Thermohaline modelling of hot geothermal fluid systems in coastal environment: the Seferihisar-Balcova Area example (Turkey)
Final Report Abstract
The Seferihisar-Balçova Geothermal system (SBG), Turkey, is characterized by temperature and hydrochemical anomalies along the faults: thermal waters in northern Balçova are heated meteoric freshwater, whereas the hot springs of the southern Seferihisar region have a strong seawater contribution. Two approches were used to understand this phenomenon: Numerical simulations of fluid flow and heat transport and hydrochemical analyses. The simulations indicated that focused upsurge of hot water in faults induces a convective-like flow motion in surrounding units. Specifically, fault-induced convection cells generate seawater plumes that extend from the seafloor toward the faults. At fault intersections, seawater mixes with rising hot thermal waters. The resulting saline fluids ascend to the surface along the fault, driven by buoyant forces. In Balçova, thick alluvium, min or faults and regional flow prevent ascending salty water from spreading at the surface, whereas the weak recharge flow in the thin alluvium of the southern SBG is not sufficient to flush the ascending hot salty waters. Additionally, for the first time in this area a 3D numerical model of thermally-induced flow has been built. The 3D models indicated that the convective patterns likely develop in the fault plane. 3D thermal fingers can also develop at over-critical Rayleigh numbers, i.e. in highly permeable fractured areas. While these different convective modes certainly change the flow patterns and mixing interactions, the basic process of seawater intrusion remains the same as described in 2D.The hydrochemical studies support the numerical findings: faults appear to be the major conduits allowing for water-rocks interactions and thermalism to occur. In conclusion, both approaches suggest that the hydrochemical and hydrothermal activity of the SBG is likely controlled by the interaction between different rates of the regional flow from Horst and the thermal convection developing in the faults. These mechanisms could develop in any faulted geothermal system, with implications for minerals and energy migration in sedimentary basins.
Publications
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2009 Numerical simulations of density viscosity-dependent hot fluids in a geothermal field: the Seferihisar- Balçova Area example, Turkey 2nd International FEFLOW User Conference 14-18 September, 2009 Potsdam/Berlin, Germany. Conference papers CD-Rom
Magri, F., Akar, T., Pekdeger, A., Gemici, U.
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2009. Derivation of the coefficients of compressibility, thermal expansion and fluid density difference ratio for reproducing aqueous NaCl density. WASY White papers Vol. V., 85-92
Magri, F
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Numerical simulations of deep geothermal groundwater flow in the Seferihisar-Balçova Geothermal system, Turkey. Geophysical Research Abstracts, Vol. 11., Abstract No: EGU2009-1187, 20.-24/04/2009, Wien, Austria
Magri, F., Pekdeger A., Gemici, U., Akar, T.
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Investigation of Seferihisar-Balcova geothermal area by environmental isotopes. Geophysical Research Abstracts, Vol. 12, Abstract No: EGU2010-7911-1, 02-07/05/2010, Wien, Austria
Akar, T., Gemici, Ü., Pekdeger, A., Magri, F.
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Thermally induced seawater intrusion in the coastal aquifers of the Seferihisar-Balçova system, Western Anatolia, Turkey - results from thermohaline simulations. Geophysical Research Abstracts, Vol. 12, Abstract No: EGU2010- 1955-1, 02-07/05/2010, Wien, Austria
Magri, F., Akar, T., Pekdeger, A., Gemici, Ü.
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2011 Geothermal springs associated with buoyant-driven fluid flow in the faults of the Seferihisar-Balçova system, Western Anatolia, Turkey - results from 3D simulations. Geophysical Research Abstracts, Vol. 13, Abstract No: EGU2011-1865-1, 03-08/04/2011, Wien, Austria
Magri, F., Birner, J., Akar, T., Gemici, Ü., Pekdeger, A.
