Seismic stratigraphy and sedimentary facies analysis of the pre- and syn- Messinain salinity crisis sequences, onshore Nile Delta, Egypt: Implications for reservoir quality prediction

Abstract

Abstract This study provides the first high-resolution outlines of the Messinian sequence in the Nile Delta based on an integrated sedimentological, petrophysical and seismic stratigraphic approach. The distribution, pattern and architecture of the Messinian facies deposited before, during and after the Messinian salinity crisis (MSC) have been investigated. In seismic, the pre-MSC Qawasim Formation constitutes parallel oblique seismic facies interpreted as deltaic system prograding northward from prodelta, distal sand bars into subaqueous distributary channels and mouthbars and subaerial delta-plain distributary channels. The MSC Abu Madi Formation consists of three seismic-stratigraphic units infilling the Eonile canyon. A seismically chaotic lower unit paving the canyon-floor is overlain by the continuous, high-amplitude reflectors of the middle unit which is capped by semi-chaotic, low-amplitude facies of the upper unit. The lower unit corresponds to the subaerial gravity-flow deposits synchronously accumulated during the Eonile incision; whereas the middle unit comprises the aggradational-progradational fluvial facies, and the upper unit constitutes the retrogradational estuarine facies. The superimposed diagenetic alterations on these various depositional facies produced complex reservoir heterogeneity. Fluid flow conduits are restricted to the coarse-grained delta distributary channels and fluvial facies with limited marine influence and minimal depositional clay content and traces of diagenetic kaolinite and chlorite. On the other hand, flow baffles and barriers are common in the fine-grained marine-influenced facies with pervasive depositional clays, diagenetic calcite and glauconite.