Microfluidic and Numerical Investigation of Trapped Oil Mobilization with Hydrophilic Magnetic Nanoparticles

Abstract

Nanoparticles have great potential to mobilize trapped oil in reservoirs by reducing the oil-water interfacial tension, altering the rock wettability, stabilizing foams and emulsions, and heating the reservoir to decrease the oil viscosity. However, the direct application of magnetic forces on paramagnetic nanoparticles in reservoir engineering applications has not be extensively investigated. We demonstrate the enhanced oil recovery (EOR) potential of hydrophilic magnetic nanoparticles in oil production by direct observation using microfluidics. We studied the mobilization of oil blobs by a ferrofluid (a suspension of hydrophilic magnetic nanoparticles in water) in a converging-diverging channel with varying depth (so-called 2.5D micromodel). The channel had a varying depth of 10-30 microns and a varying width of 50-200 microns, approximating a flow path in the rock. The nanoparticle suspension was injected at 0.1 microliter/hour. The channel was made of glass and thus the water-based ferrofluid was the wetting fluid. Initial ferrofluid flooding experiments were performed under a static magnetic field. This magnetic field caused oil droplet deformation, dynamic break-up into smaller droplets, and subsequent residual oil saturation reduction. Significant oil blob displacement was observed within 2 hours after the magnetic field was applied. During the flooding, the oil saturation within the observation area of the micromodel reduced from 27.4% to 12.0%. We then hypothesized that a changing field would have an even larger effect in saturation reduction. We have thus designed experiments with a magnetic field of the same magnitude slowly rotating under the micromodel. We subsequently observed a completely different phenomenon, namely self-assembly of oil droplets, indicating formation of the hydrophilic magnetic nanoparticles microstructures (chains under the magnetic field). These magnetic nanoparticle microstructures were ever-changing under the rotating magnetic field. While the ability of ferrofluid to rotate small blobs was in itself interesting, in experiments without actual flooding (and thus synergy of hydrodynamic and magnetic forces) we did not observe any additional oil recovery.

Digital Modeling of Increasing the Efficiency of Water Insulation in the Bottom-Hole Zone of a Well With Various Injection Agents

“…The technology is neutral in relation to the intensity of corrosion, the rate of salt deposition, the development of sulfate-reducing bacteria in oilfield equipment, and also does not affect the preparation process and the quality of commercial oil. (Wang et al, 2020).…”

12012 fundamental mechanisms behind nanotechnology applications in oil and gas: Emerging nano-EOR processes

“…Frontiers in Nanotechnology frontiersin.org magnetic field improves oil recovery when the magnetic field direction is along the flow direction. However, Wang et al developed a 3D model based on volume of fluid method and predicted the prohibits the oil recovery when the magnetic field direction is transverse to the flow direction, which is in contrary to their experimental results, hinting the presence of other mechanisms (Wang et al, 2021), (Wang et al, 2020). Magnetic nanoparticles form temporal micro-structures when exposed to external disturbances of either magnetic fields (Robbes et al, 2011), (Tracy and Crawford, 2013) or shears (Ishida et al, 2021), as shown in Figure 15.…”

“…Even when a uniform external magnetic field H is applied, the magnetization M and the magnetic flux density B is non-uniform at the pore scale because of the contrast of magnetic permeabilities of rock, oil, and brine. As a result, the corresponding magnetic-induced pressure is thus non-uniform in the ferrofluid as the flooding fluid (Prodanovic et al, 2010), (Soares et al, 2014;Wang and Prodanovic, 2017;Wang et al, 2020;Wang et al, 2021), as shown in Figure 14. This non-uniform magnetic pressure leads to deformation of the oil-ferrofluid interface and helps the mobilization of the oil droplet in the pore space.…”

“…This non-uniform magnetic pressure leads to deformation of the oil-ferrofluid interface and helps the mobilization of the oil droplet in the pore space. Prodanović et al developed 2D models based on the level-set method to analyze the equilibrium state of the trapped oil droplets and the corresponding oil saturation change with and without the static magnetic field (Soares et al, 2014), (Wang et al, 2020). They predicted that a static…”

“…Wang et al experimentally demonstrated the EOR effect of a 2.6 mT static magnetic field transverse to the flow direction in a ferrofluid flooding despite of unsuccessful approaches by other researchers, as shown in Figure 16 (Wang et al, 2021), (Wang et al, 2020). They measured the oil saturation in a micromodel during a ferrofluid flooding before and after the application of an external magnetic field.…”