<PAGE>

                                                                     EXHIBIT 4.1

                             DATED APRIL 30, 2000
                             --------------------



                                   AROC INC.



                       ________________________________

                               WARRANT AGREEMENT

                          relating to the issuance of
                             Series J Warrants of
                                   AROC Inc.
                        _______________________________
<PAGE>

     THIS WARRANT AGREEMENT (the "Agreement") is entered into as of April 30,
2000 among AROC Inc., a Delaware corporation ("the Company") and those persons
identified on the signature page of this Agreement as Warrant Holders (the
"Warrant Holders").

                                   Recitals

     The Warrant Holders have concurrently with this Warrant Agreement, entered
into a Purchase Agreement (the "Subordinated Debt Purchase Agreement") by and
between the Company and the Warrant Holders providing for the Warrant Holders to
purchase from the Company the Company's 12% Subordinated Notes due 2007 and
warrants to purchase the Company's Common Stock.

     One of the conditions to the completion of the Subordinated Debt Purchase
Agreement is that the Company shall enter into this Warrant Agreement.

     Now, therefore, in consideration of the premises and the mutual agreements
of the parties, the parties to this Agreement hereby agree as follows:

                                   Agreement

I.   INTERPRETATION

     In this Warrant Agreement, unless the context otherwise requires, the
     expressions defined in the particulars of Warrants set out in the Schedule
     hereto shall have the meanings thereby given.

II.  WARRANTS

     A.  The Warrants shall be constituted as 39,541,233 Series "J" Warrants
         entitling the holders to subscribe for shares of the common stock,
         $0.001 par value per share (the "Common Stock") of the Company at a
         fixed price of $0.01 per share (subject to the provisions of the
         Schedule hereto) at any time prior to 5:00 p.m. (Tulsa, Oklahoma time)
         on April 30, 2007, the final date for exercise of a Warrant being the
         "Expiration Date" and the price payable upon exercise of a Warrant
         being the "Subscription Price".

     B.  Each of the Warrant Holders represents and agrees as follows:

         (i)    It has the requisite power and authority to enter into and
     perform this Agreement and this Agreement and any other documents executed
     by it in connection with this Agreement will, when executed, constitute
     binding obligations of the Warrant Holder enforceable in accordance with
     their respective terms.

         (ii)   It is an "accredited investor" as that term is defined in the
     Securities Act of 1933, as amended, and is acquiring the Warrants for its
     own account, and has received all information it believes necessary to
     evaluate its investment in the Warrants.

                                       2
<PAGE>

          (iii) Each of the Warrant Holders hereby acknowledges and confirms
     that the Warrants and the Common Stock, whether issued or arising as a
     consequence of exercise of the Warrants will be "restricted securities"
     under the United States Securities Act of 1933 (as amended) and that the
     ability to resell such Warrants and such Common Stock will therefore be
     limited.

     C.  The Company represents and agrees as follows:

         (i)    The representations and warranties made by it in Subordinated
     Debt Purchase Agreement are true and correct.

         (ii)   The execution and performance of this Agreement by it has been
     duly and validly authorized by its board of directors, and, subject to the
     Charter Amendment, no other corporate action is necessary to authorize the
     execution, delivery and performance of this Agreement by it. Subject to the
     Charter Amendment, it has full, absolute and unrestricted right, power and
     authority to execute and perform this Agreement and to carry out the
     transactions contemplated hereby. This Agreement has been duly and validly
     executed by it and this Agreement and any other documents executed by it in
     connection with this Agreement is constitute valid and binding obligations
     of it, enforceable in accordance with their respective terms.

III. CERTIFICATES

     Every Warrant Holder shall be entitled to receive one certificate for each
     Series of the Warrant(s) held by him but joint holders shall be entitled to
     only one certificate in respect of the Warrants held jointly by them which
     certificates shall be delivered to the joint holder whose name stands first
     in the Register. The Company shall comply with the terms and conditions of
     the Schedule hereto and the Warrants shall be held subject to such terms
     and conditions all of which terms shall be deemed to be incorporated in
     this Warrant Agreement and shall be binding on the Company and the Warrant
     Holders and all persons claiming through or under them respectively.

