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EAGE/DGG Workshop on Microseismic Monitoring
- Conference date: March 14, 2014
- Location: Karlsruhe, Germany
- Published: 14 March 2014
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Optimizing Microseismic Monitoring Networks in Densely Populated Areas
By T KraftSummaryWe have developed an optimization algorithm for seismic monitoring networks in urban areas that allows to design and evaluate seismic network geometries for arbitrary geotechnical operation layouts. The algorithm is based on the optimization on the simulated annealing approach proposed by Hardt & Scherbaum (1994) , which aims to minimize the volume of the error ellipsoid of the linearized earthquake location problem (D-criterion). We have extended their algorithm to:
- calculate traveltimes of seismic body waves using a finite difference ray tracer and the 3-D velocity model
- calculate seismic body-wave amplitudes at arbitrary stations assuming the Brune source model and using scaling and attenuation relations recently derived for Switzerland, and
- estimate the noise level at arbitrary locations within Switzerland using a first-order ambient seismic noise model based on 14 land-use classes defined by the EU-project CORINE and open GIS data.
We use the Bayesian Magnitude of Completeness (BMC) method introduced by Mignan et al.(2011) to estimate the expected magnitude of completeness (Mc) level for the optimal network.
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Quantifying and Understanding the Uncertainty Associated with Microseismic Event Locations
By A. JupeSummaryIn this presentation we consider the causes, effects and mitigation of uncertainty in microseismic event location and interpretation. We will firstly discuss how random observational uncertainty and systematic errors can affect the microseismic event location process. We then consider how this uncertainty may propagate into higher level interpretations such as SRV estimation, which is considered an important measure of stimulation effectiveness. Finally we consider what steps can be made to reduce uncertainty with microseismic data sets.
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Passive Seismic Monitoring Concepts - The Role Of Imaging Conditions And Source Mechanisms
Authors O. Zhebel, D. Gajewski and C. VanelleSummaryLocalization of seismic events can provide us valuable information about structures activated by tectonic stresses, geothermal or volcanic activity, reservoir stimulation, and other subsurface activities. In the last few years automatic stacking-based localization methods, which do not require any picking, have proved to be reliable localization tools. Localization results obtained by such techniques are influenced by various circumstances. Influence of two key factors is illustrated in this work such as imaging conditions and source mechanisms. First, a commonly used imaging condition is discussed and alternatives are introduced. I also illustrate their advantages and limitations. Furthermore, localization of events with two different source mechanisms is shown. The first considered source type is a so-called compensated linear vector dipole source, which is typical for geothermal and volcanic areas. As the most seismic events can be best characterized by a combination of explosive, double-couple (DC) and compensated linear vector dipole (CLVD) components, localization of such a source mechanism is also presented.
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Improved Reservoir Characterization - The Use of Waveform Similarities
Authors J. Wassermann and T. MegiesSummaryThe monitoring of microseismicity has already proven to be a very important tool to assess the quality of a geothermal or hydorcarbon reservoir or to estimate the risk of larger, to be felt, earthquakes in the vicinity of geothermal wells or in natural tectonic settings. We will show in this paper, how the use of waveform similarity, i.e. the cross-correlation functions, in a cloud of microearthquakes can improve the precision of the earthquake location procedure as well as helps to characterize physical changes in the reservoir or in the geologic formation. While most of the applied techniques are rather established, the combination and interpretation of the results are still an open field of new research topics.
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Seismic Real-Time Monitoring of a Massive Hydraulic Stimulation of a Geothermal Reservoir in the Cooper Basin, Australia
Authors S. Baisch and A. McMahonSummaryGeodynamics Limited has been developing an Enhanced Geothermal System (EGS) at Habanero in the Cooper Basin, Australia, since 2003.
In November 2012, a large hydraulic stimulation was carried out in the Habanero field. The intent of the stimulation was to expand the existing EGS geothermal reservoir. Over 34 ML of water was injected into the existing “Main Fracture” at a depth of 4,077 m total vertical depth (TVD) over a three week period.
During stimulation, seven seismic stations were used to transfer data in real time to the central processing office with an additional 17 stations recording in an offline mode and incorporated into the workflow in post-processing. In this three week stimulation period, over 27,000 events were recorded, of which over 20,700 events in the magnitude range of ML −1.6 and 3 were located in real time. Hypocenter locations indicate that seismicity occurred on the same sub-horizontal layer structure identified in previous stimulations.
With peak seismicity rates of approx. 2,700 events per day, highly automatized processing played a decisive role. The seismic monitoring campaign is a unique showcase for successful and reliable real-time processing and traffic-light system operation at extremely high seismicity rates.
