press release

Unocal begins natural gas, condensate production from Trat field

El Segundo, Calif., Sept. 3, 1999 -- Unocal Corporation today said its Unocal Thailand, Ltd., subsidiary has started natural gas and condensate production from the Trat field in the Gulf of Thailand.

Daily gross production from the Trat field is currently 70 million cubic feet of natural gas and 2,100 barrels of condensate from five wells -- including Trat A-07, the company's first horizontal well in the Gulf. The field is located in block 11, northeast of the Erawan field.

Unocal plans to install three additional well platforms in the central Trat area, where gross recoverable gas resources are estimated about 240 billion cubic feet. Because of Trat's high resource potential, Unocal designed the Trat-A platform to accommodate 18 wells, as opposed to 12 on conventional offshore platforms the company has built in the Gulf of Thailand.

"We are drilling horizontal wells in the Trat field to help us reach and produce gas resources more efficiently," said Randy Howard, president of Unocal Thailand. "One successful horizontal well can have the productivity of several conventional wells."

Howard noted that horizontal drilling could be applied in cases with appropriate geologic structures, citing certain condensate-rich reservoirs and untapped zones in previously developed reservoirs. "Our approach is to blend state-of-the-art geophysical prospecting techniques with low-cost development technologies in the Gulf of Thailand," he said.

Howard went on to say, "Reasonably-priced indigenous natural gas, available in plentiful volumes, is a very efficient and clean-burning fuel for the Kingdom. Even after 18 years of production, Unocal continues to use innovative exploration and production technologies to find and provide more and more natural gas to meet Thailand's growing demand."

Unocal Thailand (71.25% working interest) is the operator of the Trat field for its co-venturers Mitsui Oil Exploration Co., Ltd. (23.75%) and PTT Exploration and Production Public Company Limited (5%).

Unocal is operator for 13 natural gas and condensate fields in the Gulf of Thailand. Daily gross production from the Unocal Thailand-operated fields is currently averaging nearly one billion cubic feet of natural gas and 33,000 barrels of condensate.

In August, Unocal Thailand started production from the Pailin field, also in the Gulf of Thailand. Gross production from Pailin is expected to reach 165 mmcf per day in the fourth quarter. The company estimates gross producible gas resources in the Pailin field at approximately 2 trillion cubic feet. About one-half of the net recoverable gas has been proved. Unocal Thailand, Ltd., is operator of the Pailin field and holds a 35 percent working interest. Co-venturers include PTT Exploration and Production Public Company Limited (45%), Amerada Hess (Thailand) Limited (15%), and MOECO Thai Oil Development Co., Ltd. (an affiliate of Mitsui Oil Exploration, 5%).

Production from the Unocal-operated fields in the Gulf of Thailand account for about 60 percent of Thailand's indigenous natural gas production. Of the total gas produced in Thailand, more than 75 percent is used to generate electricity. The remainder is used as industrial fuel, transportation fuel, cooking gas, and petrochemical feedstock.

Forward looking statements and estimates regarding exploration and production activities and costs, future production levels, and resource potential in this news release are based on assumptions about market, competitive, regulatory, environmental, operational 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: September 1999