Mechanistic investigation of CO2-foam stability: implications to CO2 storage and enhanced oil recovery

Abstract

Mitigating excessive CO₂ emissions is a significant challenge for avoiding global climate change, thereby directing researchers towards effective methods for CO₂ utilisation and sequestration. The present study aims to investigate the efficacy of CO₂ foams stabilised with surfactants, polymers, and nanoparticles for enhanced oil recovery (EOR) and CO₂ storage in depleted reservoirs or saline aquifers. The combined use of surfactants, namely alpha-olefin sulfonate (AOS, anionic) and cocamidopropyl betaine (CAPB, zwitterionic), polymers (polyethene glycol, carboxymethyl cellulose, and partially hydrolysed polyacrylamide), and nanoparticles (Al₂O₃ and ZnO) shows pronounced synergistic effects on CO₂ foam properties and performance. The half-life of CO₂ foam stabilised by an AOS + CAPB blend increased from 460 s to 522 s with the addition of Al₂O₃ nanoparticles, which adsorb at the gas–liquid interface, forming a rigid barrier that prevents coalescence and film thinning. Polymer further enhances the stability by slowing down water drainage in the foam lamellae through the formation of interfacial and bulk surfactant-polymer complexes. The results highlight strong synergistic enhancements in AOS–CAPB–Al₂O₃–PHPA composite formulations, resulting in remarkably stable foams with smaller, uniform bubbles, a significantly reduced coarsening rate, and superior interfacial viscoelastic properties. Conversely, the presence of oil above 5% by volume led to rapid foam destabilisation due to its antifoaming properties, resulting in foam rupture and rapid bubble coalescence. The outcome of the studies will be useful in designing and implementing CO₂-EOR and CO₂ sequestration projects in the field.