Analysis of productivity differences in vertical coalbed methane wells in the Shizhuangnan Block, Southern Qinshui Basin, and their influencing factors

Coalbed methane wells in the Shizhuangnan Block exhibit significant productivity differences. The reasons were determined based on the impact analysis of geological factors and drainage strategies on production capacity at 82 wells. Grey relational analysis was further utilized to quantitatively analyze the correlation degree of geological parameters to production characteristics. It is found that the main reason for wells with high water production is the ingress of external water, i.e. connecting adjacent aquifer by natural faults or artificial fractures. And aquifer characteristics, especially thickness of aquifer has the greatest influence on the water production, followed by pore connectivity, porosity, and shale content. For the wells that have not been affected by external water, the gas productivity differences are mainly affected by reservoir conditions and drainage strategies. Finally, an analytical process was proposed to provide theoretical support for rational production of coalbed methane wells.