Natural Gamma Ray Borehole Logging Technique for Estimating Radiogenic Heat Production in Basaltic Environment, Case study from Kodana region, Southern Syria

Abstract

Two nuclear techniques are used to evaluate the radioactive heat production (HP) in a basaltic environ- ment in the Kodana region, Southern Syria: natural gamma ray borehole logging (Ra) and spectrometry gamma ray. The Ra measurements are converted into (HP) values based on the Bucker and Rybach relationship. The underestimated HP values obtained in this case study of Kodana well require therefore a modification of the Bucker and Rybach relationship constants (0.0158 and 0.8). A new equation is thereafter established and proposed as follows: HP (μW/m3) = 0.037* Ra (API) + 4.35. This equation is more suited to characterize HP in continental basaltic environments. The proposed equation is validated and has proven its efficacy through estimating and analyzing the HP in three additional boreholes in the study region. The analysis of 377 measured points along the Kodana borehole shows that Ra varies between 4.93API and 9.31API, with an average value of 6.83API, while the corrected and calibrated HP varies between 0.32 and 0.51 μW/m3 , with an average value of 0.42 μW/m3 . Four calibrated HP ranges were isolated in the study region using the multi-fractal concentration number and log-log graphs. The first range (<0.354 μW/m3 ) is related to hard massive basalt, the second (0.354 - 0.41 μW/m3 ) is related to hard basalt, the third (0.41 - 0.44 μW/m3 ) is related to pyroclastic basalt, and the fourth (> 0.44 μW/m3 ) is related to basalt alteration products and clay.