Microfacies and sedimentary environment of the Shahbazan Formation in well no. 3 of the Qhaleh Nar oil field

In this study¡ microfacies and depositional environment of the Shahbazan Fromation are investigated in well no. 3 of the Qhaleh Nar oil field (SW Lurestan). The thickness of the Shahbazan Formation in the studied well is 228 meters. This formation consists mainly of limestone and dolomite. The lower boundary of the Shahbazan Formation with the Pabdeh Formation is conformable and its upper boundary with Asmari Formation is marked by an unconformity. The Shahbazan Formation in the studied well is considered middle Eocene (early Lutetian) to late Eocene (Priabonian) in age. Fourteen microfacies types were distinguished based on their depositional texture¡ petrographic analysis and fauna in the studied well. The sediments were deposited in open marine¡ bar and lagoon subenvironments. Based on distribution of microfacies¡ it seems that the lower and upper parts of the Shahbazan Formation were deposited in two types of carbonate settings. The lower part was deposited in an open shelf setting¡ while¡ a homoclinal ramp were recognized for the upper part. The lower and upper parts of the Shahbazan Formation can be divided into two subenvironments¡ middle and outer shelves and middle and inner ramps¡ respectively. The production rate and diffusion coefficient and the tectonic conditions are the effective factors on the evolution of the platform from an open shelf setting to a homoclinal carbonate ramp .