press release

Unocal announces gas discovery in Gulf of Thailand

El Segundo, Calif., Dec. 8, 1999 -- Unocal Corporation today said that an exploration well on the Arthit project in the Gulf of Thailand has discovered natural gas and condensate.

The Arthit-15-1X discovery well tested at a combined daily rate of 41 million cubic feet and 1,657 barrels of condensate from 5 zones. The well confirmed net pay of 462 feet (141 meters) in 35 gas-bearing zones.

Located on block 15A in the Gulf of Thailand, the discovery well is 21 miles (35 kilometers) northeast of the Bongkot field, which is operated by PTT Exploration and Production Public Company Limited (PTTEP).

Unocal Thailand, Ltd., holds a minimum 16-percent working interest in the prospect. PTTEP is operator and holds an 80-percent working interest. MOECO Thailand Co., Ltd., holds the remaining 4-percent interest.

"We are extremely pleased with the success of our first exploration well in the prolific, gas-prone Malay Basin," said Randy L. Howard, president of Unocal Thailand. "This successful exploration well increases the prospectivity of the Arthit project (blocks 14A, 15A and 16A), as well as block 52/97, which is located in Vietnam waters east of Arthit and where Unocal has a 70-percent interest. The combined blocks total approximately 1.5 million acres (6,000 square kilometers) and have been closed to exploration for more than 25 years."

The company has estimated the gross unrisked resource potential of the Arthit project at 3 to 6 trillion cubic feet of gas. "The discovery of additional gas resources in the Gulf of Thailand provides continued assurance that there will be ample natural gas supplies to help propel the Kingdom's return to economic growth," Howard said.

Six additional exploration wells are planned for block 15A and 16A, which will be completed by mid-2000. Unocal is one of the world's largest independent oil and gas exploration and production companies, with resource development, power plant and pipeline projects in Asia, the U.S. Gulf of Mexico region and Latin America.

Natural gas is used mainly to produce electricity in Thailand. The gas produced by Unocal Thailand and its co-venturers provides electricity to one of three homes and buildings in the Kingdom. It is also used in the transportation sector, as petrochemical feedstock, and as an industrial fuel.

Forward looking statements and estimates regarding future exploration and production activities and resource potential in this news release are based on assumptions about operational, market, competitive, regulatory, environmental, and other considerations. Actual results could differ materially as a result of factors discussed in Unocal's 1998 Form 10-K report filed with the U.S. Securities and Exchange Commission.

Updated: December 1999