its shares pursuant to the Offer. See "The Tender
    Offer--Terms of the Offer; Expiration Date."

Q:  HOW MUCH IS AROC OFFERING TO PAY AND WHAT IS THE FORM OF PAYMENT?

A:  We are offering to pay $0.06 per share in cash, without interest.  See "The
    Tender Offer--Terms of the Offer; Expiration Date."

Q:  WHAT IS THE PURPOSE OF THE OFFER?

A:  The purpose of the Offer is to provide the holders of our common stock with
    liquidity for their shares at a price that the special committee of the
    board of directors has determined to be fair to our unaffiliated
    stockholders (those stockholders other than MPAC). After completion of the
    Offer, MPAC will consider a second-step transaction, such as a merger, a
    reverse stock split or similar transaction, in which all of the remaining
    public stockholders would receive cash for their shares at a price that may
    be higher, the same or lower than the purchase price in this Offer. A
    second-step transaction may or may not require approval by our remaining
    stockholders, depending on the nature of any second-step transaction.
    Because MPAC currently holds 30.8% of our outstanding common stock, 95.6% on
    a fully diluted basis, and will hold a greater percentage after the Offer,
    it will be able to control the outcome of any second-step transaction.
    However, neither AROC nor MPAC are obligated to effect, and no agreement
    currently exists relating to, any second-step transaction. See "Special
    Factors--Reason for and Purpose of the Offer."

Q:  DOES AROC HAVE THE FINANCIAL RESOURCES TO PAY FOR THE SHARES?

A:  Yes.  We have the funds available to acquire the shares in the Offer.  See
    "Special Factors--Source of Funds for and Expenses of the Offer."

Q:  IS AROC's FINANCIAL CONDITION RELEVANT TO MY DECISION ON WHETHER TO TENDER
    MY SHARES OF AROC COMMON STOCK IN THE OFFER?

A:  Because tendering your shares of AROC common stock in the Offer will end
    your ownership interest in AROC, including the chance to receive any
    possible future dividends or other payments in respect of our common stock,
    our financial condition may be relevant to your decision whether to tender
    your shares in the Offer. We have provided certain of our summary financial
    information under "Selected Financial Data," and more detailed information
    is available in our Annual Report on Form 10-K for the year ended December
    31, 2000, which accompanies this Offer to Purchase.

                                       1
<PAGE>

Q:  HOW LONG DO I HAVE TO DECIDE WHETHER TO TENDER IN THE OFFER?

A:  You have until 12:00 Midnight, New York City time, on the expiration date of
    June 12, 2001 to tender your shares. We will purchase properly tendered
    shares of AROC common stock promptly following the expiration date if the
    conditions to our Offer are then met and the shares are not properly
    withdrawn. We may extend the period during which the Offer is open for any
    reason, including, but not limited to, if the conditions to our Offer are
    not met on the expiration date. See "The Tender Offer--Terms of the Offer;
    Expiration Date."

Q:  HOW WILL I BE NOTIFIED IF THE OFFER IS EXTENDED?

A:  If the Offer is extended we will announce the new expiration date by mailing
    a notice to stockholders, making a public announcement, or filing a Form 8-K
    with the SEC. See "The Tender Offer--Terms of the Offer; Expiration Date."

Q:  WHAT ARE THE MOST SIGNIFICANT CONDITIONS OF THE OFFER?

A:  We are not obligated to purchase any shares that are validly tendered if,
    among other things:

    .   a lawsuit or similar action is threatened or instituted against us
        challenging the Offer or, in our view, resulting or having the potential
        to result in a material adverse effect on us,

    .   we believe acceptance for payment of the tendered shares would be
        illegal,

    .   any person proposes a tender or exchange offer for any of our shares, or

    .   we believe there are events that have or may have a material adverse
        effect on us.

    We reserve the right to waive any of the above conditions. Other conditions
    are set forth in "The Tender Offer--Certain Conditions of the Offer."

Q:  CAN AROC AMEND THE TERMS OF THE OFFER?

A:  We reserve the right in our sole discretion to amend the Offer in any
    respect.  See "The Tender Offer--Terms of the Offer; Expiration Date."

Q:  HOW DO I FIND OUT IF AROC AMENDS THE TERMS OF THE OFFER?

A:  We will announce any amendment to the Offer by making a public announcement,
    mailing a notice to stockholders, or filing a Form 8-K with the SEC
    describing the amendment. We will announce any extension of the Offer no
    later than 9:00 a.m., New York City time, on the next business day after the
    last previously scheduled expiration date. In the event of a termination or
    postponement of the Offer, we will also give written or oral notice to the
    Depositary. See "The Tender Offer--Terms of the Offer; Expiration Date."

Q:  HOW DO I TENDER MY SHARES OF AROC COMMON STOCK?

A:  If you hold your shares "of record," you can tender your shares by
    completing and sending the enclosed Letter of Transmittal along with any
    other documents required by the Letter of Transmittal, and your stock
    certificates to the Depositary, Registrar and Transfer Company, at the
    address listed on the enclosed Letter of Transmittal. If your shares are
    held in "street name" for you by your broker, you must direct your broker to
    tender your shares of AROC common stock. Please contact your broker. If you
    want to tender your shares but your certificates evidencing such shares are
    not immediately available, you may tender your shares by following the
    procedure for guaranteed delivery. See "The Tender Offer--Procedures for
    Accepting the Offer and Tender Shares."

                                       2
<PAGE>

Q:  UNTIL WHAT TIME CAN I WITHDRAW PREVIOUSLY TENDERED SHARES?

A:  You can withdraw tendered shares at any time prior to midnight New York City
    time on the expiration date of June 12, 2001. If the Offer is extended, you
    can withdraw tendered shares at any time prior to the new expiration date.
    See "The Tender Offer--Withdrawal Rights."

Q:  HOW DO I WITHDRAW PREVIOUSLY TENDERED SHARES?

A:  You can withdraw shares that you have already tendered by sending a timely
    notice of withdrawal to the Depositary at the address listed on the enclosed
    Letter of Transmittal. See "The Tender Offer--Withdrawal Rights."

Q:  WHAT DOES THE BOARD OF DIRECTORS AND THE SPECIAL COMMITTEE THINK OF THE
    OFFER?

A:  Although the board of directors unanimously approved the Offer, neither AROC
    nor its board of directors make any recommendation to the stockholders as to
    whether to tender or refrain from tendering their shares. Because the board
    consists of six directors, five of whom are officers, directors, or
    otherwise affiliated with AROC or MPAC, the board formed a special
    committee, consisting of the independent director on the board of directors,
    to consider the Offer and determine whether to recommend the Offer.

    The special committee concluded that the Offer is advisable and that the
    terms of the Offer are fair to, and in the best interests of, AROC and its
    unaffiliated stockholders. In coming to its conclusion, the special
    committee took into account the valuation opinion rendered by its financial
    advisor, the costs of remaining a public company, the fact that we were not
    able to realize the benefits associated with being a public company, the
    lack of liquidity for the holders of the common stock, the difficulty in
    obtaining and pursuing viable proposals for the purchase of AROC and that
    the Offer is at a price significantly higher than the recent market price of
    our common stock and the net proceeds that would otherwise be available in
    the event of a sale of the assets of AROC. See "Special Factors--The Special
    Committee's and the Board's Recommendation."

Q:  DID THE SPECIAL COMMITTEE RECEIVE ANY OPINIONS, APPRAISALS, OR REPORTS
    REGARDING THE FAIRNESS OF THE OFFER?

A:  Yes. The special committee received a written opinion, dated April 16, 2001,
    from Randall & Dewey, Inc. to the effect that, as of that date and based on
    and subject to the assumptions and limitations contained in the opinion, the
    Offer price of $0.06 per share is fair from a financial point of view to the
    existing unaffiliated holders of AROC's common stock. See "Special Factors--
    Opinion of the Financial Advisor to the Special Committee."

Q:  WILL AROC CONTINUE AS A PUBLIC COMPANY?

A:  The Board of Directors has not determined whether AROC will continue as a
    public company. MPAC has advised us that, if the Offer is consummated, they
    will consider a second-step transaction in which the remaining public
    stockholders would receive cash for their shares. As a result, MPAC would
    own 100% of AROC and we would no longer be publicly owned.

    If a second-step transaction does not occur, it is nevertheless likely that
    the shares will no longer be quoted on OTC and that AROC will no longer file
    reports with the SEC. Under these circumstances, we would become a private
    company with all remaining stockholders, other than MPAC, holding a minority
    equity position. See "Special Factors--Background and Purpose of the Offer,"
    "--Certain Effects of the Offer" and "--Plans of AROC after the Offer."

                                       3
<PAGE>

Q:  IF I DECIDE NOT TO TENDER, HOW WILL THE OFFER AFFECT MY SHARES?

A:  Stockholders not tendering in the Offer may receive in a second-step
    transaction, if it occurs, consideration that may or may not be cash and may
    be in an amount that may be higher, the same or lower than what they would
    have received had they tendered their shares in the Offer. If the Offer is
    consummated, and the number of shares owned by MPAC is greater than 90% of
    the then outstanding shares of each class of AROC's stock, then a second-
    step transaction could immediately commence between AROC and MPAC without
    soliciting approval of the stockholders.

    If the Offer is consummated and a second-step transaction does not occur,
    the number of shares of AROC common stock traded publicly will be reduced,
    which could adversely affect the liquidity and market value of the shares
    held by the public. Depending on the circumstances, in this case we could
    seek to remove our stock from the Pink Sheets and terminate our registration
    under the Exchange Act. See "Special Factors--Effects of the Offer."

Q:  WHAT IS THE MARKET VALUE OF MY SHARES AS OF A RECENT DATE?

A:  On April 18, 2001, the last trading day before the disclosure of the
    approval of this Offer, the closing market bid quotation of our common stock
    on the Pink Sheets was $0.01 per share. The sales price per share for AROC's
    common stock, as reported on May 2, 2001, was $0.025. We advise you to
    obtain a recent quotation for our common stock in deciding whether to tender
    your shares. See "Item 5. Market for Registrant's Common Equity and Related
    Shareholder Market Information and Dividends" in AROC's Annual Report on
    Form 10-K for the year ended December 31, 2000, a copy of which accompanies
    this Offer to Purchase.

Q:  IF I OBJECT TO THE PRICE BEING OFFERED, WILL I HAVE APPRAISAL RIGHTS?

A:  No. Appraisal rights are not available in the Offer. However, if you do not
    tender your shares in the Offer and a second-step transaction occurs and is
    effected as a merger, you may elect to dissent from the merger and have the
    fair value of your shares of AROC common stock paid to you in cash provided
    that you comply with the applicable provisions of the Delaware General
    Corporation Law. This fair value as determined in the second-step
    transaction could be less than the purchase price in the Offer. See "Special
    Factors--Dissenters' and Appraisal Rights of Stockholders."

Q:  WHO CAN I TALK TO IF I HAVE QUESTIONS ABOUT THE OFFER?

A:  If you have more questions about the Offer, you should contact: Investor
    Relations at AROC by telephone at (918) 491-1100, or by mail at 4200 East
    Skelly Drive, Suite 1000, Tulsa, Oklahoma 74135.

           CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS

     In the interest of providing the AROC's stockholders with certain
information regarding AROC's future plans and operations, certain statements set
forth in this Offer to Purchase relate to management's future plans and
objectives.  Such statements are "forward-looking statements" within the meaning
of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the
Securities Exchange Act of 1934, as amended.  Although any forward-looking
statements contained in this Offer to Purchase or otherwise expressed by or on
behalf of AROC are, to the knowledge and in the judgment of the officers and
directors of AROC, expected to prove true and to come to pass, management is not
able to predict the future with absolute certainty.  Forward-looking statements
involve known and unknown risks and uncertainties which may cause AROC's actual
performance and financial results in future periods to differ materially from
any projection, estimate or forecasted result.  These risks and uncertainties
include, among other things, volatility of oil and gas prices, competition,
risks inherent in AROC's oil and gas operations, the inexact nature of
interpretation of seismic and other geological and geophysical data, imprecision
of reserve estimates, AROC's ability to replace and expand oil and gas reserves,
and such other risks and uncertainties described from time to time in AROC's
periodic reports and filings with the SEC.  Accordingly, stockholders are
cautioned that certain events or circumstances could cause actual results to
differ materially from those projected, estimated or predicted.

                                       4
<PAGE>

                                 INTRODUCTION

     We, AROC Inc., a Delaware corporation, hereby offer to purchase any and all
of our shares of common stock, $0.001 par value per share, for a purchase price
of $0.06 per share, net to the seller in cash, without interest thereon, upon
the terms and subject to the conditions set forth in this Offer to Purchase and
in the related Letter of Transmittal.  Although the Offer is being made to all
holders of shares of our common stock, MPAC Energy, LLC, our single largest
stockholder, has advised us that it does not intend to tender any shares
pursuant to the Offer.  See "The Tender Offer--Terms of the Offer, Expiration
Date."  MPAC owns 30.8% of AROC's outstanding common stock and 100% of AROC's
convertible preferred stock.  On a fully diluted basis, MPAC beneficially owns
approximately 95.6% percent of our outstanding shares of common stock.  Any
tenders received in the Offer will increase MPAC's percentage ownership of AROC.

     ALL SHARES PROPERLY TENDERED AND NOT PROPERLY WITHDRAWN WILL BE PURCHASED
UPON THE TERMS AND SUBJECT TO THE CONDITIONS OF THE OFFER.  THE OFFER IS NOT
CONDITIONED UPON ANY MINIMUM NUMBER OF SHARES BEING TENDERED.  SEE "THE TENDER
OFFER--CERTAIN CONDITIONS OF THE OFFER," WHICH SETS FORTH IN FULL THE CONDITIONS
OF THE OFFER.

     As of March 1, 2001, 55,278,837 shares of common stock, 1,877,366 shares of
preferred stock convertible into a total of 722,034,927 shares of our common
stock, and 10,000,000 shares of convertible restricted voting shares convertible
into 5,000,000 shares of our common stock, are issued and outstanding.  As of
March 22, 2001, there were approximately 4,866 holders of record of the issued
and outstanding shares of our common stock.  Pursuant to the Offer, we are
seeking to acquire all shares of our issued and outstanding common stock.  The
board of directors formed a special committee consisting of the independent
director, who is not an officer or employee or otherwise affiliated with AROC or
MPAC, to consider the Offer determine whether to recommend the Offer.

     MPAC has advised us that if the Offer is consummated it will consider a
second-step transaction in which AROC would merge, consolidate or otherwise
combine with an entity to be formed and wholly owned by MPAC, or effect some
other form of corporate transaction such that the shares of our common stock not
owned by MPAC would be converted into only the right to receive some amount in
cash or other consideration, such other form of corporate transaction being
referred to as a "second-step transaction."  The consideration received in any
second-step transaction could be higher, the same or lower than the purchase
price in the Offer, although in all likelihood the consideration will be less
than the purchase price in the Offer.  If required by applicable laws, AROC will
seek stockholder approval of a second-step transaction.  Following completion of
any second-step transaction, MPAC  would own the entire equity interest in AROC.
However, MPAC or AROC are not obligated to effect and no agreement currently
exists relating to any second-step transaction.

     In determining whether to approve the Offer, the board and the special
committee considered a number of factors, several of which are listed below (see
"Special Factors--The Board's Approval and the Special Committee's
Recommendation"):

     .    There is virtually no market for AROC's common stock. The current
          market that does exist provides very limited liquidity for
          stockholders to liquidate or add to their investments. Additionally,
          because of the limited liquidity available, AROC has been unable to
          utilize effectively the public equity capital markets as a source of
          financing.

