QL40-GR Probe Image


The QL40-GR probe measures the amount of gamma radiation occurring naturally within the formations crossed by a borehole. Gamma rays are produced mainly by isotopes of potassium, thorium, and uranium. The gamma log is widely used in the groundwater and mining industries to identify lithology and perform clay content analyses.

The tool is supplied as a stackable sub of the Quick Link (QL) product line or it can be run as a standalone tool. The QL40-GR operates on any standard wireline (mono, 4 or 7 conductor, coaxial).


  • Bed boundary analysis
  • Facies changes
  • Coarsening/ Fining Sequences
  • Identify Clay Aquitards
  • Aquifer Thickness
  • Uranium Concentration

Operating Conditions

Borehole Fluid
[X] Water
[X] Mud
[X] Dry

[X] Uncased
[X] PVC Borehole
[X] Steel

[_] Required
[X] Not Necessary

Features & Benefits

  • Versatile, ubiquitous probe which functions with a wide range of applications and borehole conditions.
  • Matrix .sub files can be modified to output gamma in API units or %wt U3O8 (percent weight Uranium).
  • Mount Sopris manufactures more natural gamma and spectral tools than any other slimline manufacturer in the world today.
  • Gamma probes with other scintillation materials and sizes can be custom made for your application.

Gamma Probe Angled

Specifications – Metric/English

Specification Metric Imperial
Diameter 42.3 mm 1.66″
Length 1.03 m 40.5″
Weight 4.67 Kg 10.3 lbs.
Max. Temp. 70ºC 158ºF
Max. Pressure 200 bar 2900 psi

Sensor: NaI(Tl) Crystal 2.22 cm x 7.62 cm (0.875” x 3.0”)

QL Stack Possibilities

  • QL40GR (Gamma) + QL40ELOG (Resistivity) + QL40MGS (Magnetic Susceptibility): Mining, Exploration
  • QL40GR (Gamma) + QL40ELOG (Resistivity) + QL40OBI (Optical Televiewer): Exploration, Bedding Planes, and Fractures in Dry holes
  • QL40GR (Gamma) + QL40ELOG (Resistivity) + QL40ABI (Acoustic Televiewer): Exploration, Bedding Planes, and Fractures in Fluid-filled holes
  • QL40GR (Gamma) + QL40ELOG (Resistivity) + QL40FTC (Fluid Res, Temp): Hydrogeologist’s Tool, Groundwater exploration and assessment
  • QL40GR (Gamma) + QL40DEV (Deviation): Lithology, Borehole location


QL40-GR Natural Gamma Probe Brochure
User Guide

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