Neutron-Induced Gamma Ray Spectroscopy for Reservoir Analysis

Abstract

Abstract The weighted least-squares (WLS) approach to spectral analysis has enabled more information to be extracted from the downhole recorded induced gamma ray spectra than was previously possible. GST™ (gamma ray spectroscopy tool), with its optimized inelastic and capture spectral modes, permits analysis of most and often all significant elements present in the formation and provides the possibility of evaluating hydrocarbons, salinity, lithology, porosity, and shaliness. Data have been obtained in a wide range of conditions in open and cased holes with the GST tool both in its present and experimental versions. This paper presents field examples to demonstrate the versatility and potential of the technique, not only as an effective oil-finder independent of water salinity conditions but as a valuable input to a more complete interpretation of well logs.