     .    There are considerable costs associated with remaining a public
          company. In addition to the time expended by AROC's management, the
          legal, accounting and other expenses involved in the preparation,
          filing and dissemination of annual and other periodic reports are
          considerable.

     .    The Offer price is significantly higher than the recent market price
          of the shares of common stock and the expected proceeds payable to
          holders of common stock if AROC or its assets were sold in the current
          market.

     In determining whether the Offer price to be paid to AROC's unaffiliated
stockholders is fair, the special committee relied on the fairness opinion dated
April 16, 2001 rendered by Randall & Dewey, Inc., to the effect that, as of that
date, and based on and subject to the assumptions and limitations contained
therein, the Offer price

                                       5
<PAGE>

of $0.06 per share is fair from a financial point of view to the existing
unaffiliated holders of AROC's common stock. See "Special Factors--Opinion of
Financial Adviser" for further information concerning the opinion of the
financial adviser.

     THE SPECIAL COMMITTEE HAS DETERMINED THAT THE OFFER IS FAIR TO, AND IN THE
BEST INTERESTS OF, AROC'S UNAFFILIATED STOCKHOLDERS, AND RECOMMENDS THAT AROC's
UNAFFILIATED STOCKHOLDERS ACCEPT THE OFFER AND TENDER THEIR SHARES PURSUANT TO
THE OFFER.

     We have filed with the SEC an Issuer Tender Offer Statement on Schedule TO.
The term, "expiration date," means 12:00 midnight, New York City time, on
June 12, 2001, unless and until we, in our sole discretion, extend the period
during which the Offer is open, in which event the term "expiration date" shall
mean the latest time and date at which the Offer, as so extended, shall expire.
See "The Tender Offer--Terms of the Offer; Expiration Date."

     The purchase price for the shares of common stock will be paid net to the
tendering stockholder in cash, without interest thereon, for all shares
purchased.  Tendering stockholders who hold shares of AROC's common stock in
their own name and who tender their shares directly to the Depositary will not
be obligated to pay brokerage commissions, solicitation fees or, subject to
Instruction 6 of the Letter of Transmittal, stock transfer taxes on the purchase
of shares by AROC pursuant to the Offer.  Stockholders holding shares of our
common stock through brokers or banks are urged to consult the brokers or banks
to determine whether transaction costs are applicable if stockholders tender
their shares through the brokers or banks and not directly to the Depositary.
However, any tendering stockholder or other payee who fails to complete, sign
and return to the Depositary the substitute form W-9 that is included as part of
the letter of transmittal may be subject to required United States Federal
Income Tax Back-up Withholding of 31% of the gross proceeds payable to the
tendering stockholder or other payee pursuant to the Offer.  See "Special
Factors--Material Federal Income Tax Consequences."

     THIS OFFER TO PURCHASE AND THE RELATED LETTER OF TRANSMITTAL CONTAIN
IMPORTANT INFORMATION THAT SHOULD BE READ BEFORE ANY DECISION IS MADE WITH
RESPECT TO THE OFFER.

                                       6
<PAGE>

                                SPECIAL FACTORS

BACKGROUND OF THE OFFER; ALTERNATIVES CONSIDERED

     Prior to 1999, AROC's predecessor, Alliance Resources Plc, was organized
under the laws of England and Wales and its stock was traded on the London Stock
Exchange.  In October 1999, the directors of Alliance recommended that Alliance
be combined with AROC because, among other things, the directors believed that
Alliance required additional financing to pursue its business plan of making
additional acquisitions of properties and that the most likely source of
financing to fund the business plan was from entities in the U.S.  This
combination was approved by a majority of the stockholders in December 1999.

     Consistent with the business plan, in May 2000, we completed the
acquisition of oil and gas properties having reserves with a standardized
measure of discounted cash flow of $62,000,000, a refinancing of $47,000,000 of
debt and issuance of a new series of preferred stock.  Effective August 11,
2000, several of the holders of this preferred stock then transferred their
stock to MPAC.  As a result of these transactions, MPAC has the right to vote
approximately 30.8% of our common stock and 100% of our preferred stock.

     During the summer of 2000, management of AROC and the predecessors of MPAC,
who owned a majority of AROC's voting shares, began consideration of various
options to provide liquidity for the minority stockholders of AROC.  Based on
these discussions, Mr. Keenan, AROC's President, proposed to the board that AROC
acquire for cash, in an amount to be determined by the board, all of the
outstanding common stock of AROC not held by the predecessors of MPAC.

     In October 2000, AROC issued a press release announcing its intention to
effect a reverse split on the terms recommended by a special committee and
approved by the board of directors.  After discussions with this special
committee and representatives of AROC's largest stockholder, management
determined that it would not be practical to complete the reverse split.  On
December 22, 2000, management announced that it had withdrawn the proposal.

     On December 4, 2000, Messrs. Phillip Douglas, William J. A. Kennedy and
John R. Martinson resigned as directors of AROC and three directors were elected
to fill the vacancies created by these resignations.  The three directors
elected were Robert L. Zorich, Gary R. Peterson and D. Martin Phillips.

     On March 8, 2001, the board of directors met to discuss the status and
direction of AROC, including proposed senior management changes, the current
liquidity of AROC's common stock, and other options involving AROC such as a
sale of AROC or its assets.  Upon completion of discussion, the board
unanimously agreed to all of the following: (i) AROC would provide liquidity for
the minority stockholders by commencing and completing a tender offer for all of
the shares of AROC's common stock not controlled by MPAC at a purchase price of
$0.06 per share; (ii) a special committee of the board composed of the outside
director would be formed to determine whether to approve the Offer and recommend
it to AROC's unaffiliated stockholders; (iii) Mr. Keenan would resign from all
positions with AROC and its affiliates upon the earlier to occur of the
completion of the Offer or 75 days from the date of the board meeting; (iv) upon
his resignation and in lieu of his existing severance arrangements with AROC,
Mr. Keenan would receive a severance payment from AROC of $900,000; (v) other
members of senior management are to receive severance payments in the same
proportion of the amounts provided under their employment agreements; (vi) Mr.
Keenan and other senior management and staff of AROC will work with
representatives of MPAC and new management of AROC in effecting a smooth
transition of its business; and (vii) during the interim period, all material
matters such as material contracts, severance arrangements, acquisitions and
dispositions will require prior board approval.  The board arrived at the price
of $0.06 per share based on their knowledge of AROC and its assets and the
current market price for shares of AROC common stock, but did not undertake any
formal analysis at the time of the proposed price.

     During March 2001, the special committee retained Randall & Dewey, Inc. as
financial advisor.  The financial advisor delivered a fairness opinion dated
April 16, 2001, to the effect that, as of such date, and based on and subject to
the assumption and limitations contained therein, the Offer price of $0.06 per
share is fair from a financial point of view to the existing unaffiliated
holders of AROC's common stock.  See "--Opinion of the Financial Advisor to the
Special Committee" below.

                                       7
<PAGE>

     Effective April 11, 2001, the members of the board of directors signed a
unanimous written consent approving written severance agreements with Messrs.
Keenan, Fenemore, Munchinski and Schulte providing for the payment of severance
payments to those individuals, that one-half of the restricted stock held by
those individuals would be vested upon the completion of the Offer, and that
AROC would pay those individuals the price of $0.06 per share for all shares
held by them upon completion of the Offer.

REASONS FOR AND PURPOSE OF THE OFFER

     The Board believes that the public trading market for the shares of AROC
common stock has been and will continue to be characterized by low prices and
low trading volume.  For these reasons, and because of the other factors
described in this Offer to Purchase, the Board is making the Offer is to provide
the holders of AROC common stock, other than MPAC, with liquidity for their
shares at a price that the special committee has determined to be fair to AROC's
unaffiliated stockholders.

INTERESTS OF CERTAIN PERSONS IN THE OFFER

     In considering the Offer and the fairness of the consideration to be
received in the Offer, stockholders should be aware that certain officers and
directors of AROC have interests in the Offer that are described below and which
may present them with certain actual or potential conflicts of interest.

     Some of the members of the board of directors have interests in the Offer
and related transactions that are different that the interests of the public
stockholders.  Messrs. Zorich, Peterson and Philips are managers of or otherwise
affiliated with MPAC, which is AROC's largest shareholder and whose ownership of
AROC will increase as a result of the Offer.  Messrs. Keenan and Fenemore are
officers of AROC and, upon completion of the Offer, will resign and receive
severance payments from AROC that will be less than the amount of severance that
these officers would otherwise be entitled to under their employment agreements.
Mr. Keenan and the other members of existing management intend to tender the
shares of AROC that they own in the Offer.

     Except as described herein, based on AROC's records and on information
provided to AROC by its directors and executive officers, neither AROC, nor any
associate or subsidiary of AROC nor, to the best of AROC's knowledge, any of the
directors or executive officers of AROC, nor any associates or affiliates of any
of the foregoing, has effected any transactions involving the shares of AROC's
common stock during the 60 business days prior to the date of this Offer to
Purchase.  Except as otherwise described herein, neither AROC nor, to the best
of AROC's knowledge, any of its affiliates, directors or executive officers, is
a party to any contract, arrangement, understanding or relationship with any
other person relating, directly or indirectly, to the Offer with respect to any
securities of AROC, including, but not limited to, any contract, arrangement,
understanding or relationship concerning the transfer or the voting of any such
securities, joint ventures, loan or option arrangements, puts or calls,
guarantees of loans, guarantees against loss or the giving or withholding of
proxies, consents or authorizations.

     In April 2001, Bank of America, one of the parties to the May 2000
transactions with AROC, contributed and assigned its shares of AROC common
stock, preferred stock and warrants to MPAC.

     Under the DGCL, corporations organized under the laws of Delaware are
permitted to indemnify their current and former directors, officers, employees
and agents under certain circumstances against certain liabilities and expenses
incurred by them by reason of their serving in such capacities.  AROC's
Certificate of Incorporation and Bylaws provide that each director and officer
will be indemnified by AROC against liabilities and expenses incurred in
connection with any threatened, pending or completed legal action or proceeding
to which he or she may be made a party or threatened to be made a party by
reason of being a director of AROC or a predecessor company, or serving any
other enterprise as a director or officer at the request of AROC.  AROC's
Certificate of Incorporation provides that, to the fullest extent that
limitations on the liability of directors and officers are permitted by the
DGCL, no director or officer of AROC shall have any liability to AROC or its
stockholders for monetary damages.  The DGCL provides that a corporation's
certificate of incorporation may include a provision which eliminates or limits
the personal liability of its directors or officers to the corporation or its
stockholders for money damages for breach of fiduciary duty as a director
except: (1) for any breach of the director's duty of loyalty to the corporation
or its stockholders; (2) for acts or omissions not in good faith or which
involve intentional

                                       8
<PAGE>

misconduct or a knowing violation of law; (3) for liability in connection with
the unlawful payment of dividends or unlawful stock purchases or redemptions; or
(4) for any transaction from which the director derived an improper personal
benefit. AROC has also purchased directors' and officers' liability insurance
for the benefit of these persons.

     For information on a significant transaction involving AROC and certain of
its affiliates which occurred on May 2, 2000, please see "Part I, Item 1.
Business--Recent Developments" in AROC's Annual Report on Form 10-K for the year
ended December 31, 2000, which accompanies this Offer to Purchase.

THE BOARD'S APPROVAL AND THE SPECIAL COMMITTEE'S RECOMMENDATION

     Although the board of directors unanimously approved the Offer, neither
AROC nor its board of directors make any recommendation to the stockholders as
to whether to tender or refrain from tendering their shares. However, the board
formed the special committee to consider the Offer and determine whether or not
to recommend the Offer to AROC's unaffiliated stockholders.

     The special committee has determined that the Offer is fair to, and in the
best interests of, AROC and its unaffiliated stockholders and recommends that
AROC's unaffiliated stockholders tender their shares of AROC common stock
pursuant to the Offer.

     In arriving at the decision to approve this Offer, the board of directors
considered a number of factors, including the following:

     .   There is virtually no trading market for AROC's common stock and we do
         not believe that an active market for AROC's stock at a higher price is
         likely to develop.

     .   Because AROC is the result of the combination of a number of companies
         and properties that had various degrees of financial difficulties prior
         to the combination and because our results continue to reflect the
         costly efforts to overcome these difficulties, the special committee
         and the board do not believe that it would be possible for AROC to
         complete an underwritten public offering of its shares that could be
         expected to generate additional investor interest in AROC's stock.

     .   Oil and gas prices are at the highest prices they have been in years,
         which the special committee and the board believe would afford AROC's
         minority stockholders an attractive price for their shares.

     In determining whether to recommend the Offer, the special committee also
considered the opinion of Randall & Dewey, Inc., as discussed below under
"--Opinion of the Financial Advisor to the Special Committee."

     The above discussion of the information and factors considered by the
special committee and the board of directors is not intended to be exhaustive.
In view of the variety of factors considered in connection with their evaluation
of the transaction, neither the special committee nor the board of directors
found it practical to and did not attempt to rank or assign relative weights to
the above factors.  In addition, the special committee and the board did not
undertake to determine whether any particular factor, or any aspect of any
particular factor, was favorable or unfavorable to their ultimate determination,
but rather conducted a discussion of the factors described above, including
asking questions of AROC's management and legal advisors, and reached a general
consensus.  Individual members of the board and the special committee may have
given different weights to different factors.  Finally, The special committee
relied on the experience and expertise of its financial advisor for quantitative
analysis of AROC's assets.

OPINION OF THE FINANCIAL ADVISOR TO THE SPECIAL COMMITTEE

     On March 29, 2001, the special committee engaged Randall & Dewey, Inc. to
act as financial advisor to the special committee in connection with the Offer.
The special committee did not retain an unaffiliated representative to act
solely on behalf of unaffiliated stockholders in connection with the Offer.  The
special committee instructed Randall & Dewey, Inc., in its role as financial
advisor to the special committee to render an

                                       9
<PAGE>

opinion as to the fairness, from a financial point of view, to the existing
unaffiliated holders of AROC's common stock of the Offer price. In connection
with this evaluation, the special committee authorized Randall & Dewey, Inc. to
conduct such investigations as Randall & Dewey, Inc. deemed appropriate.

     On April 16, 2001 Randall & Dewey, Inc. delivered its opinion to the
special committee to the effect that, as of that date and based on and subject
to the assumption and limitations contained in the opinion, from a financial
point of view, the consideration to be received by AROC's unaffiliated
stockholders in the Offer was fair to these stockholders.  Randall & Dewey, Inc.
has consented to AROC's disclosure of its opinion in this Offer to Purchase and
a copy of its opinion is attached as Appendix A to this document.  The summary
of the opinion set forth below is qualified in its entirety by Appendix A, which
is incorporated in this document by reference.  Stockholders are urged to read
the opinion in its entirety for a description of the assumptions made, matters
considered and procedures followed by Randall & Dewey, Inc.

     No limitations were imposed by the special committee upon Randall & Dewey,
Inc. with respect to the investigations made or the procedures followed by
Randall & Dewey, Inc. in rendering its opinion, and AROC and the members of its
management cooperated with Randall & Dewey, Inc. in connection with its
investigation.  The consideration to be received in connection with the tender
offer was determined by discussions among management of AROC, the special
committee and Randall & Dewey, Inc.  The opinion rendered by Randall & Dewey,
Inc. does not constitute a recommendation to any stockholder as to whether the
stockholders should tender any shares with respect to the tender offer.

