Definition for technical success of iceberg towing operations

Offshore platforms proposed for operation in regions with icebergs must be designed to withstand ice loads associated with impacts for cases where icebergs cannot be managed or avoided. Both fixed and floating systems have been successfully used on the Grand Banks off Canada´s east coast without incident to date. The Hibernia platform is designed to withstand impact loads; these loads were estimated without consideration of the efficiencies of ice management. The Terra Nova and White Rose FPSO´s are designed to disconnect and move off site if threatening icebergs cannot be managed. These systems have ice strengthening, with the benefits of ice management considered in determining the design ice loads. Ice management efficiencies were based in large part on overall towing success rates determined from ice management records. Towing success was based on a number of criteria, including whether the iceberg was obviously deflected from its course and whether downtime resulted. It is expected that in the near future there will be pressures to reduce platform costs in order to make more marginal fields viable, platforms will be installed further north where iceberg and sea ice conditions are more severe and as more platforms come on stream, there will be restrictions regarding where icebergs can be safely towed so as not to increase risks to neighboring installations. As assessment of ice management becomes more critical, it will be desirable to develop more accurate measures of efficiency for assessing both downtime and potential for impacts. In this paper, a number of alternative methods for evaluating ice management efficiency with respect to impact avoidance and the potential influence on ice design loads are explored and criteria for further development of these discussed.