The Asmari and Jahrum formations are studied in terms of microfacies, depositional environment, and diagenesis in the Gulkhari oil field based on data provided from well nos. 2, 10, and 11. Petrography, fauna content, biofacies, and depositional textures lead to recognition of 21 carbonate microfacies and 3 non-carbonate lithofacies which were deposited in four depositional environments including tidal flat, lagoon, bar, and open marine on a homoclinal ramp. Dissolution, bioturbation, cementation, neomorphism, silisification, micritization, physical compaction, and dolomitization affected on the Asmari and Jahrum formations, of which cementation, dolomitization, and dissolution are most prominent. Evidently, cementation reduced reservoir quality whereas dolomitization, dissolution, and burrowing, promoted porosity development of the reservoir. Diagenetic processes points toward uplift and a set of syngenetic processes on seafloor and epigenetic processes during shallow to deep burial. Consequently, the microfacies with improper reservoir quality were subjected to subsequent porosity development through diagenetic processes.
