Insights into the preparation and mechanism of Non-Alkali viscosity reducer for enhancing heavy oil recovery under Low-Shear condition

Abstract

Viscosity reducer flooding technology has been applied for enhanced oil recovery (EOR) in ordinary heavy oil reservoirs. However, the non-alkali viscosity reducer for heavy oil reservoir under low-shear condition has not been systematic studied. Thus, in terms of emulsifying ability and stability, oil–water interfacial tension and viscosity reduction performance, the non-alkali viscosity reducer was prepared under low-shear condition by the bottle inversion test method and shaker shaking method. Then the enhanced oil recovery ability of the non-alkali viscosity reducer was evaluated and the pore-scale EOR mechanism was investigated via microscopic visual flooding experiments. Results show that the non-alkali viscosity reducer consisting of C12-14 alkyl glucoside (APG1214) surfactant and sodium linear-dodecyl benzenesulfonate (LAS-30) surfactant was prepared with the oil–water interfacial tension of 0.15mN·m−1 and viscosity reduction rate of 97.9%. Compared with water flooding, the non-alkali viscosity reducer can significantly increase the sweep efficiency and the oil displacement efficiency and enhance oil recovery by 8.94% by the mechanism of emulsification, reducing interfacial tension and changing wettability.