Modeling focused fluid flow with geological heterogeneity

Two-phase flow equations that couple solid deformation and fluid migration have opened new research trends in geodynamical simulations and modeling of subsurface engineering operations. A numerical model based on two-phase flow equations has been used to study the formation of focused fluid flow in ductile/plastic rocks. While the effects of material properties such as permeability, bulk viscosity, shear viscosity, and bulk moduli have been studied with simple models that contain mainly homogenous material, realistic models with geological heterogeneity are scarce. This is partly due to the physical nonlinearity of fluid-rock systems and the strong coupling between flow and deformation. Here we present numerical models with a viscoelastic approach that solves hydromechanics coupling using an efficient pseudo-transient solver, which can model focused fluid flow with sharp material boundaries. First, we study the effects of a less permeable block on the propagation of channelized fluid flow by varying the permeability factor by several orders of magnitude and block size. We found that an obstacle does not stop the propagation of the localized channels but deflects and slows them down. A wide block allows channels to pass through slowly, while a narrow block deflects the channels to the sides.  Second, we study the dynamics of fluid channels reaching a sharp geological boundary that is significantly less permeable. We also adjust the bulk viscosity and permeability exponent for different materials in our models to mimic the real geological materials. This makes it possible to consider more realistic scenarios with intraformational and top-sealing layers relevant to CO2 storage and natural fluid migration.