The effects of Qatar-Arc on the upper part of the K3 Reservoir Unit of the Upper Dalan Formation in the lower part of the Permian–Triassic Boundary: Comparison of two fields in the Central Persian Gulf Basin

Paleohighs play an important role in increasing the quality and sedimentological characteristics of the reservoirs. The Upper Dalan Formation with Late Permian age in the center of the Persian Gulf Basin is known as a giant gas reservoir. In this paper, 60 meters of the Upper Dalan Formation have been studied in two fields in the center of the Persian Gulf Basin. Petrographic studies of the two fields led to the identification of seven microfacies in field A and six microfacies in field B in the form of four facies belts in the carbonated ramp environment. In order to evaluate the heterogeneity of the reservoir, the determination of rock types was performed by using four standard methods. Examination of the average porosity and permeability shows that the dissolution in field B is more severe than in field A. Study of diagenetic processes, the type of dolomites formed and the average porosity and permeability in the samples of the two fields indicate that the location of field B on the Qatar arc leads to the formation of dolomicrites, increased dissolution and finally higher reservoir quality in microfacies groups in this field in comparison with field A.