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

Abstract

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.

Highly Stable Polymer-Enhanced Pickering Foams for Hydraulic Fracturing Applications

“…Regarding aqueous foams with nanoparticles, or so-called Pickering foam, the improvement in foam stability can be attributed to the extremely large detachment energy of particles from the gas/liquid interface. , The wettability of particles, characterized by the contact angle, is a good indicator of the surface activity that determines the stabilizing effectiveness, and existing studies indicated that nanoparticles with a contact angle between 40 and 70° would be optimal for producing stable Pickering foam; − Li et al recently reported that the ideal nanosilica contact angle for stabilizing foam is between 60 and 90°. Typically, nanoparticles are dispersed with appropriate surfactants in the foaming liquid, and the surfactant concentration always plays a significant role in modifying the surface activity of nanoparticles, whereas an excess surfactant would reduce foam stability . A major issue with nanoparticle-stabilized foam is its relatively low viscosity, which prevents it from carrying proppant for an extended period.…”

“…Typically, nanoparticles are dispersed with appropriate surfactants in the foaming liquid, and the surfactant concentration always plays a significant role in modifying the surface activity of nanoparticles, whereas an excess surfactant would reduce foam stability. 29 A major issue with nanoparticlestabilized foam is its relatively low viscosity, which prevents it from carrying proppant for an extended period. This is easily remedied by the addition of water-soluble polymers, and the presence of nanoparticle−polymer−surfactant micellar networks in the continuous phase may also reduce polymer amounts, thereby decreasing the risk of polymer-related reservoir damage.…”