我が国の炭層ガス資源量とその温暖化対策への活用 : 新しいガス・ソース+CO_2シンクとしての深部石炭層(<総説特集>天然ガス需給情報最先端-資源の行方をどう読むか?-)

概要

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Recent systematic exploration of oil and natural gas by Japan National Oil Corporation and other oil companies revealed that huge volumes of coal seams lie in the depths of Paleogene and Cretaceous sedimentary basins in central Hokkaido, off the Pacific coast of northeastern Honshu and northwest of Kyushu. Deep unmineable coal seams and coaly shale layers may provide possible sink for CO_2 sequestration and source for coalbed methane. Unmineable coal seams deeper than -1,200m and shallower than -3,000m in Japan may exceed 300 Gtons that may store 10 Gtons of CO_2 and produce 3 Tm^3 of coalbed methane. Very deep unmineable coal seams deeper than -3,000m in Japan are estimated to exceed 3 Ttons, which may contain 24 Tm^3 of coalbed. CO_2 sequestration potential of very deep unmineable coal seams deeper than -3,000m are estimated to exceed 100 Gtons in Japan. Huge volumes of deep unmineable coal seams may not only provide potential sinks for CO_2 but also untapped enormous energy resources. Injected pure CO_2 behaves readily as a supercritical fluid around injection wells in deep coal seams. By the supercritical CO_2-enhanced coal seam gas recovery (EGR) and in situ fire-free microbial gasification of coal, deep unmineable coal seams may provide CO_2-sink and methane source for the CO_2 emission-free closed-circuit power plant. New type of "coal mine" with borehole mining method is proposed to develop "deep unmineable coalbeds".
2006-02-20