press release

Unocal announces significant oil discovery in deepwater Gulf of Mexico

Sugar Land, Texas, July 24, 2001 - Unocal Corporation (NYSE: UCL) today said that its deepwater exploratory well on the Trident prospect in Alaminos Canyon block 903 encountered more than 300 feet of hydrocarbon-bearing pay section and additional zones of interest. Preliminary evaluation indicates reservoir fluid of 40+ API gravity.

Trident is located 185 miles southeast of Corpus Christi, Texas, in 9,687 feet of water. The well was drilled to a total depth of 20,500 ft. in 66 days at an estimated gross cost of $34 million.

"We are obviously excited by the initial results at Trident. However, we will need to perform additional appraisal and evaluation work in order to determine ultimate commerciality," said Mike Bell, vice president of Unocal's Deepwater USA business unit.

"We are especially encouraged by the thickness of the hydrocarbon columns we penetrated, the apparent quality of the oil, and the size of the structure we are testing -- up to 10,000 acres in structural closure," Bell said.

The Trident prospect covers seven blocks in Alaminos Canyon. Unocal is operator and has a 59.5-percent working interest in the prospect. Co-venturers include Chevron U.S.A. Production Company (NYSE: CHV), 15%; Ocean Energy, Inc. (NYSE: OEI), 12.75%; Agip Petroleum Co., the American subsidiary of Eni SpA (NYSE: E), 8.55%; and Phillips Petroleum Inc. (NYSE: P), 4.2%.

The company will conduct further evaluation of the data from the Trident well and expects to begin an appraisal drilling program in 2002 based on the evaluation.

The Discoverer Spirit drillship is expected to move to Green Canyon block 782 to drill an appraisal well on the Mad Dog discovery, which is operated by BP. The discovery was announced in April 1999, and development sanction is expected later this year.

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 exploration and production operations are located in North America (Gulf of Mexico region, Alaska and Canada) and in Asia (Thailand, Indonesia, Myanmar and Bangladesh). The company is also pursuing exploration programs in West Africa and Brazil.

Unocal currently holds leases on 232 blocks in the Gulf of Mexico deepwater, with 165 blocks located in the ultra-deepwater, or greater than 5,000 feet of water. The Discoverer Spirit drillship is capable of operating in water depths up to 10,000 feet.

This news release contains certain forward-looking statements about Unocal's future drilling plans and the results of geological analysis. These statements are not guarantees of future 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. Actual results could differ materially as a result of factors discussed in Unocal's 1999 Form 10-K and subsequent reports filed with the Securities and Exchange Commission. Copies of the company's SEC filings are available from the company by calling 800-252-2233. The reports are also available on the Unocal web site, www.unocal.com.

Updated: July 2001