<PAGE>   1
                                                                   EXHIBIT 10.15


                              CONSULTING AGREEMENT


         This Consulting Agreement dated as of July 26, 1996 between
Weatherford Enterra, Inc. (the "Company") and Thomas N. Amonett (the
"Consultant").

         WHEREAS, the Company desires to engage Consultant to perform certain
services, as hereinafter specified; and

         WHEREAS, Consultant is willing to enter into this Agreement with
respect to such services upon the terms and conditions hereinafter set forth;

         NOW, THEREFORE, in consideration of the premises and of the mutual
agreements hereinafter set forth, the parties hereto agree as follows:

 1.      Duties.  Consultant will serve as Acting President and Chief Executive
         Officer of the Company and otherwise consult with the Board of
         Directors for the term of this Agreement.

 2.      Term and Termination.  This Agreement will commence on July 26, 1996
         and will continue indefinitely until terminated by either party's
         giving written notice to the other of its intention to terminate same.

 3.      Compensation.  The Company will pay to Consultant $22,750 per month,
         commencing July 26, 1996.  The Consultant will continue to receive his
         quarterly retainer and meeting fees owed by the Company in connection
         with his serving as a director of the Company.

 4.      Relationship Between the Parties.  Consultant is retained and engaged
         by the Company only for the purposes and to the extent set forth in
         this Agreement, and his relation to the Company and its affiliated or
         subsidiary companies shall be that of an independent contractor, and
         he shall be free to dispose of such portion of his entire time, energy
         and skill during regular business hours as he is not obligated to
         devote hereunder to the Company and its affiliated or subsidiary
         companies, to other pursuits, persons, firms or corporations which are
         not competitive to the businesses or products of the Company.
         Consultant shall not be considered under the provisions of this
         Agreement or otherwise as having an employee status and shall not be
         entitled to participate in any plans, arrangements or distributions by
         the Company or its affiliated or subsidiary companies pertaining to or
         in connection with any pension, stock, bonus, insurance, profit
         sharing or similar benefits for the Company's regular employees.





                                     - 1 -
<PAGE>   2
 5.      Taxes.  Consultant will be liable for all taxes imposed on him or his
         business by any government.  Accordingly, the Company will not
         withhold from Consultant's fees any monies for payment of taxes,
         including income taxes, social security taxes, etc.  Consultant agrees
         to hold harmless and indemnify the Company from and against the
         payment of any taxes on account of Consultant's performance hereunder.

 6.      Trade Secrets and Confidential Information.  Consultant recognizes and
         acknowledges that he may have access to certain trade secrets and
         other confidential information of the Company and corporations
         affiliated with the Company and that such information constitutes
         valuable, special and unique property of the Company and such other
         corporations.  Consultant will keep such information strictly
         confidential and will not, during the term of this Agreement, or for a
         period of five (5) years after the termination hereof, disclose any of
         such trade secrets or confidential information to any person, firm,
         corporation or other entity for any reason or purpose whatsoever
         except to authorized representatives of the Company and its affiliated
         corporations.  In the event of a breach or threatened breach by
         Consultant of the provisions of this provision, the Company shall be
         entitled to an injunction restraining Consultant from disclosing, in
         whole or in part, such trade secrets and confidential information.
         Nothing herein shall be construed as prohibiting the Company from
         pursuing any other remedies available to it for such breach or
         threatened breach, including the recovery of damages from Consultant.

 7.      Other Contracts.  Consultant warrants that his entering into this
         Agreement does not conflict with any obligations he has under any
         other agreement.

 8.      Conflict of Interest.  Consultant agrees that he will not, without the
         prior written consent of the Company, serve any interest or do any act
         or thing which would, in the reasonable opinion of the Company,
         conflict with the interests of the Company or any of its affiliates
         during the term of this Agreement, and Consultant will not, without
         the prior written consent of the Company, enter into competition with
         the Company or any of its affiliated or subsidiary companies or
         perform services for any competitor of the Company or any of its
         affiliated or subsidiary companies during said period.

