Stability of Water/Crude Oil Systems Correlated to the Physicochemical Properties of the Oil Phase

A characterization of 30 crude oils has been performed to determine the relative level of influence that individual parameters have over the overall stability of w/o emulsions. The crude oils have been analyzed with respect to bulk and interfacial properties and the characteristics of their w/o emulsions. The parameters include compositional properties, acidity, spectroscopic signatures in the infrared and near-infrared region, density, viscosity, molecular weight, interfacial tension, dilational relaxation, droplet size distribution, and stability to gravitationally and electrically induced separation. As expected, a strong covariance between several physicochemical properties was found. Near-infrared spectroscopy proved to be an effective tool for crude oil analysis. In particular, we have showed the importance of the hydrodynamic resistance to electrically-induced separation (static) in heavy crude oil-water emulsions. A rough estimate of the drag forces and dielectrophoretic forces seemed to capture the difference between the 30 crude oils. Given enough time, water-in-heavy oil emulsions could be destabilized even at very low electric field magnitude (d.c.). When droplets approach each other in an inhomogeneous electric field, strong dielectrophoretic forces disintegrate the films and result in coalescence. The relative contribution from film stability to the overall emulsion stability may therefore be very different in a gravitational field compared to that in an electrical field.