Unocal Commences Offer to Acquire Pure Resources

Unocal Corporation has commenced its previously announced exchange offer to acquire all of the outstanding shares of Pure Resources common stock that it does not already own.

Unocal, through its subsidiary Union Oil Company of California, currently owns approximately 65 percent of Pure's outstanding common stock. The exchange offer is scheduled to expire on Wednesday, Oct. 2, 2002.

As previously announced, Pure stockholders are being offered 0.6527 shares of Unocal common stock in exchange for each of their shares of Pure common stock. Following successful completion of the exchange offer, Unocal would effect a short form merger of Pure with a Unocal subsidiary. Pure shares held by the remaining public stockholders would be converted into the same consideration paid in the exchange offer, except for shares owned by stockholders who exercise appraisal rights.

If Pure's stockholders choose to tender their shares, and if all Pure stock options vest and are exercised, Unocal would issue approximately 15.6 million shares in the transaction. Completion of the exchange offer is subject to the satisfaction of conditions, including that Unocal own at least 90 percent of the outstanding shares of Pure common stock at the completion of the exchange offer, and other customary conditions.

A prospectus, which is part of the Unocal Registration Statement on Form S-4, and related exchange offer materials, including a letter of transmittal, are being mailed to stockholders of Pure. Investors and stockholders of Pure are urged to read all of these documents carefully. These documents contain important information about the transaction and should be read in connection with making a decision with respect to the exchange offer.

Unocal has filed its Registration Statement on Form S-4 and a Schedule TO with the Securities and Exchange Commission (SEC).