Cretaceous Fan Plays of the African Transform Margin
Regional Geologist, Kosmos Energy
The tectonic evolution of the West African transform margin has resulted in rapidly varying subsidence, thermal and basin fill histories for each for sub-basin, causing considerable variations in how the hydrocarbon play elements stack. The discovery of the Jubilee Field in 2007 opened up the Late Cretaceous play and was followed by a large increase in exploration drilling activity throughout the margin. Since the Jubilee discovery in 2007, 39 exploration wells have been drilled along the margin resulting in 21 discoveries. To date, there is only one additional sanctioned development which is also located in the Tano Basin. A significant number of these exploration wells have encountered live hydrocarbons indicating the presence of an extensive working petroleum system throughout large parts of the transform margin. However, limited commercial success to date beyond the Tano Basin appears to be associated with a combination of reservoir and trap/seal issues. The success of the play in the Tano Basin may be associated with its structural configuration. This is strongly associated with a suite of NW trending extensional faults connecting the St. Paul and Romanche FZ's and by NE oriented transpressional highs associated with movement on the transforms. This structural fabric creates intra-slope highs and lows and may help reduce bypass of the reservoir systems to the ultimate basin floor. This appears to have happened in many of the other transform basins. Trapping of the sands further up systems tract has helped to juxtapose good reservoir fairways with the part of the basin most likely to yield combination and pinch-out traps.
AAPG Search and Discovery Article #90204 © AAPG Geoscience Technology Workshop, Stratigraphic Traps and Play Concepts in Deepwater Settings, May 14-15, 2014, Rio de Janeiro, Brazil