Anisotropic Turning-wave Kirchhoff Prestack Time Migration

The standard for complex structural imaging in the time domain

Kirchhoff PSTM can accurately image steep or overturned events provided turning rays and anisotropy are taken into account. 3D Kirchhoff prestack time migration is ideally suited for imaging geological settings characterized by complex structure, but relatively gentle velocity gradients.

WesternGeco offers a full ray-traced implementation of anisotropic Kirchhoff prestack time migration. It is only by full ray tracing that we can handle propagation angles up to and including turning rays. This approach makes direct use of the interval properties vertical velocity and eta, derived from dual-parameter anisotropic velocity analysis. Other implementations may rely on high-order moveout corrections or make limiting assumptions about anisotropy (such as effective rather than interval eta values), with correspondingly negative impacts on the quality of the migrated result.

High-accuracy anisotropic ray tracing in prestack time migration yields better imaging of steep dips and can increase both vertical and lateral resolution. The migrated gathers are flatter, and better imaged, improving stack response, interval velocity analysis, subsequent AVA parameter estimation, and providing guidance and constraint to interval velocities and anisotropic parameters for depth migration.

Our Kirchhoff PSTM has been used successfully for many years in all possible geological settings around the world in land, marine and OBC (including multicomponent) environments.

The latest release includes several improved antialias options such as time-variant dip filtering and the Abma/Sun/Bernitsas antialias treatment. An anisotropic ray-traced traveltime calculator that matches our InVA package ensures consistency between migration velocity analysis and subsequent application during imaging.

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