Subsea pipelines subject to high pressure and high temperature develop significant compressive axial force and may buckle on seabed. In cases of pipeline limit states within on-bottom buckles do not meet the design criteria, buckle initiation strategy is defined in order to regularly control the lateral buckling along the pipeline route. This design approach with planned buckles is known as controlled lateral buckling principle.

Different techniques have been worldwide adopted to initiate controlled lateral buckling and thus guarantee the buckle formation, sharing the feed-in between buckles, such as the most traditional techniques: snake-lay, sleepers and distributed buoyancy modules. In the last decade, other efficient method with better cost-benefit ratio have been largely used, based on pre-bent sections of the pipeline, i.e. the residual curvature method (RCM).

RCM consists of under-straightening pipeline sections at the straightener during typical reel lay operation, to create a controlled imperfection or out-of-straightness (OOS) at pre-determined locations along the pipeline route. The critical buckling force at residual curvature (RC) sections is less than that of straightened sections, then assuring a reliable buckling initiation strategy. On the other hand, the RCM application in ultra deepwater flowlines is faced as a great challenge of design and installation, mainly due to uncertainties regarding RC section rotation during laying and not optimally landed.

This paper presents a detailed investigation of parameters that might have influence on the RCM performance of the controlled lateral buckling strategy in ultra deepwater flowlines. The performed evaluations are comprehensive and include the formation of RC sections, the deployment from the installation vessel to seabed and the as-landed configuration check on seabed. Thus, control and verification of key parameters during installation and flowline post-lay survey ensure that the as-landed RC sections will buckle as intended during operation and strain levels will be within the allowable limits.