Research on Enhanced Oil Recovery and In Situ Drag Reduction Mechanism of Janus Amphiphilic Carbon Nanotube Nanofluids.

Heavy oil reservoirs possess abundant reserves but currently exhibit low recovery efficiency, indicating significant untapped exploitation potential. This study developed a Janus amphiphilic carbon nanotube (JCMS18) nanoviscosity-reduction system (JC-F) by formulating laboratory-synthesized JCMS18 with cocamidopropyl betaine and sodium alcohol ether sulfate. Compared with existing nanofluid systems, the developed JC-F demonstrates superior performance at an ultralow concentration (0.12 wt %), achieving a viscosity reduction exceeding 99% and an EOR efficiency of over 20%. The oil-water-rock interaction mechanisms of JC-F were systematically investigated through interfacial activity experiments, emulsification performance evaluation, wettability alteration tests, static adsorption experiments, and molecular dynamics simulations. Results demonstrate that JCMS18 forms stable oil-in-water (O/W) emulsions (2-5 μm droplets) with 99% viscosity reduction and converts oil-wet surfaces to neutral-wet. Capillary pressure reduction experiments, axial pressure distribution measurements, and core flooding tests revealed 30% capillary pressure reduction (30 μm hydrophilic capillaries), 21.32%-24.76% enhanced oil recovery (523-1517 mD cores), and 40%-51.8% drag reduction. Synchronized midsection/injection-end pressure trends in sandpack tube experiments confirmed stable porous media migration. Oil film stripping experiments and microscopic flooding experiments identified synergistic mechanisms: emulsification-induced viscosity reduction, wettability alteration, and wedge-type pressure-driven oil stripping, improving displacement efficiency and sweep volume. These findings provide theoretical guidance for efficient heavy oil recovery.