| Résumé | Sandwell Engineering Inc. and Canatec Consultants Ltd., both of Calgary, Alberta, were contracted to perform a study of Ice Regimes off the West Coast of Newfoundland. The study had two major aspects, the first was to access and document available ice and environmental data for the geographical area of investigation. The second aspect was to use this ice and environmental data to provide recommendations, where appropriate, on offshore oil/gas drilling structure concepts and structures. The study was to concentrate on data applicable to the offshore oil lease areas on the West Coast of Newfoundland. As part of the project, Canatec accessed and reviewed available environmental data for the West Coast of Newfoundland. Sandwell reviewed offshore oil production structure concepts from ice covered regions of the world. The wave and ice regimes data were used by Sandwell to estimate environmental forces on representative structure geometries. The types of geometries considered were a vertically sided gravity-based structure 100 m by 100 m and a cylindrical structure from 5 m to 20 m diameter. These two candidate geometries were selected because it is impractical to perform load estimate on the many structural concepts that have been proposed for drilling structures in ice covered waters. The candidate geometries were used to investigate, in general terms, which aspects of the environmental forces are dominant as the water depth is varied. The ice force was calculated from either the 1 in 100 year iceberg impact or from a 1 in 100-year first-year pressure ridge. The wave force was calculated using the 1 in 100 year wave for the region. In water depths of less than approximately 30 m, the wave force is governed by the wave breaking action. As the water depth increases, the ice force remains essentially constant whereas the wave force increases. This relationship along with the calculations on the various cylindrical structures indicates that structures, which reduce the wave forces, could be considered. Examples of such geometry are multi-legged structures, monocones or monopods. Floating production systems may have difficulty in resisting the ridge ice force or the iceberg force and thus bottom-founded structures may be more appropriate for this region. A summer only production system could be investigated given the relatively long open water season. The ice and wave environment off the West Coast of Newfoundland was compared to other regions of the world. The Canadian and American Beaufort Seas have a more severe ice environment but less severe wave environment. The Grand Banks region have a more severe wave environment but the West Coat of Newfoundland has first-year pressure ridges as the significant ice event rather than iceberg impact. The wave, ice and water depths are similar to that in the Sakhalin region of the Sea of Okhotsk. This suggests that designs and concepts for that region may be applied to the West Coast of Newfoundland. |
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