King Fahd University of Petroleum and Minerals, Saudi Arabia
CO2-surfactant foam injection is a widely known enhanced oil recovery (EOR) technique that provides better hydrocarbon recovery compared to simple CO2 flooding. Selection of a suitable surfactant for foaming requires an in-depth experimental study. The surfactant should be thermally stable, compatible with reservoir brine and other chemicals, have lower adsorption on reservoir rock, have high foamability and foam stability, and should be economically viable. In this work, foamability and foam stability of three different surfactants were evaluated using a dynamic foam analyzer. These surfactants were fluorinated nonionic, fluorinated zwitterionic, and hydrocarbon zwitterionic surfactants. Effects of surfactant type and structure, concentration, temperature, polymer additions, salt addition, and type of injected gas were investigated on foamability and foam stability. The foamability was assessed using the volume of foam produced by injecting a constant volume of gas. Foam stability was determined by its half-life time. It was found that foamability was highest by a hydrocarbon zwitterionic surfactant. However, the foam generated using fluorinated zwitterionic surfactant was more stable. A mixture of solution containing zwitterionic fluorinated and hydrocarbon fluorinated surfactant showed better foam generation and foam stability. The foam that was generated using CO2 had less stability compared to air-generated foam. The addition of a polymer significantly improved foam stability without affecting foamability. The presence of salt increases both foam stability and foam generation. This study helps in optimizing the conditions of foam injections for enhanced oil recovery.