Common reflection angle migration

Zvi Koren*, Dan Kosloff

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

A ray-based migration/inversion approach for the construction of amplitude-preserved common image gathers (CIG) in the angle domain is presented. It is shown that the reflected events in the gathers are balanced and continue for a wide range of reflection angles, even in complex areas with multi-arrivals. The method can be used for detailed velocity-model determination and for accurate amplitude variation with angle (AVA) analysis in such areas. Our method is based on shooting rays from the image points up to the surface, forming a system of diffracted rays with uniform angle increments. Each pair of rays is a potential reflected ray with a given direction (dip angle) and a given reflection angle. The CIG traces are constructed by summing all seismic events reflected/diffracted from the image points with the same reflecting/diffracting angle. Two different approaches are presented in this paper. The first is a reconstruction of the CIG in windows centered along interpreted horizons (AVA migrated panels). It is assumed that the general direction of the reflecting horizon normals at each point is known. This allows defining a local system of assumed reflected (specular) rays at each point and therefore to define a small horizon-based migration aperture. The second approach is designed for reconstructing the full image where no assumption is made for the directivity of the specular rays. We discuss the computation of amplitude-weighted factors, small aperture definition and stretch factors. We next examine and demonstrate the extension of the method for migrating the full image. The implementation of the method for complex geological structures is demonstrated with the Marmousi dataset.

Original languageEnglish
Pages (from-to)41-57
Number of pages17
JournalJournal of Seismic Exploration
Volume10
Issue number1-3
StatePublished - 2001
Externally publishedYes

Keywords

  • Amplitudes and phases preservation
  • Common reflection angle gathers
  • Model-based aperture
  • Multi-arrivals pre-stack Kirchhoff depth migration
  • Output driven approach
  • Uniform dip angle illumination

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