Shale and tight gas reservoirs consist of porous structures with pore diameter in the range of some mm to μm. At these scales, the pore diameter becomes comparable to the gas mean free path. Flows in these structures fail often in the transition and slip regimes. Standard continuum fluid methods such as the Navier-Stokes-Fourrier set of equations fail to describe flows of these regimes. We present a Direct Simulation Monte Carlo study of a 3D porous structure in an unlimited parallel simulation. The three-dimensional geometry was obtained using a microcomputed–tomography (micro-CT) scanner with a resolution in the scale of some μm. The gas considered is CH4 (100%) and the gas inter-molecular collision model for the simulation is the variable hard sphere (VHS). We present results for different Knudsen numbers. The DSMC is applied in porous structures for the flow regimes where it was found in the cavity case to be appropriate. Our results demonstrate that significant differences appear in gas properties depending on the Knudsen number and the flow regime.

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