Heidelberg 2015 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 10: Ozeanographie
UP 10.1: Vortrag
Donnerstag, 26. März 2015, 17:00–17:15, G/gHS
The role of shallow ground water 3He/4He ratios in geothermal energy potential and fault zone characterisation — •Florian Freundt1, Sami Al Najem2, Gerhard Schmidt2, Werner Aeschbach-Hertig1, Margot Isenbeck-Schröter2, and Michael Kraml3 — 1Institute of Environmental Physics, Heidelberg University — 2Institute of Earth Sciences, Heidelberg University — 3GeoThermal Engineering GmbH
Large-scale geothermal energy production relies on extensive characterization of the target fault system: its spatial location as well as its hydraulic permeability. Current geophysical methods (e.g. 3D reflection seismics) offer only a limited insight in hydraulic permeability, which the TRACE project aims to expand by applying a multi tracer analysis on shallow ground water above the target zone. 3He/4He ratios are one important part of this approach, offering a tool to identify mantle and crustal influences in the meteorically dominated shallow ground water. Data from a sampling campaign in the northern Upper Rhine Graben, close to Groß-Gerau, Germany, shows promising results, where elevated isotope ratios coincide with characteristic geochemical data, the fault location, and a previously known saltwater anomaly spatially defined by new geochemical data. Higher saline NaCl-dominated waters show an impact of mantle fluids revealed by 3He/4He isotope analysis. The ratio is highest where the main fault of the northern Upper Rhine Graben crosses the Rhine river. This suggests that the fault is hydraulically active and connects ascending deep fluids with the shallow aquifer.