Recent Advances in Modeling Polymer Flooding

Abstract

New and improved physical property models have been added to the UTCHEM reservoir simulator to accommodate a broader range of polymer flooding applications and to improve its predictive capabilities. Accurate simulations of the chemistry and physics of polymer flooding are needed to design and optimize a polymer flood including the selection of the best polymer to use for specific reservoir conditions. The new polymer viscosity model implemented in UTCHEM can be used to calculate polymer viscosity more accurately as a function of polymer concentration, shear rate, salinity and hardness, temperature, and intrinsic viscosity. The new model is based on extensive polymer viscosity and rheological measurements. The improved polymer rheology is important for more reliable predictions of polymer injectivity and reservoir sweep. A hydrolysis model has been added to UTCHEM to aid in the selection of polymers as a function of temperature, brine composition and pH. A new cation exchange model that includes hydrolyzed polyacrylamide has been implemented to account for the effect of different cations in the brine on the polymer properties as a function of the degree of hydrolysis. The inaccessible pore volume model has been modified to include the exclusion of large polymer molecules from pores below a certain size in addition to the effect of polymer size on the velocity of the polymer molecules within the pores that are large enough for the polymer to enter. The new inaccessible pore volume model serves as a useful tool for selecting reservoir- compatible polymers and improving the accuracy of the simulations. Extensive high-quality lab data were used to validate the new models. Simulation cases were built to illustrate how the models can be used to upscale lab results to field scale.