     In arriving at its opinion, Randall & Dewey, Inc., among other things,
reviewed:

     .    a draft of this Offer to Purchase;

     .    certain publicly available business and financial information relating
          to AROC, including the Annual Reports on Form 10-K and related audited
          financial statements for the fiscal years ending April 30, 2000 and
          December 31, 2000;

     .    certain estimates of AROC's proved oil and gas reserve prepared by Lee
          Keeling & Associates, Inc., independent petroleum engineers, as of
          January 1, 2001;

     .    pro forma first quarter 2001 financial statements and operating
          reports reflective of the remaining assets net of asset sales
          concluded in the first quarter 2001;

     .    internal AROC operating and project performance summaries; and

     .    such other financial studies and analyses and took into account such
          other matters as it deemed necessary or appropriate.

     In reaching its opinion and conducting its analysis, Randall & Dewey, Inc.
did not assume any responsibility for independent verification of any of the
information discussed above and relied upon it being complete and accurate in
all material respects.  Randall & Dewey, Inc. also assumed that all of the
information, including the projections provided to Randall & Dewey, Inc. by
management of AROC was prepared in good faith, based upon reasonable estimates
and reflects the best judgment of the management of AROC as to the future
financial performance of AROC based upon the historical performance and
estimates and assumptions that were reasonable at the time made.  Randall &
Dewey, Inc.'s opinion is based on economic, monetary and market conditions
existing on the date of the opinion.

     Set forth below is a summary of the material analyses performed by Randall
& Dewey, Inc. in connection with the preparation of its opinion and included in
the presentation made by Randall & Dewey, Inc. to the special committee on
April 16, 2001.

          Description of Analyses.  The proforma balance sheet at March 31, 2001
     was utilized to calculate the implied enterprise value for AROC using the
     $0.06 per share Offer price.  Total debt of $16.56 million, working capital
     of $1.12 million and preferred shares of $97.36 million yielded total
     obligations

                                       10
<PAGE>

     as of March 31, 2001 of $112.8 million. Assuming the 10,000,000 convertible
     restricted voting shares were converted into 5,000,000 shares of common
     stock, the total number of shares of common stock outstanding would be
     60,278,837. At the Offer price of $0.06 per share, the current enterprise
     value was determined to be $116.4 million. The enterprise value expressed
     in terms of proved reserves was determined to be $5.59 per net barrel of
     oil equivalent (BOE) using the SEC reserves of 20.81 million BOE. The
     enterprise value of $116.4 million represents a multiple of 14.6 of
     annualized current period EBITDAX (earnings before interest, taxes,
     depreciation and amortization and exploration expenses).

          Comparable Company Analyses.  AROC's current production levels are
     disproportionately low relative to total reserves.  At year-end 2000,
     proved producing reserves represented only 31% of total reserves and the
     total reserve to production ratio was 24.8.  As a result of the diverse
     number and nature of AROC's producing and undeveloped assets, there are no
     other public exploration and production ("E&P") companies uniquely
     comparable to AROC.  In examining the range of publicly traded E&P
     companies for characteristics similar to AROC, Randall & Dewey, Inc.
     selected the ten E&P companies with an enterprise value greater than $100
     million whose reserve life and development status would result in a total
     reserve to production ratio greater than 15.0.  This would allow for an
     assessment of how the market currently values companies with these types of
     assets.  The ten companies are:  Pioneer Natural Resources Company, Vintage
     Petroleum Inc., Swift Energy Company, Evergreen Resources, Inc.,
     Quicksilver Resources, Inc., Encore Acquisition Company, Coho Energy, Inc.,
     Callon Petroleum Company, Berry Petroleum Company and Inland Resources,
     Inc.  For the ten companies selected, the enterprise value as of March 31,
     2001 expressed in terms of proven reserve value ranged from $2.91/BOE to
     $9.02/BOE with an average value of $4.79/BOE.  For this analysis, the
     enterprise value was calculated using December 31, 2000 balance sheet
     information and closing share prices as of March 31, 2001.  The average
     from the selected companies of $4.79/BOE is comparable to the Offer value
     of $5.59/BOE for AROC.  Evaluating the same ten companies' enterprise value
     expressed as a multiple of annualized current period EBITDAX resulted in a
     range of values from 2.9x to 10.0x with an average of 6.3x.  This compares
     to the Offer value of 14.6x.  The Offer multiple of 14.6x is significantly
     higher than the highest multiple in the selected group.

          Market Value Assessment.  Randall & Dewey, Inc. was provided with two
     reserve reports, one evaluated according to SEC guidelines (year-end prices
     of $26.80/Bbl and $9.78/MMBtu and costs held constant), and one evaluated
     using "Bank Pricing," (2001 oil prices of $20.00/Bbl, 2002 oil prices of
     $19.00 held constant for the remainder of the analysis, 2001 gas prices
     $3.00/MMBtu, 2002 gas prices of $2.75/MMBtu held constant for the remainder
     of the analysis).  The SEC evaluation resulted in price expectations
     significantly above Randall & Dewey, Inc.'s view of the asset markets'
     price view.  The Bank pricing evaluation resulted in price expectations
     below Randall & Dewey, Inc.'s opinion of the current asset markets' price
     view.  In order to evaluate the current market value of AROC's assets,
     Randall & Dewey, Inc. utilized the reserve forecasts prepared in accordance
     with SEC guidelines, but evaluated at prices reflective of the NYMEX
     forward curves as of March 26, 2001 declining to $4.00/MMBtu and $21.00/Bbl
     and held constant thereafter.  Randall & Dewey, Inc.'s Market Value
     Assessment ("MVA") is meant to represent the probable range of high bids to
     be expected in a competitive sales process.  It is not intended to predict
     the outlier or extreme bid levels that are sometimes experienced in
     competitive periods for high demand asset types.  Market discount rates and
     market risk factors were applied on each major project individually and
     then to the remaining aggregate.  The liquidation value in the current
     asset market for the AROC assets is expected to be in the range of $61.4 to
     $68.5 million.  Given the liquidation preference of the preferred stock of
     $97.4 million and existing debt of $16.5 million, Randall & Dewey, Inc.
     believes it is unlikely that the current common shareholders would receive
     any net proceeds in a liquidation at this time.

          There is virtually no current market in shares of AROC common stock,
     nor is there expected to be one in the immediate future.  No transaction
     premium analysis can be effectively evaluated.  AROC shares of common stock
     are more akin to an option on the potential of the asset value to increase
     to a level that exceeds projected obligations.  But upon exercise of this
     theoretical option, Randall & Dewey, Inc. believes the stockholder would
     most likely remain without a viable market for the shares of common stock.
     In this option valuation, not only is the volatility of the asset value a
     significant component, but also the likelihood and timing of an effective
     liquidity event.  No attempt was made to quantify this

                                       11
<PAGE>

     optionality, but Randall & Dewey, Inc. believes it is in effect an argument
     in support of the $0.06 per share offer.

     The preparation of a valuation opinion is a complex process and is not
necessarily susceptible to partial analysis or summary description.  Selecting
portions of the analyses or of the summary set forth above, without considering
the analyses as a whole, could create an incomplete view of the processes
underlying Randall & Dewey, Inc.'s opinion.  In arriving at its fairness
opinion, Randall & Dewey, Inc. considered the results of all such analyses.  The
analyses were prepared solely for purposes of Randall & Dewey, Inc. providing
its opinion to the special committee and does not purport to necessarily reflect
the prices at which assets or securities may be sold.  Analyses based upon
forecasts of future results are not necessarily indicative of actual future
results, which may be significantly more or less favorable than suggested by
such analyses.  Because such analyses are inherently subject to uncertainty,
being based upon numerous factors or events beyond the control of the parties or
their respective advisors, none of AROC, Randall & Dewey, Inc., or any other
person assumes responsibility if future results are materially different from
those forecast.

     As described above, Randall & Dewey, Inc.'s opinion to the special
committee was one of many factors taken into consideration by the special
committee in connection with its consideration of the Offer, and its opinion
does not constitute a recommendation as to whether any stockholder should tender
any shares with respect to the Offer.  The foregoing summary does not purport to
be a complete description of the analysis performed by Randall & Dewey, Inc. and
is qualified by reference to the valuation opinion of Randall & Dewey, Inc. set
forth in Appendix A to this document.  Randall & Dewey, Inc. has consented to
inclusion of its written opinion in this document.  In addition, a copy of
Randall & Dewey, Inc.'s opinion has been filed as an exhibit to the Schedule TO
filed with the SEC in connection with the Offer and is available for inspection
and copying at the principle executive offices of AROC during its regular
business hours by any stockholder or any representative of a stockholder who has
been designated in writing.  A copy of these materials will be provided by AROC
to any stockholder or any representative of a stockholder who has been so
designated in writing upon written request and at the expense of the requesting
stockholder.  See "Available Information."

     In June 2000, Randall & Dewey, Inc. was engaged to perform services for
AROC and was paid a customary fee of $25,000 for those services.  Randall &
Dewey, Inc. was formed in 1989 and provides specialized merger, acquisition,
divestment, petroleum advisory and capital solution services to the domestic and
international upstream oil and gas industry.  Clients include integrated
companies, public and private independent companies, financial institutions, and
other entities involved in world-wide energy industry.

EFFECTS OF THE OFFER

     Each stockholder who properly tenders his or her shares of common stock, as
of the effective date, will have his or her shares of common stock converted
into cash.  The interest of the stockholder in AROC will be terminated, and the
stockholder will have no right to share in the assets or future growth of AROC.
The only stockholder who it is known will remain after the Offer is MPAC.  The
Offer will therefore enable MPAC to increase its proportionate ownership.  All
shares purchased in the Offer will be held in treasury by AROC and will result
in a change in the capitalization of AROC.  Upon the earlier of May 22, 2001 or
the completion of the Offer, Messrs. Keenan, Fenemore and Humphries will resign
from the board and the remaining members of the board, all of whom are
affiliated with MPAC, will appoint new directors to fill the vacancies.  Messrs.
Keenan, Fenemore, Munchinski and Schulte will also resign from all senior
management and employment positions they have with AROC.

     If less than all of the shares owned by the public stockholders are
tendered pursuant to the Offer, MPAC will consider the pursuit of a second-step
transaction, in which the shares of AROC's common stock held by the remaining
public stockholders would be converted into the right to receive cash and MPAC
would thereafter own the entire equity interest in AROC.

     If less than all of the shares of AROC's common stock held by the public
stockholders are tendered pursuant to the Offer, and a second-step transaction
does not occur, the purchase of shares of our common stock by

                                       12
<PAGE>

AROC pursuant to the Offer will reduce the number of shares that might otherwise
trade publicly and will reduce the number of holders of shares, which could
adversely affect the liquidity and market value of the remaining shares held by
the public. Under these circumstances, given the continuing costs of public
reporting and compliance, AROC may seek to remove its stock from the Pink Sheets
and seek to terminate its registration under the Exchange Act if it has less
than 300 holders of record. Following these steps, AROC would become a private
company and there would be no public market for AROC's stock.

     The shares of AROC common stock are currently registered under the Exchange
Act, which requires, among other things, that AROC furnish certain information
to its stockholders and to the SEC and comply with the SEC's proxy rules in
connection with meetings of AROC's stockholders.  In addition, under Section
12(g) of the Exchange Act, registration under the Exchange Act may be terminated
by the issuer if there are fewer than 300 holders of record of a class of
security.  Shares held directly or indirectly by an officer or director of the
issuer or by any beneficial owner of more than 5% of the shares of the issuer
will ordinarily not be considered as being publicly held for this purpose.  In
the event the bid quotation for shares of AROC common stock were no longer
quoted on the Pink Sheets, price quotations might still be available from other
sources.  The extent of the public market for the shares of AROC common stock
and the availability of such quotations would, however, depend upon the number
of holders remaining at such time, the interest in maintaining a market in the
shares on the part of securities firms, the termination of registration under
the Exchange Act and other factors.

     The termination of the registration of the shares under the Exchange Act
would substantially reduce the information required to be furnished by us to our
stockholders and to the SEC and would render inapplicable certain provisions of
the Exchange Act, including requirements that AROC file periodic reports
(including financial statements), the requirements of Rule 13e-3 under the
Exchange Act with respect to "going private" transactions, requirements that
AROC's officers, directors and ten-percent stockholders file certain reports
concerning ownership of AROC's equity securities and provisions that any profit
by such officers, directors and stockholders realized through purchases and
sales of AROC's equity securities within any six-month period may be recaptured
by AROC.  In addition, the ability of "affiliates" of AROC and other persons to
dispose of shares of AROC common stock which are "restricted securities" under
Rule 144 under the Securities Act of 1933, as amended, may be impaired or
eliminated.  Except as disclosed in this section and elsewhere in this Offer to
Purchase, AROC has no other present plans or proposals that relate to or would
result in (i) the acquisition by any person of additional securities of AROC, or
the disposition of securities of AROC, (ii) any extraordinary corporate
transaction, such as a merger, reorganization, liquidation or sale or transfer
of a material amount of assets, involving AROC, (iii) any material change in the
present dividend policy or indebtedness or capitalization of AROC, (iv) any
other material change in AROC's corporate structure or business, or (v) any
change in AROC's certificate of incorporation, bylaws or instruments
corresponding thereto or any other actions which may impede the acquisition of
control of AROC by any person.

PLANS OF AROC AFTER THE OFFER

     Consummation of the Offer and a second-step transaction, if completed,
might result in future benefits to MPAC resulting from ownership of the entire
equity interest in AROC.  These benefits include management and investment
discretion with regard to the future conduct of the business of AROC, the
benefits of any profits generated by operations and any increase in AROC's
value.  Similarly, MPAC will also bear the risk of any decrease in the value of
AROC.

     A second-step transaction could be implemented through a merger of AROC
with a corporation to be formed and wholly owned by MPAC.  Under the Delaware
General Corporation Law, "DGCL," and AROC's certificate of incorporation, the
approval of the board and the affirmative vote of a majority of the outstanding
shares of AROC's common stock are required to approve a merger at a meeting of
the stockholders.  MPAC, who currently owns approximately 30.8% of the
outstanding shares of AROC's common stock and would own a greater percentage
after completion of the Offer, intends to vote all of its shares in favor of a
second-step transaction if it is proposed and if a stockholder vote is required.
MPAC expects to have sufficient voting power to cause the approval and adoption
of a second-step transaction immediately after the Offers, without the
affirmative vote of any other stockholders of AROC.  Under the DGCL, an entity
that owns 90% or more of the outstanding shares of each class of the outstanding
stock of another entity may effect a merger with such other entity without
submitting the merger to a vote of stockholders of the other entity.
Accordingly, if MPAC owns 90% or more of each class of

                                       13
<PAGE>

stock of AROC that remains outstanding after completion of the Offer, this type
of merger, known as a short-term merger, may be effected without a vote of
AROC's stockholders. If, however, the percentage of voting ownership of MPAC
after completion of the Offer is less than 90% of each class of stock of AROC, a
vote of AROC's stockholders will be required under the applicable laws, and a
longer period of time may be required to effect a merger.

