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Fluid injection-induced seismicity recorded by the seismic network. Geothermal Explorers Ltd. (GEL) recorded earthquakes (gray bars, detected seismic events; red bars, located seismic events) that correlate with the temporal evolution of the well head pressure (blue line, recorded by GEL) over a period of 13 days, beginning on 2 December 2006 when water first was injected into the enhanced geothermal system (EGS) injection well. Earthquake magnitudes (red dots, M L , determined by Swiss Seismological Service) exhibit an increase over time, with highest magnitudes occurring shortly after the largest well head pressures were reached. Original color image appears at the back of this volume.
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With the global challenge to satisfy an increasing demand for energy while at the same time stabilizing or reducing carbon dioxide (CO2) concentrations in the atmosphere, geothermal energy from enhanced geothermal systems (EGSs) increasingly is being recognized as an attractive alternative energy source throughout the world. However, the risks asso...
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Citations
... 19,[30][31][32] The main challenge is to develop adequate permeability in the reservoir while retaining sufficient heat transfer area and keeping the magnitude of induced seismicity as low as possible during reservoir stimulation. 22,33,34 Understanding the governing processes is of utmost importance to improve, and ultimately standardize, the applicability of EGS shear stimulation. 35 Although the process of shear stimulation is theoretically well understood and routinely modeled, fundamental investigations through laboratory tests and field measurements have been limited. ...
... The resulting data that were collected from the Basel project led to many studies on a broad range of topics. 20,22,24,[35][36][37][38][39][40] ...
... Exploiting deep geothermal reservoirs changes the original stress state prevailing in the subsurface. Observations and analyses show that these perturbations can induce seismicity, not only in so-called enhanced geothermal systems, but also in hydrothermal systems driven by a porous matrix (Kraft et al. 2009;Seithel et al., 2019;De Santis et al. 2022). This applies also to low-seismic-hazard environments such as the Munich area. ...
To accelerate the energy transition, the exploitation of deep geothermal reservoirs is becoming a priority to supply district heating networks in areas with high potential for geothermal applications. However, the sustainable development of the resource exploitation implies minimizing the associated risks, in particular related to induced seismicity, while optimizing operational processes. Besides, the growth of this energy sector, often supported by financial aid programs, provides resources to the industry that were not available in the past to implement advanced monitoring strategies. In this context, we present a monitoring system establishing Distributed Acoustic Sensing (DAS) as an effective component of the seismic network used for the monitoring of the geothermal field of Schäftlarnstraße (Munich, Germany). We also investigate its potential for real-time seismic monitoring in an urban environment and for risk mitigation. The monitoring system is based on a data management system linking the on-site acquisition infrastructure, including the fiber optic cable deployed in an injection well and the associated DAS interrogator, to a cloud Internet-of-Things (IoT) platform. The latter is designed to deliver both a secure storage environment for the DAS recordings and optimized computing resources for their processing. The proposed solution has been tested over a six-month period under operating conditions of the geothermal field. The survey proves the feasibility of efficiently acquiring and processing the large flow of continuous DAS data. The processing outcomes, emphasized by two detected local seismic events, demonstrate the suitability of DAS, cemented behind the casing of a flowing well, for (micro-) seismic monitoring of the geothermal site. The processing applied to the data takes advantage of the high spatial density of the acquisitions for their de-noising and for the detection of events. We find that the DAS monitoring system is capable of successfully detecting an event that could not be detected by the standard surface or shallow-borehole 3C-seismometers, despite noisy conditions associated with the urban environment and the field operation. The six-month test period demonstrates the potential of DAS to be integrated as a routine seismic monitoring component of an operating geothermal field. In addition, it highlights its advantageous role as a complement to surface seismometer-based networks, particularly in urban environments
... Usually, various solvents are added to enhance the performance of fracturing fluid, which causes certain pollution to the environment and groundwater (Middleton et al. 2015). The hot dry rock reservoir is dense in nature, with extremely high fracturing pressure (Kraft et al. 2009), and excessive pumping pressure can easily induce earthquakes (Majer et al. 2007;Zhou et al. 2018c). Therefore, how to protect the environment and effectively stimulate the fracture network of hot dry rock while reducing the fracturing pressure and the risk of inducing earthquake is an important problem that needs to be solved urgently. ...
