Static and flow behaviors of supercritical CO2 foam stabilized with betaine surfactant for mobility control application

Aiming at improving the stability of Supercritical CO2 (SC-CO2) foam in high temperature and salinity reservoirs, a kind of betaine surfactant, Hexadecyl Hydroxypropyl Sulfo Betaine (HHSB), was screened to stabilize SC-CO2 foam. The properties of SC-CO2 foam were improved at elevated temperature and pressure. The effects of surfactant concentration, temperature, pressure and salinity on film drainage rate were measured to explore the stability of SC-CO2 foam. The results showed that an increase of surfactant concentration, pressure and salinity can decrease film drainage rate and enhance the foam stability, which was attributed to the increase of surfactant adsorption at the gas–liquid interface. The performance of SC-CO2 foam formed by HHSB was improved and the tolerant temperature was up to 100 °C. 1-D core flooding experiments indicated that compared with Coinjection of Surfactant and Gas (CSG) method the SC-CO2 foam generated through Surfactant-Alternative-Gas (SAG) method had lower foam strength but better in-depth migration capacity. The high temperature and pressure 3-D sand showed that in Water-Alternative-Gas (WAG) case CO2 broke early through the high permeability layers. In SAG case, SC-CO2 foam can improve the macroscopic sweep efficiency by reducing the CO2 mobility.