Management of Offshore-Ice Operations

Abstract

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 19275, "Ice Management for Ice Offshore Operations," by A.J. Keinonen, AKAC Inc., prepared for the 2008 Offshore Technology Conference, Houston, 5-8 May. The paper has not been peer reviewed. The use of icebreakers in support of offshore-ice operations, and specifically their efficiency in support of vessel-shaped floating platforms in ice, is discussed. New-technology icebreakers equipped with azimuth thrusters achieve high levels of operability with various levels of ice management in a wide range of effective ice thickness. Introduction The oil industry has increased its interest in ice-covered waters. Operations, especially in water deeper than 100 m, use various vessels for drilling or production, with icebreakers supporting their station keeping. The use of icebreakers enables stationary operations in ice to continue with increasing degrees of difficulty. The use of vessels in such offshore-ice operations is substantially different from and more demanding than traditional ice-transit operations or port operations in ice-covered ports and terminals. Offshore-ice projects, which operate in moving pack ice, must ensure that station-keeping operations continue with a high degree of confidence that the station-keeping limits of the floating platform will not be exceeded. Rigorous risk control also is needed to ensure that, if needed, all operations can be stopped and the platform can be removed safely from the location. A high confidence required in the capability to stay on location before such an operation is justifiable. The overall scope of ice management is more accurately "risk management for offshore-ice operations." The following are an integral part of the ice management.Ice and environment intelligenceIce and environment forecastingDefining operability and safe ice operational envelope for the stationary vesselOperational-risk evaluation and assessmentAlerting of operations Only after the above are completed can the actual physical ice management (i.e., breaking and clearing ice) take place. Safe ice-management logic applies to all floating platforms and to any platforms intended to be removable from their stationary operational locations. This paper focuses on the most demanding version of the ice management, operations of ship-shaped platforms. Vessel-shaped platforms are unique in that they offer a highly favorable ice-interaction condition when ice moves in the direction of the vessel. However, the challenge is that if ice comes from the side, the ice loads are so much higher that the benefit of the low loads in one direction is totally lost and operation might not be feasible.