Detection of a Permeable Aquifer Geohazard Above Potash Mines using In-mine Time-domain Electromagnetics

ABSTRACT Inflows pose a serious concern to potash mining operations and often increase operating costs and production slow-downs. The mapping and understanding of water-bearing geohazards is vital in the potash mining industry. Critical to this effort is the development of geophysical tools to quantify the type and magnitude of these geohazards. In this paper, we propose using in-mine time-domain electromagnetics (TDEM) as a viable tool for investigating porous, water-bearing anomalies in geological layers more distant than has been done with electrical methods in the past. This work includes a TDEM survey to better delineate and quantify the properties of a suspected geohazard near a potash mine in southern Saskatchewan. Our investigations had two objectives: one was to confirm and define the extent of the conductive brine in the overlying lithology. The second was to determine the effectiveness of deploying TDEM in-mine where full-space effects and nearby machinery pose significant noise challenges to operation. Our results found a strong conductive EM signature to the suspected anomaly, suggesting there is high value in deploying TDEM underground. In addition, full-space EM computer modeling was performed in COMSOL Multiphysics using 2D-axisymmetric geometry to account for lithological changes both above and below our survey. We invert the survey data using a pair of different strategies. The results of which demonstrate that the anomalous EM response is caused by a conductive high in the Dawson Bay carbonate layers above the mine workings.