Nodal Processing

A total nodal solution

Because we also design, manufacture and use cable-free node systems for land, transition zones and water depths down to 3000 meters, we have also uniquely designed our processing system to optimize nodal data.

To this end, we have developed unique processing techniques to improve the quality of 2D and 3D nodal data, and, in fact, because our nodes can be precisely and repeatably placed, our proprietary front-end processing techniques are essential for successful 4D analysis.

Our technology has been applied to data acquired by international oil companies and has been very well received. Significantly, we are the most experienced contractor to use these advanced processing techniques and reap the full benefits of this revolutionary acquisition technology. These techniques include, but are not limited to, the following:

Wavefield separation

In marine multi-component data processing, separation of seismic recordings into upgoing and downgoing wavefields is desired. Quality, however, is degraded due to shear-related noise and other non-P-wave energy in the vertical geophone.

We eliminate this energy using a patented frequency-dependent 3D tau-p technique designed to identify reliable p-wave energy and tune the data accordingly. The result is a vertical geophone with the same signal-to-noise content as the hydrophone that maintains phase discrimination of upgoing and downgoing waves. The hydrophone remains unchanged. Component variations yield isolated wavefields optimal for downstream processing.

Wavefield Separation
[Left] Vertical geophone before V(z) attenuation. [Right] Vertical geophone after wavefield separation and V(z) attenuation.

Multiple attenuation

Wave-equation surface multiple attenuation (WEMA) is a model-driven technique requiring the earth as a model containing reflectors whose multiples must be attenuated. Here, the measured wavefield is propagated from the surface to the target reflector(s) and back, using finite-difference wave-equation modeling code. This way, the primaries are converted into first-order multiples, first-order multiples into second, and so on. Modeled multiples are then adaptively subtracted. Data preparation requirements are similar to SRMA, although in case of cross dip, there may be fewer requirements for cross-line acquisition footprint.

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  • No demultiple
  • Multiple removed

Mirror migration

In deep water ocean-bottom node (OBN) acquisition, each node records reflected energy from the subsurface more than once. Seismic energy can arrive directly at the seafloor (upgoing waves) or after a near-total internal reflection at the air-water interface (downgoing waves). With both a hydrophone and geophone in each node, these two wavefields can be processed separately, providing different illumination of the subsurface. Mirror migration images the downgoing wavefield, providing superior illumination of the shallow horizons from the perspective of the virtual node position.

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  • Wavefield migration diagram
  • [Left] Common receiver migration of upgoing wavefield
    [Right] Common receiver mirror migration of downgoing wavefield