Ice management in support of offshore operations can be separated into two distinct sets of activities: near-field and far-field ice management. The first set encompasses ice breaking activities upstream of the vessel, whereas the second covers ice floe monitoring and forecasting. Near-field ice management has received increased attention recently, but not far-field ice management. In this paper, we present a framework for far-field ice management, recast near-field ice management in a consistent manner, and recommend an integrated alert system for both to provide a rational basis for risk-based decisions for safe offshore operations.
There was never a shortage of challenges to the offshore industry in deep-water or Arctic frontiers. Nowadays, however, the challenge is particularly daunting with the merger of the two frontiers in new Arctic deep-water leases such as those in the Beaufort Sea (Fig. 1a), Chukchi Sea, Kara Sea and elsewhere. The main challenge can be succinctly summarized in two words: station keeping. Take for example the concrete island drilling structure (CIDS, Fig. 1b). This shallow-water mobile offshore drilling unit was designed by Global Marine to withstand about 59,000 tonnes of ice load in around 17m of water depth (Wetmore, 1984). As water depth increases, ice loads do not increase much, but overturning moment does prohibit the use of fixed-base structures beyond a limiting depth of about 100m. In fact, this depth typically delineates the boundary between shallow and deep zones in Arctic waters. This shifts the focus for the developers of those leases to floating platforms and drillships. The next boundary that faces the industry is that of mooring system capacity. Floating systems such as Hoover-Diana (Fig. 1c) are held in place by mooring systems with capacity in the range of 1,000–2,000 tonnes (API RP2SK, 2005). This capacity pales in comparison with ice load magnitude (Fig. 1b), not to mention iceberg loads (Fig. 1d). (Figures are shown in the paper)
