Analysis of Crude Oils by Frequency Domain Spectroscopy—Effect of Composition and Physical Properties on Conductivity and Dielectric Response

Abstract

The dielectric properties and the composition of fourteen light to heavy crude oils have been analyzed. Frequency domain spectroscopy (FDS) has been used in order to determine their dielectric response in the frequency range 0.01 to 1000 Hz. For all the crude oils, over the whole frequency range under study, dielectric loss, ϵ″, shows a linear dependence of frequency indicating a pure direct current (DC) conductivity. As temperature is gradually increased, the dielectric loss, ϵ″, increases as well, showing a strong temperature dependence. The storage modulus, ϵ′, shows an explicit behaviour at low frequency that could be due to adsorption of oil components onto the electrodes. We tried to correlate some physical and chemical properties (density, viscosity, SARA, TAN, water content) of the studied crude oils with their conductivity measured at various temperatures. No correlation was found and different hypothesis are suggested by the authors to explain this phenomenon.

Keywords:

• Conductivity
• crude oils
• dielectric response
• viscosity

Acknowledgments

This work is funded by the project “Electrocoalescence—Criteria for an efficient process in real crude oil systems”; co-ordinated by SINTEF Energy Research. Contact person is L. E. Lundgaard. The project is supported by The Research Council of Norway, under the contract no: 169466/S30, and by the following industrial partners: Aibel AS, Aker Solutions AS, StatoilHydro ASA, BP Exploration Operating Company Ltd., Shell Technology Norway AS, Petrobras, Saudi Aramco.

The companies in the JIP Flucha III program are acknowledged for providing the crude oils.

Hanne Skogesta is thanked for her efforts in the lab.