This paper describes the design, construction and first season's operation of the sister ships M. V. Kalvik and M. V. Terry Fox, the most powerful privately owned icebreakers in the world.
These multi-purpose Arctic Class IV vessel s are designed to support BeauDril Limited's Arctic Drilling Units in the areas of ice management, towing, anchor handling and supply.
In order to achieve the required exceptional ice breaking capabi1ity and flexibility of operation, a specific combination of design features was selected. The first season's experience with the vessels, including ice trials, has shown that their performance meets and in most aspects exceeds the design requirements.
The development by Gulf Canada Resources Inc., of its second generation Beaufort Sea Drilling System for extended season exploratory dri11ing on Gulf' s acreage in the Canadian Beaufort Sea has been described in a number of papers (References 1–3), including two previous presentations at O.T.C.
The primary objective of the Beaufort Sea Drilling System is to accelerate exploration efforts in an area where the ice environment imposes severe restrictions on conventional drilling units. This objective is achieved by extending the drilling season through second generation units designed, as integral parts of a system, to withstand the forces imposed by heavy moving ice.
The floating, moored, conical drilling unit, Kulluk, is designed for an operating season from June 1 to January 31 and is subsequently designated as Arctic Class IV under the Arctic Waters Pollution Prevention Act, whilst the bottom founded moveable caisson unit, Molikpaq, can remain on location year round.
Extension of the drilling season cannot, however, be achieved by improved drilling unit designs alone. In particular, the support of offshore supply vessels with icebreaking capability matching the operating scenario is required.
The requirements for marine support were developed as an integral part of an overall techno economic system design evaluation in 1980. This led to the decision to build four multi-purpose Arctic Class IV icebreaker/supply vessels, two of which would be of exceptional power for the purposes of front 1ine ice management. The vessel s should be capable of giving full support, in the form of ice management, towing, anchor handling and supply duties, to the drilling units through the extended season from June 1 to January 31, with the Molikpaq self-sufficient and standing alone through the remaining four months of Arctic winter. Full year round support would have required Arctic Class VI vessel s which were determined to be uneconomic for the degree of system improvement provided. Two designs were developed in the spring of 1981 and subsequent model tests in open water, level ice and ridged ice, were performed to optimize the hull forms and propulsion systems for the ships intended support duties.
