Subsurface Imaging

A more recent development with Electrical Resistivity Imaging is the capability to do cross-hole surveys. This are run using a standard surface system but with the addition of specialist downhole cables.

The usual depth limits are between 150 to 300m for most applications. In certain cases with specific electrode setups, greater depths are possible.

The surveys can be run Borehole to Borehole and surface to Borehole. Surface array data can be combined with cross-hole data to improve the image result.

Comparison between the results from surface resistivity and crosshole resistivity tomography.

Crosshole data Lateritic Iron Ore survey

Clearly the tomography shows a greater level of detail. However, it would take several crosshole panels to covers the same area as a full surface resistivity image.