RESERVOIRING MECHANISM OF COALBED METHANE IN SOUTHERN QINSHUI BASIN

Research on the reservoiring mechanism of coalbed methane is the basis of exploration and development of coalbed methane. Based on the data accumulated in various stages of exploration of oil and gas, coal and coalbed methane and in combination with the previous results of research, this paper systematically discusses the reservoiring mechanism of coalbed methane in the southern Qinshui Basin, and analyzes the features of coalbed methane reservoirs, including the spatial geometry of coalbed, the compositions and contents of coalbed methane, poroperm characteristics of the reservoirs, characteristics of adsorption, reservoir pressure and sealing conditions, and the process of reservoiring of coalbed methane, including the generation, migration and accumulation of coalbed methane. It is believed that the Upper Paleozoic coal seams went into peak generation of methane after two stages of coalification in the Indo-Chinese and Yanshan epochs and were strongly adjusted and modified in Himalayan epoch, resulting in the formation of the current coalbed methane pools in the southern Qinshui Basin. In addition to the lithologies of the adjacent rocks and the boundary faults, the recharging, movement, stagnation and discharging of ground water are also key factors which directly control and influence the enrichment of coalbed methane. The current coalbed methane wells of high capacity are basically located in the stagnant zone of groundwater in the study area.