میکروفاسیس و محیط بخش 5 سازند گچساران درمیدان نفتی منصورآباد

Abstract

The Gachsaran Formation were identified as a Cap rock of Asmari oil reservoirs in the Zagros basin which is extended from Dezful Embayment-Lorestan to Persian Gulf basin. . The thickness of the constituent parts reduced gradually from the base to the top and major lithology this member consists of anhydrite, gray and red marl, salt and inter bed limestone. Petrographic study of the member indicating nodular, replacement, enterolitic, porphyroblastic, fluvial, spherolitic, bird eyes (honey nest) and match stick diagenetic textures. The petrographic studies identify three facies belt suprataidal areas, Intertidal, lagoon environments that all of them are related to the area behind Ramp a carbonate platform. Vertical variation of micro fossil describes a vast area sabkha-agoonal depositional environment for ember 5 that in each prograd of sea, deposited marl and carbonate in lagoon environment and non fissile mudstone in intertidal area. The increased evaporation caused a regression phase that resulting in expanded anhydrite (gypsum) in a sabkha environment. . Receding sea in the last stages, leading to the form a salt pan where salt layers are deposited. The importance of Ghachsaran formation as a Cap Rock in oil and gas reservoir and its basic role as a boundary between high pressure and low pressure formations (casing point) has led to this formation be considered in sedimentology and stratigraphy studies.