Shoreline Changes Using Seabed Bathymetric, Sediments Scan and Profiles Observations in Zarum Gas Field Offshore Niger Delta

Abstract

Chuku HC and Odigi MI

Seabed bathymetry, sediment scan and profiles are relevant geological and hydrographic observations widely used in marine geology to predict shore line changes as it concerns offshore fields development in the Niger Delta. Reliefs and heterogeneous sediment distribution, both across the seabed surface and in the shallow seabed profiles below, were examined. This study of the “Zarum gas Field” in the outer shelf environment offshore eastern Niger-Delta was from the results of measurements using high fidelity onboard instrumentation: Edgetech 4600 Multibeam and Sidescan, and Edgetech Sub Bottom Profiler. These instruments were side mounted on MV Cosco and towed along survey grids, within the designed corridor with the survey speed of 3knots.Seabed features were interpreted based on the acoustic sound reflectivity and refractions. The bathymetric values were reduced to the lowest astronomical tide, LAT of Opobo River entrance and range from 20.20m-25.89m with a deepening trend from the northwest to southeast caused by seabed current regimes and storm processes affecting the shoreline zones. The sediments of the scan vary from sand, through silt to clay which are of arenitic origin. Weak seismostratigraphic layer of 30m thick was observed below the seabed, which is presently undergoing secondary lithification. The study also shows existence of depressions and sediment fill in them called spud cans which vary between 10m-40m in diameter and debris, associated with previous rig movements; jack up barges and their drags. Observed are some subsea facilities pipelines and jackets. Based on findings, recommendations have been formulated for development of this gas Field.

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