A Regional Evaluation of the Pliocene Nile Delta Pore Pressure Regime
Eleanor Rowley1, John Dolson2, Alfio Malossi3
(1) Shell Egypt, Cairo, Egypt (2) BP Egypt, (3) IEOC,
The rapid accumulation of clastic sediments resulting from the progradation of the Nile Delta during Plio-Pleistocene times has resulted in the development of an overpressured province in the offshore Nile Delta. The primary overpressure mechanism in the Pliocene is undercompaction, since up to 5 km of sediment have been deposited in less than 5 Ma in the basin’s depocentres. Thick shale packages of the Kafr El Sheikh Formation trap overpressures as little as 500 m below the seabed.
A Joint Operator Study was initiated to enhance understanding of the regional Nile Delta pore pressure regime. The aims of the study included investigating the existence of overpressure mechanisms other than undercompaction, such as inflationary and hydrocarbon generation mechanisms; finding methods to more accurately identify overpressured sequences; and developing effective well plan strategies. Particular emphasis was also given to assessing whether the pressure signature was extractable from seismic interval velocities and developing best practices for picking velocities for pore pressure prediction work.
All 3 operators are embarking on deepwater exploration programs where the problems of encountering overpressures are enhanced by the often narrow envelope between mud and fracture gradients in the shallow unconsolidated sections of the well.
A byproduct of the Joint Operator Study was a multi-well and seismic trade between the 3 participating companies - Shell Egypt, BP Egypt and IEOC, helping to enhance our overall understanding of the geology of the Nile Delta.