| Title | Passive electrical monitoring of a geothermal doublet: Rittershoffen EGS project, northern Alsace |
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| Authors | Girard, J-F; Matthey P-D; Abdelfettah, Y; Sailhac, P; Dalmais, E; Maurer, V |
| Year | 2016 |
| Conference | European Geothermal Congress |
| Keywords | electrokinetic, geothermal exploitation, modelling, field experiment, Upper Rhine Graben |
| Abstract | Fluid movement in fractured and permeable rocks generates electrical signals via electrokinetic and conduction effects which are link to flow regimes, permeability, aperture of fractures, etc... Previous work in northern Alsace, at the EGS field of Soultz-sous-Forêts, have proved the detectability of electric signal recorded in surface linked with water circulation in the reservoir at 5 km deep. They demonstrated it was due to the metallic casing of the boreholes which create a short-circuit between surface and the deep fractured crystalline reservoir. The current project consists in continuous recording of the electrical field in surface, with one potential measurement directly connected to the boreholes casing of the Rittershoffen geothermal doublet designed to produce 24 MWth (170 °C, 70 l/s) and located at less than 10 km from Soultz-sous-Forêts. Data processing consists to lower the electric noise level, especially using the synchronous recording of the electrical field at a remote site to try to identify electrical signals link with water circulation in the reservoir. If this first step is achieved, the interpretation of these signals will consist to cluster the electric events, correlate them with production chronicles and micro-seismic activity. The final objective is to obtain a classification of the electrograms that could lead to characterize the evolution of the reservoir during production. |