Sedimentology Evolution of the Sandy Bar of Givetian - Eifilian F3 of Western Alrar - Illizi Bassin, Oriental Sahara - Algeria

R. Chaouchi, MS. Malla

The conditions of the sedimentation are an important factors for the accumulation of the hydrocarbons.

The sandy reservoir F3 of Alrar West belong to the Paleozoique detritic series (Middle Devonian) of Eifilian and Gevitian age, composed of sand-clay set. Which presents variations in the characteristics of the very variable reservoirs.

The studies done up to day in sedimentology, structurale, diagenesis, and geochemistry did not permit the exploration for the accumulation of the fluides in the Alrar West structure. This is why the sedimentology model of SOMMER has been reviewed and corrected thanks to datas recolted from the recent drillings (from A128 up A136). In the fact the extention limit of F3 traced by Sommer to the South seems to be hypothetic. In reality at Alrar we are in presence of two tidal bars elongated according to NW - SE direction with an inter-bar next to the well DZ-1.

There has been established, also, 4 sedimentologic hypothesis on the extension of F3 to the West. The evolution, particularly of the F3 ALRAR WEST, happens in an environment of littoral bar of tidal influence, and the pinching out to the South and West seems to be related the rapid thinning out of the thicknesses, and sometimes to the accidents and sudden uplifts of the floor.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995