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Velocity Resolution And Salt Boundary Placement In Subsalt ImagingNormal access

Authors: Uwe Albertin, S. Kapoor, Wenfong Chang, Richard Beals and Jeff Curtis
Event name: 6th International Congress of the Brazilian Geophysical Society
Session: Imaging Methodology
Publication date: 15 August 1999
Organisations: SBGf
Language: English
Info: Extended abstract, PDF ( 568.33Kb )

Summary:
The interpretation of salt geometry is a critical aspect of velocity model building for 3D salt and subsalt
imaging. Here we investigate the effect of salt boundary placement error in the velocity model building
process. Using an example from deep water Gulf of Mexico, we first illustrate how velocity resolution
drops beneath salt . We then show how an error in salt boundary placement can produce significant
residual moveout in prestack migrated gathers. If this residual moveout is interpreted as arising from a
velocity anomaly in the sediment, a velocity update of the sediment will introduce error into the sediment
velocity model that in turn introduces false structure into the depth image. We show for this example that
the correct placement of salt both flattens gathers and eliminates the false depth structure. Techniques
for distinguishing between sediment errors and salt boundary placement errors are discussed.

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