Characteristics of nano-pore structure of clay minerals in shale and its effects on methane adsorption capacity

It is important for understanding the occurrence and migration output of shale gas to find out the pore struc- ture characteristics of clay minerals and their effects on methane adsorption. This paper focuses on the study of low temperature liquid nitrogen and isothermal adsorption of methane based on montmorillonite,illite and chlorite in shale. The results show that:① The clay mineral pore structure is complex,which is mainly composed of nanopores,and the pore aperture 2-50 nm provides the main pore volume and surface area. In detail,the mesoporous of montmorillonite, illite and chlorite respectively accounted for 81. 45% ,71. 34% and 75. 36% of the total pore volume and 88. 70% , 87. 70% and 90. 65% of specific surface area. The hole (2 -50 nm) pore constitute an important space of methane occurrence. ② Clay minerals mainly develop the slit pores in parallel plate with small amount of ink bottle holes. ③ The difference between the gas adsorption capacity of distinct clay minerals is obvious,and the maximum ad- sorption amount of montmorillonite,illite and chlorite is 8. 80,3. 27 and 2. 69 cm3 / g respectively. Clay minerals on methane adsorption is mainly controlled by the specific surface area of minerals,the maximum adsorption capacity and mesoporous specific surface area of clay minerals have a strong positive correlation.