The Lower Miocene Rudeis Formation in the Zeit Bay Field (Gulf of Suez, Egypt) has been studied by analysis of cores from six boreholes. The objective was to detail the sedimentary cycles in the formation and their implications
for the reservoir characteristics, as well as to obtain a more detailed insight into the precise age by
establishing a foraminifer zonation. The formation, which was found to be some 60–191m thick, is composed
almost exclusively of various types of carbonates. These contain foraminifers that prove a Burdigalian age, and
that also provide insight into the depositional environments, which turned out to form three belts. These belts
represent an intertidal lagoon, barrier shoals, and a reef complex, respectively, indicating a down-dip depositional
profile of a shallow marine rimmed carbonate shelf. Analysis of the cyclicity pattern of the Rudeis
Formation, supported by facies analysis and CycloLog curves, makes it possible to distinguish three superimposed
3rd-order depositional cycles, which are subdivided into several higher-order cycles that are strongly
controlled by eustatic sea-level fluctuations. A set of lithofacies isopach maps has been constructed for these
cycles with the objective to facilitate interpretation of the spatial distribution of the reservoir quality for hydrocarbons.
The maps show that the reservoir quality of the Rudeis Formation is heterogeneous because of the
highly variable characteristics of the various lithofacies types.