Compositional controls on nanopore structure in different shale lithofacies: A comparison with pure clays and isolated kerogens

•Shale lithofacies are identified as 12 types based on clay content and TOC criteria.•Compared to mixed lithofacies, argillaceous OM-rich shales have larger specific surface area (SSA) and pore volume (PV) in the full range of pore sizes.•Clay components in shales mainly contribute to the pore volume of mesopores ranging from 2 to 17 nm.•OM components in shales mainly contribute to the SSA of micropores 2% and illite-dominated clay contents > 50%) develop more interconnected pores with better hydrocarbon storage potential. The argillaceous lithofacies have large amounts of cleavage-sheet pores with large pore volumes; the accumulative pore volume of the pores in diameter from 2 to 17 nm constitutes the major amount of total pore volume that is associated with free gas. The OM-rich lithofacies develop more OM-pores (particularly in pore diameter