Study of single-phase polymer-alkaline-microemulsion flooding for enhancing oil recovery in sandstone reservoirs

Abstract Enhanced oil recovery methods (EOR) are designed to increase reservoir productivity by facilitating oil displacement in the porous media. Due to its physicochemical properties capable of reducing the interfacial tension and inverting rock wettability, microemulsion flooding has been studied as a chemical EOR method. In this work, we studied the injection of polymer, surfactant, and alkali as single microemulsion media. A microemulsion formulation was selected with high water content and a composition of 1.5% of active matter, 0.05% of oil phase (OP), and 98.39% of aqueous phase (AP) prepared with 1.5% of Na2CO3 and 0.06% of the polymer. The systems obtained were characterized according to droplet diameter, pH, surface tension, and viscosity. We studied the rock-fluid interaction mechanism, evaluating the reservoir rock's wettability before and after contact with the microemulsion in a Botucatu sandstone rock. The microemulsions studied promoted a significant reduction in surface tension and changed the sandstone wettability from oil to water-wet. Coreflooding experiment results proved the potential of microemulsions prepared with alkali and polymer in the EOR process, achieving up to 97% of the oil recovery factor.