Unocal Says Mad Dog Appraisal Well Encounters Significant Oil Pay and Extends Field

Unocal Says Mad Dog Appraisal Well Encounters Significant Oil Pay
and Extends Field 


EL SEGUNDO, Calif., March 22  /PRNewswire-FirstCall/ -- Unocal Corporation
(NYSE:UCL) today said that an appraisal well drilled on the deepwater Mad Dog
Southwest Ridge in the Gulf of Mexico encountered significant hydrocarbon pay.
The discovery was further delineated by three sidetracks.

The original hole was drilled to a total measured depth of 22,890 feet from
Green Canyon 826 to downdip targets in the adjacent Green Canyon 825 block. 
The blocks are located in approximately 5,000 feet of water.

The well and sidetracks were designed to test the previously undrilled
southwest flank of the field.  The penetrations individually encountered up to
approximately 300 feet of net oil pay in the early Miocene section and found
hydrocarbons some 700 feet deeper on the west flank of the structure than
previously encountered.

The resources associated with these appraisal wells could either be produced
through spar development wells or future subsea tie-backs.

"We are pleased with the results of this appraisal program which has extended
the limits of the Mad Dog field," said Joseph H. Bryant, Unocal president and
chief operating officer.

The Mad Dog field began production in January 2005 from Green Canyon block 782.
 Gross field production is currently about 30,000 barrels of oil per day from
two wells.

Unocal owns a 15.6 percent working interest in the Mad Dog unit, with net
interest after royalty of 13.3 percent.  BP is the operator with a 60.5 percent
working interest, and BHP Billiton owns a 23.9 percent working interest.

The Mad Dog appraisal was drilled from the Discoverer Spirit drillship, which
is under contract to Unocal.  The ship has moved to drill the Knotty Head
prospect on Green Canyon block 512.  The ship is then scheduled to drill the
St. Malo #3 appraisal well on Walker Ridge block 677.

At the completion of the St. Malo well, the ship will be subleased to another
company for the remainder of its lease term.  Unocal's commitment to the
Discoverer Spirit terminates in September 2005.

About Unocal Corporation

Unocal is one of the world's leading independent natural gas and crude oil
exploration and production companies. The company's principal oil and gas
activities are in Asia and North America.

This news release contains forward-looking statements about matters such as
drilling, development and other plans for future operations. Although these
statements are based upon Unocal's current expectations and beliefs, they are
subject to known and unknown risks and uncertainties that could cause actual
results and outcomes to differ materially from those described in, or implied
by, the forward-looking statements, including volatility in commodity prices;
the accuracy of Unocal's estimates and judgments regarding hydrocarbon
resources and formations and reservoir performance; and other factors discussed
in Unocal's 2004 Annual Report on Form 10-K and subsequent reports filed by
Unocal with the U.S. Securities and Exchange Commission (SEC).

Copies of Unocal's SEC filings are available from Unocal by calling
800-252-2233 or from the SEC by calling 800-SEC-0330. The reports are also
available on the Unocal web site, http://www.unocal.com/. Unocal undertakes no
obligation to update the forward-looking statements in this news release to
reflect future events or circumstances. All such statements are expressly
qualified by this cautionary statement, which is provided pursuant to the safe
harbor provisions of Section 27A of the Securities Act of 1933 and Section 21E
of the Securities Exchange Act of 1934. 

DATASOURCE: Unocal Corporation



CONTACT:  News Media, Christine LeLaurin, [phone], or investors,

Robert Wright, [phone], both of Unocal Corporation



Web site:  http://www.unocal.com/

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