Investigation on enhanced oil recovery potential of active nano-SiO2 in high-temperature and high-salinity reservoirs at core and pore scale

• The structure of active nano-SiO 2 was optimized through molecular simulation. • Displacement experiment was conducted to investigate the EOR potential of active nano-SiO 2 at core scale. • NMR experiment was conducted to investigate the EOR potential of active nano-SiO 2 at pore scale. Nano-SiO 2 , with unique characteristics, is a promising candidate for addressing the limitations of chemical flooding systems based on polymers and surfactants in enhanced oil recovery (EOR) from high-temperature and high-salinity reservoirs. In this study, the structure of active nano-SiO 2 was optimized using molecular dynamic simulation to endow the nano-SiO 2 with the ability to simultaneously improve sweeping efficiency and displacement efficiency. Subsequently, the interactions between active nano-SiO 2 and crude oil were investigated. Finally, the EOR potential of active nano-SiO 2 in high-temperature and high-salinity reservoirs was evaluated through displacement experiments. Molecular simulation results indicated that nano-SiO 2 modified with fatty alcohol polyoxyethylene ether carboxylic acid exhibited excellent stability and emulsifying properties at 110 °C and 18 × 10 4 mg/L salinity. Experimental results demonstrated that active nano-SiO 2 could reduce the interfacial tension to 10 −3 mN/m level and improve wettability. Moreover, an active nano-SiO 2 dispersion solution could form a water-in-oil emulsion with crude oil; the viscosity of the emulsion was 2–10 times that of crude oil. As a result, active nano-SiO 2 enhanced the sweeping and displacement efficiency simultaneously, increasing the recovery rate by more than 25 %. These findings suggest that active nano-SiO 2 provides a novel technical path and implementation strategy for the development of high-temperature and high-salinity oilfields.