Green synthesis of zinc oxide nanoparticles using Enterobacter cloacae microorganism and their application in enhanced oil recovery.

Employing safe and inexpensive methods for the synthesis of biocompatible nanoparticles (NPs) can be very challenging. Green synthesis refers to the process of synthesizing nanoparticles without using toxic and dangerous chemicals. One of the applications of nanoparticles is increasing production from oil reservoirs, known as enhanced oil recovery (EOR). The main aim of the current study is the biosynthesis of zinc oxide (ZnO) nanoparticles (NPs) using Enterobacter cloacae (Persian Type Culture Collection (PTCC): 1798) microorganism, extracted from the formation water of one of the southwestern Iranian reservoirs, as a novel approach in EOR applications. Several analytical methods, including Fourier transform infrared (FTIR), field emission scanning electron microscope (FSEM), X-ray diffraction (XRD), dynamic light scattering (DLS), energy dispersive X-ray spectroscopy (EDS), and zeta potential were used to analyze the produced NPs. The FESEM analysis confirmed the amorphous form of the nanoparticles and estimated their size in the range of 32 to 58 nm. In investigating the effect of synthesized nanoparticles on interfacial tension (IFT) and stability tests, three levels of base fluids (distilled water, seawater, and diluted sea water) and five levels of nanoparticle concentrations (0, 100, 500, 1000, and 2000 ppm) were considered. The IFT analysis showed that an increase in nanoparticle concentration causes a decrease in the IFT. Also, ZnO nanoparticles were chosen at concentrations of 500 and 1000 ppm for wettability alteration and the EOR test through injection into porous media. The results for the EOR test demonstrated a maximum oil recovery factor of 56% for nanofluid injection with a concentration of 1000 ppm with diluted seawater as the base fluid. Furthermore, oil recovery factors of 43% and 49% were achieved by injection of distilled water and seawater with a concentration of 1000 ppm, respectively.