Electrical Resistivity
HGI’s application of the electrical resistivity method is ideally suited for acquiring 2D, 3D, and 4D images to understand hydrogeological, geochemical, and geological variability of the subsurface. Geophysical resistivity services provide a rapid, non-intrusive view of the earth and can often be conducted in near real time, thus providing information that can be used to direct other essential services. Examples include leak detection, plume mapping, injection optimization, geotechnical stability, hydraulic characterization, and aquifer recharge.
Performing electrical resistivity surveys is a signature service of hydroGEOPHYSICS. We employ a variety of instruments to measure resistivity data, from commercial units to in-house manufactured systems.
Electrical resistivity surveys are a core service of HGI and we have honed the technique to solve a number of environmental and mining-based problems. We employ a wide variety of instruments to conduct electrical resistivity surveys, ranging from commercial units purchased from retailers to in-house manufactured systems (e.g., HGI’s GeotectionTM Resistivity Monitoring System) that are tailored to the most demanding projects. HGI also has a large cable inventory, which allows us to set up very long two-dimensional profiles (>5000ft) or large three-dimensional grids.
HGI regularly contributes to the science of geophysics and our range of electrical resistivity services have been adapted in a variety of ways, including the use of optimized array configurations, long electrode resistivity, and time lapse resistivity. These unusual applications have been published in peer reviewed journals and conferences around the world.
HGI regularly contributes to the science of electrical resistivity. Many of our applications have been published in peer reviewed journals and conferences around the world.
An example resistivity dataset is shown below, which was acquired as a two-dimensional profile across a deeply incised canyon. The basic geological description includes relatively young volcanic units layered nearly horizontally from multiple eruptions. Near the beginning of the line is a source of water and its effects can be seen to depths of 300ft or more. The section could also be interpreted for geological faults that break otherwise continuous contour lines (such as the canyon at 2200ft).
Electrical Resistivity Profile Example of Volcanic Material.
Our geophysical resistivity services include active monitoring by acquiring multiple snapshots over time on the same set of electrodes to observe changes in subsurface conditions. Each subsequent snapshot is compared to a baseline to more fully understand temporal effects from hydrogeological, thermal, or chemical changes. For the example shown in the below graphic, HGI monitored the changes in resistivity during an injection, whereby 1500 gallons per minute of solution was distributed among four wells, at depths of 70 to 100ft below ground surface. The result is a growing plume centered on the well’s footprint. These data were used to help optimize the injections for increased copper recovery.
Time lapse electrical resistivity