3D Seismic Interpretation of Ruby Slide Complex in West Nile Delta (Eastern Mediterranean)

A slide complex in the Western province of the Nile deep sea fan (NDSF), off Egypt has been imaged using 3D seismic data. The landslide deposits are characterized using techniques of seismic stratigraphy and seismic geomorphology, and 3D seismic visualization which allow detailed mapping of the slide geometry, internal flow structures, the erosional headwall, basal sliding surface and investigation of their inter-relationships.

The 3D seismic data reveal that the slide complex consists of two major separate, but related slides units, one nestled within another, and with their own distinct headscarps and basal shear surfaces. We propose that the staircase geometry can best be explained by a progressive model. The landslide deposits consist of large closely spaced pyramidal blocks (250 to 500 m wide and up to 250 m thick) bound by small normal faults which have rotated and deformed within a chaotic debris-flow matrix. The larger erosional slide scar is approximately 35km wide and at least 60km in the downdip transport direction. The combined excavation of the pre-existing slope sediments amounts to approximately 1000m which makes it one of the deepest incising of its type in the world.

We speculate that potential triggers for slope failure could be (1) pore pressure generation probably due to local sediment loading, (2) presence of gas in sediments, (3) melting of gas hydrates and (4) earthquakes. It is expected that rapid unloading of significant portion of the slope due to such a large landslide, would hydraulically fracture seals to any underlying petroleum accumulations. We suggest that rapid release of the overburden confinement would lead to transient high overpressure particularly in the gas reservoirs thus resulting to hydraulic leakage. This slide is therefore a spectacular example of the potential implication submarine landslide can have for petroleum systems.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California