Mobility Control and Solid–Liquid Interface Interaction Mechanisms of Psyllium Gum-enhanced CO2 Foam

Abstract

Efficient mobility control is essential for foam-enhanced CO2 flooding and storage, yet the adsorption of chemicals in reservoirs can cause foam destabilization and mobility-control loss. This study investigates the mobility control and solid–liquid interfacial mechanisms of polymer-enhanced CO2 foam across lithologies using core flooding, adsorption-wettability experiments, and molecular dynamics simulations. Results demonstrate that psyllium gum (PG) reverses the dominant dynamic retention mechanism from surface adsorption to mechanical trapping (with an estimated contribution of 83.5%), thereby establishing strong mobility resistance in carbonate rocks (resistance factor 49.8). Microscopically, PG shields electrostatic attraction between surfactants and rock surfaces via steric hindrance, reducing adsorption and regulating wettability, while forming a viscoelastic lamella at the gas–liquid interface that suppresses CO2 channeling. This study elucidates a synergistic mechanism of low adsorption, high mechanical retention, and strong mobility resistance in PG-enhanced CO2 foam, providing a theoretical basis for designing efficient CO2 foam systems in harsh reservoirs.