Jurassic-Early Cretaceous sandstones of the Sarir Group (viz. Nubian) host in excess of 16 billion barrels oil-in-place in the southeast Sirt Basin. The sequence comprises four members, which can be correlated on a regional basis. Cyclical deposition of erosive sandstones, each reflecting a relatively rapid drop in the base level of erosion, relate to a fall in sea level to the north. Intervening shales denote gradual transgressive events with landward ponding of drainage lines. The upper shale provides both source and seal for intra-Sarir oil pools in the Metem Depression.

The most important Sarir Group petroleum system relies on post-rift Tethyan shales to act as both source and seal to the underlying syn-rift Sarir Group reservoirs. The Sarir Group itself and major normal faults provide the main conduits for migration.

The Messla High occurs at the intersection of two structural (rift) trends and it remained dominantly rigid during syn and post rift sedimentation. The Calanscio High has a more complex structural history. Both highs were foci for oil migration from the cognate troughs during the Palaeogene. The main plays are stratigraphic (Messla field), structural (Sarir-C), hanging wall fault traps (UU1-65, VV1-65) and horst blocks (Calanscio field). Lateral and vertical seal on bounding faults is a key to entrapment as wrenching, together with dip slip, encouraged the formation of fault gouge. Juxtaposition of thick Tethyan shales across the fault plane is also a pre-requisite for fault seal.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas