Study on the Migration Mechanism of the CO2-Multicomponent Gases Within Inorganic Nanopores in Deep Shale Reservoirs

Abstract

Abstract. Due to the synergistic impact of high pressure within deep shale reservoirs, intricate interactions among gas moleculars, and the coupled influence between gas moleculars and pore walls, the migration of gases in nanopores experiences significant constraints. In this study, by employing the molecular dynamics simulation techniques, the migration process of multicomponent alkane molecular is conducted in deep shale reservoirs. And then, by adopting the tensile molecular dynamics simulation method, a high-pressure-driven model of shale gas migration in deep shale reservoirs is established, elucidating the migration behavior and dynamic mechanisms of CO2-multicomponent gases within the inorganic nanopores in deep shale reservoirs. Meanwhile, based on the spring force suffered by gas when it migrates in inorganic nanopores, the gas migration process in deep shale reservoirs can be divided into three stages (the adjacent stage of the gas moleculars, the migration stage of gas moleculars, and the relaxation stage of gas molecule migration). The resistance mechanism of the gas during migration is further clarified. The results show that the gas–solid interaction and capillary pressure in deep shale reservoirs predominantly impede the migration of multicomponent gases within inorganic nanopores. For the small-scale pore simulation system, the gas–solid interaction effect is significantly improved in particular.