     Following the Offer, the shares of AROC common stock may no longer be
quoted on the Pink Sheets, and, if there are less than 300 record stockholders
of AROC, the registration of the shares of AROC common stock under the Exchange
Act will be terminated and AROC will no longer file periodic reports with the
SEC.  If so, following the completion of the Offer, AROC will become a private
company and MPAC will succeed to a more dominant equity interest in AROC.  In
addition, MPAC will consider a second-step transaction to purchase any remaining
equity interest in AROC for cash.  Following the Offer and any second-step
transaction, there probably would be no publicly traded equity securities of
AROC outstanding.  However, MPAC or AROC are not obligated to effect and no
agreement currently exists relating to any second-step transaction.

DISSENTERS' OR APPRAISAL RIGHTS OF STOCKHOLDERS

     No dissenters' or appraisal rights are available to stockholders in
connection with the Offer.  Additionally, we have not made any provision for
stockholders to obtain counsel or appraisal services in connection with the
Offer at our expense.  However, if a second-step transaction is implemented
through a merger, the stockholders who have not tendered their shares will have
certain rights to dissent and demand appraisal of, and to receive payment in
cash of the fair value of their shares.

     If a dissenting stockholder were to exercise such appraisal rights in
connection with a merger, and if AROC and such stockholder were unable to agree
on the fair value of the shares, a court would determine the fair value of the
shares, as of the day prior to the date on which the stockholders' vote was
taken approving the merger.  The fair value of the shares would be paid in cash
to such dissenting stockholder.  In determining the fair value of the shares,
the court is required to take into account all relevant factors.  Accordingly,
such determination could be based upon considerations other than, or in addition
to, the market value of the shares, including, among other things, asset values
and earnings capacity.  Therefore, the value so determined in any appraisal
proceeding could be higher, the same or lower than, the purchase price received
in the Offer or in any second-step transaction.

CONDUCT OF AROC's BUSINESS AFTER THE OFFER

     In March 2001, MPAC entered into consulting agreements with Frank A.
Lodzinski and Jerry M. Crews to assist MPAC in connection with evaluating and
managing its investment in certain portfolio companies, including AROC.  Mr.
Lodzinski is the former Chairman of the Board, President, Chief Executive
Officer and a former Director of Texoil, Inc. (a Nasdaq Small Cap Market
company) from December 31, 1997 until the sale of Texoil to Ocean Energy, Inc.
(a NYSE company) in February 2001.  Prior to his positions with Texoil, Mr.
Lodzinski was the President and a director with Cliffwood Oil & Gas Corp., the
predecessor to Texoil, and  the President and a director of Hampton Resources
Corporation, a public company that was sold to Bellwether Exploration Company.
Mr. Crews is the former Executive Vice President of Texoil from December 31,
1997 until the sale to Ocean in February 2001.  Prior to his position with
Texoil, Mr. Crews was an officer and director with Cliffwood.  MPAC intends for
AROC to hire Mr. Lodzinski as Chief Executive Officer and Mr. Crews as Chief
Operating Officer of AROC, effective upon the departure of the current senior
management of AROC.  MPAC also intends for AROC to relocate its principal
offices to Houston, Texas, and to hire certain personnel who formerly worked
with Mr. Lodzinski and Mr. Crews at Texoil.  MPAC expects that Mr. Lodzinski and
Mr. Crews will continue their review of AROC, its assets, corporate structure,
capitalization, operations, properties and personnel to determine what changes
would be desirable following the Offer to enhance the operations, prospects and
value of AROC.

MATERIAL FEDERAL INCOME TAX CONSEQUENCES

     Sales of shares of AROC common stock by stockholders pursuant to the Offer
will be taxable transactions for federal income tax purposes and may also be
taxable transactions under applicable state, local, foreign and other tax laws.
This discussion is based upon laws, regulations, rulings and decisions now in
effect, all of which

                                       14
<PAGE>

are subject to change, possibly retroactively. No ruling as to any matter
discussed in this summary has been requested or received from the Internal
Revenue Service. The federal income tax consequences to a stockholder may vary
depending upon the stockholder's particular facts and circumstances.

     Under Section 302 of the Internal Revenue Code of 1986, as amended, a sale
of shares pursuant to the Offer will, as a general rule, be treated as a sale or
exchange if the receipt of cash upon the sale (a) is "substantially
disproportionate" with respect to the tendering stockholder, (b) results in a
"complete redemption" of all of the stock of AROC owned by the stockholder, or
(c) is "not essentially equivalent to a dividend" with respect to the tendering
stockholder.  If any of those three tests is satisfied, the tendering
stockholder will recognize gain or loss equal to the difference between the
amount of cash received by the stockholder pursuant to the Offer and the
stockholder's tax basis in the shares sold pursuant to the Offer.  Recognized
gain or loss will be capital gain or loss, assuming the shares were held as
capital assets, which will be long-term capital gain or loss if the shares are
held for more than one year.  If you are a certain type of entity or individual
(including insurance companies, tax-exempt organizations, financial institutions
or broker dealers, foreign stockholders and stockholders who acquired their
shares upon the exercise of options or otherwise as compensation), you may be
subject to special rules not discussed below.

     Capital gain recognized by an individual upon the sale of a capital asset
that has been held for more than one year will generally be subject to tax at a
rate not to exceed 20%.  Capital gain recognized from the sale of a capital
asset held for one year or less will be subject to tax at the ordinary income
tax rates.  Currently, the highest ordinary income tax rate is 39.6%.  In
addition, capital gain recognized by a corporate taxpayer will be subject to tax
at the ordinary income tax rates applicable to corporations.

     Capital losses recognized by an individual upon the sale of capital assets
are allowed only to the extent of capital gains from the sale of capital assets
plus $3,000.  Capital losses recognized by a corporation upon the sale of
capital assets are allowed only to the extent of capital gains from the sale of
capital assets.  Capital losses not utilized in any taxable year by an
individual may be carried forward indefinitely and allowed to the extent of
capital gains plus $3,000 in any future taxable year.  Capital losses not
utilized in any taxable year by a corporation generally must first be carried
back and allowed to the extent of capital gains in the three preceding taxable
years and then may be carried forward and allowed to the extent of capital gains
in the five succeeding taxable years.

     In determining whether any of the tests under Section 302 of the Internal
Revenue Code is satisfied, stockholders must take into account not only the
shares of AROC stock they actually own, but also any shares of AROC stock they
are deemed to own pursuant to the constructive ownership rules of Section 318 of
the Internal Revenue Code.  Pursuant to those constructive ownership rules, a
stockholder is deemed to own shares of stock actually owned, and in some cases
constructively owned, by certain related individuals or entities, and any stock
that the stockholder has the right to acquire by exercise of an option or by
conversion or exchange of a security.

     The receipt of cash upon the sale of shares pursuant to the Offer will be
"substantially disproportionate" with respect to the tendering stockholder if,
among other things, the percentage of the outstanding shares of voting stock and
common stock, respectively, actually and constructively owned by the stockholder
immediately following the sale of shares pursuant to the Offer (treating as no
longer outstanding all shares purchased pursuant to the Offer) is less than 80%
of the percentage of the outstanding voting stock and common stock,
respectively, actually and constructively owned by such stockholder immediately
before the sale of shares pursuant to the Offer (treating as outstanding all
shares purchased pursuant to the Offer).  Stockholders should consult their tax
advisors with respect to the application of the "substantially
disproportionate"test to their particular facts and circumstances. The receipt
of cash by a tendering stockholder will result in a "complete redemption" of the
stockholder's interest in AROC if all the stock actually and constructively
owned by the stockholder is sold pursuant to the Offer or otherwise and, if
applicable, the stockholder is eligible to waive and does effectively waive
attribution of all stock constructively owned by the stockholder in accordance
with Section 302(c) of the Internal Revenue Code. Stockholders should consult
their tax advisors with respect to the application of the "complete redemption"
test to their particular facts and circumstances.

     Even if the receipt of cash by a stockholder fails to satisfy the
"substantially disproportionate" test and the "complete redemption" test, such
stockholder may nevertheless satisfy the "not essentially equivalent to a
dividend" test if the stockholder's sale of shares pursuant to the Offer results
in a "meaningful reduction" in the

                                       15
<PAGE>

stockholder's proportionate interest in AROC. Whether a meaningful reduction has
occurred, and, therefore, whether the receipt of cash by a tendering stockholder
will be "not essentially equivalent to a dividend," will depend upon the
individual stockholder's facts and circumstances. Stockholders expecting to rely
upon the "not essentially equivalent to a dividend" test should therefore
consult their tax advisors as to its application in their particular situations.

     If none of the three tests under Section 302 of the Internal Revenue Code
is satisfied, the receipt of cash by a tendering stockholder pursuant to the
Offer will be treated as a dividend taxable as ordinary income to the extent
paid out of AROC's current or accumulated earnings and profits (without any
offset for the tendering stockholder's basis in the tendered shares).  Any
portion of the cash received by the tendering stockholder that is not paid out
of AROC's current or accumulated earnings and profits will first be a tax-free
return of capital to the extent of the stockholder's tax basis in the shares and
then a capital gain from the sale or exchange of property.

     In the case of a corporate stockholder, if the cash paid is treated as a
dividend, the dividend income may be eligible for the 70% dividends received
deduction.  The dividends received deduction is subject to certain limitations,
and may not be available if, among other things, the corporate stockholder does
not satisfy certain holding period requirements with respect to the shares or if
the shares are treated as "debt financed portfolio stock" within the meaning of
Section 246A(c) of the Internal Revenue Code.  Generally, if a dividend equals
or exceeds 10% of a corporate stockholder's tax basis in AROC stock and the
corporate stockholder has not held the stock for more than two years, the
dividend may be treated as an "extraordinary dividend" under Section 1059(a) of
the Internal Revenue Code, in which case such corporate stockholder's tax basis
in shares of AROC's stock retained by such stockholder would be reduced, but not
below zero, by the amount of the "non taxed portion" of the dividend, which is
generally the amount of the dividend's received deduction.  Any amount of the
non taxed portion of the dividend in excess of the stockholder's basis will
generally be treated as capital gain and will be recognized in the taxable year
in which the extraordinary dividend is received.  If a redemption of shares from
a corporate stockholder pursuant to the Offer is treated as a dividend as a
result of the stockholder's constructive ownership of other stock that it has an
option or other right to acquire, the portion of the extraordinary dividend not
otherwise taxed because of the dividends received deduction would reduce the
stockholder's adjusted tax basis only in its shares sold pursuant to the Offer,
and any excess of such non taxed portion over such basis would be currently
taxable as gain on the sale of such shares.  Except as may otherwise be provided
in applicable Treasury regulations, in the case of any redemption of stock which
is not pro rata as to all stockholders, any amount treated as a dividend under
the rules of Section 302 of the Internal Revenue Code is treated as an
extraordinary dividend without regard to the corporate stockholder's holding
period or the amount of the dividend.  Corporate stockholders should consult
their tax advisors as to the availability of the dividends received deduction
and the application of Section 1059 of the Internal Revenue Code.

     "Backup withholding" at a rate of 31% will apply to payments made to
stockholders pursuant to the Offer unless the stockholder has furnished its
taxpayer identification number in the manner prescribed in applicable Treasury
regulations, has certified under penalties of perjury that such number is
correct, has certified as to no loss of exemption from backup withholding and
meets certain other conditions.  Any amounts withheld from payments made to
stockholders pursuant to the Offer under the backup withholding rules generally
will be allowed as a refund or a credit against such stockholder's United States
federal income tax liability, provided the required information is furnished to
the IRS.

     To avoid the imposition of the backup withholding, stockholders who are
U.S. persons should submit to the Depositary the Form W-9 included with the
Letter of Transmittal, and stockholders who are non-U.S. persons should submit
to the Depositary Form W-8BEN.  Stockholders should consult their tax advisors
to determine whether or not they will be treated as a U.S. person for purposes
of backup withholding.

     THE TAX DISCUSSION SET FORTH ABOVE IS INCLUDED FOR GENERAL INFORMATION ONLY
AND IS BASED ON THE FEDERAL INCOME TAX LAW NOW IN EFFECT, WHICH IS SUBJECT TO
CHANGE, POSSIBLY RETROACTIVELY.  THE TAX CONSEQUENCES OF A SALE PURSUANT TO THE
OFFER MAY VARY DEPENDING UPON, AMONG OTHER THINGS, THE PARTICULAR CIRCUMSTANCES
OF THE TENDERING STOCKHOLDER.  NO INFORMATION IS PROVIDED HEREIN AS TO THE
STATE, LOCAL OR FOREIGN TAX CONSEQUENCES OF THE TRANSACTION CONTEMPLATED BY THE
OFFER.  STOCKHOLDERS ARE URGED TO CONSULT THEIR OWN TAX ADVISORS TO DETERMINE
THE PARTICULAR FEDERAL, STATE, LOCAL AND FOREIGN TAX CONSEQUENCES OF SALES MADE
BY THEM PURSUANT TO THE OFFER AND THE EFFECT OF THE RULES DESCRIBED ABOVE.

                                       16
<PAGE>

                                 THE TENDER OFFER

TERMS OF THE OFFER; EXPIRATION DATE

     Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of such extension or
amendment), AROC will accept for payment and pay for all shares of our common
stock validly tendered prior to the expiration date and not withdrawn in
accordance with "The Tender Offer--Withdrawal Rights" at a price of $0.06 per
share, the "purchase price," net to the seller in cash, without  interest
thereon.  The "expiration date" means 12:00 midnight, New York City time, on
June 12, 2001, unless and until we, in our sole discretion, extend the period
during which the Offer is open, in which event "expiration date" shall mean the
latest time and date at which the Offer, as so extended, shall expire.

     We expressly reserve the right, in our sole discretion, at any time and
from time to time, to extend for any reason the period of time during which the
Offer is open, including the occurrence of any of the conditions specified in
"The Tender Offer--Certain Conditions of the Offer," by giving oral or written
notice of such extension to the Depositary.  During any extension, all shares
previously tendered and not withdrawn will remain subject to the Offer, subject
to the rights of a tendering stockholder to withdraw such stockholder's shares.
See "The Tender Offer--Withdrawal Rights."

     Subject to the applicable regulations of the SEC, AROC also expressly
reserves the right, in our sole discretion, at any time and from time to time,
(i) to delay acceptance for payment of, or, regardless of whether such shares
were theretofore accepted for payment, payment for, any shares, pending receipt
of any regulatory approval specified in "The Tender Offer--Certain Legal Matters
and Regulatory Approvals," (ii) to terminate the Offer and not accept for
payment any shares upon the occurrence of any of the conditions specified in
"The Tender Offer--Certain Conditions of the Offer" and (iii) to waive any
condition or otherwise amend the Offer in any respect, by giving oral or written
notice of such delay, termination, waiver or amendment to the Depositary and by
making a public announcement thereof.  We acknowledge that (i) Rule 13e-4(f)
under the Exchange Act requires us to pay the consideration offered or return
the shares tendered promptly after the termination or withdrawal of the Offer
and (ii) we may not delay acceptance for payment of, or payment for (except as
provided in clause (i) of the first sentence of this paragraph), any shares upon
the occurrence of any of the conditions specified in "The Tender Offer--Certain
Conditions of the Offer" without extending the period of time during which the
Offer is open.

     Any such extension, delay, termination, waiver or amendment will be
followed as promptly as practicable by public announcement, mailing a notice to
all stockholders, or filing a Form 8-K, such announcement in the case of an
extension to be made no later than 9:00 a.m., New York City time, on the next
business day after the previously scheduled expiration date.  Subject to
applicable law (including Rules 13e-3(e)(2), 13e-4(e)(3) and 13e-4(f) under the
Exchange Act, which require that material changes be promptly disseminated to
stockholders in a manner reasonably designed to inform them of such changes) and
without limiting the manner in which we may choose to make any public
announcement, we shall have no obligation to publish, advertise or otherwise
communicate any such public announcement other than by filing a Form 8-K.

