--> Abstract: Submarine Fan and Turbidite Deposits Dominated Reservoirs in The Upper Illizi Basin Ordovician (South Eastern Algerian Sahara), by H. Abdallah; #90923 (1999)

Datapages, Inc.Print this page

ABDALLAH, HUSSEIN, Sonatrach, Division Exploration, Bat. C, Av. 1er Novembre, Boumerdes, Algeria

Abstract: Submarine Fan and Turbidite Deposits Dominated Reservoirs in The Upper Illizi Basin Ordovician (South Eastern Algerian Sahara)

The sedimentologic characteristics of the Upper Ordovician deposits in Illizi basin are clearly different from those of the other detrital saharan Paleozoic deposits. They include conrasting lithologies, rapid and numerous variations in sediment thickness, unique sedimentary structures, down cutting and channeling aspect. A more careful study of the facies associations combined to a sequence stratigraphy analysis reveals that the Upper Ordovician sediments corespond to turbidites deposited during a low sea-level period. The important canyon network filled by these sediments is tectonically controlled.

Two fan models are encountered in Illizi basin. The first one is clearly illustrated by the wonderful Ordovician outcrops in the Tassili N'Ajjer area: wide and deep canyons acted as conduits for mass transport complexes and turbidity currents. Due to ancient synsedimentary basement fault reactivation, only the southern basin part seems to be concerned by this model. The fine-grained sediments infilling the canyons have very poor reservoir properties. But, in the northern part of the basin, sheet-like turbidites overlain by channel-levee systems seem to be present. Oil and gas are produced from the uppermost good reservoir sandstones, just beneath the hot Silurian shale which is the main and prolific source rock. Unfortunately, to date the available seismic quality does not allow to mapping the sand bodies geometry which are 20 m thick and, probably, laterally shingled. It means that hydrocarbon exploration should be re-oriented towards this new kind of leads. 

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England