H. Takahashi¹, T. Yonezawa², and Y. Takedomi³

¹Japan Petroleum Exploration Co., Ltd., Tokyo Japan
²Japan National Oil Corporation, Tokyo Japan
³Ministry of Economy, Trade and Industry, Tokyo Japan

ABSTRACT: MITI Nankai-Trough Gas Hydrate Drilling Program – An Overview of Field Operations

Methane hydrate accumulating in deepwater sediments and Arctic permafrost has been expected as one of the future energy resources since its amount is estimated as twice that of conventional hydrocarbon resources 1 . It has heightened the interest of Japan which produces little oil and is surrounded by deepwater. Ministry of International Trade and Industry (MITI) established its evaluation project in 1995, and declared to drill an exploration well offshore Japan in 1999. The well was intended to explore not only the hydrate, but also the conventional oil and gas at a deeper Tertiary prospect, should prospects overlap.

Japan National Oil Corporation (JNOC) immediately launched all preparation works and organized 5-year collaborative R & D studies with ten (10) Japanese private companies to perform the challenging exploration efficiently. Based on the interpretation of conventional and high resolution seismic surveys carried out in the Nankai-Trough area in 1996 and 1997, the drilling location was selected at 50 km south of Shizuoka prefecture at 950 m water depth, where the BSR (Bottom Simulating Reflector) is clearly developed at 1240 m (290 m below sea floor) on the seismic section, and there is Tertiary oil/gas prospect down to 2800m. shows the equilibrium curve of methane hydrate and the estimated in -situ temperature of the well. The two curves crosses at depth of 1240 m. Thus, the BSR at 1240 m on the seismic section was expected to be the base of the hydrate zone.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado