Abstract: Shale oil reservoirs within the Fu-2 Member of the Subei Basin are characterized by nanoscale pores and complex pore structures, which impede penetration by conventional fluid systems and result in low imbibition oil recovery. Utilizing authentic downhole core samples, this study investigated the oil displacement behavior of nanoemulsions in the Fu-2 Member through core property analysis, crude oil composition analysis, and spontaneous imbibition experiments monitored with real-time nuclear magnetic resonance (NMR) scanning. Experimental results demonstrate that nanoemulsions enhance shale imbibition by reducing oil-water interfacial tension and altering rock wettability. Compared to conventional fluids, the CNI-1 and CNN-1 nanoemulsion systems increased imbibition recovery by 17.5% and 15.5%, respectively. Post-hydration micro-fracture development was observed on shale surfaces, increasing in complexity over time. Core mass gain was rapid during the initial 7 days of immersion, slowed significantly between days 7 and 21, and stabilized thereafter. Field application in Well Ji-1901 demonstrated improved production performance, providing practical guidance for shale oil exploration and development in the Subei Basin.