Deep Eutectic Solvents-Derived Functionalized Cellulose Nanoparticles for Interfacial and Wettability Control in Enhanced Oil Recovery

Abstract This study aimed to synthesize and evaluate cellulose nanoparticles (CNP) for enhanced oil recovery by examining their wettability alteration, interfacial tension, and oil displacement performance. CNP were synthesized using a Deep Eutectic Solvent (DES) method and surface-modified with (3-Aminopropyl)triethoxysilane (APTES), followed by characterization through X-ray Diffraction (XRD), Elemental Dispersive X-ray (EDX), and electron microscopy to confirm phase purity, elemental composition, and morphological features. The nanofluids were then assessed under reservoir-relevant conditions to determine their capability to reduce interfacial tension and modify rock wettability. The synthesis yielded CNP with multiple morphological structures and high purity, while EDX confirmed successful APTES grafting and thermal analysis indicated improved stability with higher residual char at 500 °C. The nanofluids reduced interfacial tension to approximately 4.2 mN/m at 0.2 wt% under 2.2 wt% salinity and 90 °C, and contact angle measurements showed a decrease to about 15.4° at 0.2 wt%, indicating strong wettability alteration toward a water-wet state. Core analysis revealed that CNP nanofluids improved oil displacement efficiency by roughly 10.2% after water flooding, leading to an oil recovery of 71.2%. Overall, the study concluded that CNP provided a thermally stable, environmentally friendly, and highly effective nanofluid system suitable for EOR applications in harsh reservoir environments.