Influence of Mass Transport Deposit on Stratigraphic Evolution, Channel Morphology, and Turbidite Reservoir Preservation and Architecture, Niger Delta, West Africa

Bakare, Olusola¹, Neil Hurley², Timothy McHargue³, Piret Plink-Bjorklund⁴ (1) Chevron International Exploration and Production, Lagos, Nigeria (2) Colorado School of Mines, Golden, CO (3) Chevron, San Ramon, CA (4) Colorado School of Mines, Golden,

Mass transport deposits (MTDs) represent a major component of the Miocene-Pleistocene deep-water system, offshore West Africa. The goal of this study is to determine the influence of MTDs on stratigraphic evolution, turbidite channel morphology, and reservoir facies preservation and architecture in a slope portion of the Niger delta.

The dataset used for this study is a conventional 3D seismic survey and a version of coherency volume. Although there are several wells in the area, there are no logs or cores in the study interval.

The deposition of a thick MTD along the depositional axis of an older channel had a significant effect on the depositional setting of the basin, which included a change in channel morphology, a change in depositional axes, and erosional truncation of turbidite reservoir facies within confined channels.

Depositional units in the study area have characteristic stacking patterns. MTDs occur at the base, overlain by distributary lobe complexes (DLCs), amalgamated channel complexes (ACCs), and they are capped by drape complexes (DCs). MTDs are very erosive, and they truncate part or all of the underlying reservoir facies. This study clearly shows that MTDs could act both as lateral and vertical seals for turbidite channel reservoirs.

Channel morphology changed from highly sinuous in the oldest sequence to relatively straight in the youngest sequence, caused by the deposition of laterally extensive, thick MTDs over older channel deposits. There is also a variation in the architectural pattern of turbidite reservoir deposits between older and younger channels separated by MTD deposition.