Parallel Simulations of Commercial-Scale Polymer Floods

Abstract

Abstract Despite advances in numerical techniques and computer hardware, numerical modeling of commercial scale mechanistic polymer floods remains a challenge. A low order finite difference scheme defined on coarse grids (standard practice in oil industry), tends to smear the front and mask the benefit of polymer solutions whereas the more accurate finer grids require excessive computer run times. A comprehensive polymer module has been added to our in-house reservoir simulator to benefit from parallel capability, efficient algorithms, and accurate grids to make fine grid field-scale polymer flood simulations possible. Polymer flooding is a mature technology to economically recover additional oil from medium to heavy oil reservoirs. Polymers are added to the water to improve the sweep efficiency in heterogeneous formations by reducing the water mobility (ratio of effective permeability to viscosity). Polymer is transported in the water phase by convection, diffusion, and dispersion and delayed by the adsorption of polymer on rock surfaces. Polymer properties include adsorption, permeability reduction, rheology, and inaccessible pore volume. Polymer solutions often exhibit non-Newtonian rheological behavior where the viscosity decreases as the shear rate increases. However, large hydrolyzed polyacrylamide polymers (HPAM) with molecular weights on the order of 20 million or greater exhibit shear thickening behavior where above certain critical shear rate the viscosity increases. This paper describes a reservoir simulator with a comprehensive polymer property model and parallel capability on a cluster of PCs. Simulations of commercial scale polymer floods are performed using fine grid and multiple processors. The impacts of elongational polymer viscosity and near wellbore flux calculations are evaluated.