Gamma ray tools record naturally occurring gamma rays in the formations adjacent to the wellbore. This nuclear measurement indicates the radioactive content of the formations. Effective in any environment, gamma ray tools are the standard device used for the correlation of logs in cased and open holes.

Gamma ray tools use a super-sensitive, hermetically sealed Sodium Iodide Scintillator crystal and a ruggedized high temperature Photomultiplier with a signal conditioner and power controller in the qPACK™ mounting. It can be placed in any position in the tool string above the pulser, and run with one or tandem battery packs. The choice of power supply is dependent upon the predicted duration of the drilling run downhole. This module is also used in the Gamma-Steering package, with the incorporation of the Gamma-Steering directional module and the focused gamma sub.

gamma sensor


  • Depth determination
  • Depth correlation within and between wells
  • Lithology identification
  • Qualitative evaluation of shaliness
  • Qualitative evaluation of radioactive mineral


  • Distinguish shales from non-shales
  • Estimate clay content in sands and limestones
  • Correlation of real-time data with offset logs to determine geologic location
  • Picking casing and coring point
Diameter 1.36" w/o housing
1.875" w/ housing
(make up)
13.6" w/o housing
41" w/ housing
Weight 1.7 lb w/o housing
21 lb w/ housing
Operating Temp -60°C to 175°C
(-77°F to 350°F)
Material BeCu
Pressure 20,000 PSI
Sensitivity 2.0 Counts per API w/o housing
1.7 Counts per API w/ housing
Accuracy ±5% to 150°C (300°F)

±10% to 175°C (350°F)
Resolution 6.8"
Survival Temp 200°C (400°F)
Max Heat/Cool -15°C (5°F) / Minute
Vibration (3 axis)
50-300 Hz & Random
30 G
Shock (Z-axis) 500 G, 0.5 ms
Shock (Y-axis) 1,000 G, 0.5 ms
Input Voltage 22-30 V
Input Current 14-18 mA
Max Voltage 31.5 V
Pulse +5 V to 0 V, 2 (±0.5) µs