Dielectric logging tools have been used for some time in attempting to characterize oil reservoirs, and in particular to provide in-situ measurements of oil and water saturation. The particular sensitivity of basic electrical measurements, e.g. resistivity, to the presence of water made the original use of this approach most relevant to the determination of water-filled porosity.
In-depth dielectric spectroscopic analyses reveal contributions from underlying processes in materials, including electronic, ionic (electric double layer, EDL) and interfacial (Maxwell-Wagner, M-W) polarization, as well as molecular orientation. Our particular objective is the evaluation of dielectric spectroscopy as a means of characterizing the physico-chemical and structural characteristics of oil sands. Relatively recently, there has been a resurgence in interest in the application of dielectric techniques to unconsolidated heterogeneous systems. The present study builds on recent developments in the literature, and, specifically to determine the extent to which the potentially dominant effects of water can be overcome in order to access additional information, such as particle size and wettability.
This initial study has therefore involved investigating a range of synthetic oil sands systematically prepared from bitumen, water, sand and clay, to compare the behaviour with results obtained from a real core sample (obtained from a BP asset). The low-frequency dielectric spectroscopic analysis (10-2 to 107 Hz) yields complex properties (e.g. conductivity, permittivity, impedance) with frequency dependent in-phase and quadrature components. Within this frequency range, dielectric spectra are dominated by EDL and M-W polarization effects. By varying the sample preparation methods, it has been possible to observe structural differences with respect to water.