APPLICATION OF SPECTRAL INDUCED POLARIZATION TECHNIQUE TO DELINEATE SOME HYDROGEOLOGICAL CHARACTERISTICS OF SATURATED AND UNSATURATED SANDSTONES

Abstract

The last decade witnesses a growing interest in the application of the Spectral Induced Polarization (SIP) method in hydrogeological and environmental investigations. This is may be inspired by the fact that both groundwater and electrical current move (and affected by) via interconnected paths through rock matrix. Besides, more sophisticated models by incorporating charge storage (complex resistivity) with petrophysical characteristics of porous matrix were produced, result in even more appropriate relationships between the electrical spectra and some hydrogeological parameters. However, the majority of the previous work was focusing on a specific sandstone aquifer, or on a specific soils or soil mixtures, causing non-comparable different calculations of the parameters characterizing observed electrical spectra. Aiming to approach a better understanding of the polarisation processes occurring in sandstone, and establish the potential value of SIP for characterising the physical and hydraulic properties of saturated and unsaturated sandstones, the laboratory electrical spectra response of samples from ten different types of sandstone have been examined against several measured physical and petrophysical parameters of sandstones included in order to assess the universality of any correlations between the spectral IP response and hydrological characteristics that are important in any hydrogeological and environmental investigations. In order to be able to define the relationship(s), if any, between SIP response and the physical and chemical characteristics of sandstones, a range of other non-electrical characteristics is necessary in order to make comparisons or correlations with the electrical spectra response of the sandstones and their internal structure. On the other hand, an intensive laboratory programme measurements was applied to measure the SIP response of the different types of sandstone over the range of mHz to kHz involved in the current study. For fairly porous sandstone types, a clear peak is noticed on both the phase and quadrature spectra that can be attributed to the existence of an effective length scale