QL40-GR-CCL Gamma Casing Collar Locator Probe Image


The QL40-GR-CCL is a combination of a natural gamma ray (GR) assembly and casing collar locator (CCL). The natural gamma ray (GR) module measures the amount of gamma radiations occurring naturally within the formations crossed by a borehole.  A scintillation Sodium Iodide crystal is used to detect the gamma rays.  Gamma rays are produced mainly by isotopes of potassium, thorium, uranium and their decay products. The gamma ray log is widely used in the mining and groundwater industry for the identification of lithology, correlation between boreholes and clay content analyses.

The casing collar locator (CCL) is a magnetic device sensitive to changes of metal thickness at casing or tubing collar. It is always run in steel cased boreholes to detect the position of casing collars. It is mainly used for depth control and depth correlation.

The QL40-GR-CCL is supplied as a stackable sub of the Quick Link (QL) product line or it can be run as a standalone tool.


  • Bed boundary analysis
  • Casing Collar Locator
  • 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] Non-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).
  • CCL magnets cause large magnetic flux at casing joints.

Specifications – Metric/English

Specification Metric Imperial
Diameter 40 mm 1.6″
Length 1.16 m 46″
Weight 6 Kg 13 lbs.
Max. Temp. 70ºC 158ºF
Max. Pressure 200 bar 2900 psi


Gamma Sensor: NaI(Tl) Crystal 2.22 cm x 7.62 cm (0.875 x 3.0 in.)
CCL Sensor: 32 x 280 mm Coil & Magnets Assembly

Measurement Principles

The natural gamma ray (GR) module is equipped with a scintillation Thallium doped Sodium Iodide crystal – NaI(Tl), a material which when struck by gamma rays emits pulses of light. These pulses of light are amplified by a photomultiplier tube and are then converted into electrical pulses. The number of pulses are counted during a sampled time interval at the investigation depth, the result is then digitized and transmitted up the wireline to the surface acquisition system.

The casing collar locator (CCL) consists of a coil mounted between two permanent magnets. As the tool passes a change in metal thickness, such as a collar, the magnetic flux between the permanent magnets becomes distorted. The distortion of the magnetic field induces a low frequency voltage in the coil. This induced voltage is amplified and after digital conversion recorded in conjunction with the gamma ray.

QL Stack Possibilities


QL40-GR-CCL Gamma Casing Collar Locator Probe Brochure

User Guide

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