Streamline-Based Simulation of Non-Newtonian Polymer Flooding

Abstract

Summary Current commercial simulators for polymer flooding often make physical assumptions that are not consistent with available experimental data and pore-scale modeling predictions. This may lead to overly optimistic recovery predictions for shear-thinning polymers, while the potential advantages of reducing flow rate or using shearthickening agents are overlooked. We develop a streamline-based simulator that overcomes these limitations and demonstrate how it can be used to design polymerflooding projects. The simulator implements an iterative approach to solve the pressure field because the pressure depends on the aqueous-phase viscosity, which, in turn for non-Newtonian fluids, depends on shear stress and, hence, the pressure gradients. This is in contrast to the common approach in commercial simulators where this viscosity/pressure interdependence is ignored, leading to overestimation of sweep efficiency. Furthermore, in the simulator, non-Newtonian viscosities are defined to be cell-centered while current simulators use a face-centered approach, thereby overpredicting viscosities and the stability of the displacing fronts. In addition, we use a physically based rheological model where non-Newtonian viscosities in two-phase flow are taken at actual effective stresses instead of single-phase equivalents. To validate the simulator, we construct 1D analytical solutions for waterflooding with a non-Newtonian fluid. We then compare our results to those from commercial simulators. We discuss the significance of current assumptions to demonstrate the effect of non-Newtonian behavior on sweep efficiency and recovery.