What is it about?
We have developed a prestack time-migration tool for local improvement of the seismic migration-velocity model. The method is based on remigration trajectories that describe the position of an image point in the image domain for different source-receiver offsets as a function of the migration velocity.
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Why is it important?
It determines kinematic migration parameters using local-slope information of migrated seismic reflection events. These parameters, in turn, are used to locally correct the velocity model. The main advantage of this technique is that it allows us to carry out a moveout correction not just at a fixed point in a zero-offset (poststack) time-migrated gather, but varying through all offsets of a common-image gather, taking into account the reflection-point displacement in the midpoint direction. In other words, it provides for time-migration velocity analysis from prestack data. The procedure is quite efficient.
Perspectives
We have developed a tool that uses the estimation of local kinematic attributes of selected events in seismic data to locally update a previous velocity model and improve the positioning of key reflectors. The method is based on image-wave propagation in the CIG domain described by means of time-remigration trajectories in the prestack time-migrated domain. Such a trajectory is defined as the set of points at which a certain point on a reflection event is migrated to as a function of migration velocity. The methods consist of analyzing the local slope of selected key reflections and determining the velocity value for which an approximate RMO expression is minimized. The advantage of this procedure over conventional MVA methods is that the RMO expression follows the events outside a fixed CIG. In this way, more accurate velocity information can be extracted from the data.
Henrique B. Santos
Universidade Estadual de Campinas
Read the Original
This page is a summary of: Prestack time-migration velocity analysis using remigration trajectories, Geophysics, July 2015, Society of Exploration Geophysicists,
DOI: 10.1190/geo2014-0205.1.
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