press release

Unocal announces discovery in Northwest Territories, Canada

Sugar Land, Texas, March 30, 2005 - Unocal Corporation (NYSE: UCL) today said its Canadian subsidiary, Northrock Resources Ltd., has made a hydrocarbon discovery on the Summit Creek prospect in the Central Mackenzie Valley area of the Northwest Territories in Canada.

Northrock Resources recently concluded this winter's program which was comprised of completing and testing the Summit Creek B-44 discovery well and drilling an exploration well, Sah Cho L-71, to test a separate structural closure.

The Summit Creek B-44 well spud on Jan. 16, 2004, and was drilled to a depth of 10,053 feet in 63 days. The well was suspended in late March 2004 with a completion and testing program planned for January through March 2005.

Testing of the Summit Creek B-44 well confirmed several productive intervals within a gross hydrocarbon column of over 600 feet. Two separate intervals were successfully perforated and flow tested for periods of 18 and 39 hours respectively. Each zone produced at rates of approximately 10 million cubic feet per day (mmcfd) of natural gas and more than 3,000 barrels per day (bpd) of light volatile oil or condensate with flowing well head pressures of 900 -1,100 psi. One of the zones also produced approximately 1,000 bpd of water.

The Sah Cho L-71 well spud Jan. 21, 2005, and was drilled to a total depth of 12,050 feet in 43 days. Hydrocarbons were encountered at L-1; however, open hole testing did not establish commercial flow rates. The well was cased to TD and has been suspended.

"While the results of this winter's program are encouraging, additional work will be necessary to assess the commercial viability of this emerging play," said David Pearce, Northrock's president.

The program area is located about 35 miles south-southwest of the town of Tulita and 45 miles from the existing Enbridge Oil Pipeline and the proposed Mackenzie Valley Gas Pipeline route.

Northrock Resources is the operator and holds a 32.5-percent working interest in the Summit Creek and Sah Cho prospects. Other working interest owners in the Summit Creek well are Husky Oil Operations Limited, 29.4775 percent; EOG Resources Canada Inc. (NYSE: EOG), 26.3975 percent; Pacific Rodera Energy Inc. (TSX-V: PRD), 6.625 percent; and International Frontier Resources Corp. (TSX-V: IFR), 5 percent.

Other working interest owners in the Sah Cho well are Husky Oil Operations Limited, 32.5 percent; EOG Resources Canada Inc., 23.375 percent; Pacific Rodera Energy Inc., 6.625 percent; and International Frontier Resources Corp., 5 percent.

This news release contains forward-looking statements about matters such as drilling, development and other plans for future operations. 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; the accuracy of Unocal's estimates and judgments regarding hydrocarbon resources and formations and reservoir performance; and other factors discussed in Unocal's 2004 Annual Report on Form 10-K and subsequent reports filed by Unocal with the U.S. Securities and Exchange Commission (SEC).

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, which is provided pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934.

Updated: March 2005