Gamma Ray Spectral Tool (GRST)

Gowell’s GRST tool measures Gamma Ray energy and discretization coming from naturally occurring radioactive elements present in formations, including Potasium (K), Thorium (Th) and Uranium (U), to provide clay type and volume analysis.

The tool contains a large scintillation crystal which provides higher detection efficiency and sensitivity. GRST measures the naturally occuring Gamma ray Spectrum, ranging from 0 to 3000 Kev. The result is a detailed spectrum of 256 discrete data channels. Spectral tools are extremely important as they provide a clear picture of the sedimentary environment present in the formation such as materials source, diagenesis, groundwater activity, clay type and clay content.





  • Quantitative measurement of actual radiation and separation into its three predominant components: Potassium, Uranium and Thorium.
  • Enhanced reservoir volumetric description and delineation
  • Determines cation exchage capacity and clay types
  • Determines clay and shale volumes
  • Provides differentiation between radioactive pay zones and shales
  • Gives crucial input for complex lithology analysis
  • Detailed well-to-well correlation
  • Igneous rock recognition



  • Clay typing
  • Built in spectrum stabilization
  • Detailed 256 Channel spectrum
  • Heavy mineral identification
  • Can be run in combination with all Gallop tools
  • Differentiation between radioactive pay zones and shales
  • Identifies fractured and highly permeable zones where high uranium concentrations are present
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