Structural controls on submarine channel morphology, evolution, and architecture, offshore Western Niger delta

Partially-avulsed, leveed channels from the continental slope of the western Niger delta are studied using 3D seismic and well data. Four channel complexes (BC1– BC4), two ridges (A and B) and two mud volcanoes (MV1 and MV2) were identified. The morphology, internal architecture, and evolution of the channels changed in response to variations in slope gradient promoted by diapirism, faulting, and mud volcanism. The influence of local tectonics on the mapped channels is marked by channel blocking, migration, and diversion. The relative position of the channel to tectonic structures also interferes with channel morphology. Preserved cross-sectional profiles of BC3 varied between dish, U and V shapes with channel width increased in sections overlying the ridges A and B. Similar variations in morphology were also recorded for thalweg depth, channel fill thickness, levee width, and depth ratio. Abandonment fill is nearly even in BC3 except at the terminal end. MV2 was active at least twice during the evolution of BC3 and may have contributed some fine-grained sediments to BC3. Channel fill is mainly turbidity prone with alternating waxing and waning cycles; lithology consists of sandstone shale and silt in varying grain sizes and thicknesses. Tectonic activity such as diapirism, growth and listric faulting as well as mud volcanism influenced the channel evolution and internal architecture of BC3. In summary, the simple, straight BC3 as imaged by seafloor bathymetry is underlain by a complex, older geomorphology that favor the generation of structural traps and enhance reservoir properties in the western Niger Delta.