Mooring System Integrity Challenges and Repair Experience of South China Sea Floating Production Units

2015 ◽  
Author(s):  
Liu Yiyong ◽  
Mao Jiayou
Keyword(s):  
South China Sea ◽  
South China ◽  
Mooring System ◽  
China Sea ◽  
System Integrity

Fundamental Analysis for the SWING Motion of Single Moored FPSO in South China Sea

2012 ◽  
Author(s):  
Yu Ma ◽  
Zhiqiang Hu ◽  
Yan Qu
Keyword(s):  
South China Sea ◽  
Model Test ◽  
South China ◽  
Hydrodynamic Model ◽  
Low Frequency ◽  
Full Scale ◽  
Mooring System ◽  
Fundamental Analysis ◽  
China Sea ◽  
Short Period

FPSO moored by STP mooring system plays a dominate role in oil and gas production in South China Sea. To study its hydrodynamic characters, a joint industry project on full scale measurement for Fenjin FPSO, headed by Shanghai Jiao Tong University and sponsored by CNOOC, was initiated in October 2007 and lasted for 25 months. During the project, a special phenomenon, named as SWING, was noticed. When a SWING happened, the FPSO’s heading angle would change greatly within a relatively short period, beyond the normal range of the weather-vane effect. Due to the large low-frequency motion, the tension forces of mooring system would increase greatly. Also, it may lead to positioning failure during the tandem offloading operation. So, the SWING motion is a great threat to the safety of FPSOs. A preliminary prediction for its cause as well as a fundamental analysis of its hydrodynamic mechanism is completed in this paper. According to the statistical results of the SWING based on the Fenjin’s motion data during the full scale measurement as well as the corresponding wind wave and current data in the same period, a plausible prediction for its cause is provided. It is pointed out that the change of direction and velocity of the current within a short time might be the cause of SWING. The research for the mechanism of the SWING is carried out through both the methods of analytical analysis and the model test. A hydrodynamic model is built to simulate the low-frequency motions of FPSO in time domain. And an in-house MATLAB program is written on the basis of the hydrodynamic model, to do the calculation. Analysis results are compared with the full-scale measured data, to prove the cause prediction. Furthermore, on purpose of validating the program, a model test was conducted in Deepwater Offshore Basin in Shanghai Jiao Tong University. Several different current velocities were chosen in the test. The program results show a good agreement with both the data of full scale measurement and the model test results, which indicates that the hydrodynamic model and the code are both credible.

Research and Design on Internal Turret Mooring System of FPSO in South China Sea

2014 ◽  
Author(s):  
Liu Huaxiang ◽  
Li Da ◽  
Bai Xueping ◽  
Wang Jianping ◽  
Zhang Baolei
Keyword(s):  
South China Sea ◽  
System Design ◽  
South China ◽  
Design Procedure ◽  
Design Parameters ◽  
Design Criteria ◽  
Mooring System ◽  
Environmental Condition ◽  
China Sea ◽  
Research And Design

This paper mainly introduced the research and design procedure, method and conclusion for internal turret mooring system of FPSO in South China Sea. According to the environmental condition characteristic and operating experience of FPSO in South China Sea and other reasons, the permanent internal turret mooring system with disconnected function is recommended as the final scenario after comparison with the other internal turret systems including disconnected system in typhoon condition and permanent system without disconnected function. For the gradually bad environmental conditions such as wind, wave and current in South China Sea, 500-year return typhoon condition is required as the extreme design condition of mooring system. According to the environmental condition distribution and classification requirement, the design standards, rules and corresponding design parameters for 500-year return condition are determined as the basis of mooring system design. The mooring system is very difficult to design because of very shallow water for catenary system and 500-year return typhoon environmental condition in South China Sea. For the problems appeared because of 500-year return extreme design condition and other parameters, a reliable solution was proposed from the aspect of wave characteristics research and got approval from classification society. The new design criteria for mooring system of FPSO in South China Sea is updated and the mooring system design is completed based on the updated design criteria. The research and design procedure and method for internal turret mooring system of FPSO in South China Sea are summarized too. This paper can be helpful to the similar projects in South China Sea.

