Geomorphology and Internal Architecture of a Pleistocene Niger Delta Channel-Levee Complex – Implications for Reservoir Modeling

Abstract The geomorphology and internal architecture of a shallowly buried Pleistocene erosive-constructive channel-levee complex on the continental slope of the Niger Delta, Nigeria, named Channel-1A (Ch-1A), was studied using a combination of 3D seismic geomorphology and stratigraphy methods. Seismic facies description, seismic stratigraphy, channel morphology characterization, architectural elements (AEs) delineation, and reservoir modeling were carried out to establish Ch-1A geomorphology, internal architecture, and sediment fills. The study objectives also include the understanding of temporal and spatial evolution of Ch-1A’s internal architecture and the factors responsible for their variations, and demonstration of the impacts of internal architecture complexities on reservoir modeling and development strategies. Observations from this work suggest a strong interplay between channel evolution and a range of controlling factors such as relative sea-level change, the rate and type of sediment supply, and sea-floor morphology. Evolution of Ch-1A was categorized into five stages (from oldest to youngest): (1) channel initiation dominated by sediment bypass and slumping, (2) basal meander loops and lateral migration that resulted in lateral accretion packages (LAPs), (3) evolution into channels that are both meandering and aggrading, (4) late-stage channels that are dominantly aggrading and capped by turbidite mud fills and (5) hemipelagic draping. This study demonstrated the critical roles that a proper understanding of internal architectures and detailed AE delineation play in reservoir modeling. This is critical when building 3D geocellular models with grids, zonation, and cells sizing capable of capturing vertical and lateral variation in geomorphology and heterogeneities before and after upscaling.