Seismic Sequence stratigraphy of the Cenomanian-Turonian Succession of the Sarvak Reservoir Formation in the Abadan Plain

The sedimentary succession of Cenomanine-Turonian, which is introduced by Sarvak Formation, is the most important hydrocarbon (reservoir) formation of Abadan plain. Reservoir facies of this formation show variable temporal and spatial distribution in this time period due to tectonic and sedimentary conditions. In this study, using subsurface seismic data and well data (petrophysical logs and core thin sections), and also comparison with surface outcrops data of Izeh zone, facies, sedimentary environments and diagenetic changes of Sarvak Formation have been studied and analyzed in the framework of sequence stratigraphy. Investigation lateral and vertical variations of facies belts and sequences indicated sedimentation of Sarvak Formation on a rimmed carbonate shelf and intra-platform basins. By examining the changes and geometries of sedimentary-seismic facies along with well, paleontological and petrophysical data and comparison with outcrops, four third-order sedimentary sequences have been separated in the Sarvak Formation (Cenomanian – Turonian interval) with an average age of about 4 million year. These sequences include K120, K130, and K135 in the early Cenomanian, mid Cenomanian, and late Cenomanian respectively, and the K140 sequence is in the early to mid-Turonian. This study showed that distribution and migration of system tracts are consistent with the reservoir zones of Sarvak Formation. The best reservoir facies are in Highstad Systems Tract (HST) which are grain-supported, high porosity and permeability and are subjected to diagenetic processes such as dissolution and karstification. The K135 Sequence forms the best hydrocarbon-containing reservoir facies of shoal, rudist, and channel type in the area.