Four ice breaking vessels on location may have been more a show for the gallery than a real need.
The two rigs used weren't designed to operate in any kind of heavy ice in the first place. No icebergs drifting in this area and no heavy ice pack in the drilling season. A few growlers may be seen in the early and late parts of the season. (No, not THAT kind of Growlers)
If ice drifts should close in they would disconnect the LMRP and move the rig(s)away from the drill site, leaving the BOP stack in place.
In this respect the Ice breaking capabilities of the secondary IM vessels would not be tested as their role was to recover anchors. As the drilling units had far less ice capability they could not remain on location in heavy ice.
So the fact is:
A) In worst case anchor chains/wires would have been slipped and the units escaped before any heavy drift ice was experienced.
B) There were NO possibility that the rig(s) would be on location long enough for heavy new ice to form on and around the drill site.
Q: How can a "Singaporean" know anything about drilling operations in the Arctic? Because I was part of the planning team for Norsk Hydro for a drilling campaign close to Bear Island in 1990, using the Polar Pioneer. The same scenarios were faced there then.
PS> We also planned the logistics for an on-shore drilling campaign on Spitzbergen, which had to be done in the dead of winter, not to damage the permafrost. This involve moving the rig and supplies to Svea before the ice got too thick. Contingency plan involved using a Russian nuclear ice breaker at USD 150,000/day, which was a large sum than.
PPS> Living in Singapore doesn't mean I only worked in S.E.Asia.