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Abstract:
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Seismic amplitude-versus-offset (AVO) analysis is a powerful geophysical technique for direct detection of gas on seismic records, and has increased the drilling success ratio in many areas. Due to the shifting of focus from 2-D migration to 3-D migration, to image correctly in regions with complex geological structures, full-volume AVO analysis of seismic reflection data is useful in detecting areas of anomalous AVO attributes (intercept and gradient), in a 3-D seismic data volume. Gardner et al. (1986) introduced 3-D dip moveout (DMO) and 3-D pre-stack imaging (PSI) as an alternative approach to 3-D time migration. One objective of this thesis is to study the amplitude behavior of the DMO and PSI methods, and show that PSI can be used to preserve the amplitude information.
This thesis presents a new implementation of the PSI method. The kinematic correctness of this new PSI implementation, and the existing DMO implementation (Canning, 1993) is illustrated using examples from their application to three-dimensional synthetic data. The amplitude behavior of the both these implementations are illustrated using several examples. Based on the amplitude behavior, two different schemes to estimate the AVO attributes (intercept and gradient) are presented. Both these schemes provide reliable estimates of the AVO attributes, for reflection events with dip angles less than 30 degrees. (Abstract shortened by UMI.) |
