Application of an Alternative Concept in Dynamic Positioning to a Tanker Floating Production System
This paper describes the development of a cost-effective floating production system, comprising a conventional tanker fitted with a dynamic positioning (DP) system to maintain the riser connection to the well head.Reduced costs in the DP system are achieved by using a control strategy based on thrusters at the forward end of the vessel thus allowing the vessel to rotate freely, i.e. weathervane, to the environment. A description of the principles of this control strategy is given.Application of this DP system to a conventional tanker is briefly outlined. Special attention was required in the location of the thrusters in the forward cargo tank and a description is given of the numerical studies and model tests used to optimise thruster location.In order to gain insight into vessel behaviour under such a DP system, simulation studies were carried out and the results correlated with model tests in a wind, wave and current environment. These results indicated the need for a thruster at the aft end of the vessel under certain environmental conditions.The paper concludes with an economic assessment of the operational costs of such a DP system, which together with reduced thruster and power plant costs presents an attractive solution to production from marginal fields.