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Sub-dept. of Geophysics, University of Birmingham, P.O. Box 363, Birmingham, B15 2TT.
Borehole resistivity methods have been used to study the Bunter Sandstone aquifer of north-west Lancashire. The results of water-resistivity and ‘normal’ logging surveys are discussed. Using the determined distribution of ground-water resistivity an average formation factor is calculated for each well. This quantity is shown to be affected by conduction of the sandstone matrix, a phenomenon which is used to estimate hydraulic conductivity at borehole sites as follows. Within a limited section of the aquifer, values of hydraulic conductivity calculated from pump-test data are correlated with formation factors corrected for several assumed levels of matrix conduction. The most significant correlation furnishes an empirical relationship which permits the interpolation of hydraulic conductivity in terms of the resistivity data. Estimated values of hydraulic conductivity at the sites of unlogged wells are generally at least as accurate as those obtained directly from interpolated hydrological parameters. The possible extension of the method to predict potential well yields is briefly indicated.
