HR: 13:55h
AN: NS13A-02    [Abstracts]
TI: Spectral Induced Polarization of Sandstones: Temperature Effects
AU: * Binley, A
EM: a.binley@lancaster.ac.uk
AF: Lancaster University, Department of Environmental Science, Lancaster, LA1 4YQ, United Kingdom
AU: Kruschwitz, S
EM: s.kruschwitz@gmx
AF: Federal Institute for Materials Research and Testing, FG VIII.2, Unter den Eichen 87., Berlin, 12205, Germany
AU: Lesmes, D
EM: david.lesmes@science.doe.gov
AF: US Department of Energy, Office of Biological and Environmental Research, 1000 Independence Ave., Washington, DC 20585, United States
AB: There is growing interest in the use of spectral induced polarization (SIP) for a wide range of environmental applications, in particular those focused on hydrogeological investigations. Recent experimental work has demonstrated that the mean relaxation time of electrical impedance spectra measured in sandstones is linked to the grain surface area and strongly correlated to some measure of a dominant pore throat size. Such empirically derived relationships lead to potential models of SIP - hydraulic conductivity, which has immense value for the hydrological community. Furthermore, the links between surface area and electrical response may lead to other, equally exciting, applications, such as in characterizing geochemical reactivity of sediments. However, there is a need to understand the fundamental behavior of SIP in such porous media in order for such models to be applied usefully. In an attempt to address this, we focus here on the influence of temperature on the SIP behavior of a range of sandstones. Classical models of dielectric dispersion in colloids have proposed direct inverse relationships between relaxation time and temperature. Through a series of experimental trials we have studied this behavior: examining the impedance spectra (in the 1 mHz to 1 kHz range) of four different sandstones over a temperature range of 5 to 30 degrees Celsius. Analysis of the spectra with the widely used Pelton Cole-Cole model has confirmed hypothesized effects on a mean relaxation time but revealed that the responses to temperature change is a function of physical properties of the sandstone. In addition, the analysis has illustrated how temperature effects on surface complex conductivity of the sandstones differ as a function of pore fluid and formation factor. The results add to the growing experimental evidence of controls on spectral impedance in porous media and help ascertain generalized petrophysical models for a wide range of applications.
DE: 0925 Magnetic and electrical methods (5109)
DE: 1829 Groundwater hydrology
DE: 1835 Hydrogeophysics
DE: 1859 Rocks: physical properties
DE: 5134 Thermal properties
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting