Ice damage zone around the Molikpaq: Implications for evacuation systems

Effective design of an emergency evacuation system from an offshore structure in sea ice conditions must take into account all aspects of the anticipated ice conditions at the site. Evacuation systems are typically comprised of several different components or subsystems. These subsystems allow evacuees a choice in response to the emergency incident onboard the installation, as well as to environmental conditions off the installation. This paper discusses four possible evacuation means—preferred, primary, secondary and tertiary. Of these four techniques, only the preferred means of evacuation is not strongly influenced by the ice regime around the structure. This paper examines these ice regimes and quantifies the size of the broken ice region around a structure for different ice conditions. A large number of parameters affect the size of this broken ice zone including the general ice regime, the existence of a grounded rubble field, the failure mode of the ice, the ice thickness, and the ice roughness. Typical damage zone extent is extremely variable and can be in the order of 25 m from the structure for ice thickness of 1.5 m. This has significant consequences for evacuation systems deployed from the structure.