A HOLISTIC DESIGN APPROACH FOR CONSIDERING ROGUE BUCKLE FORMATION DUE TO PIPELAY-INDUCEDOUT-OF-STRAIGHTNESS

摘要

As oil and gas reserves become more hostile and more remote, the associated flowline mechanical design faces increasing challenges. The trend is that longer, larger diameter, hotter, and lighter (with increased insulation requirements, and minimal stability issues in deep water) flowlines are required. Global buckling is therefore an increasingly prevalent part of the design process of modern field developments. In order to ensure a robust global buckling design, all potential buckle triggers must be considered. A challenge for this is that imperfections introduced by pipelay can not be known until installation is complete. A common approach is therefore to consider high quality survey data from previous projects to characterise the severity of pipelay features for future projects. This paper considers the effect of pipelay catenary length, pipe-soil interaction, pipeline bending stiffness and vessel motion on the as-laid horizontal imperfections, and consequently details the interrelationship between the causes and effects of the imperfection. Further, there is an interrelationship between the severity of the feature, its resistance to buckling and the level of strain in the post-buckled state. An integrated approach is therefore advocated, to obtain a robust design range of imperfection sizes in a deterministic fashion.