Microseismic imaging of a geothermal reservoir stimulation

Dyer, B.; Schanz, Ulrich; Ladner, Florentin; Häring, Markus; Spillman, Thomas

doi:10.1190/1.2954024

Cited by 73 publications

(68 citation statements)

References 7 publications

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“…On December 8th, 2006, three events ocurred that exceeded the safety threshold for continued stimulation (including one event with a magnitude M L = 3.4), so that injection was stopped prematurely and the well was vented. In the following days about one third of the injected water volume flowed back out of the well (Häring et al 2008). the seismic activity declined rapidly thereafter, but even more than two years later, sporadic microseismicity was being detected in the stimulated rock volume by the downhole-instruments.…”

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

“…An overview of the project, including a documentation of injection pressures and flow rates, can be found in Häring et al (2008). First analyses of the induced microseismicity have been published by Kumano et al (2007), Asanuma et al (2007) and Dyer et al (2008). Under contract from Geopower basel AG, the swiss seismological service (sED) performed an extensive study that includes seismotectonic aspects, scaling relationships between local magnitude (M L ) and moment magnitude (M w ), statistical analyses of the temporal and spacial evolution of the microseismicity, and ground shaking scenarios for possible stronger events based on macroseismic models and numerical calculations (sED 2007).…”

Section: Introductionmentioning

confidence: 99%

“…to stimulate the reservoir for a "hot dry rock" geothermal project, that was initiated by a private/public consortium in the city of basel, approximately 11500 m 3 of water were injected at high pressures into a 5 km deep well, between December 2nd and 8th, 2006, (Häring et al 2008). A six-sensor borehole array, installed by the operators of the project at depths between 317 and 2740 meters around the well to monitor the induced seismicity, recorded more than 10500 seismic events during the injection phase.…”

Section: Introductionmentioning

confidence: 99%

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Earthquake focal mechanisms of the induced seismicity in 2006 and 2007 below Basel (Switzerland)

Deichmann

Ernst

2009

Swiss J. Geosci.

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to stimulate the reservoir for a "hot dry rock" geothermal project, that was initiated by a private/public consortium in the city of basel, approximately 11500 m 3 of water were injected between December 2nd and 8th, 2006, at high pressures into a 5 km deep well. More than 10500 seismic events were recorded during the injection phase, and minor sporadic seismic activity was still occurring more than two years later. the present article documents the focal mechanisms of the 28 strongest events, with M L between 1.7 and 3.4, that have been obtained by the swiss seismological service (sED) during and after the stimulation. the analysis is based on data that was recorded by a six-station borehole network, operated by the project developers, as well as by several permanent and temporary surface networks. the hypocenters of the events are located inside the stimulated rock volume at depths between 4 and 5 km within the crystalline basement. Of the 28 faultplane solutions two are normal faulting mechanisms and one is a strike-slip mechanism with a strong normal component. All others are typical strike-slip mechanisms with mostly Ns and EW striking nodal planes. As a consequence, the t-axes are all nearly horizontal and oriented in a NE or sW direction (mean azimuth 46 ± 11 degrees) and the P-axes of the strike-slip events point in a NW or sE direction (mean azimuth 138 ± 13 degrees). Overall, the observed focal mechanisms agree with what would be expected from both the stress observations within the well and the stress field derived from the previously known natural seismicity. Introductionto stimulate the reservoir for a "hot dry rock" geothermal project, that was initiated by a private/public consortium in the city of basel, approximately 11500 m 3 of water were injected at high pressures into a 5 km deep well, between December 2nd and 8th, 2006, (Häring et al. 2008). A six-sensor borehole array, installed by the operators of the project at depths between 317 and 2740 meters around the well to monitor the induced seismicity, recorded more than 10500 seismic events during the injection phase. On December 8th, 2006, three events ocurred that exceeded the safety threshold for continued stimulation (including one event with a magnitude M L = 3.4), so that injection was stopped prematurely and the well was vented. In the following days about one third of the injected water volume flowed back out of the well (Häring et al. 2008). the seismic activity declined rapidly thereafter, but even more than two years later, sporadic microseismicity was being detected in the stimulated rock volume by the downhole-instruments.Meanwhile, despite the setback with respect to the original plan, efforts to analyse the large amount of data generated by this project have produced first results, some in the form of internal reports to the sponsor (Geopower basel AG), and others as publications in the open literature. An overview of the project, including a documentation of injection pressures and flow rates, can be found in Häring et...

