Nuclear activation method and apparatus for detecting and quantifying

Abstract

A nuclear apparatus for obtaining qualitative and quantitative information related to an element of earth formation surrounding a borehole, comprising: (1) a neutron source for irradiating the formation with neutrons of sufficient energy to activate atoms of at least a given element; (2) at least two (preferably four) detectors longitudinally spaced from said source, for detecting the gamma rays emitted during the activation reaction; (3) means for assigning a maximum number of counts for each detector and for establishing a relationship between these maximum number of counts and the corresponding instant of time counts for each detector; and (4) means for deriving from the relationship qualitative information related to the element. The relationship is approximately a straight line, the slope of which is representative of the element of interest. The amplitude of the counts is representative of the quantity of the activated element and of the radial distance between the activated atoms and the borehole.