Effect of asphaltene adsorption on the magnetic and magnetorheological properties of heavy crude oils and Fe3O4 nanoparticles systems

Abstract

An essential understanding of the adsorptive phenomena involving nanomaterials and asphaltenes has received considerable attention in oil recovery and production applications. Particularly, iron oxide-based nanoparticles have emerged as advanced materials due to their unique physicochemical properties, including thermal conductivity and superparamagnetism. On this basis, the kinetics and adsorption isotherms of magnetite (Fe3O4) nanoparticles/asphaltene systems were investigated, as well as the synergistic effect of resins acting as stabilizing colloidal agents. The results indicated rapid asphaltene adsorption that, essentially, follows the phenomenological external mass transfer (EMT) model. At the equilibrium, the asphaltene adsorption was adequately described by the monolayer Langmuir model. By these findings, it was studied for the first time the effect of the adsorbed asphaltenes on the magnetic dipolar interactions in nanoparticles/asphaltene powder state configurations, by applying a simple analytical model based on magnetic susceptibility and demagnetizing field concepts. It was proven accurately that asphaltenes coated the surfaces of the nanoparticles forming layers that stimulate a steric repulsive barrier between particles and, thus, reducing the intensity of interactions. Accordingly, a theoretical method was validated to estimate the magnetic-size distribution parameters by comparison with the physical distribution data obtained by Transmission Electron Microscopy (TEM). Finally, from the magnetically modified dynamic rheological properties, it was inferred that isotropic aggregates are naturally formed in the absence of the magnetic field, and these morphological features were not dramatically changed after the imposition of the field, leading to direct extrapolation of the modeling-based procedure for powders to real colloidal configurations applied in oil field operations.