SiO2 nanoparticle-assisted low-concentration viscoelastic cationic surfactant fracturing fluid

Attributing to its advantages including no residue, low friction and complete gel breaking, viscoelastic surfactant (VES) fracturing fluids are attracting more and more attention. However, high price and high consumption restrict the wide applications of VES. SiO2 nanoparticle-assisted VES fracturing fluid (NAVES) with low concentration is proposed in this study. The NAVES system consisting of 1% EDAA and 0.01% SiO2 maintains a shear viscosity of above 33 mPa center dot s at 70 degrees C for 2 h; in contrast, the viscosity of a 1% EDAA (VES) solution is 24 mPa center dot s at 70 degrees C for 2 h. This could be attributing to the formation of a strong dynamic network structure, in which the surfactant micelles attach to the surface of SiO2 nano-particles that are negatively charged through electrostatic interactions. The pseudo-crosslinking between the SiO2 and micelles also improves the shear resistance and relaxation time of the VES, without affecting the gel breaking performance. The NAVES system could break completely within 100 min, as reflected by the fact that its viscosity decreased to less than 3 mPa center dot s. The settling rate of quartz sand in an EDAA/SiO2 system at 25 degrees C was 0.0021 cm/s, which was lower than that of traditional VES fracturing fluid. Therefore, NAVES could serve as a low-concentration hydraulic fracturing fluid. In addition, the current study provides a cost-effective approach for hydraulic fracturing. (C) 2018 Elsevier B.V. All rights reserved.