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Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Earthquake focal mechanisms of the induced seismicity in 2006 and 2007 below Basel (Switzerland)

Deichmann

Ernst

2009

Swiss J. Geosci.

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“…A detailed overview of the project can be found in Häring et al (2008). First analyses of the induced microseismicity have been published by Kumano et al (2007), Asanuma et al (2007), Dyer et al (2008), and .…”

Section: The Earthquake Sequence Of Baselmentioning

confidence: 99%

Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland

Bethmann

Deichmann

Martin

2011

Bulletin of the Seismological Society of America

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Theoretical considerations and empirical regressions show that, in the magnitude range between 3 and 5, local magnitude, M L , and moment magnitude, M w , scale 1∶1. Previous studies suggest that for smaller magnitudes this 1∶1 scaling breaks down. However, the scatter between M L and M w at small magnitudes is usually large and the resulting scaling relations are therefore uncertain. In an attempt to reduce these uncertainties, we first analyze the M L versus M w relation based on 195 events, induced by the stimulation of a geothermal reservoir below the city of Basel, Switzerland. Values of M L range from 0.7 to 3.4. From these data we derive a scaling of M L ∼ 1:5M w over the given magnitude range. We then compare peak Wood-Anderson amplitudes to the low-frequency plateau of the displacement spectra for six sequences of similar earthquakes in Switzerland in the range of 0:5 ≤ M L ≤ 4:1. Because effects due to the radiation pattern and to the propagation path between source and receiver are nearly identical at a particular station for all events in a given sequence, the scatter in the data is substantially reduced. Again we obtain a scaling equivalent to M L ∼ 1:5M w . Based on simulations using synthetic source time functions for different magnitudes and Q values estimated from spectral ratios between downhole and surface recordings, we conclude that the observed scaling can be explained by attenuation and scattering along the path. Other effects that could explain the observed magnitude scaling, such as a possible systematic increase of stress drop or rupture velocity with moment magnitude, are masked by attenuation along the path.

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Pore pressure behavior at the shut‐in phase and causality of large induced seismicity at Basel, Switzerland

et al. 2017

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Induced seismicity with unexpectedly large magnitude often occurs after shut‐in or end of stimulation, generating concerns at the end of stimulation. We investigated the physical mechanism of large‐magnitude induced seismicity during shut‐in following the hydraulic stimulation at Basel, Switzerland. Larger postinjection events occurred at the periphery of the seismic cloud. We estimated the pore pressure required to cause shear slip using Coulomb failure criteria from stress information, geometry of the fault planes of microseismic events, and a constant coefficient of friction. Time series analysis of pore pressure distribution indicated that pore pressure migrated to the far field even after shut‐in. Redistribution of pore pressure at shut‐in brought sufficient pore pressure increase to induce seismicity in the peripheral region. After shut‐in, the pore pressure gradient away from the well lessened and eventually pressure became uniform. These observations suggest that the higher pore pressure, which remained in the vicinity of the injection point, shifted to the farthest field. Shut‐in pressure migration caused uniform pore pressure distribution at the edge of the seismic zone. Shut‐in pressure destabilized a large part of the fault located at the edge of the seismic cloud, resulting in the shear slip of a large section of the fault. Meanwhile, during stimulation, only some parts of the fault entered the critical state because of the pressure gradient. The resulting shear slip on that specific part causes moderate magnitude events at most.

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Microseismic imaging of a geothermal reservoir stimulation

Cited by 73 publications

References 7 publications

Earthquake focal mechanisms of the induced seismicity in 2006 and 2007 below Basel (Switzerland)

Earthquake focal mechanisms of the induced seismicity in 2006 and 2007 below Basel (Switzerland)

Scaling Relations of Local Magnitude versus Moment Magnitude for Sequences of Similar Earthquakes in Switzerland

Pore pressure behavior at the shut‐in phase and causality of large induced seismicity at Basel, Switzerland

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