A Review of Foamed CO₂Dynamics 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.