Troll oil pipeline: Design solutions for crossing very uneven seabed
- Snamprogetti S.p.A., Fano (Italy)
- Statoil, Stavanger (Norway)
Troll Oil Pipeline Development Project is relevant to a 86 km long pipeline that goes from Troll B platform to the Mongstad refinery on the Norwegian coast. The last 25 km toward the coast, inside Fensfjord feature a very deep and uneven seabed with a maximum water depth of 540 m and a very sharp gradient that goes from a depth of 290 to 540 m over only 2 km between KP 62 and 64. Further, the seabed geology is characterized by extensive sections with very soft clay where rock emergers form the soft bed-material for several meters. The pipeline route, designed with extreme accuracy to avoid the worst seabed unevennesses (Indreeide et al. 1996), frequently includes short radii unstable curves. The operating condition of the carried fluid is also extreme for a pipeline laid on such an uneven seabed. In spite of the deep water, even the environmental data are severe as the seabed currents may exceed 1 m/s in the most uneven area (between KP 60 and 65). This paper describes the following items: (1) the design solutions selected to face the problems related to the above described design basis, i.e., pre-lay gravel sleepers to reduce span lengths as well as stress/strain, lateral counteracts to stabilize short radius curves, and post-lay gravel dumping to reduce span length as well as freeze the pipeline configuration and prevent pipe uplift; (2) the selection criteria based on technical and economic assessment; (3) the design calculations to define where and when the above solutions were to be used, considering strain criteria for static analysis and multispan approach for dynamic analysis; (4) the detail design of sleepers, counteracts and gravel dumping, considering pipeline loads and seabed geomorphology.
- OSTI ID:
- 400908
- Report Number(s):
- CONF-9606279-; ISBN 0-7918-1494-7; TRN: IM9650%%314
- Resource Relation:
- Conference: 14. international conference on offshore mechanics arctic engineering (OMAE), Florence (Italy), 16-20 Jun 1996; Other Information: PBD: 1996; Related Information: Is Part Of OMAE 1996 -- Proceedings of the 15. international conference on offshore mechanics and arctic engineering. Volume 5: Pipeline technology; Murray, A. [ed.] [Nova Gas Transmission, Calgary, Alberta (Canada)]; Bruschi, R. [ed.] [Snamprogetti, S.p.A., Fano (Italy)]; PB: 612 p.
- Country of Publication:
- United States
- Language:
- English
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