Installation of conventional pipelines in areas with very irregular seabed bathygraphy may require large amounts of intervention work, e.g. gravel dumping or dredging. To facilitate pipeline installation in those areas with a minimum of intervention work, a Submerged Floating Pipeline (SFP) could be installed. The concept consists of a floating pipeline, which is anchored to the seabed by inclined or vertical tethers in an off-bottom configuration. The SFP concept is a novel technology and represents an interesting potential for relevant applications. At present, the concept is being developed and evaluated as an alternative for the gas export pipeline system from the Ormen Lange Field located outside Mid-Norway. This paper presents some key features and design aspects that are relevant for the SFP concept. The analyses are carried out based on a 20-inch internal diameter pipeline installed in 1000 m water depth. The study concludes that the SFP concept should be further investigated where installation of conventional pipeline requires very large amounts of seabed intervention works, particularly in deep water.
As development of oil and gas fields is approaching deeper water, the oil companies are also facing several places with very uneven sea bottom. An illustration of such uneven sea bottom topography is given in Figure 1. This specific example is from the deep-water area west of Mid-Norway. Similar examples may also be found West of Africa and in the Far East. Laying a conventional pipeline in such areas requires a large amount of intervention work to reduce the length of free spans. For this reason, an alternative solution has been investigated: A Submerged Floating Pipeline (SFP). The basic idea is to keep the pipeline positive buoyant at all times and anchor the pipeline to the sea floor at regular intervals, as illustrated in Figure 2.
