鄂尔多斯盆地东缘中—高煤阶煤储层微观孔隙—裂缝结构表征OA

The development of deep coal reservoirs is the key approach to increasing reserves and produc-tion of coalbed methane.The Benxi Formation 8th coals in eastern margin of Ordos Basin were taken as the research object,based on the coal quality parameter test,experiments such as low pressure CO2 ad-sorption,low temperature N2 adsorption,high pressure mercury injection and micron CT scanning were carried out to characterize the pore-fracture structure of medium-high coal reservoirs with a full scale,the characteristics of pore-fracture structure at different scales were comprehensively evaluated,and the influence of metamorphism degree on the development of pore-fracture at different scales was also dis-cussed.The results show that the coal volume type in the study area is mainly characterized by a dual-peak pattern of micropores and fractures,featuring the coexistence of micropores and fractures,and the pore size is mainly concentrated in the range of 0.3-1.5 nm and greater than 1 000 μm.The average vol-ume of micropores,mesoporous pores,macropores and fractures accounted for 70.8％,16.0％,8.1％and 5.1％of the total pore volume,respectively.Micropores contribute 98.8％of specific surface area and are the main occurrence sites of adsorbed gas.There are significant differences in the pore-fracture structure of middle-high coal reservoirs.With the increase of coal rank,the metamorphism of coal rock was deepened,the volume of micropores increases steadily,and the volume of fractures increases first and then decreases and then increases,while the change of mesoporous and macro pores volume is not obvious.The coal reservoirs with higher coal rank has higher volume proportion of micropores and stronger adsorption.This result provides theoretical and data support for deep coalbed methane potential evaluation and exploration and development in Ordos Basin.