Microscopic displacement features of polymeric surfactant flooding: a microfluidic study

Abstract

Polymeric surfactants possess properties of both of polymer and surfactant in solution thickening and interfacial tension reducing, overcomes the chromatography separation of polymer-surfactant flooding, and shows potential application in chemical enhanced oil recovery as an alternative to the binary blend of polymer and surfactant. In this study, viscosity thickening ability and property in reducing interfacial tension of three homologues of polymeric surfactant that have different fractions of activity unit are studied. The displacement performance of the polymeric surfactants in displacing simulated oil within two-dimensional porous media have been comprehensively determined in pore scale. Displacement efficiency and invasion pattern of polymeric surfactant solutions, forms and fractions of residual oil within different pore structures are quantitatively analyzed, and the obtained data are compared with those of polymer. Results show that viscosities of solutions are thickened using polymeric surfactants and the interfacial tension of crude oil/formation water is reduced to 0.0026 mN/m - 0.23 mN/m. Displacement results show that polymeric surfactants have superiority in displacing simulated oil within dual-permeability porous media compared with polymer, and simulated oil within low permeability region is continuously displaced even after the main flow route forms in the high permeability region. As for the displacements within rock porous media, polymeric surfactants displacements show higher microscopic displacement efficiencies than that of polymer displacement, which means higher displacement efficiency within swept area. This study provides properties of polymeric surfactants in displacing oil and strengthens the potential application of polymeric surfactants in enhancing oil recovery.