Abstract

This study uses previously unpublished reflection seismic data and wells to map part of the western margin of the Hormuz salt basin for the first time, and to link Hormuz facies distribution to the evolution of major structures in NE Saudi Arabia. Most of these major structures host giant or supergiant oil fields in Mesozoic reservoirs. This study is based on seismic interpretation of structural style because the Hormuz occurs at up to 10 km or more depth present day and is not penetrated by any wells. In the eastern part of the study area, seismically transparent zones with structural elements diagnostic of salt tectonics pass laterally into layered seismic facies with local clinoform geometries. The transparent facies are interpreted as mobile salt, the layered facies as immobile evaporite basin-margin strata. The layered facies display onlap and fault-bound relationships with older basement domains, and in map view the boundary between layered and transparent seismic facies at the Hormuz level forms embayments and promontories on the west margin of the salt basin. Areas of mobile salt underlie domal and periclinal structures, such as Karan, Hasbah, Dammam and Khursaniyah. These structures display steeply dipping reflections at depth that can be interpreted as salt pillow flanks, with base salt locally interpretable, and have plan-view aspect ratios of 2 or less. Beyond the limits of layered seismic facies, between the embayments and westwards towards the Arabian Shield, seismic and well data indicate that the major structures are not salt cored, including Berri, Manifa, Safaniya, Jauf, Juraybi'at and Haba.

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