Impact of Hydrophobicity of SiO2 Nanoparticles on Enhancing Properties of Colloidal Gas Aphron Fluids: An Experimental Study

In recent years, colloidal gas aphron (CGA) fluids have been much attended by researchers for their possible application in infill drilling, due to their pore blockage ability. In this study, the possible synergistic effect of silica nanoparticle hydrophobicity in the presence of sodium dodecyl sulfate (SDS), as a surface active agent, on enhancement of properties of CGA fluids was experimentally investigated. Results revealed that the hydrophobicity of nanoparticles, adsorbed at the bubble interface, plays an important role in improving stability and blockage ability at low as well as high pressure/temperature conditions, low shear rate viscosity (LSRV), and return permeability ability of CGA dispersion measured in a special radial sand pack apparatus at different levels of surfactant concentration. It was observed that partially hydrophobic SiO2 nanoparticles (nanosilica coated with KH550-Silane) yield a better performance than both strongly hydrophilic and hydrophobic nanoparticles (silicon dioxide nanopowder coated with 2 wt. % Silane) which confirms what is expected from the particle detachment theory. Optimal SDS concentrations equal to 0.25 wt. % for strongly hydrophilic, and 0.33 wt. % for both strongly hydrophobic and partially hydrophobic SiO2 nanoparticles were also found, which maximize the improving effect of CGA fluids. The superiority of the aphronized fluid improved by partially hydrophobic nanoparticles of SiO2 to CGA fluid stabilized only by surfactant makes the CGA fluids attractive for some industrial and drilling applications.