Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Challenges in S-Lay Installation of Small Size SCRs with Flexible Joint as 2nd End
Song Liu, Yongjun Du and Hui Wang
China Offshore Oil Engineering Company (COOEC)
Tianjin, China

achieve its efficiency, a spool base is required nearby to reduce transit
time to and from the pipe installation location. For S-lay installation
method, onboard welded pipe joints leave the installation vessel
horizontally and are guided over the “stinger” in order to control thedeflection of the pipe in the over-bend region above the pipeline
inflection point. The S-lay installation is a conventional pipelay method
for rigid pipes, which is suitable for large pipe sizes and can be a costeffective of higher pipelay rate solution in comparison with J-lay methodfor deepwater riser and pipeline installations.

ABSTRACTS-lay installation of a 6-inch small-sized SCR with flexible joint
assembly in the 2nd end is investigated in this paper. Due to the huge
difference in external dimensions, weights and bend stiffnesses between
the riser pipe and the flexible joint, passing through the S-lay vesselstinger of the flexible joint assembly poses a big challenge to the strength
integrity of the overbend section of the SCR, especially the steel pipe atthe connection with the flexible joint body. This paper summarizes theengineering approach and FEA analysis work that were carried out inorder to reduce the maximum strain in the critical riser overbend section.
These engineering approach options include design of a long tapered
stress joint type shroud, an extended upper shroud, to facilitate
installation of flexible joint assembly travelling along the stinger. The
latter approach is selected for detailed design which lays the engineering
groundwork for successful pre-laid operation of the 6-inch SCR withflexible joint.

In the field development phase of Lingshui 17-2 deepwater gas field inSouth China Sea, a 6-inch steel catenary riser (SCR) is used to transfer
Monoethylene glycol (MEG) for flow assurance purpose. Theconnection between this riser and the host submersible production
platform is a flexible joint, a riser hang-off component based on a steelstiffened synthetic rubber high-elastic design material. The 6-inch SCR,
together with the flexible joint assembly, was first pre-laid to the seabedin more than 1500m water depth, by the COOEC HYSY201 pipe-laying
vessel using the S-lay installation method. It was later recovered tosurface and hooked up to the platform by load transferring and pull-inoperations. Global configuration of the 6-inch MEG SCR is shown inFig. 1 with flexible joint as the hang-off system.

KEY WORDS: Steel Catenary Riser (SCR), Flexible Joint (FJ), S-Lay,
Bending strain, Overbend

NOMENCLATUREAPIA&RDNVFE
FJOSISCR

Due to the huge difference in external dimensions, unit length weights
and bend stiffnesses between the 6-inch SCR pipe and the flexible joint,
travelling along the S-lay vessel stinger of the flexible joint assembly
poses a great challenge to the strength integrity of the overbend sectionof the SCR, especially the steel pipe at the connection with the flexible
joint body. This paper summarizes the engineering approach andassociated FEA analysis work that were carried out in order to keep thebending strain of the critical riser overbend section within the design
criteria specified by industry code and standard (DNVGL-ST-F101).

American Petroleum Institute
Abandonment and recovery
Det Norske Veritas
Finite Element
Flexible Joint
Oil States Inc.
Steel Catenary Riser

INTRODUCTION

Earlier studies (You, 2020; Hou, 2020) investigated the feasibility of Slay installation for larger size SCRs and pipelines of the Lingshui 17-2
projects, which is determined by vessel hold back tension, winch
capacity and stinger performances.

There are several methods to lay pipeline offshore in deep water region,
which includes S-Lay, J-Lay, Reel-Lay etc. Reel-lay is an extremely
efficient method for the installation of small to middle size rigid pipelines,
with advantages gained by the high production rate as well as thecontrolled welding and inspection conditions onshore. However, to1785