Performance evaluation and formation mechanism of Janus-SiO2 nanoparticles assisted viscoelastic surfactant fracturing fluids

The eco-friendly viscoelastic surfactant (VES) system, whose viscoelasticity can be enhanced by nanoparticles (NPs), is an appropriate substitute for polymer fracturing fluid. In the present study, the JA12C NPs (Janus SiO2 nanoparticles decorated with dodecyl hydrophobic carbon chain) are successfully synthesized and characterized by Fourier transform infrared spectra (FTIR), thermal gravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscope (TEM). The prepared JA12C NPs are separately induced into three kinds of fracturing fluids (anionic-based VES (aVES), cationic-based VES (cVES), and zwitterionic-based VES (zVES) fluids) to investigate their effects on the rheological properties of various VES fluids. It is found that additional JA12C NPs significantly enhance the viscoelasticity of cVES fluid, while hardly affecting that of aVES and zVES fluids. Then the zeta potential of mixed JA12C/surfactant dispersions and the rheological parameters of diverse VES systems are measured to explore the interaction mechanism of wormlike micelles (WLMs)/JA12C mixture. It is believed that the intensive hydrophobic interaction and the moderate electrostatic repulsion between WLMs and JA12C should be responsible for the visibly enhanced viscoelasticity of JA12C-assisted cVES (cJAVES) fluid. This work suggests the feasibility of using Janus NPs to enhance the tolerance properties of VES fluids in harsh conditions, which fills the gap in the applications of VES fracturing fluids incorporating Janus NPs.