Natural gamma-ray spectral logging - Some applications

Applications of the gamma-ray spectrometric method to the oil, gas and hard coal prospecting are presented. The use of a borehole spectrometer made it possible to determine in situ concentrations of the K, U and Th natural ra dioisotopes. The knowledge of K, U and Th concentrations gives an informati on which combined with other geophysical parameters such as: density, appar ent photoelectric absorption cross section, P-e, and neutron porosity, cons titutes a valuable tool for prospection of the investigated layers. The pre sented anomalies of uranium concentrations is of importance to determinatio n of shale concentration in the rocks. The method, when applied in a hard c oal deposit, made it possible to identify the coal seams and their thicknes ses. The determined U, Th and K concentrations were used to calculate the c alorific value, ash and carbon content in the coal.