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                                                                  EXHIBIT 10.13
 
                               FIRST AMENDMENT TO
                      UNION TEXAS PETROLEUM HOLDINGS, INC.
                             1992 STOCK OPTION PLAN
 
     WHEREAS, UNION TEXAS PETROLEUM HOLDINGS, INC. (the "Company") has
heretofore adopted the UNION TEXAS PETROLEUM HOLDINGS, INC. 1992 STOCK OPTION
PLAN (the "Plan"); and
 
     WHEREAS, the Company desires to amend the Plan in certain respects;
 
     NOW, THEREFORE, the Plan shall be amended, subject to stockholder approval,
as follows, effective as of January 26, 1995:
 
     1. Subparagraph (c) of Paragraph X of the Plan shall be deleted and the
following shall be substituted therefor:
 
     "In the event that the Committee determines that any dividend or other
     distribution (whether in the form of cash, Stock, other securities, or
     other property), recapitalization, stock split, reverse stock split,
     reorganization, merger, consolidation, split-up, spin-off, combination,
     repurchase, or exchange of Stock or other securities of the Company,
     issuance of warrants or other rights to purchase Stock or other securities
     of the Company, or other similar corporate transaction or event affects the
     Stock such that an adjustment is determined by the Committee to be
     appropriate in order to prevent dilution or enlargement of the benefits or
     potential benefits intended to be made available under the Plan, then the
     Committee shall, in such manner as it may deem equitable, adjust any or all
     of (i) the number and type of shares of Stock (or other securities or
     property) with respect to which Options may be granted, (ii) the number and
     type of shares of Stock subject to outstanding Options, and (iii) the grant
     or exercise price with respect to any Option or, if deemed appropriate,
     make provision for a cash payment to the holder of an outstanding Option;
     provided, in each case, that with respect to Incentive Stock Options and
     Options intended to qualify as performance based compensation under Section
     162(m)(4)(C) of the Code, no such adjustment shall be authorized to the
     extent that such authority would cause the Plan to violate Section
     422(b)(1) of the Code or would cause such Option to fail to so qualify
     under Section 162(m) of the Code, as the case may be, or any successor
     provisions thereto; and provided, further, that the number of shares of
     Stock subject to any Option shall always be a whole number. In addition to
     the Committee's authority set forth in Paragraph X(b) and (c) of the Plan,
     in order to maintain the Optionees' rights in the event of any Change in
     Control, as hereinafter defined, the Committee, as constituted before such
     Change in Control, is hereby authorized and directed to provide for the
     acceleration of any time periods relating to the exercise or realization of
     all Options so that such Option may be exercised or realized in full, and
     has sole discretion, as to any Option, either at the time such Option is
     made hereunder or any time thereafter, to take any one or more of the
     following actions: (i) provide for the purchase of any such Option, either
     automatically or upon the Optionee's request, for an amount of cash equal
     to the amount that could have been attained upon the exercise of such
     Option or realization of the Optionee's rights had such Option been
     currently exercisable or payable; (ii) make such adjustment to any such
     Option then outstanding as the Committee deems appropriate to reflect such
     Change in Control; or (iii) if equitable and in the best interests of the
     Company and its shareholders, cause any such Option then outstanding to be
     assumed, or new rights substituted therefor, by the acquiring or surviving
     corporation after such Change in Control. The Committee may, in its
     discretion, include such further provisions and limitations in any Option
     Agreement as it may deem equitable and in the best interests of the
     Company. A "Change in Control" shall be deemed to occur (1) if any person
     or persons or entity or entities (other than Petroleum Associates, L.P.,
     KKR Partners II, L.P. and any entity controlling, controlled by or under
     common control with any such entities, separately or in the aggregate
     ("KKR")) acquires 75% or more of the assets of the Company or a successor
     of the Company or such successor's parent corporation (based upon the then
     current fair market value thereof) or 50% or more of the Company's then
     outstanding voting stock or a successor's or such successor's parent
     corporation's then outstanding voting

 
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     securities, and, if there shall be more than one class of voting securities
     thereof, then of the combined voting power held by all classes of voting
     securities of the Company, a successor corporation or its parent
     corporation (whether such acquisition of stock or assets occurs pursuant to
     a single transaction or several related transactions or series of
     transactions), (2) upon the approval by the Company's stockholders of a
     plan of liquidation or dissolution of the Company or a successor of the
     Company or such successor's parent corporation, or (3) upon the approval by
     the Company's stockholders of a merger or consolidation and such
     transaction was determined to be a Change in Control, which transaction and
     determination was approved by a majority of the Company's Board of
     Directors in actions taken prior to, and with respect to such transaction."
 
     2. As amended hereby, the Plan is specifically ratified and reaffirmed.
 
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