Electrical conduction mechanisms in green river oil shale

Abstract

Results on the dielectric behavior of Green River oil shale in alternating current fields are reported. Oil shale samples with oil yields in the range 10–40 gallons per ton have been obtained by coring of the rock perpendicular to the bedding planes. Trends in the variation of AC conductivity, dielectric constant and loss factor are studied with frequency and temperature as the variable parameters. Measurements have been carried out in the range of frequencies 1 Hz-1 MHz and temperatures 25–500 °C. Increases in the conductivity of several orders of magnitude are observed for the samples heated from room temperature to 500 °C. The abnormally high values of dielectric constant and loss factor point toward the importance of Maxwell—Wagner interfacial polarization in electrical conduction mechanisms in oil shale. Striking variations in the conductivity—temperature curves are found before and after decomposition of the organic matter in the shale. The results of the present study indicate that measurement of electrical conductivity could be utilized to monitor the progress of retort fronts in oil shale beds.