IV.  APPOINTMENT OF WARRANT AGENT

     The Company may in its absolute discretion by resolution of its Board of
     Directors appoint as agent of the Company such person or persons as it
     thinks fit to act in connection with the issue, registration, transfer and
     exchange or otherwise of warrants (the "Warrant Agent"). The Company agrees
     that the Warrant Agent shall perform the duties and obligations required of
     it in accordance with the terms and conditions of the Schedule hereto and
     any other terms that the Company sees fit and to undertake all
     responsibilities hereby vested for the time being in the Company.

V.   MISCELLANEOUS

     A.  The representations, warranties, covenants and agreements of the
         parties to this Agreement shall survive after the Offer is declared
         unconditional.

                                       3
<PAGE>

     B.  Except as otherwise provided in this Agreement, the parties shall each
         pay their own expenses and costs in connection with this Agreement and
         the transactions contemplated hereby.

     C.  Subject to the requirements of law and regulatory bodies, no party
         shall make any public announcement or press release with respect to
         this transaction without first consulting with the other parties and
         giving such parties the opportunity to review and comment thereon.

     D.  This Agreement and all of the provisions hereof shall be binding upon
         and inure to the benefit of the parties hereto and their respective
         heirs, personal representatives, successors and assigns.

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

     F.  This Agreement (including the instruments between the parties referred
         to herein and any waivers delivered pursuant hereto) constitutes the
         entire agreement among the parties with respect to the subject matter
         hereof and supersedes all other prior agreements and understandings,
         both written and oral, among the parties, or any of them, with respect
         to the subject matter hereof. The exhibits are a part of this Agreement
         as if fully set forth herein. All references to articles, sections,
         subsections, paragraphs, clauses, exhibits and schedules shall be
         deemed references to such part of this Agreement, unless the context
         shall otherwise require.

     G.  No supplement, modification, or amendment of this Agreement or waiver
         of any provision of this Agreement will be binding unless executed in
         writing by, or on behalf of, all parties to this Agreement. No waiver
         of any of the provisions of this Agreement will be deemed or will
         constitute a waiver of any other provision of this Agreement
         (regardless of whether similar), nor will any such waiver constitute a
         continuing waiver unless otherwise expressly provided.

     H.  Descriptive headings contained herein are for convenience of reference
         only and shall not affect the meaning or interpretation hereof.

     I.  This Agreement may be executed in any number of counterparts, each of
         which shall be deemed to be an original but all of which together
         shall constitute but one agreement.

     J.  The parties shall execute, acknowledge and deliver or cause to be
         executed, acknowledged and delivered such instruments and take such
         other action as may be necessary or advisable to carry out their
         obligations under this Agreement and

                                       4
<PAGE>

         under any document, certificate or other instrument delivered pursuant
         hereto or required by law.

                                       5
<PAGE>

IN WITNESS whereof the undersigned have caused this Warrant Agreement to be duly
executed and issued the day and year first above written.

                              The Company:

                              AROC INC.


                              By: ____________________________________
                              Name: __________________________________
                              Title: _________________________________

                              Warrant Holders:

                              ENCAP EQUITY 1996 LIMITED PARTNERSHIP
                              (Holder of 20,933,594 Series J Warrants)
                              By: ENCAP INVESTMENTS L.L.C.

