A Review of Foamed CO ₂ Dynamics during Geo-Sequestration in Deep Saline Aquifers

Geological sequestration of carbon dioxide (CO2) in deep saline aquifers requires an improved control of plume migration and enhanced trapping security. Foamed CO2, generated by dispersing CO2 in an aqueous surfactant solution, offers a viable means to increase the storage effectiveness within geological formations. The foamed technique primarily increases the CO2 viscosity and sweep efficiency, thereby providing uniform displacement and enhancing residual trapping. This review critically examines foamed CO2 dynamics in porous media with direct relevance to geo-sequestration applications. First, we outline the underlying pore-scale physics governing foam generation, propagation, and stability, emphasizing their sensitivity to reservoir storage conditions. Literature reports show that high-salinity brines (>100,000 ppm TDS) can reduce foam half-life by 40–80%, while surfactant adsorption onto reservoir minerals (0.2 to 2.5 mg/g rock) leads to notable chemical loss and increased operational costs. Whereas conventional CO2 injections typically yield trapping efficiencies of 10–25% pore volume, experimental studies in saline-aquifer analogs demonstrate that foamed CO2 can raise trapped CO2 saturations within the swept region to 20–60%, depending on surfactant chemistry, rock type, injection strategy, and reservoir heterogeneity. Key deployment challenges of foamed CO2 technologies include foam instability and surfactant degradation under high-salinity aquifer conditions, economic constraints associated with adsorption losses, and uncertainties in the long-term storage performance. A central modeling gap in current simulation models is the lack of validated upscaling strategies to translate pore-scale lamella dynamics into reservoir-scale forecasts. Overall, this review highlights these barriers while providing new insights into CO2 foam behavior and its potential to enhance geo-sequestration performance strategies in deep saline aquifers.