Preparation of novel polymeric surfactants based on synergistic effects and analysis of the mechanism driving the oil-displacement process and enhanced oil recovery

Abstract

Polymeric surfactants have been favored by researchers due to their ability to increase the viscosity of the aqueous phase, reduce the viscosity of the oil phase, and avoid the chromatographic separation effects of polymer-surfactant binary combination flooding. However, there is little research into the oil-displacement effect of polymer surfactants, and the mechanism whereby it enhances heavy oil recovery remains unclear. To fill this theoretical gap in the research into the oil-displacement mechanism of polymer surfactants, a novel polymeric surfactant PNBM was prepared using acrylamide, acrylic acid, nonylphenol ethoxylate (NP), and 4-vinylbiphenyl (VB). The chemical structure of PNBM was validated by characterization methods such as 1HNMR, FT-IR spectroscopy and elemental analysis. The mechanism of PNBM for enhancing heavy oil recovery was systematically studied based on the displacement and profile control by thickening, reducing viscosity by emulsification, and peeling of oil films and droplets. Polymeric surfactant PNM containing NP and polymeric surfactant PBM containing VB were used as control groups. Benefiting from the synergistic effect of two viscosity-reducing monomers, PNBM has better oil displacement effect compared to PNM and PBM: (1) a tighter adsorption film can be formed at the water–oil interface due to the good interfacial activity of PNBM, so that the average viscosity reduction rate of PNBM at a low concentration reaches 85.5 %; (2) PNBM can significantly increase the viscosity of aqueous solutions (increasing to 38.2 mPa·s), decrease the water–oil mobility ratio, and expand the swept volume; (3) PNBM can reduce the contact angle of the water phase on the oil-wet surface to 62.8°, supplemented by its good viscoelasticity, thereby improving the oil-washing efficiency. Therefore, under the triple effects of displacement and profile control by thickening, reducing viscosity by emulsification, and peeling of oil films and droplets, PNBM can enhance heavy oil recovery by 17.7 %, significantly improving the beneficial industrial exploitation of heavy oil reservoirs.