| Abstract |
Radiogenic heat production (RHP) is a key parameter in assessing the thermal regime of subsurface formations, influencing hydrocarbon maturation, reservoir quality, and geothermal energy potential. Radiogenic heat primarily originates from the radioactive decay of naturally occurring isotopes of uranium (U), thorium (Th), and potassium (K), which significantly contribute to subsurface temperature distribution. However, in hot sedimentary aquifer geothermal systems, heat is typically assumed to be generated in the underlying granitic basement, and the overlying sediments simply act as thermal blankets rather than heat sources. This study calculates RHP of sediments using geophysical well log data from the Horn River Basin in northeast British Columbia, Canada. This basin presents an ideal case study due to its extensive shale gas development and comprehensive subsurface data - particularly spectral gamma ray logs, including total gamma ray and individual U, Th, and K concentrations. The basin is also subject of emerging geothermal interest given abnormally high thermal gradients (46.4°C/km average). We focus here on the radiogenic Horn River Group (HRG) shale at the base of the sedimentary basin. By integrating well logs with bottomhole temperatures, we generated thermal gradient profiles and mapped RHP distributions across the basin. Results reveal spatial variation in RHP among three formations within the HRG: The Evie Formation has the highest average RHP (4.3 µW/m³), the Otter Park Formation the lowest (2.3 µW/m³), and the Muskwa Formation intermediate (3.6 µW/m³). These findings suggest that the HRG heat production could partially account for the anomalously high geothermal gradients observed. |