A Model for Multi-component Shale Gas Transport in Nanopores with Multiple Mechenisms Coupling

Under shale gas reservoir condition, the gas composition of shale gas often contains a series of impurity gases. In addition, carbon dioxide and other gases are often injected into gas reservoirs to improve the productivity of shale gas wells. In this paper, a novel model is developed by coupling the effect of other gas components with different transport mechanisms of shale gas through nanopores. Taking the mixture of methane and carbon dioxide as an example, the flow characteristics of the mixture under different carbon dioxide content were studied. The predicted results show that: (a) the Knudsen number decreases with decreasing of methane fraction (increasing of CO₂ fraction). The conductivities of modified diffusion, Knudsen diffusion and coupled flow increase with decreasing of methane fraction. (b) The contribution degrees of Knudsen diffusion and modified slippage flow are comparable to each other under medium pressure level condition (1 MPa). (c) The influence of modified slippage flow on total gas transport capacity in increased with increasing pressure. (d) The effect of different gas mixture system on contributions of modified slippage flow and Knudsen diffusion to total mass flow rate can be neglected over wide ranges of pressures and nanopore radius.