In-situ Measurement of Physico-Chemical Parameters of Geothermal Waters and Brines – Results of R&D Project PETher
Elisabeth SCHRÖDER, Michael KRAML, Klaus THOMAUSKE, Dietmar KUHN, Marco JODOCY, Kirsten THORWART, Markus WOLFGRAMM
[Karlsruhe Institute of Technology, Germany]
PETher was a research project implemented on behalf of the German Federal Ministry for Economic Affairs and Energy (BMWi). The project team consisted of KIT (Karlsruhe Institute of Technology; technical project coordination), GeoT (GeoThermal Engineering GmbH; geoscientific project coordination), gec-co (Global Engineering and Consulting GmbH) and GTN (Geothermie Neubrandenburg GmbH). The objective of PETher was to determine physico-chemical properties (specific isobaric heat capacity, kinematic viscosity, and density) of geothermal water under conditions that reflect the conditions to be found in geothermal utilizations (pressure, temperature, salinity of the brine). The knowledge of these physico-chemical properties is crucial in order to estimate the thermal output and therefore the economic viability as well as to optimize the plant or heating station design during the development and operation of a geothermal project. Up to now, only a limited number of measurements of selected physical properties have been made, usually under laboratory conditions as well as for individual geothermal plants. Currently available mathematical formulae describing the physico-chemical properties are typically not valid for the conditions to be found in geothermal applications. Also, geothermal waters in Germany have not been subject of detailed measurements systematically performed under operational conditions. In this project, the thermo-physical properties of geothermal water are measured under in-situ-conditions as functions of pressure, temperature, and salinity. The measurements were taking place directly at several geothermal sites located in Germany’s hydrogeothermal key regions. Those are the Molasse Basin, the Upper Rhine Graben, and the North German Basin. For doing the in-situ measurements, a mobile testing unit was developed and refined with instruments specifically designed in-house (KIT) to meet any geothermal reservoir conditions to be found in Germany. The obtained results were compared with standard analytical methods as well as used to calibrate systematic laboratory measurements that simulate the encountered in-situ conditions. The modelled type curves contribute to a more realistic prediction of the thermal output of future geothermal plants. The results cannot only be applied in Germany but are representative for all NaCl-dominated geothermal brines of sedimentary basins with underlying crystalline basement in the investigated temperature range (up to 170 °C) all over the world.
|        Topic: Power Generation||Paper Number: 26015|