Oil companies are considering large Gravity-Based Structures (GBS) as a potential solution to support operations in new offshore oil and gas field developments in the Arctic seas that are designed for year-round production in potentially 100-meter-deep waters. These structures support multibillion-dollar drilling, production, and storage facilities that are typically commissioned with topsides and consumables before entering the Arctic, and are towed with these elements already installed on the GBS to the installation site. However, the tow not only presents a high risk during the installation phase of the platform, but also has a significant influence on the design and cost of the GBS. Movement of these large offshore structures through the Bering Straits and into position at the installation location includes unique risks that result from the minimal precedence of these tows and the scarcity of local support and contingency ports. This situation suggest that typical approaches to risk identification, design criteria development, and application of risk mitigation approaches may merit reevaluation. This paper will discuss the logistics related to the movement of these large structures and discuss the various cost- and schedule-related risks that have to be identified to support the early design phases of the GBS.

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