Gas sorption in shale media by molecular simulation: Advances, challenges and perspectives

Shale gas plays a vital role in global energy supply and carbon emission reduction due to its abundant resource reserves and high energy efficiency. In shale nanoporous media, substantial gas is stored in the form of sorption gas including adsorbed gas and absorbed gas. Molecular simulation is a powerful tool to gain insights into the microscopic sorption behaviors and mechanisms of shale gas in nanoporous media. In this work, various molecular models of shale media and gas species as well as their force fields are summarized. Typical simulation methods for shale gas sorption are introduced. The most recent progress about gas sorption behaviors and mechanisms as well as their controlling factors in shale nanoporous media is elaborated. Also, challenges and perspectives in shale gas sorption by molecular simulation are discussed, which can provide a theoretical guide for further in-depth research in this field. Particular attention is devoted to the construction of representative molecular models of shale media, the quantitative determination of absolute adsorption and gas absorption, and the characterization of the coupling behaviors and mechanisms between gas sorption and pore deformation.