• Tunnel and Underground Space
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• v.23 no.6
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• pp.581-592
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• 2013

This article provides an overview on the geothermal energy research in Europe and one of the EU funded projects 'GEISER (Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs)' in which the authors were involved. More details are given for description of GEISER, in particular, about aims and discussions and how the project was managed. Emphasis is given to one of the work packages 'Induced Seismicity and Large Magnitude Events (LME)' and results of this work package are summarized. This article intends to summarize the lessons learned in the GEISER project and give recommendations to future geothermal projects by creating Enhanced Geothermal Systems hydraulic stimulation where induced seismicity issues are expected to be a major issue and obstacle.

• Tunnel and Underground Space
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• v.23 no.6
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• pp.493-505
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• 2013

This numerical study investigates seismicity and fault slip induced by fluid injection in deep geothermal reservoir with pre-existing fractures and fault. Particle Flow Code 2D is used with additionally implemented hydro-mechanical coupled fluid flow algorithm and acoustic emission moment tensor inversion algorithm. The output of the model includes spatio-temporal evolution of induced seismicity (hypocenter locations and magnitudes) and fault deformation (failure and slip) in relation to fluid pressure distribution. The model is applied to a case of fluid injection with constant rates changing in three steps using different fluid characters, i.e. the viscosity, and different injection locations. In fractured reservoir, spatio-temporal distribution of the induced seismicity differs significantly depending on the viscosity of the fracturing fluid. In a fractured reservoir, injection of low viscosity fluid results in larger volume of induced seismicity cloud as the fluid can migrate easily to the reservoir and cause large number and magnitude of induced seismicity in the post-shut-in period. In a faulted reservoir, fault deformation (co-seismic failure and aseismic slip) can occur by a small perturbation of fracturing fluid (<0.1 MPa) can be induced when the injection location is set close to the fault. The presented numerical model technique can practically be used in geothermal industry to predict the induced seismicity pattern and magnitude distribution resulting from hydraulic stimulation of geothermal reservoirs prior to actual injection operation.

• Geophysics and Geophysical Exploration
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• v.18 no.1
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• pp.21-30
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• 2015

Induced seismicity has been observed in the relation with lots of anthropogenic influence and at variety of geological conditions over the last several decades. This paper reviews those induced earthquakes and compares with each other as well as with natural tectonic earthquakes. Hydraulic fracturing is commonly used to enhance the permeability through new cracks in the rock formation. The process triggers the induced seismicity, which can give crucial information on the fracture network and oil/gas migration. In the similar way, unintentionally induced events during the production procedure of the field, dam reservoir, minig activity, or wastewater injection can be used to give insight into various hydrodynamic processes and changes of reservoir properties at a various scales. The general conclusion summarizes the uncertainty or limitations of knowledge up to date and presents some issues to be dealt with in the future research.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.385-399
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• 2021

Among human-induced seismicity, fluid production has been one of the causes. In this report, the mechanism that causes an earthquake due to a decrease in the fluid pressure inside the reservoir during fluid extraction is summarized. As case studies, the Lacq gas field in France, the Cerro Prieto geothermal field in Mexico, and the Groningen gas field in the Netherlands, which have become issue recently, were introduced. It is showed that fluid production, ground subsidence, and the presence of existing faults were closely related with the induced seismicity. Therefore, for the development of oil or gas field and geothermal field, it is important to investigate the presence of faults that may cause earthquakes in the reservoir, to monitor ground subsidence during production in real time, and to control production.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.741-748
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• 2006

Seismic performance evaluation was conducted for four wind-designed concentrically braced steel highrise buildings in order to check the feasibility of designing steel highrise buildings per elastic seismic design criterion (or strength and stiffness solution) in the regions of strong wind and moderate seismicity. The pushover analysis results revealed that the wind-designed highrise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind-induced overstrength, highrise buildings with a slenderness ratio of larger than four or five can withstand elastically even the maximum considered earthquake at the performance level of immediate occupancy. Based on the analytical results of this study, practical elastic seismic design procedure for steel highrise buildings in the regions of moderate seismicity is proposed.

