Sidewall Density and Sidewall Density/Guard Probe
The sidewall density gamma probe uses dual shielded detectors to provide a boreholecompensated density measurement with good bed-boundary resolution. The sidewall-density/guard probe offers an additional LL3 focussed electrical measurement with good vertical resolution and depth of investigation.
Principle of Measurement: The probes contain a detachable 137Cs gamma source and two scintillation gamma detectors. The active windows of the source and detectors are maintained in contact with the borehole wall by a motorised caliper arm. Gamma radiation back-scattered by the formation (Compton effect) reaches the detectors where the relative count rates provide a measure of formation density.
Features
- Compensated density output in engineering units (g/cc)
- Short-spacing detector for high vertical resolution
- Tungsten shielding reduces borehole effects
- Standard calibration blocks for field or base use
Measurements
- Bulk density
- High-resolution density (HRD)
- Natural gamma
- Caliper
- Options: Guard resistivity, Bed-resolution density (BRD), Temperature
Applications
- Minerals:
- Density and porosity
- Lithology
- Bed thickness and boundary location
- Coal ash and moisture content
- Engineering:
- Rock strength and elasticity parameters (with sonic log)
- Detection of weathered or fractured zones
- Water:
- Location of aquifer and aquitard
- Detection of cavities and missing cement
Operating Conditions
- Borehole type: open-hole, water-filled
Specifications
- Diameter: 50mm
- Weight: 20kg
- Temperature: 0-70⁰C (extended ranges available)
- Max. pressure: 20MPa
- Density range : 1.1 to 2.95g/cc
- Caliper range: 50mm to 300mm
- Resistivity range: 1 – 2,000 ohm-m
