Enhanced heat flow assessment in Gulf of Hammamet and Pelagian Sea: Temperature corrections and conductivity adjustments

Abstract

This study proposes new corrections of formation temperatures combined to correction of formation conductivities to reconstruct the heat flow map of the Gulf of Hammamet-Pelagian Sea, Eastern Tunisia. For that, a new linear Cross-Plot temperature correction approach, based on Bottom Hole Temperatures (BHT) and Drill Stem Temperatures (DST) of 63 drilled boreholes, was applied. In addition, and as temperature is transmitted from the substratum to the top of a stratigraphic column owing to the thermal conductivity, the latter was investigated according to a high appraisal of ±5 m and taking into account porosity variation with depth. The produced corrected thermal conductivity and geothermal gradient allowed to calculate the corrected heat flow in the Gulf of Hammamet – Pelagian Sea. Results show that the corrected geothermal gradient varies between 23 °C/Km and 58 °C/Km with a regional mean of about 39 °C/Km. The corrected heat flow rises from 49.5 to 119 mW/m2 with a regional mean of about 68 mW/m2. Variation of heat flow is dependent of the geodynamic evolution of the area where high heat flows follow folding structures and relatively low heat flows follow major trending faults. The major variations are E-W, N-S and NW-SE in direction following the major structural trends.