Supercritical carbon dioxide (ScCO2) fracturing to transform geothermal reservoirs is a new technology in geothermal development, with great prospects. In this paper, the current laboratory test methods and test results of ScCO2 fracturing granite are reviewed, and the breakdown pressure and fracture parameters are discussed, and the existing problems and suggestions are given. The results show that the breakdown pressure of ScCO2 is 19.26–26.99% lower than that of water. The breakdown pressure is positively correlated with confining pressure and injection flow rate, and negatively correlated with temperature. ScCO2 tends to form shear fractures, induce more fracture branches and more complex fracture morphology than other fracturing fluids. Compared with water, the density of fracture branches increased by 17.82–60.54%, and the complexity of fracture morphology increased by about 4%. Existing studies have shown that ScCO2 has the advantages of low breakdown pressure, good fracture formation effect, no pollution and water resource saving. It is suggested that further research should be carried out regarding fracturing fluid properties, laboratory tests, theoretical derivation and engineering application in the future, to accelerate the application process of ScCO2 in deep geothermal development.
... According to the results, it has been determined that the noise level in the well is very low compared to the surface and this is at a suitable level for microseismic monitoring networks. [3][4][5] gibi teknik yöntemlerle geliştirilmiş jeotermal sistemler (Enhanced Geothermal System-EGS) olarak adlandırılan jeotermal sistemlere dönüştürülebilmektedir [6,7]. ...
Bu çalışma, Türkiye’de hali hazırda elektrik üretimi yapan jeotermal bir sahada, üretim ve re-enjeksiyon kuyuları sebebiyle oluşacak uyarılmış sismisiteyi izlemek üzere sahaya kurulması planlanan mikrosismik ağın özelliklerini ve kurulum aşamalarını kapsamaktadır. Çalışmada uygulaması yapılan bu ve benzer jeotermal sahalarda, optimum mikrosismik izleme ağı kurulumunun nasıl olması gerektiği, kurulum çalışmaları ve istasyon konumlarına ilişkin gürültü analizleri ile ilgili sonuçlar verilmiştir. 7 adet kuyu tipi sismometre 65 metre derinliğinde açılmış kuyulara yerleştirilerek, sahaya ilişkin mikrosismik kayıtlar elde edilmiştir. Arazi ekipmanlarının başında SARA-SS10BHV marka üç-bileşenli (3C) kuyu tipi kısa periyotlu hız sismometreleri gelmekte olup, analog veri 24-bit SL06 marka kayıtçılar ile sayısallaştırılmıştır. Veri analizlerinde pasif sismik kayıtlar içerisinde yüksek frekanslı, düşük enerjili ve küçük genlikli mikrosismik olaylar ile ilgilenilmiştir. Bu nedenle ağ kurulumunun en önemli basamağını gürültü analizleri oluşturmuştur. Gürültü analizi çalışmalarında, mikrosismik ağ istasyonlarının yerleştirileceği konumlarda arka alan gürültüsü hem yüzey hem de kuyu içerisinden yapılan ölçümlerle belirlenmiş ve sonuçlar birbirleri karşılaştırılmıştır. Bunu sonuçlara göre kuyu içerisindeki gürültü seviyesinin yüzeye oranla çok düştüğü ve bunun mikrosismik izleme ağları için uygun bir düzeyde olduğu belirlenmiştir.
... For more background on poroelasticity, we refer to the example of reservoir engineering where oil and gas reservoirs, as well as more sustainable energy resources like geothermal reservoirs, are subject of research [2,3,42]. This includes the problem of induced seismicity caused by the injection or extraction of fluids in the subsurface of the earth, leading to anthropogenic earthquakes [37,25]. Further references on poroelasticity in earthquake engineering are [15,41,17]. ...
Biot's equations of poroelasticity contain a parabolic system for the evolution of the pressure, which is coupled with a quasi-stationary equation for the stress tensor. Thus, it is natural to extend the existing work on isogeometric space-time methods to this more advanced framework of a partial differential-algebraic equation (PDAE). A space-time approach based on finite elements has already been introduced. But we present a new weak formulation in space and time that is appropriate for an isogeometric discretization and analyze the convergence properties. Our approach is based on a single variational problem and hence differs from the iterative space-time schemes considered so far. Further, it enables high-order convergence. Numerical experiments that have been carried out confirm the theoretical findings.
... Other types of geo-energy projects using the deep underground have been experiencing similar challenges around the globe, such as fracking-related waste-water disposal in the eastern United States, fracking-induced earthquakes in the United Kingdom, and western Canada, ground-water-extraction-related induced earthquakes in Spain, or gasreservoir depletion-related earthquakes in the Netherlands. Managing induced seismicity has thus increasingly become one of the most pressing challenges for geothermal and other geo-energy applications that alter the stress and pore-pressure conditions in the underground (Kraft et al., 2009;Giardini, 2009;Zoback et al., 2012;Ellsworth, 2013;Grigoli et al., 2017). ...
