new procedure for evaluation of cap rock across the oil fields in sedimentary basin in sw iran

TL;DRAbstract

Due to samples crushing during drilling program, correlation and subdivision of cap rock in a sedimentary basin, to understand for location of casing points, are difficult. The Gachsaran Formation is a cap rock for the Asmari reservoir in Zagros petroliferous basin of SW Iran and is mainly composed of evaporite (anhydrite, gypsum), marl and mostly gypsiferous shale. Six key beds have been identified in the lowermost part of this interval in the cap rock including A, B, C, D, E and F. Two different anhydrite units are present at the upper part and one in the cap rock unit as stated is in the lowermost parts of this formation. In addition to sedimentologic (thin sections of cutting), stratigraphic and petrophysical studies, a semi quantitative analysis has been carried out by SEMEDS to differentiate the anhydrites and introduce the new key beds. Based on our study, the upper anhydrite unit contains a large amount of Na, Cl, Ba and Ti, while the lower anhydrite unit in the cap rock contai

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