An Approach to Establish Sea Ice Design Load Cases South of the Barents Sea Polar Front

An approach for deriving sea ice design load cases (DLCs) during rare intrusions of sea ice at the Wisting oil and gas field in the northwestern Barents Sea is described. The DLCs are combinations of sea ice parameter values likely to cause global loads at selected return periods. Wisting is located only ~100 km south of the Barents Sea polar front, which separates cold water at freezing from warmer water south of the front. Historically, sea ice has occurred south of Wisting. However, there are no recent (since 1978) occurrences. Sea ice occurrence probability is calculated through extreme value statistics, but the sea ice characteristics cannot be extrapolated in the same way. Moreover, precise numerical mooring load calculations in broken ice conditions are prohibitively time consuming. An approach to calculate DLCs was devised, involving 1) estimation of statistical characteristics of the sea ice parameters from existing data/literature upstream from Wisting, 2) transformation of the parameter values to the Wisting location, 3) statistical simulation of simultaneous long time series (100 000 years) of all parameters, 4) assessment of the combined effect of the parameters through analytical computation of an ice severity index, as function of the relevant sea ice parameters, and 5) determination of ice severity index values at selected return periods. The corresponding values of sea ice parameters are selected to form a set of DLCs at Wisting, subsequently used in ice tank tests and in numerical simulations to calculate global sea ice loads.


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  • Accession Number: 01745137
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jul 1 2020 5:00PM