Comparison of Factors Influencing Pore Size Distributions in Marine, Terrestrial, and Transitional Shales of Similar Maturity in China

Abstract

This paper compares pore size distributions in different sedimentary facies shales for similar maturity in typical areas, China. Pore size distributions were analyzed using low-pressure gas adsorption, mercury intrusion capillary pressure, and field-emission scanning electron microscopy techniques. Results showed that pore volume and surface area of shales clearly covary with sedimentary facies, total organic carbon (TOC) contents, clay minerals, maturity, and kerogen type. Influenced by the compaction and clay minerals, the immature terrestrial Jurassic Yanan shales exhibited the highest pore volume and surface area, which are much higher than those of overmature transitional Permian Shanxi and marine Longmaxi shales. The pore volume of shales mainly consists of meso- and macropores, whereas micro- and mesopores comprise most of the surface area. For similar immature shales, pore size distributions are mainly influenced by the degree of compaction. For similar overmature shales, pore size distributions a...