--> Abstract: Upper Cretaceous Hydrocarbon System, Ghana, Togo and Benin, West Africa, by Ken A. Nibbelink; #90039 (2005)

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Upper Cretaceous Hydrocarbon System, Ghana, Togo and Benin, West Africa

Ken A. Nibbelink
Devon Energy, Houston, TX

Integration of recent deepwater exploration wells and new well tie 2D seismic define the Cretaceous fold belt in Ghana, Togo and Benin in a regional context. Structures began forming with the initial rifting of the South Atlantic along the Romanche Fracture Zone in the Aptian/Albian and are reactivated as late as the Miocene, however the main period of growth appears to be during the Campanian. Numerous oil slicks and seeps are observed in the area and oil is produced from Albian and Turonian Sandstones on the shelf, but discoveries made to date in the deepwater trend have not been commercial.

Isochron thicks indicate two major sources for deepwater Upper Cretaceous sediment, in eastern Benin and the Paleo Volta River. A thick Paleocene/Eocene mass transport complex is observed in Togo, but this section is missing from the Keta Arch in Ghana. The Volta Fan produced over 2.5 km of Miocene sediment.

Hydrocarbons generated from Miocene loading of the Turonian source migrate in Campanian and Maastrichtian basin floor fans under a top Cretaceous shale seal and are focused on to regional Keta Arch. Sediment patterns document the growth of the structures on the Keta Arch during the Campanian. The Cenomanian deepwater fans cut across the structures, the Campanian interval is progressively influenced by growing seafloor topography and the Maastrichtian section is ponded and deflected around the structures. A regional pinchout of the Campanian deepwater reservoirs across the Keta Arch provides the geometry for a world-class stratigraphic trap.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005