Sedimentology and Reservoir Characterization of the Qom Formation, Central Iran Basin

ABSTRACT The Qom Formation has been considered as a significant reservoir succession in Central Iran forming various hydrocarbon fields. The geological data from four wells from the two hydrocarbon fields (I and II) have been investigated for a reconstruction of sedimentary and diagenetic environments as well as reservoir quality of the Qom Formation in southeast and northwest of the Qom city. This formation consists of 15 depositional facies in nine facies groups. Concerning to abrupt facies changes, reef facies and high-energy facies (grain-supported) we propose shelf carbonate platform as a sedimentary environment for the Qom Formation in the studied area. The presence of reworked inner platform to deep-water facies, confirm the result. Cementation, dissolution, dolomitization, and fractures are the most significant diagenetic processes that have affected reservoir quality. These features are formed in three major diagenetic settings including marine, meteoric, and burial environments. Interparticle, fenestral and fracture porosities are the most common types of porosities in this formation. The essential relationships among the porosity and permeability show positive effect of porosity on a reservoir quality except for mud-supported facies. On the other hand, mud-supported facies have a low reservoir quality relate to the grain-supported facies. The reservoir characteristics of the Qom Formation are dominantly affected by diagenetic events, so diagenetic studies and identification of diagenetic zones in field-scale are the most important part in reservoir quality studies.