                              By: ____________________________________
                              Name: __________________________________
                              Title: _________________________________

                              ENERGY CAPITAL INVESTMENT COMPANY PLC
                              (Holder of 6,977,865 Series J Warrants)


                              By: ____________________________________
                              Name: __________________________________
                              Title: _________________________________


                              EL PASO CAPITAL INVESTMENTS, L.L.C.
                              (Holder of 11,629,774 Series J Warrants)


                              By: ____________________________________
                              Name: __________________________________
                              Title: _________________________________

                                      6
<PAGE>

                                   SCHEDULE

1.   Subscription Rights

     (a)  At any time after the Company has obtained approval of the increase in
          authorized shares of Common stock of the Company in an amount
          sufficient to permit the exercise of all of the Company's then
          outstanding warrants and the conversion of all of its then outstanding
          Series A Convertible Preferred Stock (the "Charter Amendment"), then a
          registered holder (a "holder") of a Warrant shall have the right,
          exercisable in accordance with paragraph 1(c) below, to subscribe (the
          "subscription rights") in cash on any date on or after January 1,
          2001, but prior to the Expiration Date in respect of such Warrant, on
          the following terms: for each Warrant specified in the Warrant
          certificate one share of Common Stock at the Subscription Price in
          respect of such Warrant payable in full on subscription. The number of
          shares of Common Stock to be subscribed and the subscription price are
          subject to adjustment pursuant to paragraph 2 below. The subscription
          rights will not be exercisable in respect of a fraction of a share of
          Common Stock. Failure to exercise a Warrant prior to 5:00 p.m. (Tulsa,
          Oklahoma time) on the relative Expiration Date will mean that the
          Warrant shall become void and all rights attaching to such Warrant
          shall cease.

     (b)  The number of Warrants to which each registered holder of Warrants
          shall be entitled shall be evidenced by a Warrant certificate issued
          by the Company. Warrant certificates shall be dated as of the date of
          issue, whether on initial issue, transfer, exchange or in lieu of
          mutilated, lost, stolen or destroyed Warrant certificates. Warrants
          shall be deemed to have been exercised immediately prior to the close
          of business on the date of the surrender for exercise of the Warrant
          certificate.

     (c)  In order to exercise the subscription rights in respect of any
          Warrants, the registered Warrant Holder must, after completing the
          notice of exercise on his Warrant certificate, deliver it to the
          office of the Warrant Agent for the Company accompanied by a
          remittance for the total subscription price of the shares of Common
          Stock in respect of which the subscription rights are being exercised.
          Once delivered, a notice of subscription shall be irrevocable except
          with the consent of the Directors of the Company.

     (d)  Shares of Common Stock issued pursuant to the exercise of subscription
          rights will be issued not later than 14 days after, and with effect
          from, the date on which the related duly completed subscription notice
          shall be delivered to the Warrant Agent for the Company (the
          "subscription date") and Common Stock certificates in respect of such
          shares of Common Stock will be issued free of charge and mailed (at
          the risk of the persons entitled thereto) not later than 14 days after
          the relevant subscription date to the first named person in whose name
          the Warrants are registered at the relevant subscription date or
          (subject as provided by law) to such other persons as may be named in
          the form of nomination upon the reverse of the Warrant certificate. In
          the event that not all of the Warrants evidenced by a Warrant
          certificate are exercised, the Company shall at the same time issue
          for no payment a fresh Warrant

                                       1
<PAGE>

          certificate in the name of the Warrant Holder for any balance of the
          subscription rights remaining exercisable.

     (e)  Shares of Common Stock issued pursuant to the exercise of subscription
          rights will not be deemed outstanding for any dividends or other
          distributions declared, made or paid in respect of any financial year
          of the Company prior to the financial year in which the relevant
          subscription date falls, nor shall they be deemed outstanding for any
          dividends or other distributions declared, made or paid on a date (or
          by reference to a record date) prior to the relevant subscription date
          but, subject thereto, will be treated pari passu in all other respects
          with the shares of Common Stock issued at the relevant subscription
          date including being deemed issued for all dividends and other
          distributions in respect of the financial year in which the relevant
          subscription date occurs provided that on any issuance failing to be
          made pursuant to paragraph 3(c) below the shares of Common Stock so to
          be issued shall not be deemed outstanding for any dividends or other
          distributions declared, made or paid by reference to a record date
          prior to the date of issuance.

     (f)  To the extent not then exercised, all subscription rights in respect
          of the Warrants shall lapse at 5:00 p.m. (Tulsa, Oklahoma time) on the
          Expiration Date in respect of such Warrants.

