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 of Fabrication and Integration of Complex Ship Integrated Turret
Jiayou Mao

Huaxiang Liu

Limei Feng

Longxiang Li

Deep Water Engineering & Construction Center, CNOOC Ltd. Shenzhen
Shenzhen, Guangdong, PR. Chinaand run up into the swivel stacks. The Liuhua turret is the biggest andmost complex turret ever built and installed in China. Fig.1 shows thegeneral arrangement of the turret.

ABSTRACT
Ship Integrated Turret (SIT) is widely used for FPSO in harshenvironment and deep water applications. In China, all FPSOs located inSouth China Sea are equipped with Ship Integrated Turret mooring
systems. In 2019-2020, CNOOC has developed offshore Liuhua16-2 oilfield project with FPSO HYSY119 equipped with the most sophisticated
SIT systems ever been built and integrated in China. The system isdesigned to host 10 swivel stacks with flow path, power supply, subsea
control and chemical injection for over 26 wells. There has been a lot ofchallenges during the fabrication and integration of this 2800MT turretsystem. Due to big number of risers attached to the turret and criticalvessel to turret load path arrangement, the design had been very
challenging with several significant late design changes which
essentially created critical path schedule clash issues. The very tightfabrication and integration tolerance of the unique single bearing turret
and ten stack swivels into the FPSO presented also unparalleledchallenges to the construction team.

KEY WORDS: ship integrated turret; tight tolerance; dimension
control; deformation; integration

INTRODUCTION
The Liuhua16-2 oil field development is comprised of three oil fields
namely Liuhua16-2, Liuhua20-2 and Liuhua21-2. The threedevelopments were discovered one after another from 2010 through2015. The three fields are located in South China Sea with water depth
around 420m. They are located in a triangle layout with the far mostfields about 30km apart from each other. The field development mode is“FPSO + subsea production systems”. The harsh South China Sea
environment requires that the FPSO to be equipped with ship integrated
internal turret which provides permanent mooring station keeping for theFPSO and weather vanning for the FPSO heading all the time to thefavorable environmental direction. The second function of the turretsystem is to provide interfacing paths from subsea to topside. Due to thelarge number of oil wells, each well is equipped with dual electricalsubmersible pumps, each oil field is provided with dual flow lines. Allof these made the turret interface with high complexity. In total there are
17 hang off lines on the turret, namely 6 risers, 3 umbilicals and 8multicore subsea power cables. All of them enter the turret from bottom

Fig.1 The general arrangement of liuhua turret

TURRET DESIGN
The design of such a complex turret was proved to be challenging. From
the design environmental condition to detail structural interfaces
connecting to the FPSO moon pool and subsea functional interfaces areto be managed properly. The turret is connected to both the FPSO andsubsea, so there are two major design interfaces. First the structural andload transferring interface from the FPSO to the turret. The second is the673