press release

Unocal announces results of Gulf of Mexico exploratory wells

Sugar Land, Texas, March 26, 2004 - Unocal Corporation (NYSE: UCL) today said it has concluded drilling operations on two Gulf of Mexico exploratory wells.

The deepwater Myrtle Beach prospect, located in Green Canyon block 943, and the deep shelf test on the House Payment prospect in Eugene Island block 40 did not encounter commercial quantities of hydrocarbons. Unocal expects to charge the costs of the wells to expense in the first quarter 2004.

The company said the Discoverer Spirit deepwater drill ship is moving from Myrtle Beach to Alaminos Canyon block 859 to drill the Tobago prospect. The Tobago well will test a structure between the Trident and Great White oil discoveries.

In addition to Tobago, Unocal's deepwater Gulf of Mexico drilling plan for 2004 includes an appraisal well on the St. Malo discovery in Walker Ridge block 678 and Sardinia, a lower Tertiary test in Keathley Canyon block 681.

Unocal operated the Myrtle Beach well, with a 25.6-percent working interest. Co-venturers included Exxon Mobil Corporation (27.8%), Amerada Hess Corporation (20%), Pioneer Natural Resources USA, Inc. (10%), Maxus (U.S.) Exploration Company (10%), and another co-venturer (6.6%).

At House Payment, Unocal was operator and held a 50.2-percent working interest. Co-venturers were The Houston Exploration Company (33.3%), and Devon Energy Corporation (16.5%).

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 operations are in North America and Asia.

This news release contains certain forward-looking statements about expected dry hole expenses and exploration drilling plans. These statements are not guarantees of future events or performance. The statements are based upon Unocal's current expectations and beliefs and are subject to a number of known and unknown risks and uncertainties that could cause actual results to differ materially from those described in the forward looking statements, including the risks and uncertainties discussed in Unocal's 2003 Annual Report on Form 10-K (SEC File No. 1-8483) and other reports filed by Unocal with the U.S. Securities and Exchange Commission. Unocal undertakes no obligation to update the information in this news release.

Copies of Unocal's SEC filings are available from the company by calling 800-252-2233. The reports are also available on Unocal's web site, You can also obtain filings from the SEC by calling 800-SEC-0330.

Updated: March 2004