Evolution and Modeling of the Carbonate-Clastic Permian system in the Jeffara Basin, Central Tunisia

Permian deposits are found in outcrops and in the subsurface of Central Tunisia. Their sedimentary and stratigraphic characteristics and origin are not fully understood and represents the main focus of this work. Base level changes, location of the palaeo-coastline and stratigraphic architecture and sandstone connectivity of formations are insufficiently known. Answering these questions will impact future hydrocarbon exploration and improve the geological understanding of Tunisia. Seismic lines and well data of the Jeffara Basin have been re-interpreted and seismic data converted to depth domain. The results indicate a shallow marine rimmed shelf depositional environment, with dimensions of 100 square kilometers and a general east-west orientation. Seventy kilometers to the north of the reconstructed paleoshore line twelve stacked reef complexes up to 3000 meters thick were identified. Literature study of the area indicates a tropical climate. Structurally, it was observed that the Permian is not affected by major normal faults and appears at large scale gently folded. Wells and outcrop investigations provide lithological information, which is composed of limestone and dolomite, with intervals of sand and shale. The thickness gradually increases northwards, reaching 4000 meter maximum. Using DionisosFlow, 3D stratigraphic models are constructed. They provide a number of equiprobable scenarios of facies distribution through the basin matching the available data. This modelling approach highlighted the impact of base level changes on reef geometry and in the lateral connectivity of clastic deposits. It also indicates depocenters shifting, shoreline evolution and feeder systems position and importance over time.