Linear AVO Inversion by Prestack Depth Migration: Imaging Angle Dependent Reflectivity as a Tool for Litho-Stratigraphic Inversion

摘要

In the thesis a linear inversion strategy is proposed, which transforms preprocessed seismic measurements at the surface into a depth section. The section may represent a structural image or it may represent an image of specific lithoclass transitions. The inversion strategy can be subdivided into two steps: a migration step followed by a linear inversion step. The first part of the thesis discusses the extraction of angle dependent reflection information from seismic surface data. By applying the generalized imaging principle, the elastic angle dependent reflection information, or AVO behavior, can be retrieved for each grid point. The angle dependent reflection information is determined by the contrasts in the elastic parameters (mass density, compressional and shear wave velocity) above and below an interface. The angle dependent reflection information can be elegantly presented in the so-called reflection matrix. For each lateral position and extrapolation level the information in the reflection matrix can be transformed into a so-called z - p gather, where z represents the depth and p the ray parameter. The principle of the generalized imaging step is illustrated with some simple examples.