Premium
Accurate Estimation of Conductivity of Water from Geoelectrical Measurements— A New Way to Correct for Clay
Author(s) -
Park Stephen K.,
Dickey Stephen K.
Publication year - 1989
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1989.tb01042.x
Subject(s) - conductivity , induced polarization , electrical resistivity and conductivity , geology , geophysics , porosity , mineralogy , calibration , soil science , polarization (electrochemistry) , geotechnical engineering , chemistry , physics , quantum mechanics
We propose a new way to correct estimates of solution conductivity for the effects of clay in a rock. The bulk electrical conductivity of a rock is dependent on its porosity, the conductivity of the pore fluid, and its clay content. Archie's law relates the bulk electrical conductivity to the first two factors only. The third factor, clay, enhances a rock's conductivity through surface conduction, and simple application of Archie's law will lead to overestimates of the solution conductivity. The enhancement due to clay can be estimated from measurements of induced polarization, however, and the bulk conductivity of the rock can be corrected. This correction will then lead to a more accurate estimate of the solution conductivity. Both resistivity and induced polarization can be measured by geophysical techniques. Interpretations of geophysical data are inherently nonunique, however, unless wells are correlated with the data. The method proposed here requires calibration with subsurface samples from at least one location. We have tested the method we propose to correct for clay in an area already sampled by monitoring wells. The corrections lead to substantial improvements in the correlation between solution conductivities from wells and from geophysical measurements. We are not proposing replacement of wells with geophysical soundings. Rather, the geophysical measurements, which are obtained at a fraction of the cost of a well, can be used to site wells and minimize the amount of drilling needed.