press release

Unocal finds significant oil pay with Indonesia deepwater exploration wells; prepares to drill adjacent prospects

El Segundo, Calif., Sept. 4, 2001 -- Unocal Corporation (NYSE: UCL) today said that its Unocal Rapak, Ltd., subsidiary has drilled two successful exploration appraisal wells on the Ranggas prospect in the southern portion of the Rapak Production-Sharing Contract (PSC) area, offshore East Kalimantan, Indonesia.

Unocal Rapak has drilled two additional wells as a follow-up to the initial discovery announced in January 2001. Both wells encountered significant oil and gas pay.

The Ranggas-2 well encountered 155 feet (47 meters) of net oil pay and 118 feet (36 meters) of net gas pay. The well was drilled to a total depth of 13,661 feet (4,163 meters) in 5,192 feet (1,582 meters) of water. The Ranggas-2 well is located in the southern portion of the Ranggas structure, nearly a mile southwest of the discovery well.

The Ranggas-3 well encountered 306 feet of net oil pay and 123 feet of net gas pay. The well was drilled in 5,368 feet (1,636 meters) of water to a total vertical depth of 13,248 feet (4,038 meters). The well is located 3.4 miles (5.5 kilometers) north of the discovery well in the central portion of the Ranggas structure.

Based on drilling to date, the company estimates the gross unrisked resource potential for the Ranggas structure is between 190 million barrels-of-oil-equivalent (MMBOE) and 650 MMBOE.

"We are extremely encouraged by the significant oil component of the Ranggas discovery," said Charles R. Williamson, Unocal chief executive officer. "Our Kutei basin program has been extremely successful, but until now we have found more gas than oil. Given Ranggas and the 'look-alike' adjacent prospects that we have developed, we are excited about the next phase of our exploration program, which will definitely be oil-focused."

In the next phase of drilling, Unocal Rapak will drill 4-8 wells beginning late in 2001 or early in 2002 to further delineate the Ranggas discovery and test at least two adjacent prospects. The company expects to determine commerciality and the size of the production facilities in this second drilling phase.

Unocal Rapak is operator of the Rapak PSC area. It holds an 80-percent working interest, while Lasmo Rapak, Limited, a subsidiary of ENI, holds the remaining 20-percent working interest.

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 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.

This news release contains certain forward-looking statements about Unocal's future drilling plans, prospects and resource potential. Resource potential is a speculative estimate of ultimate recovery (including non-proved resource) based on engineering, geophysical, and geological studies and may include market risk. 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 2000 Form 10-K and subsequent reports filed with the Securities and Exchange Commission.

Cautionary Note to U.S. Investors: The U.S. Securities and Exchange Commission permits oil and gas companies, in their filings with the SEC, to disclose only proved reserves that a company has demonstrated by actual production or conclusive formation tests to be economically and legally producible under existing economic and operating conditions. Unocal uses certain terms in this news release, such as "resource potential," that the SEC's guidelines strictly prohibit Unocal from including its filings with the SEC. U.S. investors are urged to consider closely the disclosure in Unocal's 2000 Form 10-K (SEC File No. 1-8483). 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, You can also obtain this form from the SEC by calling 800-SEC-0330.

Under the terms of the PSCs, Unocal Indonesia Company and its affiliates, including Unocal Rapak, Ltd., as contractors to Pertamina, the Indonesia national oil company, are entitled to varying shares of the oil and gas produced from commercial discoveries.

Updated: September 2001