     If we make a material change in the terms of the Offer or other information
concerning the Offer, or if it waives a material condition of the Offer, AROC
will extend the Offer to the extent required by Rules 13e-3(e)(2), 13e-4(e)(3)
and 13e-4(f) under the Exchange Act.  The minimum period during which an offer
must remain open following material changes in the terms of the Offer or
information concerning the Offer, other than a change in price or a change in
the percentage of securities sought, will depend on the facts and circumstances
then existing, including the relative materiality of the changed terms or
information.  With respect to a change in price or a change in the percentage of
securities sought, a minimum period of ten business days is generally required
to allow for adequate dissemination to stockholders and investor response.

     If, prior to the expiration date, we decide to decrease the number of
shares being sought or to increase or decrease the consideration being offered
in the Offer, such decrease in the number of shares being sought or such
increase or decrease in the consideration being offered will be applicable to
all stockholders whose shares are accepted for payment pursuant to the Offer
and, if at the time notice of any such decrease in the number of shares being
sought or such increase or decrease in the consideration being offered is first
published, sent or given to

                                       17
<PAGE>

holders of such shares, the Offer is scheduled to expire at any time earlier
than the period ending on the tenth business day from and including the date
that such notice is first so published, sent or given, the Offer will be
extended at least until the expiration of such ten business day period. For
purposes of this Offer, a "business day" means any day other than a Saturday,
Sunday or federal holiday and consists of the time period from 12:01 a.m.
through 12:00 midnight, New York City time.

     Pursuant to Rule 13e-4(f)(6), under the Exchange Act, we may not make any
purchases of AROC common stock or any right to purchase AROC common stock
otherwise than pursuant to the Offer until the expiration of at least ten
business days after the expiration date of the Offer.

     This Offer to Purchase and the related Letter of Transmittal will be mailed
to record holders of AROC common stock whose names appear on AROC's stockholder
list and will be furnished, for subsequent transmittal to beneficial owners of
shares, to brokers, dealers, commercial banks, trust companies and similar
persons whose names, or the names of whose nominees, appear on the stockholder
list or, if applicable, who are listed as participants in a clearing agency's
security position listing.

ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES

     Upon the terms and subject to the conditions of the Offer (including, if
the Offer is extended or amended, the terms and conditions of any such extension
or amendment), we will accept for payment and pay for (and thereby purchase) all
shares properly tendered and not properly withdrawn prior to the expiration
date.  All questions as to the satisfaction of such terms and conditions will be
determined by AROC in our sole discretion, which determination will be final and
binding.  See "The Tender Offer--Terms of the Offer; Expiration Date" and
"--Certain Conditions of the Offer."

     Upon the terms and subject to the conditions of the Offer, promptly after
the expiration date, AROC will accept for payment and pay a purchase price in
cash of $0.06 per share for any and all shares of our common stock properly
tendered, and not properly withdrawn.  AROC expressly reserves the right to
extend the expiration date pending receipt of any regulatory approvals specified
in "The Tender Offer--Certain Legal Matters and Regulatory Approvals" or
withdraw or extend the Offer in order to comply in whole or in part with any
other applicable law.

     In all cases, payment for shares of our common stock tendered and accepted
for payment pursuant to the Offer will be made only after timely receipt by the
Depositary of (i) the certificates evidencing such shares pursuant to the
procedures set forth in "The Tender Offer--Procedures for Accepting the Offer
and Tendering Shares," (ii) the Letter of Transmittal, properly completed and
duly executed, with any required signature guarantees and (iii) any other
documents required under the Letter of Transmittal.

     For purposes of the Offer, AROC will be deemed to have accepted for payment
(and thereby purchased) shares of our common stock validly tendered and not
properly withdrawn as, if and when AROC gives oral or written notice to the
Depositary of our acceptance for payment of such shares pursuant to the Offer.
Upon the terms and subject to the conditions of the Offer, payment for shares
accepted for payment pursuant to the Offer will be made by deposit of the
purchase price therefor with the Depositary, which will act as agent for
tendering stockholders for the purpose of receiving payments from AROC and
transmitting such payments to tendering stockholders whose shares have been
accepted for payment.  Under no circumstances will interest on the purchase
price for shares be paid, regardless of any delay in making such payment.

     AROC will pay all stock transfer taxes, if any, payable on the transfer to
us of shares purchased pursuant to the Offer.  If, however, payment of the
purchase price is to be made to, or (in the circumstances permitted by the
Offer) if unpurchased shares are to be registered in the name of, any person
other than the registered holder, or if tendered certificates are registered in
the name of any person other than the person signing the Letter of Transmittal,
the amount of all stock transfer taxes, if any (whether imposed on the
registered holder or the other person), payable on account of the transfer to
the person will be deducted from the purchase price unless satisfactory evidence
of the payment of the stock transfer taxes, or exemption therefrom, is
submitted.  See Instruction 6 of the Letter of Transmittal.

                                       18
<PAGE>

PROCEDURES FOR ACCEPTING THE OFFER AND TENDERING SHARES

     In order for a holder of shares of our common stock validly to tender
shares pursuant to the Offer, the Letter of Transmittal, properly completed and
duly executed, together with any required signature guarantees and any other
documents required by the Letter of Transmittal, must be received by the
Depositary at one of its addresses set forth on the back cover of this Offer to
Purchase and either (i) the share certificates evidencing tendered shares must
be received by the Depositary prior to the expiration date, or (ii) the
tendering stockholder must comply with the guaranteed delivery procedures
described below.

     A STOCKHOLDER WHO HOLDS SHARES THROUGH A BROKER OR BANK IS URGED TO CONSULT
ITS BROKER OR BANK TO DETERMINE WHETHER TRANSACTION COSTS ARE APPLICABLE IF THE
STOCKHOLDER TENDERS ITS SHARES THROUGH THE BROKER OR BANK AND NOT DIRECTLY TO
THE DEPOSITARY.

     THE METHOD OF DELIVERY OF SHARE CERTIFICATES AND ALL OTHER REQUIRED
DOCUMENTS IS AT THE OPTION AND RISK OF THE TENDERING STOCKHOLDER, AND THE
DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY.  IF
DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY
INSURED, IS RECOMMENDED.  IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO
ENSURE TIMELY DELIVERY.

     Signature Guarantees.  Signatures on all Letters of Transmittal must be
guaranteed by a firm that is a member of the Medallion Signature Guarantee
Program, or by any other "eligible guarantor institution," as such term is
defined in Rule 17Ad-15 under the Exchange Act, an "Eligible Institution,"
except in cases where shares are tendered (i) by a registered holder of shares
who has not completed either the box entitled "Special Payment Instructions" or
the box entitled "Special Delivery Instructions" on the Letter of Transmittal or
(ii) for the account of an Eligible Institution.  If a share certificate is
registered in the name of a person other than the signer of the Letter of
Transmittal, or if payment is to be returned, to a person other than the
registered holder(s), then the share certificate must be endorsed or accompanied
by appropriate stock powers, in either case signed exactly as the name(s) of the
registered holder(s) appear on the share certificate, with the signature(s) on
such share certificate or stock powers guaranteed by an Eligible Institution.
See Instructions 1 and 6 of the Letter of Transmittal.

     Guaranteed Delivery.  If a stockholder desires to tender shares of our
common stock pursuant to the Offer and the certificates evidencing the
stockholder's shares are not immediately available or the stockholder cannot
deliver the share certificates and all other required documents to the
Depositary prior to the expiration date, the shares may nevertheless be
tendered, provided that all the following conditions are satisfied:

     a.   the tender is made by or through an Eligible Institution;

     b.   a properly completed and duly executed Notice of Guaranteed Delivery,
          substantially in the form made available by AROC is received prior to
          the expiration date by the Depositary as provided below; and

     c.   the certificates, in proper form for transfer, together with the
          Letter of Transmittal, properly completed and duly executed, with any
          required signature guarantees, and any other documents required by the
          Letter of Transmittal are received by the Depositary within three
          trading days after the date of execution of the Notice of Guaranteed
          Delivery.

     The Notice of Guaranteed Delivery may be delivered by hand or mail or
transmitted by telegram or facsimile transmission to the Depositary and must
include a guarantee by an Eligible Institution in the form set forth in the form
of Notice of Guaranteed Delivery made available by AROC.

     In all cases, payment for shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by the Depositary of the
share certificates evidencing such shares, and the Letter of Transmittal,
properly completed and duly executed, with any required signature guarantees,
and any other documents required by the Letter of Transmittal.

     Determination of Validity.  All questions as to the number of shares to be
accepted, the validity, form, eligibility (including time of receipt) and
acceptance for payment of any tender of shares will be determined by

                                       19
<PAGE>

AROC in our sole discretion, which determination shall be final and binding on
all parties. AROC reserves the absolute right to reject any and all tenders
determined by it not to be in proper form or the acceptance for payment of which
may, in the opinion of its counsel, be unlawful. AROC also reserves the absolute
right to waive any condition of the Offer or any defect or irregularity in the
tender of any shares of any particular stockholder, whether or not similar
defects or irregularities are waived in the case of other stockholders. No
tender of shares will be deemed to have been validly made until all defects and
irregularities have been cured or waived. None of AROC, the Depositary, the
Information Agent or any other person will not be under any duty to give
notification of any defects or irregularities in tenders or incur any liability
for failure to give any such notification. Our interpretation of the terms and
conditions of the Offer, including the Letter of Transmittal and the
instructions thereto, will be final and binding.

     Lost, Destroyed or Stolen Certificates.  If any certificates for the shares
have been lost, destroyed or stolen, stockholders should contact the Depositary
immediately at the address and telephone number set forth on the back cover of
this Offer to Purchase.  In such event, the Depositary will forward additional
documentation necessary to be completed in order to surrender effectively such
lost, destroyed or stolen certificates.  The purchase price with respect to the
relevant shares will not be paid until the procedures for replacing lost,
destroyed or stolen certificates have been followed.

     Other Requirements.  By executing the Letter of Transmittal as set forth
above, a tendering stockholder irrevocably appoints designees of AROC as the
stockholder's proxies, each with full power of substitution, in the manner set
forth in the Letter of Transmittal, to the full extent of the stockholder's
rights with respect to the shares tendered by the stockholder and accepted for
payment by AROC and with respect to any and all shares or other securities
issued or issuable in respect of the shares on or after May 14, 2001.  All the
proxies shall be considered coupled with an interest in the tendered shares.
The appointment will be effective when, and only to the extent that, AROC
accepts the shares for payment.  Upon acceptance for payment, all prior proxies
given by the stockholder with respect to the shares (and any other shares and
securities) will be revoked without further action, and no subsequent proxies
may be given nor any subsequent written consent executed by the stockholder
(and, if given or executed, will not be deemed to be effective) with respect
thereto.  The designees of AROC will, with respect to the shares for which the
appointment is effective, be empowered to exercise all voting and other rights
of the stockholder as they in their sole discretion may deem proper at any
annual or special meeting of AROC's stockholders or any adjournment or
postponement thereof, by written consent in lieu of any  meeting or otherwise.

     TO PREVENT BACKUP FEDERAL INCOME TAX WITHHOLDING WITH RESPECT TO PAYMENT TO
CERTAIN STOCKHOLDERS OF THE PURCHASE PRICE OF SHARES PURCHASED PURSUANT TO THE
OFFER, EACH STOCKHOLDER MUST PROVIDE THE DEPOSITARY WITH THE STOCKHOLDER'S
CORRECT TAXPAYER IDENTIFICATION NUMBER AND CERTIFY THAT THE STOCKHOLDER IS NOT
SUBJECT TO BACKUP FEDERAL INCOME TAX WITHHOLDING BY COMPLETING THE SUBSTITUTE
FORM W-9 IN THE LETTER OF TRANSMITTAL.  IF BACKUP WITHHOLDING APPLIES WITH
RESPECT TO A STOCKHOLDER, THE DEPOSITARY IS REQUIRED TO WITHHOLD 31% OF ANY
PAYMENTS MADE TO THE STOCKHOLDER.  SEE INSTRUCTION 9 OF THE LETTER OF
TRANSMITTAL.

     Tendering Stockholder's Representation and Warranty; AROC's Acceptance
Constitutes an Agreement.  A tender of shares pursuant to any of the procedures
described above will constitute the tendering stockholder's acceptance of the
terms and conditions of the Offer, as well as the tendering stockholder's
representation and warranty to AROC that (a) the stockholder has a "net long
position" (as defined in Rule 14e-4 promulgated by the SEC under the Exchange
Act) in the shares or equivalent securities at least equal to the shares
tendered within the meaning of Rule 14e-4 and (b) the tender of shares complies
with Rule 14e-4.  It is a violation of Rule 14e-4 for a person, directly or
indirectly, to tender shares for that person's own account unless, at the time
of tender (including any extensions thereof), the person so tendering (i) has a
net long position equal to or greater than the amount of (x) shares tendered or
(y) other securities immediately convertible into or exchangeable or exercisable
for the shares tendered and will acquire the shares for tender by conversion,
exchange or exercise and (ii) will deliver or cause to be delivered the shares
in accordance with the terms of the Offer.  Rule 14e-4 provides a similar
restriction applicable to the tender or guarantee of a tender on behalf of
another person.  AROC's acceptance for payment of shares tendered pursuant to
the Offer will constitute a binding agreement between the tendering stockholder
and AROC upon the terms and conditions of the Offer.

     CERTIFICATES FOR SHARES, TOGETHER WITH A PROPERLY COMPLETED LETTER OF
TRANSMITTAL AND ANY OTHER DOCUMENTS REQUIRED BY THE LETTER OF TRANSMITTAL, MUST
BE DELIVERED TO THE DEPOSITARY AND NOT TO AROC.

                                       20
<PAGE>

ANY SUCH DOCUMENTS DELIVERED TO AROC WILL NOT BE FORWARDED TO THE DEPOSITARY AND
THEREFORE WILL NOT BE DEEMED TO BE PROPERLY TENDERED.

WITHDRAWAL RIGHTS

     Tenders of shares of our common stock made pursuant to the Offer are
irrevocable except that the tendered shares may be withdrawn at any time prior
to the expiration date and, unless accepted for payment by AROC pursuant to the
Offer, may also be withdrawn at any time after May 14, 2001.  If AROC extends
the Offer, is delayed in its acceptance for payment of shares or is unable to
accept shares for payment pursuant to the Offer, the Depositary may,
nevertheless, on behalf of AROC, retain tendered shares, and the shares may not
be withdrawn except to the extent that tendering stockholders are entitled to
withdrawal rights as described in this section.

     For a withdrawal to be effective, a written, telegraphic or facsimile
transmission notice of withdrawal must be timely received by the Depositary at
one of its addresses set forth on the back cover page of this Offer to Purchase.
Any notice of withdrawal must specify the name of the person who tendered the
shares to be withdrawn, the number of shares to be withdrawn and the name of the
registered holder of the shares, if different from that of the person who
tendered the shares.  If certificates evidencing shares to be withdrawn have
been delivered or otherwise identified to the Depositary, then, prior to the
physical release of these certificates, the serial numbers shown on the
certificates must be submitted to the Depositary and the signature(s) on the
notice of withdrawal must be guaranteed by an Eligible Institution, unless the
shares have been tendered for the account of an Eligible Institution.

