Numerical and experimental evaluation of ferrofluid potential in mobilizing trapped non-wetting fluid

Abstract:

Ferrofluid is a stable dispersion of paramagnetic nanosize particles in a liquid carrier which are magnetized in the presence of magnetic field. Functionalized coating and small size of nanoparticles allows them to flow through porous media without significantly compromising permeability and with little retention. We numerically and experimentally investigate the potential of ferrofluid in mobilizing trapped non-wetting phase. Numerical method is based on a coupled level set model for two-phase flow and an immersed interface method for finding magnetic field strength, and provides the equilibrium configuration of an oleic (non-wetting) phase inside some pore geometry in the presence of dispersed excitable nanoparticles in surrounding water phase. The magnetic pressures near fluid-fluid interface depend locally on the magnetic field intensity and direction, which in turn depend on the fluid configuration. Interfaces represent magnetic permeability discontinuities and hence cause disturbances in the spatial distribution of the magnetic field. Experiments are conducted in micromodels with high pore-to-throat aspect size ratio. Both numerical and experimental results show that stresses produced by the magnetization of ferrofluids can help overcome strong capillary pressures and displace trapped ganglia in the presence of additional mobilizing force such as increased fluid flux or surfactant injection.