Some Aspects of the Thermal Regime, Hydrodynamics, and Petroleum Occurrences in Central Tunisia.

BEN DHIA, H., and H. KOUAS, Ecole Nationale d'Ingenieurs de Sfax, Tunisia

Recent literature has emphasized the possible relation between positive thermal anomalies, deep water movement, and hydrocarbon occurrences. In Tunisia, parallels have been shown between some hydrocarbon accumulations and the geothermal gradient in the Central part of the country. Other studies showed the relation between some deep aquifers hydrodynamics (Aptian, Ypresian, etc.) and the corresponding oil fields. For Central Tunisia, 8 of the 10 main existing hydrocarbon occurrences are located within a region of positive geothermal gradient anomaly ranging from 35 to 45 degrees C/km. On the other hand, the relatively old oil fields (Triassic) show a low geothermal gradient values (<30 degrees C/km), whereas the recent ones (upper Tertiary) seem to have high geothermal gradient valu s(>50 degrees C/km).

The study of the deep reservoirs in central Tunisia revealed that oil accumulations of the Aptian (Douleb field), Ypresian (Lytaiem field), etc. are located within zones of hydrodynamic convergence and discharge areas. Hydrogeologic studies of other reservoirs (Abiodh and Serj formations) revealed new interesting areas of deep waters convergence, favorable to oil accumulations and not yet assessed. Moving water within deep reservoirs seems to be the main vehicle of temperature and oil. Even if the primary reason of this parallel between oil, temperature, and hydrodynamics, is not yet clearly established, empirical evidence and numerous examples throughout the world make it worthwhile to consider geothermal and hydrologic exploration as integral part of any petroleum exploration progra .

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)