The geometry of the Western Boundary Fault (WBF) of Amer oil field and its influence on hydrocarbon trapping, western central Gulf of Suez, Egypt

Abstract

Amer ridge holds one of the most prolific oil fields in the western central Gulf of Suez rift basin and was discovered in 1965. The brownfield produces oil from the Miocene-Eocene carbonates and Late Cretaceous sandstone reservoirs with oil water contact 1150 m. The present work provides a structural model expressing the role of inherited structures and the tectonic evolution of the western fault bounding the field. This model resulted from the multi-scale integration of subsurface data from 90 wells, various borehole images, and 3-D seismic volumes attributes. The interpretation demonstrated the vertical profile of the western boundary fault of Amer field (WBF) to be a ramp-flat-ramp geometry pattern cutting through lithological units of different rheology. The developed fault surface of the WBF divided the penetrated sedimentary succession into two distinct strain intervals. The inherited structural fabrics of the lower interval of pre-rift units are documented with 1) an anomalous southwest-stratal dip, and 2) severe deformation of the WBF footwall with extensional faults of gulf parallel and gulf-orthogonal trends. Simultaneously, the roll-over anticline-syncline structure that developed within the upper, less-strained Miocene interval, coincided with the flat of the WBF geometry.By applying this model, it was possible to i) distinguish the three-footwall structurally controlled plays of Amer area into lower ramp-1, flat, and upper ramp-2 and ii) enlarge the size of the brownfield. Recent development activity in Amer area verified the new structural model and expanded the drilling activity to target the Paleozoic clastic reservoir of Nubia C as a new exploration objective. The Amer structural model can serve as a useful analogue for oil field development and production enhancement in other complex rift basin settings.