Sidewall Density - Probe

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.


  • 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


  • Bulk density
  • High-resolution density (HRD)
  • Natural gamma
  • Caliper
  • Options: Guard resistivity, Bed-resolution density (BRD), Temperature


  • 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


  • 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

Sidewall Density and Sidewall Density

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