Impact of surfactants on CO2-brine relative permeability under reservoir conditions

Abstract

Interfacial tension (IFT) reduction and wettability alteration of porous media are effective in enhancing oil recovery. However, the impact of these factors on CO2-brine two-phase flow for CO2 geological storage is yet to be directly demonstrated. In this study, experiments were conducted on two Berea sandstone cores with an average length of 120 mm and diameter of 38 mm to assess the effect of surfactant pre-injection on the flow of CO2-brine under reservoir conditions at 10 MPa and 40 °C. It was validated that the experimental system could provide reliable results by comparing the baseline relative permeabilities with those presented in the existing literature. It was consistently demonstrated through repeated experiments that a surfactant solution, even when present in low concentration, could enhance CO2 saturation and relative permeability using identical procedures. Specifically, the CO2 relative permeability was increased by at least 56% from the baseline. Additionally, the experiment on the imbibition process showed that surfactant treatment effectively increases residual CO2 saturation. The results support previous numerical analysis and show that surfactant pre-injection could improve injectivity and contribute to a smaller CO2 footprint such that CO2 is prevented from any leakage pathway.