Icebergs can pose a risk to offshore oil and gas structures in arctic and sub-arctic regions of the world. The Iceberg Load Software (ILS) was developed to determine design loads on structures following the spirit of ISO 19906:2010, helping designers better understand the impact forces and moments the structures must be designed to withstand. The ILS is a fully probabilistic model which accounts for the range of iceberg shapes, sizes and strengths, and environmental conditions expected at the platform location. The model is applicable to fixed structures such as a gravity based structure (GBS), as well as floating structures such as a floating production, storage and offloading (FPSO) vessel. Users can incorporate the effectiveness of iceberg detection, physical management, and disconnection (where applicable for floating platforms) in mitigating the risk of impact with an iceberg. The input relationships and distributions used to characterize the iceberg population are based on measured data typically collected in the region. These data include everything from basic measurements such as iceberg length, width or sail height to the more detailed shape information in the form of complete three dimensional iceberg profiles. In 2012, a major field program was carried out (Younan et al. 2016) with the objective of collecting high resolution iceberg profiles to improve the modelling of iceberg shape. Above water shapes were captured using a photogrammetry technique and were merged with below water shapes collected using multibeam sonar. The end product was a database of 28 high resolution iceberg profiles providing considerable information on iceberg shape. The objective of this study was to use the high resolution iceberg profiles to update models characterizing iceberg shape in the ILS. These includes models for area-penetration, contact location and impact eccentricity. In addition, relationships correlating iceberg draft and mass to waterline length were updated using the new profiles. Example simulations were performed for a generic structure using the ILS to demonstrate the influence of the updated models, distributions and relationships on the output design forces and moments.

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The majority of exploration, development and production offshore Newfoundland has occurred in shallow water. Currently there are two floating production, storage and offloading (FPSO) vessels and one gravity based structure producing oil on the Grand Banks. In recent years, there has been a move to deeper water offshore Newfoundland. There have been significant discoveries at Bay du Nord and Mizzen, and new licence blocks are opening up towards the north and northwest of the existing producing fields. With the move towards deeper water, new challenges arise. Supply facilities, search and rescue equipment and other required infrastructure is much further away. A GBS structure is no longer an option due to the water depth. A disconnectable concrete Spar is being considered as a concept for deep water locations off Canada’s east coast. The platform is designed to withstand iceberg impacts, or to be disconnected and moved off location to avoid impacts from very large ice features. Global design loads (ice crushing forces on the platform) and mooring systems global loads were estimated using a two-step approach. First the concrete Spar was assumed to be fixed (i.e. not able to move during an iceberg impact) and quasi-static global design loads were estimated using the Iceberg Load Software (ILS). The ILS was developed to model iceberg impacts with a fixed platform such as a gravity based structure (GBS). Assuming the concrete Spar to be fixed is a very conservative assumption for floating platforms which are free to move upon impact, albeit limited by a mooring system. Second, the inertial properties of the platform and the mooring compliance were approximated using a one-dimensional timestep model. Since the time domain model is not as efficient computationally, a subset of the simulated impacts from the quasi-static analysis was used as input into the time domain model, and dynamic design loads were estimated. The resulting design loads were used by designers to ensure that the structure meets the requirements of ISO 19906:2010. The end product is a more effective design for the platform, while not compromising the safety of the personnel onboard or the integrity of the structure, mooring system or risers.