Elastic reverse-time migration with OBS multiples

Duan, Yuting; Sava, Paul

doi:10.1190/segam2014-1395.1

Cited by 7 publications

(2 citation statements)

References 19 publications

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“…Such waves produce artifacts in the migrated images, as seen in Figure 2b, 2d, and 2f. Because the artifacts are generally inconsistent with each other between different shots, they are attenuated in stacked images (Duan and Sava, 2014).…”

Section: Theorymentioning

confidence: 99%

Scalar imaging condition for elastic reverse time migration

2015

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Polarity changes in converted-wave images constructed by elastic reverse time migration cause destructive interference after stacking over the experiments of a seismic survey. This polarity reversal is due to PS and SP reflectivities reversing sign at certain incidence angles, e.g., at normal incidence in isotropic media. Many of the available polarity correction methods are complex and require costly transformations, e.g., to the angle domain. We derive a simple imaging condition for converted waves to correct the image polarity and reveal the conversion strength from one wave mode to another. Our imaging condition exploits pure P-and S-modes obtained by Helmholtz decomposition. Instead of correlating Cartesian components of the vector S-mode with the P-mode, we exploit all three components of the S wavefield at once to produce a unique image. We generate PS and SP images using geometric relationships among the propagation directions for the P-and S-wavefields, the reflector orientation, and the S-mode polarization direction. Compared with alternative methods for correcting the polarity reversal of PS and SP images, our imaging condition is simple and robust and does not significantly increase the cost of reverse time migration. Several numerical examples were used to test the effectiveness of our new imaging condition using simple and complex models.

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Section: Theorymentioning

confidence: 99%

Scalar imaging condition for elastic reverse time migration

2015

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“…However, elastic migration suffers from issues that negatively affect the quality of the images. Because it is, in general, difficult to separate all arrivals by wave mode in recorded data, nonphysical modes lead to artifacts (i.e., crosstalk) in the image (Duan and Sava, 2014).…”

Section: Introductionmentioning

confidence: 99%

Elastic least-squares reverse time migration

2017

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Least-squares migration can produce images with improved resolution and reduced migration artifacts, compared with conventional imaging. We have developed a method for elastic least-squares reverse time migration (LSRTM) based on a new perturbation imaging condition that yields scalar images of squared P-and S-velocity perturbations. These perturbation images do not suffer from polarity reversals that are common for more conventional elastic imaging methods. We use 2D synthetic and field-data examples to demonstrate the proposed LSRTM algorithm using the perturbation imaging condition. Our results show that elastic LSRTM improves the energy focusing and illumination of the elastic images and it attenuates artifacts resulting, for instance, from sparseness in the wavefield sampling and crosstalk of the P-and S-modes. Compared with RTM images, the LSRTM images provide more accurate relative amplitude information that is useful for reservoir characterization.

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Isotropic elastic wavefield imaging using the energy norm

2016

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From the elastic-wave equation and the energy conservation principle, we have derived an energy norm that is applicable to imaging with elastic wavefields. Extending the concept of the norm to an inner product enables us to compare two related wavefields. For example, the inner product of source and receiver wavefields at each spatial location leads to an imaging condition. This new imaging condition outputs a single image representing the total reflection energy, and it contains individual terms related to the kinetic and potential energy (strain energy) from both extrapolated wavefields. An advantage of the proposed imaging condition compared with alternatives is that it does not suffer from polarity reversal at normal incidence, as do conventional images obtained using converted waves. Our imaging condition also accounted for the directionality of the wavefields in space and time. Based on this information, we have modified the imaging condition for attenuation of backscattering artifacts in elastic reverse time migration images. We performed numerical experiments that revealed the improved quality of the energy images compared with their conventional counterparts and the effectiveness of the imaging condition in attenuating backscattering artifacts even in media characterized by high spatial variability.

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Elastic reverse-time migration with OBS multiples

Cited by 7 publications

References 19 publications

Scalar imaging condition for elastic reverse time migration

Scalar imaging condition for elastic reverse time migration

Elastic least-squares reverse time migration

Isotropic elastic wavefield imaging using the energy norm

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