press release

Spirit Energy 76 participates in significant deepwater discovery

Sugar Land, Texas, March 17, 1999 -- Spirit Energy 76, Unocal Corporation's U.S. Lower 48 exploration and production unit, today said that the exploratory well drilling the Mirage prospect in the Gulf of Mexico deepwater is a significant oil discovery. Spirit Energy holds a 25-percent working interest.

Vastar Resources, Inc. (NYSE: VRI) owns 75-percent working interest and is the operator. Vastar estimates the well encountered approximately 300 feet of net pay.

"We are encouraged by the initial results of this first well in the Mirage prospect," said John T. Donohue, president of Spirit Energy 76. "This discovery is an important step forward in proving the commerciality of this prospect and delivering value for our deepwater program."

The company said it is too soon to estimate the extent of the discovery. Additional drilling will be conducted to further evaluate the find.

"The preliminary data on Mirage is very encouraging," said David A. Johnson, vice president of exploration at Spirit. "It is too early to assess the total field potential. However, we do know that the main pay zones in Mirage correspond to the most productive zones of the adjacent Mars and Ursa fields.

"Although we are not ready to sanction a development at this time, we believe that further appraisal drilling will deem this discovery a commercial development," Johnson said.

The Mirage drilling program included an initial well that reached a depth of 16,600 feet and a sidetracked well that reached a depth of 22,435 feet, making it the deepest well drilled to date in the Mars basin. Well conditions prevented the sidetracked well from reaching additional deeper objectives.

The well was drilled in 3,927 feet of water, approximately 80 miles south-southeast of Venice, La., on Mississippi Canyon block 941. It has been temporarily abandoned.

Spirit Energy 76, Unocal Corporation's U.S. Lower 48 exploration and production unit, has major operations onshore in Texas and Louisiana and on the Gulf of Mexico shelf, in addition to a significant presence in the Gulf of Mexico deepwater.

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.

Forward-looking statements regarding exploration activities, drilling results and resource potential in this news release are based on assumptions concerning 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 Securities and Exchange Commission.

Updated: March 1999