Study of nano-SiO2 reinforced CO2 foam for anti-gas channeling with a high temperature and high salinity reservoir.

[Display omitted] • A nano-SiO 2 enhanced HTHS-resistance CO 2 foam for anti-gas channeling was developed. • The injection and anti-gas channeling ability of the CO 2 foam CO 2 was evaluated in HTHS cores. • The mechanism of anti-gas channeling for CO 2 foam was verified by micro visualization experiments. CO 2 flooding has been widely applied in lots of low permeability reservoirs. After extensive CO 2 injection, some reservoirs began to show serious gas channeling problems. CO 2 foam had been successfully used to solve gas channeling problems due to its advantages of water selective plugging features (not plugging oil). In this paper, a novel CO 2 foam system was developed for high temperature and high salinity(HTHS) (85 ℃, 60,000 mg/L) aiming at solving the gas channeling in Changqing Oilfield. Taking the foam half-life as the evaluation standard, the optimum foam system (0.5 wt% EC-1 + 1 wt% SiO 2) for the target reservoir was determined. The influences of temperature, salinity and pressure on the CO 2 foam performance were studied by high temperature and high pressure(HTHP)method. The ability and mechanism of anti-gas channeling were studied by experiments of sand packed tube and microscopic displacement, respectively. The results showed that the foam system possessed good foam properties at HTHS with pressure. As the concentration of SiO 2 nanoparticles increased, the resistance factor of the foam system increased. However, temperature showed an adverse effect on foam stability, the resistance factor decreased with the increase of temperature. The Jamin superposition and emulsion plugging mechanism of foam system was revealed by microscopic displacement experiments. [ABSTRACT FROM AUTHOR]