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

Sergey Fomel

doi:10.1007/s13202-011-0004-8

Abstract

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 common-azimuth imaging.

Highlights

I present two methods for constructing angle gathers in 3-D seismic imaging by downward extrapolation
Wave extrapolation provides an accurate method for seismic imaging in structurally complex areas (Biondi 2006; Etgen et al 2009)
J Petrol Explor Prod Technol (2011) 1:11–16 extracting angle gathers from migrated images

Summary

Introduction

I present two methods for constructing angle gathers in 3-D seismic imaging by downward extrapolation. One extracts angle gathers after applying the imaging condition by transforming local offset gathers in the depth domain. One generates gathers at each depth level converting offset-space-frequency planes into angle-space planes simultaneously with applying the imaging condition. The offset in this case refers to the local offset between source and receiver parts of the downward continued prestack data. Biondi and Symes (2004) demonstrate that the method of Sava and Fomel (2003) is strictly valid in the 3-D case only in the absence of cross-line structural dips. They present an extension of this method for the common-azimuth approximation (Biondi and Palacharla 1996)

Discussion

Conclusion