Preservation of AVO after migration

Oliver Lahr, Gary F. Margrave

Choice of migration algorithms and seismic acquisition techniques are two contributing factors of how well Amplitude Variation with Offset (AVO) data is preserved. In this report, these effects are investigated using synthetic Shots and Common Offset Vectors (COV gathers), the latter being the 3D extension of Common Shot gathers. The data, both shots and gathers, were created from a 2D synthetic data set that is comprised of the three different AVO classes occurring at different horizontal layers, and was in turn created using elastic modeling. A simple orthogonal survey was used, with different data sets being created by varying the shot and receiver line spacing to simulate different levels of decimation. To mitigate the effect of these decimations and its associated seismic acquisition footprint, they were then migrated using Kirchhoff migration. It is the purpose of this report to show how well the Zoeppritz plot of the AVO anomalies pictured below could be reproduced for the input data shown in the well logs and associated table below, and identify the scenarios that one or the other migration techniques undertaken here.