Physical Characteristics And Evaluation Of Coalbed Methane Development Potential Of Medium-rank Coal Reservoirs In Shanxi Province

The high-rank coal reservoirs characteristics in Shanxi Province have been studied extensively,and the commercial development of CBM in high-rank coal reservoirs has also been realized.However,the research on the medium-rank coal reservoirs characteristics is still weak.The medium-rank coal reservoirs only show good development results in Baode and Liulin areas of Hedong coalfield.In this paper,18 coal samples were collected from Carboniferous-Permian coal measures in Shanxi Province.Based on the matching experiments/tests of lithotype,coal quality,isothermal adsorption,high pressure mercury intrusion and pulse permeability,etc.Combining with the testing results of my superviser’s research group on the medium-rank coal reservoirs characteristics in Shanxi Province,the theoretical knowledge of coal geology,energy geology and coalbed methane geology is used.By means of the combination of underground observation,coal sample test and result data analysis,this paper systematically analyzed the distribution rule,pore and permeability characteristics,adsorption and gas content characteristics of medium-rank coal reservoirs in Shanxi Province,and discussed the influencing factors.The evaluation system of CBM development potential which dominated by the physical properties of coal reservoirs is established.Analytic hierarchy process(AHP)was used to evaluate and rank the development potential of CBM in medium-rank coal reservoirs in different mining areas of Shanxi province.The results show that the medium-rank coal reservoirs in Shanxi Province are distributed in all the Datong,Huoxi and Ningwu coalfields,most of the Hedong coalfields(except southern Xiangning),Qinyuan and Xishan coalfields,and the lithotype of the medium-rank coal reservoirs are mainly semibright coal and semidull coal coal,with vitrinite as the main component,inertinite as the second and exinite as the lowest.The areas with high gas content are concentrated in the south of Ningwu coalfield,the middle and north of Hedong coalfield,the eastern margin of central and South China,the Qingxu-Jiaocheng area of Xishan coalfield and Qinyuan mining area of Qinshui basin.The gas content is positively correlated with burial depth and maceral.Langmuir volume is positively correlated with coal rank,and negatively correlated with water content,ash yield and volatile yield.The medium-rank coal reservoirs has the most developed micropore,the worst mesopore,the lower porosity as a whole,and the negative correlation between permeability and burial depth.Analytic hierarchy process(AHP)evaluation results show that the development potential of CBM in medium-rank reservoir is the best in Liulin mining area,and the others are Baobian mining area,Xishan Gujiao mining area,Ningwu Xuangang mining area,Jingle Lanxian mining area,and Pingshuonan mining area is the worst.