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                                                                    EXHIBIT 10.4

                              FOURTH AMENDMENT TO
                      UNION TEXAS PETROLEUM HOLDINGS, INC.
                             1987 STOCK OPTION PLAN


         WHEREAS, UNION TEXAS PETROLEUM HOLDINGS, INC. (the "Company") has
heretofore adopted the UNION TEXAS PETROLEUM HOLDINGS, INC. 1987 STOCK OPTION
PLAN (the "Plan"); and

         WHEREAS, subsequent thereto, the Company has amended the Plan; and

         WHEREAS, the Company desires to amend the Plan in certain respects;

         NOW THEREFORE, the Plan shall be amended as follows, effective May 9,
1997:

         1.      Paragraph IV shall be amended by adding the term "Except as
provided below," at the beginning of the first sentence, by adding "or pursuant
to a qualified domestic relations order as determined by the Committee" at the
end of the first sentence and by adding the following after the first sentence
of such Section:

         "The Committee may, in its discretion, adopt rules or guidelines under
         which any Option previously granted to an Optionee may be transferred
         (in whole or in part pursuant to such form as approved by the Company)
         by the Optionee to (i) the spouse, children or grandchildren of the
         Optionee ("Immediate Family Members"), (ii) a trust or trusts for the
         exclusive benefit of the Immediate Family Members and, if applicable,
         the Optionee, (iii) a partnership, limited liability company or other
         entity in which such Immediate Family Members and, if applicable, the
         Optionee are the only partners, members or stockholders, (iv) the
         transferee pursuant to a qualified domestic relations order as
         determined by the Committee, (v) an organization described under
         Section 501(c)(3) of the Code and which is a private foundation within
         Section 509(a) of the Code or any trust the only beneficiary (other
         than an Immediate Family member and, if applicable, the Optionee) of
         which is an organization described under Section 501(c)(3) of the Code
         and which organization is a private foundation within Section 509(a)
         of the Code or (vi) to other persons or entities as approved by the
         Board or the Committee in its discretion.  Following transfer, any
         such Option shall continue to be subject to the same terms and
         conditions as were applicable to the Option immediately prior to
         transfer; provided, however, that no transferred Option shall be
         exercisable or payable, as the case may be, unless arrangements
         satisfactory to the Company have been made to satisfy any tax
         withholding obligations the Company may have with respect to the
         Option."

         2.      Paragraph VIII shall be amended by adding the term "Except as
provided in Paragraph IV," at the beginning of the first sentence of such
Section and by adding the following phrase ", which arrangement in the
discretion of the Committee may include the
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relinquishment of a portion of the shares subject to the Option or delivery of
shares of Stock owned by the Optionee" to the end of Paragraph VIII(b), before
the last word "and".

         3.      As amended hereby, the Plan is specifically ratified and
                 reaffirmed.

         IN WITNESS WHEREOF, this Fourth Amendment has been executed this 9th
day of May, 1997.

                                        UNION TEXAS PETROLEUM HOLDINGS, INC.



                                        By: /s/ J. L. WHITMIRE                
                                           -------------------------------------
                                            J. L. Whitmire
                                            Chairman and Chief Executive Officer
ATTEST:



/s/ LINDA L. MEAGHER              
- ----------------------------------
L. L. Meagher
Assistant Secretary