Pore-scale simulation of viscous instability for non-Newtonian two-phase flow in porous media

The impact of micro-heterogeneity on non-Newtonian two-phase flow is the focus of the present study. The direct numerical simulation of non-Newtonian fluids (modelled using shear stress-dependent Meter model) displacing oil in 3D Mt. Simon sandstone and 2D heterogeneous porous media were considered over a range of wettabilities (strong imbibition to strong drainage), capillary numbers and viscosity ratios. This study suggests that heterogeneity of the porous medium can potentially lead to an unstable fluid flow front (even after use of polymer). Therefore along with capillary number and viscosity ratio, heterogeneity is the governing factor for controlling viscous and capillary fingering, and it is crucial to account for the microscale heterogeneity of porous media to design polymer solution injection.