Molecular simulation on the desorption and extraction of methane in the slits with varying surface activity

Understanding the production process of shale gas in the complex geological environment is important for the recovery prediction of shale gas development. The adsorption/desorption and extraction of methane in the slits with varying surface activity simplified by tuning the force field parameters are studied with molecular dynamics (MD) simulations. The density of free gas in the slits does not change with the surface activity, while the density of adsorbed gas increases with the surface activity. A minimum pressure difference to initiate the desorption is characterized by the non-equilibrium molecular dynamic (NEMD) simulation. The high surface activity results in not only the slow flow of free gas, but also the slow desorption of the adsorbed gas. Thus, the extraction presents a slow rate and long-tail with extraction times. The adsorption/desorption and the extraction computations in the MD simulations provide a useful reference for the production prediction of shale gas.