press release

Unocal extends offshore Vietnam exploration acreage

Hanoi, Vietnam, Sept. 28, 1998 - Unocal Corporation today said its Unocal Vietnam Exploration, Ltd., subsidiary signed an agreement with PetroVietnam to supplement the Block B Production Sharing Contract area with the additional acreage of Block 48/95.

The Block B extension includes approximately 9,150 square kilometers (2.3 million acres) of additional lands located directly north of Block B, bringing the new total for the block to approximately 14,700 square kilometers (3.6 million acres). Block B was awarded to Unocal and its coventurers in 1996.

Map of Block B

The company announced a significant discovery with its first exploration well in the Kim Long prospective trend in Block B in December 1997. Two drill stem tests of the B-KL-1X exploration well yielded a combined rate of 52.9 million cubic feet per day of gas from Miocene age sands. Several other potential hydrocarbon prospects have been identified along the Kim Long trend.

"The supplemental acreage will improve the opportunity for the successful exploration of the Kim Long prospect, which extends into the new area," said Darcel Hulse, president of Unocal Asia-Pacific Ventures, Ltd. "We now plan to acquire 3D seismic data for the entire prospect in one operation."

Hulse added that the economies of scale continue throughout the entire exploration phase. "More cost-effective exploration will enable Vietnam to quantify its natural gas resources more quickly and efficiently," he said.

"Unocal Thailand's long experience and expertise in drilling in the difficult geological formations of the Gulf of Thailand give added benefit to our work in Vietnamese waters," Hulse said. The Thailand operation (Unocal, 64% net working interest), producing since 1982, has drilled over 1,100 wells and has installed 78 platforms in the Gulf. Current gross production is nearly one billion cubic feet per day of natural gas.

Unocal Vietnam has a 45 percent working interest and is operator for the new acreage. Repsol Exploracion Vietnam S.A. (a subsidiary of Repsol, S.A.) holds a 30 working interest; and Moeco Vietnam Petroleum Co., Ltd. (a subsidiary of Mitsui Oil Exploration Co., Ltd.), holds 25 percent. PetroVietnam has an option to participate with a 15-percent interest. If exercised, PetroVietnam's options would reduce the other participants' interests proportionately.

Unocal is a leading global oil and gas exploration and production company with significant pipeline and power plant project developments worldwide.

Forward-looking statements, including estimates of future exploration and development activities, in this news release are based on assumptions concerning geology, drilling success, costs, market conditions, competition, and other considerations. Actual results could differ materially.

Updated: September 1998