This paper presents a simple and cost effective method to control pipeline thermal buckling in the operational phase. The method is based on active use of the straightener system during reel-lay installation in order to create intermittent residual curvature sections in the pipeline. These residual curvature sections form ‘expansion loops’, in which deflection of the pipeline appears, and the result is controlled pipeline deflection and acceptable utilization at these locations under operational loads.
The method was first applied on Statoil’s Skuld project in 2012, using Subsea 7’s reel ship “Seven Oceans” for installation of a 26 km long 14″–16″ dual diameter pipeline in the Norwegian Sea. Implementation was performed at a small cost related to making the straightener adjustments and the effect on vessel time, and eliminated the need for other measures to control thermal buckling of the pipeline. For the Skuld project, engineering analysis demonstrated that the method would be superior to other methods with regards to both robustness and load controlled utilization in the pipeline under operating loads. Inspection survey during operation has verified the suitability of the method. The technique therefore has the potential to become a vitally important reel-lay method to control global pipeline buckling under operating loads.
