Optimising Reeled Pipe Design through Improved Knowledge of Reeling Mechanics

Abstract

Pipeline reeling is a well established method for offshore installation of rigid steel pipelines and catenary risers. The basic process of loading stalks of pipe that have been fabricated onshore onto large reels before transit to the worksite, un-spooling, straightening and lay is well known. However, despite the wide use of this installation method, the actual mechanics of reeling are generally not well understood. This occasionally leads to concerns that a reeled pipeline has somehow been degraded by the process and must be down-rated in comparison to a similar line installed by another method. There is, therefore, a risk of unnecessary over-design of the pipeline.The expanding ultra deepwater market drives the industry towards streamlining its designs to reduce submerged weight and costs. Over-conservatism related to misconception is certainly not beneficial.This paper intends to demonstrate that there is no general reduction in pipeline performance as a result of the reeled installation method, provided that certain items are considered during design, procurement and fabrication process.The argument is constructed by assessing each 'limit state', meaning the fundamental ways that a pipeline can fail (burst, collapse, fracture), and considering the possible effect that reeling may have on each during service, in comparison to other installation methods. The paper makes use of a wide range of supporting data from extensive in-house engineering and testing programme, reference to relevant Joint Industry Projects and the largest reel-lay installation track record in the industry.