Abstract: The Hydrocarbon Systems of North Africa

Duncan S. MacGregor, David G. Dalton, Ian R. Vann

Over 90% of the reserves in the North African region derive from only three source rock intervals. The Palaeozoic-Triassic play fairways of Algeria, Tunisia and Libya are charged mainly from the regionally developed basal Silurian source rock, deposited within a series of sag basins during transgression. Source rocks in the late Cretaceous and Eocene were deposited along the North Tethyan margin within restricted basin settings and as regional transgressive systems, and were possibly augmented in quality by oceanic anoxia and/or upwelling. A wide stratigraphic range of reservoirs are sourced from these levels, though all are in demonstrable lateral communication with the source rock. The most prolific setting is within the Sirte basin of Libya where tilted fault blocks and overlying s mple drape structures provide effective traps with negligible leakage to surface.

Source rock development and maturity together with the timing of structuring relative to migration seem to be the key controlling factors on basin success or failure. The Silurian source system, key to success in the Palaeozoic basin setting, extends through several underexplored interior basins in Algeria and Libya. A critical factor in these areas is the relationship between timing of migration and the Hercynian orogeny, which may have destroyed most pre-existing oilfields. Similarly, the key factor in developing attractive prospects in the Atlas basins will be in demonstrating a favourable relationship between structuring and expulsion of oil from the late Cretaceous source rock which should extend through the area.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994