Integrated study of surface and subsurface data for prospecting hydrogeothermal basins of hot water spring Ain El Hammam: case of Utique region basin (extreme north of Tunisia)

摘要

The Utique region is located in the extreme north part of Tunisia. It is represented by the main and over exploited shallow Plio-Quaternary aquifers of Ghornata-Aousdja-Ghar el Meleh. These aquifers are captured by a good number of wells which are characterized by a cold water. Within the study region, in the Utique ruin rise the hydrothermal spring of the Ain El Hammam. It is marked by a hot temperature (36.2 A degrees C) and low salinity 1.7 g L-1. A synthetic study integrating geological, geophysical, hydrogeological, hydrogeochemical, and geothermometry data has been applied in order to determine the reservoir of Ain El Hammam and evaluate its hydrothermal potential. The interpretation of petroleum wells and seismic lines gave a clear picture of the structure and geometry of the different sedimentary series. The geochemical data show that the thermal water of Ain El Hammam has a Na-Cl type which is due to the following: first, the abundance of the evaporitic strata, particularly halite, gypsum, and anhydrite, and second, related to direct cation exchange between groundwater and the clay fraction. The use of saturation indices for different solid phases according to the temperature and geothermometers suggests that the reservoir temperature estimated of Ain El Hammam can reach up to approximately 82 A degrees C. Indeed, this temperature value can be attempted in a depth of almost 1800 m indicating that the reservoir of the hydrothermal spring of Ain El Hammam corresponds to the Late Triassic series. Probably, the water circulates from the Late Triassic reservoir to the surface following the fault of Utique F1 and traversing the anhydrite, gypsum, and clay of the Mio-Plio-Quaternary series.