Conduction and Dielectric Relaxation Mechanisms in Athabasca Oil Sands with Application to Electrical Heating

Six oil sands with increasing water and clay content were investigated for their electrical relaxation mechanisms using broadband dielectric spectroscopy with frequency (1 Hz to 1 MHz) and temperature (20-200 °C) to identify suitable operational strategies for electrical heating. Oil sands having least water and clay content showed a conduction relaxation mechanism following Jonscher's law due to Maxwell-Wagner (MW) polarizations at bound water interfaces between bitumen and silica grains. MW polarizations due to free water interfaces between 1 kHz and 1 MHz were observed for oil sands having pendular connected water channels between sand grains. Poor oil sands with water entrapped in fine clusters had a dominant dc conduction mechanism. Additionally, all oil sands displayed dipole relaxations due to bitumen molecules between 100 kHz and 1 MHz. Electrical properties increased as temperatures were increased from 20 to 120 °C, whereas a further increase from 120 to 200 °C resulted in reduction of these properties and dominance of ac conduction, causing all oil sands to behave the same irrespective of their grade.