Prestack depth migration

By | 05.12.2018

In the simplest geological setting, with a single horizontal reflector, a constant velocity and a source and receiver at the same location referred to as zero-offset, where offset is the distance between the source and receiver , the geophysicist can determine the location of the reflection event by using the relationship:. By using this site, you agree to the Terms of Use and Privacy Policy. This page was last edited on 16 September , at Though stacking the data without the migration corrections yields a somewhat inaccurate picture of the subsurface, migration is preferred for better most imaging recorder to drill and maintain oilfields. Depth Migration is applied to seismic data in depth regular Cartesian coordinates, which must be calculated from seismic data in time coordinates.

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Why prestack depth migration is worth its salt

An example of such can be seen in the diagram. Ray trace travel times are also available.

Reverse Time Migration RTM Reverse Time Migration RTM is a pre-stack two-way wave-equation migration algorithm-solution suited for imaging in areas of complex structure, being able to handle steep structural dips and high velocity contrasts salt basins.

In these situations a form of migration is used called pre-stack migration PreSMin which all traces are migrated before being moved to zero-offset. Once data are spatially regularized so that the resulting prestack data have uniform fold of coverage and migraiton been corrected for source-receiver azimuth, then, in principle, any of the three categories of migration algorithms — Kirchhoff-summation, finite-difference, or frequency-wavenumber, can be used to perform 3-D prestack depth migration.

Why prestack depth migration is worth its salt - Offshore

Depth Migration is applied to seismic data in depth regular Cartesian coordinates, which must be calculated from seismic data in time coordinates. Journal of Applied Geophysics. Post-stack migration begins with seismic data which has already been stacked, and thus already lost valuable velocity deptg information. The better treatment of amplitudes by the frquency-wavenumber algorithms compared to the Kirchhoff summation technique, however, has greatly increased their use in practice [3 ].

In this case, 3D migration is needed to attain the best possible image.

It is a half-sphere, and not a full sphere, because we can ignore all possibilities that occur above the surface as unreasonable.

Depending on budget, time restrictions and the subsurface geology, geophysicists can employ 1 of 2 fundamental types of migration algorithms, defined by the domain in which they are applied: Kirchhoff Pre-Stack Depth Migration Pre-SDM is the most commonly used pre-stack migration algorithm and it is well suited for moderately complex geology settings. Noise that may be easy to distinguish pre-migration could be smeared across the entire aperture length during migration, reducing image sharpness and clarity.

A form of migration is one of the standard data processing techniques for reflection-based geophysical methods seismic reflection and ground-penetrating radar The need for migration has been understood since the beginnings of seismic exploration and the very first seismic reflection data from were migrated. Seismic waves are elastic waves that propagate through the Earth with a finite velocity, governed by the elastic properties of the rock in which they are travelling.

In this case, the distance is halved because it can be assumed that it only took one-half of the total travel time to reach the reflector from the source, then the other half to return to the receiver. This method does therefore require a velocity model, making it resource-intensive because building a seismic velocity model is a long and iterative migrattion.

When data is acquired at non-zero offsets, the sphere becomes an ellipsoid and is much more complex to represent both geometrically, as well as computationally. Paradigm RTM is driven by velocity models developed with and refined using the GeoDepth velocity modeling tools. A form of migration is one of the standard data processing techniques for reflection-based geophysical methods seismic reflection and ground-penetrating radar.

Retrieved 24 October Migration can lead to a dramatic uplift in image quality so algorithms are the subject of intense research, both within the geophysical industry as well as academic circles. migratioon

Seismic migration - Wikipedia

Stolt migration, Gazdag and Finite-difference migration. Terms of use Privacy policy Contact us. From Wikipedia, the free encyclopedia. Migration moves dipping reflectors to their true subsurface positions and collapses diffractions[4] resulting in a migrated image that typically has an increased spatial resolution and resolves areas of complex geology much better than non-migrated images.

This page was last edited on 16 Septemberat Retrieved from " https: While it has the advantage of producing an image in depth along a set of line traverses without having to produce an image volume in depth, Kirchhoff summation technique lacks the rigor to handle amplitudes that the frequency-wavenumber techniques can provide.

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Seismic migration

The need for migration has been understood since the beginnings of seismic exploration and the very first seismic reflection data from were migrated. What then is an migrration algorithm for 3-D prestack depth migration — Kirchhoff-summation, finite-difference, or frequency-wavenumber? Zero-offset data is important to a geophysicist depgh the migration operation is much simpler, and can be represented by spherical surfaces. In the simplest geological setting, with a single horizontal reflector, a constant velocity and a source and receiver at the same location referred to as zero-offset, where offset is the distance between the source and receiverthe geophysicist can determine the location of the reflection event by using the relationship:.

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