Subsalt imaging using prestack depth migration of converted waves: Mahogany Field, Gulf of Mexico

Kendall, Robert; Gray, Sam; Murphy, Gary E.

doi:10.1190/1.1820355

Cited by 12 publications

(9 citation statements)

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“…Nicolétis et al, 1998) and anisotropic (e.g., Riste and Fjellanger, 2000) materials. Depth migration of P-S data can be accomplished (Kendall et al, 1998;Hoffe and Lines, 1999), which, in addition to possibly better imaging, creates P-P and P-S sections sharing the same depth axis (as opposed to raw P-P and P-S time axes). The use of positive and negative source-receiver offsets can help with improved velocity analysis and imaging (Dai et al, 2000).…”

Section: P-s Data Processingmentioning

confidence: 99%

Converted‐wave seismic exploration: Methods

Gaiser²,

et al. 2002

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Multicomponent seismic recording (measurement with vertical-and horizontal-component geophones and possibly a hydrophone or microphone) captures the seismic wavefield more completely than conventional single-element techniques. In the last several years, multicomponent surveying has developed rapidly, allowing creation of converted-wave or P-S images. These make use of downgoing P-waves that convert on reflection at their deepest point of penetration to upcoming S-waves. Survey design for acquiring P-S data is similar to that for P-waves, but must take into account subsurface V P /V S values and the asymmetric P-S ray path. P-S surveys use conventional sources, but require several times more recording channels per receiving location. Some special processes for P-S analysis include anisotropic rotations, S-wave receiver statics, asymmetric and anisotropic binning, nonhyperbolic velocity analysis and NMO correction, P-S to P-P time transformation, P-S dip moveout, prestack migration with two velocities and wavefields, and stacking velocity and reflectivity inversion for S-wave velocities.Current P-S sections are approaching (and in some cases exceeding) the quality of conventional P-P seismic data. Interpretation of P-S sections uses full elastic ray tracing, synthetic seismograms, correlation with P-wave sections, and depth migration. Development of the P-S method has taken about 20 years, but has now become commercially viable.

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Section: P-s Data Processingmentioning

confidence: 99%

Converted‐wave seismic exploration: Methods

Gaiser²,

et al. 2002

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“…Many authors, including Nicoletis et al (1998); Kendall et al (1998); Dai et al (2000), investigate methods for time or depth migration using converted-wave data. The migration procedures for PP and PS data do not differ in nature, and both include two basic steps: the reconstruction of source and receiver wavefields at all locations in the subsurface and the application of an imaging condition to extract reflectivity from the reconstructed wavefields.…”

Section: Introductionmentioning

confidence: 99%

Analysis of converted‐wave extended images for migration velocity analysis

Jia

Sava

2010

SEG Technical Program Expanded Abstracts 2010

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Converted-wave data have been recognized to have potential in complementing conventional compressional data. However, imaging for converted-waves is more difficult mainly due to the need for estimating shear-wave velocities, in addition to compressional-wave velocities. The common practice is to obtain the shear-wave velocity by registering PS and PP images. Despite its low cost, this procedure is prone to error due to the assumption of imaging simple structure and due to the high potential for cycle skipping. On the other hand, we could obtain S velocities by adapting wave-equation migration velocity analysis (MVA) tools for shear waves. Our assumption is that we can update the S velocities while keeping the known P velocity fixed. We assume that the P-wave velocity is known from MVA of the PP component of the data, then we estimate the S-wave velocity from MVA on the PS component of the data. If P-and S-wave velocities are all correctly estimated, corresponding PP and PS events match in the migrated depth sections. This velocity analysis can make use of both common image gathers (CIGs) and common image point gathers (CIPs). We derive the moveout function for CIPs of converted-wave images and find that they present more complicated moveout than their pure-mode counterparts. We explore the applicability of differential semblance optimization (DSO) to the PP and PS gathers (CIPs and CIGs) to obtain objective functions, based which we can construct optimal velocity models. We find that the objective functions for both PP and PS data are convex, which warrants their use for migration velocity analysis using efficient gradient-descent numerical optimization schemes.

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“…1990; Granli et al . 1995; Kendall, Gray and Murphy 1998). This process can be tedious and very costly.…”

Section: Introductionmentioning

confidence: 99%

“…An initial v P /v S depth variant ratio is then estimated keeping the best available ratio at each depth. The ratio profile is then fine tuned by using event correlation (Tessmer et al 1990;Granli et al 1995;Kendall, Gray and Murphy 1998). This process can be tedious and very costly.…”

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confidence: 99%

Using refracted shear waves for velocity estimation

Pautet¹,

Kuperman²,

Dorman³

2001

Geophysical Prospecting

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The most difficult part of multicomponent processing is the estimation of the shear‐wave velocity map for migration. We used refracted shear waves and a simple iterative method called wavefield continuation (WFC) to evaluate the shallow shear‐wave velocity profile on a real data example. The WFC was developed in 1981 by Clayton and McMechan to determine compressional‐wave velocity profiles from refracted compressional waves. The application to refracted shear waves is straightforward. The real data example shows that shear structure can be easily determined independently of the compressional structure.

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Subsalt imaging using prestack depth migration of converted waves: Mahogany Field, Gulf of Mexico

Cited by 12 publications

References 0 publications

Converted‐wave seismic exploration: Methods

Converted‐wave seismic exploration: Methods

Analysis of converted‐wave extended images for migration velocity analysis

Using refracted shear waves for velocity estimation

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