Natural Gamma

Gamma ray logging is used to measure naturally occurring Gamma radiation for characterization of rock or sediment inside the borehole. It is used in mineral exploration and water-well drilling but commonly used for formation evaluation in the borehole. It is based on principle that different types of rock emit different amount and spectra of natural gamma radiation. For example shales usually emit more gamma radiation than other sedimentary rocks, such as sandstone, gypsum, coal or dolomite because of radioactive potassium which is a common component in their clay content and also because of the cation exchange capacity of clay cause them to absorb uranium & thorium.