Influence of Extreme Wave Spectra on FPSO Motions in the North Sea

Abstract

The dynamic behavior of Floating Production, Storage, and Offloading units under severe environmental loading remains a central concern in offshore oil and gas engineering. This study investigates the influence of extreme wave spectra on FPSO responses in the North Sea, a region characterized by long-period storm seas and significant wave heights exceeding 16 m. Spectral analysis was conducted using representative 100-year return period storm data, capturing spectral moments and bandwidth variations across parametric formulations. A numerical motion-response framework was developed to predict heave, pitch, and roll amplitudes under multi-peaked spectral conditions. Results show that broad spectral bandwidths amplify resonant responses, particularly in roll and pitch motions, while narrow bandwidth spectra concentrate energy within critical natural frequency ranges. The findings underscore the importance of accurate regional spectral characterization in FPSO design, mooring configuration, and operational planning. This paper highlights how North Sea extreme spectra, compared with other offshore regions, impose higher fatigue and station-keeping demands, with implications for safety and reliability in harsh environments.

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