     (g)  No sale, offering or transfer of the Warrants or the shares underlying
          the Warrants is permitted unless validly registered under the
          Securities Act of 1933, as amended, or exempt from the registration
          requirements of that Act.

2.   Adjustment of Subscription Price

     (a)  If, on a date (or by reference to a record date) on or before the
          relative Expiration Date in respect of a Warrant, the Company shall
          issue any Common Stock by way of dividend to holders of Common Stock
          of record on a date (or by reference to a record date) before the
          relative Expiration Date or upon any consolidation or sub-division of
          the Common Stock before such Expiration Date, the number of shares of
          Common Stock to be issued on any subsequent exercise of the
          subscription rights in respect of that Warrant will be increased or,
          as the case may be, reduced in due proportion and the subscription
          price per share of Common Stock will be adjusted accordingly. On any
          such dividend, consolidation or sub-division the Company will cause
          the auditors of the Company to verify the correctness of the
          appropriate adjustments and, within 28 days of such adjustments,
          notice will be sent to each Warrant Holder of the adjusted number of
          shares of Common Stock to which the Warrant Holder is entitled to
          subscribe in consequence thereof, fractional entitlements being
          ignored, such notice being accompanied by a new Warrant certificate in
          respect of such adjusted number of shares of Common Stock.

     (b)  If, on a date (or by reference to a record date) on or before the
          relative Expiration Date, the Company makes any offer or invitation
          (whether by rights issue, rights offer or otherwise but not being an
          offer to which paragraph 3(c) below applies or an offer

                                       2
<PAGE>

          of shares in lieu of a cash dividend payment) to the holders of Common
          Stock in their capacity as such, or any offer or invitation is made to
          such holders otherwise than by the Company, then the Company shall, as
          far as it is able, cause at the same time the same offer or invitation
          to be made to the then Warrant Holders as if their subscription rights
          had been exercisable and had been exercised on the day immediately
          preceding the date (or record date) of such offer or invitation on the
          terms (subject to any adjustment pursuant to paragraph 2(a) above) on
          which the same could have been exercised on the basis then applicable
          provided that, if the Directors shall so resolve, in the case of any
          offer or invitation made by the Company, the Company shall not be
          required to cause the same offer or invitation to be made to the
          Warrant Holders but the subscription price and/or the number of shares
          of Common Stock to be subscribed on any subsequent exercise of the
          subscription rights shall be adjusted accordingly. The Company will
          cause the auditors of the Company to certify in writing the
          appropriateness of the adjustments and, within 28 days, notice will be
          sent to each Warrant Holder together with a new Warrant certificate in
          respect of the adjusted number of share of Common Stock to which that
          Warrant Holder is entitled to subscribe in consequence thereof,
          fractional entitlements being ignored.

     (c)  No adjustment shall be made to the subscription price of a Series of
          Warrants pursuant to paragraph 2(a) or (b) if such adjustment would
          (taken together with the amount of any adjustment carried forward
          under the provisions of this paragraph 2(c)) be less than 1 percent of
          the relative subscription price then in force and on any adjustment
          the adjusted subscription price will be rounded down to the nearest
          $0.01. Any adjustment not so made and any amount by which the
          subscription price is rounded down will be carried forward and taken
          into account in any subsequent adjustment.

3.   Other Provisions

     So long as any subscription rights remain exercisable:

     (a)  after obtaining approval of the Charter Amendment, the Company shall
          reserve for issuance sufficient authorized but unissued shares to
          satisfy in full (without the need for the passing of any further
          resolution by shareholders) all subscription rights remaining
          exercisable;

     (b)  the Company shall not (except with the consent of the holders of at
          least three-fourths of the Warrants of each Series) issue any Common
          Stock by way of a dividend nor make any such offer as is referred to
          in paragraph 2(b) above if as a result the Company would on any
          subsequent exercise of the subscription rights be obliged to issue
          Common Stock for less than the par value thereof;

