You are invited to a technical presentation which will be delivered by Dr. Nigel Cross - Subsurface Team Leader, BG Trinidad & Tobago.



Date:     Wednesday 23rd February, 2011.
Venue:   The Normandie Hotel - Gallery 1&2
Time:     11:30am - 1pm
 

The 3-D Seismic Geomorphology of Deep-Water Slope Channel Systems – A Case Study from the Deep Water Nile Delta

 Dr Nigel E Cross. 

Within the Nile Delta gas province, reservoirs are dominated by Pliocene slope channel systems, which are spectacularly imaged on high quality 3-D seismic data. This presentation discusses the broad character of these reservoirs and then focuses on one of the larger and better, developed examples – the Sequoia channel system. The seismic geomorphology of this particular system will be described, focusing on the geometry and distribution of its component sand-bodies, and the impact they have on reservoir heterogeneity. The Sequoia reservoir serves as a potential analogue for similar, but less well imaged, deep-water slope systems.

 The reservoir consists of a succession of sandstones and mudstones organized into a composite upward-fining profile. Sand-bodies include laterally amalgamated channels, sinuous channels and channels with frontal splays, and are interpreted to be the products of deep-water gravity-flow processes. Above a major basal incision surface, the reservoir is highly sand-prone and made up of laterally amalgamated channels. The medial section of the reservoir is more aggradational and exhibits laterally isolated and sinuous channels. Within the upper part of the reservoir, channels are smaller, straighter and built of individual channels with associated frontal splay elements. The main channel system is buried by a pro-grading slope succession that includes lobate sand sheet elements. The stacking of facies within the Sequoia channel system implies a punctuated waning of sediment supply prior to eventual abandonment. 

The Sequoia channel is interpreted to be the late low stand to transgressive infilling of a 3rd-order early low stand slope incision. The channel fill is overlain by a mudstone unit, which delineates a major correlatable ‘hot’ gamma-ray event, and on seismic data is a prominent down-lap surface and therefore a candidate maximum flooding surface).  

The Sequoia channel system shows evidence for syn-sedimentary faulting including a large-scale down-dip widening of the channel, and small-scale channel diversions and intra-slope ponding of flows. 

Understanding reservoir architecture in terms of sand-body geometries and connectivity is vital within Sequoia because the gas column occupies the most complex and heterogeneous upper part of the reservoir. Correspondingly, the basal sand-rich part of the reservoir will significantly influence aquifer behavior during production.

Bio of Dr. Nigel Cross  

Dr Nigel Cross is the Subsurface Team Leader for BG Trinidad and Tobago’s NCMA and Central Block interests. Prior to his arrival in Trinidad (2008), he was based in BG’s Cairo office where he worked on the spectacular slope channel reservoirs of the West Delta Deep Marine area. Before joining BG in 2004 he worked for Petro-Canada, Hess and Badley Ashton – all in the UK. He has a Geology BSc. (1992) and PhD (1996) from Royal Holloway, University of London. His technical interests range from the detailed characterization and modeling of carbonate and clastic reservoirs to regional rift basin geology.