Reservoir Characterization of Cretaceous Carbonate Reservoirs in Ultra-Deep Waters of the East Mediterranean Sea, Egypt

Abstract

The East Mediterranean basin is considered an essential area for hydrocarbon production, which has led to an increased drive for exploration in this region. The main reservoir zone in the Eastern Mediterranean Sea is the carbonate reservoir of Cretaceous age. The characterization of this reservoir provides a supporting role for developing and exploring gas in such important region. In this study, Cretaceous carbonate reservoirs have been subjected to reservoir characterization approaches. This process typically integrates various data sources like well logs, seismic data, core samples, and production data to construct a geological model, which then helps in the creation of a reservoir simulation model. The geometry of these Cretaceous reservoirs is a shallow-water carbonate platform situated directly beneath the Messinian Evaporite, with structural settings influenced by growth faulting towards the northeast. The depositional model reflects a shallow-water, "ramp-like" carbonate system developed on an isolated structure, comprising inner, marginal, and outer settings. The main lithofacies include limestone, with some breccia and marl facies present. Porosity and pore connectivity vary from poor to fair in the uppermost part, improving from good to excellent in the downward reservoir section. The Messinian evaporites contain claystone-rich layers that demonstrate the potential to be source rocks, as they have relatively high levels of total organic carbon (TOC) reaching up to 1.5%. On the other hand, the Cretaceous Reservoir interval lacks significant source rock potential, as the average TOC is less than 0.2%. The source rock within the Messinian evaporites generates gas of biogenic origin.