Hydrogeological potentiality assessment of Teboursouk Basin, Northwest Tunisia using electrical resistivity sounding and well logging data

Abstract

The water table of Teboursouk basin (NW Tunisia), logged in the Eocene limestone, is a relevant hydrological target considering its relatively important volume and good chemical quality. The assessment of its geohydrological potential requires the compilation of geological, stratigraphic, geophysical studies and drilling data. Well logging aims characterization of the petrophysical parameters of aquifer formations as well as possible correlations between boreholes. The interpretations show high variabilities in porosity (from 4 to 42 % related to fracturing) of limestone formation and in salinity (0.7 to 2.3 g/l) of the water table; the latter increase to the Southeast of the basin, which is contaminated by the salt formation. Over 54 Schlumberger electrical soundings (AB = 400 m) were performed. The interpretation of resistivity distributions at various depths is based on apparent resistivity maps corresponding to different AB spacings. Measured resistivity values were one-dimensionally interpreted. Drilled boreholes and the position of some electrical soundings on geological outcrops have been helpful for electrical data calibration. The generalization of the calibration for all electrical soundings show that the limestones are characterized by high and very contrast resistivity (ρ >22 Ωm), a depth ranging from 0 to 100 m and a thickness of about 70 m, exceeding 200 m per place. These variations are due to the presence of faults which are affecting the basin, and are connected to Eocene lands behind. The compilation of data led to evaluate approximately the groundwater reserves of Teboursouk basin to 130 million of cubic meter.