Viscoelastic surfactant (VES) fracturing fluids gain significant attention in the hydraulic fracturing field with low reservoir damage. However, the harsh reservoir conditions seriously cause the structural instability and viscoelastic degradation of VES fracturing fluids. In this study, the silicon quantum dot (SiQD)-enhanced stearyl trimethylammonium bromide (STAB)/sodium salicylate VES fracturing fluids were constructed and evaluated. Then, the properties (proppant transport, gel-breaking, and permeability damage) of VES fracturing fluids containing different nanoparticles were systematically investigated. SiQDs were characterized by the Fourier transform infrared (FTIR), dynamic light scattering (DLS), transmission electron microscopy (TEM), and nitrogen adsorption–desorption experiments. Then, the rheological test and Cryo-TEM were employed to study the influences of various nanoparticles on the viscoelasticity of VES fracturing fluids. Compared to VES fracturing fluids enhanced by hydrophilic SiO2 nanoparticles (SiNPs, 0.1 wt %), the relatively low-concentration SiQD (0.025 wt %)-reinforced VES fracturing fluids exhibited superior tolerance properties and application performance in harsh reservoir environments. The very intensive electrostatic interactions between STAB and SiQDs promoted the formation of more connection points, effectively extending contour length and improving viscoelasticity of VES fracturing fluids. In addition, the controlled experiments about SiQDs modified with propyltrimethoxysilane confirmed the dominant roles of the electrostatic interactions rather than hydrophobic interactions between SiQDs and STAB. To our knowledge, this work demonstrates the first successful application of SiQDs to improve the viscoelasticity of VES fracturing fluids for unconventional oil and gas development.
Jia et al. (Sat,) studied this question.
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