The hydrocarbon systems of North Africa

Abstract

North Africa's hydrocarbon reserves are spread over a wide range of reservoirs and play types but derive from only a few key source rock intervals, particularly those in the Silurian, Late Cretacous and Eocene. Source rock maturity, together with the timing of the generation relative to trap forming and destructive events, seem to be the key controlling factors on success or failure at a basin level. In most cases, generation clearly post-dates trap formation, although a more complex relationship is evident in various parts of Algeria, where some traps did not form until gas was being generated. Source rock deposition and maturation can be tied to two main extensional tectonic cycles which ended in the compressional and destructive events of the Hercynian and Alpine orogenies. Remaining exploration potential in mature provinces may be tied largely to subtle and stratigraphic traps. In addition, significant frontier potential can be identified in two main fairways, corresponding to regions where Silurian/Devonian and Cretaceous/Eocene sources respectively are likely to have generated petroleum. Critical factors in these areas are timing of generation and preservation. The gas discoveries in the Ahnet Basin provide analogues for Palaeozoic generation/preservation models in the interior Silurian/Devonian source fairway. Similarly, the key to success for the Mesozoic basins of the Atlas region lies in demonstrating a favourable relationship between trap formation/destruction and generation from Late Cretaceous and Eocene source rocks.