Abu Dhabi Tectonic Evolution: Novel Model Impacting Hydrocarbon Potentiality and Trapping Mechanism
Authors: Noufal Abdelwahab , Alkatheeri Safeya , Obaid Khalid , Shehab Abdulla , Al Shehhi Hamda , Al Hadarem Saleh 
Published: October 2023

There is evidence that the Oman Mountains deformation is being continued by massive thrust fault systems in the Eastern Abu Dhabi basins. These are large-scale thrust faults with a strike-slip component that most likely include a fault damage zone encircling the fault core, a zone of strong rock shearing, and complicated zones of deformation involving numerous fault planes. The initial event was caused by the compressional movement of the Masirah, which faulted and folded again during the Semail tectonic events. Large faults are typically modeled on seismic as a single, large slip plane, but the outcrop analogs demonstrate the case is far more intricate, according to understanding of fault zone complexity and fault rock attributes from field observations.

To understand the strength characteristics and seismic behavior of faults in the subsurface, more in-depth information of the growth and structural style of thrust systems on outcrop analogues is essential considering the future exploration in eastern Abu Dhabi. Architecture, geometry, and tectonic uplift resulting from accumulated slip on the faults are all expressed at the surface for sub-surface thrust faults. The three-dimensional geometry of these fault planes and slip distributions, which provide suggestions to fault evolution and structural styles of the thrust systems in the subsurface, can be better understood by characterizing the structural patterns along-strike morphology of such styles.

The fold-thrust belt can be further divided into sub-belts, including the imbricate thrust sub-belt, which is characterized by imbricate stepped-thrust sheets, the thrust-fold sub-belt, which is composed of equally developed thrusts and related folds, and the detachmentfold sub-belt, which is composed of box, chevron, and closed overturned-isoclinal folds on the oblique surface. Imbricate thrust system, passive-roof duplex (triangle zone), fault-related folds, back-thrust system, pop-up structure, and other types of structures have all been identified or inferred.

A reasonable model for folding evolution in Abu Dhabi subsurface is presented answering the questions of the many interpretations for folding patterns, such as:

If these folds related to the compressional forces, then why they did not represent series of anticlines and synclines? Why have they dissected? Why showing different amplitudes from the deflection to the hinge zones? And finally, why the main geometry is open folding style and did not showing steep dipping limbs towards the direction of the compression more than the other limb?

This paper is presenting a trial to answer these questions lightening the tectonic evolution of Abu Dhabi basins reflecting the fields formation and evolution. Thrusting deformation developed preferentially along the main detachment layers, moving upward from the Upper Jurassic through the Cretaceous to Tertiary. The approach presented a new model for Abu Dhabi tectonic evolution, which will impact understanding of the hydrocarbon potentiality and trapping mechanism.