Data Dependent Adaptive Deghosting -Application to Vintage Data

Raj, Abhishek; Anantan, A.; Zarkhidze, Alexander; Brice, Tim; Cunnell, Chris

doi:10.3997/2214-4609.201601217

Cited by 4 publications

(2 citation statements)

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“…With a Nyquist frequency of 125 Hz after resampling, the source-and receiver-side 'ghost' notches are mostly outside the data bandwidth (Fig. 3c), but deghosting still helps to extend the lower part of the bandwidth and removes the interference of the 'ghosts' with the primary wavelet in time domain (Raj et al 2016). A deeper towing depth would have been desirable to improve the recording of the lower frequencies and to attenuate the 'swell' noise, which is particularly strong and dominates the low frequency part of the data.…”

Section: Limits Of the Pre-processing Strategymentioning

confidence: 99%

Reprocessing 2-D airgun seismic reflection data SALTFLU (salt deformation and sub-salt fluid circulation in the Algero-Balearic abyssal plain) in the Balearic promontory and the Algerian basin

Blondel

Ford

Lockwood³

et al. 2023

Mar Geophys Res

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In an ever more challenging context for the acquisition of seismic data in the Mediterranean Sea, reprocessing to improve the quality of legacy data has become increasingly important. This work presents the newly reprocessed, open access dataset SALTFLU acquired in the Algerian basin by the National Institute of Oceanography and Applied Geophysics (OGS) in 2012. We apply a ‘broadband’ reprocessing strategy adapted for offset-limited (3 km streamer for a target 4 km below the sea level) airgun reflection seismic data acquired in deep water settings. We then assess if the reprocessed images provide new geological insights on the Mediterranean sub-surface. The workflow relies on an integrated approach combining geophysics and geological interpretation to iteratively build the velocity model. In this way we aim to tackle some of the challenges linked to imaging deep complex geological structures containing high velocity contrasts with 2-D, offset-limited seismic data. We first broaden the bandwidth of the data through multi-domain de-noising, deghosting and a source designature using an operator derived from the seabed reflection. We then perform iterative migration velocity analysis, pre-stack time migration and multiple attenuation in the Radon domain to obtain time-migrated images. The initial velocity model is derived from the resulting time migration velocities, and geologically driven model updates are generated using a combination of travel-time tomography, seismic interpretation of the major salt horizons and velocity gradient flooding. The gradient flooding aims to reproduce the large scale first-order velocity variations, while the travel-time tomography aims to resolve the smaller second-order velocity variations. The results improve our deep geological knowledge of the under-explored Algerian basin down to the base salt and the pre-salt. Fluid indicators are imaged within the Plio-Quaternary of the Algerian basin, which we interpret as thermogenic or biogenic gas sourced from either the Messinian Upper Unit or from the pre-salt, migrating through a hydro-fractured salt. The reprocessed data image lateral and vertical seismic facies variation within the Messinian units that could shed new light on the tectono-stratigraphic processes acting during the Messinian Salinity Crisis. It also reveals numerous previously unresolved volcanic structures within the Formentera basin.

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Section: Limits Of the Pre-processing Strategymentioning

confidence: 99%

Reprocessing 2-D airgun seismic reflection data SALTFLU (salt deformation and sub-salt fluid circulation in the Algero-Balearic abyssal plain) in the Balearic promontory and the Algerian basin

Blondel

Ford

Lockwood³

et al. 2023

Mar Geophys Res

View full text Add to dashboard Cite

show abstract

“…Such values broadly correspond to the combined source and receiver 'ghost' and might reflect a varying depth of the towed source or poor depth control along the streamer during the acquisition. With a Nyquist frequency of 125 Hz after resampling, the source-and receiver-side 'ghost' notches are 400 mostly outside the data bandwidth (Figure 3c), but deghosting still helps to extend the lower part of the bandwidth and removes the interference of the 'ghosts' with the primary wavelet in time domain (Raj et al, 2016). A deeper towing depth would have been desirable to improve the recording of the lower frequencies and to attenuate the 'swell' noise, which is particularly strong and dominates the low frequency part of the data.…”

mentioning

confidence: 99%

Reprocessed 2-D airgun seismic reflection data SALTFLU (salt deformation and sub-salt fluid circulation in the Algero-Balearic abyssal plain) in the Balearic promontory and the Algerian basin

Blondel

Ford²,

Lockwood³

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. In an ever more challenging context for the acquisition of seismic data in the Mediterranean Sea, reprocessing to improve the quality of legacy data has become increasingly important. This work presents the newly reprocessed, open access dataset SALTFLU acquired in the Algerian basin by the National Institute of Oceanography and Applied Geophysics (OGS) in 2012. We apply a ‘broadband’ reprocessing strategy adapted for short-offset, deep water airgun reflection seismic data and assess if the reprocessed images provide new geological insights on the Mediterranean sub-surface. The workflow relies on an integrated approach combining geophysics and geological interpretation to iteratively build the velocity model. In this way we aim to tackle some of the challenges linked to imaging complex geological structures containing high velocity contrasts with 2-D, short-offset seismic data. We first broaden the bandwidth of the data through multi-domain de-noising, deghosting and a source designature using an operator derived from the seabed reflection. We then perform iterative migration velocity analysis, pre-stack time migration and multiple attenuation in the Radon domain to obtain time-migrated images. The initial velocity model is derived from the resulting time migration velocities, and geologically driven model updates are generated using a combination of travel-time tomography, seismic interpretation of the major salt horizons and velocity gradient flooding. The gradient flooding aims to reproduce the large scale first-order velocity variations, while the travel-time tomography aims to resolve the smaller second-order velocity variations. The results improve our deep geological knowledge of the under-explored Algerian basin down to the base salt and the pre-salt. Fluid indicators are imaged within the Plio-Quaternary of the Algerian basin, which we interpret as thermogenic or biogenic gas sourced from either the Messinian Upper Unit or from the pre-salt, migrating through a hydro-fractured salt. The reprocessed data image lateral and vertical seismic facies variation within the Messinian units that could shed new light on the tectono-stratigraphic processes acting during the Messinian Salinity Crisis. It also reveals numerous previously unresolved volcanic structures within the Formentera basin.

show abstract