Seismic and Chronostratigraphy of the Late Jurassic Carbonate-Evaporite Arab Formation, Abu Dhabi: Insights into Stratigraphic Traps Potential

Abstract Our study demonstrates the application of seismic sequence stratigraphy interpretation in carbonate-anhydrite dominated interval from sabkha to inner ramp depositional setting. The primary objective is to reconstruct regional stratigraphic architecture including the lateral and vertical distribution of the Arab, Hith, and Asab Formation across the Abu Dhabi area. The regional seismic transects were utilized to perform chronostratigraphy correlation of several wells in the Arab and Hith Formation as well as the equivalent Asab Formation across UAE. Finally, integration with the wellbore data describes reservoir quality and hydrocarbon distribution that have potential for stratigraphic and/or diagenetic traps. A comprehensive and regional approach utilizing various subsurface data including 2D seismic reflection profiles, and wellbore data are presented. Integrated seismic facies analysis, seismic instantaneous attribute, and seismic density inversion, as well as sequence stratigraphy combined with detail petrographic analysis have been applied to reconstruct regional stratigraphic framework and reservoir characterization of the carbonate-evaporites system of the Arab Formation. Four second-order sequences from mud-dominated basinal limestones, grain-supported oolitic and skeletal shoals, and lagoonal to supratidal anhydrite-rich deposits were interpreted. In addition, four sequence boundaries (SB) and three maximum flooding surfaces (MFS) correlated with MFS J80, J90, and J100 of regional framework. The first sequence commenced from the west-northwest as aggradation-progradation cycles, followed by east-southeast progradation of the second sequence. Several toplap reflectors observed in sequence 4 located near the Asab area which coincide with the pinch-out of the Hith Formation. An angular unconformity was observed in the fourth sequence in the easternmost of Abu Dhabi that could be associated with the Upper Jurassic uplift and erosion in the east Arabian Plate. Denser seismic profiles in an offshore oilfield in the Northwest of Abu Dhabi indicate a south plunging anticline at the top of Arab D interval without structural closure in the north. The absence of fault in the north from the seismic and well suggests a stratigraphic or diagenetic trap development. A lower density zone was detected in the north based on density inversion analysis that could be associated with cementation, dolomitization, or bitumen as the permeability barrier. This study provides new insights of the comprehensive regional and detail chronostratigraphy of the Arab Formation and a case study for the stratigraphic trap identification.