Monitoring of a secondary recovery application of leachate injection into a heap

An electrical resistivity monitoring survey was conducted on a mine heap to track fluid movement during high pressure injections. The injections were part of Newmont's patent-pending process called Hydro-Jex, where high pressures and flow rates were used to add significant volumes of fluid within multiple depths or zones. For this experiment, injections occurred in two wells over a seven day period, with a total of about 3000 m3 of leachate added to each well. The resistivity data showed that the flow of leachate can be affected by low permeability zones. The cascading effect of leachate moving along the top of low permeability horizons and finally draining over the edge was directly observed in the resistivity data. Furthermore, it was observed in the resistivity that thin horizons of increasing saturation can travel at least 40 m from the injection well. Lastly, crude approximations to hydrological parameters may be obtained with the data, such as the change in water content, but calibration of the resistivity data with a few moisture sensors would be preferable and likely more reliable.