Integration of geological, hydrochemical and geophysical methods for prospecting thermal water resources: The case of the Hmeiema region (Central-Western Tunisia)

摘要

The Hmeiema region (Central-Western Tunisia) is characterized by numerous Aptian anticlines associated with Triassic outcrops. These Aptian reefal limestones, characterized by intense fracturing and important karstification, constitute a regional thermal aquifer. The aim of this multidisciplinary study is to evaluate the hydrothermal potential of this aquifer. Geophysical prospecting based on the electrical method allowed the lateral evolution and the structure at depth of the reefal limestones to be followed. Furthermore, the dataset obtained permitted a fair understanding of the structural geology of the region. Hydrochemical characterization of the sampled water, with temperature ranging between 29 and 39.3℃, shows that it is of Na-Cl type with enrichment in Ca and HCO_3. This water is undersaturated with respect to gypsum but oversaturated or close to equilibrium with respect to calcite. The synthetic approach integrating all data gave a clear picture of the water flow-path at depth. It is clear that the thermal ground-water in the region flows in the Aptian limestone and dissolves evaporitic Triassic deposits.