Study of Microfacies, Sedimentary Environment and Sequence Stratiography of Fahliyan Formation in Abadan Plane Oilfield

The Fahliyan Formation belonging to Khami Group is a main reservoir rock in Abadan Plane oil fields¡ and this formation is related to Neocomian age. Thickness of this formation in studied wells is about 580 meters. In the Abadan Plane¡ the Fahliyan Formation transitionally overlays the argillaceous limestone of the Garu Formation and its upper boundary transitionally changes into marl and argillaceous limestone of the Gadvan Formation. Petrographic studies of thin sections have been prepared from cuttings and cores resulted in to recognition of 13 microfacies and 2 lithofacies. This formation consists of two carbonate and mixed carbonate –detritalclastic (mixed zone) members. The carbonate member deposited in various sub-environment of basin¡ outer/mid ramp and inner ramp and the mixed member is composed of 3 parts: clay¡ sand beds and argillaceous limestone. Apparently¡ the sedimentary sequences of the carbonate member deposited in a homoclinal ramp¡ containing important shoal facies and lagoon expansion. The mixed member sucession shows shallow marine carbonate features along with claystone and thin sand beds. The Fahliyan Formation consists of three type 3 sequences with sb2 sequence boundary where termination of sb3 in mixed zone changes into sb1 in the Gadvan Formation.