Numerical modelling of Balçova-Narlidere Geothermal Field, Izmir, Turkey

Since Turkey is located on an active tectonic belt due to its geological and geographical location, it is in a rich position among the countries of the world in terms of geothermal energy. The Balçova-Narlıdere Geothermal Field (BNGF) is located on the southern edge of Izmir Bay of the Aegean coast and is 11km far from southwest of Izmir city. This geothermal play represents the first field in Turkey used for the application of direct heating. Beginning in 1960, studies about hydrogeology, hydrochemistry, reservoir performance, temperature analysis and use of geothermal water are still going on in the Balçova-Narlıdere Geothermal field. Currently, there are 26 wells drilled by Izmir Geothermal Energy Company in the field. Among 26 wells, 11 are deep production wells, 5 wells are shallow production wells, 4 wells are re-injection wells, 4 wells are gradient wells for research goals and the rest 2 wells are not feasible to utilize. There was a renewal of six wells from 2013 to 2015. Besides these 26 wells, there are additional 11 wells drilled which belong to Izmir Governorship Investment Monitoring and Coordination Department. Shallow wells correspond to depths up to 200m, while deep wells range from 410m to 1100m depth. The energy obtained from Balçova-Narlıdere Geothermal field has been supplied to approximately 38500 residences, beginning from 1996. A numerical simulation of the Balçova-Narlıdere Geothermal field has been implemented to predict the future reservoir performance regarding temperature and pressure states. Model construction, natural state modelling using EOS1 in BNGF and history match of injection and production data are stages of simulation conducted prior to future reservoir performance forecasting. The performance prediction has been carried out according to three production/injection scenarios. In the Scenario-I, the production and injection flow rates have been kept the same for next 20 years beginning from 2008. In Scenario-II, the simulation has been carried out for 15 years' period. Initially, the production and injection rates remain the same for the first three years, after which they have been increased by 10% and 17%, respectively, every three years. Scenario-III includes a new BT-1 well drilled at depth of 765m to operate as an injection well from the start of the simulation. Here, about 60 percent of injected water through well BD-8 has been transferred to newly operating well BT-1. Scenario-III has the same production scenario as Scenario-II. From the results of all three scenarios, it can be deduced that there is no important change in bottomhole pressure in deep wells. However, in Scenario-II and III shallow wells B-5 and B-10 represented pressure drop. By comparing the first two scenarios, Scenario-I is more feasible as in the Scenario-II temperature of deep wells in the field was reduced more than in Scenario-I. Having said that, in Scenario I, the temperature in the eastern side deep wells reduced significantly while in the western side deep wells decreased less, in comparison with deep wells in Scenario-III. Keywords: Balçova-Narlıdere Geothermal Field, Numerical simulation, Natural State Modelling, Hydrogeology, Hydrochemistry.