Interaction between Psyllium Gum-Enhanced CO2 Foam and Crude Oil: Oil Resistance and Stabilization Mechanism of the Oil–Water Interface

Abstract

Crude oil-induced foam destabilization is a critical bottleneck to the industrial deployment of CO2 foam flooding technology. However, the complexity of crude oil composition leads to significant variations in the oil resistance behavior of different foam systems. Consequently, elucidating the microscopic oil resistance mechanisms between different oil-phase components and foam is a core issue that must be addressed to develop highly efficient oil-resistance systems. Combining performance experiments with molecular dynamics simulations, this study systematically explores the effects of various crude oil components on the oil resistance of psyllium gum (PG)-enhanced CO2 foams, as well as their oil–water interfacial stabilization mechanism. Results demonstrate that light components (alkanes and aromatics) in the oil phase significantly weaken foam stability by promoting gas mass transfer and foam lamella drainage. Conversely, heavy components (resins and asphaltenes) with high interfacial activity induce surfactant flat-lying adsorption, synergistically constructing a highly viscoelastic “pseudo-emulsion film” with polymer/surfactant molecules (PG/OHSB). This film facilitates the formation of stable emulsified oil droplets that accumulate at the Plateau borders, effectively blocking oil droplet invasion and gas mass transfer. Consequently, the heavy oil (TH) system exhibits maximum stability, with a drainage activation energy of 48.77 kJ·mol–1 and an Ostwald ripening rate of 0.998 × 104 μm3·min–1. Compared to the blank system, the drainage half-life and foam comprehensive index for TH are enhanced by 20.0% and 23.4%, respectively. This study elucidates the molecular mechanisms by which oil components regulate foam stability, providing a theoretical foundation for understanding the differences in oil resistance of CO2 foams across different oil-phase reservoirs, and offering guidance for the design of oil-resistant foam systems and their application in field CCUS-EOR processes.