Characterizing the Unique Shear Thickening Feature of Novel Surface Active Polymers Targeting Ultimate Recovery

Abstract The primary objective of this work is to understand the behavior of surface-active polymer (SAP) in porous media and its interactions with high-porosity, high-permeability sandstone outcrops. The study also aims to maximize oil recovery by optimizing polymer concentration to achieve a targeted viscosity for effective oil displacement and investigates polymer retention in porous media under various injection strategies. Samples were saturated with high-salinity synthetic formation brine (209,000 ppm), drained with the oil, and aged for one week. Polymer solutions varying in concentration between 500 to 1500 ppm were prepared by mixing polymer powder with the engineered brine. The experimental work consisted of three stages. In stage one, SAP's rheological behavior was analyzed across various key parameters to generate rheology maps to optimize the selection of polymer concentrations and injection rates for effective injection strategies. Stage two involved testing the selected polymer concentrations and injection strategies by performing several core-flooding experiments and assessing polymer behavior via pressure drop and oil displacement in the effluent. Stage three evaluated polymer retention effects through pre- and post-flooding NMR analysis. Selected SAP concentrations (1000, 1250, and 1500 ppm) achieved peak viscosities of 4.65, 10.1, and 19.15 cP, compared to the mineral oil and crude oil of 4.60 and 1.23 cP, respectively, at 80°C. Injection strategies were: (1) shear thickening followed by shear thinning, (2) progressive shear thickening followed by shear thinning, and (3) progressive shear thickening followed by progressive shear thinning. These strategies resulted in oil recoveries of 41.57%, 48.79%, and 52.22%, respectively. The NMR analysis of pore size distributions showed progressive shear thickening, followed by progressive shear thinning, minimized polymer retention. Gradual viscosity reduction after maximum shear thickening displaced the trapped polymers, enabling dual displacement zones: one at the injector and another within the porous media, allowing for greater oil displacement.