Nyanga Basin

The formation of the Nyanga, Gabon, Douala and Rio Muni basins along the west coast of Africa began in the Early Cretaceous, during the breakup of Gondwana and subsequent opening of the South Atlantic Ocean. Early rift sediments include the Barremian age Melania shale, a rich lacustrine source rock which has an average TOC of 5-6% with local maximums of 20%. Later rift deposits include reservoir quality sediments accumulating in the fluvial-lacustrine deltaics of the early Aptian Dentale formation. A transitional erosion and peneplanation phase followed rifting, culminating in a marine transgression during which the Gamba sandstone, the principal reservoir in the Gamba field, was deposited. This was followed by a period of salt deposition during the late Aptian, during which approximately 500m of Ezanga salt was accumulated. The pre-salt section has all the ingredients for a successful petroleum system and this is confirmed by the number of discoveries made since the 1970s.