Schlumberger

Data Optimization

Wavefield reconstruction and 3D deghosting

Generalized matching pursuit (GMP) is used to simultaneously reconstruct the pressure wavefield and perform 3D deghosting using the IsoMetrix multimeasurement data. It generates the main IsoMetrix field deliverable, which comprises a regular 'carpet' of channels for each shot point—equivalent to 6.25-m channel intervals on virtual streamers towed at a nominal 6.25-m lateral separation—and is termed, the IsoGrid.

The power of GMP lies in the handling of any components of the seismic wavefield that are not confined to travelling straight from source to receiver, but instead have a significant degree of propagation across the streamer spread. These may include seismic reflections, diffractions, multiples or other noise modes, and, if not treated correctly, can generate artefacts in the final interpretation volumes. Using GMP, any energy arriving from the crossline direction which had previously been spatially aliased and wrapped around as noise on conventional shot records, is now sampled appropriately both spatially and temporally. GMP is a data-driven approach, and, subject to certain assumptions, has been shown to accurately reconstruct the pressure wavefield in situations where conventionally-recorded seismic events are exposed to a very high order of aliasing in the crossline direction.

Source deghosting

The WesternGeco broadband Delta calibrated marine broadband seismic source complements IsoMetrix technology by providing improved low-frequency content and no source notches below 150 Hz for all directions within a 20-degree cone from the vertical. Residual spectral shaping can be performed directly after wavefield reconstruction.

Beyond the IsoGrid

After wavefield reconstruction to the IsoGrid, the choice of processing and imaging steps is governed by the survey-specific objectives and project constraints. However, maximum value from IsoMetrix technology can be obtained when the full complexity of the reconstructed wavefield is leveraged throughout the processing sequence. A portfolio of new algorithms are emerging that, for example, make explicit use of the dense, 3D geometry of the IsoGrid shot records—for example, to enable more powerful 3D noise attenuation or accurate multiple prediction.

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WesternGeco

Capture the Complexity of the Seismic Wavefield

IsoMetrix technology delivers crossline wavefield reconstruction from a single source.
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