Tectono-Sedimentary Provinces of the Oligocene-Quaternary in the Offshore Nile Delta; Relevance to Hydrocarbon Trapping and Reservoirs Distribution

By

 Lorenzo Meciani¹, Sergio Laura¹, Mesbah Khalil¹

(1) IEOC (ENI-Agip), Cairo, Egypt

 The offshore Nile Delta is a prolific and prospective hydrocarbon province due to the potentiality of its Oligocene-Quaternary succession. The richness of this system is related to the continuous source of clastic from south and to the complex tectonic-sedimentary history that provides different reservoirs and trapping mechanisms.

The Messinian evaporites form a major horizontal tectonic separation between two different tectonic environments, while the sedimentary pattern remains relatively constant in the entire Oligocene-Quaternary, being formed by an overall prograding Deltaic sequence.

A number of tectono-sedimentary provinces, characterized by specific trap mechanism and reservoir facies, are identified.

Compressive/transpressive deformations prevail during Pre-Messinian; few tectonic provinces can be defined, and predominant syn-depositional deformations affect the sea-bed morphology, controlling reservoir facies distribution.

Proven Messinian reservoirs are localized in the Abu Maadi paleo-valley; potential for reservoir facies is expected down-current.

Marked differences are recognized within the provinces of the Plio-Pleistocene. Localized syn- and post-depositional deformations affect the sub-marine topography and, along with sea level fluctuations and distance from clastic supply, control facies distribution and trapping mechanisms.

The extent to which Plio-Pleistocene can be considered a sedimentary analogue to pre-Messinian sequences is under debate, as analogies and differences are present.

Continuous source of clastics during Oligo-Quaternary is mainly related to the contemporaneous rising and erosion of the western shoulder of the Red Sea-Suez rift. The eroded clastics are transported westward to the Nile valley then through the main channel to the Nile Delta where entry points were available from Oligocene to present.