Development and Performance Evaluation of the Nanoparticle-Enhanced Seawater-Based High-Temperature-Resistant Guar Gum Fracturing Fluid System

Abstract To address the problems of low viscosity retention, and insufficient sand-carrying capacity for seawater-based fracturing fluids in deepwater high-temperature reservoirs, this study enhanced the fracturing fluid by adding modified nano-SiO2 (M-NS). A seawater-based, high-temperature-resistant fracturing fluid system was constructed from M-NS and carboxymethyl hydroxypropyl guar gum (CMHPG). The results showed that 3-aminopropyltriethoxysilane (APTES) modification improved, to a certain extent, the dispersion stability and interfacial compatibility of nano-SiO2 (NS) in the seawater-based CMHPG solution. The optimal formulation of the M-NS-enhanced system was 0.4 wt % CMHPG, 0.5 wt % organic zirconium crosslinker, 0.08 wt % M-NS, 0.1 wt % APS, and 0.05 wt % SDS. After shearing at 200 °C and 100 s–1 for 2 h, the retained viscosity was 60.03 mPa·s, which was 1.42 times that of the conventional system. At 95 °C, no proppant settling was observed at sand ratios of 10%, 20%, and 30%. In addition, the fracturing fluid exhibited favorable breaking and flowback performance, dynamic leak off control performance, and formation-damage performance. Investigation of the high-temperature-resistance mechanism revealed that the M-NS-enhanced fracturing fluid system demonstrated excellent viscosity recovery and nonlinear elastic response under large strain. This improvement is attributed to the formation of physical crosslinking through hydrogen bonding between the −NH2 on the M-NS surface and the hydroxyl and carboxymethyl groups on the polymer chains. This physical crosslinking mechanism likely synergizes with the organic zirconium chemical crosslinking to construct a dual-network structure. Moreover, M-NS is uniformly dispersed in the CMHPG base fluid, acting as rigid nucleation points and a skeleton. Consequently, the network skeleton of the enhanced gel is significantly thickened, and the structure of the gel is enhanced. This study provides a seawater-based, high-temperature-resistant guar gum fracturing fluid system for deepwater and ultra-deepwater high-temperature reservoirs, demonstrating significant engineering application potential.