Dynamic Responses of Floating Production Storage and Offloading (FPSO) Vessel Subjected to Random Waves

Floating, Production, Storage and Offloading (FPSO) unit is ship shaped vessel
which is currently used for the production and storage of hydrocarbon in deep water
region. FPSO is more efficient and economical as compared to fixed structure such as
topside and jacket. This is because the installation of pipeline for fixed structure is
expensive and therefore FPSO is more preferred than fixed structure. FPSO is a
floating structure which allows six degrees of motion in surge, heave, sway, pitch, yaw
and roll. It is crucial to possess a study on dynamic responses of FPSO due to
environmental load for excellent station-keeping characteristics. As wave cause the
dominant environmental loads, the evaluation of responses due to random waves is
necessary for the analysis and preliminary design of FPSOs. The model testing of the
FPSO model is performed in UTP Offshore Laboratory to investigate the three degrees
of freedom under action of waves at Malaysian deep water. The same is validated using
finite element analysis of moored FPSO using frequency domain method. The
metocean data is obtained from the Petronas Technical Standards (PTS) for operating
condition which consist of wave height and peak period. The uncoupled analysis of
the FPSO is performed using SESAM suites of programs. Diffraction potential theory
is used to calculate the dynamic responses of FPSO. Hydrodynamic analysis is
conducted to determine the motion of FPSO in surge, heave and pitch motion in
random waves. Wave spectrum is generated using Jonswap spectrum. The motion
responses of the ship is studied by using transfer functions or Response Amplitude
Operator (RAO) and both numerical and experimental results were compared. Since
there are no study has been reported on dynamic responses of FPSO in Malaysian
waters by using SESAM, therefore this study is very useful for the future design of
FPSO and also to ensure the excellent station keeping characteristics in deep water.