Integrating synthesized citric acid-coated magnetite nanoparticles with magnetic fields for enhanced oil recovery: Experimental study and mechanistic understanding

Nanofluid injection has emerged as an attractive enhanced oil recovery (EOR) process in the past decade. These fluids improve oil recovery by reducing interfacial tension (IFT), modifying wettability, and reducing mobility ratio. In this communication, magnetite citric acid-coated nanoparticles (NPs) were synthesized by an affordable, facile and one step method and then characterized using Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Dynamic light scattering (DLS). Afterward, the microscopic and macroscopic efficiencies of oil recovery in heterogeneous and homogeneous 2D micromodels were investigated in the presence of magnetic field. Citric acid-coated magnetite NPs started to respond to the magnetic field around the intensity of 800 Gauss and also showed the maximum ultimate recovery factor at the intensity of 2750 Gauss. In addition, citric acid coated magnetite NPs provided more enhanced oil recovery factor compared to hematite NPs, because of reducing interfacial tension (IFT) between the oil and injection fluid, altering surface wettability from oil-wet to water-wet, promoting the NPs distribution in porous media, and generating column-like structure in the presence of magnetic field. In fact, magnetite NPs act as piston toward the magnetic field by creating a column which sweeps the oil and increases production. Furthermore, citric acid-coated magnetite NPs flooding increased ultimate recovery factor more than polymer and hematite NPs flooding.