Total and spectral natural Gamma-ray logs of core samples

Total and spectral gamma natural radioactivity from potassium (40K), uranium (238U) and thorium (232Th) of core samples from a local well were determined in the laboratory. The measurements were carried out using a 127x127 mm (5x5) NaI (T1) detector and an electronic set up coupled to a PC-based data acquisition and analysis system. The data analyses of 240 samples for the depths 466 to 511m (1529 to 1677 ft) showed that the activities ranged from 0.3 to 67 API units. The results from laboratory measurements were compared with those of field well logging measurements. It was observed that the resolution of laboratory measurements was better than that of well logging and it was found that there was a depth shift of (1ft) between the data of the two types of measurements. The spectral gamma logs for potassium, uranium and thorium were also deduced from the spectrum analyses. (author)