This paper examines a preliminary design aimed at evaluating the cost of a gravity based structure in the Sea of Okhotsk. Emphasis is placed on a simplified design for the ice belt zone of the structure in order to reduce the cost. The present work includes a method for estimating first-year ice loads on the structure. The method consists of analysis of actual ice data obtained for the Molikpaq structure in the Beaufort Sea, combined with numerical simulations. The results give global ice loads forl00-year return period and a new pressure-area relation.
The development of oil and gas in the Sea of Okhotsk faces several technical challenges, which reflect on the required capital expenditures. Reducing the cost of drilling structures is considered the key to success of that development. Such costs, however, remain uncertain. The uncertainty is mainly the result of the lack of well-defined functional requirements for the structures and corresponding designs. Ice loads on the structure are particularly considered to have a significant efl~ct on the design and cost of the structure. Therelbre, accurate ice load estimates and reasonable design methods are important Ibr developing cost effective structures. With this background, Japan National Oil Corporation, NK_K Corporation, the National Research Council of Canada (NRC), and Sandwell Engineering Inc. initiated a three-year research project in 1996, aimed at developing accurate estimates of ice loads and a reasonable structure design. In the first year, the influence of ice conditions on the design and ice load estimate methods were investigated. In the second and third years, field measurements were compiled and analyzed in order to obtain more accurate results, and preliminary numerical simulations were compared to other proposed load estimation methods (Frederking et al., 1999a and Timco et al., 1999b).
