Investigating gas transport mechanisms and apparent permeability evolution in shale micro-nanopores

Gas flow in shale reservoirs is strongly affected by adsorption-induced deformation, stress sensitivity, and gas slippage in micro–nano scale pores, which makes permeability prediction challenging. In this study, a theoretical apparent permeability model is developed by coupling a capillary bundle representation with adsorption deformation, stress/strain–permeability relationships under constant confining pressure, and the slippage effect. The model is validated using published pulse-decay permeability data for Posidonia shale with CH₄ and He. The predicted results agree well with experimental measurements, with average absolute deviations generally below 0.15. In addition, non-adsorptive gas (He) exhibits higher apparent permeability than adsorptive gas (CH₄). Compared with existing models, the proposed approach explicitly accounts for coupled adsorption deformation and slippage effects within a unified framework, providing improved accuracy and clearer physical interpretation of shale gas transport.