Turret-moored floating production storage and offloading (FPSO) vessels have found application in several offshore oil and gas fields in Australia’s North West Shelf (NWS). These vessels are either custom-built or converted tankers, with an internal or external turret. The position of an internal turret is decided based on a number of design considerations, primarily, available deck and interior space, and weathervaning capabilities. It is known that turret position can influence vertical motions and accelerations of a vessel, but this factor has not been given much importance, in comparison with the effects on the horizontal plane motions, primarily surge. This paper presents the results of a pilot study conducted at the Australian Maritime College, Tasmania, to study the vertical motions of a single-point moored FPSO model in waves, while systematically varying the mooring position across the length of the model. The displacement of the vessel was held constant at 50-percent-loaded condition. A single-point mooring system was designed and implemented on the model to simulate the prototype turret mooring system. Results show that the mooring location significantly affects the vertical motions and accelerations of the vessel. Astern turrets were found to produce higher heave and pitch than other locations tested. Although turrets positioned close to the longitudinal center of gravity produced the lowest overall motions, it is suggested that turret position forward of midships be preferred, as it provides a balance between lowering vertical motions and improving weathervaning characteristics.

de Boom, W.C., 1989, “The Development of Turret Mooring Systems for Floating Production Units,” Proceedings, 21st Annual OTC, Houston, TX, Paper 5978.
Comstock, J. P., ed., 1967, Principles of Naval Architecture, SNAME, pp. 634–635, 660–665.
Garza-Rios, L. O., and Bernitsas, M. M. 1997, “Nonlinear Slow Motion Dynamics of Turret Mooring Systems in Deep Water,” Proceedings, Behavior of Offshore Structures (BOSS’97), pp. 177–188.
Hunter, K. C., De Souza, P. M., and Carra, C. J. 1995, “Griffin—A State of the Art FPSO and Some Thoughts on FPSO Trends in Australasia,” Proceedings, 27th Annual OTC, Houston, TX, pp. 59–69.
Jiang, T., and Schellin, T. E., 1988, “Motion Prediction of a Single Point Moored Tanker Subjected to Current, Wind and Waves,” Proceedings, 7th International OMAE, Houston, TX, Vol. 2, pp. 317–326.
Jiang, T., Schellin, T.E., and Sharma, S.D., 1993, “Horizontal Motions of an SPM Tanker Under Alternative Mooring Configurations,” Proceedings, 12th International OMAE, Vol. 1, pp. 123–132.
Lloyd, A. R. J. M., 1989, Seakeeping: Ship Behaviour in Rough Weather, Ellis Horwood Pub. West Sussex, Ch. 21, pp. 425–429.
Mace, A. J., and Hunter, K. C., 1987, “Disconnectable Riser Turret Mooring System for Jabiru’s Tanker Based Floating Production System,” Proceedings, 19th Annual OTC, Houston, TX, pp. 49–56.
Mack, P. C., Gruy, R. H., and Hall, R. A., 1995, “Turret Moorings for Extreme Design Conditions,” Proceedings, 27th Annual OTC, pp. 23–29.
Nishimoto, K., Brinati, H. L., and Fucatu, C. H., 1996, Proceedings, 15th International OMAE, Vol. 1B, pp. 71–78.
, and
B. T.
, “
An Experimental Study of Turret-Moored Floating Production Systems
Journal of Applied Ocean Research
, Vol.
, pp.
J. F.
, and
M. E.
, “
Motion Sickness Incidence as a Function of the Frequency and Acceleration of Vertical Sinusoidal Motion
Aerospace Medicine
, Vol.
, pp.
Tein, Y. S. D., Chantrel, J. M., Marol, E. M. H., and Huang, K., 1987, “A Rational Dynamic Analysis Procedure for turret Mooring Systems,” Proceedings, 19th Annual OTC, Houston, TX, pp. 369–383.
Yashima, N., Matsunaga, E., and Nakamura, M. 1989, “A Large Scale Model Test of Turret Mooring System for Floating Production Storage Offloading (FPSO),” Proceedings, 21st Annual OTC, Houston, TX, pp. 223–232.
This content is only available via PDF.
You do not currently have access to this content.