Troll Phase 1, large-diameter pipeline design/installation on an uneven seabed
- Reinertsen Engineering ANS, Trondheim (Norway)
- A/S Norske Shell, Bergen (Norway)
Development of the Troll Phase 1 project required landfall, towards an onshore gas conditioning plant, of both 36-in wet gas feed (or import) pipelines and 40-in dry gas export pipelines. The plant is located at Kollsnes on the Norwegian west coast characterized by very uneven seabed topography and severe wave and current conditions. A 3.5 km long subsea tunnel system was constructed for pipeline landfall, leaving a 3.5 km approach corridor towards the tunnel piercing, with still a very uneven seabed to traverse. To safeguard the long-term integrity of the pipelines and minimize costs for traversing the tunnel approach corridor, an extensive optimization between pipeline spanning design, rock support placement and pipeline installation was carried out. Permissible span lengths in the order of 60 to 70 m were defined for the in-service condition on basis of advanced multispan dynamic analyses. Further, strain-based acceptance criteria were utilized for continuously supported pipeline sections, greatly reducing peak leveling requirements. Additional optimization was achieved by the installation of heavier pipe across the deepest depression in the corridor, combined with temporary buoyancy tanks to minimize lay tension. Under the constraints of achievable height of, and optimum location for, rockdumped supports this optimization resulted in a technically feasible, construction-friendly and cost effective solution for the tunnel approach. The article focuses on pipeline spanning and installation aspects. The geotechnical design and offshore execution of rockdumping are covered elsewhere (Brennodden et al., 1996).
- OSTI ID:
- 400901
- Report Number(s):
- CONF-9606279-; ISBN 0-7918-1494-7; TRN: IM9650%%307
- 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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