The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Junzo Kasahara - One of the best experts on this subject based on the ideXlab platform.
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Elastic Full Waveform Inversion With a Permanent Seismic Source ACROSS: Towards Hydrocarbon Reservoir Monitoring
2016Co-Authors: Mamoru Takanashi, Stefan Lüth, Ayato Kato, Junzo Kasahara, Christopher JuhlinAbstract:Time-lapse analysis plays an essential role in EOR (enhanced oil recovery) or CCS (carbon capture and storage) management. However, conventional time-lapse Seismic often cannot capture differential signals from the target interval because of near-surface heterogeneity or poor signal-to-noise (S/N) ratio. We discuss a potential application of a permanent Seismic Source "ACROSS" (Accurately Controlled and Routinely Operated Signal System) that can continuously excite controlled Seismic signals over years. The superior repeatability of ACROSS makes it possible to subtract any waveforms that do not change over time, and hence the temporal changes due to the fluid replacement at the target interval should be enhanced. Also, it is possible to consider reverse time migration or full waveform inversion rather than just the first arrival or P-wave reflection traveltime inversion, since ACROSS precisely controls the Source signature. Both vertical and horizontal single forces are reconstructed by clockwise and counter-clockwise rotations of an asymmetric cylindrical mass. In our synthetic study, we assume that two ACROSS Sources are installed at a CO 2 pilot injection project in Ketzin, Germany. Elastic FWI (full waveform inversion) is tested with the assumption that the medium parameters (i.e., P- and S-wave velocities and density) before the injection are known. To prevent crosstalk caused by interference of P- and S-waves, we apply a wave separation technique by extracting the scalar (P-wave component) and vector potential (S-wave component) of the elastic wavefields. The simulation results demonstrate that this approach clearly delineates the P-wave velocity decrease caused by the fluid injection. The high-repeatability of ACROSS enables an application of elastic FWI for residual P-wave velocity, which may bring a breakthrough toward CO 2 and hydrocarbon reservoir monitoring. Copyright 2014, International Petroleum Technology Conference.
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Towards a new approach for time-lapse Seismic using permanent Seismic Source ACROSS and elastic full waveform inversion
2014Co-Authors: Mamoru Takanashi, Ayato Kato, Junzo KasaharaAbstract:© 2014 SEG. Source repeatability is one of the most important problems in time-lapse Seismic and reservoir monitoring. We introduce a new time-lapse approach using a permanent Seismic Source ACROSS (Accurately Controlled and Routinely Operated Signal System) and elastic full waveform inversion. The ACROSS Source, fixed in cement at surface, can produce repeatable, extremely precise two-component Seismic signal. We first performed field data observation at a Kashiwazaki test field, Niigata, Japan using two ACROSS Sources with sweep frequency ranging between 5-50 Hz. Signals from each ACROSS Source are clearly separated owing to an accurate Source control, and transfer functions (or shot gathers) corresponding to each ACROSS are generated. The waveforms arriving before surface waves, mostly P-wave related, show little waveform changes over time and confirm excellent Source repeatability. With the assumption that two ACROSS Sources are installed at a CCS (carbon capture and storage) field, we performed 2D simulation study using time-lapse elastic full waveform inversion (FWI) for differential P-wave velocity. Since ACROSS precisely controls the sweep Source signature, it is more suitable to apply elastic algorithm than conventional acoustic method. To simplify the multi-component and multiparameter problems on elastic FWI, we invert only for P-wave velocity residual using so-called scalar potential of the elastic wavefields to prevent from crosstalks caused by P- and S-wave interference. The synthetic FWI result shows sharp delineation of P-wave velocity residual associated with fluid replacement. The superior repeatability of ACROSS and the proposed timelapse FWI approach may bring a breakthrough towards hydrocarbon reservoir or CO2 monitoring.
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real time imaging of co2 storage zone by very accurate stable long term Seismic Source
Energy Procedia, 2013Co-Authors: Junzo Kasahara, Tomohiro Fujiwara, Yoko Hasada, Kayoko Tsuruga, Ryoya Ikuta, Naoyuki Fujii, Koshun Yamaoka, Kinya NishigamiAbstract:Abstract To examine the effectiveness of our time lapse method for CCS monitoring, we carried out a field-test in Japan using an ultra-stable Seismic Source. We injected 80-tons air in total into 100 m depth. We obtained transfer functions between the Source and 31 seismometers. All residual waveforms between before and after the injection revealed very large changes on records. A station at 200m distance from the injected-well showed 10ms travel-time delay at 1-day after the injection. The time-reversal imaging showed the clear image for spreading of disturbed area from the injection point to eastward with elapsed times.
Jeanpaul Montagner - One of the best experts on this subject based on the ideXlab platform.