     (c)  if at any time an offer or invitation is made by the Company to the
          holders of Common Stock for the purchase by the Company of any of its
          Common Stock, the Company shall simultaneously give notice thereof to
          the Warrant Holders and each

                                       3
<PAGE>

          such Warrant Holder shall be entitled at any time while such offer or
          invitation is open for acceptance to exercise his subscription rights
          as if they were then exercisable so as to take effect as if he had
          exercised his rights immediately prior to the date (or record date) of
          such offer or invitation;

     (d)  if the Company commences liquidation, whether voluntary or compulsory
          (except on terms sanctioned by the consent of the holders of at least
          three-fourths of the Warrants), it shall forthwith give notice thereof
          to all holders of Warrants; thereupon each Warrant shall be
          exercisable and each holder of a Warrant will (if in such winding-up
          there shall be a surplus available for distribution among the holders
          of Common Stock (including for this purpose the Common Stock which
          would be issued on the exercise of all the outstanding subscription
          rights) which, taking into account the amounts payable on the exercise
          of the subscription rights, exceeds in respect of each share of Common
          Stock a sum equal to the subscription price) be deemed, as of
          immediately before the date of such order or resolution, to have
          exercised his subscription rights in full and shall accordingly be
          entitled to receive out of the assets available on liquidation pari
          passu with the holders of the Common Stock such a sum as he is
          entitled as a holder of Common Stock to which he becomes entitled by
          virtue of such subscription after deducting a sum per share equal to
          the subscription price; subject to the foregoing, all subscription
          rights shall lapse on liquidation of the Company; and

     (e)  the Company shall not (except with the consent of the holders of at
          least three-fourths of the Warrants of each Series) issue Common Stock
          by way of a dividend unless at the date of such issuance the Directors
          have authority to grant the additional rights to subscribe to which
          the Warrant Holders will by virtue of paragraph 2(a) above to be
          entitled in consequence of such capitalization.

4.   Modification of Rights and Warrant Instrument

     All or any of the rights attached to the Warrants may from time to time
     (whether or not the Company is being wound up) be altered or abrogated with
     the consent of the holders of at least three-fourths of the Warrants of
     each Series affected by such alteration or abrogation. Such alteration or
     abrogation approved as aforesaid shall be effected by a majority vote of
     the Board of Directors executed by the Company and expressed to be
     supplemental to this Warrant Instrument. Modifications to this Warrant
     Instrument which are of a formal, minor or technical nature, or made to
     correct a manifest error, or any modifications which the Directors consider
     appropriate may be effected by a majority vote of the Board of Directors
     executed by the Company and expressed to be supplemental to this Warrant
     Instrument and notice of such alteration or abrogation or modification
     shall be given by the Company to the Warrant Holders.

5.   Purchase by the Company

                                       4
<PAGE>

     The Company shall be entitled at any time to purchase Warrants on the open
     market or otherwise.  Any Warrants so purchased shall be canceled
     immediately and shall not be available for re-issue.

6.   Transfer

     (a)  The Warrants will be registered and transferable in whole or in part
          by instrument of transfer in any usual or common form or in any other
          form which may be approved by the Board of Directors except that no
          transfer of a right to subscribe for a fraction of a share of Common
          Stock shall be effected. Except insofar as the same would be
          inconsistent with this Warrant Instrument, the provisions of the
          Bylaws of the Company relating to the registration, transfer and
          transmission of shares shall apply mutatis mutandis to the Warrants.

     (b)  Notwithstanding any other provision contained herein, for so long as
          any Regulated Entity (as defined herein) holds any Warrants which,
          upon exercise, would result in such Regulated Entity holding more than
          5% of the outstanding Common Stock, such Regulated Entity may only
          transfer the Warrants under the following circumstances:  (i) in a
          widely distributed public offering; (ii) in a transfer pursuant to
          Rule 144 under the United States of America ("U.S.") Securities Act of
          1933, as amended, or any similar rule then in force; (iii) in a
          transfer where the Common Stock underlying the Warrants being
          transferred represent two percent or less of the outstanding Common
          Stock (not including the transfer from the Regulated Entity); (v) in a
          transfer to the Company; (vi) in a transfer to an affiliate or such
          holder or any other Regulated Entity; or (vii) in any method of
          transfer permitted by the Board of Governors of the Federal Reserve
          System of the U.S.

