Evans, Douglas G.1
(1) WesternGeco, Gatwick Airport, United Kingdom
ABSTRACT: Subsurface Deposition on the Abyssal Plain of the Congo Fan
The Congo Fan of Angola shows evidence of extensive subsurface sand deposition from the
Oligocene onwards. This sand deposition extends beyond the recent Tertiary deepwater
discoveries such as Plutao in the salt diapir province, onto the abyssal plain. This area,
outboard of Angolan Blocks 31 & 32 has been covered by recent 3D seismic data sets in
‘ultra’ deep water of 3km and more. These data will be used to show that sand
deposition is clearly identifiable and continues into this ‘ultra deep’
province, extending the Tertiary play fairway westwards for a considerable distance.
By using these data, the morphology of differing styles of sand deposition can be shown in a variety of ways including amplitude extraction, timeslices, opacity and 3D visualisation.
In the ultra deep province of offshore Angola it can also be demonstrated that the Cretaceous and early Tertiary on the abyssal plain shows little or no seismic evidence of sand deposition. However, this section is a prime candidate to contain mature source rocks, the evidence for which can be demonstrated by the ‘DHIs’ seen in the overlying sands. Levels of source rock maturity will also be discussed.
The abyssal plain is at first sight the ultimate location for the ‘subtle’ i.e. stratigraphic trap, however, closures can also be shown to exist as drapes over basement features and allochthonous salt bodies.
All these elements combine to show that this area of offshore Angola has the potential to be a major new petroleum province of the near future.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.