Session: 04-02-02 Rigid Risers II

Paper Number: 79231

79231 - Small Size Steel Catenary Riser S-Lay Installation With Flexible Joint as 2nd End: Difficulties and Solutions 

During Lingshui 17-2 deepwater field development project, 6-inch MEG steel catenary riser (SCR) was pre-laid to the seabed in more than 1500m water depth, by the COOEC HYSY201 pipe-laying vessel through the S-lay installation method. The connection between the riser and the submersible platform uses flexible joint type of design, which is based on a steel-stiffened synthetic rubber high-elastic material as the riser hang-off system.

Due to the huge difference in dimensions, unit weights and stiffnesses between the 6-inch steel riser and the flexible joint assembly, to be passing through the vessel stinger and roller boxes as a 2^nd end, poses a great challenge to the strength integrity of the overbend section of the SCR, especially the steel pipe at the connection with the flexible joint body.

This paper summarizes two different engineering and FEA analysis approaches that were investigated in order to reduce the maximum stress and strain of the critical riser overbend section. These engineering approaches include design of a long tapered stress joint, or an installation aid in large diameters, together with rigging assembly, to facilitate installation of flexible joint passing over the stinger. The latter method was selected for further optimization which laid the engineering groundwork for success installation of the 6-inch SCR flexible joint S-lay as a 2^nd end.

This engineering design and analysis work, in conjunction with project engineering practices, provides meaningful insight and approaches that can be applicable in other S-lay installation project with risers or pipelines in small size in particular.

Presenting Author: SONG LIU COOEC

Authors:

SONG LIU COOEC
Yongjun Du COOEC
Wentai Yu COOEC