Approaches for refining pack ice driving force estimates for the Beaufort Sea

摘要

There are large oil and gas resources in the shear zone region of the Beaufort Sea. Development of these resources would entail many factors for consideration. One of the most important is the ice load on drilling and production platforms. However, there is very large uncertainty on the ice loads in this region due to a clear lack of knowledge of the pack ice driving forces. This pack ice driving force is one of the primary mechanisms that dictate how much force the ice can exert on an offshore platform, even if large multi-year ice floes are present. Improved knowledge of this force would significantly reduce uncertainty in the design ice loads, provide essential baseline engineering knowledge and a more reliable structure, leading to greater regulatory certainty and safer and more economical offshore operations. The pack ice driving force, as a function of width, can be calculated through an equation in the ISO Arctic Offshore Structures Standard. However, a relevant parameter is still poorly defined for this equation and spans a large range. As a result, calculations of driving forces are very uncertain, yet it is the key limiting force mechanism for the Beaufort Sea. This paper presents the results of a study that investigated means of refining uncertainty when calculating pack ice driving forces. An overview of the standard method of determining these forces is given, as well as a discussion of the historical development of, and implications of uncertainty in, calculating the pack ice force. Methods for refining the uncertainty are presented and comparisons are discussed. Numerical modelling studies offer the greatest potential for refining the uncertainty based on cost, usefulness, confidence in the results and study opportunities. The information provided in this paper has applications for refinement of pack ice driving force calculations in current engineering standards. A clear understanding of the magnitude of pack ice driving forces would help to reduce the risk of failure of engineering structures and improve their safety, by enabling a significantly better definition of the anticipated ice loads and the upper limit of the loads for the Beaufort Sea.