Preparation of an amphiphilic BaTiO3 nanofluids and its application to oil displacement in low-permeability reservoirs

Abstract

The challenges of difficult injection and low recovery in low-permeability reservoirs significantly impact production efficiency. Nanofluid flooding presents a viable approach to improve to enhance recovery in such reservoirs. In this study, an amphiphilic J nano-BaTiO₃ particle (JNB-P) with a particle size of 50–90 nm was synthesized. Characterization results indicated that, compared to unmodified Nano BaTiO₃ particles, the JNB-P molecules introduced long-chain groups, leading to improved dispersion and a transition of the particle surface from hydrophilic to amphiphilic. Settling experiments identified the optimal dispersive nanofluid (JNB-FS) as a combination of 0.25 % PEG400 and 0.025 % JNB-P, with complete settling time for nanoparticles decreased as temperature or salinity increased. Emulsification experiments demonstrated that, at a water-to-oil volume ratio of 5:5, JNB-FS and crude oil successfully emulsified into an O/W emulsion with an average particle size of 0.791 μm. Interfacial tension experiments revealed that the interfacial tension of oil–water decreased by more than 50 times after adding JNB-FS. Furthermore, with increasing temperature, the degree of emulsification initially increased before decreasing, while emulsion stability, interfacial tension, and expansion modulus gradually decreased. As salinity increased, the degree of emulsification and emulsion stability declined, with interfacial tension first decreasing and then increasing, and the expansion modulus initially rising before falling. Wetting improvement experiments indicated that the core transitioned from lipophilicity to strong hydrophilicity after soaking in JNB-FS for 60 h. Finally, flow experiments demonstrated that compared to first water flooding, the oil recovery increased by 15.82 %. The oil displacement mechanism of JNB-FS primarily involved reducing interfacial tension, enhancing rock wettability, emulsification, and improving the permeability of the injected water via nanoparticles.