A Lattice Boltzmann Model for Simulating Gas Flow in Kerogen Pores

Abstract

Nanoscale phenomena in kerogen pores could result in complicated non-Darcy effects in shale gas production, and so classical simulation approaches based on Darcy’s law may not be appropriate for simulating shale gas flow in shale. In general, understanding the shale gas transport mechanisms in a kerogen pore is the first and most important step for accurately simulating shale gas flow in shale. In this work, we present a novel lattice Boltzmann (LB) model, which can take account of the effects of surface diffusion, gas slippage, and adsorbed layer, to study shale gas flow in a kerogen pore under real gas conditions. With the Langmuir isothermal adsorption equation and the bounce-back/specular-reflection boundary condition, the gas–solid and gas–gas molecular interactions at the solid surface are incorporated into the LB model. Furthermore, the effects of surface diffusion and gas slippage on the free-gas velocity profile and mass flux in a kerogen pore are studied via the LB model. It is found that the free-gas velocity profile appears as a parabolic profile in a kerogen pore and the free-gas velocity at the center of the kerogen pore is apparently higher than that near the wall. In particular, we find that both surface diffusion and gas slippage can enhance the mass flux. Compared with gas slippage, surface diffusion is a more important factor on the shale gas transport in small pores, while it can be negligible in large pores.