Experimental Study of the Stabilization of CO2 Foam by Sodium Dodecyl Sulfate and Hydrophobic Nanoparticles

CO 2 foam can control the CO 2 mobility and improve the sweep efficiency in reservoirs; however, CO 2 foam stabilized solely by surfactants is not stable. Nanoparticles can improve the performance of CO 2 foam. The synergistic effect of SiO 2 nanoparticles and sodium dodecyl sulfate (SDS) on the CO 2 foam stability was studied in this paper. The experimental results show that the synergistic effect requires an SDS/SiO 2 concentration ratio of 0.1–0.4. The strength of the effect increases as the SDS/SiO 2 concentration ratio increases from 0.1 to 0.17 but then decreases as the ratio further increases from 0.17 to 0.4; thus, a ratio of 0.17 provides the best performance for CO 2 foam. The mechanisms of the synergistic effect of SDS and SiO 2 include modulating the position of nanoparticle adsorption on the CO 2 and liquid interface, improving the interfacial properties of the CO 2 foam, and reducing its liquid discharge and coarsening. SiO 2 nanoparticles can also improve the CO 2 foam performance under high temperatures and pressures. The visual flooding experiment reveals that the addition of SiO 2 nanoparticles can improve the stability of CO 2 foam in porous media and shows good tolerance of crude oil. SDS/SiO 2 foam can increase the pressure differences of the flow in sandpacks after water flooding and improve the oil recoveries markedly. As the SDS/SiO 2 concentration ratio increases, the pressure differences and enhanced oil recovery first increase and then decrease. The best CO 2 foam flooding performance is achieved at an SDS/SiO 2 concentration ratio of 0.17, which is related to the CO 2 foam stability. The experimental results provide theoretical support for improving CO 2 foam flooding under reservoir conditions.