P O W E R  O F  A T T O R N E Y
                                   SECTION 16


         The undersigned, John A. Briffett, hereby:

     l. Employs, appoints,  authorizes,  empowers, and constitutes the Corporate
Secretary of Unocal Corporation,  a Delaware corporation ("Unocal"), or any duly
appointed Assistant Secretary of Unocal, and each of them as his true and lawful
attorneys-in-fact to:

         (a)      fill out and file and execute on his behalf certain reporting
                  forms known as Form 3, Form 4, and Form 5, and any amendments
                  and corrections thereto, or any other forms prescribed by the
                  Securities and Exchange Commission (or other authorities)
                  under Section 16(a) of the Securities Exchange Act of 1934
                  (the "Act"), as amended, as such forms pertain to his holdings
                  of securities in Unocal; and

         (b)      do and perform all things incident, necessary and proper to
                  appropriately complete, execute and file said forms, and in
                  conjunction therewith to do all things which in the opinion of
                  the attorney(s)-in-fact may be of benefit to, in the best
                  interest of, or legally required by, the undersigned.

     2. Grants to each such  attorney-in-fact full power and authority to do and
perform all and every act and thing whatsoever requisite,  necessary, and proper
to be done in the exercise of any of the rights and powers  herein  granted,  as
fully to all intents and purposes as such attorney-in-fact  might or could do if
personally  present,  with full power of  substitution  and  revocation,  hereby
ratifying and  confirming all that such  attorney-in-fact,  or his substitute or
substitutes,  shall  lawfully  do or cause to be done by virtue of this Power of
Attorney and the rights and powers herein granted.

     3. Represents and warrants to Unocal and to its directors, officers and the
attorneys-in-fact  appointed  hereby,  that the  undersigned  will provide full,
accurate,  and timely  information  to them,  in the detail and at the frequency
which  they may  demand,  as to his  direct  and  indirect  interests  in Unocal
securities,  as well as any changes  therein,  in order to enable them to assist
the undersigned in fulfilling the reporting requirements of Section 16(a) of the
Act.

     4.  Acknowledge  that the foregoing  attorneys-in-fact,  in serving in such
capacity  at the request of the  undersigned,  are not  assuming,  nor is Unocal
assuming, any of the undersigned's responsibilities to comply with Section 16 of
the Securities and Exchange Act of 1934.

     5. This Power of Attorney  shall remain in effect until revoked in a signed
writing by the undersigned delivered to the Corporate Secretary.



                                  /S/ John A. Briffett
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                                          Signature

DATED:   24 March 2005
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