          Once such Regulated Entity holds Warrants and share of Common Stock
          which, after exercise of the Warrants, would constitute 5.0% or less
          of the outstanding Common Stock, the foregoing restrictions on
          transfer shall cease to apply.

          "Regulated Entity" means (i) any entity that is a "bank holding
          company" (as defined in Section 2(a) of the U.S. Bank Holding Company
          Act of 1956, as amended (the "BHC Act")) or any non-bank subsidiary of
          such an entity or (ii) any entity that, pursuant to Section 8(a) of
          the U.S. International Banking Act of 1978, as amended, is subject to
          the provisions of the BHC Act or any non-bank subsidiary of such an
          entity.

7.   Indemnification of Warrant Agent

     (a)  The Warrant Agent shall act as Agent of the Company. The Warrant Agent
          shall not, by issuing and delivering Warrant certificates or by any
          other act, be deemed to make any representations as to the validity or
          value of the Warrant certificates or the Warrants represented thereby
          or of the Common Stock or other property delivered on exercise of any
          Warrant. The Warrant Agent shall not be under any duty or
          responsibility to any holder of the Warrant certificates to make or
          cause to be made

                                       5
<PAGE>

          any adjustment of the Subscription Price or to determine whether any
          fact exists which may require any such adjustments.

     (b)  The Warrant Agent shall not (i) be liable for any statement or fact
          contained in this instrument or for any action taken or omitted by it
          in reliance on any Warrant certificate or other document or instrument
          believed by it in good faith to be valid and to have been signed or
          presented by the proper party or parties, (ii) be responsible for any
          failure on the part of the Company to comply with any of its covenants
          and obligations contained in this instrument or in the Warrant
          certificates, or (iii) be liable for any act or omission in connection
          with this Agreement except for its own negligence or willful
          misconduct.

     (c)  The Warrant Agent may at any time seek legal advice of counsel (who
          may be counsel to the Company) and shall incur no liability or
          responsibility for any action taken or omitted by it in good faith in
          accordance with such notice, statement, instrument, request,
          direction, order or demand.

     (d)  Any notice, statement, instruction, request, direction, order or
          demand of the Company shall be sufficiently evidenced by an instrument
          signed by any officer of the Company. The Warrant Agent shall not be
          liable for any action taken or omitted by it in accordance with such
          notice, statement, instruction, request, direction, order or demand.

     (e)  The Company agrees to pay the Warrant Agent reasonable compensation
          for its services hereunder and to reimburse the Warrant Agent for its
          reasonable expenses. The Company further agrees to indemnify the
          Warrant Agent against any and all losses, expenses and liabilities,
          including judgments, costs and fees, for any action taken or omitted
          by the Warrant Agent in the execution of its duties and powers,
          excepting losses, expenses and liabilities arising as a result of the
          Warrant Agent's negligence or willful misconduct.

8.   General

     (a)  The Company will concurrently with the issue of the same to holders of
          Common Stock send to each holder of a Warrant (or, in the case of
          joint holders, to the first named) a copy of each published annual
          report and accounts of the Company and unaudited interim report of the
          Company together with all documents required by law to be annexed
          thereto, and copies of every statement, notice or report issued to
          holders of Common Stock.

     (b)  For the purposes of this Warrant Instrument, "business day" means a
          day (excluding Saturdays and public holidays) on which banks in the
          States of Oklahoma and Texas are open for business. All the provisions
          of the Bylaws of the Company as to meetings of the shareholders shall
          apply mutatis mutandis as though each series of the Warrants formed a
          separate class of Common Stock of the Company but so that (i) the
          period of notice shall be 21 days at least, (ii) the necessary quorum
          shall be

                                       6
<PAGE>

          Warrant Holders of the relevant series (present in person or
          by proxy) entitled to subscribe for one-third of the Common Stock
          attributable to the then outstanding Warrants of that series, (iii)
          every Warrant Holder present in person at any such meeting shall be
          entitled to one vote for every such share of Common Stock for which he
          is entitled to subscribe, and (iv) if at any adjourned meeting a
          quorum as defined above is not present, a Warrant Holder who is then
          present in person or by proxy shall be a quorum.

