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                                                                    EXHIBIT 4.10

                            CERTIFICATE OF AMENDMENT

                                       OF

                          CERTIFICATE OF INCORPORATION

                                       OF

                          MISSION RESOURCES CORPORATION

         Mission Resources Corporation, a corporation organized and existing
under the General Corporation Law of the State of Delaware (the "Corporation"),
does hereby certify:

         The amendments to the Corporation's Certificate of Incorporation set
forth in the following resolution approved by the Corporation's Board of
Directors and stockholders were duly adopted in accordance with the provisions
of Section 242 of the General Corporation Law of the State of Delaware:

         "RESOLVED, that the introductory paragraph of Article Four of the
Company's Certificate of Incorporation is hereby amended in its entirety so
that, as amended, it shall be and read as follows, with the remainder of Article
Four to remain unamended:

                  The Corporation shall have authority to issue two classes of
         stock, and the total number authorized shall be sixty million
         (60,000,000) shares of Common Stock of the par value of one cent ($.01)
         each, and five million (5,000,000) shares of Preferred Stock of the par
         value of one cent ($.01) each. A description of the different classes
         of stock of the Corporation and a statement of the designations and the
         powers, preferences and rights, and the qualifications, limitations or
         restrictions thereof, in respect of each class of such stock are as
         follows:"

         IN WITNESS WHEREOF, Mission Resources Corporation has caused this
Certificate to be signed and attested by its duly authorized officers, this 8th
day of May, 2001.

                                           MISSION RESOURCES CORPORATION



                                           By: /s/ Douglas Manner
                                              ----------------------------------
                                               Douglas Manner, Chief Executive
                                               Officer

Attest:


/s/ Roland E. Sledge
-------------------------------------
Roland E. Sledge, Secretary