A comparison of methods for obtaining local image gathers in depth migration

Luo, Min; Lu, Ruqian; Winbow, Graham A.; Bear, Lorie K.

doi:10.1190/1.3513522

Cited by 7 publications

(9 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…" " " " " " " " " " " " Partial comparisons of these methods have been made previously. Luo et al (2010) compared the LPWD FT implementation and the LSIC SS implementation, using the parts of Sigsbee2A data set. Xu et al (2011) compared ADCIGs obtained by an LPWD implemented by FT, and those obtained by an LSIC method, using the whole Sigsbee2A data set.…”

Section: " "mentioning

confidence: 99%

Comparison of methods for extracting ADCIGs from RTM

McMechan

Guan

2014

GEOPHYSICS

View full text Add to dashboard Cite

Methods for extracting angle-domain common-image gathers (ADCIGs) during 2D reverse-time migration fall into three main categories; direction-vector-based methods, local-plane-wave decomposition methods, and local-shift imaging condition methods. The direction-vector-based methods, which use either amplitude gradients or phase gradients, cannot handle overlapping events because of an assumption of one propagation direction per imaging point per imaging time; however, the ADCIGs from the directionvector-based methods have the highest angle resolution. A new direction-vector-based method using instantaneous phase gradients in space and time gives the same propagation directions and ADCIGs as those obtained by the Poynting vector or polarization vector based methods, where amplitudes are large. Angles calculated by the phase gradients have larger uncertainties at smaller amplitudes, but they do not significantly degrade the ADCIGs because they contribute only small amplitudes. The local-plane-wave decomposition and local-shift imaging condition methods, implemented either by a Fourier transform or by a slant stack transform, can handle overlapping events, and produce very similar angle gathers. ADCIGs from both methods depend on the local window size in which the transforms are done. In small local windows, both methods produce ADCIGs with low noise, but also with low angle resolution; in large windows, they have high angle resolution, but contain smeared artifacts.

show abstract

Section: " "mentioning

confidence: 99%

Comparison of methods for extracting ADCIGs from RTM

McMechan

Guan

2014

GEOPHYSICS

View full text Add to dashboard Cite

show abstract

“…By the end of 2000s, prestack 3-D reversetime migration has become a standard tool for depth imaging in structurally-complex areas, and it is becoming feasible to generate 3-D angle gathers as part of routine processing (Luo et al 2010;Vyas et al 2010;Xu et al 2010). The most important new theoretical developments are the ability to extract angle information from time-shift angle gathers (Sava and Fomel 2006;Vyas et al 2010), the ability to extract not only reflection-angle but also azimuth information (Xu et al 2010), and the extension of the angle-gather theory to anisotropy (Biondi 2007;Fomel 2009, 2011).…”

Section: Discussionmentioning

confidence: 99%

Theory of 3-D angle gathers in wave-equation seismic imaging

Fomel

2011

J Petrol Explor Prod Technol

View full text Add to dashboard Cite

I present two methods for constructing angle gathers in 3-D seismic imaging by downward extrapolation. Angles in angle gathers refer to the scattering angle at the reflector and provide a natural access to analyzing migration velocity and amplitudes. In the first method, angle gathers are extracted at each downward-continuation step by mapping transformations in constant-depth frequency slices. In the second method, one extracts angle gathers after applying the imaging condition by transforming local offset gathers in the depth domain. The second approach generalizes previously published algorithms for angle-gather construction in 2-D and commonazimuth imaging.

show abstract

“…Alternatively, the reflection angles can be calculated by applying SSs (Schultz and Claerbout, 1978) to each HOCIG Iðx; z; h x Þ to directly calculate the reflection angles from slopes of plane waves (Sava and Fomel, 2003;Biondi and Symes, 2004). The SSs alter the waveforms with phase shifts (Luo et al, 2010;Jin et al, 2014), so here, we use FTs instead of SSs when transforming from HOCIGs to ADCIGs. The local plane-wave assumption occurs in the first step.…”

Section: Smearing-effect Artifacts In the Local Shift Imaging Conditionmentioning

confidence: 98%

Removing smearing-effect artifacts in angle-domain common-image gathers from reverse time migration

McMechan

2015

GEOPHYSICS

View full text Add to dashboard Cite

Local plane-wave decomposition (LPWD) and local shift imaging condition (LSIC) methods for extracting angle-domain common-image gathers (ADCIGs) from prestack reverse time migration are based on the local plane-wave assumption, and both suffer from a trade-off in choosing the local window size. Small windows produce clean ADCIGs, but with low angle resolution, whereas large windows produce noisy ADCIGs, which include smearing-effect artifacts, but with high angle resolution. The cause of the smearing-effect artifacts in LPWD is the crosscorrelation of plane waves obtained by decomposition of the source and receiver wavefronts, at points that do not lie on the source wavefront excitation time trajectory. The cause of the smearing-effect artifacts in LSIC is the decomposition of curved events of offset-domain common-image gathers (ODCIGs) at incorrect depth points at zero offset. These artifacts can occur even if the migration velocity model is correct. Two methods were proposed to remove the artifacts. In the LPWD method, the smearing-effect artifacts were removed by decomposing and crosscorrelating the resulting source and receiver plane waves only at image points and excitation (image) times. In the LSIC method, the artifacts were removed by decomposing curved events in ODCIGs into planar events only at zero-offset target image points. Numerical tests with synthetic data revealed the success of the proposed methods.

show abstract

A comparison of methods for obtaining local image gathers in depth migration

Cited by 7 publications

References 13 publications

Comparison of methods for extracting ADCIGs from RTM

Comparison of methods for extracting ADCIGs from RTM

Theory of 3-D angle gathers in wave-equation seismic imaging

Removing smearing-effect artifacts in angle-domain common-image gathers from reverse time migration

Contact Info

Product

Resources

About