HR: 14:40h
AN: H12H-05    [PDF]
TI: Electrical Spectroscopy of Permo-Triassic Sandstone From the United Kingdom
AU: * Scott, J
EM: j.b.t.scott@bham.ac.uk
AF: Earth Sciences, University of Birmingham, Birmingham, B15 2TT United Kingdom
AU: Barker, R
EM: r.d.barker@bham.ac.uk
AF: Earth Sciences, University of Birmingham, Birmingham, B15 2TT United Kingdom
AB: Electrical spectroscopy measurements in the range of mHz to kHz have been made on the dominantly red Permo-Triassic sandstone from the United Kingdom. Samples have been selected from borehole cores from all of the main outcrop areas of sandstone and represent a wide variety of lithologies. This sandstone is an important aquifer for several major cities including Manchester and Birmingham. The samples have been fully saturated with sodium chloride brines and a synthetic groundwater solution that is higher in calcium and magnesium ions than sodium and which closely matches the cation concentrations of the groundwater at Birmingham. Electrical measurements were made using a four-electrode arrangement of silver-silver chloride electrodes. Most of the electrical spectra show a clear, slightly asymmetric, electrical relaxation phenomenon with relaxation peaks in the range of 0.001 Hz to 20 Hz. These relaxation phenomena can be fitted very well by a generalised Cole-Cole model. The relaxation time from this model is found to correlate closely with the dominant pore-throat size from mercury injection. Normalising the chargeability, Cole-Cole m parameter, by the conductivity gives a polarisation magnitude which correlates well with the pore surface to volume ratio (S$_{POR}$) for sandstone samples with an even distribution of surface coating clays. The information obtained from the electrical spectra is very useful. The pore-throat size is important in controlling the permeability and in particular the flow of non-aqueous phase fluids. The pore surface area has links to the sorbtion properties of the rock, which are important in estimating contaminant transport. The electrical spectra also provide a useful fingerprint of individual lithologies which could be used for correlation between boreholes or outcrops.
DE: 0925 Magnetic and electrical methods
DE: 1800 HYDROLOGY
SC: Hydrology [H]
MN: 2003 Fall Meeting