Investigation of facies and sedimentary environment of Qom Formation in Sarajeh gas field and Yurtshah aquifer (Qom, Central Iran basin)

The Qom Formation is considered as one of the most important reservoir formations in Central Iran. This study was conducted to identify the facies and sedimentary environment of this formation in Sarajeh gas field and Yurtshah aquifer which are located in the southeast and northeast of Qom, respectively. 15 sedimentary facies were identified after examining the Qom formation-related thin sections and cores in the study area, which can be divided into 9 belts or facies groups according to standard models. According to the characteristics of the studied samples, the expansion of turbidite deposits and the frequency of reef / shoal facies, the paleoenvironment of Qom Formation in Sarajeh Field and Yurt-e-shah Aquifer is a carbonate shelf. Facies related to deep sections are less frequent, so the paleo-position of the two fields under study has been shallow sections of the platform.There are three main features in the facies identified in the study areas that have not been introduced in other sections and other studies of the Qom Formation, including the presence of supratidal facies (especially anhydrite facies), the continuous reef sequences and the existence of facies has planktonic foraminifera. The most complete sequence of the Qom Formation is related to Sarajeh field, but in Yurtshah Square this sequence is not complete and also shows less thickness. The ancient position of Sarajeh field was an depression and the Yurtshah anticline was an paleohigh. These conditions have led to thickness changes in the the Qom Formation even in the regional dimension.