Janus SiO2-surfactant dispersion designed for enhanced imbibition oil recovery in ultra-low permeability reservoirs

The use of nanofluids in formations with high temperatures and high salinity is currently encountering significant obstacles. Therefore, a Janus SiO 2 -surfactant dispersion consisting of Janus nanoparticles and surfactants was constructed in the current study. The Janus SiO 2 -surfactant dispersion is resistant to both high temperatures and high salinity. The Janus SiO 2 -surfactant dispersion, consisting of Janus SiO 2 nanoparticles and the non-ionic surfactant Tween80, is abbreviated as JASN-T80 hereafter. The system can be dispersed and kept stable for one week at a salinity of 30,000 mg/L and a temperature of 85 ℃. The concentration of f nanoparticles and surfactant in the system was optimized at 0.02 wt% Janus SiO 2 nanoparticles + 0.04 wt% Tween80 based on the particle size. An assessment was conducted to measure the system's capacity to decrease interfacial tension and alternate wettability. The interfacial tension between oil and water was reduced to 1.21 mN/m. The JASN-T80 system demonstrates a notable capacity to change wettability by decreasing the contact angle of water on an oil-wet rock surface from 100.6° to 70.5°. The combination of nanoparticle and surfactant leads to a synergistic effect, resulting in an imbibition recovery of 44.28 % for ultra-low permeability core. This work provides a novel concept for the advancement and utilization of nanofluid imbibition system for unconventional reservoir.