Hydrogeological Survey of Savcili Büyükoba Geothermal Field (Kaman, Kirsehir-Central Anatolia, Turkey)

Abstract

Savcili-Büyükoba geothermal field is located in the east of Kaman district of Kirsehir province of Central Anatolia. This study is focused on the evaluation of geological, hydrogeological, hydrogeochemical, geophysical drilling (SB-1, SB-2, SB-3, and SB-4 wells) studies. Previous investigations and exploration wells for producing of thermal waters were carried out by MTA and Iller Bankasi General Directorates in this field. Subsequently, Hacettepe University performed geological and hydrogeological studies. Within the framework of the study, geology, hydrogeology, water chemistry and isotope hydrology studies have been carried out and geology, hydrogeology maps and cross sections were prepared. Geological and hydrogeological properties of the reservoir rock were determined; the relationship of hot waters and the cold waters, the recharge area and a conceptual hydrothermal model of the studied area was proposed. The geological units consist of Kirsehir Metamorphics, Baranadag Granitoids, Barakli Formation, Mesedag Formation, Kizilirmak Formation and Alluvium. The basement complex is formed of Paleozoic aged Kirsehir metamorphics (marbles,schist,quartzite). Granitoids are Mesozoic (Late Cretaceous) aged. Eocene aged (Barakli and Mesedag Formations) marl, claystone, limestone, alternating clayey limestone sandstone and marl Pliocene (Kizilirmak Formation) deposits overlie unconformably on this basement. Quaternary aged alluvium lie at the top. Savcili-Büyükoba geothermal area is controlled by mainly NE-SW and N-S faults. Thermal waters emerge along the intersection of the faults. The basement rocks are Paleozoic Kirsehir metamorphics (marbles, quartzite) and Mesozoic (Late Crateceous) granodiorites are reservoir rocks and Eocene sediments constitute the caprock of the field. In the study area, Kirsehir metamorphics and granodiorites are basement rocks which are partially permeable that they have secondary porosity with tectonic activity. Alluvium is important aquifer for cold water. Temperature of thermal and mineral water springs in the field changes between 30°C - 34.5°C and average total flow rates of springs are 4.5 l/s. According to ionic content, the hydrochemical facies of the thermal waters are NaHCO3. Thermal waters of the study area closed to Local Meteoric Water Line (LMWL) and this suggests that geothermal waters have a meteoric origin.The low tritium content of Savcili spring shows that the thermal aquifer of Savcili-Büyükoba geothermal area is recharged by groundwater having relatively long residence time which represents a deep groundwater circulation system in the study area.