Effect of thermal maturity on shale pore structure: A combined study using extracted organic matter and bulk shale from Sichuan Basin, China

The thermal maturity is of great significance in the evolution of pores in gas shales. In this work, the comparison of pore structures between Wufeng-Longmaxi and Niutitang shales and its corresponding extracted organic matter (OM) is made. The Wufeng-Longmaxi shales have higher total pore volumes, surface areas and porosity than the Niutitang shales and OM pores are the main pore types in both shales. With the thermal maturity (Ro) increases, the OM porosity decreases. Combined with literature results, it is further proved that the evolution of OM pores was related to the gas generation with increasing thermal maturity. Compared with Niutitang shales, the lower thermal maturity of Wufeng-Longmaxi shales is beneficial for preserving OM pores and providing better connectivity. It can be concluded that the thermal maturity is the main controlling factor on the development of OM pores, which are important for the shale gas generation and preservation.