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77th EAGE Conference and Exhibition - Workshops
- Conference date: June 1-4, 2015
- Location: Madrid, Spain
- Published: 01 June 2015
121 - 128 of 128 results
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Estimating the Location of a Tunnel Using Interferometric Times of Rayleigh-wave Scattering
Authors A. Kaslilar, U. Harmankaya, K. Wapenaar and D. DraganovSummaryInspired by a technique called seismic interferometry, we estimate the location of a scatterer using scattered waves. We isolate the scattered wavefield and evaluate the result of correlating scattered waves at different receiver locations. The cross-correlation eliminates the travel path between a source and a scatterer, making the estimation of the scatterers’ locations dependent only on properties between the receivers and the scatterer. We illustrate the potential of this method by locating a tunnel from seismic field data, recorded along a line with multiple source and receiver locations. As near-surface scatterers are potential weak zones and may pose risk for the environment, to mitigate geo- and environmental hazards, this method can be an efficient alternative in detection of such structures.
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Feasibility Study of Seismic Interferometry for CO2 Storage Monitoring - An Example from the Ketzin Site
More LessSummarySeismic interferometry is a relatively low cost method compared with conventional seismic monitoring methods and can be performed together with microseismic and reservoir monitoring. These features make it a new potential tool for carbon dioxide storage monitoring. In this study, we acquired 6 nights of ambient noise data were recorded at the Ketzin experimental CO2 injection Site located in Ketzin, west of Berlin, Germany, in August 2013. An active survey was also acquired at the same time along of one line for a source test. Passive seismic interferometry was applied to the recorded noise data to reconstruct common shot gathers. The virtual shot gathers was processed to obtain a stacked section. The results show that the passive stacked sections are less coherent and low resolution compared with the active stacked section. However, we could also find some similar features to both the passive and active stacked sections in the shallow parts and even some agreement in the deeper parts.
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Feasibility of Retrieving Time-lapse Reflection Signals Using Ambient-noise Seismic Interferometry at Ketzin, Germany
Authors B. Boullenger, A. Verdel, B. Paap, J. Thorbecke and D. DraganovSummaryAmbient-noise seismic interferometry (ANSI) applied to passive body-wave measurements retrieves an estimate of the reflection response as if from a source at a receiver position. Often, the limited compliance with theoretical assumptions causes erroneous absolute amplitudes of the retrieved physical reflections, and additional artefacts. Nevertheless, the retrieved reflection data may be further used for time-lapse interpretation, since the latter exploits relative amplitude differences. Here, we study the feasibility of applying ANSI to time-lapse passive seismic data to extract the time-lapse reflection signal produced by the exploitation of a reservoir. We base our study on the case of the demonstration site for CO2 storage at Ketzin, Germany. With numerical experiments, we apply ANSI to two passive datasets using a base and a repeat scenario (after velocity decreases in the CO2 reservoir) and modelled by random distributions of band-limited noise sources. We show that the retrieval of an unambiguous time-lapse signal is enabled by increased common illumination between the two datasets. Finally, we apply ANSI by auto-correlation to Ketzin field data and show the retrieval of responses consistent with modelled and active field data. We conclude that ANSI applied to field data has the potential for time-lapse differences extraction and interpretation.
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A Study on the Effect of Least-squares Datuming on VSP Multiple Imaging
Authors A. Aldawood, I. Hoteit, G. Turkiyyah and T. AlkhalifahSummaryInterferometric transformations are widely applied to transform seismic data from one acquisition geometry to another. We used a correlation-type interferometric transformation to redatum vertical-seismic-profiling surface-related multiples into surface-seismic virtual primaries. Conventional redatuming, based on the cross-correlation of seismic traces, yields virtual surface-seismic records that suffer from correlation artefacts, wavelet distortion, and low-temporal resolution. These effects are mainly caused by the limited recording aperture, the band-limited nature of the source wavelet, and the coarse source-receiver sampling. Least-squares migration of the virtual surface-seismic gathers can partially enhance the seismic resolution of the final migrated sections. However, our results demonstrate that the least-squares datuming step remarkably helps suppress the cross-correlation artefacts, enhance the resolution of the seismic events, and properly deconvolve the source wavelet. Therefore, the computed migrated sections suggest that least-squares datuming can be an essential processing step to apply to VSP surface-related multiples prior to imaging subsurface structures.