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time reversal Seismic Source imaging and moment tensor inversion
Geophysical Journal International, 2008Co-Authors: Hitoshi Kawakatsu, Jeanpaul MontagnerAbstract:SUMMARY The time reversal operation in Seismic Source estimation is considered. We show that the time reversal operation, equally the adjoint operation, for Seismic Source imaging gives an approximate solution to more conventional Seismic Source inverse problem through the ‘happy approximation’ underlined by Claerbout. Practical applications of such methods in a longperiod range to monitor earth’s activities in realtime are also discussed.
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Time‐reversal Seismic‐Source imaging and moment‐tensor inversion
Geophysical Journal International, 2008Co-Authors: Hitoshi Kawakatsu, Jeanpaul MontagnerAbstract:SUMMARY The time reversal operation in Seismic Source estimation is considered. We show that the time reversal operation, equally the adjoint operation, for Seismic Source imaging gives an approximate solution to more conventional Seismic Source inverse problem through the ‘happy approximation’ underlined by Claerbout. Practical applications of such methods in a longperiod range to monitor earth’s activities in realtime are also discussed.
Hitoshi Kawakatsu - One of the best experts on this subject based on the ideXlab platform.
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time reversal Seismic Source imaging and moment tensor inversion
Geophysical Journal International, 2008Co-Authors: Hitoshi Kawakatsu, Jeanpaul MontagnerAbstract:SUMMARY The time reversal operation in Seismic Source estimation is considered. We show that the time reversal operation, equally the adjoint operation, for Seismic Source imaging gives an approximate solution to more conventional Seismic Source inverse problem through the ‘happy approximation’ underlined by Claerbout. Practical applications of such methods in a longperiod range to monitor earth’s activities in realtime are also discussed.
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Time‐reversal Seismic‐Source imaging and moment‐tensor inversion
Geophysical Journal International, 2008Co-Authors: Hitoshi Kawakatsu, Jeanpaul MontagnerAbstract:SUMMARY The time reversal operation in Seismic Source estimation is considered. We show that the time reversal operation, equally the adjoint operation, for Seismic Source imaging gives an approximate solution to more conventional Seismic Source inverse problem through the ‘happy approximation’ underlined by Claerbout. Practical applications of such methods in a longperiod range to monitor earth’s activities in realtime are also discussed.
Karin Sigloch - One of the best experts on this subject based on the ideXlab platform.
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fully probabilistic Seismic Source inversion part 1 efficient parameterisation
Solid Earth, 2013Co-Authors: Simon C Stahler, Karin SiglochAbstract:Abstract. Seismic Source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves but also estimates of their uncertainties are of great practical importance. Probabilistic Source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Seismic Source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and Source time function efficiently by using information from previous non-Bayesian inversions. The Source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 Source time functions (STFs) by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the Source parameters, and permits propagating these Source uncertainties into travel time estimates used for Seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and Source time functions from teleSeismic broadband waveforms is feasible.
E Boschi - One of the best experts on this subject based on the ideXlab platform.
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a Seismic Source zone model for the Seismic hazard assessment of the italian territory
Tectonophysics, 2008Co-Authors: C Meletti, F Galadini, Gianluca Valensise, Massimiliano Stucchi, R Basili, S Barba, Gianfranco Vannucci, E BoschiAbstract:Abstract We designed a new Seismic Source model for Italy to be used as an input for country-wide probabilistic Seismic hazard assessment (PSHA) in the frame of the compilation of a new national reference map. We started off by reviewing existing models available for Italy and for other European countries, then discussed the main open issues in the current practice of seismogenic zoning. The new model, termed ZS9, is largely based on data collected in the past 10 years, including historical earthquakes and instrumental Seismicity, active faults and their seismogenic potential, and seismotectonic evidence from recent earthquakes. This information allowed us to propose new interpretations for poorly understood areas where the new data are in conflict with assumptions made in designing the previous and widely used model ZS4. ZS9 is made out of 36 zones where earthquakes with M w > = 5 are expected. It also assumes that earthquakes with M w up to 5 may occur anywhere outside the seismogenic zones, although the associated probability is rather low. Special care was taken to ensure that each zone sampled a large enough number of earthquakes so that we could compute reliable earthquake production rates. Although it was drawn following criteria that are standard practice in PSHA, ZS9 is also innovative in that every zone is characterised also by its mean seismogenic depth (the depth of the crustal volume that will presumably release future earthquakes) and predominant focal mechanism (their most likely rupture mechanism). These properties were determined using instrumental data, and only in a limited number of cases we resorted to geologic constraints and expert judgment to cope with lack of data or conflicting indications. These attributes allow ZS9 to be used with more accurate regionalized depth-dependent attenuation relations, and are ultimately expected to increase significantly the reliability of Seismic hazard estimates.
