Geophysical monitoring of leakages in shallow groundwater from deep compressed air energy storage

Said Attia al Hagrey1, Daniel Köhn1, Carla E. Wiegers1, Dirk Schäfer1, Wolfgang Rabbel1
1 Institut für Geowissenschaften, Universität Kiel

O 11.5 in Wärme-, Energie- und Kohlenstoffspeicherung im Untergrund

29.05.2014, 15:20-15:40, H18, NW II


Renewable energy resources are intermittent and need a buffer storage to bridge the time-gap between production and demand peaks. North German Basin has favorable conditions and a very large capacity for compressed air energy storage (CAES) in porous saltwater reservoirs and salt cavities. However, the injected CAES and even saltwater can seep along weak zones and fractures upwards and migrate into shallow groundwater aquifers. These gas and fluid phase leakages cause changes in the electrical resistivity, density and elastic moduli of these aquifers, and justify applications of geophysical techniques. Our current interdisciplinary project ANGUS+ deals with impacts of using geologic subsurface as a thermal, electric or material storage in context with alternative energy resources. Our main task is to develop a geophysical monitoring strategy using integrative geophysical techniques on almost realistic scenarios in the North German Basin.


Using numerical simulations we study here the feasibility of techniques of elastic full wave inversion FWI, electric resistivity tomography ERT, electromagnetic induction EMI and gravity in detecting these groundwater leakages in the underground of Northern Germany.


A real geological formation in Northern Germany was chosen as a typical scenario. No CAES is planned at this site, but the geological structure and parameters of shallow potable aquifers are well known. With help of the user interface PetraSim the geological data were imported into the simulation program TOUGH 2-MP (EOS3). A leakage rate of 1 kg/s compressed air was assumed for 10 years and the potential three dimensional spreading of gas in the formation was simulated. Analogously a leakage of saltwater from deeper formations into the shallow aquifers was simulated for another geological structure.


These hydrogeological leakage models are transferred in geophysical models using realistic parameterization prevailing in the North Germany Basin and adequate petrophysical laws. These models are used to generate synthetic datasets which in turn are reconstructed to reproduce the underground models.


Results reflect the capability of geophysical techniques to detect and monitor these leakages. CAES leakages can be characterized by their resistivity highs and mass deficit, and saltwater intrusions by their resistivity lows and mass excess. The lower boundary value of detectability can be determined. Full wave inversion FWI technique can map the CAES plume better than the saltwater plume due to their different impedance contrast. Applied integrative techniques complement each other. Gravity and FWI methods are more sensitive to CAES plumes yielding stronger density contrast than saltwater intrusions, whereas ERT and EMI are more sensitive to the conductive saltwater than the resistive CAES.





This study has been carried out within the framework of ANGUS+ research project funded by the German Federal Ministry of Education and Research (BMBF).

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Letzte Änderung 01.11.2013