RIASSUNTO
ABSTRACT
For a typical field development project within the Northern Norwegian Continental Shelf, facing the North Atlantic and Barents Seas, some particular challenges are faced. These relate to the very irregular and partly soft seabed creating free spans, with trawl interaction, and maintenance of the fragile environment in general, including cold water corals. Traditional design approach has called for infill of free spans and trenching of smaller diameter flowlines to eliminate damage risk from trawl gear interaction. On very irregular seabed this may lead to excessive intervention work volumes, with associated high cost. Mitigation actions may be considered in two groups, phased in conceptual/early FEED work and detail engineering actions, respectively. The paper outlines how these challenges may be addressed during the early FEED phase to develop a field layout with focus on minimized intervention cost and risk, while fulfilling also all general layout, installation and operational requirements. Further, for the detail design phase, how new developments within fatigue and trawl design methodology is utilized to allow for significant free spans without pipe support even for clad flowline diameters of 10-12 inches.
INTRODUCTION
The northern Norwegian continental shelf (NCS) facing the North Atlantic and Barents Seas, is considered a very promising area for future oil and gas finds. Operating fields and ongoing development are typically located in water depths of 200-500 m, and often characterized by several smaller isolated reservoirs, with high pressure and high temperature characteristics. Wellstream composition often calls for use of corrosion resistant alloys in flowlines, examples being solid 13% Cr pipe or various clad/lined pipe options. Interesting prospects are currently investigated further out and at greater depths, down to 1200 - 1500 m. Historically, these waters have been among the most productive fish breeding areas on a global scale, with associated significant fishing industry.