Mitsui Oil Exploration Co., Ltd.("MOECO") is pleased to announce that MOECO Tuna E&P Co., Ltd.(MTE), a subsidiary of MOECO, transferred a 15% interest in Tuna Block in the eastern Natuna Sea, Indonesia to GS Caltex Corporation, a South Korean company on February 1st, 2011. The relevant interest owners in the block are as follows.

■ Before 1 February 2011

Interest owner	Interest
Premier Oil Tuna B.V. (Operator)	65.0％
MOECO Tuna E&P Co., Ltd.	35.0％

■ After 1 February 2011

Interest owner	Interest
Premier Oil Tuna B.V. (Operator)	65.0％
MOECO Tuna E&P Co., Ltd.	20.0％
GS Caltex Corporation	15.0％

MTE is engaged in exploration for crude oil and natural gas. On 5th January, 2011, Japan Oil, Gas and Metals National Corporation (JOGMEC) granted the equity capital finance to MTE covering up to 75% of the exploration expenditures incurred by MTE.