Investigating the Factors Controlling Reservoir Quality and Introducing Flow Units of the Fahliyan Formation in One of the oilfield in the Abadan Plain, the Southwest of Iran

The Fahliyan Formation (Early Cretaceous) forms one of the main oil reservoir rocks in many oilfields in the Zagros specifically in the Dezful Embayment and Abadan Plain. For investigation of facies characteristics, depositional environment, diagenetic overprints and reservoir quality of this formation in one of the wells of an oilfield located in Abadan Plain province, the results of geological and petrophysical data including petrographic studies of thin sections, conventional core analysis and well logs were integrated. Facies analysis resulted in recognition of nine microfacies in the carbonate and two petrofacies in the siliciclastic-carbonate parts in the studied well. In addition, the carbonate microfacies were deposited in lagoon and shoal sub-environments, whereas petrofacies related to the siliciclastics dominated part falls within tidal flat environment. Based on evidences obtained in this study and comparison with the results from previous studies, it can be suggested that the Fahliyan Formation was deposited on shallow parts of a homoclinal carbonate ramp. Moreover, petrographic analysis demonstrates that diagenetic features have considerable both negative and positive effects on the reservoir characteristics and mainly regulate pore system characteristics. To identify flow units, a petrophysical method including stratigraphic modified Lorenz plot (SMLP) was applied. The results indicate that this method successfully classified the studied reservoir into discrete flow units by considering the relationship between petrophysical properties and depositional and diagenetic features. Finally, Based on SMLP method, ten flow units including four reservoir units (two speed zone and two good to fair flow units), three baffle units, two barrier units and one baffle-fair flow unit were differentiated.