Hydrogeological investigations on Balçova geothermal system in Turkey

The Balc¸ova geothermal system is situated within the confines of Izmir City, Turkey. It is located along the Izmir Fault zone, trending E–W. It has formed a hot water reservoir that is currently exploited for district heating of the nearby Balc¸ova-Narlidere area. Geoscientific studies on the area around the Balc¸ova geothermal field indicate that regional tectonics coupled with a major fault system has created NW–N–NE trending permeable pathways for a geothermal system, starting from a delimited intake area on the Seferihisar Horst in the south to the outflowing area in the north. The Balc¸ova geothermal system is a fracture zone system in which hot water ascends over an area of about 2 km along a major fracture zone associated with the Agamemnon Fault, reaching almost boiling temperatures close to the surface. The hot water discharges via two concealed horizontal flows, one in the alluvium (upper 100 m) and another deeper one in more permeable, ill-defined layers in the flysch formation between 400 and 700 m depth. The two concealed outflows and the steeply dipping fracture zone constitute the presently exploited reservoir, which extends for as much as 1.5 km from the feeding fracture zone. The natural direct discharge of the system was 2.5 kg/s; the surface heat discharge of the system is estimated at a minimum of 9.5 MWt. The average max. total production rate of all the production wells was 135 kg/s during the 2000–2001 heating season. The contribution of recharge to Balc¸ova geothermal field production was estimated at about 50kg/s. # 2003 CNR. Published by Elsevier Ltd. All rights reserved.