DEM modeling of coupled multiphase flow and granular mechanics: wettability control on fracture patterns

As one of the factors that influences multiphase flow in porous media, wettability has been studied for decades, yet many fundamental questions remain. In a recent experimental study, the impact of wettability on the fluid-fluid displacement pattern in a deformable granular pack was investigated. The experiments show the emergence of fracture of the granular pack under certain conditions of injection rate and confining stress. They also show that changes in wettability lead to striking differences in the fracture network morphology.
Here we use discrete element modeling (DEM) to provide insight into the mechanisms underpinning these experimental results. We first develop a 2D model with single-phase flow, and validate it against results from fluid-driven deformation of a confined monoloayer of hydrogel particles [MacMinn et al., PRX 2015]. To study two-phase flow, we couple a dynamic pore-scale network description of fluid-fluid displacement with a DEM model of the mechanical deformation of the skeleton of solid grains. This modeling approach allows us to capture the effects of varying wettability on the fracture pattern, thereby offering a grain-scale mechanistic understanding of the fracturing process.