Abstract
Receiver ghosts attenuate marine seismic reflection data at harmonic frequencies that depend on the propagation angle and the streamer depth below the sea surface. The resulting loss of bandwidth is one of the major factors hampering seismic resolution. In near-surface and legacy multi-channel data, receivers depth is often unknown and may vary significantly both along the streamer length and during the survey, making frequency–slowness deghosting techniques unsuitable. In this work, we present a method for the attenuation of receiver ghost reflections in data with an arbitrary streamer depth profile varying during the survey. For each trace, a different deghosting operator is estimated and applied at different two-way-time windows, in order to account for depth-dependent changes in reflection angles. The ghost null frequencies are picked on the time-varying power spectrum via an automatic algorithm, guided by a user-dependent a priori function, and optimised to respect the harmonics’ periodicity. The power of the inverse filter is adjusted by adaptively damping abnormal amplitudes in the deghosted spectra. The algorithm is applied to high-resolution (GI-gun, 20–400 Hz) and ultra-high-resolution (Sparker, 0.2–3.0 kHz) multi-channel datasets, yielding an excellent bandwidth recovery and gain in resolution in the final stacks. Limited computing time and straightforward application make the method widely applicable and cost-effective.
Highlights
Maximising the frequency bandwidth of recorded seismic reflection data is instrumental to obtaining optimal resolution and penetration depth within the inherent limitations of source and receiver antennas
The resulting loss of bandwidth depends on the acquisition setting, namely, the deeper the receiver below the sea surface and the narrower the reflection angle, the longer the time delay and the lower the fundamental ghost notch frequency
If the time delay is longer than the wavelet duration, commonly in very-highfrequency seismic data, the receiver ghost may appear in the time–offset domain as a separate arrival with opposite polarity (e.g., Provenzano et al 2018)
Summary
Maximising the frequency bandwidth of recorded seismic reflection data is instrumental to obtaining optimal resolution and penetration depth within the inherent limitations of source and receiver antennas. One of the main factors hampering seismic resolution, compromising the interpretability of the subsurface imaging, is the presence of ghost reflections in the recorded wavefield (e.g., Aytun 1999; Bai et al 2013; Sun et al 2015). A ghost reflection originates at the sea-surface and interferes with the primary up-going wavefield (Fig. 1), producing notches in the recorded frequency spectrum at harmonics whose fundamental is equal to the reciprocal of the relative time delay (Aytun 1999; Yilmaz 2012). The resulting loss of bandwidth depends on the acquisition setting, namely, the deeper the receiver below the sea surface and the narrower the reflection angle, the longer the time delay and the lower the fundamental ghost notch frequency. If the time delay is longer than the wavelet duration, commonly in very-highfrequency seismic data, the receiver ghost may appear in the time–offset domain as a separate arrival with opposite polarity (e.g., Provenzano et al 2018)
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