Updating the Iceberg Load Software Using High Resolution Iceberg Profiles

AbstractIcebergs 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.