The differences of microscopic pore structure characteristics of coal, oil shale and shales and their storage mechanisms

Nitrogen adsorption, mercury intrusion, scanning electron microscope and methane sorption experiments were analyzed for coals, oil shale and shales to study their pore structure characteristics and storage mechanisms. The results are as follows. (1) There are great differences in pore size scale and pore size distribution among coals, oil shale and shales, which are the result of maturity, clay mineral content, and dissolution effect caused by organic fluid; (2) The microscopic pores in low mature kerogen are not developed with few total pores, exhibiting a minor number of micropores and relatively more mesopores as well, while the mature kerogen has much higher specific surface area and pore volume than the low-mature kerogen and is an important contributor to pore space in shales; (3) The methane sorption capacities don't match the specific surface areas for coals, oil shale and shales, indicating that coal sample with lower specific surface has the highest methane sorption capacity, called “overbalance sorption”, which may be caused by the molecular aggregation way of “molecular filling” or even “solid solution”. The methane sorption capacity of oil shale may contain a certain amount of dissolved gas in bitumen and oil; high to over-mature organic-rich shales have significant higher methane sorption capacity compared to low-mature shales. © 2015, Science Press. All right reserved.