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. (C) 2014 Elsevier Ltd. All rights reserved.