Laboratory Test Study of CO₂ Responsive Enhanced Foam System

The development effect of CO₂ flooding in low permeability reservoirs is affected by the gas channeling. In response to this problem, the foam comprehensive value was used as the evaluation index to establish CO₂ responsive enhanced foam system by optimizing foaming agent with stirring method. The formula was 0.1% foaming agent AOS(alpha olefin sulfonate) adding 4.0% small molecule amine and water. Its viscosity, which was close to water viscosity before exposure to CO₂, increased by more than 18 times after reaction with CO₂. The results of performance evaluation indicated the foam comprehensive value of the proposed CO₂ responsive enhanced foam system could reach more than 11 times those of conventional foam systems, with obvious shear-thinning characteristics. The rheological equation conformed to the rheological model of power-law fluids. With stronger viscoelasticity than those of conventional foam systems, the proposed foam system could also be used to plug the dominant seepage channels to inhibit the gas channeling during CO₂ flooding in heterogeneous low permeability reservoirs and ultimately to enhance the oil recovery in such reservoirs. The research results showed that the CO₂ responsive enhanced foam system could solve the problem of gas channeling and improve the development effect of CO₂ flooding in low permeability reservoirs.