Rock Typing Determination of the Dariyan Formation for Reservoir Evaluation in the Framework of Depositional Sequences in an Oilfield in the Eastern Persian Gulf

The Dariyan Formation with the Aptian age is one of the most important prolific oil reservoirs in the Zagros and Persian Gulf. In the current study, different rock typing approaches were integrated and applied for the reservoir characterization of this formation in an oil field in the eastern Persian Gulf. Petrographic studies on the thin sections of the studied formation have led to the recognition of nine microfacies grouped into four sub-environments, including basin, outer, middle and inner ramp. The observed facies indicate a carbonate ramp as the depositional environment of the Dariyan Formation. The most important diagenetic processes observed in thin sections are dissolution, dolomitization, fracturing, micritization, (mechanical and chemical) compaction, and bioturbation. Based on the porosity-permeability of cores, six hydraulic flow units (the flow zone indicators = FZI method), four Winland rock types, and three Lucia rock classes were identified. Predicted porosity and permeability from log data were used to identify five hydraulic flow units (from the FZI method) and based on the stratigraphic modified Lorenz plot (SMLP), six reservoir/non-reservoir units were identified. In addition, using the multi-resolution graph-based clustering (MRGC) technique, seven electrofacies were determined. A comparison between the results of all rock-typing methods and petrographic data also reveals close correspondence. In a general view, the reservoir potential of the Dariyan Formation is higher in the Highstand System Tracts, which are mainly composed of grain-supported fossil-bearing and boundstone facies of the inner ramp sub-environment that could be a target zone for the field development. In contrast, the mud-dominated facies of the basin and outer ramp sub-environments in the Transgressive System Tracts are the poor reservoir units within the Dariyan Formation.