Synergy of hydrophilic nanoparticle and nonionic surfactant on stabilization of carbon dioxide-in-brine foams at elevated temperatures and extreme salinities

Stability of carbon dioxide foam attracts huge attentions while being of great challenge to many industrial practices. In this paper, aqueous CO 2 foam stabilized with synergy of hydrophilic nanoparticles and nonionic surfactants was experimentally investigated at elevated temperatures and extreme salinities. The foam formula consisting of 1.5 wt% T40 and 2.49 mM C 12 E 23 was determined under elevated temperature and salinity conditions. At 80 °C, the foam volume of the C 12 E 23 /T40 foam is 225 mL, and the half-life is 32 min, which is 13.9 times that of the C 12 E 23 foam. At a salinity of 17 × 10 4 mg/L, the foam volume is 185 mL, and the half-life is 71 min, which is 24.4 times that of the C 12 E 23 foam. With increasing salinity and temperature, the interfacial tension rises, and the viscoelastic modulus gradually declines, resulting in a lower foam stability. However, the T40/C 12 E 23 foam has a good temperature and salinity tolerance, which can be used under harsh reservoir conditions. In a heterogeneous microscopic visualization model, water channeling in high-permeability regions inhibits the further increase in oil recovery. Subsequent injection of the C 12 E 23 /T40 foam improves the oil recovery factor up to 86.2%. The C 12 E 23 /T40 foam enhances the oil recovery by increasing the sweep area and flooding efficiency. In a sandpack model, the plugging pressure gradient of the CO 2 foam stabilized by 2.49 mM C 12 E 23 and 1.5 wt% T40 reaches 25.3 MPa/m, which is 12.65 times higher than that of the C 12 E 23 foam. The composite reinforced foam attains good water blocking and profile control effects, thereby increasing the oil recovery factor 20.1% after water flooding. This study of great importance to improve not only the oil recovery efficiency, also anywhere where CO 2 -in brine foam applicable.