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Petroleum prospects in deep water (300 to 3,000 m) in the U.S. Atlantic continental slope and rise occur in three major trends: shelf-edge/slope carbonate complex, Blake Plateau-Carolina Trough, and the upper continental rise. Data supporting the potential of these trends come from COST wells, DSDP core holes, USGS multichannel seismic profiles, single-channel seismic surveys, and aeromagnetic and gravity surveys.
The carbonate complex parallels the present shelf-slope boundary in 300 to 2,000 m of water along much of the U.S. Atlantic margin and consists of a series of discontinuous barrier-reef structures ranging in thickness from 1,000 to perhaps 6,000 m. Associated with this complex, on the basis of seismic interpretations and COST B-3 well data, are thick, west-dipping, porous sandstone wedges, east-dipping forereeftalus wedges, and elongate anticlinal closures in strata overlying the reefs. The Blake Plateau-Carolina Trough trend contains a series of large salt domes and swells together with low-relief anticlines, fault traps, and patch reefs. Prospects in the upper rise include east-dipping fan deposits, buried slump deposits, channeled unconformities, fault traps, buried sea-mounts, and oceanic basement highs.
Jurassic and Lower Cretaceous strata contain the most promising potential reservoirs in the carbonate complex and Blake Plateau trends; Cretaceous and Tertiary turbidites, contourites, and chalks may also be prospective in the upper rise. Low and discontinuous porosities and permeabilities may limit some reservoirs, although faults and fracture zones could provide local permeability enhancement. Hydrocarbon maturation depths in the rise are estimated to be greater than 2,000 m below sea floor and as much as 4,000 m in the other trends. Potential source rocks are Lower Cretaceous black shales as well as Jurassic shales and carbonates that may have been deposited in an oxygen minimum zone on a paleoslope.
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