     (c)  The invalidity of any undertaking, or any part of any undertaking, in
          paragraph 3 shall not affect the validity of any other part of that
          paragraph.

     (d)  Any determination or adjustment made pursuant to these terms and
          conditions by the auditors of the Company shall be made by them as
          experts and not arbitrators and shall be final and binding on the
          Company and all Warrant Holders.

9.   Governing Law

     THIS AGREEMENT AND THE LEGAL RELATIONS AMONG THE PARTIES HERETO SHALL BE
     GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE STATE
     OF OKLAHOMA, WITHOUT REGARD TO CONFLICT OF LAWS PRINCIPLES.

                                       7
<PAGE>

                              WARRANT CERTIFICATE

---------------------------------------------------------------
                             Date

                    _______________, ____
---------------------------------------------------------------
 Certificate No.   Exercise Price per Share  Number of Warrants

    J_______                $____                 _______
---------------------------------------------------------------

                                   AROC INC.


                       _________________________________


               SERIES "J" WARRANTS TO SUBSCRIBE FOR COMMON SHARES

THIS IS TO CERTIFY that _________________ of _________________________________
is the Registered holder of Warrants to subscribe for __________ shares of
common stock, par value $0.001 per share, ("Common Stock") of AROC Inc. subject
to the conditions endorsed hereon and the provisions of the Certificate of
Incorporation of the Company.



                                    AROC Inc.


                                    By: ______________________________
                                    Name: ____________________________
                                    Title: ___________________________

Dated: ___________________, _____
<PAGE>

                              NOTICE OF EXERCISE

To:  AROC Inc. (the "Company")

1.   I/We, being the registered holder(s) of the Warrants represented by this
     certificate, hereby give notice of my/our desire to exercise my/our
     subscription rights in respect of _________/1/ shares of Common Stock of
     the Company in accordance with the conditions applicable thereto and
     request that such shares be issued for the total price of $__________ for
     which we enclose my/our check.

2.   I/We agree to accept all of the shares of Common Stock of the Company to be
     issued to me/us pursuant hereto subject to the Certificate of Incorporation
     of the Company. I/We desire all such Common Stock to be registered in
     my/our name(s) and hereby authorize the entry of my/our name(s) in the
     stock transfer records of the Company in respect thereof and the delivery
     of a certificate therefor by United States mail at my/our risk to the
     person whose name and address is set out below or, if none is set out, to
     the registered address of the sole or first named holder.

3.   I/We hereby authorize the delivery of a certificate for the balance (if
     any) of the Warrants represented by this certificate which are not
     exercised by United States mail at my/our risk to the person whose name and
     address is set out below or, if none is set out, to the sole or first named
     holders at his/her registered address.

     Dated: ____________________________

     Signature(s) of Warrant Holder(s)/2/:

                     _________________________________________________

                     _________________________________________________

     Name/3/:        _________________________________________________

__________________________

     /1/  Delete or complete as appropriate. If no amount is inserted, the
          notice of exercise will be deemed to relate to all of the shares of
          common stock subject to the Warrant.

     /2/  In the case of joint holders ALL should sign. A corporation or other
          entity should execute through an officer or attorney duly authorized
          in that behalf in which event the Warrant must be accompanied by the
          authority under which this notice is completed.

     /3/  Please insert in BLOCK CAPITALS the name and/or the address of the
          person to whom you wish the common stock share certificate and any
          balance certificate for Warrants to be sent if it is different from
          that of the sole or first named Warrantholder.
<PAGE>

     Address:  _______________________________________________________________