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A Review of Tangent-phase Interferometry Method and Applications
Authors F. Poletto, B. Farina and G. BöhmSummarySeismic interferometry makes it possible to reconstruct redatumed signals creating virtual sources at receivers. The conventional method utilizes the crosscorrelation of recorded signals from a plurality of sources to estimate the Green’s function between receivers. Great advantages are to remove the propagation effects outside the representation zone, and redatum signals without the need of velocity model. The seismic interferometry method requires an appropriate and complete distribution of seismic sources around the receivers for signal representation with stationary conditions. Lack of coverage may results in ghost and artefacts. However, the condition to have only partial coverage by sources is common. Recently, a method was proposed to overcome these limitations and to extend the stationary conditions for selected events. The tangent-phase interferometry (TPI) corrects the phase in the cross-correlations before integral representation. This approach requires identification of the signal trends for selected events in the cross correlations, and corresponds to move the virtual source from receiver positions to projected points on the signal wavefronts. We present a review of TPI applications, with the analysis of emerging aspects in different examples. This review is aimed at evaluating advantages and critical issues in the joint use of TPI with other inversion and imaging methods.
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Use of Seismic Interferometry to Improve the Imaging of a Heterogeneous Landfill
Authors L.A. Konstantaki, D. Draganov, R. Ghose and T. HeimovaaraSummaryIn this study we investigate the application of seismic interferometry (SI) to seismic reflection data recorded over a landfill. Landfills represent strongly heterogeneous subsurfaces making the seismic reflection imaging challenging. We show that SI improves the imaging of high-density areas, which create scattering events in the recorded data. In addition, we use SI to subsequently predict surface-wave energy and remove it from the original data to improve the imaging of reflectors. The combined interpretation of the conventional reflection seismic data, SI and reflection data with surface waves removed improves the understanding of the landfill body.
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Scatterer Characterization from Correlated Surface Wave Coda
Authors T.E. Blum, T.D. Mikesell, K. van Wijk, R. Snieder and H. SatoSummaryThe accuracy of scattered Rayleigh waves estimated using an interferometric method is investigated. Summing the cross correlations of the wave fields measured all around the scatterers yields the Green's function between two excitation points. This accounts for the direct wave and the scattered field (coda). The correlations themselves provide insights into the location of the scatterers as well as which scatterer is responsible for particular parts of the coda.
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Analysis of Rayleigh Wave Ellipticity in the Iberian Peninsula and Morocco Using Ambient Noise and Teleseismic Records
Authors C. Gómez-García, A. Villaseñor, A. Ugalde and B. GaiteSummaryWe combine Rayleigh wave ellipticity, or H/V (horizontal to vertical) amplitude ratios, measurements obtained using teleseismic earthquake recordings and ambient noise cross correlations to provide improved constraints on the crustal models across the Iberian Peninsula and Morocco. To obtain the H/V ratios, we use more than 250 shallow (h<40 km) teleseismic events with magnitudes Mw>6.0 recorded atmore than 450 seismic stations. We also use all the multicomponent ambient noise cross correlations computed for each station pair for the time period 2010 to 2012. Periods between 20 and 100 seconds are investigated. We observe a good agreement between the uppermost geological features of the crust and the obtained Rayleigh H/V ratios, with low values in major mountain ranges and high ratios in sedimentary basins. Combination of Rayleigh H/V ratio measurements from both earthquakes and ambient noise data with phase velocities and other types of seismic data will help to better constrain the Earth’s structure at different crustal levels.
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