New insight into salt-related structure in the Onshore Zagros foreland basin, a prospect into the deep gas reservoirs

The Southern area of the Zagros fold-and-thrust belt (ZFTB) well-known as a great hydrocarbon province developed over the Cambrian Hormuz salt basin. However, the existence of Hormuz salt in the west and southwest of the ZFTB was always under debates. Using a multidisciplinary approach based on high quality 3D seismic data, seismic attributes evaluation, well data analyses, 3D mechanical restoration and depth and thickness maps, this study describes the geometry and kinematic of salt bodies in the Mesopotamian Zagros foreland basin (i.e. Abadan Plain), and their possible salt-related traps for the first time. Deep seismic interpretation reveals that three deep-seated structural trends inherited from the basement including N-S (Pan-African), NW–SE (Zagros), and NE-SW (Neo-Thetyan) trends have affected the basin-infill of the study area. Seismic sections across a N-S trending Azadegan-Burgan Paleo High allow to interpret two buried salt structures that possibly started to develop at the Lower Paleozoic soon after the salt was deposited. It seems that after the huge inflation of both salt structures during Paleozoic times, their growth significantly diminished by the end of the Permian. Therefore, the halokinesis is mainly confined to the Permian strata, and the younger strata are fairly affected by minor salt withdrawal. The 3D structural restorations illustrating the post-salt evolution in the area allows to recognize two main tectonic events during the Upper Jurassic and the Late Cretaceous times. The Late Cretaceous contractional deformation reactivated the two deep-seated basin-bounded NE-SW faults and rejuvenated the inherited salt structures. Sequential restoration reveals that the N-S elongated anticline has segmented into two northern and southern domal-shaped structures with a mini-basin in between during the Ilam-Sarvak deposition (Late Cretaceous). During the Late Cretaceous, the structural amplification of the inherited salt structures is characterized by a number of crestal extensional faults and high channelization in the carbonate Sarvak-Ilam formations that significantly affected their reservoir quality. The southern salt dome structure made considerable relief at the deeper horizon which could be considered as potential structural/ pinch-out traps in the Permian to Early Jurassic formations. Seismic indicators (i.e. bright and flat spots) detected gas potential, gas-filled limestone bodies, in the Early Jurassic Neyriz Fm. sourced from the Permo-Triassic gas reservoir leaking up along the crestal extensional faults.