Iceberg disconnect criteria for floating production systems

Abstract

In designing a floating offshore production system to operate in a region with risk of impacts from icebergs, the effectiveness of management and avoidance of detected icebergs may be considered when determining design ice loads. Management can include deflection of encroaching icebergs through towing or use of water cannon. Avoidance would typically consist of disconnecting the floater and moving off site for cases when an iceberg cannot be managed, but could also include moving off site for periods with high numbers of icebergs. There may be grounds for remaining on site in certain cases (e.g., small icebergs in low sea states) if it can be clearly demonstrated that there are no serious risks. This paper discusses issues involved when determining guidelines for remaining on site, including relevant standards and limits states, trade-offs between ice strengthening and operational requirements, and considerations when presented with a threat by a specific iceberg and set of environmental conditions. A probabilistic approach is presented for establishing operational criteria for disconnection that will still ensure target reliabilities with respect to iceberg impact loads are achieved.