Structural evolution of the Jebel Hafeet Anticline (Al Ain, UAE): A multi-scale approach to model fracture patterns and kinematic fold evolution

Conceptual, physical and numerical models have attempted to predict the fracture patterns from various fold shapes and kinematics, but so far these models remain poorly predictive in terms of spatial and temporal distribution of fractures. These models are crucial for reservoir characterization studies. Therefore, more detailed field-based data are required to better constrain 3D models of fold-fracture relationships.

For this purpose, we present new multi-scale fracture data collected at the northern half of Jebel Hafeet anticline (UAE) by combining different remote sensing methods with detailed field surveys. The Jebel Hafeet is an asymmetric east verging, double plunging anticline, formed above a dcollement horizon at depth and a basement thrust. The anticlinal structure, which has a length of 25 km and 5 km width, is famous for its excellent and continuous exposures from both limbs and fold hinge area, making it a suitable area to study fracture patterns. The development of fractures in the sedimentary layers of the anticline is documented and interpreted to constrain the kinematic evolution of the fold structure. The fracture patterns across the anticline are more complex than those predicted from conceptual models with respect to kinematics, timing and mechanical stratigraphy, and appear to be influenced by pre-folding fracture sets, mechanical boundaries and fold growth. The rich dataset produced by these combined techniques provide statistically robust estimates of the spatial variation of fracture orientation and density across the fold surface for reservoir characterization.

This study highlights also that although remote sensing data are so beneficial for structural geology interpretation, providing detailed information in 3D and a multi-scale approach, their value is significantly reduced without detailed structural field work. Such a field-based and multi-method analysis opens new perspectives in the understanding of fold related brittle structures development that deviate from the theoretically proposed models for fold-fracture relationships.