Experimental Study on Hydrodynamics of a FPSO in Deepwater Gulf of Mexico

The scaled model testing of a FPSO with its mooring lines and risers for deepwater and ultra-deepwater installation sites is considered to be the most reliable methodology to study the complex hydrodynamic behaviour of the complete system, since it can represent the nearest real environmental conditions and the comprehensive hydrodynamic interactions of the waves, current and wind with the total floating production system. The best technical option, at the present time, is a combination of an appropriate scale model of the FPSO and a suitable level of truncation obtained using a hybrid passive truncated experimental methodology for the mooring lines and risers. This is in order to minimize the various uncertainties in model behaviour and to study the hydrodynamic behaviour of the complete floating system and thus to validate numerical design of prototype systems for installation in deepwater and ultra-deepwater locations. This paper investigates the global response of a specific FPSO to prevailing environmental conditions, based on a hybrid passive truncated experimental methodology for the mooring lines and risers in a specific deepwater location with a water depth of 1000m in the GOM. The main objective of the experiment is to examine the nonlinear effects of the FPSO vessel and its mooring lines and to provide reliable experimental data for subsequent extrapolation to a full scale prototype design. Several case studies were carried out. The FPSO global responses for Full load and Ballast Load conditions with static and dynamic load tension components of the truncated mooring lines were studied for both collinear and non-collinear extreme storm environmental conditions. The experiments revealed that the main horizontal plane motion response of the FPSO (surge) under non-collinear loading condition is almost two-times that of the collinear loading condition.