Aspects of 3-D DMO correction — a summary

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Seismic Data Analysis
Series Investigations in Geophysics
Author Öz Yilmaz
ISBN ISBN 978-1-56080-094-1
Store SEG Online Store

Because of irregular spatial sampling associated with 3-D recording geometries, the 3-D DMO process is best applied in the time-space domain using the integral method (principles of dip-moveout correction). A velocity analysis is then performed following the DMO correction to estimate dip- and azimuth-corrected velocities.

In principles of dip-moveout correction, we discussed the principles of DMO correction and studied its practical aspects using synthetic and field data. We now extend aspects of 2-D DMO correction outlined in principles of dip-moveout correction to 3-D DMO correction.

  1. The process of 3-D dip-moveout corrects for the dip and source-receiver azimuth effects on stacking velocities.
  2. Thus, it preserves conflicting dips with different stacking velocities during CMP stacking.
  3. The 3-D DMO stack, therefore, is a closer representation of a 3-D zero-offset section as compared to a conventional CMP stack volume of data based on normal-moveout correction, only.
  4. The 3-D DMO stack can then be migrated using a 3-D zero-offset migration algorithm with greater accuracy.
  5. Conflicting dips with different stacking velocities give rise to multivalued velocity picks from velocity spectra. Velocity analysis of 3-D DMO-corrected data alleviates this problem and increases the accuracy of picking an unambiguous velocity function from a velocity spectrum.
  6. Velocities estimated from 3-D DMO-corrected data are dip and azimuth independent; therefore, they are more suitable to derive a migration velocity field as compared to velocities estimated from data without 3-D DMO correction.
  7. 3-D DMO correction actually is a process of partial migration before stack. Specifically, it maps normal-moveout-corrected data to normal-incidence reflection points in the subsurface. As a result, the midpoint is a variant under DMO correction.
  8. As a direct consequence of aspect (g), 3-D DMO correction removes the reflection point dispersal associated with nonzero-offset recording in the presence of dipping reflectors.
  9. By 3-D DMO correction, prestack data can be implicitly regularized into common-midpoint gathers. This then facilitates sorting of prestack data into a set of common-offset volumes, each of which can be considered a replica of a 3-D zero-offset wavefield.
  10. Following 3-D DMO correction, prestack data can be migrated so as to create CMP gathers in their migrated position. This then enables us to conduct velocity analysis to derive a migration velocity field with greater confidence.
  11. Finally, the CMP gathers from prestack time migration of 3-D DMO-corrected data can be used for amplitude variation with offset analysis.

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