Abu Dhabi Fold-Thrust Belt Dilemma of Jebel Jais Outcrops: Impact on Hydrocarbon Trapping Mechanism in Eastern Abu Dhabi

Abstract

For the last decades, only a few scattered wells have explored the thrust fold belt in Abu Dhabi, with inconclusive results about the hydrocarbon potentiality. Drilling was avoided in these areas in the past due to the geological complexity and unavailable technologies that would reveal the subsurface geometries. Previous studies attempted to resolve the petroleum system elements in Eastern Abu Dhabi; however, they are still challenging, and require thorough investigation. This paper is focusing on the integration of Jebel Jais outcrops in Ras Al Khaima with subsurface datasets (Geophysical and well data), which will help in understanding the subsurface structural trap geometries, reservoir and charge evolution and timing. The outcrops functioned as remarkable analogues for structural features that indicate complex tectonics of the region such as folding and faulting. They will also serve in guiding the mechanical and kinematic modeling of subsurface, where seismic image is undistinguishable. ADNOC has recently completed a Mega 3D seismic survey in Eastern Abu Dhabi with higher acquisition parameters compared to the legacy 2D and 3D seismic surveys. The early fast track Seismic processing results revealed additional structural styles, which will be refined with advanced seismic imaging techniques, and calibrated with potential data such as gravity and magnetics in later stages. The thrust nappes deformation and the fault-bend folds were observed in the outcrops. Most of thrusts are associated with strike-slip component and the detachment surface located at the base of Khuff units. Folding-stacked structures have different orientations with narrow duplexes that led to the growth of anticlinal stacked structures, which were the consequence of differential uplift of the rock units above the duplex, and were subjected to stretching. This process invoked strike-slip faulting along the lateral culmination wall and was facilitated by the regional, syn-thrusting arc–parallel transpression. Horizontal movement along the fault plane is a result of tear faulting accommodating a varied rate of advancement of Khuff units. The time of the fault formation is well-constrained post-Jurassic; however, the syn-thrusting origin showing its anticipation through Triassic onwards forming thrust-fold belt. This paper will provide insights from Jebel Jais Outcrops that will help in understanding the substantial undiscovered hydrocarbon resources and prepare for future exploration activities.