Lateral Buckling Mitigation of Subsea Pipeline by Temporary Winch Pull

Abstract

The design process of lateral buckling has gained in maturity over the last ten years. However the design of any required engineered trigger to control the formation of lateral buckles remains open to a wide range of design concepts (like sleeper, buoyancy modules, snake lay or residual curvature method) with sometimes increasing complexity in either engineering, fabrication or installation. This paper will describe how a lateral deflection initiated by a temporary subsea winch after pipelay can be used as a reliable mitigation with limited impact on the project execution. The interaction between the winch pull and the pipe soil interaction and the consequences on both the post buckle behaviour and reliability design of the mitigation architecture will be presented. The advantages of this technique (decoupling of construction activities between pipelay and lateral buckling mitigation, standard engineering process, no offset from seabed, no additional permanent equipment) and its limitations (stiff pipeline, detailed pipe soil interaction) will be discussed. The operational feedback from several flowlines designed, installed and operated with this winch pull mitigation will be reviewed and the main lessons learnt will be highlighted. It can be concluded that this temporary subsea winch pull is an interesting and cost effective option for lateral buckling initiation of subsea pipelines.