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Methane Flow in Shale Nanopores with Kerogen Microstructure by Molecular Simulations


 We perform a systematic molecular investigation of construction of the kerogen matrix and simulation of gas flow. The kerogen matrix is constructed by 60 Type-II kerogen macromolecules. The pore space is generated by means of dummy atoms. The porosity, surface area, and transport diffusivity are analyzed. In the past, the simulations of methane flow have been performed assuming rigid molecules in the kerogen matrix. We extend the simulations from rigid molecules to flexible molecules in the kerogen matrix. The gas flow simulation is performed based on the boundary-driven method. The results show that the relaxation of the generated kerogen matrix after the deletion of dummy atoms should be part of the process. Without the relaxation, the pore volume will be overestimated significantly. The transport diffusivity in flexible kerogen matrix is generally higher than in rigid kerogen matrix. The flux is mainly contributed by the adsorbed methane molecules. There is additional flux through the occasionally opened pores in the flexible kerogen matrix.