Subsalt imaging: The RAZ–WAZ experience

Kapoor, Jerry; Moldevaneau, Nick; Egan, Mark S.; O’Briain, Michael; Desta, Dawit; Atakishiyev, Iigar; Tomida, Michiru; Stewart, Elizabeth

doi:10.1190/1.2805764

Cited by 24 publications

(5 citation statements)

References 5 publications

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“…The success of seismic exploration surveys in hydrocarbon provinces influenced by salt tectonics often depends on the ability to accurately image sub‐salt target zones (Kapoor et al . ). However, accurate and clear imaging of sub‐salt structures can be challenging for multiple reasons.…”

Section: Introductionmentioning

confidence: 97%

Source wavelet correction for practical Marchenko imaging: A sub‐salt field‐data example from the Gulf of Mexico

Mildner

Broggini

Filho

et al. 2019

Geophysical Prospecting

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Imaging a target zone below a salt body can be challenging because large velocity contrasts in the overburden between the salt and surrounding sediments generate internal multiples, which interfere with primary reflections from the target level in the imaging process. This can lead to an erroneous interpretation of reflections in the sub‐salt area if multiples are misinterpreted as primaries. The Marchenko redatuming method may enable imaging of the sub‐salt target area where the effect of the multiply‐scattering overburden is removed. This is achieved by creating a redatumed reflection response where virtual sources and receivers are located below the overburden using a macromodel of the velocity field and the surface reflection data. The accuracy of the redatumed data and the associated internal multiple removal, however, depends on the accurate knowledge of the source wavelet of the acquired reflection data. For the first time, we propose a method which can accurately and reliably correct the amplitudes of the reflection response in field data as required by the Marchenko method. Our method operates by iteratively and automatically updating the source function so as to cancel the most artefact energy in the focusing functions, which are also generated by the Marchenko method. We demonstrate the method on a synthetic dataset and successfully apply it to a field dataset acquired in a deep‐water salt environment in the Gulf of Mexico. After the successful source wavelet estimation for the field dataset, we create sub‐salt target‐oriented images with Marchenko redatumed data. Marchenko images using the proposed source wavelet estimation show clear improvements, such as increased continuity of reflectors, compared to surface‐based images and to conventional Marchenko images computed without the inverted source wavelet. Our improvements are corroborated by evidence in the literature and our own synthetic results.

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Section: Introductionmentioning

confidence: 97%

Source wavelet correction for practical Marchenko imaging: A sub‐salt field‐data example from the Gulf of Mexico

Mildner

Broggini

Filho

et al. 2019

Geophysical Prospecting

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“…A target-oriented strategy using a data set obtained by generalized Born modeling based on a single scattering approximation to the full wave equation can use wavefield-based velocity estimation to focus on improving velocities in subsalt regions (Tang and Biondi, 2011). In addition, others focus effort on investigating the impact of acquisition geometries on subsalt imaging (Kapoor et al, 2007;VerWest and Lin, 2007;Burch et al, 2010;Zhu et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Staining algorithm for seismic modeling and migration

Chen

Jia

2014

GEOPHYSICS

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In seismic migration, some structures such as those in subsalt shadow zones are not imaged well. The signal in these areas may be even weaker than the artifacts elsewhere. We evaluated a method to significantly improve the signalto-noise ratio (S/N) in poorly illuminated areas of the model. We constructed a "phantom" wavefield: an extension of the wavefield to the complex domain. The imaginary wavefield was synchronized with the real wavefield, but it contained only the events relevant to a target region of the model, which was specified using a staining algorithm. The real wavefield interacted with the entire model. However, all structures except for the target were transparent to the imaginary wavefield, which is excited only when the real wavefront arrives at the target structure. The real and the imaginary source wavefields were crosscorrelated with the regular receiver wavefield. The results were revealed in two images: the conventional reverse time migration image and an image of the target region only. Synthetic experiments showed that the S/N of the target structures was improved significantly, with other structures effectively muted.

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“…In recent years, we have seen great advances in imaging technology, which, together with new wide-azimuth acquisition, have resulted in greatly enhanced images in even the most complex structural settings (Kapoor et al, 2007). RTM has clearly emerged as the algorithm of choice for such complex areas.…”

Section: Introductionmentioning

confidence: 99%

Improved subsalt imaging and salt interpretation by RTM scenario testing and image partitioning

O’Briain¹,

Smith²,

Montoya

et al. 2013

SEG Technical Program Expanded Abstracts 2013

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Advances in acquisition and processing technology help overcome imaging challenges in complex structural settings. The widespread adoption of wide-azimuth (WAZ) and the move towards full-azimuth (FAZ) acquisition geometries, both combined with increasing offsets, result in significantly improved illumination. Reduced compute cost and improved performance enabled reverse time migration (RTM) to emerge as the imaging algorithm of choice in such settings. Of course, an accurate velocity model is a key component in realizing the full potential of these acquisition geometries and algorithms. The trend is towards increasingly more complex anisotropic models, with a move from vertical transverse isotropy (VTI) to tilted transverse isotropy (TTI) and even orthorhombic. In the Gulf of Mexico (GoM), though the importance of defining an accurate anisotropic model in the supra-salt section cannot be understated, the largest contributing factor to a good image subsalt is often the correct delineation of the "salt body" itself. Without an accurate definition of the salt geometry, the subsalt image invariably remains distorted and poorly resolved. In this paper, we will focus on this portion of the depth imaging workflow and illustrate how the techniques of RTM scenario testing and image partitioning can be used in combination to both help define the salt geometry and improve the final post-migration image. We will describe a practical workflow and the key components that we feel are necessary for its success. In addition, we will illustrate a number of lessons learned during the course of recent projects executed in the GoM.

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Subsalt imaging: The RAZ–WAZ experience

Cited by 24 publications

References 5 publications

Source wavelet correction for practical Marchenko imaging: A sub‐salt field‐data example from the Gulf of Mexico

Source wavelet correction for practical Marchenko imaging: A sub‐salt field‐data example from the Gulf of Mexico

Staining algorithm for seismic modeling and migration

Improved subsalt imaging and salt interpretation by RTM scenario testing and image partitioning

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