Deepwater Reservoir Elements: Channels and their Sedimentary Fill
Deepwater channels have received considerable attention in the petroleum industry during the past decade because of (1) the important discoveries that have been made in several deepwater basins in which reservoir performance was critical to development decisions and strategies (e.g., Campos Basin, Brazil; offshore Angola; the Nile; the Mahakam Delta; the northern Gulf of Mexico; West of Shetland Islands; and offshore mid-Norway); (2) the ability of 3D seismic to increasingly image the complex internal geometries of channel systems (especially those that are sinuous); and (3) the need to avoid shallow flow problems while drilling channel-fill sediments.
Many slope systems in passive margins are very muddy. The importance of channels as sand conduits for bypass to the basin floor probably was not fully appreciated until about 15 years ago, when large volumes of sand were recognized to occur downdip of muddy slope systems (e.g., Angola and the northern Gulf of Mexico). Many slope channels are marked by evidence of sediment bypass (coarse-grained lags, traction deposits, hetero-lithic deposits of fine-grained tails, and fine-grained levees, in some instances).
Channels and their fills have been studied for many years, from different perspectives and using multiple data sets, including data from the modern seafloor, from the shallow subsurface (shallow seismic for shallow-hazards drilling surveys), from deeper-exploration seismic, from reservoirs, and from outcrops. In this introductory section, we present a few general, qualitative concepts that are widely accepted concerning channels and their fills.
Because of the large number of published studies, and because most channel fills