Twisting Slip and Rotation of UAE Fault System

Abstract

Abstract Abu Dhabi fields are influenced by strike-slip and their damage zones as a main tectonic regime. A damage zone is the deformed volume of rocks around a fault surface that results from the initiation, propagation, interaction, and build-up of slip along fault segments. These damages zones impacted the distribution of the traps, migration pathways and increasing the drilling risks. Slippage and rotation along the fault segments in Abu Dhabi fields increases the damage zones widths around the fault segments. This paper presents a detailed description of the kinematics and dynamics of rotated damage zones in the strike-slip faults of Abu Dhabi fields. The factors that are controlling the damage zones around faults are mainly the rock type, relation between bedding and fault plane and stress tensors. This paper, however, focuses on the structures within the damage zones as they are influencing the trapping mechanism, the drilling hazards and how the rotation increases these. In addition, the structures formed at the fault tips are also considered, especially for the initiation and propagation of the fractures. Field examples and outcrop analogues of damage zones around strike-slip faults are presented. This study is integration between seismic, cores, logs, and outcrops. During the Late Cretaceous the kinematics of Abu Dhabi fault system changed to transtensional and accommodated a major component of left-lateral strike-slip motion with a SE-NW compressional component. The final phase occurred by the Miocene time, where the stress tensor is changed to NE-SW compression, which rotated the blocks. During this deformation, the blocks were dissected into a series of large-scale blocks bounded by NW-trending left-lateral strike-slip faults which merge into a NE–SW fault system that forms the main structures in Abu Dhabi. Field studies on the mountains exposures data from the fault bound subsurface blocks indicate 10°–15° of post-Early Miocene anticlockwise rotation with substantial latitudinal motion. The decrease/increase of stresses along the fault segments in the overlapping/linkage zones and at the fault tips under differential confining pressures affecting the rocks behavior and understanding of these will greatly avoid drilling dry holes and reduce the drilling risks.