CGG's CleanSweep is a new technology which unlocks the full potential of broadband land seismic by delivering a sweep featuring high-fidelity low frequencies free of harmonic noise and exceptionally high signal-to-noise ratio over the whole bandwidth. CleanSweep enables you to leverage the broad frequency content of your data for more reliable inversion and interpretation.
The advent of a new generation of sweeps tailored to extend the bandwidth at both low and high frequencies opened the door to onshore broadband acquisition. However, the full potential of these broadband sweeps has remained until now, obscured by the undesired harmonic distortion that was inevitably contaminating the whole bandwidth. To mitigate the effect of this broadband harmonic noise, the industry has developed specific acquisition strategies and post-acquisition processing techniques, but without addressing the challenges during sweep generation.
CleanSweep provides a signal free of harmonic noise over the first four octaves of frequency during sweep generation. It therefore avoids subsequent broadband harmonic noise contamination. CleanSweep is a noise cancellation solution which consists in adding an anti-distortion signal extracted from field measurements to a standard pilot sweep. This is specifically designed to result in a ground force that is free of harmonics and accurately fits the desired pilot.
Average time-frequency amplitude spectra of the ground force for a low-dwell broadband sweep, without and with CleanSweep. With CleanSweep the harmonic noise is totally removed over the first four low-frequency octaves and is significantly removed over the remaining bandwidth.
CleanSweep is effective on all sweep designs particularly CGG's EmphaSeis low-dwell sweep, delivering four low-frequency octaves free of distortion. This removes the requirement for the use of post-processing techniques to eliminate the high distortion energy commonly recorded at low frequencies and therefore reduces the risk of impairing the signal.
Because of the broadband nature of harmonic noise it will contaminate the entire bandwidth if not handled properly. By canceling the distortion during sweep generation, CleanSweep provides a signal-to-noise ratio uplift over the full bandwidth.
In flip-flop mode, CleanSweep avoids self-harmonic contamination such as ground roll harmonic interference with early arrivals. In slip-sweep mode, CleanSweep further improves the signal-to-noise ratio by reducing significantly the harmonic contamination from the next shots.
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