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Title

Deep electrical resistivity tomography for the prospection of low- to medium-enthalpy geothermal resources

Authors
Fischanger, Federico
Gance, Julien
Cocchiararo, Giuseppe
Morelli, Gianfranco
Published in Geophysical Journal International. 2019, vol. 219, no. 3, p. 2056-2072
Abstract SUMMARY The growth of the geothermal industry sector requires innovative methods to reduce explo- ration costs whilst minimizing uncertainty during subsurface exploration. Until now geoelec- trical prospection had to trade between logistically complex cabled technologies reaching a few hundreds meters deep versus shallow-reaching prospecting methods commonly used in hydro-geophysical studies. We present a recent technology for geoelectrical prospection, and show how geoelectrical methods may allow the investigation of medium-enthalpy geothermal resources until about 1 km depth. The use of the new acquisition system, which is made of a distributed set of independent electrical potential recorders, enabled us to tackle logistics and noise data issues typical of urbanized areas. We acquired a 4.5-km-long 2-D geoelectrical survey in an industrial area to investigate the subsurface structure of a sedimentary sequence that was the target of a ∼700 m geothermal exploration well (Geo-01, Satigny) in the Greater Geneva Basin, Western Switzerland. To show the reliability of this new method we compared the acquired resistivity data against reflection seismic and gravimetric data and well logs. The processed resistivity model is consistent with the interpretation of the active-seismic data and density variations computed from the inversion of the residual Bouguer anomaly. The combination of the resistivity and gravity models suggest the presence of a low resistivity and low density body crossing Mesozoic geological units up to Palaeogene–Neogene units that can be used for medium-enthalpy geothermal exploitation. Our work points out how new geoelectrical methods may be used to identify thermal groundwater at depth. This new cost- efficient technology may become an effective and reliable exploration method for the imaging of shallow geothermal resources.
Keywords Electrical propertiesFracture and flowPermeability and porosity
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Structures
Research group Crustal Deformation and Fluid Flow
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CARRIER, Aurore et al. Deep electrical resistivity tomography for the prospection of low- to medium-enthalpy geothermal resources. In: Geophysical Journal International, 2019, vol. 219, n° 3, p. 2056-2072. doi: 10.1093/gji/ggz411 https://archive-ouverte.unige.ch/unige:124619

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Deposited on : 2019-10-18

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