Abstract
Reduction of the CO2mobility is beneficial during subsurface sequestration of anthropogenic CO2in salineaquifers and hydrocarbon reservoirs by mitigatingflow instabilities leading to early gas breakthrough and poorsweep efficiency. Injection of CO2foam is afield-proven technology for gas mobility control. Foam generationand coalescence are compared between six commercially available surfactants with a range in CO2solubility,during unsteady state injection of dense CO2-foam in a long sandstone outcrop core (1.15 m). Foam generationcategories and foam decay were defined based on the observed changes in foam apparent viscosity duringgeneration and coalescence. The degree of CO2solubility influenced apparent viscosity development and peakfoam strength for the tested surfactants. Variations in foam peak strength resulted in a range of water saturationsat CO2breakthrough (up to 24 percentage points difference observed experimentally), with implications for theCO2storage capacity.