Evaluation of Cellulose Nanoparticles Synthesized from Paper Waste as High-Temperature, High-Salinity Nanofluid Agents for Enhanced Oil Recovery

Abstract High-temperature and high-salinity reservoir conditions had long compromised the stability and performance of conventional EOR chemicals such as polymers and surfactants, creating the need for more resilient materials. Consequently, this study aimed to assess cellulose nanoparticles (CNP) synthesized from wastepaper as a thermally stable and sustainable alternative for enhancing oil recovery. The CNP were synthesized and characterized using microscopy, particle size analysis, FTIR, XRD, and TGA to evaluate morphology, functional groups, crystallinity, and thermal stability. The methodology yielded CNP in the 17.6–19.6 nm range, and microscopic examination confirmed that their chemical structure remained largely intact after synthesis. Rheological testing showed that the nanofluids displayed shear-thinning behavior, with viscosities ranging from 26.32 to 16.71 mPa·s at a shear rate of 1000 s−1. Interfacial tension decreased significantly from 23.02 to 5.9 mN/m with increasing CNP concentration, while contact angles shifted from oil-wet (142.5°) to water-wet (10°), indicating strong wettability alteration under reservoir conditions. Core flooding experiments demonstrated additional oil recoveries of 7.8%, with a Recovery Factor of 59.1% for xanthan polymer and additional oil recoveries of 28.7%, with a recovery factor of 73.9% for CNP, confirming the superior displacement efficiency of the nanoparticles. Emulsion tests further revealed enhanced stability, reduced coalescence, and improved mobility-ratio effects in the presence of CNP. Overall, the results concluded that cellulose nanoparticles offered a robust, environmentally friendly, and high-performance option for EOR applications in high-temperature, high-salinity reservoirs.