Amphiphilic Titania Nanocolloids for Oil Mobilization in Saline and Thermal Extremes

The nanofluid flooding tertiary oil recovery method to augment the production of oil from matured wells is limited by nanoparticle instability under high salinity and at high temperatures, rock surface adsorption, formation water incompatibility, and economic feasibility. To address these issues, this study proposes a nanofluid for oil recovery from harsh reservoir conditions. Janus nanoparticles (JNPs) were synthesized by selective surface modification with a nonionic surfactant, which was confirmed through Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) analyses. These JNPs demonstrated excellent colloidal stability in high-salinity brines and in the presence of divalent cations, showcasing resilience to harsh reservoir conditions. Their amphiphilic nature remarkably reduced interfacial tension (IFT) at the oil–brine interface even at an ultralow concentration of 0.005 wt %. Notably, 60.5% IFT reduction for 4 wt % NaCl and 44.5% for 6 wt % NaCl with 2 wt % CaCl2 were attained. Furthermore, JNPs effectively altered the wettability from oil-wet to water-wet and demonstrated high oil displacement across various salinity conditions and high reservoir temperatures. Oil displacement on the model surface was tested under both static and dynamic conditions. In spontaneous imbibition tests for carbonate cores, high oil recovery rates of 92.5% for 4 wt % NaCl and 78.4% for 5 wt % NaCl with 2 wt % CaCl2 were observed. This was aided by excellent sweep efficiency, where 0.005 wt % JNPs in crude oil–water emulsions reduced the crude oil viscosity by about 85.3% at 50 s–1. This study highlights the promising potential of robust, low-cost, and environmentally friendly JNPs for advancing oil recovery technologies.