Electrical Resistivity: An Overview Of Tools & Techniques

To save time and money and reduce risk, you need to see what’s below the surface before you drill, dig, or develop. Electrical resistivity imaging not only makes that possible—it makes it efficient and cost-effective.

What is electrical resistivity?

Electrical resistivity, also known simply as resistivity, is a bulk electric property of all material that shows how strongly it opposes the flow of electric current. A low resistivity indicates a material that readily allows the flow of electric current (or is conductive).

All materials have a certain resistivity and fall within a broad range. The SI unit for resistivity is the ohmmeter (Ωm).

Why does resistivity matter?

We’re glad you asked! For scientists and geophysicists who love this stuff, electrical resistivity is the tool that allows us to do electric resistivity imaging: the scanning and imaging of the subsurface of the Earth—whether on land or in water. Electrical resistivity meters like ours allow the user to visualize the results of the scans in 2D slices and 3D volumes in terms of resistivity.

So why should electrical resistivity imaging matter to you?

Benefits Of Electrical Resistivity Imaging

If you’re involved with building, drilling, digging, developing, repairing, or mapping anything on the surface, underground, or underwater, the electrical resistivity method of imaging can help you do your job safer, faster, and more efficiently. Here’s a sample of ways our tools have helped clients across the globe with their projects.

Use Cases

• Groundwater exploration.

• Subsurface site characterization (2D and 3D imaging, tomography and ERT).

• Cave, void, and sinkhole location.

• Depth-to-bedrock determination.

• Landslide hazard mapping.

• Marine 2D and 3D surveys for dredging, harbour work, underwater cable laying etc.

• Lithology mapping.

• Mineral exploration.

• Archaeological site investigation.

• Mapping permafrost.

• Mapping underground pollution plumes, such as brine spills.

• Detection of free products of nonaqueous phase liquids (NAPLs).

• Monitoring remediation processes such as ammonia injection, desiccation, vitrification, steam injection, pumping, and air-sparging.

• Monitoring subsurface processes such as pump tests, CO2 injection, groundwater recharge, infiltration, saltwater intrusion, tunneling, dam leakage, and mining operations.

Tools & Techniques For Your Resistivity Surveys

The tools you need will depend on what and where you’re surveying as well as the size of the area you’re surveying. Here are two case histories that can give you an idea of what tools you may need for your project:

Groundwater Exploration

• Locating water wells in South Sudan: By surveying with our multichannel surface resistivity meter system, the SuperSting, and then processing that data with EarthImager, our clients could select a drilling location for a very high-production, potable water well with a 4,000-liter-per-hour static yield in the South Sudan region.

Geophysical Exploration

• Scanning for leaks in the Amistad Dam: Engineers observed holes opening in the bottom of the Amistad Dam that were emptying the dam. Our field demonstration used an earlier instrument similar to our SuperSting to find the leaks based on the survey. With the data from our instruments, our client was able drill into the anomalous areas, which were then drilled and grouted.

Our supported measurement arrays mean you can use the resistivity measurement techniques that best suit your use case:

• Dipole-Dipole (8-Channel)

• Bipole-Bipole (8-Channel)

• Pole-Bipole (8-Channel)

• Pole-Pole (8-Channel)

• Gradient (8-Channel)

• StrongGradient™ (8-Channel)

• EdgeGradient™ (8-Channel)

• Radial Dipole-Dipole

• Inverse Schlumberger (4-Channel)

• Mixed Arrays

  • Dipole-Dipole-Gradient

  • Wenner-Schlumberger

• Schlumberger (Single-Channel Only)

• Wenner (Single-Channel Only)

• User-Programmable Arrays Of Any Kind