Mitsui Oil Exploration Co., Ltd. (三井石油開発株式会社, Mitsui Sekiyu Kaihatsu Kabushiki-gaisha) (MOECO) is an oil exploration subsidiary of Mitsui & Co. that specializes in natural gas. It has its headquarters in the Hibiya Central Building in Nishi-Shinbashi, Minato, Tokyo.It was one of 17 Mitsui companies that were spun off on July 19, 1969.Its core areas are Thailand, where it drills principally in the Gulf of Thailand in conjunction with Chevron, and Vietnam and Cambodia.