Depositional–diagenetic history and sequence stratigraphy of the Upper part of Sarvak Formation in hydrocarbon fields of the central and southern Dezful Embayment, SW Iran

Cenomanian –Turonian carbonate sequences of the upper Sarvak Formation are among the most important hydrocarbon reservoirs of the Zagros area in SW Iran. Depositional and diagenesis histories were investigated using the petrographic studies of core samples and thin sections of this formation in 6 wells from 5 oilfields located in central and southern parts of the Dezful Embayment. Facies analysis has resulted in the recognition of 14 microfacies that are grouped into six facies associations (basin, outer ramp, middle ramp, open marine lagoon, shoal, and restricted lagoon), according to their facies characteristics and comparison to the standard microfacies models. A homoclinal ramp model was proposed as depositional setting of the Sarvak Formation. Important diagenetic alterations of this formation include dissolution, cementation, dolomitization, de-dolomitization, silicification, neomorphism, compaction, and fracturing. They represent a paragenetic sequence of marine, meteoric (eogenetic and telognetic), and shallow- to deep burial realms. Sequence stratigraphic interpretations resulted in the differentiation of two (third-order?) depositional sequences in the upper Sarvak Formation (mid Cenomanian – early Turonian). Finally, facies characteristics and diagenetic alterations are interpreted in a sequence stratigraphic framework.