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ABSTRACT: Previous HitMigrationNext Hit of Velocity Spectra: An Example from the Timor Sea

BEASLEY, J. CRAIG, and ROLF KLOTZ, Western Geophysical Company, Singapore

Successful seismic imaging of complex geology such as that found in the Timor Sea requires accurate Previous HitmigrationNext Hit of the seismic data to collapse diffractions, image faults, and position reflectors in the correct spatial location. Although today's Previous HitmigrationNext Hit algorithms in theory generally are accurate, in practice Previous HitmigrationNext Hit accuracy for steep dips critically depends on the Previous HitmigrationNext Hit velocity.

An approach used routinely to estimate the Previous HitmigrationNext Hit velocity is to minimize the effects of dip and azimuth by applying dip movement (Previous HitDMONext Hit) to the data. However, velocity derived from Previous HitDMONext Hit-corrected data is located at an unmigrated position and should be repositioned prior to use as a Previous HitmigrationNext Hit velocity. The effect of this phenomenon will be demonstrated through an example from the Timor Sea in which, prior to Previous HitmigrationNext Hit, reflections and diffractions from a complex system of faulted carbonates conflict with low-relief primary reflections resulting in poorly resolved velocity analyses.

This problem can be overcome by employing conventional Previous HitmigrationNext Hit to migrate the Previous HitDMONext Hit velocity to the proper spatial location prior to migrating the seismic data. Velocity spectra are generated first from Previous HitDMONext Hit-corrected data on a regular spatial grid and then common-velocity slices are extracted and migrated. Finally, the migrated velocity is reassembled at common spatial locations into velocity spectra, which provide a better estimate of the true subsurface velocity.

By applying conventional Previous HitmigrationNext Hit principles to migrate velocity derived from Previous HitDMONext Hit-corrected data, velocity is placed at the correct spatial location as required for Previous HitmigrationNext Hit. The method provides an automated, efficient, and accurate procedure for determining Previous HitmigrationTop velocity.

 

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)