New Insights from CongoSpan Pre-Stack Depth Migrated Imaging in Angola-Congo-Gabon: Petroleum Systems and Plays

Henry, Steven G.; Danforth, Al; Venkatraman, S.

doi:10.5724/gcs.05.25.0731

Cited by 3 publications

(3 citation statements)

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“…Henry et al 2005) in the North Kwanza Basin (Fig. 3), some researchers assuming that this is also true in the South Kwanza Basin (e.g.…”

Section: Sag Intervalmentioning

confidence: 94%

“…Beyond the CSA, south of the Florianopólis Fracture Zone, Barremian-aged oceanic crust is present outboard of the Walvis (Namibia) and Pelotas (Brazil) basins (Fig. 3); to the north of the Luanda Fracture Zone lie significantly thicker Aptian pre-salt strata (Henry et al 1995(Henry et al , 2005, as well as putative Barremian oceanic crust ( Fig. 3) outboard of the North Kwanza (Angola) and Espirito Santo (Brazil) basins.…”

Section: Study Areamentioning

confidence: 97%

“…Now, however, new seismic technologies and multiple well data have significantly advanced our geological knowledge and produced high quality sub-salt images, such as those resulting from pre-stack depth migration (e.g. Henry et al 2005;Davison et al 2012), a technique where seismic reflections are placed in their correct sub-surface positions using iterative velocity models replicating the ray paths taken by the seismic energy. Here we will describe key features in an example from a very large twodimensional (2D) seismic survey covering the Brazilian Santos and Campos basins (350 000 km 2 ) on the western side of the CSA, a region conjugate to the Namibe, Benguela and South Kwanza basins (Angola) on the eastern side of the ocean.…”

Section: Pre-salt Stratigraphy and Structurementioning

confidence: 99%

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Rifting, subsidence and continental break-up above a mantle plume in the central South Atlantic

Quirk

Hertle

Jeppesen

et al. 2013

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New seismic and well data in the deep-water basins of Campos, Santos, South Kwanza and Benguela, supported by plate reconstructions, help answer fundamental questions on the rifting history of the central South Atlantic, specifically on the amount and effect of fault-related deformation, and on when and where sea-floor spreading started. The Paraná mantle plume played a fundamental role -dynamically raising the plate, prolonging continental rifting by heat-softening the crust and, after break-up, delaying the onset of marine conditions. Previous discrepancies in extension and subsidence have been solved, and the location and age of the continent-ocean boundary can now be determined. Rifting involved approximately 450 km of homogeneous pure shear, equivalent to a b factor (lithosphere stretching factor) of 4.5. Break-up occurred at 123 Ma (Barremian-Aptian boundary), 7-8 Ma later than the southern South Atlantic but 6 Ma before widespread salt deposition. The mid-Atlantic ridge was initially subaerial, marked by a volcanic high. Sea-floor spreading was at a rate of 24 mm year 21 , similar to syn-rift deformation prior to breakup. Transcontinental strike-slip shear zones are not evident but a major NW-SE lithospheric lineament associated with a failed triple junction arm had a major influence on the magmatic history, both prior to and after break-up.

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“…Henry et al 2005) in the North Kwanza Basin (Fig. 3), some researchers assuming that this is also true in the South Kwanza Basin (e.g.…”

Section: Sag Intervalmentioning

confidence: 94%

Section: Study Areamentioning

confidence: 97%

Section: Pre-salt Stratigraphy and Structurementioning

confidence: 99%

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Rifting, subsidence and continental break-up above a mantle plume in the central South Atlantic

Quirk

Hertle

Jeppesen

et al. 2013

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Salt interpretation enabled by reverse-time migration

Buur

Kühnel

2008

GEOPHYSICS

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Many production targets in greenfield exploration are found in salt provinces, which have highly complex structures as a result of salt formation over geologic time. Difficult geologic settings, steep dips, and other wave-propagation effects make reverse-time migration (RTM) the migration method of choice, rather than Kirchhoff migration or other (by definition approximate) one-way equation methods. Imaging of the subsurface using any depth-migration algorithm can be done successfully only when the quality of the prior velocity model is sufficient. The (velocity) model-building loop is an iterative procedure for improving the velocity model. This is done by obtaining certain measurements (residual moveout) on image gathers generated during the migration procedure; those measurements then are input into tomographic updating. Commonly RTM is applied around salt bodies, where building the velocity model fails essentially because tomography is ray-trace based. Our idea is to apply RTM directly inside the model-building loop but to do so without using the image gathers. Although the process is costly, we migrate the full frequency content of the data to create a high-quality stack. This enhances the interpretation of top and bottom salt significantly and enables us to include the resulting salt geometry in the velocity model properly. We demonstrate our idea on a 2D West Africa seismic line. After several model-building iterations, the result is a dramatically improved velocity model. With such a good model as input, the final RTM confirms the geometry of the salt bodies and basically the salt interpretation, and yields a compelling image of the subsurface.

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