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Calibri 83ffff̙̙3f3fff3f3f33333f33333.kTU Delft Repositoryg Wuuidrepository linktitleauthorcontributorpublication yearabstract
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departmentresearch group programmeprojectcoordinates)uuid:85aa81cb4cf048c7a9fc95f6cef248bfDhttp://resolver.tudelft.nl/uuid:85aa81cb4cf048c7a9fc95f6cef248bfeTransmission compensated primary reflection retrieval in the data domain and consequences for imaging"Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft ImPhys/Acoustical Wavefield Imaging; TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics)We have developed a scheme that retrieves primary reflections in the twoway traveltime domain by filtering the data. The data have their own filter that removes internal multiple reflections, whereas the amplitudes of the retrieved primary reflections are compensated for twoway transmission losses. Application of the filter does not require any model information. It consists of convolutions and correlations of the data with itself. A truncation in the time domain is applied after each convolution or correlation. The retrieved data set can be used as the input to construct a better velocity model than the one that would be obtained by working directly with the original data and to construct an enhanced subsurface image. Two 2D numerical examples indicate the effectiveness of the method. We have studied bandwidth limitations by analyzing the effects of a thin layer. The presence of refracted and scattered waves is a known limitation of the method, and we studied it as well. Our analysis indicates that a thin layer is treated as a more complicated reflector, and internal multiple reflections related to the thin layer are properly removed. We found that the presence of refracted and scattered waves generates artifacts in the retrieved data.acoustic; internal multiplesenjournal articleEGreen Open Access added to TU Delft Institutional Repository You share, we take care! Taverne project https://www.openaccess.nl/en/yousharewetakecare Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
20191026)uuid:a6cb1a3123c946f09a52b1f68378d57fDhttp://resolver.tudelft.nl/uuid:a6cb1a3123c946f09a52b1f68378d57f"Timeslice wavefield decompositionHolicki, M.E. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); Drijkoningen, G.G. (TU Delft Applied Geophysics and Petrophysics)2Sicking, Charles (editor); Ferguson, John (editor)We propose a novel acoustic decomposition operator for time slices, loosely based on conventional surface decomposition operators. The proposed operators hold for constant velocity models and require two 2D Fourier Transforms (one forward, one backward) per decomposed time slice per decomposition direction. We then demonstrate the capabilities of our operators on a constant velocity model and the Marmousi model. The decomposition results prove that we can decompose into up, down, left and rightgoing waves for complex velocity media.imaging; internal multiplesconference paperSEG)uuid:e5a476136f6c48a6a81e16430c319586Dhttp://resolver.tudelft.nl/uuid:e5a476136f6c48a6a81e16430c319586=Electromagnetic Marchenko imaging in 1D for dissipative media3Zhang, L. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Staring, M. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)We present a onedimensional lossless scheme to compute an image of a dissipative medium from two singlesided reflection responses. One reflection response is measured at or above the top reflector of a < dissipative medium and the other reflection response is computed as if measured at or above the top reflector of a medium with negative dissipation which we call the effectual medium. These two reflection responses together can be used to construct the approximate reflection data of the corresponding lossless medium by multiplying and taking the square root in time domain. The corresponding lossless medium has the same reflectors as the dissipative medium. Then the constructed reflection data can be used to compute the focusing wavefield which focuses at the chosen location in subsurface of the dissipative medium. From the focusing function and constructed reflection response the Green s function for a virtual receiver can be obtained. Because the up and downgoing parts of the Green s function are retrieved separately, these are used to compute the image. We show with an example that the method works well for a sample in a synthesized waveguide that could be used for measurements in a laboratory.Delectromagnetic; conductivity; internal multiples; permeability; GPR)uuid:55668444877344cea542b28883d3654cDhttp://resolver.tudelft.nl/uuid:55668444877344cea542b28883d3654cRMarchenko wavefield redatuming, imaging conditions, and the effect of model errorsde Ridder, Sjoerd (University of Edinburgh); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Curtis, A (University of Edinburgh); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Recently, a novel method to redatum the wavefield in the subsurface from a reflection response measured at the surface has gained interest for imaging primaries in the presence of strong internal multiples. A prerequisite for the algorithm is an accurate and correct estimate of the directwave Green's function. However, usually we use an estimate for the directwave Green's function computed in a background velocity medium. Here, we investigate the effect of amplitude and phase errors in that estimate. We formulate two novel imaging conditions based on doublefocusing the measured reflection response inside the subsurface. These yield information on the amplitude error in the estimate for the directwave Green's function which we can then correct, but the phase error remains elusive.