Fluid flow and transport in fractal porous media under stress conditions

With the successful development of unconventional oil and gas, obtaining a better understanding of the flow and transport mechanisms in fractal porous media (e.g. tight sandstone, tight carbonate and shale) plays an important role for oil and gas production. As nanopores exist widely in porous media, which can communicate with the larger pores (e.g. micropores) and fractures, the transport mechanism of fluid flow in nanopores is crucial for understanding flow behavior in fractal porous media. Besides, the porous media could be compressed during production and the effective stress provides a possibility to analyze the constitutive equations using the strain and stress relations. Therefore, it is of theoretical and practical signicance to determine the essential controls on the transport mechanism of fluid flow in fractal porous media under stress conditions. In this research, we will derive a theoretical model including various mechanisms (e.g. slip flow, viscous flow, Knudsen diffusion, surface diffusion, etc.) to study the fluid flow and transport in nanopores, which aims at the coupled behaviors in detail. This model considers the porous media by means of fractal geometry, and uses the Hertzian contact theory to represent deformation under stress conditions. The model will generate core-scale parameters (e.g. porosity, permeability, capillary pressure and relative permeability) for practical applications. In addition, the parameter sensitivity will be analyzed and proper values will be estimated using data assimilation/history matching methods from either experimental data or numerical results in existing literatures. Finally, the results of our proposed model will be compared with those from numerical methods (e.g., lattice Boltzmann methods) for validation and verification.