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 and Solutions of “FPSO+Subsea” Mode Development for South China Sea
Jiayou Mao

Huaxiang Liu

Huoping Wang

Deepwater Engineering &Construction Center, CNOOC Ltd. Shenzhen
Shenzhen, Guangdong, PR China

favorable due to CNOOC had long experience of FPSO operations aswell as subsea production systems (Li and Ji,2016; Li and He,2016;Mao,2014; Liu and Mao,2015). Both are technically proven andeconomically appealing. However, during the design and project
execution phase, multi technical issues were encountered such as theworld record long distance power supply by direct variable frequency
drive, the 17 dynamic flexibles and umbilicals interferences in the watercolumn due to complex soliton current, the high gas oil ratio challenges
to flow assurance, the complex turret system ever built in China etc. Dueto the criticality of the facilities, a comprehensive monitoring system wasinstalled to the FPSO and mooring to collect environmental data, FPSO
motion as well as mooring line angles. This article is intended to sharethe major challenges as well as solutions we adopted. The project was
successful which achieved first oil in Sept. 2020. Fig. 1 is a field generallayout overview.

ABSTRACT“FPSO+Subsea” mode is a typical offshore oil field development mode.
This mode is suitable for deep water developments where other types offacilities such as jacket platforms or TLPs are either not economically
viable or technically feasible comparing to subsea systems. This mode is
widely used in Brazil’s deep water developments. Jacket platforms +FPSO or Subea tie backs have been the major development mode inSouth China Sea in the past (Yue,2013;Mao and Yang 2016). CNOOC
recently developed its Liuhua16-2 oil field located in South China Sea
by this FPSO+Subsea mode. Due to the complexity of the environment
and the large scale subsea systems with three oil fields and a total of 26
subsea wells, we had faced a lot of challenges during the development
such as complex FPSO turret, long distance subsea tie backs, flow
assurance , pipelines and umbilicals interferences under special South
China Sea soliton currents etc.

KEY WORDS: fpso+subsea; long distance tie-back; flow assurance;
clash check;

NOMENCLATURE
ESP: Electrical Submersible Pump
VFD: Variable Frequency Drive
BMIT: Bottom Mounted Internal Turret
GOR: Gas Oil Ratio

INTRODUCTION
The Liuhua16-2 oil field development is comprised of three oil fields
namely Liuhua16-2, Liuhua 20-2 and Liuhua21-2. The threedevelopments were discovered one after another from 2010 through2015. The three fields are located in South China Sea with water deptharound 420m. they are located in a triangle layout with the far most fields
about 30km apart from each other. During the course of the discovery
various development concepts were studied . including re-developmentof the existing Liuhua11-1 oil field with the new Liuhua16-2 prospects
with TLPs. Due to the TLP technology has never been exercised in China,
there is a question of the suitability of TLP application at the typhoonand soliton prone South China Sea(Mao,2014). With the discovery of all
three oil fields, CNOOC finally decided to develop all of the three
together with FPSO+subsea mode. This development mode is more

Fig. 1 General Layout of Liuhua16-2 oil field

DESIGN VERIFICATIONLong Distance Direct Drive Power Supply
The subsea oil wells are all equipped with dual ESPs powered from the568