     All questions as to the form and validity (including the time of receipt)
or any notice of withdrawal will be determined by AROC, in its sole discretion,
whose determination will be final and binding.  None of AROC, the Information
Agent or any other person will be under any duty to give notification of any
defects or irregularities in any notice of withdrawal or incur any liability for
failure to give any such notification.

     Any shares properly withdrawn will thereafter be deemed not to have been
validly tendered for purposes of the Offer.  However, withdrawn shares may be
re-tendered at any time prior to the expiration date by following one of the
procedures described in "The Tender Offer--Procedures for Accepting the Offer
and Tendering Shares."

DIVIDENDS AND DISTRIBUTIONS

     Although AROC is currently restricted from paying dividends under our
credit agreement with Toronto Dominion Bank, if, on or after May 14, 2001, AROC
should declare or pay any dividend on the shares of common stock or make any
other distribution (including the issuance of additional shares of capital stock
pursuant to a stock dividend or stock split, the issuance of other securities or
the issuance of rights for the purchase of any securities) with respect to the
shares of common stock that is payable or distributable to stockholders of
record on a date prior to the transfer to the name of AROC on AROC's stock
transfer records of the shares purchased pursuant to the Offer, then, without
prejudice to AROC's rights under "The Tender Offer--Certain Conditions of the
Offer," (i) the purchase price per share payable by AROC pursuant to the Offer
will be reduced to the extent any such dividend or distribution is payable in
cash; and (ii) any non-cash dividend, distribution or right shall be received
and held by the tendering stockholder for the account of AROC and will be
required to be promptly remitted and transferred by each tendering stockholder
to the Depositary for the account of AROC, accompanied by appropriate
documentation of transfer.

CERTAIN CONDITIONS OF THE OFFER

     Notwithstanding any other provision of the Offer, AROC shall have the right
to amend the Offer or terminate the Offer and not accept for payment or pay for
any shares tendered pursuant to the Offer, if prior to the acceptance for
payment of shares, any of the following conditions exist:

     a.   there shall have been threatened, instituted or pending any action or
          proceeding by any government or governmental, regulatory or
          administrative agency, authority or tribunal or any other person,
          domestic or foreign, before any court, authority, agency or tribunal
          that directly or indirectly (i) challenges the making of the Offer,
          the acquisition of some or all of the shares

                                       21
<PAGE>

          pursuant to the Offer or otherwise relates in an adverse manner to the
          Offer, or (ii) in AROC's reasonable judgment, could materially and
          adversely affect the business, condition (financial or other), income,
          operations or prospects of AROC and its subsidiaries, taken as a
          whole, or otherwise materially impair in any way the contemplated
          future conduct of the business of AROC and its subsidiaries;

     b.   there shall have been any action threatened, pending or taken, or
          approval withheld, or any statute, rule, regulation, judgment, order
          or injunction threatened, proposed, sought, promulgated, enacted,
          entered, amended, enforced or deemed to be applicable to the Offer or
          AROC or any of its subsidiaries, by any court or any authority, agency
          or tribunal that, in AROC's reasonable judgment, would or might
          directly or indirectly (i) make the acceptance for payment of, or
          payment for, some or all of the shares illegal or otherwise restrict
          or prohibit consummation of the Offer, (ii) restrict AROC's ability or
          render AROC unable to accept for payment or pay for some or all of the
          shares, or (iii) materially and adversely affect the business,
          condition (financial or other), income, operations or prospects of
          AROC and its subsidiaries, taken as a whole;

     c.   there shall have occurred (i) any prolonged general suspension of
          trading in, or limitation on prices for, securities on any national
          securities exchange or in the over-the-counter market, (ii) the
          declaration of a banking moratorium or any suspension of payments in
          respect of banks in the United States, (iii) the commencement of a
          war, armed hostilities or other international or national calamity
          directly or indirectly involving the United States, (iv) any
          limitation (whether or not mandatory) by any governmental, regulatory
          or administrative agency or authority on, or any event that, in AROC's
          reasonable judgment, might materially and adversely affect the
          extension of credit by banks or other lending institutions in the
          United States, (v) any change in the general political, market,
          economic or financial conditions in the United States or abroad that
          could, in the reasonable judgment of AROC, have a material adverse
          effect on AROC's business, operations or prospects, or (vi) in the
          case of any of the foregoing existing at the time of the commencement
          of the Offer, a material acceleration or worsening thereof;

     d.   a tender or exchange offer for all or substantially all of the shares
          of AROC's common stock on terms more favorable to AROC's unaffiliated
          stockholders, or any merger, business combination or other similar
          transaction with or involving AROC shall have been proposed, announced
          or made by any person;

     e.   (i) any entity, person or "group" (as that term is used in Section
          13(d)(3) of the Exchange Act) shall have acquired or proposed to
          acquire beneficial ownership of more than 5% of the  outstanding
          shares of AROC's common stock (other than any such person, entity or
          group who has filed a Schedule 13D or Schedule 13G with the SEC on or
          before April 30, 2001), (ii) any such entity, group or person who has
          filed a Schedule 13D or Schedule 13G with the SEC on or before the
          expiration date of the Offer shall have acquired or proposed to
          acquire beneficial ownership of an additional 2% or more of the
          outstanding shares of AROC's common stock, or (iii) any person, entity
          or group shall have filed a Notification and Report Form under the
          Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, or
          made a public announcement reflecting an intent to acquire AROC or any
          of its assets or securities other than in connection with a
          transaction authorized by the board of directors of AROC; or

     f.   any change or changes shall have occurred in the business, financial
          condition, assets, income,  operations, prospects or stock ownership
          of AROC and its subsidiaries that, in AROC's reasonable judgment, is
          of or may have a material adverse significance to AROC or its
          subsidiaries, taken as a whole.

     The foregoing conditions are for the sole benefit of AROC and may be
asserted by AROC regardless of the  circumstances giving rise to any such
condition or may be waived by AROC in whole or in part at any time and from time
to time prior to the expiration date in its sole discretion.  The failure by
AROC at any time to exercise any of the foregoing rights shall not be deemed a
waiver of that right; the waiver of any right with respect to

                                       22
<PAGE>

particular facts and other circumstances shall not be deemed a waiver with
respect to any other facts and circumstances; and each right shall be deemed an
ongoing right that may be asserted at any time and from time to time prior to
the expiration date.

SOURCE OF FUNDS FOR AND EXPENSES OF THE OFFER

     AROC estimates that payments for tendered shares will aggregate
approximately $2,200,000 and likely will aggregate significantly less than that
amount.  AROC intends to use internally generated funds and available cash to
purchase shares pursuant to the Offer and to pay related fees and expenses of
the Offer.

     The special committee of the board of directors of AROC retained Randall &
Dewey, Inc. to act as its financial advisor in connection with the Offer.  The
engagement letter between AROC and Randall & Dewey, Inc. provides that AROC will
pay Randall & Dewey, Inc. a fee of $30,000.  In addition, the engagement letter
provides that AROC will reimburse Randall & Dewey, Inc. for any reasonable out-
of-pocket expenses as may be related to travel as requested by AROC, and will
indemnify Randall & Dewey, Inc. and certain related persons against any and all
liabilities, including liabilities under securities laws, arising out of its
engagement.

     AROC has retained Registrar and Transfer Company to act as Depositary in
connection with the Offer.  The Depositary will receive reasonable and customary
compensation for its services, will be reimbursed by AROC for certain reasonable
out-of-pocket expenses and will be indemnified against certain liabilities in
connection with the Offer, including certain liabilities under the federal
securities laws.

     No fees or commissions will be payable by AROC to brokers, dealers or other
persons for soliciting tenders of shares pursuant to the Offer.  Stockholders
holding shares through brokers or banks are urged to consult the brokers or
banks to determine whether transaction costs are applicable if stockholders
tender shares through such brokers or banks and not directly to the Depositary.
AROC, however, upon request, will reimburse brokers, dealers and commercial
banks for customary mailing and handling expenses incurred by them in forwarding
the Offer and related materials to the beneficial owners of shares held by them
as a nominee or in a fiduciary capacity.  No broker, dealer, commercial bank or
trust company has been authorized to act as the agent of AROC or the Depositary
for purposes of the Offer.  AROC will pay or cause to be paid all stock transfer
taxes, if any, on its purchase of shares except as otherwise provided in
Instruction 6 in the Letter of Transmittal.

     The estimates of specific fees and expenses are:

       Financial advisor fees and expenses......................     $  35,000
       Printing and mailing.....................................        11,460
       Filing fee...............................................           500
       Depositary fees..........................................         6,000
       Counsel fees and expenses................................       150,000
       Miscellaneous............................................     $   2,000
                                                                     ---------
            Total...............................................     $ 204,960
                                                                     =========

CERTAIN LEGAL MATTERS AND REGULATORY APPROVALS

     General.  AROC is not aware of any license or other regulatory permit that
appears to be material to the business of AROC that might be adversely affected
by the acquisition of shares by AROC pursuant to the Offer or of any approval or
other action by any domestic (federal or state) or foreign governmental,
administrative or regulatory authority or agency which would be required prior
to the acquisition of shares by AROC pursuant to the Offer.  Should any such
approval or other action be required, it is our present intention to seek such
approval or action.  AROC does not currently intend, however, to delay the
purchase of shares tendered pursuant to the Offer pending the outcome of any
action or the receipt of any approval (subject to AROC's right to decline to
purchase shares if any of the conditions in "The Tender Offer--Certain
Conditions of the Offer" shall have occurred). There can be no assurance that
any approval or other action, if needed, would be obtained without substantial
conditions or that adverse consequences might not result to the business of
AROC, or that certain parts of the businesses of AROC, might not have to be
disposed of or held separate or other substantial conditions complied with in
order to obtain such approval or other action or in the event that approval was
not obtained or other action

                                       23
<PAGE>

was not taken. AROC's obligation under the Offer to accept for payment and pay
for shares is subject to certain conditions, including conditions relating to
the legal matters discussed in this section. See "The Tender Offer--Certain
Conditions of the Offer."

     State Takeover Laws.  AROC is incorporated under the laws of the State of
Delaware.  In general, Section 203 of the DGCL prevents an "interested
stockholder" (generally a person who beneficially owns or has the right to
acquire 15% or more of a corporation's outstanding voting stock, or an affiliate
or associate thereof that beneficially owned 15% or more of the outstanding
voting stock of the corporation at any time within the past three years) from
engaging in a "business combination" (defined to include mergers and certain
other transactions) with a Delaware corporation for a period of three years
following the date such person became an interested stockholder unless, among
other things, prior to the date the interested stockholder became an interested
stockholder, the board of directors of the corporation approved either the
business combination or the transaction in which the interested stockholder
became an interested stockholder.  AROC believes that the restrictions contained
in Section 203 of the DGCL applicable to a "business combination" will not apply
to the Offer or any second-step transaction, if it occurs.

     AROC conducts limited business in several states in the United States, some
of which have enacted takeover laws.  AROC does not believe that any state
takeover statutes apply to the Offer and has not currently complied with any
state takeover statute or regulation.  In the event it is asserted that one or
more state takeover laws is applicable to the Offer or any second-step
transaction, and an appropriate court does not determine that it is inapplicable
or invalid as applied to the Offer or a second-step transaction, AROC may be
required to file certain information with, or receive approvals from, the
relevant state authorities.  In addition, if enjoined, AROC may be unable to
accept for payment any shares tendered pursuant to the Offer or be delayed in
continuing or  consummating the Offer and any second-step transaction.  In such
case, AROC may not be obligated to accept for payment any shares tendered.  See
"The Tender Offer--Certain Conditions of the Offer."

     Litigation.  To the best knowledge of AROC, no lawsuits have been filed
relating to the Offer or any possible second-step transaction.

                                       24
<PAGE>

                                 THE COMPANY

BACKGROUND AND BUSINESS

     AROC is a Tulsa-based holding company of a group whose principal activities
are the exploration, development and production of oil and gas and the
acquisition of producing oil and gas properties.  AROC (formerly known as
American Rivers Oil Company) was incorporated and registered under the laws of
Delaware on July 16, 1999.  AROC's corporate headquarters are at 4200 East
Skelly Drive, Suite 1000, Tulsa, Oklahoma 74135 and its telephone number is
(918) 491-1100.

     AROC's majority stockholder, MPAC Energy, LLC, is a limited liability
company organized under the laws of the state of Texas.  MPAC's principal
business address and office is located at 13101 Northwest Freeway, Suite 320,
Houston, Texas 77040.  The principal business of MPAC is engaging in oil and gas
related investments.  The controlling members of MPAC are EnCap Equity 1996
Limited Partnership ("EnCap 96 LP"), a Texas limited partnership, EnCap Equity
1994 Limited Partnership ("EnCap 94 LP"), a Texas limited partnership, Energy
Capital Investment Company, PLC ("Energy PLC"), a company organized and existing
under the laws of England, EF-II Holdings, L.L.C. ("EF-II"), a Texas limited
liability company, EnCap Investments L.L.C. ("EnCap Investments"), a Delaware
limited liability company, and El Paso Capital Investments, L.L.C. ("El Paso
Capital"), a Delaware limited liability company.  The sole general partner of
EnCap 96 LP and EnCap 94 LP is EnCap Investments.  The members of EF-II holdings
are EnCap 96 LP and Energy PLC.  The sole member of EnCap Investments and El
Paso Capital is El Paso Merchant Energy Holding Company ("El Paso Merchant
Energy"), a Delaware corporation.  The controlling person of El Paso Merchant
Energy is El Paso Corporation.

OFFICERS AND DIRECTORS

     For biographical information on AROC's executive officers and directors,
see "Item 10.  Directors and Executive Officers of the Registrant" in AROC's
Annual Report on Form 10-K for the year ended December 31, 2000, a copy of which
is being sent to stockholders along with this Offer to Purchase.  Certain
information regarding the officers and directors of MPAC and its control persons
is set forth in Appendix B attached to this Offer to Purchase.

     None of the executive officers or directors of AROC has, during the last
five years, been convicted in a criminal proceeding (excluding traffic
violations or similar misdemeanors) or has been a party to a civil proceeding
which resulted in a judgment, decree or final order enjoining further violations
of, or prohibiting activities subject to, federal or state securities laws or
finding any violation of such laws.  All of the executive officers and directors
of AROC are citizens of the United States, with the exception of Paul R.
Fenemore who is a citizen of the United Kingdom.

     None of MPAC, Energy PLC, EnCap 96 LP, EnCap 94 LP, EnCap Investments, El
Paso Capital, EF-II Holdings, El Paso Corporation, El Paso Merchant Energy, or
any of the individuals identified in Appendix B has, during the last five years,
been convicted in a criminal proceeding (excluding traffic violations or similar
misdemeanors).  None of MPAC, Energy PLC, EnCap 96 LP, EnCap 94 LP, EnCap
Investments, El Paso Capital, EF-II Holdings, El Paso Corporation, El Paso
Merchant Energy, or any of the individuals identified in this Schedule 1 has,
during the last five years, been a party to a civil proceeding of a judicial or
administrative body of competent jurisdiction and a result of such proceeding
was or is subject to a judgment, decree or final order enjoining future
violations of, or prohibiting or mandating activities subject to, federal or
state securities laws or finding any violation with respect to such laws.

