Sedimentological and diagenetic controls on reservoir properties in the Permian–Triassic successions of Western Persian Gulf, Southern Iran

Abstract

The Permian–Triassic intervals in the Arabian Plate, namely the Khuff Formation and its equivalents, Dalan and Kangan formations, are among the most important gas reserves in the word. In Iran, they were the subject of several studies, which mainly focused on the supergiant South Pars Field. This study provides informations on the facies characteristics, diagenetic features and reservoir properties of these intervals in the western Persian Gulf (Golshan Field). As well, characteristics of the lower Dalan Member were evaluated for the first time from the Iranian sector of the Persian Gulf. Results of this study revealed the combined effects of depositional processes and diagenetic overprints on the reservoir quality of these intervals. Among the various diagenetic processes, anhydrite and calcite cementation has intense destructive effects on the reservoir quality of precursor porous facies. On the other hand, dolomitization has different effects on the reservoir quality. It has a positive effect, if it is not concomitant with overdolomitization and anhydrite cementation. Results of this study reveal that there is a close relationship between the depositional facies and diagenetic processes in the Dalan–Kangan sequences. Therefore, different reservoir/non-reservoir units of these intervals can be traced in a sequence stratigraphic framework. In order to constructing a sequence stratigraphic model, as a basis for geological reservoir model, various orders of sequences (third to fifth/sixth) were differentiated and correlated across the giant Golshan Field and supergiant South Pars Field.