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Wave-equation migration velocity analysis by focusing diffractions and reflections

By
Paul C. Sava
Paul C. Sava
Formerly with Stanford University, Stanford Exploration Project, Geophysics Department, Stanford, California 94305-2215; presently with the University of Texas-Austin, Bureau of Economic Geology, University Station, Box X, Austin, Texas 78713-8924.
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Biondo Biondi
Biondo Biondi
Stanford University, Stanford Exploration Project, Geophysics Department, Stanford, California 94305-2215.
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John Etgen
John Etgen
BP, E&P Technology Group, 200 Westlake Park Boulevard, Houston, Texas 77079-2696.
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Published:
January 01, 2016

Abstract

We propose a method for estimating interval velocity using the kinematic information in defocused diffractions and reflections. We extract velocity information from de-focused migrated events by analyzing their residual focusing in physical space (depth and midpoint) using prestack residual migration. The results of this residual-focusing analysis are fed to a linearized inversion procedure that produces interval velocity updates. Our inversion procedure uses a wavefield-continuation operator linking perturbations of interval velocities to perturbations of migrated images, based on the principles of wave-equation migration velocity analysis introduced in recent years. We measure the accuracy of the migration velocity using a diffraction-focusing criterion instead of the criterion of flatness of migrated common-image gathers that is commonly used in migration velocity analysis. This new criterion enables us to extract velocity information from events that would be challenging to use with conventional velocity analysis methods; thus, our method is a powerful complement to those conventional techniques.

We demonstrate the effectiveness of the proposed methodology using two examples. In the first example, we estimate interval velocity above a rugose salt top interface by using only the information contained in defocused diffracted and reflected events present in zero-offset data. By comparing the results of full prestack depth migration before and after the velocity updating, we confirm that our analysis of the diffracted events improves the velocity model. In the second example, we estimate the migration velocity function for a 2D, zero-offset, ground-penetrating radar data set. Depth migration after the velocity estimation improves the continuity of reflectors while focusing the diffracted energy.

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Contents

Society of Exploration Geophysicists Geophysics Reprint Series

Seismic Diffraction

Kamil Klem-Musatov
Kamil Klem-Musatov
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Henning Hoeber
Henning Hoeber
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Michael Pelissier
Michael Pelissier
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Tijmen Jan Moser
Tijmen Jan Moser
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Society of Exploration Geophysicists
Volume
30
ISBN electronic:
9781560803188
Publication date:
January 01, 2016

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