Regional Sequence Stratigraphy and Sand Fairways as Controls on Hydrocarbon Occurrence in The Niger Delta

Joe Ejedawe, Benedikt Lehner, Steve Meyer, Femi Olugbemiro, Lisa Fullarton, Ohams Agwunobi, Julius Agbo, and Jorge Calvache
Shell International Exploration and Production, Rijswijk, Netherlands

A regional geological framework study of the Niger Delta was undertaken to provide better understanding of the hydrocarbon habitat. The study was based on a seismic 2D grid of 500x500m, and 500 well data.

Sequence analysis identified thirty two sequence boundaries (rSBO-rSB32) between 3.7 and 38.7 Ma, twenty one of which were mapped and integrated with sand percentage, isopach, channel system, and paleobathymetric maps to generate reservoir fairway and hydrocarbon sweet spot maps. The reservoir sweet spot in each sequence is confined to a relatively narrow belt within the sand percentage 2060%. The fairway maps trace the evolution of the delta from Eocene initiation and river domination with irregular shoreline to its present arcuate form and wave domination beginning in Oligocene time.

The channel systems, and sand percentage trends show direct linkage with turbidite facies of the deepwater acreage. The stacking of these turbidites since the early Miocene indicates about 150 - 300km transportation distance from the paleo-shelf edge. This distance appears to decrease with time as the delta system prograded basinwards apparently related to a contraction as the volume of underlying shale and its tectonic activity increased basinward.

The facies distribution indicates detachment of the shelf deltaics from the deepwater turbidites with the bypass zone represented by a facies belt of erosional channels, channel levee systems, and slope subbasins. This has implication for reservoir and pressure prediction, key elements in unlocking the potential of the deep play, the next frontier of the onshore Niger Delta.