Development of an Iceberg Impact Load Assessment Tool

Abstract

Icebergs can pose risks to platforms in arctic and subarctic regions. These risks require careful consideration during design, and as well during operations. Platforms must be designed to withstand potential impacts from icebergs, or to disconnect and move offsite to avoid impacts. ISO 19906 allows use of ice management to mitigate iceberg and sea-ice actions. In the case of icebergs, management may include detection, monitoring, towing, disconnection and evacuation. Threat assessment is also a critical input to the iceberg management decision-making process. For example, given one or more detected icebergs and available information on the iceberg and environment characteristics, what is the probability of exceeding platform design ice actions? Based on the threat assessment, better decisions can be made regarding which iceberg to manage, whether more information should be acquired, and whether shut-down or evacuation is needed. This paper describes a new tool developed to estimate the distribution of iceberg impact actions from an encroaching iceberg given concurrent metocean conditions, conditional on impact. The tool can be used in a number of ways depending on the information available to the user. It can be used to assess the threat from a single iceberg or can be used to compare actions from multiple icebergs in the region, or for the same iceberg but with changing weather conditions. The iceberg load assessment tool is demonstrated for several example cases on the Grand Banks, showing the benefit of improved iceberg characterization obtained through rapid iceberg profiling.

Iceberg disconnect criteria for floating production systems

“…The decision criteria should be based on the resistance of the FPSO hull, the extent of knowledge regarding the iceberg size and shape, and the range of ice pressures that could be imparted to the FPSO in the event of an impact. The ability to estimate global impact load distributions is a function of the available information on the iceberg (waterline length, iceberg mass or complete profile), as described in Stuckey et al (2018). For this study, it is assumed that only the iceberg waterline length is known.…”