Anisotropic PS Kirchhoff PSTM & PSDM

Superior mode-converted imaging in time or depth

The WesternGeco prestack PS Kirchhoff migration workflows are the industry leaders for converted-wave velocity model parameterization and imaging.

PS Kirchhoff PSTM
Our model building and migration tools are based on a workflow using the vertical S-velocity instead of the more common method of using a non-physical converted-wave velocity. The PS Kirchhoff algorithm uses smoothed physical interval parameters for V_nmo(P), V_p/V_s(vert) and V_vert(S).

This has the advantage of dealing with more geophysically meaningful parameters with direct links to borehole measurements. All parameters can, therefore, be compared directly or constrained to information from wells or walkaway VSPs.

As rays used for wide-offset PSTM often travel horizontally, accurate treatment of ray bending and anisotropy is critical. The asymmetric PS operator is designed using full curved-ray, anisotropic ray tracing abased on the two separate, but consistent, P-wave and S-wave geological models.

PS Kirchhoff PSDM
For more complex structural challenges, anisotropic PS Kirchhoff prestack depth migration and a tomographic velocity model building approach can be used. Our implementation utilizes a four-parameter anisotropic velocity model and employs full 3D anisotropic ray tracing to handle any lateral velocity variations. Again, borehole information (in the form of well logs, check shots, and VSPs) provides geological constraints.

The use of prestack depth migrations and a common velocity model ensures that both PP and PS data are tied in depth. Final image volumes are, therefore, ready for Multicomponent Interpretation and Event Registration, and  Joint PP-PS Inversion.

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