Laboratory study of CO2 foam for enhanced oil recovery: Advanced screening, optimization, and evaluation

CO2 foam has been proposed as mobility control agent to overcome various limitation of CO2 injection such as viscous fingering, gravitational override and reservoir heterogeneities which lead to poor sweep efficiency. In this study, CO2 foam formulation was screened and optimized under HPHT conditions to achieve strong foam which results in high oil recovery. For this purpose, different surfactant formulations were prepared in brine with fixed salinity. The stability of bulk foam was measured using FoamScan (Teclis) in the presence of Malaysian crude oil. Whereas, a HPHT foam rheometer was used to perform advanced level screening and optimization at different foam qualities and shear rates. The best foam formulation obtained was then evaluated in core flooding experiment using Berea sandstone (250mD) by co-injection mode under HPHT condition. Among various formulated surfactant mixtures, the combination of alpha olefin sulfonate (AOS) and betaine with specific composition was able to generate strong supercritical CO2 foam at different shear rates under reservoir conditions. Foam rheology results showed that 80% foam quality as the optimum condition for having a high apparent viscosity. Results from co-injection experiments in porous media show that the designed CO2 foam has successfully improved the cumulative oil recovery from 57.58% to 74.08%.