Synergistic Stabilization Mechanism of SiO2 Nanoparticles and Anionic Surfactants during Foam Fracturing

To study the synergistic stabilization mechanism of SiO2 nanoparticles and anionic surfactants during foam fracturing, inorganic SiO2 nanoparticles and sodium dodecyl sulfate (SDS) were used as a foam stabilizer and foaming agent, respectively, to prepare foam fluids. Foam stability was analyzed by evaluating the foam volume, half-life, and morphology. The synergistic stabilization mechanism of SDS and SiO2 nanoparticles was studied by measuring and analyzing the surface tension, contact angle, and bubble diameter. The results indicated that, at a suitable SDS concentration, the surface activity of the nanoparticles can be altered to enhance the adsorption of SiO2 nanoparticles at the gas–liquid interface and, consequently, improve foam stability. However, excess SDS caused a decrease in foam stability. Upon increasing the SDS concentration, the contact angle between the SiO2 nanoparticles and water decreased gradually, and the SiO2 nanoparticles became increasingly hydrophilic. The average bubble diameter of the SiO2–SDS foam systems decreases with the increase in time, and the foam system with the smaller change trend of the bubble diameter is more stable. Moreover, with the increase in time, the nanoparticles adsorbed by the ruptured bubbles are transferred to the surrounding of the bubbles that are not ruptured, increasing their liquid film thickness and improving the stability of the foam system. These results provide an experimental basis for the application of the nanoparticle in foam stabilization during coal seam fracturing.