Ice Management To Support The Kulluk Drilling Vessel

Abstract

Abstract A second-generation drilling vessel has been constructed to extend the drilling season in the Beaufort Sea through the use of a unique hull design, mooring system and icebreaking support vessels. The unique designs of the drilling vessel, icebreakers and supply boats are described. The Kulluk vessel, designed to drill in open water or newly-formed ice, commenced drilling in August 1983. It was soon called on to cope with the most severe ice conditions in nine years. The ice surveillance and ice management procedures employed in coping with the prematurely severe 1983 ice conditions are presented. Depending on the severity of the ice hazards colour code alerts were triggered which dictated the nature of the drilling operations permissible. A pre-requisite for operations is a knowledge of which ice features present a hazard to the drilling vessel. Operationally, the hazards must be detected using radar and visual reconnaissance from aircraft or vessels. Predictions of the velocity, trajectory and time of arrival of the hazardous features are made based on plots of radar and other information. Action is taken to mitigate the hazards through the use of the four powerful icebreakers and supply boats, biased tensioning of the mooring system, disconnecting the riser or, in the extreme event, moving from the location. The icebreaking vessels work at assigned distances from the drilling unit to either break floes and pressure ridges into less hazardous features or to deflect the floes away from a collision course. The ice management system for the Kulluk was put to a severe test in its first year of operation but it performed admirably well. Introduction The continental shelf of the Beaufort Sea has long been considered to have the potential for major oil and gas accumulations. During the period 1963 to 1969, offshore permits to explore for oil and gas were issued for the majority of the shelf which extends some 125 km to 175 km from shore to water depths of 200 m. The Geological Survey of Canada's average expectations of the hydrocarbon potential of the Beaufort Sea - Mackenzie Delta area are 1347 million m3 of oil and 1865 billion m3 of gas(l). Numerous encouraging hydrocarbon discoveries have been made in the Beaufort Sea since offshore drilling commenced in 1973. The commerciality of reserves will depend on many factors such as pay thickness and other reservoir characteristics' well productivities, reservoir depth, water depth, distance from shore, environmental forces, sea bottom conditions, capital and operating costs, crude oil prices and the fiscal regime. Sea ice conditions in the Beaufort Sea are such that the drilling season from conventional ice reinforced drillships is only 3 to 4 months. The second-generation drilling vessel, BeauDril's Kulluk, was constructed to extend the drilling season by commencing earlier in spring and drilling later in the fall. This increased capability is possible because of the unique designs of the Kulluk and vessels and the ice management procedures. Environmental monitoring and forecasting and vessel performance monitoring are key activities in extending the drilling season.