MOECO agrees to purchase Thailand Oil and Gas Assets from Pogo

June 20, 2005 Project

Mitsui Oil Exploration Co., Ltd. ("MOECO", Head office: Hibiya Central Bldg. 2-9, Nishi Shimbashi 1-Chome, Minato-ku, Tokyo, JAPAN / President: Mr. Junji Sato) is pleased to announce it has entered into a Stock Purchase Agreement with Pogo Producing Company of the United States of America and their affiliate Pogo Overseas Production B.V. ("Pogo") to purchase Pogo's Thailand assets jointly with PTTEP Offshore Investment Company Limited (PTTEPO), a wholly-owned subsidiary of PTT Exploration and Production Public Company Limited of Thailand. Pogo's Thailand assets consist of a 46.34% interest in the B8/32 Concession and the adjacent Block 9A Concession located in the Gulf of Thailand. The purchase price is US$820 million in cash, of which MOECO will contribute approximately 40% and PTTEPO approximately 60% with MOECO and PTTEPO each acquiring interests in the assets in the same proportion. MOECO's interests in the assets are to be held through its wholly-owned subsidiary, MOECO International B.V.

The Concessions are located offshore about 230km south of Rayong and Chevron is the operator with a working interest of approximately 51%. Recent daily production from the Concessions in 2005 has averaged at about 59,200 barrels of crude oil and 240 million cubic feet of gas.

The transaction is expected to close in the third quarter of 2005, subject to receipt of necessary approvals.

Together with Unocal Thailand, Ltd. ("Unocal") and other partners, MOECO has significant interests in operations in the Gulf of Thailand with an average working interest of approximately 20% in various concessions and under four Gas Sales Agreements. Currently, total daily production from these operations is approximately 1,200 million cubic feet of natural gas (or 200,000 barrels oil equivalent), 40,000 barrels of condensate and 30,000 barrels of crude oil. The volume of natural gas produced in these projects accounts for about 60% of all domestic gas production in Thailand. MOECO's share of production under these projects amounts to approximately 60,000 barrels oil equivalent per day, making MOECO the third largest producer of natural gas, condensate and crude oil in Thailand, next only to Unocal and PTTEP. On the onshore side, MOECO is expanding its operations conducting exploration activities in its capacity as operator in two blocks.

Upon closing, in addition to greatly enhancing MOECO's interests in Thailand, the acquisition will significantly improve the balance of MOECO's production portfolio with a significant increase in the proportion of crude oil production.

MOECO continues to strive to enhance its position as a reliable and respected participant in the global exploration and production industry through its increased commitment in the Kingdom of Thailand and pursuit of other international growth opportunities.