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ION’s Kirchhoff pre-stack depth migration algorithm is amplitude preserving, making it the premier choice for providing

gathers for AVO studies. Using travel-time tables based on full TTI anisotropic 3D ray-tracing, including turning rays to

capture reflection energy from overhanging structures, it is well suited for imaging data from areas of significant lateral

velocity change and geological complexity. Ray tracing can be performed from the sea surface or from true shot source

and receiver depths, as required for OBC data, and also from topography for land environments.

Angle information is computed during 3D ray-tracing and used to calculate anti-aliasing filters and to limit the migration

aperture. For the ray-path selection, users can choose between highest amplitude and shortest ray length.

As well as full 3D volumes, the algorithm can output inlines, crosslines, CRP gathers, and OVT ensembles for OBC or

WAZ data. In addition to outputting gathers for subsequent non-parametric picking and tomographic velocity update, our

PreSDM algorithm can create velocity-perturbation scans of both stacked images and gathers, providing velocity model

update in areas where automatic picking proves to be unreliable.

In addition to conventional acoustic imaging, the algorithm is capable of visco-acoustic imaging (also referred to as

Q-migration). For strongly attenuative media, such as near-surface gas-charged geobodies, the dimming caused by

absorption can be more correctly addressed during migration. In this case, in addition to an interval velocity field, we

must also supply an effective-Q field, furnished by our Q-tomography engine.

KEY FEATURES AND BENEFITS

Amplitude Preservation – ION’s Kirchhoff

migration method has proven to be an amplitude-

preserving product, allowing the migrated gathers

to be used as input for more accurate AVO analysis.

Turning Ray Imaging – The algorithm can depth-

image very steep or overturned seismic events, as in

the cases of vertical or overturned salt walls and faults.

To achieve this objective, travel-time tables are

constructed allowing ray propagation angles to

bend up to 150°.

Kirchhoff Pre-Stack Depth Migration

Left: preSTM image of an onshore detached salt body. Right: corresponding preSDM image of the same structure. As expected, due to the large velocity contrast at the steep top salt interface, the time migration is incapable of producing a meaningful image.

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KEY FEATURES AND BENEFITS (CONTINUED)

Anisotropy – Our Kirchhoff solution can image from transversely isotropic (uniaxial anisotropy) velocity models. The

medium is parameterized in terms of Thomsen’s parameters (i.e., epsillon and delta), the vertical velocity, and the

orientation of the axis od symmetry, all of which may be spatially variant. The result is a higher-quality depth image of the

subsurface that better matches the depths of geologic structures from well data.

Velocity Analysis – Extreme flexibility in data output and the accuracy of the

algorithm makes our approach suitable for true 3D migration velocity analysis. The

imaging effect of a varying range of velocities relative to the base model can be

analyzed on gathers, stack volumes, and focusing panels.

Operator Anti-aliasing – Migration noise as a result of operator aliasing is

attenuated very effectively through the use of a multi-frequency anti-alias operator

that controls frequency as a function dip, Steep dips are preserved while migration

noise is minimized.

Topography – Topography has a kinematic effect on the pre-stack seismic data, and unless it is properly accounted for,

the velocity model and the resulting image-quality will be compromised. Our Kirchhoff algorithms honors topography

exactly in both the travel-time computation and the imaging stages.

Efficiency – Our sophisticated Kirchhoff solution is one of the fastest raytracing implementation in the industry. Its high

performance allows ION to achieve an iteratively generated, high-quality velocity model and a full volume 3D pre-stack

depth migration in shorter turnaround times.

Application – PreSDM is designed for 2D and 3D land and marine seismic data. Our Kirchhoff approach is well suited for

depth imaging of very steep and overhanging structures, in the presence of velocity anisotropy, and when both accurate

depth structure and amplitude preservation are required.

ION’s Kirchhoff PreSDM solution is capable of imaging complex geologic structures while preserving their amplitude. With the Turning Ray option, very steep dips and overturned salt walls and faults can be imaged.