CO2-Soluble Ionic Surfactants and CO2 Foams for High-Temperature and High-Salinity Sandstone Reservoirs

Abstract

The sweep efficiency of CO2 enhanced oil recovery can be improved by forming viscous CO2-in-water (C/W) foams that increase the viscosity of CO2. The goal of this study is to identify CO2-soluble ionic surfactants that stabilize C/W foams at elevated temperatures up to 120 °C in the presence of a high salinity brine using aqueous phase stability, static and dynamic adsorption, CO2 solubility, interfacial tension, foam bubble size, and foam viscosity measurements. An anionic sulfonate surfactant and an amphoteric acetate surfactant were selected to achieve good thermal and chemical stability, and to minimize adsorption to sandstone reservoirs in the harsh high-salinity high-temperature brine. The strong solvation of the surfactant head by the brine phase and surfactant tail by CO2 allows efficient reduction of the C/W interfacial tension, and the formation of viscous C/W foams at high salinity and high temperature. Furthermore, the effect of temperature and methane dilution of CO2 on foam viscosity was eva...