Matching early-time water flowback is important for history matching and understanding near-fracture fluid dynamics. ResFrac’s water banking capability addresses this within the framework of its 1D submesh method.
ResFrac typically uses a coarse matrix mesh, with the 1D submesh providing fine-resolution leakoff and production calculations near fractures. Because the 1D submesh does not solve a full multiphase flow problem, approximate methods handle multiphase effects. Water banking is one of these methods.
As water leaks off from fracture elements during pumping, the simulator assigns it to a ’water bank’ representing a region of elevated water saturation immediately surrounding the fracture. During flowback, the water bank depletes first. To reflect the resulting elevated water cut, the model increases water relative permeability (and optionally decreases hydrocarbon relative permeability) during the flowback period.
This document explains how to configure the water bank parameters and calibrate them to match field-observed flowback data.