Amplitude-Preserving Monte Carlo 3D Prestack Migration

Cazzola, Luca; Arienti, M.T.; Bonomi, Ernesto; Cardone, Giovanni

doi:10.3997/2214-4609-pdb.5.b009

Cited by 2 publications

(1 citation statement)

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“…The deconvolution-type imaging condition scale the amplitudes through a correlation, using a weight function dependent on the illumination field. In data with a single shot and receivers covering the whole velocity field, there are two illumination-field weighting possibilities (Schleicher, Costa & Novais, 2008) and its equivalence has been proved (Cazzola, Arienti, Bonomi & Cardone, 2002;Shin, Jang & Min, 2001;Valenciano & Biondi, 2003;Vivas, Pestana & Bjorn, 2009). In shot-profile migration each shot is migrated separately and the images of all shots are stacked to produce the final migrated image.…”

Section: Introductionmentioning

confidence: 99%

Deconvolution-type imaging condition effects on shot-profile migration amplitudes

Vivas-Mejía

González-Alvarez

Jaimes-Osorio³

et al. 2012

CT&F Cienc. Tecnol. Futuro

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Amplitude preservation in Pre-Stack Depth Migration (PSDM) processes that use wavefield extrapolation must be ensured – first, in the operators used to continue the wavefield in time or depth, and second, in the imaging condition used to estimate the reflectivity function. In the later point, the conventional correlation-type imaging condition must be replaced by a deconvolution-type imaging condition. Migration performed in common-shot profile domain obtains the final migrated image as the superposition of images resulting of migrate each shot separately. The amplitude obtained in a point of the migrated image corresponds to the sum of the reflectivities for each shot which has illuminated such point, along the angles determined by the velocity model and the positions of the source and the receiver. The deeper the reflector, the lower the amplitude of the illumination field will be. As result, the correlation-type imaging condition produces images with an unbalanced amplitude decrease with depth. A deconvolution-type imaging condition scales the amplitudes through a correlation, using the weighting function dependent on the spectral density or the illumination of the downgoing wave field. In this article, two possible scaling functions have been used in the case of a single shot. In the case of data with multiple shots, five scaling possibilities are presented with the spectral density or the illumination function. The results of applying these imaging conditions to synthetic data with multiple shots show that the values of the amplitude in the migrated images are influenced by the coverage of the common midpoint, compensating this effect only in one of the imaging conditions described. Numerical experiments with synthetic data generated using Seismic Unix and the Sigsbee2a data are presented, highlighting that in velocity fields with strong vertical and lateral velocity variations, the balance of the amplitudes of the deep reflectors relative to the shallow reflectors is strongly influenced by the imaging condition applied.

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Section: Introductionmentioning

confidence: 99%

Deconvolution-type imaging condition effects on shot-profile migration amplitudes

Vivas-Mejía

González-Alvarez

Jaimes-Osorio³

et al. 2012

CT&F Cienc. Tecnol. Futuro

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Shot-profile true amplitude crosscorrelation imaging condition

et al. 2013

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The U/D imaging condition for shot profile migration can be used to estimate the angle dependent reflection coefficient, but is difficult to implement numerically because of the spectral division involved. Most techniques for stabilizing the division require a damping factor which might be difficult to estimate and which also introduces bias into the final result. A stable result can be achieved by approximating the imaging condition with a crosscorrelation of the up-and downgoing wavefields at zero time lag, but this will lead to incorrect amplitudeversus-angle (AVA) behavior of the estimated reflection coefficient. We use a simple model for wave propagation of primary reflections in the wavenumber frequency domain and invert the model with respect to the reflection coefficient. By using the properties of wavefield extrapolators it can then be shown that the reflection coefficients can be estimated by crosscorrelation of the upgoing wavefield and a downgoing wavefield where the initial wavefield is the inverse of the wavefield generated by a point source. The new imaging condition gives the correct AVA behavior for horizontal reflectors. For dipping reflectors it is shown that a postmigration correction factor can be used to recover the correct angle behavior of the reflection coefficient. The new imaging condition is numerically stable, does not involve damping factors, is simple to implement numerically, and is a simple modification of the classical crosscorrelation imaging condition. Numerical examples confirm the correct AVA behavior of the new imaging condition.

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Amplitude-Preserving Monte Carlo 3D Prestack Migration

Cited by 2 publications

References 0 publications

Deconvolution-type imaging condition effects on shot-profile migration amplitudes

Deconvolution-type imaging condition effects on shot-profile migration amplitudes

Shot-profile true amplitude crosscorrelation imaging condition

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