Steel Catenary Riser Dynamic Analysis for Deepwater Applications in South China Sea

This paper first describes the functional requirements of the Steel Catenary Risers (SCRs) for the deepwater applications in South China Sea. Spar is assumed to be the floating platform for the study in this paper. SCR wall thickness is preliminarily selected according to the industry codes. Dynamic strength analysis is preformed to verify the riser wall thickness. Fatigue analysis is then carried out to evaluate fatigue strength for the riser. The fatigue analysis covers different sources such as wave motion, ambient current, and Spar Vortex-Induced Motion (VIM). The metocean data in South China Sea are used for the vessel global motion generation. The current data are used for computing the riser fatigue caused by Vortex-Induced Vibration (VIV). Total fatigue damage for the risers is evaluated. Conclusions are finally drawn from the work in this paper.

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Independent Design Verification of Deepwater SCRs for the Application in South China Sea

10.1115/omae2021-63906 ◽

2021 ◽

Author(s):

Hu Yang ◽

Yongming Cheng ◽

Fanli Xu ◽

Ning He

Keyword(s):

South China Sea ◽

Fatigue Damage ◽

South China ◽

Wave Motion ◽

Fatigue Analysis ◽

Strength Analysis ◽

Design Verification ◽

China Sea ◽

Independent Design ◽

Scr System

Abstract Through nearly 30 years of design and implementation, Steel Catenary Risers (SCRs) have been found to have the advantages of relatively low cost and good adaptability to floating platform’s motion. SCRs have been selected as the production and export riser solution for Lingshui 17-2 (termed LS17-2) field in South China Sea, which consists of a subsea production system, a deep-draft semi-submersible, and an export riser/pipeline. This paper investigates independent design verification of deepwater SCRs for the application in South China Sea. This paper first introduces a SCR system for LS17-2 project. The field for this project is located in northern South China Sea, with water depth of 1220m to 1560m. This paper describes the design verification methodology, procedure, riser computer modelling, extreme challenges, findings, and technical discussions. The independent design verification includes riser sizing, adjacent riser interference, cathodic protection, dynamic strength analysis, Vortex-Induced Vibration (VIV) analysis, wave motion fatigue analysis, semi-submersible Vortex-Induced Motion (VIM) fatigue analysis, and riser installation. Sensitivity study was carried out to demonstrate the accuracy of the results and the robustness of the riser design. SCR designs are extremely sensitive to environmental loading and the motion characteristics of a host platform. The independent design verification shows that the riser governing location of global performance is at the riser Touch Down Point (TDP) region. Compression forces in an SCR touchdown area can be caused by extreme or survival load cases. Among the fatigue damage sources, fatigue damage contributions are dominated by wave motion, VIM and VIV. This paper finally summarizes the findings from the independent verification work. It concludes that the SCR system design for LS17-2 development meets the requirements of API 2RD design code.

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Extreme Vertical Deepwater Current Profiles in the South China Sea, Offshore Borneo

29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 4 ◽

10.1115/omae2010-21006 ◽

2010 ◽

Cited By ~ 3

Author(s):

Rizwan Sheikh ◽

Alison Brown

Keyword(s):

South China Sea ◽

South China ◽

Oil And Gas ◽

Extreme Event ◽

Current Data ◽

Empirical Orthogonal Functions ◽

The South China Sea ◽

The South ◽

China Sea ◽

Reliability Method

This paper details a study of extreme oceanographic currents at deepwater locations offshore Borneo in the South China Sea. With the global demand for oil and gas set to rise steadily over the long-term, oil and gas operators are ever more exploring deeper waters in search of reserves. Often, these finds are economically marginal and challenging from an engineering perspective. Offshore Borneo is a typical example of this, where one such challenge is the prediction of extreme current speeds. Indeed, currents in deepwater are more complex and less constant with depth. As a consequence, the vertical profile associated to an extreme event is integral in the design and safe operation of deepwater facilities. Until recent exploration little measured full-depth deepwater current data has been available. With new datasets for multiple offshore locations, current speeds through the water column are approximated using Empirical Orthogonal Functions (EOFs) and their extreme profiles derived using the inverse First Order Reliability Method (FORM). These profiles are then compared with consideration of different types of current events and used as a basis to formulate idealised deepwater design vertical current speed profiles for locations offshore Borneo that are application specific.

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Prototype Data Analysis on LH11-1 Semisubmersible Platform in South China Sea

Volume 1B: Offshore Technology ◽

10.1115/omae2014-24610 ◽

2014 ◽

Author(s):

Yu Du ◽

Wenhua Wu ◽

Yanlin Wang ◽

Qianjin Yue

Keyword(s):

South China Sea ◽

Frequency Domain ◽

South China ◽

Deep Understanding ◽

Frequency Domain Analysis ◽

Mooring Line ◽

Floating Platform ◽

China Sea ◽

Floating Platforms ◽

Prototype Measurement

There are still uncertainties and challenges by using floating platforms as the main oil exploitation mode due to lake of actual drilling experience in South China Sea. In order to ensure the safety of platform operation, large amounts of prototype data are needed for environment and structure analysis. From 2011 till now, a prototype measurement project is carried out on a semisubmersible platform “NanHaiTiaoZhan” FPS. Large amounts of data have been collected including parameters of ocean environmental loading, motions of floater and underwater responses of mooring and risers. In this paper, statistical analysis of floater responses together with marine environmental conditions are carried out for deep understanding of the characteristics of semisubmersible floating platform. In order to study the motion behaviors of floater under harsh storm, the data recorded in a typical typhoon “Nock-ten” are chosen to perform the deep analysis. The measured data, wind, wave, current and floater motions, are analyzed in time-domain and frequency-domain separately. The comparison study of theoretical prediction and prototype measurement result in typhoon weather has been carried out. The data recorded by standalone sensors are processed by program MoorForce. The result of frequency-domain analysis of measured mooring force proves that the significant wave frequency dynamic behavior of mooring line during typhoon weather should be considered in design.

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