Analysis of induced seismicity in geothermal reservoirs – An overview

Zang, Arno; Øye, V.; Jousset, Philippe; Deichmann, Nicholas; Gritto, Roland; McGarr, A.; Majer, Ernest L.; Bruhn, David

doi:10.1016/j.geothermics.2014.06.005

Cited by 209 publications

(127 citation statements)

References 113 publications

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“…The constant b is typically close to 1 for natural seismicity, and is typically higher for earthquake swarms (lacking a clear main shock), for increasing material heterogeneity, for aftershocks, and for areas of having a high geothermal temperature gradient (Kulhanek, 2005;Zang et al, 2014). This relationship is generally displayed in a plot of seismic event magnitude vs. log (frequency M ≥ x).…”

Section: Microseismic Monitoringmentioning

confidence: 95%

The Northwest Geysers EGS Demonstration Project, California

García¹,

Hartline²,

Walters³

et al. 2016

Geothermics

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a b s t r a c tAn Enhanced Geothermal System (EGS) Demonstration Project is currently underway in the Northwest Geysers. The project goal is to demonstrate the feasibility of stimulating a deep high-temperature reservoir (HTR) (up to 400 • C, 750 • F). Two previously abandoned wells, Prati State 31 (PS-31) and Prati 32 (P-32), were reopened and deepened to be used as an injection and production doublet to stimulate the HTR. The deepened portions of both wells have conductive temperature gradients of 10 • F/100 ft (182 • C/km), produce connate native fluids and magmatic gas, and the rocks were isotopically unexchanged by meteoric water. The ambient temperature meteoric water injected into these hot dry rocks has evidently created a permeability volume of several cubic kilometers as determined by seismic monitoring. Preliminary isotopic analyses of the injected and produced water indicate that 50-75% of the steam from the created EGS reservoir is injection-derived.

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Section: Microseismic Monitoringmentioning

confidence: 95%

The Northwest Geysers EGS Demonstration Project, California

García¹,

Hartline²,

Walters³

et al. 2016

Geothermics

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“…The total amount of volume of fluid injection is therefore 200 m 3 . The amount of injected volume is far lower than what is often used in geothermal sites, i.e., >10 000 m 3 (McGarr 2014;Zang et al 2014). However, it should be noted that the model is in two dimensions (2D) with a unit thickness of 1 m in the out-of-plane direction.…”

Section: Model Description and Parametersmentioning

confidence: 99%

“…Fluid injection can cause stress changes locally through the stress shadow effect, as well as reactivation of pre-existing joints and slip of nearby faults, which consequently can trigger larger magnitude events (LMEs), e.g., Basel EGS (Häring et al 2008;Kraft et al 2009;Mukuhira et al 2013). Larger magnitude events induced in geothermal sites were collected and analyzed in Zang et al (2014).…”

Section: Introductionmentioning

confidence: 99%

Discrete element modeling of fluid injection–induced seismicity and activation of nearby fault