     Each of the individuals identified in Appendix B is a citizen of the United
States of America, with the exception of (i) Alan B. Henderson and William W.
Vanderfelt who are citizens of the United Kingdom, (ii) Energy PLC which was
formed under the laws of the United Kingdom, (iii) Leo G. Deschuyteneer who is a
citizen of Belguim, (iv) James F. Ladner who is a citizen of Switzerland, and
(v) Juan Carlos Braniff who is a citizen of Mexico.

                                       25
<PAGE>

BENEFICIAL OWNERSHIP OF CERTAIN STOCKHOLDERS

     The following table sets forth certain information, as of May 1, 2001,
about any person that is known to AROC to be the beneficial owner of more than
5% of each class of AROC common stock and each executive officer and director of
AROC and all executive officers and directors of AROC as a group.  Except as
otherwise indicated, each of the persons named below is believed by AROC to
possess sole voting and investment power with respect to the shares beneficially
owned by such person.

<TABLE>
<CAPTION>

Name and Address of Beneficial Owner (1)       Shares Owned Beneficially (2)             Percent (2)
-----------------------------------------    -------------------------------------    -----------
<S>                                       <C>                             <C>
John A. Keenan (3)                                     2,000,000                          3.6%
-------------------------------------------------------------------------------------------------

Paul R. Fenemore (4)                                   1,400,000                          2.5%
-------------------------------------------------------------------------------------------------

Francis M. Munchinski (5)                              1,000,000                          1.8%
-------------------------------------------------------------------------------------------------

Robert E. Schulte (6)                                    750,000                          1.4%
-------------------------------------------------------------------------------------------------

Michael E. Humphries                                     250,000                           *
-------------------------------------------------------------------------------------------------

Robert L. Zorich (7)                                        -0-                            -
-------------------------------------------------------------------------------------------------

Gary R. Petersen (7)                                        -0-                            -
-------------------------------------------------------------------------------------------------

D. Martin Phillips (7)                                      -0-                            -
-------------------------------------------------------------------------------------------------

MPAC Energy, LLC (8)                                 820,422,217                         95.6%
-------------------------------------------------------------------------------------------------

All directors and executive                            5,400,000                           *
 officers of AROC as a group (8
 persons) (3), (4), (5), (6), (7)
-------------------------------------------------------------------------------------------------
</TABLE>
_________________
<TABLE>
<CAPTION>
*      Less than 1%
<S>    <C>
</TABLE>
(1)  All of AROC's directors and executive officers may be contacted at 4200
     East Skelly Drive, Suite 1000, Tulsa, Oklahoma 74135.

(2)  All share amount and percentage information is calculated on the basis that
     AROC's common stock and Series A convertible preferred stock constitute a
     single class because as of each share of preferred stock is convertible at
     any time into 423.7 shares of AROC's common stock and generally has the
     right to vote in all matters on the same basis as if the preferred stock
     had been converted into common stock.

(3)  Includes 1,900,000 shares granted as restricted stock under AROC's 2000
     Omnibus Stock and Incentive Plan.

(4)  Consists of 1,400,000 shares granted as restricted stock under AROC's 2000
     Omnibus Stock and Incentive Plan.

(5)  Consists of 1,000,000 shares granted as restricted stock under AROC's 2000
     Omnibus Stock and Incentive Plan.

(6)  Consists of 750,000 shares granted as restricted stock under AROC's 2000
     Omnibus Stock and Incentive Plan.

(7)  Excludes stock owned by MPAC, with which this person is affiliated.

(8)  Consists of 17,045,454 shares of common stock, 10,000,000 shares of
     convertible restricted voting shares that are convertible into 5,000,000
     shares of common stock, warrants to purchase 44,009,814 shares of common
     stock at a price of $0.01 per share that are exercisable, and 1,780,306
     shares of preferred stock that are convertible into 754,366,949 shares of
     common stock.  The address of MPAC Energy, LLC is 13101 Northwest Freeway,
     Suite 320, Houston, Texas 77040.

     In addition to the interests set out above, John A. Keenan is interested in
45,000 shares of common stock held in the name of Diamond Securities Limited and
102,500 shares of common stock held in the name of Havensworth Limited by virtue
of having proxy over the voting rights attached to these shares of common stock

                                       26
<PAGE>

pending their sale, as required by a settlement of legal proceedings with the
former Managing Director of Alliance in August 1996.

ADDITIONAL INFORMATION ABOUT AROC IN FORM 10-K

     Additional information concerning AROC, including its business, properties,
management's discussion and analysis of financial condition and the results of
operations, and financial statements and the notes thereto, is included in its
Annual Report on Form 10-K for the year ended December 31, 2000, a copy of which
is being sent to stockholders along with this Offer to Purchase.

                                       27
<PAGE>

                                 AVAILABLE INFORMATION

     AROC is subject to the informational requirements of the Exchange Act, and
in accordance with such requirements files reports, proxy statements, and other
information with the SEC.  The reports, proxy statements, and other information
filed with the SEC can be inspected and copied at the public reference
facilities maintained by the SEC at 450 Fifth Street, N.W., Judiciary Plaza,
Washington, D.C. 20549 and at the following Regional Offices of the SEC: 500
West Madison Street, Suite 1400, Chicago, Illinois 60661 and 7 World Trade
Center, Suite 1300, New York, New York 10048.  Copies of such material can be
obtained at prescribed rates from the Public Reference Section of the SEC at 450
Fifth Street, N.W., Judiciary Plaza, Washington, D.C. 20459.  The SEC maintains
a World Wide Web site on the Internet at http://www.sec.gov that contains
reports, proxy and information statements and other information regarding
registrants that file electronically with the SEC, including AROC.

     AROC and MPAC have filed a Schedule TO with the SEC with respect to the
Offer.  As permitted by the rules and regulations of the SEC, this Offer to
Purchase omits certain information and exhibits contained in the Schedule TO.
The Schedule TO (including exhibits) and any amendments thereto may be inspected
and copied at, or obtained from the SEC's offices as set forth above.  For
further information, reference is hereby made to the Schedule TO and the
exhibits thereto.  Statements contained in this Offer to Purchase concerning
documents filed with the SEC as exhibits to the Schedule TO or attached as
Appendices to this Offer to Purchase are not necessarily complete and, in each
instance, reference is made to the copy of the document filed as an exhibit to
the Schedule TO or attached as an Appendix to this Offer to Purchase.  Each
statement in this Offer to Purchase concerning such a document is qualified in
its entirety by reference to such document.

     Certain documents discussed in this Offer to Purchase including, without
limitation, the Schedule TO and all exhibits thereto, are also available for
inspection and copying at the principal executive offices of AROC at 4200 East
Skelly Drive, Suite 1000, Tulsa, Oklahoma 74135, telephone (918) 491-1100,
during its regular business hours, by any stockholder or his or her
representative so designated in writing.  Upon the written request of a
stockholder directed to the Secretary of AROC at the above address, AROC will
mail to such stockholder a copy of any such document at the expense of such
stockholder.  Additional copies of this Offer to Purchase, the Letter of
Transmittal and the Notice of Guaranteed Delivery may also be obtained by
stockholders from AROC at its address and telephone number set forth above at no
cost to the stockholders.

     Once the Offer is completed, AROC may deregister its common stock and, if
it does, it will no longer be subject to the reporting requirements of the
Exchange Act.  See "Special Factors--Effects of the Offer."

     No person has been authorized to give any information or make any
representation in connection with the Offer made hereby other than those
contained or incorporated by reference in this Offer to Purchase, and, if given
or made, such information or representation must not be relied upon as having
been authorized by AROC.  The delivery of this Offer to Purchase shall not,
under any circumstances, create any implication that there has been no change in
our affairs since the date hereof or that the information contained or
incorporated by reference herein is correct as of any time subsequent to its
date.  Information in this Offer to Purchase about AROC has been provided by
AROC.

                                       28
<PAGE>

                                                            APPENDIX A
                             Randall & Dewey, Inc.
                       Two Greenspoint Park, Suite 380-S
                         16800 Greenspoint Park Drive
                             Houston, Texas 77060
                                (281) 774-2000

April 16, 2001

Mr. Michael E. Humphries
Chairman of the Special Committee
of the Board of Directors
AROC Inc.
4200 E. Skelly Drive, Suite 1000
Tulsa, OK  74135

Members of the Committee:

You have requested our opinion as to the fairness, from a financial point of
view, to the existing non-affiliated holders of common stock ("Shareholders"),
par value $0.001 per share ("Common Stock") of AROC Inc. ("the Company"), of the
consideration to be received as set forth in the Offer to Purchase from AROC
Inc.  Pursuant to the Offer to Purchase, the Company will commence a tender
offer (the "Offer") to purchase all of the outstanding shares of Common Stock at
a price per share of $0.06/share in cash.

In arriving at our opinion, we have, among other things: 1) reviewed a draft of
the Offer to Purchase (the "Offer to Purchase") to be included in a Schedule TO
to be filed by the Company with the Securities and Exchange Commission; 2)
reviewed certain publicly available business and financial information relating
to the Company, including the Annual Reports on Form 10-K and related audited
financial statements for the fiscal years ending April 30, 2000 and December 31,
2000; 3) reviewed certain estimates of the Company's proved oil and gas reserves
prepared by Lee Keeling & Associates Inc. ("Lee Keeling"); 4) reviewed pro-forma
first quarter 2001 financial statements and operating reports reflective of the
remaining assets net of asset sales concluded in the first quarter 2001; 5)
reviewed internal AROC Inc. operating and project performance summaries; and 6)
reviewed such other financial studies and analyses and took into account such
other matters as we have deemed necessary or appropriate.  This opinion is for
the use and benefit of the Special Committee of the Board of Directors of the
Company and does not constitute a recommendation to any holder of the Company
Common Stock as to whether such holder should tender any shares pursuant to the
Offer.  As you are aware, we have acted as financial advisor to the Special
Committee of the Board of Directors, and we will receive a fee from the Company
for such services.  In addition, the Company has agreed to indemnify us for
certain liabilities arising out of our engagement.

                                      A-1
<PAGE>

Mr. Michael E. Humphries
Chairman of the Special Committee
April 16, 2001/page 2

Our opinion is rendered on the basis of conditions in the oil and gas markets
and the securities markets prevailing as of the date hereof and the conditions
and prospects, financial or otherwise, of the Company as they have been
represented to us as of the date hereof or as they were reflected in the
materials and discussions described above.  It is our opinion that, as of the
date hereof, the Offer Price of $0.06 per share is fair from a financial point
of view to the non-affiliated holders of the Company Common Stock.

Very truly yours,

/s/ Gregg Jacobson
-----------------------
Gregg Jacobson
Randall & Dewey, Inc.

GAJ/lph
Attachment

                                      A-2
<PAGE>

                                                            APPENDIX B

                        DIRECTORS, EXECUTIVE OFFICERS,
                            OR CONTROLLING PERSONS
                              OF MPAC ENERGY, LLC

     The name, business address, present principal occupation or employment and
the name, principal business address of any corporation or other organization in
which such employment is conducted, of each of (i) the members of the board of
managers of MPAC Energy, LLC, (ii) the executive officers and directors of
Energy Capital Investment Company, PLC, (iii) the executive officers of EnCap
Investments L.L.C.,  (iv) the directors and executive officers of El Paso
Capital Investments, L.L.C., (v) the directors and executive officers of El Paso
Merchant Energy Holding Company, and (vi) the directors and executive officers
of El Paso Corporation, are set forth below:

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
MPAC ENERGY, LLC

D. Martin Phillips            Manager,               Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana St.            MPAC Energy, LLC       EnCap Investments         1100 Louisiana St.
Suite 3150                                           L.L.C.                    Suite 3150
Houston, Texas 77002                                                           Houston, Texas 77002

Gary R. Petersen              Manager,               Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana St.            MPAC Energy, LLC       EnCap Investments         1100 Louisiana St.
Suite 3150                                           L.L.C.                    Suite 3150
Houston, Texas 77002                                                           Houston, Texas 77002

Robert L. Zorich              President and          Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana St.            Manager                EnCap Investments         1100 Louisiana
Suite 3150                    MPAC Energy, LLC       L.L.C.                    Suite 3150
Houston, Texas 77002                                                           Houston, Texas 77002

Robert Swanson                Vice President,        Vice President,           MPAC Energy, LLC
13101 Northwest Fwy           Secretary and          Secretary and Treasurer   13101 Northwest Fwy
Suite 320                     Treasurer              MPAC Energy, LLC          Suite 320
Houston, Texas 77040          MPAC Energy, LLC                                 Houston, Texas 77040

ENERGY CAPITAL INVESTMENT
COMPANY, PLC

Leo G. Deschuyteneer          Director of Energy     Executive Director        Sofina SA
38 Rue de Naples              Capital Investment     of Sofina SA              38 Rue de Naples
B-1050                        Company PLC                                      B-1050
Brussels, Belgium                                                              Brussels, Belgium

Alan B. Henderson             Director of Energy     Chairman of Ranger        Ranger Oil (UK) Ltd.
Ranger House                  Capital Investment     Oil (UK) Ltd.             Ranger House
Walnut Tree Close             Company PLC                                      Walnut Tree Close
Guildford, Surrey                                                              Guildford, Surrey
GU1 4HS                                                                        GU1 4HS

James F. Ladner               Director of Energy     Executive Director        RP & C International
Gartenstrasse 10              Capital Investment     of RP & C                 Gartenstrasse 10
CH-8002                       Company PLC            International             CH-8002
Zurich, Switzerland                                                            Zurich, Switzerland
</TABLE>

                                      B-1
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
Gary R. Petersen              Director               Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana                Energy Capital         EnCap Investments         1100 Louisiana
Suite 3150                    Investment Company     L.L.C.                    Suite 3150
Houston, Texas 77002          PLC                                              Houston, Texas 77002

William M. Vanderfelt         Director               Managing Partner of       Petercam S.A.
19 Place Sainte-Gudule        Energy Capital         Petercam S.A.             19 Place Sainte-Gudule
B-1000                        Investment Company                               B-1000
Brussels, Belgium             PLC                                              Brussels, Belgium

ENCAP INVESTMENTS L.L.C.

David B. Miller               Senior Vice            Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana                President              EnCap Investments         1100 Louisiana
Suite 3150                    EnCap Investments      L.L.C.                    Suite 3150
Houston, Texas 77002          L.L.C.                                           Houston, Texas 77002

Gary R. Petersen              Senior Vice            Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana                President              EnCap Investments         1100 Louisiana
Suite 3150                    EnCap Investments      L.L.C.                    Suite 3150
Houston, Texas 77002          L.L.C.                                           Houston, Texas 77002

D. Martin Phillips            Senior Vice            Senior Vice President     EnCap Investments L.L.C.
1100 Louisiana St.            President              EnCap Investments         1100 Louisiana
Suite 3150                    EnCap Investments      L.L.C.                    Suite 3150
Houston, Texas 77002          L.L.C.                                           Houston, Texas 77002

Robert L. Zorich              Senior Vice            Senior Vice President     EnCap Investments L.L.C.
3811 Turtle Creek Blvd.       President              EnCap Investments         3811 Turtle Creek Blvd.
Suite 1080                    EnCap Investments      L.L.C.                    Suite 1080
Dallas, Texas 75219           L.L.C.                                           Dallas, Texas 75219

EL PASO CAPITAL
 INVESTMENTS, L.L.C.

