DELINEATION OF WATER INFLOW IN AN UNDERGROUND POTASH MINE WITH 3-D ELECTRICAL RESISTIVITY IMAGING

Delineating water inflow in underground potash mining environments has routinely been done using conventional mining methods, seismic techniques and recently GPR as a useful non-invasive tool. The combination of highly resistive dry salt and highly conductive wet salt makes these water inflow areas a good candidate for Electrical Resistivity Imaging (ERI). Mosaic Potash, Golder Associates Ltd., and the University of British Columbia’s Geophysical Inversion Facility (UBC-GIF) have worked to develop and apply ERI techniques for the underground environment. Because of the 3-D distribution of current and potential electrodes and the 3-D nature of the targets, full 3-D forward modeling and inversion of the data are required. The nature of underground mining limits the placement of electrodes to existing underground drifts and this severely restricts the available electrode geometry. By placing additional electrodes in boreholes, a survey geometry with enough information to constrain the 3-D inversion can be deployed. We present a case study of the delineation of a water inflow in a potash mine using 3-D ERI. The resulting inversion models of electrical conductivity have helped to focus drilling and mitigation efforts and have provided the geotechnical engineers and mine personnel with valuable information about the underground water distribution.