EXHIBIT 3.1
                      RESTATED CERTIFICATE OF INCORPORATION

                                       of

                       PIONEER NATURAL RESOURCES USA, INC.


     Pioneer  Natural   Resources  USA,  Inc.,  a  Delaware   corporation   (the
"Corporation"),  pursuant  to the  provisions  of  Section  245 of the  Delaware
General   Corporation   Law,   hereby  adopts  this  Restated   Certificate   of
Incorporation  (this  "Restated  Certificate  of  Incorporation"),   which  only
restates and  integrates,  but does not further  amend,  the  provisions  of the
Corporation's   Certificate  of   Incorporation   as   theretofore   amended  or
supplemented.   There  is  no  discrepancy  between  those  provisions  and  the
provisions of this Restated  Certificate of  Incorporation.  The Corporation was
originally  incorporated  under the name "Mesa Sub 1,  Inc." , and its  original
Certificate of Incorporation  was filed with the Delaware  Secretary of State on
December 30, 1993. This Restated  Certificate of Incorporation  was duly adopted
in accordance with Section 245 of the Delaware General Corporation Law.

     FIRST:  The name of the corporation is Pioneer Natural  Resources USA, Inc.
(the "Corporation").

     SECOND:  The address of the  registered  office of the  Corporation  in the
State of  Delaware  is 1209  Orange  Street,  Wilmington,  county of New Castle,
Delaware  19801.  The name of the  registered  agent of the  Corporation at such
address is The Corporation Trust Company.

     THIRD:  The  purpose of the  Corporation  is to engage in any lawful act or
activity for which  corporations may be organized under the General  Corporation
Law of the State of Delaware (the "General Corporation Law").

     FOURTH:  The total  number of shares of stock which the  Corporation  shall
have the authority to issue is 1,000 shares of common stock,  par value $.01 per
share ("Common Stock").

     In the event of a voluntary  or  involuntary  liquidation,  dissolution  or
winding up of the affairs of the  Corporation  and upon any  distribution of the
assets of the Corporation in connection  therewith,  the holders of Common Stock
shall be  entitled to receive all the assets of the  Corporation,  tangible  and
intangible, of whatever kind available for distribution to stockholders, ratably
in proportion to the number of shares of Common Stock held by them.

     Each holder of Common Stock shall have one vote in respect of each share of
Common Stock held by such holder on any matter  submitted  to the  stockholders.
Cumulative voting of shares of Common Stock is prohibited.

     FIFTH:  The business and affairs of the Corporation  shall be managed by or
under  the  direction  of the  Board of  Directors.  In  furtherance  and not in
limitation  of the  powers  conferred  by  statute,  the Board of  Directors  is
expressly authorized  to adopt,  amend or repeal the  Bylaws of the Corporation;

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provided,  however,  that the  grant of such  authority  shall  not  divest  the
stockholders of the power,  nor limit their power to adopt,  amend or repeal the
Bylaws.  The  number of  directors  that  shall  constitute  the whole  Board of
Directors of the  Corporation  shall be as from time to time fixed by, or in the
manner  provided  in, the Bylaws of the  Corporation.  The election of directors
need not be by written ballot,  unless the Bylaws so provide. In addition to the
authority and powers hereinabove or by statute conferred upon the directors, the
directors are hereby authorized and empowered to exercise all such powers and do
all such acts and things as may be exercised or done by the Corporation, subject
to  the  provisions  of  the  General   Corporation  Law,  this  Certificate  of
Incorporation  and any Bylaws adopted by the  stockholders  of the  Corporation;
provided,  however,  that no Bylaws hereafter adopted by the stockholders of the
Corporation shall invalidate any prior act of the directors that would have been
valid if such Bylaws had not been adopted.

     SIXTH:  No director of the  Corporation  shall be personally  liable to the
Corporation  or any of its  stockholders  for  monetary  damages  for  breach of
fiduciary duty as a director involving any act or omission of any such director;
provided, however, that the foregoing provision shall not eliminate or limit the
liability of a director (a) for any breach of the director's  duty of loyalty to
the Corporation or its stockholders, (b) for acts or omissions not in good faith
or which involve intentional misconduct or a knowing violation of law, (c) under
Section 174 of the General  Corporation Law, as the same exists or hereafter may
be  amended,  or (d) for any  transaction  from  which the  director  derived an
improper personal benefit.  If the General  Corporation Law is amended after the
date of filing of this  Certificate  of  Incorporation  to  authorize  corporate
action further limiting or eliminating the personal liability of directors, then
the liability of a director of the Corporation, in addition to the limitation on
personal liability  provided for herein,  shall be limited to the fullest extent
permitted  by  the  General  Corporation  Law  as  so  amended.  Any  repeal  or
modification of this Article Sixth by the stockholders of the Corporation  shall
be  prospective  only,  and shall not  adversely  affect any  limitation  on the
personal liability of a director of the Corporation existing at the time of such
repeal or modification.

     SEVENTH: The Corporation expressly elects not to be governed by Section 203
of the General Corporation Law, as the same exists or hereafter may be amended.

     IN WITNESS WHEREOF, the Corporation has caused this Restated Certificate of
Incorporation to be signed by its authorized officer as of November 10, 1997.


                                       PIONEER NATURAL RESOURCES USA, INC.


                                       By:        /s/ Garrett Smith
                                              -------------------------------
                                              M. Garrett Smith,
                                              Senior Vice President - Finance


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