Katrina Coterill¹, Gabor Tari¹, Paul Ashton¹, Philip Thomson¹

(1) Vanco Energy, Houston, TX

ABSTRACT: Three-dimensional Seismic Facies of Submarine Channel Systems in Variable Tectonic Settings along the Deepwater West Africa Margin

Recent exploration in deepwater West Africa has resulted in numerous significant discoveries. Angolan discoveries are primarily associated with Oligo-Miocene age submarine channel-fan systems. Discoveries in Equatorial Guinea include Upper Cretaceous channelized-ponded turbidites. Consequently, the success of each discovery is directly related to the character of its channel system. One method used to predict channel character is seismic facies calibration. Three-dimensional seismic facies and corresponding lithofacies found in well penetrations are assumed analogous to similar facies from similar depositional environments. However, variations in three-dimensional seismic facies may be best used as a predictive tool when examined in the context of tectonic setting.

The Oligo-Miocene channel-fan systems of Angola vary their character with depositional environment and timing relative to structural development. The three-dimensional seismic facies of these systems also vary according to these parameters. Ultimately, mobilization of channel-fan systems onto ductile salt structures produces hydrocarbon traps. Deepwater Gabon provides a relatively untested salt tectonic setting for comparison. The two systems display similar three-dimensional seismic facies. However, the scale of similar seismic facies differs between the two areas.

Alternatively, Upper Cretaceous ponded turbidites have recently proved successful in Equatorial Guinea. Submarine channel systems play a significant role in both reservoir deposition and trap formation. Although structures are produced by salt tectonics, their nature is strongly influenced by their transform setting. Northern Namibia provides a second, relatively untested province for comparison. The three-dimensional seismic facies of these systems differ in scale and character - both from each other and among other West African areas.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado