著者

大賀 光太郎 本位田 篤生

出版者

石油技術協会

雑誌

石油技術協会誌 (ISSN:03709868)

巻号頁・発行日

vol.73, no.6, pp.487-495, 2008 (Released:2011-02-22)

参考文献数

9

被引用文献数

2

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JCOP (Japan CO2 Sequestration in Coal Seams Project) has been commenced since JFY2002 with full subsidy from Ministry of Economy, Trade and Industry. Yuubari area of Ishikari coal field in Hokkaido was selected as the most suitable pilot test field, because the coal seams of this area are gassy and permeable.The preliminary field experiment was designed to investigate technical and economical feasibility of storing CO2 in coal seam until end of JFY2007.Injection well (IW-1) was drilled in the end of 2003, production well (PW-1) was drilled in the summer of 2004. The distance in the coal seam between the vertical injection well (IW-1) and the deviated production well (PW-1) was about 65m.CO2 injection and CH4 production tests were carried out from the end of this August to the end of October, 2007. From the measurement results, gas and water production rates were observed lower than estimated rates. The gas production rate increased gradually after carbon dioxide injection and then it reached the peak. After stopping injection, gas production rate decreased gradually to the initial gas production level. It is seems that this increase was due to the carbon dioxide injection.CO2 injection rate were also observed lower than estimated rate. History matching was carried out using the measured water production rate in 2005. From the results of history matching, these measured gas production rates were in agreement with calculation results. At that calculation, bottom of pressure of production well was 9MPa and permeability around the injection well was 0.13md. The high bottom hole pressure of production well shows that production damage is occurred. It is considered that perforation holes or cleat of coal plugged with fine coal particles might have caused this production damage. Two reasons for the decrease of permeability around injection well can be considered. One is that the gap of the coal cleats was reduced by the swelling of coal matrix due to CO2 adsorption. The other is that coal cleat was plugged by fine coal particles. From the measurement of gas content of coal in this test, it is conformed that gas content of coal seams in Ishikari coal field are in highest level. If the above mentioned problems on production damage is solved, CO2 injection into the coal seam and development of CBM will be commercialized soon.