Kirchhoff Prestack Depth and Time Migration | Schlumberger

Kirchhoff Prestack Depth and Time Migration

The most widely used migration algorithm in the industry

3D Kirchhoff prestack depth migration (PSDM) sets the standard for depth imaging as a key component of the seismic toolbox.

Our implementation images arrivals that propagate at 90° and higher angles as turning waves. Image quality is further improved by the ability to honor both vertical and tilted transverse isotropy (VTI and TTI).

This flexible, amplitude-preserving implementation has been used for many years in a variety of geological settings around the world—in land, marine, and ocean bottom cable (OBC) geometries—and for imaging multicomponent data. Our massive parallel compute clusters ensure rapid delivery without sacrificing quality.

Our Kirchhoff PSDM allows direct ray tracing through explicit surfaces in the velocity model. This can help generate more accurate traveltimes, resulting in better positioning and image fidelity.

The advantage of depth over time imaging.
Prestack depth migration generates more accurate images (left) reducing exploration risk and improving reservoir definition.

Kirchhoff prestack time migration (PSTM) can accurately image steep or overturned events, provided that turning rays and anisotropy are taken into account.

3D Kirchhoff PSTM is ideally suited for imaging geological settings characterized by complex structure but relatively gentle velocity gradients.

We offer a full ray-traced implementation of anisotropic Kirchhoff PSTM. 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 vertical velocity and eta interval properties 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 PSTM 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, and subsequent AVA parameter estimation. Additionally, the gathers provide guidance and constraint to interval velocities and anisotropic parameters for depth migration.

Salt flank imaging using anisotropic turning-wave Kirchhoff PSTM.
Kirchhoff anistropic turning-wave PSTM (left) demonstrates significant improvements in structural imaging of overlying salt flanks compared with a conventional common-offset time migration (right).

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