Experimental investigation on enhancing oil recovery using magnetic nanofluid as fracturing fluid in tight oil reservoir

Abstract

The potential of magnetic nanofluids as fracturing fluids in tight oil reservoir development is investigated. Hydrophobic magnetic nanoparticles (MNPs) are synthesized using a chemical co-precipitation method and characterized by Fourier transform infrared spectroscopy, dynamic light scattering, and scanning electron microscopy. A magnetic nanofluid is prepared as a pad fracturing fluid in accordance with the aforementioned methodology. Significantly, the effects of homogeneous and heterogeneous magnetic fields were evaluated on oil recovery and formation damage through core flooding experiments. The synthesized MNPs are hydrophobic, 20 nm in diameter, and stabilized by one layer of surfactant molecules in an aqueous solution. The nanofluid exhibits a relatively higher oil recovery than the surfactant solution because of its superior function of wettability alteration. The chaining behavior of MNPs under homogeneous magnetic fields leads to severe particle retention in the pore throats, which results in a significant decrease in core permeability. In contrast, the magnetic force gradient is unique to heterogeneous magnetic fields, resulting in a 40% increase in oil recovery at a magnetic intensity of 900 G near the core, while the permeability reduction is negligible. In conclusion, the retention of nanoparticles in pore throats represents a significant obstacle to the application of nanotechnology in tight reservoirs. The utilization of hydrophobic MNPs in conjunction with heterogeneous magnetic fields presents a potential solution to this conundrum.