Objective To address the instabile properties and poor thermal/salt tolerance of polyacrylamide drag reducers in high-temperature/high-salinity reservoirs, this study developed a nano-composite drag reducer integrated with additives to establish an advanced slick water fracturing fluid system with a significant thermal/salt tolerance.

Method The nano-composite drag reducer ZJYD-SiO₂ was prepared using AM, AMPS, hydrophobic monomer DMHAAB and KH-570 modified nano-SiO₂ as raw materials. After the optimal concentration was selected based on the drag reduction rate test results, the breaker ammonium persulfate and the clean up additive cocoyl hydroxyethyl betaine were selected based on parameters such as the viscosity of the breaker fluid and interfacial activity, and the nano-composite slick water fracturing fluid ZJYD-SiO₂ system was constructed. A series of performance index comparisons were made between the slick water fracturing fluid system composed of ZJYD-SiO₂ and the drag reducer ZJYD without modified nano-SiO₂, including drag reduction performance and rheological performance under different experimental conditions.

Result The results showed that in terms of drag reduction performance, the drag reduction rate of the slick water fracturing fluid system first increased and then decreased with the increase of flow rate, and decreased with the increase of temperature, salinity and pipe diameter. However, the drag reduction rate was always greater than 70% and higher than that of the ZJYD system. In terms of viscoelasticity tests, the energy storage/loss modulus was greater than that of the latter. In terms of temperature and shear resistance tests, the viscosity attenuation of the former was lower than that of the latter. The settling rate test of proppants also showed the same trend.

Conclusion The key properties of the ZJYD-SiO₂ system are superior to those of the ZJYD system, indicating that the nano-composite drag-reducer has excellent application performance. The introduction of nano-materials can enhance the extensibility of the polymer chain, forming a more stable spatial network structure.