Advances in velocity model-building technology for subsalt imaging

Wang, Bin; Kim, Young; Mason, Chuck; Zeng, Xiansong

doi:10.1190/1.2966096

Cited by 34 publications

(14 citation statements)

References 33 publications

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“…By using our subsalt scan picking tool, delayed imaging times are picked by comparing scan panels (stacked images) as well as gather displays. This method is similar to wave-equation migration scan picking (Wang et al, 2008). After the DIT-scan subsalt velocity update, RTM is rerun by using the newly updated velocity model.…”

Section: Composite Rtm Image-based Dit-scan Pickingmentioning

confidence: 99%

Enhanced prestack depth imaging of wide-azimuth data from the Gulf of Mexico: A case history

Ma¹,

Wang²,

Reta-Tang³

et al. 2011

GEOPHYSICS

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We present a case study of enhanced imaging of wideazimuth data from the Gulf of Mexico utilizing recent technologies; and we discuss the resulting improvements in image quality, especially in subsalt areas, relative to previous results. The input seismic data sets are taken from many large-scale wide-azimuth surveys and conventional narrowazimuth surveys located in the Mississippi Canyon and Atwater Valley areas. In the course of developing the enhanced wide azimuth processing flow, the following three key steps are found to have the most impact on improving subsalt imaging: (1) 3D true azimuth surface-related multiple elimination (SRME) to remove multiple energy, in particular, complex multiples beneath salt; (2) reverse-time migration (RTM) based delayed imaging time (DIT) scans to update the complex subsalt velocity model; and (3) tilted transverse isotropic (TTI) RTM to improve image quality. Our research focuses on the depth imaging aspects of the project, with particular emphasis on the application of the DIT scanning technique. The DIT-scan technique further improves the accuracy of the subsalt velocity model after conventional ray-based subsalt tomography has been performed. We also demonstrate the uplift obtained by acquiring a wide-azimuth data set relative to a standard narrow-azimuth data set, and how orthogonal wide-azimuth is able to enhance the subsalt illumination.

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Section: Composite Rtm Image-based Dit-scan Pickingmentioning

confidence: 99%

Enhanced prestack depth imaging of wide-azimuth data from the Gulf of Mexico: A case history

Ma¹,

Wang²,

Reta-Tang³

et al. 2011

GEOPHYSICS

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“…Liu et al (2011) modify conventional RTM and use the multiples as constructive energy for imaging. Velocity model building plays an important role to enhance the subsalt visibility and resolution (Fliedner et al, 2007;Wang et al, 2008;Ji et al, 2011). 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).…”

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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“…Salt boundary interpretation is important for studying salt tectonics (Hudec et al, 2011;Jackson and Hudec, 2016) and for velocitymodel building in seismic migration (Wang et al, 2008;Leveille et al, 2011). Interpreting salt boundaries often involves computing a salt attribute image and picking salt boundaries from the attribute image.…”

Section: Introductionmentioning

confidence: 99%

Fast salt-boundary interpretation with optimal path picking

Fomel

Hudec

2017

SEG Technical Program Expanded Abstracts 2017

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Salt boundary interpretation is a crucial step for velocitymodel building in seismic migration, but it remains a highly labor-intensive task for manual interpretation and a big challenge for automatic methods. We have developed a semiautomatic method to efficiently and accurately extract 2D and 3D complicated salt boundaries from a seismic attribute image that highlights salt boundaries. In 2D salt boundary extraction, we first pick a few points to interpolate an initial curve that is close to the true salt boundary. These points are picked near the salt boundary but are not required to be exactly on the boundary, which makes human interactions convenient and efficient. We then resample the salt boundary attribute image in a band area centered at the initial curve to obtain a new image in which the true salt boundary is an open curve extending laterally. We then extract the salt boundary in the new image using an optimal-path picking algorithm, which is robust enough to track a stable salt boundary from highly discontinuous attribute values by solving a global maximization problem. We finally map the picked path back to the original image to obtain a final salt boundary. In 3D salt boundary extraction, we apply the 2D method to recursively pick 2D salt boundaries in a sequence of inline or crossline slices and then use these 2D boundaries to fit an implicit (level-set) surface of the 3D salt boundary. In our recursive picking, human interactions are greatly reduced by using a salt boundary picked in the previous slice as an initial curve for picking in a followed slice. The effectiveness of our method is confirmed with 2D and 3D real seismic images.

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Advances in velocity model-building technology for subsalt imaging

Cited by 34 publications

References 33 publications

Enhanced prestack depth imaging of wide-azimuth data from the Gulf of Mexico: A case history

Enhanced prestack depth imaging of wide-azimuth data from the Gulf of Mexico: A case history

Staining algorithm for seismic modeling and migration

Fast salt-boundary interpretation with optimal path picking

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