Salinity, pH, and Surfactant Concentration Effects on CO₂-Foam

The influence of a number of parameters on CO2-foam stability and surfactant adsorption at reservoir conditions were determined. At 25°C and 1500 psig, using different brine concentrations (NaCl/CaCl2 at 3:1 wt ratio), foam stability was determined to be insensitive to salinity when Chaser CD1045™ (CD) concentrations were \u3e 0.025 wt %. This implied that CD could be used as a stable foam over a wide range of field conditions, but become sensitive to salinity when CD concentration is for example ≥ 0.005 wt %. CO2 foam stability was surfactant concentration-dependent. Coalescence of bubbles is observed only at CD concentration of 0.005 wt %, well below the cmc. Adsorption onto kaolinite increased with surfactant concentration. Adsorption increased with salinity for both NaCl and CaCl2 with the divalent salt system inducing a higher adsorption on the kaolinite. Foam stability was insensitive to salinity when CD concentrations were 0.025 wt % and high, but was sensitive to salinity when CD concentration was 0.005 wt%. Adsorption decreased with pH due to the electrostatic repulsion between bubbles and the grains of rock