Deepwater Pipelines: Improving State Of The Art

Abstract

Abstract The paper examines the factors that need to be taken into account in the design of pipelines in deep water, and the extent to which proven construction techniques and existing equipment can be applied. It considers the design problems that arise in deep water, particularly the need for the pipeline to resist external pressure if conventional pipe laying practice is followed. It shows that much can be done with existing knowledge, and explores the problems that remain. Introduction Pipelines are far the most economical method for transporting large quantities of fluids. Other modes are more economical only when the quantities are too small to justify the capital cost of a pipeline, or when political disruptions make it impossible to agree on the construction of a line or to make its continued operation secure and reliable, or in a few instances where technical difficulties. Make it impossible to construct a pipeline. The principal technical difficulties are related to extreme depths, and occasionally to uneven seabed and to high currents. The difficulties are more often political than technical. There is a demand for pipelines in very deep water. The demand comes from various directions. First, there are known to be oil, gas, condensate and hydrate fields in sedimentary basins in several areas, among them the Gulf of Mexico, the Atlantic Ocean west of Shetland, north-east of Greenland and east of the United States, the Davis Strait between Canada and Greenland, the Canadian Arctic Archipelago, and several areas in south-east Asia. Some of these resources are beginning to be developed, notably in the Gulf of Mexico, where the comforting factor of political stability makes up for the high cost of development. It is difficult to imagine that many of these projects will go ahead when the oil price is as low as it is now ($14.14 /barrel on the day this is written), but the world consumes oil at a frightening rate, about 50 million barrels a day, and deep-water reserves will be needed before too long. Second, there are ambitious projects for long-distance transportation of gas. Marine transportation of gas as LNG is less attractive than marine transportation of oil, because about 30 per cent of the original energy content of the gas is lost in the process of liquefaction, transportation and degasification, Gas is such an attractive and convenient fuel and petrochemicals feedstock that once it becomes available economies use gas in preference to other fuels. In the past, much associated gds was flared, an example of irresponsible waste of nature's resources that we must reproach ourselves with, but the demand now is to move gas to markets, even markets at a long distance from reserves. These factors generate demands for long-distance pipelines, and among possible projects are several lines which include deep-water crossings:from Nigeria and Algeria to Europe;from the middle East westward into Europe;from the middle East eastward to Pakistan, India, China and Japan;from Siberia eastward to Japan;from south-east Asia north to China and Japan.