Investigation of Novel Modified Nanoparticle-Enhanced Viscoelastic Surfactant Clean Fracturing Fluid System for Improving Oil Recovery in Low-Permeability Reservoirs

Summary Nanoparticle-enhanced viscoelastic surfactant (VES) fracturing fluid systems have attracted significant attention for their exceptional rheological properties and superior resistance to temperature and shear. In this study, we introduce a novel modified nano-silica (nano-SiO2)-enhanced VES clean fracturing fluid system developed to optimize performance and enhance oil recovery. We achieved this by deeply investigating the fluid’s rheological characteristics, thermal and shear stability, and self-assembly behavior. From both fracturing and spontaneous imbibition perspectives, we formulated and tested two VES systems: VES-A (without nano-SiO2) and VES-B (incorporating modified nano-SiO2 materials). These systems were based on a synthesized zwitterionic surfactant, erucamidopropyl hydroxysultaine (EAPHS), along with sodium salicylate (NaSal) and potassium chloride (KCl). Our findings indicate that modified nano-SiO2 can effectively alter the surface charge of the VES system, promoting the formation of more uniform and stable wormlike micelles (WLMs). Moreover, nano-SiO2 particles act as effective crosslinking sites for micelles through electrostatic adsorption or hydrogen bonding, thereby constructing a longer, more robust 3D micellar network that significantly enhances the system’s viscoelasticity and shear resistance. The VES-A system maintained a viscosity of 32 mPa·s after shearing at 120°C and 170 s⁻¹ for 60 minutes, yielding an imbibition oil recovery rate of 35.21%. In stark contrast, the VES-B system’s viscosity remained at 61 mPa·s after shearing under more demanding conditions (140°C and 170 s⁻¹ for 60 minutes), and its imbibition oil recovery rate reached 47.35%. Throughout the entire imbibition process, the VES-B system demonstrated superior oil displacement efficiency compared with the VES-A system, which is of great significance for the development of low-permeability and tight oil reservoirs. Crucially, the developed VES-B fracturing fluid system has demonstrated significant engineering success through its successful field application in multiple wells within a low-permeability shale gas block in the Sichuan Basin, China. For instance, the SW-1 well achieved a daily gas production of 1.5×10⁶ m³/d, a remarkable 18.7% increase compared to adjacent wells stimulated using conventional polymer slickwater systems. Collectively, these comprehensive laboratory findings and successful field applications highlight the substantial potential of nano-SiO2 materials for enhancing reservoir use in low-permeability oil and gas formations, thereby promoting the efficient development of shale gas resources.