et al. 2015

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Enhanced geothermal systems, shale gas, and geological carbon sequestration all require underground fluid injection in high-pressure conditions. Fluid injection creates fractures, induces seismicity, and has the potential to reactivate nearby faults that can generate a large magnitude earthquake. Mechanisms of fluid injection-induced seismicity and fault reactivation should be better understood to be able to mitigate larger events triggered by fluid injection. This study investigates fluid injection, induced seismicity, and triggering of fault rupture using hydromechanical-coupled discrete element models. Results show that a small amount of fluid pressure perturbation can trigger fault ruptures that are critically oriented and stressed. Induced seismicity by rock failure shows in general higher b-values (slope of magnitude-frequency relation) compared to seismicity triggered by the fault fracture slip. Numerical results closely resemble observations from geothermal and shale-gas fields and demonstrate that discrete element modeling has the potential to be applied in the field as a tool for predicting induced seismicity prior to in situ injection.Key words: induced seismicity, fault reactivation, large-magnitude events, triggered seismicity, magnitude-frequency relation b-value.Résumé : Les systèmes géothermiques améliorés, l'extraction du gaz de schiste et la séquestration du carbone géologique nécessitent l'injection de fluides à haute pression dans le sous sol. Ce type d'injection génère des fractures, cause des secousses sismiques et peut réactiver des failles avoisinantes, lesquelles peuvent provoquer des tremblements de terre de forte magnitude. Il serait utile de mieux comprendre les mécanismes des séismes induits par l'injection de fluides et ceux de la réactivation de failles, et ce afin d'être en mesure de prévenir les événements graves causés par l'injection de fluide. Dans le présent article, on étudie l'injection de fluides, la sismicité induite et le déclenchement de ruptures de failles à l'aide de modèles couplés hydromécaniques basés sur la méthode des éléments discrets. Les résultats montrent qu'une légère perturbation de la pression du fluide injecté peut déclencher des ruptures d'orientation critique soumises à des contraintes. La sismicité induite par la rupture de roches est généralement caractérisée par des valeurs de b (pente de la fonction de relation entre la magnitude et la fréquence) par rapport à celles observées dans le cas de la sismicité déclenchée par le cisaillement de rupture des failles. Les résultats numériques se rapprochent beaucoup des observations faites sur les sites géothermiques ou d'extraction de gaz de schiste et montrent que la modélisation basée sur la méthode des éléments discrets pourrait être utilisée sur ces sites comme outil servant à prédire la sismicité induite avant l'injection de fluides in situ. [Traduit par la Rédaction] Mots-clés : sismicité induite, réactivation de failles, incidents de forte magnitude, sismicité déclenchée, valeur de b: pente ...

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“…The contemporary in situ upper crustal stress field is of key importance for our understanding of geodynamic processes such as natural and induced seismicity (Häring et al, 2008;Gaucher et al, 2015;Scholz, 2002;Heidbach and BenAvraham, 2007;Townend and Zoback, 2004;Zang et al, 2014). The stress field also provides critical a priori information for safe and sustainable underground engineering such as wellbore planning and stability, reservoir management, tunnelling, mining, and underground waste storage (Altmann et al, 2014;Cornet et al, 1997;Fuchs and Müller, 2001;Moeck and Backers, 2011;Tingay et al, 2008;Zang et al, 2013;Ziegler et al, 2015;Zoback, 2010).…”

Section: Introductionmentioning

confidence: 99%

A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin

Ziegler

Heidbach

Reinecker³

et al. 2016

Solid Earth

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Abstract. The knowledge of the contemporary in situ stress state is a key issue for safe and sustainable subsurface engineering. However, information on the orientation and magnitudes of the stress state is limited and often not available for the areas of interest. Therefore 3-D geomechanicalnumerical modelling is used to estimate the in situ stress state and the distance of faults from failure for application in subsurface engineering. The main challenge in this approach is to bridge the gap in scale between the widely scattered data used for calibration of the model and the high resolution in the target area required for the application. We present a multi-stage 3-D geomechanical-numerical approach which provides a state-of-the-art model of the stress field for a reservoir-scale area from widely scattered data records. Therefore, we first use a large-scale regional model which is calibrated by available stress data and provides the full 3-D stress tensor at discrete points in the entire model volume. The modelled stress state is used subsequently for the calibration of a smaller-scale model located within the large-scale model in an area without any observed stress data records. We exemplify this approach with two-stages for the area around Munich in the German Molasse Basin. As an example of application, we estimate the scalar values for slip tendency and fracture potential from the model results as measures for the criticality of fault reactivation in the reservoir-scale model. The modelling results show that variations due to uncertainties in the input data are mainly introduced by the uncertain material properties and missing S H max magnitude estimates needed for a more reliable model calibration. This leads to the conclusion that at this stage the model's reliability depends only on the amount and quality of available stress information rather than on the modelling technique itself or on local details of the model geometry. Any improvements in modelling and increases in model reliability can only be achieved using more high-quality data for calibration.

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Analysis of induced seismicity in geothermal reservoirs – An overview

Cited by 209 publications

References 113 publications

The Northwest Geysers EGS Demonstration Project, California

The Northwest Geysers EGS Demonstration Project, California

Discrete element modeling of fluid injection–induced seismicity and activation of nearby fault

A multi-stage 3-D stress field modelling approach exemplified in the Bavarian Molasse Basin

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