常见黏土矿物电镜扫描微孔隙特征与甲烷吸附性

野外采集的黏土岩的电镜扫描图像分析显示，黏土矿物孔隙分布于颗粒之间和颗粒内部板片自然错断处，前者形态不规则，后者呈楔形或面状缝隙。具层间结构的蒙脱石层内发育纳米级连通孔隙。蒙脱石微孔隙最为发育，伊-蒙混层黏土次之，其粒间孔和层面缝隙为20~100 nm，层内连通孔隙小于50 nm。高岭石黏土主要发育20~100 nm的粒间孔。伊利石和绿泥石晶体颗粒较大，以微米级孔隙为主。吸附实验所反映的各种黏土矿物甲烷吸附能力与电镜扫描反映的微孔发育程度相吻合，指示泥页岩中的纳米级微孔在一定程度上决定着泥页岩的比表面积和气体储存能力。黏土岩的孔隙发育与岩石成因和成岩演化有关，孔隙大小主要受黏土颗粒大小的控制。

Micro-pore characteristics and methane adsorption properties of common clay minerals by electron microscope scanning

The scanning electron microscope(SEM) image analysis of clay rocks collected from the field demonstrates that pores of clay minerals are distributed among grains and at natural fractures of intragranular plates,where the former has an irregular shape and the latter shows a wedge-shaped or plane gap.Connected nano-pores develop in layers of the smectite that has interlayer structures,micropores are most frequently found in smectite clay and secondly in illite and smectite mixed layers.In clay minerals,the size of intergranular pores and plane gaps ranges from 20 to 100 nm and connected pores within layers are less than 50 nm in size.Kaolinite clay mainly has intergranular pores with a size of 20-100 nm.Illite and chlorite are of larger crystal particles and dominated by micropores.The methane adsorption capacity of various clay minerals determined by experiments is consistent with the degree of micropore development measured by SEM,indicating that dominant nano-pores in shales,to a certain extent,determine the surface to volume ratio of shales as well as the storage capacity of shale gas.The porosity development of clay rocks is related to the genesis and diagenetic evolution of shales,while the pore size is controlled mainly by the particle size of clay minerals.