The shale gas flow in the complex porous media based on the lattice Boltzmann method

Due to the tightness of shale, its fluid microflow mechanism has always been a hot topic of research. The lattice Boltzmann method has become an effective way to study this mechanism in the gradual improvement over the past few decades. However, current research has not yet provided a unified analysis of various microscale effects and heterogeneity of porous media. By introducing regularization equations, correcting local Knudsen numbers, modifying boundary conditions, and combining with the generalization processing of microscale effects, this article proposes a fully coupled shale gas lattice Boltzmann model that includes all the above-mentioned factors. The simulation results show that the microscale effects will have a significant impact on gas flow when the pore diameter is below 10 nm. When the pore size is greater than 50 nm and the pressure is greater than 20 MPa, the influence of Knudsen diffusion can be ignored. Compared to Knudsen diffusion, surface diffusion requires lower pressure and smaller pores to manifest. The surface diffusion rate will reach its optimal state at a pore size of 5 nm and a pressure of 10-20 MPa. The impact of surface diffusion can be ignored when the pore size is larger than 20 nm.