Application of selected geothermometers to exploration of low-enthalpy thermal water: the Sudetic Geothermal Region in Poland

摘要

The most important intakes of thermal waters within the Sudetic Geothermal Region occur in three separate hydrogeothermal systems: (1) Ladek, (2) Duszniki and (3) Cieplice. All these waters are of meteoric origin and circulate in crystalline rocks to different depths. Their outflow temperatures are between less than 20℃ and to about 87℃. To evaluate the geothermal fields in the light of their prospectiveness, to further exploration of thermal energy resources, we took an effort to apply selected iso-topic and chemical geothermometers to assess the maximum possible temperatures, which may be found in the reservoirs. The only chemical geothermometers which give a reliable range of reservoir temperatures are SiO_2 (chalcedony), Na-Ka-Ca and partly Na-K ones. The oxygen isotopic geothermometer in the SO_4-H_2O system gives a real range of estimated reservoir temperatures only for deeply circulating waters in the Cieplice area. On the other hand, in the case of CO_2 rich waters in the Duszniki area, where outflow temperatures do not exceed 30℃, application of chemical or isotopic temperature indicators always leads to erroneous results due to the lack of equilibrium in the thermodynamic system of water-rock interaction.