Abstract

The discovery of oil at Prudhoe Bay, Alaska in 1968 and the increased pace of exploration in the Canadian Arctic prompted the formation of a consorti.um, Mackenzie Valley Pipe Line Research Limited, in Canada, to study the problems associated with oil transportation. The problems arose because the oil would normally be warm when produced, and in a conventionally buried line would melt the ground around it. In the Arctic and Subarctic the ground Ls permanently frozen, often contains excess ice and is protected during the warm seasons by an insulating layer of living and dead organic material. When the cover is disturbed or when additional heat is input, melting of excess ice and escape of water causes a volume reduction in the thawed ground. Therefore construction and operation of a warm oil pipeline could cause settlement of the ground creating drainage and erosion problems and stresses in the pipe. Melting of permafrost soil could also cause reduction in its strength and create potential instability in the mass of thawed soil surrounding a buried line on a slope. There would obviously be threats to the integrity of the line. In addition to these technical problems, current awareness of the environment focused attention on a broad spectrum of potential hazards of such a large scale industrial development. Though the importance of environ mental protection is recognized and is receiving careful study, this discussion is confined to Some aspects of research on the technical problems.

An early area of investigation was that of above ground construction methods. Two of the most promising designs were tested over a period of two years near Inuvik, N.H.T. and one, that of a line supported on piles in a continuous zig-zag pattern proved eminently successful. Although the design of a line laid on a gravel pad and covered with gravel left some questions this segment of the test proved very useful in studies of the thermal regime around a buried line.

Theoretical studies of the thawing process on permafrost soil led to the development of techniques for the measurement of properties of preserved cores in both the frozen and thawed states and the design of field tests to gather fundamental data, demonstrate the results of thawing, and provide the basis for reliable design criteria. Significant progress in this area has led to a better understanding of the behavior of permafrost terrain and will enhance the task of route selection. For the latter, comprehensive studies of permafrost occurrence and characteristics have been combined with modern techniques of air photo interpretation to develop a new terrain classification system. This system is currently being tested for reliability.

Construction and operation of a warm oil pipeline will cause some degree of disturbance to the permafrost. The ability to minimize and contain the consequences of such disturbance will depend on the available scientific knowledge and its application to sound engineering design and construction and operation practices. Research to date has lent considerable support to earlier studies which concluded that arctic pipelines were technically feasible.

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