Sequence Cyclostratigraphy, and Sedimentary Facies Modelling of the Cretaceous Sandstone Reservoirs in Geisum Oil Field-Southern Gulf of Suez

By

Iman Hussein Helal¹, M.Nour El Din², M. Darwish Darwish³, S. Ahmed Ahmed³

(1) Geisum oil Co, Cairo, Egypt (2) Geisum oil Co, Cairo/Egypt, Egypt (3) EREX, Cairo, Egypt

 Geisum oilfield lies in the southern province of the Gulf of Suez. The Precampanian Cretaceous sandstones are the main oil-bearing reservoirs in the southern part of the field. This work highlights the stratigraphy and the depositional systems of this succession aiming better understanding of the reservoir geometry and its distribution.

The study results show that eleven sedimentary litho-facies units could be distinguished, included in seven 3rd order cycles of Precampanian age. The lowermost sedimentary sequence is of Barremian(?) age represented by fluvio-lacustrine facies overlying the Precambrian basement complex. It is followed upwards by a poorly fossiliferous shallow marine Turonian sandstone/shale sequence of tide-dominated setting channels, bars and prograding sand waves. The overlying sequence of Coniacian-Santonian age is built-up of sandstone/shale with carbonates of tidally influenced setting of wide spectrum mixed sand/mud flat to retrograding tidal bars. The succession is flooded at top by an open-marine sequence of shoreface and foreshore domains, being dominated by carbonates with subordinate shale and thin sandstone of Campanian age.

The correlation of the 3rd order cycles and facies belts show the direct impact of the fluctuating global sea-level and syn-depositional tectonics on the distribution of the reservoir units. The inter- and intra-cycle breaks are the critical elements that influence the subsequent depositional and diagenetic patterns, which control porosity development.

The distribution of the interpreted rock facies will lead to more reliable reservoir modelling and hence more chances for finding new potential hydrocarbon-bearing reservoirs.