Sequence Stratigraphy and Sedimentation of the Araej Formation (Middle Jurassic), UAE: Outcrop and Subsurface Compared

Abstract

Abstract A comparison of the Araej section cropping out in Wadi Naqab (southeast of Ras Al Khaimah in the UAE) with the subsurface of Abu Dhabi and nearby areas shows that the Araej Formation of onshore and offshore Abu Dhabi is very similar to that of Qatar. The surface section was compared to well data using core petrography, biostratigraphy, characterization of the cycles and depositional environments and sequence stratigraphic analysis. The Araej Formation corresponds to the section between the top of the Izhara and the base of Tuwaiq Mountain Formation. The age of the Araej section of Wadi Naqab succession, similarly to the subsurface, ranges from Bathonian to Callovian. In Wadi Naqab, the cyclic section equivalent to the Araej Formation comprises five sequences. The recently defined Arabian Maximum Flooding Surfaces, J30 and J40 are evident in Wadi Naqab. J30 coincides with the MFS of the first Bathonian sequence, in the lower part of the Lower Araej, while J40 can either be located near the top of Uweinat or near the base of Upper Araej. The Uweinat is composed mainly of grainstones, micropeloidal in the lower and middle parts and oolitic and cross-bedded in several horizons throughout the section. Stromatoporoid and coral rudstones occur in the upper half. The Uweinat of Wadi Naqab seems similar to the offshore Uweinat reference section of well US-2, where reworked stromatoporoides were also recorded in the upper Uweinat. As a result of regional correlations, the Araej section of a well of NE Abu Dhabi is proposed as the onshore reference section of the Araej Formation of Abu Dhabi. The Sequence Stratigraphic interpretation with the identification of the Maximum Flooding Surfaces provides better chronostratigraphic control enhancing prediction accuracy of the geometric relationship of source, reservoir and seals. A better characterization of the Araej Reservoirs will support the regional correlation, exploration and production of the Middle Jurassic of the Middle East.