Abstract
As the demand for energy resources continues to grow, the oil and gas industry is looking north to the Arctic for discovery and extraction of offshore hydrocarbon resources. In seasonal ice covered waters and regions frequented by icebergs where ice loads are significant; the Gravity Based Structure (GBS) has been shown, in cases, to be the preferred technically feasible solution (e.g. Hibernia, Hebron, Sakhalin 1, and Sakhalin 2). In remote locations, where there may be no pipeline infrastructure or the cost of such infrastructure may be too high, the GBS can be designed to offer storage at a reasonable cost. In some circumstances, a ballasted steel structure might have advantages over traditional steel reinforced concrete structures, as outlined in this paper.
In these areas where ice loads are significant, the majority of installed Gravity Based Structures are comprised of steel reinforced concrete. This paper presents the concept of a steel GBS with a storage option for remote Arctic regions. The proposed structural design of the steel GBS is based on the study of ice loads and associated stability. The sizing, advantages and limitations of the unique hull structure are discussed in this paper. The paper discusses about the design and construction of a steel hull GBS capable of withstanding both first year ice and multi-year ice loads in an Arctic setting, where there is future proposed route for ice-class shuttle tankers. For the purpose of this paper, water depths between 30m and 50m are considered for the design of the structure. Optimized sizing of the GBS for various water depths, in order to achieve an approximate storage of six to eight days of crude oil production, is discussed.
