3-D Visualization of West Africa Waterbottom Leveed Channels and Debris Flows: Analogues for Offshore Reservoirs

Sutton, Jason P., Robert M. Mitchum, ChevronTexaco, Bellaire, TX

3D images of Pleistocene sea-bottom leveed channels and associated debris flows of deepwater offshore West Africa make excellent analogues for interpreting older subsurface features. GeoProbe visualization of these high-resolution images shows details of a large leveed channel system, at least 30km’s across, as it emerges from the mouth of a 1.6km wide canyon. The canyon head cuts into the present-day shelf margin and traverses down the slope. A large apron of leveed channels and associated debris flows builds out from the canyon mouth directly onto the basin plain.

Several avulsing channels and associated levees emerging from the canyon are shown in unusual detail. Slumping of channel walls and levees produces debris flows in all stages of development. In addition, broad shallow sheets of debris flow on the adjacent slope are developed from large slump scars. These features can be studied in great detail in all stages of development.

Slightly older leveed-channel systems occur just below the water-bottom surface (upto 600msecs below water-bottom), in a complex complementary fill pattern. One of these channel-levee systems is filled with a meandering set of channels occurring in a straight, tightly constrained meander belt. Another has a set of basal parallel high-amplitude reflec­tors probably representing an attached frontal splay.

3D visualization techniques using GeoProbe were used to make remarkable images of all these features, including channels and levees, meander belts, and debris flows. The features are shown both as geomorphic surfaces and reflection pattern configuration architecture. Several examples illustrate these uses.