Hormuz salt distribution in the United Arab Emirates: Implications for the location of hydrocarbon fields

Hydrocarbon fields in the United Arab Emirates (UAE) are related with Neoproterozoic basement highs and/or Ediacaran–Early Cambrian Hormuz salt domes. However, neither the basement nor Hormuz salt are penetrated or imaged by available well and seismic data due to thick Phanerozoic sediments. In this study, we have used the residual gravity anomaly of the sedimentary layer throughout the UAE by subtracting the gravity response of the basement structure from the isostatic residual gravity anomaly. The structure and distribution of the low-density Hormuz salt were then delineated for the first time by applying a 3D constrained layer inversion method on the residual gravity anomaly of the sedimentary layer. Well data were used to constrain this inversion from which the density of the reference model and the isosurface of the Hormuz salt were defined, whilst seismic profiles were used to qualitatively check the location, shape and depth of the domal structures. The inversion model shows that the Hormuz salt is more widespread in offshore than in onshore UAE and generally occurs within NE-SW to N–S trending basins. The inverted Hormuz salt model has a thickness that ranges from 1000 to 4000 m, with an average thickness of 2100 m. Moreover, the model suggests that the Hormuz, Ara (central Oman) and East Rub’ Al Khali (Saudi Arabia) salt basins are most likely connected, except in regions of structural basement highs. In addition, the model reveals a low density (≤2290 kg/m3) shallow layer (0–6000 m below the sea level) in the foreland basin, which corresponds to the Aruma and Pabdeh sequences that infill the foreland basin. Many of the offshore hydrocarbon fields in the UAE such as Zakum, Umm Shaif and Sarb are associated with Hormuz salt domes. Also, several hydrocarbon fields adjoin basement highs, which are possibly related to the flexural bulge caused by the emplacement of the Semail ophiolite on the Arabian continental margin. The basement highs are probably bordered by faults, which could have initiated halokinesis of the Hormuz salt. Thus, the 3D inverted model provides a detailed distribution of Hormuz salt bodies, which allows an improved understanding of Palaeozoic hydrocarbon plays in the UAE.