Detecting calcium and magnesium in borehole - by neutron irradiation and measuring gamma radiation resulting from decaying calcium and magnesium isotopes

摘要

Method for studying the lithology of subterranean formations tranversed by probe esp. during well logging, comprises (a) irradiating a formation with neutron of sufficient energy to produce the activation reactions 26Mg(n,gamma) 27Mg and 48Ca (n,gamma)49Ca; (b) measuring the levels of activity of the gamma rays resulting from the decay of the 27Mg and the 49Ca and (c) combining the measurements to provide an inducation of the lithology, i.e. to obtain the ratio Ca/Mg allowing observer to distinguish dolomites and limestones from other formations. The readings are not affected by the presence of sandstone.