Incrustation ability of geothermal waters of the Continental Intercalaire aquifer in the Grand Erg Oriental basin (Algeria and South Tunisia)

The chemical composition of groundwater from wells tapping the Continental Intercalaire (CI) aquifer in the Grand Erg Oriental basin and the detailed analysis of saturation indices enable identification of the mineralization origin. CI groundwater is characterized by a Ca–SO₄/Cl abundant water type and a Na–Cl second type. Chemical pattern is controlled by evaporites dissolution (halite, anhydrite and gypsum). Recently, the decrease in these CI geothermal water wells performance is explained by an incrustation in the well screen. To study the scaling process, we used the degree of calcite saturation, hardness and Langelier Saturation Index (LSI). It has been demonstrated that scaling potential is the most important in the basin axis, around El Oued region (southern Algeria) and in the south-east of Tunisia and the Chott Djerid borders (El Hamma of Gabes, Tozeur and Kebili) corresponding to the discharge zones. However, the scaling potential decreases towards Algerian reliefs (Tademait and Tinrhert) representing aquifer recharge zones.