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Automated Micro-earthquake Location
By V. OyeSummaryThis presentation provides an overview on automatic location methods for various microseismic applications, and hence largely variable receiver networks. We will focus on the use of migration-based methods as an alternative to phase identification, especially in cases of large receiver networks with poor signal-to-noise ratio datasets.
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Improving Sensitivity of Earthquake Measurements by Nanoseismic Monitoring
Authors B. Sick, P. Blascheck and M. JoswigSummaryNanoseismic Monitoring acts as a seismic microscope tuned for the recording and analysis of very low-SNR microseismic events. The method benefits from three principal ideas: (I) better noise conditions by flexible surface station deployments independent from infrastructure (II) improved detection capabilities by array correlation and advanced spectrogram visualization and (III) interactive event localization to handle uncertain phase readings. The performance of the approach is demonstrated by two examples from Switzerland. The complementary surveillance of the Basel deep heat mining project allows for comparison to the monitoring results of borehole stations which define Ground Truth. The observation of the Mont Terri underground rock laboratory unveils previously unknown recent tectonics close to the lab.
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Effective Detection Capability of a Local Seismic Network
By E. GaucherSummaryIn applications such as geothermal energy, underground storage, mining, hydraulic fracturing, it becomes current practice to implement local seismic networks to monitor induced seismicity and to help mitigating the associated risks. In such contexts, it is crucial to guarantee that the network is able to detect a seismic event of predefined magnitude in a specific area. We propose a method to estimate this detection capability for existing kilometric-scale seismic networks which did not record any seismicity in the target zone yet.
However, the network should be running for a time period long enough to record several local events listed in a reference catalogue. These earthquakes are used to calibrate an amplitude-magnitude relationship, knowing that the amplitudes are at the basis of the detection of seismic event candidates. This observation-based approach can take into account uncertainties in the magnitude estimate.
The procedure was applied on the seismic network deployed over Bruchsal (Germany) geothermal field. Since mid-2010, no seismicity in the reservoir has been recorded by the network despite its good working order. The proposed technique suggests that there is 95% probability that no seismic event with ML ≥ 0.7 occurred below the network down to the reservoir depth at 2400 m.
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Probabilistic Seismic Hazard Analysis for Induced Seismicity
Authors D.A. Kraaijpoel, M. Caccavale, T. van Eck and B. DostSummaryProbabilistic Seismic Hazard Analysis is currently the most common approach to seismic hazard analysis. For application to induced seismicity, a major challenge is the fact that the hazard is inherently nonstationary. In this paper we describe the theoretical extension of PSHA to a non-stationary context. We identify three major challenges of non-stationary PSHA: (1) the determination of the seismicity rate as a function of time,
(2) the definition of the earthquake probability density functions for space and magnitude, and (3) the construction or selection of an appropriate ground motion prediction equation. We show some examples from our work in progress at the Groningen field.
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Towards a Risk Governance Framework for Induced Seismicity
By S. WiemerSummaryIt is a well established fact that man-made perturbations to the critically stressed crust, e.g. through reservoir stimulation, hydraulic fracking, mining, reservoir impoundment, injection of waste water, and CO2 storage leads to enhanced seismic activity. While the size of such induced seismic events is typically smaller than the largest observed natural events in the same location, they are governed by the same physics, and are often indistinguishable from natural events.
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Microseismic Monitoring of the northern Upper Rhine Graben - The projects SiMoN and FERRY
Authors B. Homuth, M. Lindenfeld, G. Rümpker, H. Winter and M. KrachtSummaryMonitoring of natural and induced seismicity.
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Hydroacoustic Monitoring of the La Valette Landslide
Authors M. Boubacar, S. Bernardie, F. Lebert, G. Grandjean and J.P. MaletSummaryLandslide failures may seriously damage the human and environmental resources of a region. However, it is still uneasy to forecast the evolution of a landslide because it depends both on its dynamics and on external triggering events, such as earthquakes and rainfall (Guzzetti et al. 2007). To better understand these processes, passive seismic monitoring techniques have been developed since the 1960s, in order to detect possible seismic signals triggered by the slope dynamics (Cadman & Goodman 1967; Novosad et al. 1977). It consists generally in identifying seismic sources induced by the slope movement using seismic sensors. This work focuses on the characterisation of seismic sources observed in at La Valette landslide (South French Alps) which is representative of landslides developped in clays. Hydro-acoustic devices installed permanently in boreholes since October 2012 are used to detect seismic events and relate their occurence to environmental factors (rain, groundwater level variations) and to the surface displacement of the landslide.
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