Nanoparticle-stabilized CO₂ foam for mobility control and enhanced oil recovery in heterogeneous reservoirs

Surfactant-stabilized foam is a promising method for controlling gas mobility and improving sweep efficiency during carbon dioxide (CO₂)-enhanced oil recovery processes. However, its limited stability poses a challenge. This study investigates the performance of surfactant-only foam versus surfactant–nanoparticle (NP) foam in both bulk and porous media. Static bulk tests, coreflood experiments, and oil recovery tests were conducted. In bulk tests with oil, surfactant-stabilized foam stability declined as oil concentration increased. Adding silica nanoparticles improved foam stability in oil-free systems by reducing bubble coalescence and gravity-driven liquid drainage. Dynamic foam experiments using an Indiana limestone core showed that the apparent viscosity of CO₂ foam nearly doubled with the addition of nanoparticles to the surfactant solution, indicating stronger foam generation. In a heterogeneous coreflood experiment, both surfactant- and surfactant–nanoparticle-stabilized foams effectively diverted flow from high- to low-permeability zones, enhancing sweep efficiency. However, the surfactant-nanoparticle foam generated a higher-pressure drop compared to surfactant-only foam, suggesting it better blocked high-permeability channels and enhanced flow diversion. Oil recovery experiments revealed that the addition of nanoparticles increased oil recovery by approximately 5 % compared to surfactant-only foam. Overall, the results demonstrate that incorporating nanoparticles enhances foam strength, stability, and oil recovery performance. This suggests significant potential for nanoparticle-stabilized CO₂ foam in improving EOR efficiency.