Natural gamma ray spectrum analysis and filtering technique

摘要

In accordance with an illustrative embodiment of the present invention, a method and apparatus is disclosed for determining the content of a selected number of materials in an earth formation penetrated by a borehole from the spectrum of gamma radiation emitted by the materials in the formation. By deriving representations of portions of the detected gamma radiation spectrum and combining the representations, the content of the selected materials is determined. A special filter arrangement provides for an improvement in such a determination by effecting a reduction of an anti-correlation relationship between the determined contents of materials having closely related spectra. This reduction is achieved without sacrificing the resolution of the measurements along the borehole.