Frequency domain
RIM/BHR — Radio Imaging / Borehole Radar
Hole-to-hole radio tomography of the rock in between
Frequency band
50 kHz - 30 MHz
Depth range
10 - 300 m between holes
Resolution
High between holes
Source
Downhole radio transmitter
Typical cost
Moderate - needs boreholes
Survey speed
Moderate - one hole pair at a time
Best terrain
Resistive host rock; existing boreholes required
Domain
Frequency domain
Overview
A transmitter is lowered down one hole and a receiver down another. Measuring signal attenuation over many transmitter-receiver pairs allows a tomographic image of the rock volume between the holes to be reconstructed.
How the physics works
Attenuation depends on conductivity and frequency through the loss tangent. Conductive features - sulphides, water-filled fractures, shear zones - cast a measurable radio shadow, and the geometry of many crossing raypaths converts those shadows into an image.
Where it is used
- Coal seam continuity and washout detection
- Mapping massive sulphide lenses between drillholes
- Fracture and karst detection for engineering
- Ore-body delineation ahead of mining