| Title | Relation Between Induced Seismicity and Geothermal Systems: A Case Study from the Gediz Graben, Western Anatolia, Turkey |
|---|---|
| Authors | Huseyin UYTUN, Hasan SOZBILIR, Alper BABA, Kemal YILDIZDAG, Murat KARAS |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Induced seismicity, active fault, geothermal, reinjection, hydraulic fracturing. |
| Abstract | It is well known that induced seismicity associated with geothermal systems occurs when the fluid pressure in a fault or fracture reaches a critical value .This study has been focused on induced seismicity associated with operating geothermal systems since 2015 in the Gediz Graben. Geothermal fluid in Gediz Graben originates from structural zones of low angle Gediz detachment fault of Quaternary age and high angle normal faults of Holocene age. For the geothermal application, many wells with the function of production and reinjection have been drilled with a depth range from 1000 to 3500 m in the Graben. In this study, the seismic data of Kandilli Observatory - Earthquake Research Institute, Prime Ministry Disaster - Emergency Management Authority and the geothermal well data of Manisa Investment, Monitoring - Coordination Directorates were used. Production - reinjection and seismic data were evaluated together with the tectonics and geology of the region by using Geographic Information System-based program Quantum GIS (QGIS). In that analysis, seismicity was observed especially around geothermal wells drilled for reinjection. It is concluded that earthquakes with magnitude 1-3 can be related to the geothermal activity. However, no direct correlation was found between the pressure, flow rate and the earthquake magnitude of the injected fluids. No correlation was observed between the high pressures or flow reinjection induced seismicity. In addition to the reinjection process, micro-earthquakes were observed during the hydraulic fracturing process which may occur due to reactivation of pre-existing faults. To examine that incident in more detail, the seismometers should be deployed near to the power plants and following that, the change of injection flow and pressure varying with time together with lithology should be determined. A method called “traffic light system†has been using especially in countries where enhanced geothermal system applications were used, to trace production and reinjection activities. In worst-case situations, these activities in power plants can be halted using that method. Concerning geothermal power plants in Western Anatolia, detailed studies should be conducted to estimate the relationship between geothermal production-reinjection activities with seismicity subsequent to fulfillment of infrastructure requirements. |