Geochemical evaluation and conceptual modeling of Edremit geothermal field

Avşar, Özgür
Edremit geothermal field with 42-62 °C discharge temperatures is utilized for space heating. Alternation of permeable and impermeable units created two superimposed aquifers in the area: upper unconfined and lower confined. Water samples from 21 (hot, warm, cold) wells were taken in this study. 8 of these wells penetrate the deeper confined, while 13 penetrate the shallower unconfined aquifer. Geochemical analysis revealed Na+K–SO4 nature for the hot (>40°C), Ca–HCO3 nature for the cold (<30°C) and Ca–SO4 nature for the warm (30-40°C) waters. δ18O-δD compositions point to a meteoric origin for all waters, while 14C analyses suggest longer subsurface residence times for the hot, compared to the cold/warm waters. Chemical and isotopic compositions indicate that “mixing” and “water-rock interaction” are the possible subsurface processes. When silica and cation geothermometers are evaluated together with fluid mineral equilibria calculations, a 110°C reservoir temperature is expected in the field. Saturation indices indicate potential silica scaling for waters at temperatures lower than discharge temperatures. Hydrogeology of the study area is highly affected by faults. The groundwater is percolated (down to 3 km depth) via deep seated step faults, heated at depth and ascends to surface at the low lands, especially through intersection of buried, mid-graben faults. During its ascent towards surface, geothermal water invades the two superimposed aquifers and mixing between hot and cold waters takes place in the aquifers. Resource assessment studies suggest a 3.45x1013 kJ accessible resource base and 9.1 MWt recoverable heat energy for Edremit geothermal field with 90% probability.
Citation Formats
Ö. Avşar, “Geochemical evaluation and conceptual modeling of Edremit geothermal field,” Ph.D. - Doctoral Program, Middle East Technical University, 2011.