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S. R. Lawrence1,
A Soulsby2,
R. J. Bray2
(1) Exploration Consultants Ltd, Henley-on-Thames, United Kingdom
(2) Exploration Consultants Ltd
Abstract: New prospects in the Gulf of Guinea post-rift petroleum system (Equatorial Guinea and Cameroon)
Recent deepwater licensing rounds in the Gulf of Guinea have focused attention on the emerging Cretaceous post-rift play. Here, the post-rift section comprises "transitional" (Aptian-Albian) and "early drift" (Cenomian-Santonian) sequences. Good oil-prone source rocks are proven in the Aptian-Albian section and are inferred in the Cenomanian-Turonian section from regional extrapolation and geochemical data from reservoired oils and surface seepages.
An important post-rift structural episode occurred in the Santonian, involving transform reactivation and differential uplift causing extensive gravity-sliding. Large scale gravity-slide features characterize large areas of offshore Rio Muni and southern Cameroon. Cessation of this structural event is demarked by the "Senonian Unconformity".
The Kribi oil and gas and Sanaga Sud gas/condensate fields occupy gravity-slide structures. Hydocarbons probably migrated from source rocks in downdip/subjacent intra-gravity-slide or downdip extra-slide locations. Hydrocarbon type and quality can be explained by laterally-varying maturity histories. In deepwater locations, in front of gravity-slides, less complex burial and maturity history is dominated by post-Senonian unconformity burial. Source rocks here are in "late oil" to gas mature conditions, favourably located below predicted reservoir development within seismically defined Upper Cretaceous and Lower Tertiary base-of-slope/basin-floor fan systems.
Much oil remains to be discovered from this post-rift petroleum system in the deep water Gulf of Guinea region.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana