press release

Unocal unit announces successful delineation drilling in the Gulf of Thailand

Bangkok, Oct. 1, 2004 -- Unocal Thailand, Ltd., today said that it has completed successful delineation drilling in the South Gomin operating area, comprising approximately 319 sq. km. located in the concession Block 13 in the Gulf of Thailand.

The delineation drilling program involved three follow-up wells that encountered 195, 183, and 95 feet of net natural gas pay. The South Gomin field was discovered in 1998 when the South Gomin-1 well was drilled and encountered a total of 269 feet of net gas/condensate pay. The first production from the South Gomin field is expected in late 2006.

"The original South Gomin well established that a working petroleum system was present. As the Thai market is now ready for more gas, we have confirmed the commerciality of the area with three very successful follow-up wells," said Tara Tiradnakorn, Unocal Thailand President.

Unocal is currently in discussions with Thai agencies to produce increased volumes of gas over current contracted volumes after the third pipeline is installed to transport natural gas from the Gulf of Thailand fields to shore facilities. Once agreements are reached on timing and volumes, Unocal anticipates executing an accelerated delineation drilling program of 30 to 45 wells over the period 2005 to 2007.

"The accelerated delineation program is expected to confirm additional reserves of domestic gas to further promote the Kingdom's energy independence, increase Thailand's reserves to production (R/P) ratio as well as to provide feedstock for the forthcoming expansion of the Thai petrochemical industry, the so called Third Wave," Tara added.

The drilling campaign is part of Unocal's effort to alleviate the impact of the current high oil prices and long-term commitment to the exploration and development of domestic energy resources to help Thailand meet its increasing future demand.

The South Gomin field is part of the Unocal 3 gas contract area where Unocal Thailand is operator and holds a 71.25% working interest. Other working interest owners include MOECO (23.75 %) and PTTEP (5.00%). Unocal and partners also produce gas from three other contract areas (MOECO in all 3 and PTTEP and Amerada Hess in 1) that in total supply about 60 percent of Thailand's domestic gas of which 70 percent is used for power generation.

About Unocal Thailand

Unocal Thailand is a wholly owned subsidiary of Unocal Corporation, one of the world's leading independent natural gas and crude oil exploration and production companies. Unocal's principal oil and gas activities are in Asia and North America.

This news release contains forward-looking statements about matters such as Unocal's assessment of hydrocarbon formations and potential resources, drilling and development plans, future production timing, and negotiations, sales and transactions with third parties. Although these statements are based upon Unocal's current expectations and beliefs, they are subject to known and unknown risks and uncertainties that could cause actual results and outcomes to differ materially from those described in, or implied by, the forward-looking statements, including volatility in commodity prices and the effectiveness of Unocal's hedging program; Unocal's ability to develop and produce the resources discussed in this release in a timely and cost-effective manner; local demand, infrastructure and the distance to markets for Unocal's hydrocarbon production; the accuracy of Unocal's estimates and judgments regarding hydrocarbon resources and formations; adverse geological and other operational factors; the extent of Unocal's operating cash flow and other capital resources available to fund its capital expenditures; international and domestic regulatory, political, and economic factors; negotiations with, and performance by foreign government entities, joint venture partners, independent contractors, equipment suppliers and other third parties; and other risks and uncertainties discussed in Unocal's 2003 Annual Report on Form 10-K, as amended, and subsequent reports filed by Unocal with the Securities and Exchange Commission (SEC File No. 1-8483). Copies of Unocal's SEC filings are available from Unocal by calling 800-252-2233 or from the SEC by calling 800-SEC-0330. The reports are also available on the Unocal web site. Unocal undertakes no obligation to update the forward-looking statements in this news release to reflect future events or circumstances. All such statements are expressly qualified by this cautionary statement.

Updated: October 2004