Effect of particle hydrophobicity on CO₂ foam generation and foam flow behavior in porous media

Studies of CO₂ foam stabilized with silica nanoparticles at reservoir conditions were carried out for CO₂ foam enhanced oil recovery (EOR) application. In the study described in this paper, three types of silica nanoparticles with varied wettability were employed to study the effects of particle hydrophobicity on CO₂ foam generation at reservoir conditions. The results showed that nanoparticle surface hydrophobicity played an important role in CO₂ foam generation. More CO₂ foam was generated as the particle surface changed from strongly hydrophilic to somewhat hydrophobic. The bubble size of the CO₂ foam decreased noticeably as the particle surface became more hydrophobic. Nanosilica particle-stabilized CO₂ foam demonstrated a significant effect on the reduction of the CO₂ mobility at a phase ratio between 2 and 11. The particle-stabilized CO₂ foam also improved the apparent viscosity of the CO₂ as the mixture flowed through a capillary tube.