Subsalt illumination analysis using RTM 3D dip gathers

Li, Zhengxue; Tang, Bing; Ji, Shuai

doi:10.1190/segam2012-1348.1

Cited by 12 publications

(3 citation statements)

References 22 publications

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“…As a separate product, RTM 3D dip gathers were used as a specular imaging tool to attenuate noise and enhance the subsalt image. The RTM dip gathers were generated by the directional wavefield decomposition among dip and azimuth angles at each image point (Li et al, 2012;. In dip gathers, each dip-azimuth angle pair represents a possible subsurface structure.…”

Section: Rtm Dip Gathersmentioning

confidence: 99%

Understanding and improving the subsalt image at Thunder Horse, Gulf of Mexico

Hartman¹,

Chakraborty²,

Nolte³

et al. 2015

SEG Technical Program Expanded Abstracts 2015

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Subsalt imaging at the Thunder Horse Field in the Gulf of Mexico is challenging primarily because the salt canopy, overlying roughly 75% of the structure, greatly distorts subsalt illumination and causes imaging and resolution problems. Since the Thunder Horse discovery, advancements in seismic acquisition techniques and imaging technologies have significantly improved subsalt images. The latest successful application is from a tilted transverse isotropy (TTI) reverse time migration (RTM) project combining two wide azimuth towed streamer (WATS) data sets and three narrow azimuth towed streamer (NATS) data sets. The addition of an extra WATS data set and the application of the recent imaging technologies are key contributors to the dramatic structural image improvements with better defined three-way events and a higher signal-to-noise ratio (S/N).

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Section: Rtm Dip Gathersmentioning

confidence: 99%

Understanding and improving the subsalt image at Thunder Horse, Gulf of Mexico

Hartman¹,

Chakraborty²,

Nolte³

et al. 2015

SEG Technical Program Expanded Abstracts 2015

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“…It was developed for prestack one-way wave-equation migration and may be adapted to two-way wave-equation methods as well. There are few other authors that provide techniques for computing dip-angle CIGs based on space-shift extended waveequation migration methods (Browaeys 2008;Li, Tang and Ji 2012;Dafni and Symes 2016a). Another recent publication by Silvestrov, Baina and Landa (2016) involves poststack reversetime migration (RTM) and pseudo-dip-angle decomposition for diffraction imaging.…”

Section: Introductionmentioning

confidence: 99%

Diffraction imaging by prestack reverse‐time migration in the dip‐angle domain

Dafni

Symes

2017

Geophysical Prospecting

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Prestack image volumes may be decomposed into specular and non‐specular parts by filters defined in the dip‐angle domain. For space‐shift extended image volumes, the dip‐angle decomposition is derived via local Radon transform in depth and midpoint coordinates, followed by an averaging over space‐shifts. We propose to employ prestack space‐shift extended reverse‐time migration and dip‐angle decomposition for imaging small‐scale structural elements, considered as seismic diffractors, in models with arbitrary complexity. A suitable design of a specularity filter in the dip‐angle domain rejects the dominant reflectors and enhances diffractors and other non‐specular image content. The filter exploits a clear discrimination in dip between specular reflections and diffractions. The former are stationary at the specular dip, whereas the latter are non‐stationary without a preferred dip direction. While the filtered image volume features other than the diffractor images (for example, noise and truncation artefacts are also present), synthetic and field data examples suggest that diffractors tend to dominate and are readily recognisable. Averaging over space‐shifts in the filter construction makes the reflectors‧ rejection robust against migration velocity errors. Another consequence of the space‐shift extension and its angle‐domain transforms is the possibility of exploring the image in a multiple set of common‐image gathers. The filtered diffractions may be analysed simultaneously in space‐shift, scattering‐angle, and dip‐angle image gathers by means of a single migration job. The deliverables of our method obviously enrich the processed material on the interpreter's desk. We expect them to further supplement our understanding of the Earth's interior.

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“…This is because the separation is based on the relative offset of the source and imaging location, which is only indirectly related to the dip of the subsurface events. Li et al (2012) proposed a PSF-like approach for evaluating and balancing dip-and azimuth-dependent illumination coverage through forward modeling point diffractors followed by RTM with 3D subsurface dip-azimuth gather outputs. Subsurface dip-azimuth RTM gathers (hereafter referred to as RTM 3D dip gathers or simply dip gathers) can accurately map the prestack depth-migration image into different subsurface dip orientations using plane-wave decomposition applied during the imaging condition.…”

Section: Introductionmentioning

confidence: 99%

Revealing subsalt structure using RTM 3D dip gathers

Huang

Lee

et al. 2016

The Leading Edge

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Gulf of Mexico (GoM) subsalt imaging often suffers from poor illumination due to salt-related wavefield distortion, even with full-azimuth (FAZ) acquisition. In order to image the weakly illuminated subsalt plays, isolating the signal from the noise is a crucial component of many depth-imaging practices. Reverse time migration (RTM) subsurface 3D dip-azimuth gathers, which separate seismic data into different dip/azimuth components, are utilized to address illumination problems in structure-oriented imaging. A weighting scheme using RTM 3D dip gathers for image enhancement is proposed; it is based on a priori structure information and targets noise that has conflicting dips with the structure. The sensitivity of the method to the uncertainty of the initial dipping information of the structure is further discussed and evaluated. The method is applied on subsalt structures on both a synthetic data set and a real data set with staggered-acquisition FAZ data. The tests demonstrate the necessity of signal-to-noise ratio enhancement in the imaging of FAZ, long-offset data, and the effectiveness of RTM 3D dip gathers in unmasking poorly illuminated zones.

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Subsalt illumination analysis using RTM 3D dip gathers

Cited by 12 publications

References 22 publications

Understanding and improving the subsalt image at Thunder Horse, Gulf of Mexico

Understanding and improving the subsalt image at Thunder Horse, Gulf of Mexico

Diffraction imaging by prestack reverse‐time migration in the dip‐angle domain

Revealing subsalt structure using RTM 3D dip gathers

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