Kizildere geothermal field is located in the Aegean graben systems. The study area comprises Kizilkaya, Igdecik, Sazak, Kolonkaya, and Tosunlar formations consisting of marbles, limestones, conglomerates, sandstones, travertines, and alluviums. The wells were drilled to develop the Kizildere geothermal field, and the reservoir temperatures in the wells were various between 170 and 212 °C. There are three reservoir rocks in the Kizildere geothermal area. The top reservoir rock is limestone with limited lateral continuity in the Pliocene-aged Sazak formation. The limestones have low porosity, low permeability, and low temperature at about 180 °C compared to other reservoir rocks. The middle reservoir rock, which has a slightly higher porosity and permeability, is represented by Igdecik formation consisting of the alternation of marble-quartz-schist. It has known that there is a hydrostatic pressure relation between these two aquifers. The quartzites are the deepest reservoir in the Kizildere region. According to the data in R-1 well, quartzites have high permeability and high temperature, which is about 242 °C. The water analysis in the Schoeller diagram demonstrated that the origins of water were the same; however, the amount of ion in water was different. According to the Piper diagram, water samples were classified as a water class with carbonate alkalinity. Finally, the Giggenbach diagram analysis confirmed that the water class of almost all of the water samples were determined as partially in equilibrium condition.