沁水盆地南部3号煤层含气量主控地质因素分析

Analysis of 3th Coal Seam's Main Controlling Geological Factors of Gas Content in Southern Qinshui Basin

以沁水盆地南部四个矿区不同深度的3号煤岩样品为研究对象,采用压汞、低温液氮吸附、显微镜和扫描电镜等试验方法对煤样的孔径、裂缝和孔隙连通性、渗透性以及吸附性进行表征,结合研究区的构造特征、储层特征以及水动力特征,研究该地区3号煤层含气量的主控地质因素。研究区处于一个大型复式向斜构造上,3号煤层煤样总比表面积和总比孔容积与煤层埋深呈负向关系。煤岩类型以半亮煤为主,镜质组含量较高,生气能力较强,顶底板密封性较好。盆地接受大气降水,从向斜翼部流向轴部,有效阻止了煤层气的逸散。研究结果表明,该区3号煤层含气量主控地质因素包括:煤岩类型、孔裂隙结构、水动力特征以及顶底板封闭性,煤层气的富集是上述几项地质因素耦合作用的结果。

In the study of the coal samples from four mines at different depths in southern Qinshui Basin, use the test methods of mercury, low temperature nitrogen adsorption, microscopy and scanning electron microscopy to characteristic the aperture, cracks and pore connectivity, permeability and adsorption of the coal samples. Com- bined with the structural characteristics and hydrodynamic characteristics of the study area to study the 3th eoalbed＇ s main control geological factors of gas content of the region . The study area in a large syncline structure and the 3th coal seam specific surface area and pore volume has negative relationship with the depth increased, coal types give priority to semi-bright coaX, vitrinite content is high, has strong gas production ability and better tightness of roof and floor, the basin accept atmospheric precipitation, flows from the syncline wing shaft portion, which ef- fectively prevent the escape of CBM. The results showed that the main geological factors of 3th coalbed in this area include ： coal rock type, pore fissure structure, hydrodynamic characteristics and closed roof and floor, enrichment of CBM is a result of the coupling of several geological factors.