Continuous and time-lapse magnetotelluric monitoring of low volume injection at Rittershoffen geothermal project, northern Alsace – France

Abdelfettah, Yassine; Sailhac, Pascal; Larnier, H.; Matthey, P.-D.; Schill, Eva

doi:10.1016/j.geothermics.2017.08.004

Cited by 20 publications

(10 citation statements)

References 25 publications

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“…MT has also recently been applied to monitor resistivity changes in volcanoes (Aizawa et al, 2013;Wawrzyniak et al, 2017;Ladanivskyy et al, 2018). However, the application of time-lapse MT continues to be challenging due to variations in geomagnetic activity, sources of anthropic noise and the stability of the MT setup (Abdelfettah et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018–2019 Mayotte seismovolcanic crisis

Darnet

Wawrzyniak

Tarits

et al. 2020

Journal of Volcanology and Geothermal Research

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A major seismovolcanic crisis has afflicted the islands of Mayotte, Comoros Archipelago, since May 2018, although the origin is debated. Magnetotellurics (MT), which is sensitive to hydrothermal and/or magmatic fluids and can map the subsurface electrical resistivity structure, can provide insight by revealing the internal structure of the volcanic system. In this paper, we report the results of a preliminary land and shallow marine MT survey performed on and offshore the island nearest the crisis. The 3D inversionderived electrical resistivity model suggests that the island is underlain by a shallow ~500-m-thick conductive layer atop a deeper, more resistive layer, possibly associated with a high-temperature geothermal system. At depths of ~15 km, the resistivity drops by almost two orders of magnitude, possibly due to partial melting. Further petrophysical and geophysical studies are underway for confirmation and to map the geometry and evolution of the volcanic system. Highlights► A major seismovolcanic crisis has afflicted the islands of Mayotte, Comoros Archipelago, since May 2018, although the origin is debated. ► We report the results of a preliminary land and shallow marine MT survey performed on and offshore the island nearest the crisis. ► The 3D inversion-derived electrical resistivity model suggests that the island is underlain by a shallow ~500-m-thick conductive layer atop a deeper, more resistive layer, possibly associated with a high-temperature geothermal system. ► At depths of ~15 km, the resistivity drops by almost two orders of magnitude, possibly due to partial melting.

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Section: Introductionmentioning

confidence: 99%

Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018–2019 Mayotte seismovolcanic crisis

Darnet

Wawrzyniak

Tarits

et al. 2020

Journal of Volcanology and Geothermal Research

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“…In practice, magnetotellurics (MT) is often used, primarily due to its large penetration depth (often several kilometers) and its use of naturally occurring sources. MT has been used to characterize EGS (MacFarlane et al., 2014) and also in a time‐lapse approach to monitor fluid injection and propagation (Abdelfettah et al., 2018; Peacock et al., 2012). MT offers some benefits compared to its seismic alternatives, but due to the diffusive nature of the EM fields and the very low frequencies involved, the method lacks spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

Permeability Enhancement From a Hydraulic Stimulation Imaged With Ground Penetrating Radar

Shakas

Maurer

Giertzuch

et al. 2020

Geophysical Research Letters

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“…In practice, magnetotellurics (MT) is often used, primarily due to its large penetration depth (often several kilometers) and its use of naturally occurring sources. MT has been used to characterize EGS (MacFarlane et al, 2014) and also in a time-lapse approach to monitor fluid injection and propagation (Abdelfettah et al, 2018;Peacock et al, 2012). MT offers some benefits compared to its seismic alternatives, but due to the diffusive nature of the EM fields and the very low frequencies involved, the method lacks spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

Permeability enhancement from a hydraulic stimulation imaged with Ground Penetrating Radar

Shakas

Maurer

Giertzuch

et al. 2020

Preprint

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We present evidence of permeability enhancement from hydraulic stimulation experiments in fractured crystalline rock. A total of 9.49 m 3 was injected in two fractured intervals of a 300 m long borehole. Repeated Ground Penetrating Radar (GPR) measurements in the same borehole were carried out prior to and following the stimulation. The initial measurements revealed fractures in the vicinity of the borehole that could be traced up to distances of 50 m away. The data measured post-stimulation were used in a difference-imaging approach to illuminate changes in the GPR reflections caused by the stimulations. The changes delineate the enhancement of a large and complex fracture network. These changes likely correspond to changes in local aperture, thus permeability. Our results indicate that borehole GPR yields unique information on subtle changes in hydraulic properties within a relatively large volume and provides a new perspective on the characterization and monitoring of deep geothermal reservoirs.Plain Language Summary Deep geothermal reservoirs are a renewable and carbon-neutral source of energy that is globally underutilized. Their principle is to efficiently extract heat energy from the Earth by circulating a fluid within a deep reservoir. Oftentimes, reservoirs need to be Engineered (or Enhanced), leading to the term Engineered Geothermal Systems (EGS). EGS rely on enhancing a reservoir's permeability, its ability to allow for fluid flow. Geophysical remote sensing techniques are useful in illuminating changes in properties of an EGS, and in monitoring its evolution. In crystalline bedrock environments, borehole Ground Penetrating Radar (GPR) is especially useful in mapping contrasts between rock and water. Here, we present results from a hydraulic stimulation experiment that aimed at enhancing a reservoir's permeability by injecting water in existing fractures. Using GPR single-hole reflection imaging, we were able to map existing fractures within a relatively large volume. By repeating the measurements after the stimulations, we were able to detect changes in their reflectivity that most likely arise from permeability changes caused by the stimulation. The ability of GPR borehole measurements to image changes of the hydraulic properties in such high resolution offers a new and exciting perspective for characterizing and monitoring EGS.

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Continuous and time-lapse magnetotelluric monitoring of low volume injection at Rittershoffen geothermal project, northern Alsace – France

Cited by 20 publications

References 25 publications

Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018–2019 Mayotte seismovolcanic crisis

Mapping the geometry of volcanic systems with magnetotelluric soundings: Results from a land and marine magnetotelluric survey performed during the 2018–2019 Mayotte seismovolcanic crisis

Permeability Enhancement From a Hydraulic Stimulation Imaged With Ground Penetrating Radar

Permeability enhancement from a hydraulic stimulation imaged with Ground Penetrating Radar

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