2004 年 69 巻 2 号 p. 214-221
Massive Methane hydrate (hereinafter referred to as "MH") is interpreted to be widely distributed in the offshore region of the Japanese islands. Trial calculations indicate the amount of MH is estimated to be enough to supply the domestic natural gas demand for some a hundred years. The Advisory Committee of the METI (Ministry of Economy, Trade and Industry) prepared "Japan's Methane Hydrate Exploitation Program, July 2001" with the aim of producing natural gas from the MH. The action plan "MH Resources Research and Development" (2001-2016) is currently being carried out.
The existence of MH in sandy beds in the offshore region of the Japanese islands was confirmed for the first time in 2000 through the METI Exploratory Test Well "Nankai Trough".
The well clarified that the net thickness of MH-rich layers is 12 to 14m in total. Several thin MH layers are also present at a depth between 1, 100-1, 140 m deep from the sea surface. Some thicker sand layers (12-14m thick) associated with a submarine fan that are characterized by the high concentration of MH were identified between 1, 140 m and 1, 213 m deep from the sea surface. In the lower interval of these thicker sand layers, each sand bed is less than lm in thickness and was correlated between test wells. Wire line logging with Combinable Magnetic Resonance* (CMR) data showed that the MH saturation was 60 to 80% in the MH containing layer. The bottom depth of high MH concentration deposits coincides with the depth of BSR on the basis of Vertical Seismic profile* (VSP).
*: Sclumberger trademark