Geophysical Assessment of Offshore Seabed Stability for Oil Platform Installation in the Deep-water Niger Delta

Deepwater oil platform installation in the Niger Delta requires rigorous geotechnical and geophysical assessment of seabed stability, as the region's sedimentary setting introduces hazards including submarine landslides, shallow gas accumulations, and active faulting that can compromise platform foundation integrity. This professional study evaluates seabed stability for a proposed deepwater floating production platform installation using high-resolution marine geophysical data including sub-bottom profiling, multibeam bathymetry, and shallow seismic survey. Multibeam bathymetric data were processed to produce a 1-metre resolution digital elevation model of the seabed within a 25-square-kilometre area centred on the proposed installation. Sub-bottom profiling using an EdgeTech chirp system acquired records to 60 metres below the seabed, identifying a sequence of acoustically stratified hemipelagic sediments punctuated by chaotic reflectors interpreted as debrite units from past slope failures. A shallow gas anomaly characterised by acoustic turbidity and bright spot reflections is identified in the sub-bottom profiles at 15 to 30 metres depth in the northeastern sector of the survey area. The proposed platform footprint was re-evaluated against these hazard maps, confirming that the platform centre can be positioned to avoid the gas anomaly while maintaining the designed mooring configuration. A geohazard risk assessment is developed for the approved platform location, identifying residual risks and monitoring requirements for the platform installation phase. Keywords: seabed stability, geohazard, deepwater Niger Delta, sub-bottom profiling, platform foundation