New Installation Method for Subsea Pipelines in South China Sea

2012 ◽  
Author(s):  
Chi Chen ◽  
Kai Zhang ◽  
Tianxiao Yang ◽  
Ouyang Xiong ◽  
Qiang Tang ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Oil Field ◽  
The Other ◽  
Mooring System ◽  
Safety Zone ◽  
Mooring Lines ◽  
China Sea ◽  
The One ◽  
Subsea Pipelines

The subsea pipelines between two platforms located in South China Sea were required to be replaced. In between the two platforms is a Floating Production Storage and Offloading (FPSO) unit including the mooring system, anchors and Pipeline End Termination (PLET). The new pipelines need to run below the FPSO and the mooring lines. This paper discusses a new installation method for the subsea pipelines in South China Sea. There are technical challenges to install the new 18-km pipelines in Panyu oil field. On the one hand, it needs to ensure a 500-m radius safety zone from the FPSO. The pipeline laying vessel shall not work within the safety zone due to possible interference with anchor lines. On the other hand, the new pipelines have to run below the FPSO and the mooring lines in order to avoid potential interference with existing cable and riser system. This paper considers the existing pipeline installation methods and generates a new method to install the pipelines in South China Sea. A concept of ‘dummy pipe’ is introduced to simulate the installation operation. The paper presents a series of installation sequences including assisting the pipeline laying and pulling, accurately positioning the pipelines, and protecting the existing facility. Figures are used to illustrate the installation deployment. Messenger lines were installed to run below the FPSO. The installation process was monitored. The new pipelines were installed in the field successfully. In addition, this paper further presents some recommendation for future installation practice.

New Semi-Submersible Floating Wind Turbine for South China Sea

2015 ◽  
Author(s):  
RongFu Li ◽  
Xiaoliang Qi ◽  
Wei Gao ◽  
Hui Li
Keyword(s):  
South China Sea ◽  
Wind Turbine ◽  
South China ◽  
Offshore Wind ◽  
Normal Operation ◽  
Mooring System ◽  
China Sea ◽  
Floating Foundation ◽  
Floating Wind Turbine ◽  
Seakeeping Performance

With the demand of renewable energy due to the pressure from environmental pollution and global warming, the wind industry has been growing rapidly over the past decades during which the offshore wind innovation is becoming more and more attractive because of vast offshore wind resources. In this paper, a novel tapered-column semi-submersible floating foundation with economical mooring system is developed to support 6MW wind turbine in South China Sea. The coupled aero-hydro-servo-structural analysis is done in GH-Bladed software to obtain the global dynamic response of the whole floating wind turbine. By combining the derived wind loads with the wave and current induced loads, the global performances of the foundation and attached mooring system under both extreme conditions and normal operation conditions are analyzed in AQWA software. The result reveals that the floating foundation complies with the design standard and meets requirements of wind turbine. This novel patent-pending floating foundation with tapered columns is proved as a successful design with high material efficiency and good seakeeping performance. Also a reliable and efficient design methodology of floating foundation based on optimal cost is provided in this paper which can be used as design reference of floating foundations.

Study on Anchor Leg Installation Sequence of Nanhai Shengli FPSO Under Typhoon Season

2019 ◽  
Author(s):  
Hui Shen ◽  
Huoping Wang ◽  
Weiquan Zhu ◽  
Deyang Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
Time Domain ◽  
The South China Sea ◽  
Mooring System ◽  
The South ◽  
China Sea ◽  
Catenary System ◽  
Typhoon Season ◽  
The Time Domain

Abstract Nanhai Shengli (NHSL) FPSO, which is serviced in the South China Sea, was dry-docking to upgrade its internal turret mooring system in the first half of 2018, and the mooring system was re-hooked up to the FPSO subsequently in July. The whole installation of the mooring system will last for more than a month. Based on the metocean data of the South China Sea and operation experience, the mooring system installation may encounter typhoon conditions. The NHSL mooring system consists a 10-legs catenary system. The installation sequence of anchor legs may affect the performance of the mooring system under different intensity typhoon conditions. Steps in the design process of anchor leg installation sequence are described in this paper. Based on the tension and offset derived from the time domain mooring analysis, an optimized installation sequence is obtained in order that the mooring system has a better ability to withstand typhoon conditions.

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