MOECO makes an oil and gas discovery in block L10/43 onshore Thailand

December 4, 2006 Project

Mitsui Oil Exploration Co., Ltd. ("MOECO", Head office: Hibiya Central Bldg. 2-9, Nishi Shimbashi 1-Chome, Minato-ku, Tokyo, JAPAN / President: Mr. Yoshiyuki Kagawa) is pleased to announce that Siam Moeco Ltd. ("SML"), a wholly-owned subsidiary of MOECO and the holder of a 70% interest in Blocks L10/43 and L11/43 onshore Thailand, has made an oil and gas discovery with its 1st exploration well (Arunothai-1) in Block L10/43. The well flowed approximately 1,254bopd (API gravity tentatively evaluated to be 40-45) and 0.72MMcfgd on testing.

SML spudded Arunothati-1 at the Arunothai prospect in July and reached the target depth in late August, after which a series of tubing stem tests were conducted at two oil zones.

The blocks, located next to Block S1 which contains the Sirikit Field, the largest producing oil field in onshore Thailand, are considered to be highly-prospective for crude oil. SML has been conducting exploration activities since January 2004 and will enter the 2nd Obligation Period under the Concession in 2007. There are plans to drill further exploratory wells to assess additional hydrocarbon potential in the blocks and SML plans early production to optimize benefits for all the stakeholders including the Kingdom of Thailand.

The concessionaires of Blocks L10/43 and L11/43 are SML (70%) in the capacity of operator, and GS Caltex Corporation (30%), with the assignment of the 30% interest subject to Thai Government approval.

MOECO is currently active internationally, with key assets in the Gulf of Thailand with a total net daily production of approximately 88,000boepd.