--> --> Migration Velocity Analysis Using Seismic Multiples, by C. D. Manuel; #90902 (2001)
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Migration Previous HitVelocityNext Hit Analysis Using Seismic Multiples

C. D. Manuel
Curtin University of Technology, Dept. of Exploration Geophysics, Perth, Australia

Migration Previous HitvelocityNext Hit analysis (MVA) is an essential component of the Previous HitvelocityNext Hit model building technique in complex geological areas and depth migration is the process whereby seismic data in the timeoffset domain is mapped to the depth domain. After migration with a certain Previous HitvelocityNext Hit, the curvature remaining on a primary reflection gives an indication of the variance from the true average Previous HitvelocityNext Hit of the primary. If migration is performed with the correct Previous HitvelocityNext Hit then the reflector will appear flat. This is done for each primary reflection to find the Previous HitvelocityNext Hit structure as a function of depth. The process is repeated for other surface locations until a Previous HitvelocityNext Hit model is generated for the region.

The present research includes the analysis of multiple reflections in MVA. Any initial error in Previous HitvelocityNext Hit between the migration and interval velocities will be increased as the distance traveled through the Earth increases. Hence in migration, multiples will be more sensitive than primaries to changes in the Previous HitvelocityNext Hit model. On a coherency plot, multiples will stack in a more localized region. This should result in increased accuracy in determining interval Previous HitvelocityNext Hit and interval thickness. It should also reduce the number of migration iterations needed to converge on an accurate solution. This has implications for reducing the time and cost of the MVA process. The ability to create a more accurate Previous HitvelocityTop model will mean that the depth image obtained from seismic data will be much more accurate. This will in turn enable more accurate positioning of wells.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid