HGI offers drilling support, borehole logging, and well design to help understand internal heap conditions and draw down excess metal inventory.
In-situ characterization of heaps and dumps is important to obtain quantitative data concerning metal inventory, moisture conditions, and compaction. HGI provides onsite drilling support and borehole logging, as well as ensuring the proper completion of drainage or injection wells. We are experienced in a variety of drilling methods and can help develop a hydraulic understanding or inventory analysis from assays. When combined with our geophysical characterization technology <<link to geophysical characterization page>>, a powerful mapping tool can be provided to ensure the right interpretation is available for important decision making.
HGI offers a wide variety of drilling support and borehole logging methods applicable to heaps and dumps, and can provide methodologies for developing an in-situ understanding of hydraulic processes or inventory analysis from assay data.
Borehole logging of physical parameters of formation material, as well as direct sampling, provides snapshots into the subsurface conditions of heaps and dumps, including heap structure, permeability, and material oxidation state – all of which are important components of well field design for heap characterization <<link to heap characterization page>> and enhanced metal recovery <<link to enhanced recovery page>>. Providing these components to our clients in both report and graphic formats benefits their planning, and enhances efficiency in their processes.
As an example, electrical resistivity was collected across a leach pad to help pinpoint areas within the heap that were causing ponding. A link to the full paper can be found here <<link to second Carlota paper>>. The figure below shows the results of the survey as color contours, with the depth of investigation extending to the HDPE liner. Low values of resistivity are usually associated with moist material, porewater of high ionic strength, or clayey ore. The profile shows a wide range of resistivity, spanning nearly four orders of magnitude.
The figure also shows results from HGI’s drilling support and borehole logging, taken from locations that were in close proximity to the resistivity profile. LPD-22 and LPD-23 were drilled after the resistivity data were acquired and additional ore was stacked. The moisture data is uniform along the profiles, similar to the electrical resistivity data at that location. Total copper metal inventory from assaying extracted samples is more variable, but the trends between the drill holes are the same. Furthermore, there is an indirect correlation between the trends of moisture and trends in total copper. That is, when moisture increases the copper decreases, which suggests that if the ore is sufficiently wetted then copper leaching will occur.
The second pair of drilling data occurred in the area of the resistivity profile that was more heterogeneous in nature. LPD-37 shows the same indirect correlation between moisture and metal inventory, and a very wet zone at a depth of 1177m is almost depleted of copper. Curiously, the trends in total copper from LPD-37 and LPD-38 are opposite but moisture trends are similar.
HGI provides a comprehensive view of heaps and dumps. Our data can be used to solve a variety of problems associated with drainage, compaction, pooling, and stability.