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The borehole-geometry probe consists of a four-arm caliper combined with a verticality measurement. The probe can replace the standard three-arm caliper with advantage where the borehole cross-section departs from circular and where directional information is required for well-completion studies and formation stress analysis.

Principle of Measurement:

The XY caliper provides continuous measurements of borehole diameter from two independent pairs of linked arms. The verticality section includes a triaxial magnetometer and three accelerometers. Data from these are combined by a downhole microprocessor to provide real-time, continuous logs of probe orientation and borehole inclination and direction.


  • Sensitive X-Y caliper
  • Continuous orientation log for all borehole inclinations


  • X and Y calipers
  • Borehole deviation and drift
  • Borehole volume
  • True vertical depth (TVD)
  • Natural gamma


  • Water/minerals/engineering
  • Borehole diameter in two axes
  • Borehole break-out for stress analysis
  • Cracks, fissures and casing defects


Diameter 60mm
Length 3.5m (in two sections)
Weight 40kg
Temperature 0-70⁰C (extended ranges available)
Max. pressure 20MPa
Caliper range 75mm to 700mm

Operating Conditions

  • Borehole type: open/cased, water/air-filled
  • Centralisation: recommended, non-magnetic centralisers required

Sales Information

I002044 Borehole geometry probe with natural gamma

Download Borehole-geometry sheet


...Practical Innovation with Global Service & Support...

Robertson Geologging Ltd., 2017

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