Facies analysis and diagenetic processes of the albian-turonian carbonates of the Sarvak formation in Gachsaran oil field, SW Iran

The Albian-Turonian carbonates of the Sarvak Formation are the host of the second prolific petroleum system of the Zagros folded belt, SW Iran. This research aims to investigate sedimentary facies and diagenetic processes of the formation in Gachsaran oilfield, which is the second Iranian supergiant oilfield in the southern Dezful Embayment. Combination of cores and petrographic investigations together with wireline log analysis of seven drilled wells led to identification of eleven microfacies deposited in different environments of a rimmed-shelf carbonate platform. The platform was affected by a tectonically active zone known as Kharg-Mish paleohigh due to re-activation of pre-existing basement faults during Turonian time. The findings also indicated that the studied carbonates were subjected to various destructive and constructive diagenetic processes such as micriticization, compaction, cementation, neomorphism and dissolution by passing through marine, meteoric and burial diagenetic environments while the uplifting process. Integrated Prediction Error Filter Analysis (INPEFA) plots of all drilled wells under study revealed that there are variations in sea level while during the Sarvak deposition.These variations led to generate different microfacies through the field from the east to the west. The data verified that the fractures and the rudist facies play the main role in the Sarvak reservoir of Gachsaran field. In addition the presence of paleohigh affected the thickness of sediments as well as microfacies changes and distribution throughout the field. These findings could contribute to a better understanding of the main factors controlling the petroleum system and optimum exploitation of the reservoir.