New Offshore and Icebreaker Technologies for the European Research Icebreaker Consortium Figure 1: Side View of the Aurora Borealis
various other benthic robotic tools in fully closed sea-ice cover conditions. Additionally, the adjacent fully-enclosed staging hangar provides abundant weather-sheltered repair, control and maintenance areas for operational personnel and support tools. The aft moon pool is dedicated to drilling operations.
Figure 2: Forward Moon Pool Part of the Vessel with A: Atrium in Cross-section View; B: Sheltered Staging Hangar with Transport System, View from Aft Towards Moon Pool
A
Scientific laboratories are located on several decks around the central moon pool section of the vessel, which is designed in an atrium-like shape with circular walkways and preparation areas (patented). In order to optimally equip the ship for specific scientific missions, containerised laboratories can be loaded and become fully-integrated into the scientific workflow on board.
Icebreaking and Dynamic Positioning Characteristics The Aurora Borealis has a unique hull form. It is optimised for both open water and icebreaking operations, usually features contrary to each other. The hull form provides sufficient discharge of broken ice floes so they do not jam the hull. The underwater bow section aids, with a narrow knife-like stem, in providing an initial cut into ice flows before the entire bow crushes onto the ice with the vessel’s weight. At the waterline, the sides of the vessel are inclined. This balcony-like shape helps the vessel to break the ice while turning on a given position.
Dynamic positioning in open waters with thrust against wind, waves and current with rotatable thrusters is used daily on drilling and supply vessels owned by the oil and gas industry. An entirely different challenge exists with station-keeping in large drift-ice areas created by wind and tides that are subject to quick changes in drift directions and speeds and also by the different ice thicknesses, strengths and press-ice formations.
B
The Aurora Borealis maintains position while the ice drifts against the hull. In order to do this, she is equipped with six fixed-angle retractable transverse thrusters (4,500kW each) in addition to her main propulsion via three propellers (27,000kW each). In this case, the main propulsion units and the thrusters will work together to push the ship against the ice in an ice-breaking mode. The propulsion system is designed for the utmost reliance and robustness in ice conditions and conforms to DP2+ status.
thick ice is needed to enable the deployment of equipment, for example for extended seismic surveys. To prevail in more severe ice conditions, the vessel can break substantially thicker ice, such as pressurised ice ridges of more than 12m, by ramming. This performance allows personnel to work in nearly all ice conditions during wintertime, bad seasons and adverse weather conditions. Before the design of this vessel, no icebreaker was able to operate with similar specifications in polar regions throughout the year.
The two watertight closable moon pools are unique features for a heavy icebreaker (see Figure 1). These measure 7x7m each. They are planned for use during scientific and drilling operations and allow personnel to lower and hoist equipment, keeping it well-protected from the ice and the harsh polar environment (see Figure 2). The forward moon pool provides the opportunity to safely deploy sensitive equipment without the danger of damage incurred by floating ice during deployment. Such equipment may include remotely-operated vehicles, autonomous underwater vehicles or
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A specifically-developed ballast water system will help the ship to break the ice while staying in position. By a partly automated process of movement, the bow of the vessel can be rhythmically raised and lowered in accordance with the advance speed of the ice drift. With this method, the necessary speed for icebreaking can be simulated. This active pitching motion is supported by an active rolling motion.
Extensive model tests by HSVA and Aker Arctic in their ice tanks have validated the icebreaking and dynamic positioning concepts independently of each other in ice fields 1–2.5m-thick ice. These tests on manoeuverability and dynamic positioning capability in ice included turning, breaking out of the channel and keeping station in drifting ice with altering drift-heading angles of the approaching ice. The tests have been run with and without support by trimming and heeling motions.
Site Survey and Drilling Concept
The ice-covered Arctic Ocean not only poses technical challenges for the drilling operations itself. Before starting any such operation, extensive seismic site surveys have to be carried out to characterise the local settings and strata that are to be penetrated.
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 2
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