Geothermal energy is one of the most promising sources in Azerbaijan. There are different types of ground or surface heat sources, such as mud volcanoes, mineral water, and deep wells. In the Azerbaijan territory, no active volcanoes and geysers turn out to be present. However, geothermal energy can be extracted from many wells where reservoir temperatures of thermal fluid are higher than 90°C. Especially, the Greater and Lesser Caucasus, the Absheron Peninsula, and Talysh region are characterized by the presence of geothermal fluids. The reservoirs where thermal fluid was discovered and partially studied in several wells developed for oil and gas in the Kur basin and the Precaspian-Guba region.