Mooring system design of a floating offshore structure in the arctic region is considered to be extremely important. This paper aims at investigating an optimal mooring system for the Kulluk platform operating in the Beaufort Sea, which has ice-free and ice-covered conditions during the whole year time. In order to complete the layout design of the mooring system to satisfy the year-round operation, both the effect of wave loads and ice loads should be considered. The research establishes a coupled numerical production system composed of the Kulluk platform and mooring system. Wave load is solved by potential flow theory. The slender finite element method is used to compute the tension of the mooring system. The nonlinear finite element method, discrete element method, and empirical formula are compared to analyze ice load. Finally, the discrete element method is selected for the analysis of the Kulluk, and the simulated results are compared reasonably with the field data. When studying the mooring line configurations, quantitative time-domain analysis is carried out, including tension of mooring lines and the motions of the platform under different working conditions. The research work in this paper will provide a reference for the optimal design of the mooring system of the platform operating in the Arctic Sea.

The Arctic region is rich in oil and gas resources, but exploitation of resources there is always facing great challenge. Floating offshore platform is considered as a practical choice for oil and gas exploration in the Arctic deep water regions. One of the key technologies is positioning system design under harsh arctic sea loads. In this paper, a comprehensive design of the positioning system is investigated. A coupled numerical model composed of a mooring-assisted dynamic positioning system and the Kulluk platform is established. 16 different positioning combination forms are selected and investigated. The positioning capability of the coupled system is evaluated by analyzing the platform motion response under different environmental loads, including wave, level ice, and broken ice floes. Wave load is calculated using potential flow theory. Computation of ice load is compared with the finite element method (FEM) and discrete element method (DEM). The dynamic analysis of the mooring system is carried out by using the slender finite element method. The control system of dynamic positioning adopts proportional-integral-derivative (PID) control methodology. It is found that a better positioning system design can reduce the offset by more than 50%, including surge, sway and yaw motion. The results of this study will provide a good reference for the positioning system design of an arctic floating production platform.