 9.      Notices.  Any notice required or permitted to be given under this
         Agreement shall be in writing and shall be deemed to have been given
         when deposited in the U.S. mail in a registered, postage prepaid
         envelope addressed, if to Consultant, 3609 W. Clay, Houston, Texas
         77019, and if to the Company, Weatherford Enterra, Inc., 1360 Post Oak
         Boulevard, Houston, Texas 77056, Attn.: H. Suzanne





                                     - 2 -
<PAGE>   3
         Thomas, or to such other address as either party shall designate by
written notice to the other.

10.      Assignment.  Consultant may not assign his rights or obligations
         hereunder without obtaining the prior written consent of the Company.
         The rights and obligations of the Company hereunder shall inure to the
         benefit of and shall be binding upon the successors and assigns of the
         Company.

11.      Miscellaneous.

         (a)     This Agreement shall be subject to and governed by the laws of
                 the State of Texas.

         (b)     Failure to insist upon strict compliance with any provision
                 hereof shall not be deemed a waiver of such provision or any
                 other provision hereof.

         (c)     This Agreement may not be modified except by an agreement in
                 writing executed by the parties hereto.

         (d)     The invalidity or unenforceability of any provision hereof
                 shall not affect the validity or enforceability of any other
                 provision.

12.      Entire Agreement.  This Agreement contains the entire agreement of the
         parties hereto with respect to the engagement of Consultant by the
         Company.

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
day and year first above written.


                                        WEATHERFORD ENTERRA, INC.



                                        By:     /s/ H. SUZANNE THOMAS
                                                -------------------------------
                                        Name:   H. Suzanne Thomas              
                                        Title:  Senior Vice President and      
                                                Secretary                      
                                                                               
                                                                               
                                                /s/ THOMAS N. AMONETT
                                        ---------------------------------------
                                                Thomas N. Amonett





                                     - 3 -
<PAGE>   4
                    FIRST AMENDMENT TO CONSULTING AGREEMENT

         This First Amendment to Consulting Agreement dated as of January 1,
1997 between Weatherford Enterra, Inc. (the "Company") and Thomas N. Amonett
(the "Consultant").

         WHEREAS, the Company and Consultant have previously entered into that
certain Consulting Agreement dated as of July 26, 1996 (the "Consulting
Agreement"); and

         WHEREAS, the parties which to amend the Consulting Agreement;

         NOW, THEREFORE, in consideration of the premises and of the mutual
agreements hereinafter set forth, the parties agree as follows:

         1.      Section 3 of the Consulting Agreement is hereby deleted in its
entirety and replaced with the following language:

         "COMPENSATION.

         (a)     The Company will pay to Consultant $30,000 per month,
                 commencing January 1, 1997.  Consultant will continue to
                 receive his quarterly retainer and meeting fees owed by the
                 Company in connection with his serving as a director of the
                 Company during the term of this agreement.

         (b)     Upon Consultant's services as Acting President and Chief
                 Executive Officer no longer being required, the Company will
                 pay to Consultant an amount equal to one year's pay, such
                 amount to be paid at such times and in such installments as
                 directed by Consultant.  In addition, the Company will provide
                 Consultant with an office and secretarial assistance for one
                 year thereafter; provided, however, that this shall be
                 furnished at no additional cost to the Company."

         2.      The remainder of the Consulting Agreement shall remain in full
force and effect as written.
                     
         IN WITNESS WHEREOF, the parties have executed this First Amendment to
Consulting Agreement as of the day and year first above written.

                                        WEATHERFORD ENTERRA, INC.

                                         
                                         
                                        By:     /s/ H. SUZANNE THOMAS
                                               ---------------------------------
                                        Name:       H. Suzanne Thomas
                                               ---------------------------------
                                        Title:      Sr. Vice President and
                                                         Secretary
                                               ---------------------------------
                                                                              
                                        /s/ Thomas N. Amonett
                                        ----------------------------------------
                                        Thomas N. Amonett