ABSTRACTNanoparticles have received much attention as potential agents to enhance oil recovery (EOR) in low‐permeability reservoirs recently. Compared to water or polymer solutions, they exhibit small sizes and superior rheology, which is important for low porosity and permeability petroleum rocks with nanopores. While the use of nanofluids as injection fluids for enhanced oil recovery has been explored in past studies, application conditions of hydrophobic nanoparticles have not been explored to date. In this study, different hydrophobic functional groups were used to graft on the surface of SiO2 nanoparticles for wettability alteration applications. The synthesized nanoparticles were identified and optimized using contact angle measurement and Fourier‐transform infrared spectroscopy (FTIR). At last, core flowing experiments combined with NMR tests were conducted to study the fluid flow properties of low porosity and permeability reservoirs. Based on the results obtained in this study, the nanoparticles modified by KH570 have the best hydrophobic effect, the optimal reaction conditions including pH = 6, reaction temperature of 84°C, and modifier dosage of 25%. The proportion of 30% between nanoparticles and pores has been recommended as the ideal condition for use in improving flow capacity in low‐permeability reservoirs. Our findings offer fresh insights into the fundamental investigations on the implications of nanofluid injection for enhanced oil recovery at a microscale scale.