Many subsurface and industrial porous media such as carbonate rocks, filters, and catalysts possess multiscale porous structures that play an important role in regulating fluid flow and transport therein. A pore-network-continuum hybrid flow model is promising for numerical studies of a multiscale digital rock. It is, however, still prohibitive to the REV-size modeling because tens of millions of microporosity voxels may exist.
In this talk, I will introduce a novel and robust algorithm for coarsening microporosity voxels of a multiscale digital rock. Then, we combine coarsened microporosity grids with the pore network of resolved macropores to form efficient computational meshes. Furthermore, a pore-network-continuum simulator is developed to simulate flow and transport in both synthesized multiscale digital rocks and realistic carbonate and tight rocks. I will show that the coarsening algorithm can reduce computational grids by about 90%, which substantially reduces computational costs. Meanwhile, coarsening microporosity has a minor impact on the predictions of absolute permeability, gas production curves, and breakthrough curves of solute transport. Finally, I will present the application of the hybrid model in the modeling of capillary pressure and relative permeability curves of tight sandstones. The developed pore-network-continuum hybrid model aided by grid coarsening of microporosity serves as a useful numerical tool to study flow and transport in multiscale porous media.

multiscale digital rocks,pore-scale modeling,two-phase flow,permeability