Sammendrag
One of the keys to an efficient loading of oil in the Arctic offshore is probably a subsea solution where the interference with ice is at a minimum. Therefore an attempt to assess the performance of an Arctic Shuttle Barge System including a subsea mooring and loading terminal was done at a model-scale of 1:25 in the Hamburg Ship Model Basin (HSVA) ice tank in 1999. The system consists of a barge of about 120 000 tons loaded displacement and 80 000 tons ballast displacement (90 000 DWT, length overall Loa = 265.5 m,) and a pusher/icebreaker of about 8000 tons displacement (2000 DWT, Loa = 86 m). The pusher serves as the main propulsion and connects/disconnects to a notch in the aft of the barge. The operational performance and forces exerted on the barge, the pusher and the mooring system, including a riser, were investigated. The system was pushed by the pusher through level ice or towed through level ice and pressure ridges by the mooring system. The latter simulated the moored condition in drifting ice. This paper describes the test set-up, procedures and performance of the concept when manoeuvring into the loading position in level ice. The maximum ice breaking force was about 23000 kN during a ridge event. The paper also elaborates on the use of a wedged plough and ice milling propellers to avoid ice from interfering with the mooring lines and riser. Finally we have a brief discussion on how the transhipment at the ice edge could be done.
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