Resolution of a Multi-Set, Strike-Slip Dominated Fault System, Identified from 3D Seismic, in Early Cretaceous Carbonate Reservoir Sequences of a Giant Offshore Field in Abu Dhabi

Abstract

Abstract Recent mapping of fault patterns from picked surface attribute analysis (‘difference’ maps, spectral decomposition, isochron maps) and time slices over a giant offshore field in Abu Dhabi has recognized a complex multi-set pattern of faults at reservoir level. As well as providing additional seismic scale faults, linear features (proposed subseismic faults and fracture systems) have been identified. These patterns are best described in terms of strike-slip geometries; however, many display components of both dip-slip and strike-slip over their movement history. In different parts of the field dominant fault directions displaying dextral transtension, dextral transpression, trapdoor hinge faulting and oblique-slip keystone graben generation are observed. Fault throw statistics and segment growth history in the most important mapped zones typify components of strike-slip along with local shear and segment termination at cross-fault zones. The prevalent fault trends are roughly orthogonal NE-SW and NW-SE systems that dissect the field. Superimposed on this geometry is an array of distinctly en-echelon WNW-ESE and WSW-ENE structures that link to steep zones at deeper levels. Within sub-regions of the field other trends are also present, including NNE-NNW to N-S, NNW-SSE and E-W. These sets do not form a radial pattern; they are distributed spatially within field domains and involve complex systems and layer-related rheologically controlled deformation. Comparison of the mapped lineament pattern with core-derived fracture orientation data shows that all sets identified in the field from seismic are present within the overall fracture strike system within the wells. Field-wide, domains where transtension and transpression dominate, as well as more dip-slip dominated areas can be mapped out. Core scale fractures tend to display a component of strike-slip within the bulk strain field-wide, as evidenced by steep or sub-vertical fracture intersections. Newly identified lineament zones allow better understanding of high intensity fractured wells previously mapped distal to known faults