Studies of CO 2 foam stabilized with silica nanoparticles at reservoir conditions were carried out for CO 2 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 CO 2 foam generation at reservoir conditions. The results showed that nanoparticle surface hydrophobicity played an important role in CO 2 foam generation. More CO 2 foam was generated as the particle surface changed from strongly hydrophilic to somewhat hydrophobic. The bubble size of the CO 2 foam decreased noticeably as the particle surface became more hydrophobic. Nanosilica particle-stabilized CO 2 foam demonstrated a significant effect on the reduction of the CO 2 mobility at a phase ratio between 2 and 11. The particle-stabilized CO 2 foam also improved the apparent viscosity of the CO 2 as the mixture flowed through a capillary tube.