Depositional environment and biostratigraphy of the upper Sarvak Formation in Ahwaz Oilfield (Well No. 63)

Carbonate successions of the Sarvak Formation (Late Albian? To Mid-Turonian) together with the carbonate of the Ilam Formation formed the second important hydrocarbon reservoirs in SW Iran and Persian Gulf. Facies analyses were carried out on the upper parts of the Sarvak Formation in western part of the Ahwaz Oilfield (AZ-63 well) to interpret depositional environment. Lithologically، the upper part of Sarvak Formation is composed of clean to argillaceous limestones، which have been partly dolomitized in some intervals. Based on this study، 15 microfacies were identified that are grouped into 6 facies associations، deposited in a homoclinal ramp-like carbonate platform in the studied well. Facies distribution is also investigated in the suggested depositional model using the frequency pie-diagram. Biotratigraphic studies were carried out on microfossils of the Sarvak Formation and resulted in presentation of three biozones including Nezzazata-Alveolinid assemblage zone (Cenomanian)، Rudist debris zone (Cenomanian-Turonian) and Moncharmontia apenninica-Nezzazatinella-Dicyclina assemblage zone (Turonian). These are closely correlated with the biozonation scheme of Wynd (1965).