Reliability and Safety of Pipeline Laying by Reeling Technology in Deepwater

Abstract The paper presents the results of reeling pipeline stresses and strains amplification investigation and describes the practical proved method to suppress the phenomenon, prevent a failure, and provide pipelay reliability and safety. Advantages of pipeline laying by reeling are the cause of worldwide use of this method for pipe diameters up to 16-inch and even more in a future. Some time ago there were several occurrences of pipe rupture during reeling in area of pipe properties changes (wall thickness or pipe grade) from previous joint to the next one. The rupture surface inspections have shown significant and unusual overstress in the area as a result of stress / strain reallocation. Stress / strain amplification occurs at any joint with different properties along the pipeline on a reel drum and especially when the connection is leaving a drum surface. The pipeline reeling failures have caused companies significant losses. It is suggested an amplification suppression method by utilizing a special form transition joint between different properties adjacent joints. The presented procedure allows control of the transition joint stress / strain values depending upon joint geometrical and steel property variations. The analysis is based on curvilinear beam non-linear stress - strain consideration and presented in spreadsheet form. The above method has been successfully used during BPX Pompano Phase II Project and Pennzoil Flowline and Riser Project. Introduction Modern subsea pipeline construction uses the most cost-effective methods of installation. The pipelay by reeling technology is one of them providing the construction, acceptable cost and terms. This technology has been used with success for a relatively long time. The method and equipment are adapted now to lay pipeline up-to 16 inches in diameter and probably will be used for pipe-in-pipe assembly installation. Reeling technology is associated with a high level of bending strain, which is often just slightly below pipe shell buckling strain values. The approach is generally acceptable because there is a good reeled pipe axis curvature. Indeed, the curvature is maintained by the reel drum radius magnitude. That is correct until the reeled pipe has unchangeable properties: beam bending stiffness and pipe's moment-to-curvature non-linear characteristic values. If there is any changes in the reeled pipe properties then, the bent around reel drum stiffer pipe section generates the certain moment value, which could not be acceptable for the weaker pipe section being the extension of the stiffer pipe.