Ralph Eads                    Chief Executive        Chief Executive           El Paso Merchant Energy
1001 Louisiana Street         Officer                Officer of El Paso        Holding Corporation
Houston, Texas 77002                                 Merchant Energy           1001 Louisiana Street
                                                     Holding Company           Houston, Texas 77002

Clark C. Smith                President              President of El Paso      El Paso Merchant Energy
1001 Louisiana Street                                Merchant Energy           Holding Corporation
Houston, Texas 77002                                 Holding Company           1001 Louisiana Street
                                                                               Houston, Texas 77002

John B. Holmes                Chief Operating        Chief Operating           El Paso Merchant Energy
1001 Louisiana Street         Officer                Officer of El Paso        Holding Corporation
Houston, Texas 77002                                 Merchant Energy           1001 Louisiana Street
                                                     Holding Company           Houston, Texas 77002
</TABLE>

                                      B-2
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>

John L. Harrison              Senior Vice            Senior Vice President     El Paso Merchant Energy
1001 Louisiana Street         President and Chief    and Chief Financial       Holding Corporation
Houston, Texas 77002          Financial Officer      Officer of El Paso        1001 Louisiana Street
                                                     Merchant Energy           Houston, Texas 77002
                                                     Holding Company

Larry M. Kellerman            Vice President and     Vice President and        El Paso Merchant Energy
1001 Louisiana Street         Senior Managing        Senior Managing           Holding Corporation
Houston, Texas 77002          Director               Director of El Paso       1001 Louisiana Street
                                                     Merchant Energy           Houston, Texas 77002
                                                     Holding Company

Cecilia T. Heilmann           Vice President,        Vice President,           El Paso Merchant Energy
1001 Louisiana Street         Managing Director,     Managing Director, and    Holding Corporation
Houston, Texas 77002          and Controller         Controller of El Paso     1001 Louisiana Street
                                                     Merchant Energy           Houston, Texas 77002
                                                     Holding Company

Grady M. Blakley              Senior Vice            Senior Vice President     El Paso Merchant Energy
1001 Louisiana Street         President              of El Paso Merchant       Holding Corporation
Houston, Texas 77002                                 Energy Holding Company    1001 Louisiana Street
                                                                               Houston, Texas 77002

J. Robert Collins, Jr.        Senior Vice            Senior Vice President     El Paso Merchant Energy
1001 Louisiana Street         President              of El Paso Merchant       Holding Corporation
Houston, Texas 77002                                 Energy Holding Company    1001 Louisiana Street
                                                                               Houston, Texas 77002

W.C. Mack                     Senior Vice            Senior Vice President     El Paso Merchant Energy
1001 Louisiana Street         President              of El Paso Merchant       Holding Corporation
Houston, Texas 77002                                 Energy Holding Company    1001 Louisiana Street
                                                                               Houston, Texas 77002

EL PASO MERCHANT ENERGY
 HOLDING COMPANY

Ralph Eads                    Chief Executive        Chief Executive           El Paso Merchant Energy
1001 Louisiana Street         Officer Merchant       Officer, Merchant         Holding Corporation
Houston, Texas 77002          Energy Group and       Energy Group and          1001 Louisiana St.
                              Director               Merchant Energy North     Houston, Texas 77002
                                                     America

Clark C. Smith                President,             President, Merchant       El Paso Merchant Energy
1001 Louisiana Street         Merchant Energy        Energy North America      Holding Corporation
Houston, Texas 77002          North America and                                1001 Louisiana St.
                              Director                                         Houston, Texas 77002

John B. Holmes                Chief Operating        Chief Operating           El Paso Merchant Energy
1001 Louisiana Street         Officer Merchant       Officer, Merchant         Holding Corporation
Houston, Texas 77002          Energy North America   Energy North America      1001 Louisiana St.
                                                                                Houston, Texas 77002
</TABLE>

                                      B-3
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
Timothy D. Bourn              Vice President and     Vice President and        El Paso Merchant Energy
1001 Louisiana Street         Senior Managing        Senior Managing           Holding Corporation
Houston, Texas 77002          Director               Director, Merchant        1001 Louisiana St.
                                                     Energy North America      Houston, Texas 77002

Larry M. Kellerman            Vice President and     Vice President and        El Paso Merchant Energy
1001 Louisiana Street         Senior Managing        Senior Managing           Holding Corporation
Houston, Texas 77002          Director               Director, Merchant        1001 Louisiana St.
                                                     Energy North America      Houston, Texas 77002

John L. Harrison              Senior Vice            Senior Vice President     El Paso Merchant Energy
1001 Louisiana Street         President and Chief    and Chief Financial       Holding Corporation
Houston, Texas 77002          Financial Officer      Officer, Merchant         1001 Louisiana St.
                                                     Energy  North America     Houston, Texas 77002

W.C. Mack                     Senior Vice            Senior Vice President,    El Paso Merchant Energy
1001 Louisiana Street         President              Merchant Energy North     Holding Corporation
Houston, Texas 77002                                 America                   1001 Louisiana St.
                                                                               Houston, Texas 77002

Grady M. Blakley              Senior Vice            Senior Vice President,    El Paso Merchant Energy
1001 Louisiana Street         President              Merchant Energy North     Holding Corporation
Houston, Texas 77002                                 America                   1001 Louisiana St.
                                                                               Houston, Texas 77002

J. Robert Collins, Jr.        Senior Vice            Senior Vice President,    El Paso Merchant Energy
1001 Louisiana Street         President              Merchant Energy North     Holding Corporation
Houston, Texas 77002                                 America                   1001 Louisiana St.
                                                                               Houston, Texas 77002

EL PASO CORPORATION

William A. Wise               Chairman of the        Chairman of the Board,    El Paso Corporation
1001 Louisiana Street         Board, President,      President, Chief          1001 Louisiana Street
Houston, Texas 77002          Chief Executive        Executive Officer and     Houston, Texas 77002
                              Officer and Director   Director of El Paso
                                                     Corporation

H. Brent Austin               Executive Vice         Executive Vice            El Paso Corporation
1001 Louisiana Street         President and Chief    President and Chief       1001 Louisiana Street
Houston, Texas 77002          Financial Officer      Financial Officer of      Houston, Texas 77002
                                                     El Paso Corporation

Ralph Eads                    Executive Vice         Executive Vice            El Paso Corporation
1001 Louisiana Street         President              President of El Paso      1001 Louisiana Street
Houston, Texas 77002                                 Corporation               Houston, Texas 77002

Joel Richards III             Executive Vice         Executive Vice            El Paso Corporation
1001 Louisiana Street         President              President, Human          1001 Louisiana Street
Houston, Texas 77002                                 Resources and             Houston, Texas 77002
                                                     Administration of El
                                                     Paso Corporation

</TABLE>

                                      B-4
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
William A. Smith              Executive Vice         Executive Vice            El Paso Corporation
1001 Louisiana Street         President              President, Business       1001 Louisiana Street
Houston, Texas 77002                                 Development  of El        Houston, Texas 77002
                                                     Paso Corporation

John W. Somerhalder II        President, Pipeline    President, Pipeline       El Paso Corporation
1001 Louisiana Street         Group                  Group of El Paso          1001 Louisiana Street
Houston, Texas 77002                                 Corporation               Houston, Texas 77002

Britton White, Jr.            Executive Vice         Executive Vice            El Paso Corporation
1001 Louisiana Street         President and          President and General     1001 Louisiana Street
Houston, Texas 77002          General Counsel        Counsel of El Paso        Houston, Texas 77002
                                                     Corporation

Jeffrey I. Beason             Senior Vice            Senior Vice President     El Paso Corporation
1001 Louisiana Street         President and          and Controller of El      1001 Louisiana Street
Houston, Texas 77002          Controller             Paso Corporation          Houston, Texas 77002

C. Dana Rice                  Senior Vice            Senior Vice President     El Paso Corporation
1001 Louisiana Street         President and          and Treasurer of El       1001 Louisiana Street
Houston, Texas 77002          Treasurer              Paso Corporation          Houston, Texas 77002

Patricia A. Shelton           President, Western     President, Western        El Paso Natural Gas Company
1001 Louisiana Street         Pipeline Division      Pipeline Division         1001 Louisiana Street
Houston, Texas 77002                                                           Houston, Texas 77002

E.J. Holm                     Chief Executive        Chief Executive           El Paso Natural Gas Company
1001 Louisiana Street         Officer, Eastern       Officer, Eastern          1001 Louisiana Street
Houston, Texas 77002          Pipeline Division      Division                  Houston, Texas 77002

John D. Hushon                Chief Executive        Chief Executive           El Paso Energy
1001 Louisiana Street         Officer, El Paso       Officer, El Paso Europe   International Company
Houston, Texas 77002          Europe                                           1001 Louisiana Street
                                                                               Houston, Texas 77002

Greg G. Jenkins               President of El        President of El Paso      El Paso Global Networks
1001 Louisiana Street         Paso Global            Global Networks Company   Company
Houston, Texas 77002          Networks Company                                 1001 Louisiana Street
                                                                               Houston, Texas 77002

Robert G. Phillips            President of El        President of El Paso      El Paso Field Services, L.P.
1001 Louisiana Street         Paso Field             Services, L.P.            1001 Louisiana Street
Houston, Texas 77002          Services, L.P.                                   Houston, Texas 77002

James C. Yardley              President, Southern    President, Southern       Southern Natural Gas Company
1001 Louisiana Street         Natural Gas Company    Natural Gas Company       1001 Louisiana Street
Houston, Texas 77002                                                           Houston, Texas 77002

John B. Holmes, Jr.           Chief Operating        Chief Operating           El Paso Merchant Energy
1001 Louisiana Street         Officer, Merchant      Officer of Merchant       Holding Company
Houston, Texas 77002          Energy Group           Energy Group              1001 Louisiana Street
                                                                               Houston, Texas 77002
</TABLE>

                                      B-5
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
Stephen C. Beasley            President,             President, Tennessee      Tennessee Gas Pipeline
1001 Louisiana Street         Tennessee Gas          Gas Pipeline Company      Company
Houston, Texas 77002          Pipeline Company                                 1001 Louisiana Street
                                                                               Houston, Texas 77002

James J. Cleary               President, ANR         President of ANR          ANR Pipeline Company
1001 Louisiana Street         Pipeline Company       Pipeline Company          1001 Louisiana Street
Houston, Texas 77002                                                           Houston, Texas 77002

Byron Kelly                   President, El Paso     President, El Paso        El Paso Energy
1001 Louisiana Street         Energy International   International Company     International Company
Houston, Texas 77002                                                           1001 Louisiana Street
                                                                               Houston, Texas 77002

Tom Wade                      President, Merchant    President, Merchant       Coastal States Crude
1001 Louisiana Street         Energy Petroleum       Energy Petroleum          Gathering Company
Houston, Texas 77002          Markets                Markets                   1001 Louisiana Street
                                                                               Houston, Texas 77002

Rod Erskine                   President, El Paso     President of El Paso      El Paso Production Company
1001 Louisiana Street         Production             Production Company        1001 Louisiana Street
Houston, Texas 77002                                                           Houston, Texas 77002

Byron Allumbaugh              Director               Retired Chairman,         610 Newport Center Drive
610 Newport Center                                   Ralphs Grocery Company    Suite 210
Drive, Suite 210                                                               Newport Beach, CA 92660
Newport Beach, CA 92660

David A. Arledge              Non-Executive Vice     Non-Executive Vice        El Paso Corporation
1001 Louisiana Street         Chairman of the        Chairman of the Board     1001 Louisiana Street
Houston, Texas 77002          Board                  of El Paso Corporation    Houston, Texas 77002

John M. Bissell               Director               Chairman of the Board     Bissell Inc.
2345 Walker Ave., N.W.                               of Bissell Inc.           2345 Walker Ave., N.W.
Grand Rapids, MI 49501                                                         Grand Rapids, MI 49501

Juan Carlos Braniff           Director               Director, Grupo           Universidad 1200, Col. XOCO
Universidad 1200, Col.                               Financiero Bancomer       Mexico, D.F.C.P. 03339
XOCO
Mexico, D.F.C.P. 03339

James F. Gibbons              Director               Professor at Stanford     Stanford University
Stanford University                                  University School of      Paul G. Allen Center for
Paul G. Allen Center for                             Engineering               Integrated Systems
 Integrated Systems                                                            Room 201 (Mail Stop 4075)
Room 201 (Mail Stop 4075)                                                      Stanford, CA 94305
Stanford, CA 94305

Anthony W. Hall, Jr.          Director               City Attorney, City of    Attorney, City of Houston
P.O. Box 1562                                        Houston                   P.O. Box 1562
Houston, Texas 77025                                                           Houston, Texas 77251

</TABLE>

                                      B-6
<PAGE>

<TABLE>
<CAPTION>

         NAME AND              CAPACITY IN WHICH      PRINCIPAL OCCUPATION       NAME, PRINCIPAL BUSINESS
     BUSINESS ADDRESS                SERVES                                     ADDRESS OF ORGANIZATION IN
                                                                                WHICH PRINCIPAL OCCUPATION
                                                                                       IS CONDUCTED
<S>                           <C>                    <C>                       <C>
Ronald L. Kuehn, Jr.          Director               Business Consultant       El Paso Corporation
1001 Louisiana Street                                                          1001 Louisiana Street
Houston, Texas 77002                                                           Houston, Texas 77002

J. Carleton MacNeil, Jr.      Director               Securities Consultant     7020 Port Washington Road,
7020 Port Washington Road,                                                     Suite 200
 Suite 200                                                                     Milwaukee, WI 53217
Milwaukee, WI 53217

Thomas R. McDade              Director               Senior Partner,           McDade, Fogler, Marnes,
Two Houston Center                                   McDade, Fogler,           L.L.P.
909 Fannin, Suite 1200                               Marnes, L.L.P.            Two Houston Center
Houston, Texas 77010                                                           909 Fannin, Suite 1200
                                                                               Houston, Texas 77010

Malcolm Wallop                Director               Chairman, Western         Western Strategy Group
Western Strategy Group                               Strategy Group            1001 Wilson Blvd.,
1100 Wilson Blvd.,                                                             Suite 1400
Suite 1400                                                                     Arlington, VA 22209
Arlington, VA 22209

Joe B. Wyatt                  Director               Chancellor Emeritus,      Vanderbilt University
Vanderbilt University                                Vanderbilt University     211 Kirkland Mall
211 Kirkland Mall                                                              Nashville, TN 37240
Nashville, TN 37240

</TABLE>

                                      B-7
<PAGE>

     Facsimile copies of the Letter of Transmittal, properly completed and duly
executed, will be accepted. The Letter of Transmittal, certificates for shares
of AROC common stock and any other required documents should be sent or
delivered by each stockholder or his broker, dealer, commercial bank, trust
company or other nominee to the Depositary as follows:

                       The Depositary for the Offer is:

                         REGISTRAR & TRANSFER COMPANY

                               Delivery Address:

       By Hand Delivery,                      By Facsimile:
Overnight Courier or Mail:

 Registrar and Transfer Company               (908) 497-2311
Attn: Reorganization Department
       10 Commerce Drive
      Cranford, NJ  07016
         (800) 368-5948

     Additional copies of this Offer to Purchase, the Letter of Transmittal and
the Notice of Guaranteed Delivery may be obtained from the Depositary.  Any
questions and requests for assistance may be directed to Investor Relations at
the telephone number and address listed below.  You may also contact your
broker, dealer, commercial bank or trust company for assistance concerning the
Offer.

                                    [Logo]

                                   AROC INC.
                              Investor Relations
                      4200 East Skelly Drive, Suite 1000,
                             Tulsa, Oklahoma 74135
                                (918) 491-1100

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