Synthesis and application of rice husk silica nanoparticles for chemical enhanced oil recovery

Silica (SiO2) nanoparticles were synthesized from rice husk (RH) via wet milling method and evaluated for enhanced oil recovery (EOR) applications. Physical properties of RH-SiO2 nanoparticles (RH-SNP) with its size distribution were explored through field emission scanning electron microscopy (FESEM) and dynamic light scattering (DLS). Stability, functional groups and purity of RH-SNP were determined by zeta potential, Fourier-transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), respectively. Effect of RH-SNP on the precipitation and thermal degradation of oilfield polyacrylamide (HPAM) was studied using Brookfield RST rheometer. Interfacial tension (IFT) properties of RH-SiO2 polymeric nanofluid (RH-SPNF) at interface of oil and water (O/W) were investigated using Easy-Dyne KRUSS tensiometer. Subsequently, oil displacement efficiency of RH-SPNF was determined and compared with oilfield HPAM at reservoir conditions using Fars EOR high-pressure high-temperature (HPHT) core flooding equipment. The wet milling method was effective in producing RH-SNP of size ranges 43.9-59.5 nm with a purity of 98% through the mechanism of nucleation, Brownian motion and coalescence. Rheological results show that RH-SNP inhibited the precipitation and thermal degradation of oilfield HPAM. IFT of RH-SPNF showed a monotonic tendency as temperature increased. HPAM and RH-SPNF flooding showed an incremental oil recovery of approximately 10% and 24%, respectively. Emulsion generated using RH-SPNF shows higher stability and resistance to coalescence. Finally, mobility ratio of water flooding approaches unity faster, compared to HPAM and RH-SPNF. Overall, the low energy utilization, use of low-cost and benign raw material make RH-SNP and the extraction method an appropriate substitute to commercially available SiO2 nanoparticles.