山西河东煤田中—南部煤系页岩气储层微观特征

Microscopic characteristics of shale gas reservoirs in middle and southern coal measures of Hedong Coalfield,Shanxi Province

为探讨山西河东煤田中—南部海陆过渡相煤系页岩气储层微观特征,表征储层孔隙结构参数发育特征及影响因素,应用扫描电镜并结合氩离子抛光技术对储层各类孔隙形貌特征进行直观观察研究;借助高压压汞、低温液氮吸附实验测试对泥页岩储层孔径分布、孔体积和比表面积进行间接表征;通过单因素拟合分析及SPSS多因素综合分析表征孔隙结构参数的影响因素。结果表明,页岩中主要发育有机质孔、粒间孔、粒内孔和微裂隙4类孔隙,孔隙形态以四周开放的平行板状孔,细颈广体孔和墨水瓶孔为主,孔隙连通性较好;孔径多为纳米尺度,以微孔和介孔为主,储层孔体积和比表面积发育主要由微孔和介孔贡献;孔体积和比表面积与黏土矿物含量、TOC和R_O呈正相关关系,与脆性矿物含量呈负相关关系;黏土矿物和脆性矿物中,孔体积和比表面积与伊利石、绿泥石、伊/蒙间层和斜长石含量呈正相关关系,与石英、钾长石和高岭石含量为负相关关系。研究结果精细表征了河东煤田中—南部山西组、太原组和下石盒子组煤系页岩气储层微观特征及影响因素,对于河东煤田中—南部地区煤系页岩气资源勘探开发具有一定理论指导意义。

In order to further study the microscopic characteristics of the coal-bearing shale reservoirs in the middle south of Hedong Coalfield,discussion was carried out on the characteristics and influencing factors of reservoir pore structure parameters.In this paper,scanning electron microscopy and argon ion polishing technology were used to describe the characteristics of various reservoirs directly. The pore size distribution,pore volume and specific surface area of the samples were measured by high pressure mercury intrusion and low temperature liquid nitrogen adsorption experiments.The results show that there are four kinds of pores in shale: Organic matter pore,intergranular pore, intragranular pore and micro fissure. The pore size is mainly distributed in the nanometer scale, micropores and mesoporse are dominant,and the pore volume and specific surface area are mainly contributed by micropores and mesopores. The results of single factor analysis and SPSS multi factor analysis showed that the growth of pore volume and specific surface area positively correlated with clay mineral content,TOC and Ro, and negatively correlated with the content of brittle minerals. In clay minerals and brittle minerals. the content of illite,chlorite, interlayer and plagioclase has a positive in fluence. while the content of quartz, potassium feldspar and kaolinite is negative. The research results have some theoretical significance for the exploration and development of coalbearing shale gas resources in the middle and south parts of the Hedong Coalfield,with the study of the microscopic characteristics and influencing factors of the coal-bearing shale reservoirs in the middle-south Xiashihezi Formation Taiyuan Formation.