Migration method improves subsalt imaging

 

The velocity analysis shows a single Kirchhoff migrated depth gather with its related semblance analysis and stacked section. Note that the gathers can be analyzed to determine if the migration velocity was too fast or too slow. Thus, the velocity field can be updated to a more accurate velocity field for subsequent migrations.

The velocity analysis shows a single Kirchhoff migrated depth gather with its related semblance analysis and stacked section.

HOUSTON, May 11 — Spectrum ASA, Oslo, reported good results from the use of wave-equation migration in a 2D seismic dataset to image geology below salt in the Gulf of Mexico.

By the Oil and Gas Journal 

The geophysical contractor first applied normal Kirchhoff eikonal prestack depth migration (PSDM), a method for improving the accuracy of seismic records, to data from a 28,000-km 2D survey of the eastern gulf.

It then used wave-equation migration, which revealed “clearer subsalt definition,” said Andy Cuttell, head of worldwide data processing operations.

Spectrum explained that wave-equation migration “takes into account the multiple arrivals of seismic waves in the subsurface, overcoming the limitations of standard Kirchhoff PSDM, which takes into account only the first arrival of seismic waves.”

Compared to normal Kirchhoff migrations, the contractor said, “the wave-equation method increases the focusing of seismic images in areas with complex velocity models and excels in imaging below geology that is traditionally difficult to penetrate with seismic signals, such as salt formations.”

Spectrum workers in Houston tested the wave equation technique in data from the first phase of a multiclient survey and determined that it has potential to improve imaging of the Florida escarpment and the base-of-salt definition.

For more information about Spectrum’s depth imaging techniques please click here

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