... As a consequence of the ML3.4 earthquake induced during the 2006 Basel EGS project (with claimed damages over 6 million CHF), it is now universally accepted that the future development of geothermal systems near urban areas critically depends on the ability to assess and mitigate the nuisance and potential seismic risk posed by induced seismicity (Giardini, 2009;Kraft et al., 2009;Mena et al., 2013;Mignan et al., 2015). However, induced seismicity risk management is currently a substantial scientific challenge because not enough reliable and validated methods and tools exist to assess and monitor the risk (e.g., Giardini, 2009;Majer et al., 2012). ...
The Swiss Seismological Service at ETH Zurich (SED, www.seismo.ethz.ch) wants to contribute to the sustainable and safe use of deep geothermal energy with this report on good-practice on monitoring, assessment and management of induced seismicity related to the exploitation of deep geothermal energy. The report is aimed at a range of audiences:
– field operators,
– regulators at the local, cantonal or federal level,
– insurance companies looking to assess the financial risk,
– as well as media and the general public that wish to be informed on the topic.
The report builds on the wide range of knowledge and experience that the SED has collected in the past years through participation in the monitoring as well as in the hazard and risk assessment for several deep geothermal projects in Switzerland (e.g., Basel (2006-today), Zurich (2010-2011), St. Gallen (2013-today, Figure 2), Schlattingen (2013-2015), Geneva (2016-today)). In this context, the GEOBEST-CH 2 project, funded by EnergieSchweiz3 (Swiss Federal Office of Energy (SFOE)),instrumental in gaining experience in seismic monitoring and induced-seismic hazard and risk assessment. The report also builds on the ongoing research at the SED and at the Swiss Competence
Center for Energy Research – Supply of Electricity (SCCER-SoE) 4. It benefits from the research and discussions with colleagues from other countries, such as during the Schatzalp workshops on induced seismicity in Davos in March of 20155, March 2017 6, and March 20197. We also profit in many parts from the TA Swiss study ‘Energy from the Earth’ (Hirschberg et al., 2015), where the SED was a major contributor.
... J. Lee et al., 2020). Nucléés à des profondeurs très faibles (Klose, 2010), ces séismes ont des impacts socio-économiques disproportionnellement élevés car ils sont généralement situés proche de zones urbanisées, dans des régions continentales stables, qui concentrent 90 % d'une population mondiale souvent peu préparée à endiguer un séisme destructeur (Kraft et al., 2009 Chaque société est donc confrontée à un double-défi. Le premier est de comprendre les risques sismiques auxquels elle est confrontée pour en atténuer les effets, et donc de décider du niveau de sécurité à atteindre. ...
La compréhension des mécanismes qui gouvernent l'occurrence et la distribution de la sismicité faible à modérée des régions continentales stables est entravée par les capacités limitées des algorithmes utilisés à détecter les petits séismes dans des environnements anthropisés, malgré le déploiement intensif des réseaux de stations. Cette thèse développe une procédure de détection automatique des séismes de faible magnitude à travers SeisComP3 et le Calcul de Haute Performance. Cette nouvelle procédure réduit la contamination des séismes détectés par du bruit sismique en tenant compte des niveaux de bruit enregistré aux stations, de la géométrie du réseau de stations et du milieu de propagation des ondes sismiques. En incorporant un algorithme d’apprentissage machine supervisé, elle discrimine efficacement les séismes détectés, des tirs de carrière et des faux événements associés à du bruit. Les résultats sont prometteurs : 50% de séismes de magnitude inférieure à 1.2 sont détectés en plus. Ce travail vise à une plus large exploration de l’apprentissage machine dans les observatoires sismologiques.
... Un événement de magnitude Mw 3.4 est survenu quelques heures plus tard (Häring et al., 2008 ;), conduisant à la fermeture définitive de la centrale géothermique suite aux plaintes des riverains. Trois autres événements de magnitude supérieure à 3 ont eu lieu au cours des deux mois après la fin de l'injection (Kraft et al., 2009 (Zoback & Harjes, 1997). La distribution spatio-temporelle de la sismicité semble suivre une loi de diffusion (Shapiro et al., 1997). ...
... De plus, il serait intéressant de valider les comportements mécaniques et sismogéniques mis en évidence dans le chapitre 5 à partir de la modélisation de cas réels. Par exemple, la section 5.5 présente diverses hypothèses pour empêcher le déclenchement d'événements sismiques de forte magnitude après l'arrêt de l'injection (par exemple, arrêter l'injection avant que la sismicité atteigne le front de pression) qu'il serait intéressant de tester sur des cas réels présentant également de la sismicité post-injection, tels que l'exploitation géothermique de Bâle en Suisse ou le champ gazier Castor en Espagne (Häring et al., 2008 ;Kraft et al., 2009 ;Cesca et al., 2014 ;Ruiz-Barajas et al., 2017). ...