>inversion; autofocusing; imaging; internal multiples; velocity)uuid:170cc1de39a64906ad7a935382da4232Dhttp://resolver.tudelft.nl/uuid:170cc1de39a64906ad7a935382da4232MNew method for discriminating 4D time shifts in the overburden and reservoirr5Liu, Yi (Norwegian University of Science and Technology); Arntsen, B (Norwegian University of Science and Technology); Landr, M (Norwegian University of Science and Technology); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics)Understanding seismic changes in the subsurface is important for reservoir management and health, safety and environmental (HSE) issues. Typically the changes are interpreted based on the time shifts in seismic timelapse (4D) data, where sources are at the surface and receivers are either at the surface or in a borehole. With these types of acquisition geometry, it is more straightforward to detect and interpret changes in the overburden, close to the source and receivers, than changes in the deeper part close to the reservoir, because the time shift is accumulative along its ray path from source to receiver. We propose a new method for reconstructing the reflection responses of the overburden and the reservoir, separately, for 4D time shift analysis. This method virtually moves sources and receivers to a horizontal borehole level, which enables a more direct interpretation of the time shifts to the changes close to the borehole, instead of to the surface. A realistic field model is used to demonstrate the method, and we observe a clear discrimination of the different time shifts in the overburden and reservoir, which is not obvious in the original datasets.Nreconstruction; timelapse; traveltime; downhole receivers; internal multiples< )uuid:37a5a787e38849f59c22579dee5aa1efDhttp://resolver.tudelft.nl/uuid:37a5a787e38849f59c22579dee5aa1efQFrom closedboundary to singlesided homogeneous Green's function representations,Wapenaar, C.P.A. (TU Delft Applied Geophysics and Petrophysics); van der Neut, J.R. (TU Delft Applied Geophysics and Petrophysics); Thorbecke, J.W. (TU Delft Applied Geophysics and Petrophysics); Slob, E.C. (TU Delft Applied Geophysics and Petrophysics); Singh, Satyan (University of the West Indies)The homogeneous Green s function (i.e., the Green s function and its timereversed counterpart) plays an important role in optical, acoustic and seismic holography, in inverse scattering methods, in the field of timereversal acoustics, in reversetime migration and in seismic interferometry. Starting with the classical closedboundary representation of the homogeneous Green s function, we modify the configuration to two parallel boundaries. We discuss stepbystep a process that eliminates the integral along the lower boundary. This leads to a singlesided representation of the homogeneous Green s function. Apart from imaging, we foresee interesting applications in inverse scattering, timereversal acoustics, seismic interferometry, passive source imaging, etc.)uuid:7b0b9d5d78954d469b03d618bd9734faDhttp://resolver.tudelft.nl/uuid:7b0b9d5d78954d469b03d618bd9734fa>Internal multiple suppression by adaptive Marchenko redatumingFVan der Neut, J.R.; Wapenaar, C.P.A.; Thorbecke, J.W.; Vasconcelos, I.Recently, a novel iterative scheme was proposed to retrieve Green's functions in an unknown medium from its singlesided reflection response and an estimate of the propagation velocity. In Marchenko imaging, these Green's functions are used for seismic imaging with complete wavefields, including internal multiple reflections. In this way, common artifacts from these internal reflections are avoided and illumination of the subsurface can potentially be improved. However, Marchenko imaging requires accurate input data, with correct amplitudes, a deconvolved source signature, without freesurface multiples and source / receiver ghosts. Hence, a significant amount of preprocessing is required, which should be done accurately. To relax these requirements, we propose a scheme to remove artifacts due to internal multiples from inverseextrapolated wavefields, by adaptively subtracting an estimate of these artifacts that is constructed with the Marchenko equation. autofocusing; internal multiples!Civil Engineering and GeosciencesGeoscience & Engineering)uuid:097d4a01a0ae47418bbf023b10226dfbDhttp://resolver.tudelft.nl/uuid:097d4a01a0ae47418bbf023b10226dfbdOn the focusing conditions in timereversed acoustics, seismic interferometry, and Marchenko imagingcWapenaar, C.P.A.; Van der Neut, J.R.; Thorbecke, J.W.; Vasconcelos, I.; Van Manen, D.J.; Ravasi, M.yDespite the close links between the fields of timereversed acoustics, seismic interferometry and Marchenko imaging, a number of subtle differences exist. This paper reviews the various focusing conditions of these methods, the causality/acausality aspects of the corresponding focusing wavefields, and the requirements with respect to omnidirectional/singlesided acquisition.Applied SciencesImPhys/Imaging Physics)uuid:a3762abc0fae4b0bbea6aa571f2db3e2Dhttp://resolver.tudelft.nl/uuid:a3762abc0fae4b0bbea6aa571f2db3e2[Autofocusing imaging: Imaging with primaries, internal multiples and freesurface multiplesTSingh, S.; Snieder, R.; Behura, J.; van der Neut, J.R.; Wapenaar, C.P.A.; Slob, E.C.#Recent work on autofocusing with the Marchenko equation has shown how the Green's function for a virtual source in the subsurface can be obtained from reflection data. The response to the virtual source is the Green's function from the location of the virtual source to the surface. The Green's function is retrieved using only the reflection response of the medium and an estimate of the first arrival at the surface from the virtual source. Current techniques, however, only include primaries and interna<l multiples. Therefore, all surfacerelated multiples must be removed from the reflection response prior to Green's function retrieval. Here, we extend the Marchenko equation to retrieve the Green's function that includes primaries, internal multiples, and freesurface multiples. In other words, we retrieve the Green's function in the presence of a free surface. We use the associated Green's function for imaging the subsurface. The information needed for the retrieval are the reflection response at the surface and an estimate of the first arrival at the surface from the virtual source. The reflection response, in this case, includes the freesurface multiples; this makes it possible to include these multiples in the imaging operator and it obviates the need for surfacerelated multiple elimination.@imaging; multiples; scattering; autofocusing; internal multiples
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