Measurements and Modeling of Polyacrylamide Polymer Viscosities for Chemical EOR Applications

Abstract

Abstract High molecular weight Polyacrylamide polymer brine viscosities were measured and modeled in a wide range of conditions to improve fundamental understanding and field application of chemical enhanced oil recovery (EOR) processes. More than 300 steady shear rate sweep viscosity curves were generated using a copolymer of acrylamide-polyacrylate and two sulfonated tert-polyacrylamide polymers. The generated viscosity curves were fitted to the Carreau-Yasuda (C-Y) viscosity model with fixed Huggins coefficient of 0.2. Intrinsic viscosity was determined using Martin's equation for the given polymer and brine. The obtained intrinsic viscosity was correlated to the brine composition using the 22 data points for each polymer, so this correlation for intrinsic viscosity is a function of material and brine composition. The zero-shear viscosity, shear thinning index, and time constant parameters of the C-Y model were then correlated to intrinsic viscosity, polymer concentration, and temperature for all three polymers simultaneously, which enabled a unified model approach. Polymer solution viscosities were modeled by plugging three individual correlations for zero shear viscosity, time constant, and shear thinning exponent into C-Y model. The modeling results were compared and discussed with those of the Abdullah et al. model (Abdullah et al., 2023) and the Jouenne and Lavache model (Jouenne and Levache, 2020). Of particular importance is the range and composition of the synthetic brines which are representative of the real brine chemistry variable space in chemical EOR research and field applications. The synthetic brine compositions were derived from 119 brines of polymer flooding field projects worldwide, so the work is aimed at practical field applications by excluding unrealistic brine compositions from the design-of-experiment stage. The proposed viscosity model demonstrated significantly improved prediction performances and/or workflow compared to the existing models.