Geological Control Of CBM Productivity Difference In Lu'an Mining Area

This paper takes Lu'an mining area in the eastern margin of Qinshui Basin as the research object.Based on the mine geological report,coal exploration borehole data and CBM evaluation well data.Combined with the experimental test data of No.3 coal samples in the study area,the paper comprehensively analyzes the physical properties of No.3 coal,such as buried depth,coal thickness,coal quality,pore fracture characteristics,coal structure,reservoir pressure,gas bearing property and permeability,and discusses the geological control factors of CBM enrichment law.In this paper,the productivity characteristics of coalbed methane wells are studied,and the key geological factors affecting the productivity of coalbed methane wells in Lu'an mining area are explored by using the grey correlation analysis method.The results show that the key geological factors affecting CBM productivity in the study area are gas content,coal structure and reservoir pressure gradient.The average gas content of No.3 coal reservoir in the study area is 9.78 m3/t,and mainly distributed in 6 ? 10 m3/t.the gas content of No.3 coal seam in the study area is gradually increasing from south to North and from east to west.The gas content of coal reservoir is more than 9 m3/t,and the proportion of middle and high production wells in Lu'an mining area increases significantly.The coal structure in the southern part of Ergangshan fault and the northern part of Wenwangshan fault is better,mainly primary and cataclastic coal.The coal structure in the middle area of Ergangshan fault and Wenwangshan fault is poor,and structural coal is the main coal.With the gradual improvement of coal structure,the overall gas production of CBM wells is on the rise.No.3 Coal Seam is an under pressure reservoir with an average reservoir pressure gradient of 0.354 MPa/100 m in Lu'an mining area.The reservoir pressure gradient is characterized by "low in the middle and high in the north and south sides".The reservoir pressure gradient of high production well is obviously higher than that of middle production well,low production well and ultra-low production well.The above three geological factors are further discussed,and the quantitative indexes of favorable production areas are established.The primary structure coal seams with reservoir pressure gradient greater than 0.4MPa/100 m and gas content greater than9m3/t are selected as the class I area of favorable production area.Class I area is mainly distributed in the northwest of Wuyang coal mine and the middle of Yuwu coal mine.There are 75 figures,22 tables and 126 references in this paper.