• Tunnel and Underground Space
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• v.33 no.1
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• pp.57-69
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• 2023

In this study, we simulated induced seismicity in the Groningen natural gas reservoir using 2D hydro-mechanical coupled discrete element modelling (DEM). The code used is PFC2D (Particle Flow Code 2D), a commercial software developed by Itasca, and in order to apply to this study we further developed 1)initialization of inhomogeneous reservoir pressure distribution, 2)a non-linear pressure-time history boundary condition, 3)local stress field monitoring logic. We generated a 2D reservoir model with a size of 40 × 50 km² and a complex fault system, and simulated years of pressure depletion with a time range between 1960 and 2020. We simulated fault system failure induced by pressure depletion and reproduced the spatiotemporal distribution of induced seismicity and assessed its failure mechanism. Also, we estimated the ground subsidence distribution and confirmed its similarity to the field measurements in the Groningen region. Through this study, we confirm the feasibility of the presented 2D hydro-mechanical coupled DEM in simulating the deformation of a complex fault system by hydro-mechanical coupled processes.

• Tunnel and Underground Space
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• v.24 no.6
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• pp.418-429
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• 2014

Induced seismicity related to four energy development technologies that involve fluid injection or withdrawal: geothermal energy, conventional oil and gas development including enhanced oil recovery (EOR), shale gas recovery, and carbon capture and storage (CCS) is reviewed by literature investigation. The largest induced seismic events reported in the technical literature are associated with projects that did not balance the large volume of fluids injected into, or extracted from the underground reservoir. A statistical observation shows that the net volume of fluid injected and/or extracted may serve as a proxy for changes in subsurface stress conditions and pore pressure, and other factors. Energy technology projects that are designed to maintain a balance between the amount of fluid being injected and the amount of fluid being withdrawn, such as geothermal and most oil and gas development, may produce fewer induced seismic events than technologies that do not maintain fluid balance, such as long-term wastewater disposal wells and CCS projects.

• Tunnel and Underground Space
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• v.32 no.3
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• pp.203-218
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• 2022

A hydro-mechanical study was performed to analyze the relationship between the magnitude of injection-induced seismicity and shut-in. In hydraulic analysis, the suspension of fluid injection makes the pore pressure gradient smaller while the pore pressure at the pressure front can reach the critical value for several hours after shut-in, which leads to the additional slip with wider area than during injection. The hydro-mechanical numerical analysis was performed to model the simplified fault system, and simulated the largest magnitude earthquake during shut-in stage. The effect of the abrupt suspension of fluid injection on the large magnitude earthquake was investigated in comparison with the continuous injection. In addition to the pore pressure distribution, it was found that the geometry of multiple faults and the stress redistribution are also important in evaluating the magnitude of the induced seismicity.

• Earthquakes and Structures
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• v.10 no.6
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• pp.1391-1404
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• 2016

Peninsular Malaysia lying on the stable Sunda Plate has traditionally been considered safe with low to moderate seismicity. However, far field Sumatran mega-earthquakes have been shown to be capable of triggering ground motions felt in high rise structures in the major Malaysian cities while seismic impact from local earthquakes of moment magnitude 3.8 have reportedly induced nominal structural damages to nearby buildings. This paper presents an overview of the recent seismic activities in and around Peninsular Malaysia with reference to prominent earthquakes generated by far field interplate and local intraplate sources. Records of ground motion data and seismic hazard assessment (SHA) results available in the literature have been analyzed and discussed. The peak ground acceleration (PGA) values from historical records for few local intraplate events were observed to be higher than those for the events from Sumatran Subduction Zone. This clearly points to the need for a detailed and comprehensive SHA incorporating both far field and local sources. Such an analysis would contribute the knowledge required for secure and reliable infrastructure design and safeguard the Malaysian people and economy.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.288-295
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• 2000

As the level of earthquake intensity in Korea is considered to be moderate, some structures or structural elements may be subjected to the reduced ductility demand, in contrast to the structures in high seismicity, due to the large inherent strength induced by gravity loads. New Zealand Standard(NZS) deals with these structures within the category of structures of limited ductility. This paper briefly reviews the concept of structures of limited ductility in NZS, and its applicability to Korean case. A structural wall system which is used as the structural system for typical apartments is taken as an example for the illustration.