The objective for this work is to determine transport coefficients of multicomponent systems in atomistic kerogen models using molecular dynamics simulations. In transport of multicomponent gases, we are specifically interested in investigating the effects of nonmethane species (ethane, water, and carbon dioxide) on diffusion of methane. The kerogen unit models prepared by (Ungerer et al., 2014) are used in this study. Two mixtures, one containing water and one without water, are placed within the kerogen structures. Computed methane-methane diffusion coefficients are approximately one order of magnitude higher than those for other species in both mixtures for all kerogen types. This is due to fact that methane has the lowest adsorption compared with other three species, and therefore its Onsager diffusion coefficients are the highest. Among the other three species, ethane has the highest diffusion coefficients and water demonstrates the lowest Onsager coefficients. High adsorption (and low transport coefficients) of water is due to induced polarity of the pore surfaces that causes water molecules to be preferentially adsorbed to the pore surfaces over other species. Most of species demonstrate higher diffusion coefficients in the mixture containing water than in other mixture. In the absence of water molecules, vacant adsorption sites become available for other species. These sites will be preferably filled by carbon dioxide molecules as they have higher adsorption capabilities compared to alkanes.

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