Offshore Arctic Pipeline Oil Spill Risk Assessment

Renewed interest in offshore arctic oil and gas has led to the need for pipeline designs able to minimize environmental risk. A risk evaluation was conducted to assess the relative merits of pipeline concept designs for the Liberty Pipeline, which is intended to carry oil from BP/Amoco’s Liberty site to onshore Alaska. The Liberty site is inshore of the Barrier Islands in the Alaskan Beaufort Sea, in 22 feet of water. The offshore portion of the pipeline is 6.12 miles long. Risk was defined as the oil volume expected to be spilled over the 20-year life of the Liberty Pipeline. Risks due to ice gouging, strudel scour, permafrost thaw subsidence, thermal loads leading to upheaval buckling, corrosion, third party activities, and operational failures were evaluated. Failure probabilities were assessed based on analyses of the pipeline’s response and failure criteria that were established. A consequence model was set up to quantify the oil volume released during a pipeline failure, considering the mode and location of failure as well as leak detection systems. The risk was evaluated by summing the product of event probability and consequence for each hazard. The relative risk is discussed for each pipeline design.