Facies, Depositional Environment and Sequence Stratigraphy of Dalan Formation in Persian Gulf (Qatar-South Fars Arch) Well SP-A Subsurface Section

Objectives: Facies, depositional environment and sedimentary cycles of Dalan Formation in the South Pars gas field are the aspects that this paper is focused on. Methods/Statistical Analysis: Three hundred and seventy-eight thin-sections prepared from cutting and cores were evaluated by using petrographic microscope. Corel Draw X6, Autodesk Map, Corel Photo-Paint, Autodesk Map, DN2 Microscopy Image Processing System, Geocalc and Auto Cad 2014 employed for this research. Findings: Twenty-four major facies in five facies associations were identified comprising Tidal flat (A), Lagoon (B), Shoal (C), Open marine (D) and Mid ramp (E). The Dalan Formation was deposited in inner to mid parts of a homoclinal ramp. The sequence stratigraphy studies revealed the seven main third– order sedimentary cycles in the well SP-A. The shoal ooid grainstone facies with intergranular, moldicand fracture porosity comprise the main reservoir facies of the Dalan Formation. Dissolution, dolomitization, anhydritization, compaction and cementation are the main diagenetic processes in this formation which played an important role in the quality of the reservoir. Applications/Improvements: The results obtained from this paper, can be used to construct a major depositional framework in the Qatar-South Fars Arch for later exploration purposes.