APC OFS’s GRST tool measures discrete levels of Gamma Ray energy coming from naturally occurring radioactive elements present in formations, including Potassium (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 occurring Gamma ray Spectrum, ranging from 0 to 3,000 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.