Analysis of Structural Fatigue in Offshore Jacket Platforms Under Environmental Loading Conditions in the Niger Delta Shelf

Offshore jacket platforms in the Niger Delta shallow-water shelf are subjected to complex cyclic loading from waves, currents, and operational activities, which cumulatively induces structural fatigue that is a primary mechanism of platform aging and failure risk. This study analyses the structural fatigue behaviour of fixed offshore jacket platforms characteristic of those operating on the Niger Delta continental shelf, using finite element analysis methods. A representative jacket platform structure is modelled using finite element software, with environmental loading characterised by wave spectral data derived from ten years of recorded metocean conditions in the Niger Delta offshore zone. Fatigue life calculations are performed using a spectral fatigue analysis approach in accordance with the Det Norske Veritas offshore structural standard. Hot spot stress concentrations at critical tubular joints are identified and fatigue life predictions are developed for baseline and deteriorated structural conditions. Results indicate that several joint configurations in the splash zone and water column achieve fatigue life predictions substantially below the intended design service life under realistic metocean loading, particularly when accounting for the effect of corrosion-accelerated stress concentration at weld toes. The study contributes a metocean condition-specific fatigue dataset and finite element validation for Niger Delta shelf structures. Recommendations include revised inspection intervals for splash zone joints and adoption of cathodic protection retrofit for structures approaching mid-life. Keywords: structural fatigue, offshore jacket platform, finite element analysis, Niger Delta, spectral fatigue analysis