Seismic Challenges of Developing the Pre-Messinian - Akhen Field Offshore Nile Delta

By

 Robert Francis Marten¹, Mark V. Shann²

(1) BP Egypt, Maadi,Cairo, Egypt (2) BP Egypt, Maadi, Cairo, Egypt

 BP’s recent drilling results in the Akhen field, offshore Nile Delta, provide an excellent case study into the seismic challenges of drilling and developing the Pre-Pliocene in the Nile Delta. The challenges are significant: Pliocene overpressure cells, variable thickness and rugosity of Messinian anhydrite, deep and complex structural elements and seismic quality challenges.

Recent work suggests that the Serravallian aged reservoir sands present in the Temsah-Akhen area are likely turbidite channel complexes that were deposited over the structure as it started to form. Both seismic scale and sub-seismic scale channels are evident in the 18 wells drilled to date across the structure. Rock properties studies of the Serravallian aged sediments suggest that the sands are acoustically hard, with little acoustic difference seen between brine charged and gas charged sands. The sands are primarily Class 1, suggesting the sands remain hard at far offsets, regardless of pore fluid.

In 2001, BP drilled the first development well for the Akhen Field, West Akhen-2, which targeted three stacked channel sands. The well results suggest a higher degree of complexity and faulting than previously interpreted. Results of the re-processing, including the use of tomographically derived velocities, clearly show the structure at the West Akhen-2 well location has become much tighter, indicating event movement of 100-120 meters up-dip. In addition, the increased resolution from the near stack dataset reveled the presence of slump faulting, which had removed part of the primary objective section.