Turret-moored floating production systems are sensitive to the effect of non-collinear waves, wind and current. Traditional mooring design recipes often rely on the application of 100-year extreme metocean events where waves, wind and current are assumed to be collinear. Determination of the true effect of non-collinear conditions requires that a proper long-term response analysis be performed. Accordingly, this paper focuses on two aspects of the design of a turret-moored floating storage and offloading unit (FSO) proposed for the deepwater Gulf of Mexico. First, in order to investigate the behavior in extreme weather, the long-term responses were analyzed using a hindcast database of 35 hurricanes that occurred during 85 years in the Gulf of Mexico. Response-based design criteria were proposed for the roll, pitch and chain table vertical motion. Second, in order to investigate the everyday FSO weathervaning behavior and motion responses, a new hindcast database was developed that represents six years of site-specific everyday wave, wind and current (including loop/eddy current effects) conditions. Results of the analysis can be used to develop information about the joint directionality of waves, wind and current to be applied in a fatigue analysis or offloading operability analysis. In addition, valuable insight can be obtained into the expected everyday FSO responses (e.g. roll motion). The results from both analyses can be used in a parametric study to help select an “optimal” turret location.

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