Characteristics of Carbonate Microfacies and Sedimentary Environment of the East Margin of Caspian Basin in the Carboniferous KT-II Layer: A case from Zanazor area

Key words: 
• Caspian basin /
• Zanazor /
• Carboniferous /
• KT-II layer /
• microfacies

Abstract: In order to solve the problem of reservoir heterogeneity in Carboniferous KT-II carbonates in Zanazor on the eastern margin of the Pre-Caspian basin, the internal sedimentary models of sedimentary microfacies are characterized more detailedly and meticulously. The results show that:①The carbonate rocks of the Carboniferous KT-II in the study area are dominated by sparry grainstones, followed by packstones and mudstones. ②According to the different sedimentary characteristics and depositional environment, carbonate sediments can be divided into tidal flat, shoal and depression. Based on the characteristics of water depth, hydrodynamic condition and salinity, the carbonate shoal is divided into two kinds of microfacies:the break-wave shoal and up-wave shoal. According to their composition, the carbonate shoal is subdivided into four types:fusulinids shoal, foraminifera shoal, algal shoal and oolitic shoal. ③According to Wilson's idealized carbonate model, the study area belongs to the interior sedimentary area of the open platform, and corresponds to the Irwin's epicontinental sea energy model. The tidal flat corresponds to the Z-zone close to the coast; the shoal corresponds to the the Y-zone near the coast; and depression corresponds to the X-zone far from the coast.