<PAGE>   1
                                                                   Exhibit 10.15


                       INTERNATIONAL CONSULTING AGREEMENT



         YPF Sociedad Anonima (hereinafter referred to as the "Company"), a
sociedad anonima organized under the laws of the Republic of Argentina, with
principal offices at Avenida Pte. Roque Saenz Pena 777, Buenos Aires 1364,
Argentina, and C. L. Blackburn (hereinafter referred to as "Consultant"), whose
address is 3705 Gillon Avenue, Dallas, Texas 75205, hereby agree as follows:

         1.      The Company desires to engage Consultant on the terms and for
the period set forth herein as an international consultant (the "Consulting
Services").  Consultant agrees to provide the Consulting Services on the terms
and for the period set forth herein.  In performing the Consulting Services,
Consultant shall have direct access to Jose A. Estenssoro and Nells Leon, the
Company's President and Chief Executive Officer and Executive Vice President
and Chief Operating Officer, respectively, or their successors.

         2.      The term of this Agreement shall commence on May 1, 1995  and
shall remain in effect for a term of two years; provided, however, that  this
Agreement will terminate upon Consultant's death if he should die during the
term hereof.

         3.      As the fee for the Consulting Services, the Company shall pay
Consultant a retainer of US$180,000 per year, payable in monthly installments
of US$15,000 on or before the first day of
<PAGE>   2
every month during the term hereof. Should Consultant provide more than 60 days
of Consulting Services during the first or second 12-month period hereof,
Company shall pay him US $3000 for each day during which Consulting Services
are so provided in excess of 60 days in either 12-month period.  Consultant
shall invoice the Company monthly for Consulting Services performed in excess
of 60 days in such a 12-month period, and Consultant's invoices shall set forth
the total number of days in which Consulting Services were performed during the
applicable month. Consultant is to send any such invoices to Cedric Bridger at
the address given for the Company first above.   Such invoices will be paid
within ten (10) business days after receipt.

         If and to the extent Consultant serves as a director of Maxus Energy
Corporation, a majority owned subsidiary of the Company (Maxus"), during the
term hereof, Consultant waives the right to receive compensation in addition to
that provided herein for his service as a director of Maxus unless he has
previously provided Consulting Services in excess of 60 days during the
relevant 12-month period.  However, it is understood and agreed that time spent
performing duties as a director of Maxus shall be deemed to be the performance
of Consulting Services.

         4.      Within ten (10) business days after receipt of an  invoice,
the Company shall reimburse Consultant for reasonable travel, entertainment,
out of town living and similar expenses incurred by him in connection with the
Consulting Services rendered





                                      -2-
<PAGE>   3
hereunder.  Such invoices are to be sent to Cedric Bridger at the address given
for the Company first above.

         5.      Subject to the other provisions hereof, during the term
hereof, Consultant will make himself available to perform the Services at least
60 days during each of the first and second 12-month periods hereof.

         The Company specifically acknowledges and agrees that Consultant is
free to serve as a director of companies or other entities not affiliated with
the Company, provided that and for so long as such other companies and entities
do not in any material way compete with, provide goods or services to, or
otherwise generate conflicts with the Company.

         6.      The Company agrees to provide Consultant with mutually
agreeable office space, reserved parking, supplies and support services,
including secretarial support, at its headquarters' offices in Buenos Aires,
Argentina and at Maxus' headquarters' offices in Dallas, Texas, U.S.A. as may
be necessary or appropriate in connection with Consultant's performance of the
Consulting Services at such locations.

         7.      Consultant is an independent contractor hereunder with the
responsibility for, and control over, the details and means of performing the
Consulting Services.  In this connection, it is understood and agreed that the
Company is interested in results and





                                      -3-
<PAGE>   4
shall not have the right to control the details of the Services to be performed
hereunder or the manner in which they are performed.

         8.      Confidentiality.  All data and information which may be
received by Consultant from the Company, directly or indirectly, or developed
by him in connection with his performing the Consulting Services shall be kept
confidential by him and will be utilized only for the purposes of carrying out
the Consulting Services to be provided hereunder.

         9.      The Company represents that if any approval of this Agreement
by its Board of Directors or any committee thereof is required to make this
Agreement binding on the Company, such approval has been given.

         10.     This Agreement may not be assigned by Consultant and may be
assigned by the Company only to a corporation into which the Company is merged
or which acquires substantially all of the Company's assets.

         11.     This Agreement is entered into in Dallas, County, Texas,
U.S.A.  All payments provided for herein are payable in Dallas County, Texas,
U.S.A. in United States dollars.





                                      -4-
<PAGE>   5
         12.     This Agreement shall be construed under the laws of the State
of Texas, without giving effect to its conflicts of laws principles.

         13.     (a) The Company consents to the non-exclusive jurisdiction of
any court of the State of Texas or any United States federal court sitting in
Dallas, Dallas County, Texas, U.S.A., and any appellate court from any thereof,
and waives any immunity from the jurisdiction of such courts over any suit,
action or proceeding that may be brought in connection with this Agreement.
The Company irrevocably waives, to the fullest extent permitted by law, any
objection to any suit, action or proceeding that may be brought in connection
with this Agreement in such courts whether on the grounds of venue, residence
or domicile or on the ground that any such suit, action or proceeding has been
brought in an inconvenient forum.  The Company agrees that final judgment in
any such suit, action or proceeding brought in such court shall be conclusive
and binding upon the Company and may be enforced in any court to the
jurisdiction of which the Company is subject by suit upon such judgment.
Notwithstanding the foregoing, any suit, action or proceeding brought in
connection with this Agreement may be instituted in any competent court in
Argentina.

         (b)  The Company agrees that service of all writs, process and
summonses in any suit, action or proceeding brought in connection with this
Agreement against the Company in any court sitting in Dallas, Dallas County,
Texas, U.S.A. may be made upon the General





                                      -5-
<PAGE>   6
Counsel of Maxus Energy Corporation, 717 N. Harwood St., Dallas, Texas 75201,
U.S.A., whom the Company irrevocably appoints as its authorized agent for
service of process for purposes of this Agreement and all actions brought in
connection herewith.  The Company represents and warrants that Maxus' General
Counsel has agreed to act as the Company's agent for service of process.   The
Company agrees that such appointment shall be irrevocable so long as this
Agreement shall remain in effect or until the irrevocable appointment by the
Company of a successor in Dallas, Texas as its authorized agent for such
purpose and the acceptance of such appointment by such successor.  The Company
shall provide Consultant in writing the name and address of such successor
agent. With respect to any such action in any court of the State of Texas or
any United States federal court in Dallas, Dallas County, Texas, U.S.A. service
of process upon Maxus' General Counsel, as the authorized agent of the Company
for service of process, and written notice of such service to the Company,
shall be deemed, in every respect, effective service of process upon the
Company.

         (c)     Nothing in this Section 14 shall affect the right of any party
to serve legal process in any other manner permitted by law or affect the right
of any party to bring any action or proceeding against any other party or its
property in the courts of other jurisdictions.

         14.     Should any provision hereof be unenforceable or otherwise
illegal, the remainder of this Agreement shall not be affected, and





                                      -6-
<PAGE>   7
the provision held to be unenforceable or illegal shall be reformed to the
extent (and only to the extent) necessary to make it enforceable and legal.

         Executed as of the 1st day of May, 1995.



                                        YPF SOCIEDAD ANONIMA
                                        
                                        By: [ILLEGIBLE]
                                           -----------------------------------
                                        
                                        
                                        
                                           /s/ C. L. BLACKBURN
                                           -----------------------------------
                                           C. L. Blackburn





                                      -7-