RIM/BHR
Radio Imaging / Borehole Radar
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.
Crew
2 borehole operators plus a driller or hoist crew on standby
Mobilisation
2-3 days: hole condition survey, winch rigging, probe calibration
Daily coverage
1-2 hole pairs per day (roughly 0.4-0.8 km of tomographic coverage)
Equipment and specifications
| Probes | Matched transmitter / receiver dipole probes, 50 kHz - 30 MHz, slim-hole rated |
|---|---|
| Winches | Two depth-encoded winches, 0.05 m depth accuracy, synchronised control |
| Cable | Fibre or coax logging cable rated to hole depth with strain relief |
| Calibration jig | Above-ground fixed-separation frame for amplitude calibration |
| Hole condition kit | Caliper and deviation survey data for both holes |
Setup sequence
- 01
Verify the holes
Deviation and caliper surveys first — true probe separation drives the whole tomogram.
- 02
Calibrate
Record fixed-separation amplitudes above ground at every frequency to be used.
- 03
Plan the scan
Fan or level-by-level geometry with ray coverage crossing the target volume.
- 04
Run the scans
Lower both probes on synchronised encoders, recording amplitude at each station pair.
- 05
Invert
Attenuation tomography using true 3D geometry from the deviation surveys.
Safety
Stuck or lost probe
Overshot fishing kit on site, tension limits set on the winch, no forcing through obstructions.
Open hole and collar
Collar covers, edge protection, hard barricades around the pad.
Winch and cable under tension
Exclusion zone, no hands on moving cable, gloves and eye protection.
Underground work (if applicable)
Mine permit, gas testing, self-rescuer, tag-in / tag-out.
Field vs lab
| Aspect | In the simulator | In the field |
|---|---|---|
| Signal-to-noise | Clean synthetic response; noise added only if you ask for it. | Cultural noise, wind and instrument drift set the usable dynamic range. |
| Hole geometry | Two perfectly parallel, straight holes. | Real holes deviate metres; unsurveyed deviation shows up as false attenuation. |
| Hole fluid and casing | Not modelled. | Conductive fluid or any steel casing can kill the signal completely. |
| Coupling | Fixed antenna coupling. | Varies with hole diameter, fluid and wall roughness at every station. |
| Repeatability | Identical parameters return an identical curve every time. | Coupling, moisture and temperature move the response between repeats. |
Field QC checklist
- · Deviation survey available for both holes before acquisition
- · Calibration amplitudes repeatable within 1 dB start and end of shift
- · Reciprocal ray amplitudes agreeing within 2 dB