Abstract
Upscaling of parameters involved in single and two-phase flow has been researched quite extensively, and several methods for performing upscaling are known and understood. Less work has been done related to upscaling of enhanced oil recovery simulations. This is what we investigate, and in particular, we consider upscaling of parameters related to polymer flooding, which is the process in which large polymer molecules are added to the injected water to enhance its ability to push hydrocarbons through the reservoir. Herein, the polymer flooding process is described as a two-phase, immiscible system that in addition to a Todd-Longstaff mixing model includes permeability reduction, polymer adsorption, and dead pore space. Effective parameters are computed by running simulations until a steady-state is reached and then performing upscaling based on the fluxes. This method is used by a major oil company as part of an established work flow for single and two-phase upscaling, and it is therefore natural to try to extend the method to polymer flooding. The upscaling is performed on the meter scale, where the steady-state assumption best can be justified. The procedure involves first performing single-phase upscaling of the absolute permeability, then two-phase upscaling of relative permeabilities, and finally, upscaling of the parameters involved in polymer flooding. The new upscaling method is verified against an analytical solution and validated on two synthetic models that include real data. Results show that the permeability reduction factor, which only depends on polymer concentration in the fine-scale model, will generally also depend on water saturation in the upscaled model. This introduces addition computational costs in the simulation, since the property evaluations now require extensive use of lookup-tables and interpolation. We therefore suggest making simplifications in order to reduce the complexity.
