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Strasbourg, France

Baujard C.,GEOWATT AG | Schoenball M.,Karlsruhe Institute of Technology | Kohl T.,Karlsruhe Institute of Technology | Dorbath L.,EOST

The occurrence of induced seismicity during reservoir stimulation requires robust real-time monitoring and forecasting methods for risk mitigation. We propose to derive an estimation of Mmax (here defined as the largest single seismic event occurring during or after reservoir stimulation) using hydraulic energy as a proxy to forecast the total induced seismic moment and to model the transient evolution of the seismic moment distribution (based on the Gutenberg-Richter relation). The study is applied to the vast dataset assembled at the European pilot research project at Soultz-sous-Forêts (Alsace, France), where four major hydraulic stimulations were conducted at 5km depth. Although the model could reproduce the transient evolution trend of Mmax for every dataset, detailed results show different agreement with the observations from well to well. This might reveal the importance of mechanical and geological conditions that may show strong local variations in the same EGS. © 2014 Elsevier Ltd. Source

Ordonez A.,EOST | Sollner W.,PGS
75th European Association of Geoscientists and Engineers Conference and Exhibition 2013 Incorporating SPE EUROPEC 2013: Changing Frontiers

The imaging condition needs special attention in imaging of separated wavefields because of the increased complexity of the source wavefield. Starting from reciprocity relations and using pressure-normalized wavefield decomposition, we introduce a new deconvolution imaging condition in which the subsurface image is determined from the upgoing pressure and the downgoing vertical particle velocity wavefields. In a recent work, Lameloise et al. (2012) elaborated on migration of separated wavefields using dual-sensor towed streamer data of a simultaneous source system. This work was the starting point to set up a feasibility study and test the new imaging condition. Synthetic and real data examples showed that this approach leads to a better match between the depth images of multiples and primaries. Copyright © (2012) by the European Association of Geoscientists & Engineers All rights reserved. Source

Magnenet V.,CNRS Computer Science and Engineering Laboratory | Fond C.,CNRS Computer Science and Engineering Laboratory | Genter A.,British Petroleum | Schmittbuhl J.,EOST
Geothermal Energy

Background: A two-dimensional numerical model is developed for the Soultz-sous-Forêts reservoir from an idealized cross-section containing six homogeneous horizontal layers. The considered constitutive equations are those of homogenized saturated porous media involving Thermo-Hydro-Mechanical (THM) couplings, and most of materials properties (for brine and rocks) are taken dependent on temperature and pressure. Methods: The constitutive equations are solved in transient regime with the finite element software Code_Aster to reach a stationary state of the reservoir. Results: We show that a large scale natural convection is compatible with present boundary conditions if the permeability of the reservoir is of the order of 1.0×10−14m2. Convection cells are of the order of 1.3 km in width and we analyze several vertical profiles and maps of physical properties. Conclusions: A stationary convective solution at large scale is highlighted. © 2014, Magnenet et al.; licensee Springer. Source

Albaric J.,NORSAR | Calo M.,EOST | Husen S.,ETH Zurich | Oye V.,NORSAR | Maupin V.,University of Oslo
Sustainable Earth Sciences, SES 2013: Technologies for Sustainable Use of the Deep Sub-Surface

We performed a series of tests for passive seismic tomography with data from Paralana, a new Enhanced Geothermal System (EGS) located in South Australia. An injection well was drilled at Paralana in 2009 into a sedimentary basin down to a high heat-producing basement at ~4000 m depth. The first main hydraulic stimulation of the well took place in July 2011 in order to create/enhance a geothermal reservoir. Induced seismicity was monitored by a network of 20 stations (from surface to 1800 m depth) and more than 7000 microearthquakes were detected during the five days of injection. The synthetic tests indicate that small velocity heterogeneities into the reservoir can be resolved at Paralana if high-precision relative arrival times are used, such as provided by waveform-cross correlation. Preliminary results indicate a low P-wave velocity anomaly at the base of the well. Source

Tatevossian R.E.,Russian Academy of Sciences | Aptekman Z.Y.,Russian Academy of Sciences | Dorbath C.,EOST | Vakarchuk R.N.,Russian Academy of Sciences | Tatevossian T.N.,Russian Academy of Sciences
Izvestiya, Physics of the Solid Earth

Relationship between the intensity of seismic shaking on the surface and the velocity structure of the medium at large depth is studied. The Spitak earthquake of December 7, 1988 is chosen as an object of study. A method to correlate the intensity of shaking in the localities to the geophysical parameters specified in the nodes of regular spatial grid is proposed. Formalized definition of anomalous intensity is suggested; it takes into account the distribution of distances from the localities with given intensity degrees to the hypocenter or to the nearest segment of the surface fault. It is found that the seismic wave velocities at a depth of 1 km are higher (up to 0.2-0.6 km/s) under the localities with anomalously high intensity. No any certain regularity is found in deeper layers. © 2011 Pleiades Publishing, Ltd. Source

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