Influencing factors of surface gas extraction effect in Wangpo minefield of Jincheng mining area

The effect of surface gas extraction in Wangpo minefield of Jincheng mining area is poor. In order to find out the causes and to guide the construction of future surface gas extraction, the occurrence conditions of CBM resources in the study area were analyzed and compared with those of adjacent Chengzhuang minefield where the extraction effect is good, the quality of the produced water was tested, at the same time the fracture forms were observed underground. The comprehensive analysis indicated that the abundance of coal gas resources and the reservoir conditions were the major intrinsic basic factors influencing the gas extraction effect in Wangpo minefield; Great amount of developed collapse columns have destroyed the confining conditions of CBM and enhanced groundwater recharge, resulting in the difficulties in depressurization by water drainage of extraction wells. Underground fracture observation showed that the fractured fractures extended horizontally along coal seams and the weak stress plane of seam roof, inducing the poor effect of fracturing and transformation of the reservoir. It is recommended to study deeply the characteristics of gas occurrence and distribution as well as the development scale of collapse columns in the study area to later construction of surface gas extraction wells.