Breaking the Limits of CO2 EOR: Why Nanobubbles are Effective in Oil Mobilization

Abstract While interest in renewable energy resources is growing, the demand for oil and gas remains strong, creating a need for more efficient recovery methods. Water flooding often leaves a large amount of oil behind, and existing enhanced oil recovery (EOR) methods, such as using surfactants, polymers, alkaline, or nanoparticles, struggle with high cost, surface adsorption, and stability issues. This study investigates CO2 nanobubbles as an alternative to conventional chemical enhanced oil recovery methods, focusing on their stability, high surface area, and ability to modify interfacial energies at liquid-fluid and liquid-fluid-solid interfaces. CO2 nanobubbles are generated by injecting CO2-saturated water through a porous plate diffuser into water containing varying concentrations of surfactants. Their size and concentration are characterized using a particle size analyzer. Interfacial tension and contact angle measurements are performed to assess their impact on surface energy. Finally, core flooding experiments are conducted to evaluate their effectiveness in mobilizing residual oil. The results indicate that CO2 nanobubbles have advantages over microbubbles in key interfacial and flow-related properties. Core flooding experiments, along with interfacial tension and contact angle measurements, suggest improved oil mobilization and fluid distribution. These findings point to the potential of CO2 nanobubbles as a practical and scalable approach for enhanced oil recovery and CO2 utilization, particularly in low-permeability formations. The study offers comparative experimental data that contribute to the growing understanding of nanobubble behavior in EOR applications.