Preparation of Amphiphilic Janus-SiO2 Nanoparticles and Evaluation of the Oil Displacement Effect

In order to meet the requirements of tertiary oil recovery technology in a low-permeability, dense, and high-salt reservoir, gaseous SiO2 nanoparticles were modified with trichloro(octyl)silane and aminopropyl triethoxysilane by interface protection modification, and amphiphilic Janus-SiO2 nanoparticles with hydrophobic carbon chain and hydrophilic amino group were prepared. The basic properties of amphiphilic nanoparticle dispersion were evaluated by surface interfacial tension and wettability tests, and the oil displacement effect of amphiphilic nanoparticle dispersion was investigated. The results show that the size distribution of Janus-SiO2 nanoparticles with n-octyl as the hydrophobic carbon chain and amino group as the hydrophilic headgroup is uniform, and they have good dispersion in mineralized water. The change of salinity has little effect on the interfacial activity. The interfacial tension between the amphiphilic nanoparticle dispersion and crude oil is always on the order of 10–2 mN/m, and the amphiphilic nanoparticle dispersion has good interfacial activity. Amphiphilic nanoparticles adsorbed on the rock surface can enhance the hydrophilicity of the rock surface. Amphiphilic nanoparticle dispersion liquid has a certain effect of improving oil recovery in the environment of high-salt and low-permeability reservoir. Under the condition of 65 °C and salinity of 8000 mg/L, injection of 0.5 PV 0.05% amphiphilic nanoparticle dispersion can enhance oil recovery by 14.6% on the basis of water flooding. The mechanism of amphiphilic nanoparticles to improve the recovery efficiency of low-permeability tight high-salt reservoir mainly includes reducing the oil–water interfacial tension, changing the rock wettability, and enhancing the shear viscosity of oil and water interface and the interfacial film strength, which has excellent potential application prospect in the development of low-permeability tight high-salt reservoir.