The addition of surfactant in brine during water alternating with CO2 (WAG) injection or co-injection with the CO2 process has proven to produce foam that reduces CO2 mobility. Laboratory experiments have shown that some surfactants generate "smart" foam which selectively reduces CO2 mobility by a greater fraction in lighter rather than in lower permeability cores. The occurrence of such an exciting property in foam displacement and its application for improving oil recovery in heterogeneous porous media are discussed in this paper.
In our latest work that experimentally simulated the heterogeneous characteristic of reservoirs, we used composite cores that contain coaxial zones of high and low permeability either in capillary contact or isolated from each other. Experiments were performed on core systems both with and without oil saturation. Smart foam was injected into these core systems and its performance was determined by the breakthrough time of CO2 and fluid recovery in each well-defined permeability region.
Our results demonstrate that smart foam is useful in correcting nonuniform frontal displacement due to the heterogeneity of a reservoir formation. Smart foam is also very effective in displacing the oil¯¯a benefit frequently overlooked by researchers testing the foam aspects of mobility control.