Bulletin du Service Géologique de l'Algérie
Volume 8, Numéro 1, Pages 55-70
1997-06-01

Sedimentological Evolution Of The F3 Sandy Bar Of The Western Alrar Field (eifelian - Givetian), Illizi Basin, Algeria

Authors : Chaouchi Rabah . Malla Mohand Said . Kichou Fatiha .

Abstract

Commercial accumulation of hydrocarbons depend on several factors, among which sedimentological conditions are of prime importance. Effects of such conditions have been observed on a mainly sandy reservoir of Givetian- Eifelian (Middle Devonian) age, within the western part of the Alrar field. Frequent variations of the reservoir characteristics are present within the area. Previous studies have failed to produce a coherent model capable of explaining observed patterns of hydrocarbon distribution and entrapment within the West Alrar field. A previous sedimentological model incorporates new well data and helps explain these patterns, though the southern limit of the F3 remains largely hypothetical. We believe that, in Alrar, the reservoir was deposited as tidally influenced littoral bars. These are elongated in a NW-SE direction with an interbar area in the vicinity of well DZ-1. Based on this model, four possible sedimentological interpretations of the extention of the F3 reservoir to the south and west have now been developed. The pinch out also seems to be related to the rapid thinning out of the section in this direction and to active faulting and uplifts at the time of deposit.

Keywords

Alrar - Devonian - Reservoir - Evolution of the bars