Dielectric Properties of Asphaltene Solutions: Solvency Effect on Conductivity

Electrical demulsification is considered an elegant method to enhance the separation of water-in-crude-oil emulsions. Understanding the mechanisms involved during this process remains a challenge for the further development of this separation method. The aim of this study is to elucidate the influence of the aggregation state of the asphaltenes on their conductivity, to determine the mechanisms governing conductivity in crude oils. Dielectric properties of two different asphaltenes extracted from crude oils (labeled CrA and CrB) and their solutions diluted in toluene or heptane were measured by frequency domain spectroscopy. When the heptane volume fraction increases, conductivity decreases. It also appears that the conductivity decreases with an increasing aggregate size. Conversely, decreasing the aggregate size increases the mobility of the charge carriers in the system and, consequently, increases the conductivity. On the basis of these observations, we propose here that the conductivity of asphaltenes is mostly governed by their mobility. The possible application of this method for determining the critical nanoaggregate concentration (CNAC) of asphaltenes is also evaluated and discussed.