The Ekofisk Field development by the Phillips Norway Group in the Central North Sea has provided the first practical experience in deeper water pipelining in exposed areas. Work performed by Brown &Root in installing Phase I and Phase II field flowlines during the winter seasons of 1970/1971 and 1972/ 1973 has proven that with careful planning of installations and equipment, qualified supervision, and dedicated and experienced crews, it is possible to perform constructive offshore pipe1aying in fully exposed areas where return to she1tered water is impractical in severe weather, even in the most hazardous season. Many new techniques and improvements on proven systems have been required, and these provide indications of future development possibilities.
The Phillips Norway Group, for which Phillips Petroleum Company Norway is operator, made the initial oil discovery in the Ekofisk area in late 1969. The Ekofisk Field, located in the central North Sea almost equidistant from the U.K., Norway, and Denmark, was the first commercial discovery of oil in the North Sea and the first productive venture away from the now relative security of the southern North Sea.
The author's Company has been active throughout the design, construction and pipelay operation, with the entire network of field pipelines having been or in the process of being laid by Brown &Root. Numerous difficulties have been encountered during the development of the Ekofisk Field, with the most serious being the weather.
The text of this paper consists of a description of the area of operations, the equipment, and the procedures utilized by Brown &Root in the Ekofisk flowline pipelay program to date. In addition, some of the developments planned for future pipelay operations in the deeper, rougher waters of the North Sea are discussed.
Of the various offshore areas of the world where the authors' Company operates some experience more violent weather conditions than the North Sea on occasion, but it is the consistency of rough weather in the North Sea which has made it a severe and difficult area for offshore construction.
The "North Sea Pilot", published by the Hydrographic Department of the Admiralty, describes two semi-permanent pressure systems which are the major influences on the North Sea conditions. The two systems are a high pressure area in the region of the Azores and a low pressure area in the region of Iceland. The weather pattern, however, is locally very inconsistent: individual days will show one or both pressure systems varying widely from the average condition. The "Pilot", referring to years of observation, indicates that there is no regularity about duration or movement of transient highs and lows or of the fronts associated with them, no direction of movement that does not occur, and this movement can occur at speeds up to 40 knots.