Elastic P- and S-wave autofocus imaging with primaries and internal multiples

Filho, Carlos Alberto da Costa; Ravasi, Matteo; Curtis, Andrew

doi:10.1190/geo2014-0512.1

Cited by 40 publications

(20 citation statements)

References 69 publications

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“…a direct wave) in the imaging condition eliminates some crosstalk between source-side wavefields and unrelated events in the receiver-side wavefield (Wapenaar et al 1987;da Costa Filho et al 2015).…”

Section: Imaging Methodsmentioning

confidence: 99%

Imaging strategies using focusing functions with applications to a North Sea field

Filho

Meles

Curtis

et al. 2017

Geophysical Journal International

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SUMMARYSeismic methods are used in a wide variety of contexts to investigate subsurface Earth structures, and to explore and monitor resources and waste-storage reservoirs in the upper~100 km of the Earth's subsurface. Reverse-time migration (RTM) is one widely used seismic method which constructs high-frequency images of subsurface structures. Unfortunately, RTM has certain disadvantages shared with other conventional single-scattering-based methods, such as not being able to correctly migrate multiply-scattered arrivals. In principle, the recently-developed Marchenko methods can be used to migrate all orders of multiples correctly. In practice however, using Marchenko methods are costlier to compute than RTM-for a single imaging location, the cost of performing the Marchenko method is several times that of standard RTM, and performing RTM itself requires dedicated use of some of the largest computers in the world for individual datasets. A different imaging strategy is therefore required. We propose a new set of imaging methods which use so-called focusing functions to obtain images with few artifacts from multiply-scattered waves, while greatly reducing the number of points across the image at which the Marchenko method need be applied. Focusing functions are outputs of the Marchenko scheme: they are solutions of wave equations that focus in time and space at particular surface or subsurface locations. However, they are mathematical rather than phys-2 da Costa Filho et. al ical entities, being defined only in reference media that equal to the true Earth above their focusing depths but are homogeneous below. Here, we use these focusing functions as virtual source/receiver surface seismic surveys, the upgoing focusing function being the virtual received wavefield that is created when the downgoing focusing function acts as a spatially distributed source. These source/receiver wavefields are used in three imaging schemes: one allows specific individual reflectors to be selected and imaged. The other two schemes provide either targeted or complete images with distinct advantages over current reverse-time migration methods, such as fewer artifacts and artifacts that occur in different locations. The latter property allows the recently published "combined imaging" method to remove almost all artifacts. We show several examples to demonstrate the methods: acoustic 1D and 2D synthetic examples, and a 2D line from an ocean bottom cable (OBC) field dataset. We discuss an extension to elastic media, which is illustrated by a 1.5D elastic synthetic example.

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Section: Imaging Methodsmentioning

confidence: 99%

Imaging strategies using focusing functions with applications to a North Sea field

Filho

Meles

Curtis

et al. 2017

Geophysical Journal International

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“…Marchenko inverse scattering may also be used to predict and remove internal multiples in acoustic and elastic (da Costa Filho et al, forthcoming) data. Imaging methods that use wavefields from the Marchenko methods have been referred to as data-driven wavefield imaging , autofocus imaging (Behura et al, 2014;da Costa Filho et al, 2015), and Marchenko imaging .…”

Section: Introductionmentioning

confidence: 99%

Attenuating multiple-related imaging artifacts using combined imaging conditions

Filho

Curtis

2016

GEOPHYSICS

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The objective of prestack depth migration is to position reflectors at their correct subsurface locations. However, migration methods often also generate artifacts along with physical reflectors, which hamper interpretation. These spurious reflectors often appear at different spatial locations in the image depending on which migration method is used. Therefore, we have devised a postimaging filter that combines two imaging conditions to preserve their similarities and to attenuate their differences. The imaging filter is based on combining the two constituent images and their envelopes that were obtained from the complex vertical traces of the images. We have used the method to combine two images resulting from different migration schemes, which produce dissimilar artifacts: a conventional migration method (equivalent to reverse time migration) and a deconvolution-based imaging method. We show how this combination may be exploited to attenuate migration artifacts in a final image. A synthetic model containing a syncline and stochastically generated small-scale heterogeneities in the velocity and density distributions was used for the numerical example. We compared the images in detail at two locations where spurious events arose and also at a true reflector. We found that the combined imaging condition has significantly fewer artifacts than either constituent image individually.

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“…Alternatively, we can estimate the required Green's functions directly from the reflection data that are acquired at the earth's surface by solving a multidimensional Marchenko equation (Broggini et al, 2012;Slob et al, 2014;Wapenaar et al, 2014;da Costa Filho et al, 2015;Singh et al, 2015). Internal multiples are effectively accounted for by this methodology even though it only requires a smooth subsurface model (Behura et al, 2014;Broggini et al, 2014;Mildner et al, 2017).…”

Section: Motivationmentioning

confidence: 99%

Target-enclosed seismic imaging

et al. 2017

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Seismic reflection data can be redatumed to a specified boundary in the subsurface by solving an inverse (or multidimensional deconvolution) problem. The redatumed data can be interpreted as an extended image of the subsurface at the redatuming boundary, depending on the subsurface offset and time. We retrieve target-enclosed extended images by using two redatuming boundaries, which are selected above and below a specified target volume. As input, we require the upgoing and downgoing wavefields at both redatuming boundaries due to impulsive sources at the earth’s surface. These wavefields can be obtained from actual measurements in the subsurface, they can be numerically modeled, or they can be retrieved by solving a multidimensional Marchenko equation. As output, we retrieved virtual reflection and transmission responses as if sources and receivers were located at the two target-enclosing boundaries. These data contain all orders of reflections inside the target volume but exclude all interactions with the part of the medium outside this volume. The retrieved reflection responses can be used to image the target volume from above or from below. We found that the images from above and below are similar (given that the Marchenko equation is used for wavefield retrieval). If a model with sharp boundaries in the target volume is available, the redatumed data can also be used for two-sided imaging, where the retrieved reflection and transmission responses are exploited. Because multiple reflections are used by this strategy, seismic resolution can be improved significantly. Because target-enclosed extended images are independent on the part of the medium outside the target volume, our methodology is also beneficial to reduce the computational burden of localized inversion, which can now be applied inside the target volume only, without suffering from interactions with other parts of the medium.

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Elastic P- and S-wave autofocus imaging with primaries and internal multiples

Cited by 40 publications

References 69 publications

Imaging strategies using focusing functions with applications to a North Sea field

Imaging strategies using focusing functions with applications to a North Sea field

Attenuating multiple-related imaging artifacts using combined imaging conditions

Target-enclosed seismic imaging

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