Multiscale investigation of CNC-stabilized foams: From interfacial design to energy-relevant fluid displacement

This study investigates the mechanisms of enhanced oil recovery using a cellulose nanocrystal (CNC)-stabilized foam system. A systematic approach—encompassing foam characterization, scanning electron microscopy (SEM), interfacial tension and wettability measurements, microfluidic displacement visualization, and low-field nuclear magnetic resonance (LF-NMR) analysis—was employed to evaluate the CNC-enhanced foam system. The results demonstrate that the optimized formulation improved foamability and stability, with foam volume and half-life increased by 15.7% and 35.2%, respectively. The incorporation of CNCs reduced the contact angle from 64.9° (conventional system) to 49.6°, indicating enhanced wettability alteration capability. Real-time microfluidic displacement experiments and LF-NMR analysis revealed that the CNC-enhanced nanofluid-assisted water alternating gas (NWAG) process increased the local sweep efficiency to 47.21% and improved micro-pore recovery by 28.5 percentage points. The NWAG process achieved an average ultimate oil recovery of 50.5%, demonstrating a 15.1 percentage-point improvement compared with conventional WAG injection.