Les variations de pression de fluide lors d’une injection hydraulique dans une faille affectent la stabilité de la faille. Ainsi, elles peuvent engendrer du glissement sismique et asismique sur la faille. Cependant, les relations entre la pression de fluide, le glissement asismique et la sismicité sont encore mal comprises. Dans cette thèse, j’ai exploré, avec des modélisations 3D sismo-hydro-mécaniques, les mécanismes régissant la déformation sismique et asismique d’une faille perméable gouvernée par une loi de friction « slip-weakening » lors d’une injection ponctuelle. L’objectif principal de ce travail est de mieux comprendre comment une faille répond à une injection de fluide, et aussi d’identifier les propriétés des failles qui contrôlent les comportements sismiques et asismiques observés dans des expériences in-situ et lors de manipulations de fluides en profondeur dans des réservoirs géologiques. Le modèle permet de tester différents états de contraintes sur la faille, et aussi de tester l’influence de différents paramètres hydromécaniques (perméabilité initiale, angle de dilatance) et frictionnels (chute de friction, distance caractéristique de glissement) sur la réponse hydromécanique de la faille. Un glissement asismique de forme elliptique, croissant au cours de l’injection, est observé dans les différentes simulations. Les contraintes cisaillantes s’accumulent au bord de ce patch asismique, ce qui induit des événements sismiques. Dans cette série de simulations, la sismicité suit le front de glissement asismique plutôt que le front de diffusion de pression. La déformation relâchée au cours d’une simulation est majoritairement asismique, avec un moment sismique inférieur à 5% du moment total, conformément aux observations sismologiques acquises lors d’expérience in situ (Guglielmi et al., 2015a; De Barros et al., 2018). Les résultats des modèles montrent aussi que le moment sismique augmente principalement avec une augmentation de la proximité initiale des contraintes à la rupture de la faille et avec la chute de friction, mais aussi, d’une moindre manière, avec une diminution de la perméabilité et de la distance caractéristique de glissement. Modifier la valeur de ces quatre paramètres ne permet pas de reproduire les relations classiques du moment et du volume de fluide injecté (McGarr & Barbour, 2018 ; Galis et al., 2017). Les variations de la b-value avec ces quatre paramètres suivent une relation semi-logarithmique avec la partition sismique du moment. De plus, l’état de contrainte avant l’injection ainsi que la durée de l’injection influent sur la magnitude maximale observée après l’arrêt de l’injection. Ces résultats montrent des caractéristiques observées lors d’expériences d’injection in-situ dans des réservoirs à échelle décamétrique et kilométrique. Ainsi, ces résultats peuvent contribuer à mieux comprendre et anticiper le risque sismique lors d’une injection de fluide en profondeur.
... Awareness and concern regarding the impacts of seismicity induced by hydraulic fracturing have grown significantly in recent years (e.g Ellsworth, 2013; Davies et al., 2013;Cotton et al., 2014;Whitmarsh et al., 2015;Williams et al., 2017;Atkinson et al., 2020), which may pose a threat to the future development of unconventional gas resources (Kraft et al., 2009). There is evidence that tolerance of such operations will be increased if the public is made aware of the potential consequences of the resulting ground shaking (Giardini, 2009;Bommer et al., 2015). ...
We propose a novel framework for assessing the risk associated with seismicity induced by hydraulic fracturing, which has been a notable source of
recent public concern. The framework combines statistical forecast models for injection-induced seismicity, ground motion prediction equations, and
exposure models for affected areas, to quantitatively link the volume of fluid injected during operations with the potential for nuisance felt
ground motions. Such (relatively small) motions are expected to be more aligned with the public tolerance threshold for induced seismicity than
larger ground shaking that could cause structural damage. This proactive type of framework, which facilitates control of the injection volume ahead
of time for risk mitigation, has significant advantages over reactive-type magnitude and ground-motion-based systems typically used for induced
seismicity management. The framework is applied to the region surrounding the Preston New Road shale gas site in North West England. A notable
finding is that the calculations are particularly sensitive to assumptions of the seismicity forecast model used, i.e. whether it limits the
cumulative seismic moment released for a given volume or assumes seismicity is consistent with the Gutenberg–Richter distribution for tectonic
events. Finally, we discuss how the framework can be used to inform relevant policy.
