Pore-scale simulation of shale gas production considering the adsorption effect

A microscale lattice Boltzmann (LB) model considering the adsorption effect was established and adopted to simulate shale gas production in microscale porous media. The adsorption effect was incorporated into the LB model by introducing the interaction forces between solids and gas particles, and the adsorption parameters were determined by the molecular simulation method through a novel process proposed in this paper. First, the grand canonical Monte Carlo (GCMC) method was adopted to simulate gas adsorption in a slit pore. Then the LB model was also adopted to do the same simulation under the same conditions. By matching the results of LB model with those of molecular simulation, the adsorption parameters in LB model under different conditions were obtained. Then the proposed LB model was adopted to simulate gas production processes in an organic porous medium and an inorganic porous medium with the same geometry. The effects of adsorption on pore-scale gas storage, recovery and production were all analyzed. The simulation results show that adsorption can greatly increase the gas storage in organic porous media, while the gas recovery of organic porous medium is always lower than that of inorganic porous medium since the adsorbed gas is difficult to produce. In addition, the organic porous media will not always produce more gas than the inorganic porous media. Whether the adsorption effect will increase the gas production or not depends on the excess adsorption curve.