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Abstract The East Bahariya concession lies in the eastern Abu Gharadig Basin (northern part of the Western Desert of Egypt). The present study is based on the analysis of 3D seismic and borehole data. Detailed seismic interpretation of key tectonic events was integrated with data of 76 wells to develop a 3D structural model of the reservoir rocks of the area using the Schlumberger Petrel software. These 3D interpretation techniques besides flattening of seismic sections provide accurate details of the structural geometry and fault patterns in the area. They also reveal structural deformation represented by large buried NE-trending inversion anticlines that play an important role in the hydrocarbon potentialities of the area. This tectonic inversion took place in post-Coniacian time and continued slightly during the Tertiary, till the Oligocene. Three main episodes of deformation have been detected in the area of study: (1) A Jurassic-Early Cretaceous extensional episode, resulting in the formation of NE-trending extensional faults bounding asymmetric half-grabens, (2) Santonian-Oligocene positive inversion of these extensional faults and (3) Post-Early Miocene Extension. Structural traps have proven successful to date in the area of study, particularly fault-dependent, footwall three-way dip closures (fault-block traps) and hanging wall four-way dip closures (inversion anticlines). A set of tectonosequences related to the opening and the subsequent convergence of the Neotethys was mapped. The inclusion of 3D seismic isochore data facilitated mapping the thicknesses of the tectonosequences. Each identified tectonosequence has its own unique drive mechanism and geometry. Recognition of these elements allows illustration of the Neotethyan basin evolution of East Bahariya concession through time as well as understanding the tectonic and stratigraphic framework and effective prediction of the petroleum system. A fault seal study was performed for selected oil fields in East Bahariya concession. Together with petrophysical logs, the constructed 3D model of the fault displacement was used to compute the variation of fault seal potential (shale gouge ratio or fault-zone percent shale) on each fault surface and to predict cross-fault juxtaposition relationships in 3D space, based on the geometries of strata that are cut by faults. Compilation of many shale gouge ratio analyses with in situ pore pressure data has allowed a better definition of the relationship between calculated shale gouge ratio and maximum trapped hydrocarbon column height, i.e. the ‘fault seal-failure envelope’. This example demonstrates that a 3D analysis leads to significant improvements in the prediction of fault seal, the analysis of the interaction of the sealing properties of multiple faults, and the interpretation of fault seal within the context of sedimentary basin geometry. Keywords: East Bahariya concession, Western Desert, 3D structural model, inversion anticlines, post-Coniacian, tectonosequences, shale gouge ratio, fault seal. |