2002 年 12 巻 1 号 p. 50-55
Exploration for natural methane hydrate was carried out in the Nankai-Trough offshore Japan at a water depth of 945 m over an 88-day period, from November 1999 to February 2000. This was a national project led by the Ministry of International Trade and Industry (MITI) to seek a new energy source. It was organized by Japan National Oil Corporation (JNOC) in collaboration with Japan Petroleum Exploration Co., Ltd. as the drilling operator. The Nankai-Trough wells were drilled with a deepwater semisubmersible rig. The location was selected where BSR (Bottom Simulating Reflector) is the clearest on the seismic section. Six wells were drilled through the BSR horizon and the hydrate rich formation was confirmed between 1135 m to 1213 m BMSL (below mean sea level) by LWD data, core samples and electric logging data.