Amplitude migration in v(z) media

Oliver Lahr, Gary F. Margrave and Kay Yuhong Liu

ABSTRACT

This report is meant to investigate the notion that amplitude migration in a v(z) medium must be treated differently than migration in a constant velocity medium. It is based on findings that migrated shot gathers near edges do not show even remotely close correct amplitudes. Reasons seem to deal with the fact that geometrical, both in-phase and out of phase, must be dealt with. To prove this, a ray based analysis was undertaken to account for spreading of both kinds. Based on that, it will be shown here that accounting for a v(z) medium will result in migrations that restore amplitudes more correctly than simply assuming a constant velocity medium. In particular, we will use a flat reflector model and a simple AVO 3 model. Also, several cost-saving measures that come with this improved migration will be pointed out.

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