Northstar Development Pipelines Limit State Design and Experimental Program

BP Exploration (Alaska) Inc. (BPXA) and its Northstar Project Alliance contractors started field construction of the Northstar development in January 2000 (Lanan et al. 2000). In April 2000, the offshore section of the Northstar pipeline reached Seal Island, located in 11 m water depth Northwest of Prudhoe Bay. Seal Island is in the Beaufort Sea, 9.7 km offshore from the shore crossing at Point Storkersen, on the North Slope of Alaska. Design, testing and permitting activities required multiple years leading up to this first of it kind pipeline construction project. Figure 1 shows the offshore pipeline welding spread working on the floating sea ice surface, similar to the conventional procedures used on the overland portion of the Northstar pipeline. This paper presents the limit state design of the offshore pipelines and the associated full-scale experimental program, which demonstrated that the pipelines can safely withstand operational bending strains up to 1.8%.