Reviving Old Seismic Data Using Latest Broadband Processing Technology - A Case Study from West Of Shetland

Lille, H. Toubiana; Gigou, G.; Vivin, L.; Rebert, T.; Baillon, S.; Rivault, Jean-Louis; Smadja, L.; Palmer, J.; Krishna, Hari; James, G.

doi:10.3997/2214-4609.201700814

Cited by 3 publications

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“…Common goals of reprocessing are to improve the data bandwidth, spatial resolution, signal-to-noise ratio, reflector continuity and, where relevant, seismic-borehole correlations (Sadhu et al 2008;Lille et al 2017). In this study we aim to better image the salt structures, particularly the base salt, previously interpreted from the legacy processing as a flat surface lying around 2.7 km below the seafloor, at a water depth of 3.2 km (Dal Cin et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…Compared to traditional 'narrowband' seismic processing, 'broadband' processing aims to improve the spectral accuracy by expanding the data bandwidth and restoring frequency content attenuated by the source-and receiverside 'ghost' effect and by seismic absorption (Masoomzadeh et al 2013;Lille et al 2017). High frequencies are most strongly affected by seismic absorption, which preferentially attenuates the highest frequency parts of the spectrum (Futterman 1962;Sams et al 1997).…”

Section: Introductionmentioning

confidence: 99%

“…High frequencies are most strongly affected by seismic absorption, which preferentially attenuates the highest frequency parts of the spectrum (Futterman 1962;Sams et al 1997). Recovering this information improves the resolution and results in more accurate true amplitudes, improving the performance of other data processing steps such as velocity model estimation and migration, and quantitative interpretation such as amplitude variation with offset (AVO) analysis, impedance inversion, and attribute analysis (Chopra and Marfurt 2007;Mavko et al 2009;Amundsen and Zhou 2013;Lille et al 2017). Conversely, lack of low frequency signal commonly results in poor focusing in the deep part of the section, as low frequencies suffer less from scattering and absorption, so they penetrate deeper and display a better trace-to-trace moveout coherence, allowing us to build a more accurate velocity model (ten Kroode et al 2013).…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…The method is applied to a West of Shetland marine dataset recently reprocessed (Toubiana et al, 2017). We first briefly describe the applied tomography-based velocity model building workflow.…”

Section: Introductionmentioning

confidence: 99%

Tomographic model uncertainties and their effect on imaged structures.

Reinier¹,

Messud²,

Guillaume³

et al. 2017

79th EAGE Conference and Exhibition 2017 - Workshops

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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

Lockwood

et al. 2022

Preprint

View full text Add to dashboard Cite

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 (3km 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.

show abstract

Reviving Old Seismic Data Using Latest Broadband Processing Technology - A Case Study from West Of Shetland

Cited by 3 publications

References 0 publications

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

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

Tomographic model uncertainties and their effect on imaged structures.

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

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