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Wavefield Separation for Ocean Bottom Seismic Data

In addition to the operational advantages, a key benefit of utilizing ocean bottom cables (OBC) or ocean bottom nodes (OBN) for acquisition is the ability to exploit the combined response of dual sensor recording (hydrophones and vertical geophones*) to discriminate and effectively suppress ghosts and receiver-side water column multiples from the data. The result is greater bandwidth and a higher quality image leading to more confident interpretation and reservoir characterization.

ION expertly leverages the nature of dual-component data in OBC/OBN data acquisition to achieve this goal. After proper phase and amplitude calibration of the vertical and the pressure component response, a wavefield separation technique exploits the opposite polarity of down-going waves recorded in the two receiver types to remove receiver-side ghosts and multiples. Processing and combining up- and down- going waves in certain ways further reduces noise and multiples to broaden the frequency spectrum and improve the image quality.

System Calibration

After noise removal, system calibration removes the phase and amplitude differences between hydrophone and vertical geophone response before summation techniques are applied. Using theoretical instrument responses and/or data dependent methods we derive match filters to equalize amplitude and phase of hydrophone/geophone pairs. The processing methodology is tailored for acquisition in different water depths.

Wavefield Separation

A wavefield separation approach exploits up-going and down-going energy to not only de-ghost and remove receiver-side multiples, but to reduce acquisition footprint and improve illumination, and is tailored for different water depths.

The down-going wavefield is also isolated by these workflows. Down-going energy can be mirror imaged to reduce acquisition footprint, improve illumination and minimize migration swing noise. Additionally, by combining up- and down-going energy in certain ways we can further reduce the effects of noise and multiples. The process improves the quality of the OBS data for imaging.

*Although geophones are explicitly referenced, results apply equally well to accelerometers.