Multi-mode reliability analysis of mooring system of deep-water floating structures

2019 ◽  
Vol 192 ◽  
pp. 106517 ◽  
Author(s):  
Junfeng Du ◽  
Anteng Chang ◽  
Shuqing Wang ◽  
Mingyuan Sun ◽  
Junrong Wang ◽  
...  
Keyword(s):  
Reliability Analysis ◽  
Deep Water ◽  
Mooring System ◽  
Floating Structures ◽  
Multi Mode

Coupled Analysis of Floating Structures With a New Mooring System

2011 ◽  
Author(s):  
Zhiming Yuan ◽  
Chunyan Ji ◽  
Minglu Chen ◽  
Yun Zhang
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Coupled Analysis ◽  
Mooring System ◽  
Full Time ◽  
Analysis Method ◽  
Floating Structures ◽  
Motion Performance ◽  
Improved Performance ◽  
Hydrocarbon Reserves

As the exploitation of hydrocarbon reserves moves towards deeper waters, the floating structures are becoming more and more popular, and the catenary and taut mooring systems are two widespread mooring systems which are used for these floating structures. However, both of them have their inherent drawbacks. The aim of the present work is to develop and validate a new mooring system which will overcome these shortcomings. To this end, the motion performance of a semi-submersible platform is simulated by employing a full time domain coupled analysis method. It is shown that the new mooring system yields very good motion performance when benchmarked against the taut mooring system, and the reasons for this improved performance are discussed. Also, the new mooring system is compatible with the characteristic of catenary mooring system, which eliminates the requirement of anti-uplift capacity of the anchors. The second aim of this paper is to explore the proper water depth in employing this new mooring system. For this purpose, several typical water depths are simulated. It is found that the new mooring system works well both in deep water and ultra-deep water. But, as the water depth becomes deeper, the advantages of the new mooring system are reduced.

High Holding Power Torpedo Pile: Results for the First Long Term Application

2004 ◽  
Author(s):  
Jairo Bastos de Araujo ◽  
Roge´rio Diniz Machado ◽  
Cipriano Jose de Medeiros Junior
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Field Tests ◽  
Free Fall ◽  
Mooring System ◽  
Holding Power ◽  
Campos Basin ◽  
Anchoring System ◽  
Very High

Petrobras developed a new kind of anchoring device known as Torpedo. This is a steel pile of appropriate weight and shape that is launched in a free fall procedure to be used as fixed anchoring point by any type of floating unit. There are two Torpedoes, T-43 and T-98 weighing 43 and 98 metric tons respectively. On October 2002 T-43 was tested offshore Brazil in Campos Basin. The successful results approved and certified by Bureau Veritas, and the need for a feasible anchoring system for new Petrobras Units in deep water fields of Campos Basin led to the development of a Torpedo with High Holding Power. Petrobras FPSO P-50, a VLCC that is being converted with a spread-mooring configuration will be installed in Albacora Leste field in the second semester of 2004. Its mooring analysis showed that the required holding power for the mooring system would be very high. Drag embedment anchors option would require four big Anchor Handling Vessels for anchor tensioning operations at 1400 m water depth. For this purpose T-98 was designed and its field tests were completed in April 2003. This paper discusses T-98 design, building, tests and ABS certification for FPSO P-50.

Coupled Dynamic Analyses of Deep-Water Semi-Submersible With New Spread Mooring System

2021 ◽  
Author(s):  
Srinivasan Chandrasekaran ◽  
A. K. Jain ◽  
Azeem Uddin Syed
Keyword(s):  
Deep Water ◽  
Mooring System ◽  
Dynamic Analyses

Reliability analysis of mooring lines for floating structures using ANN-BN inference

2020 ◽  
pp. 147509022092520
Author(s):  
Yuliang Zhao ◽  
Sheng Dong ◽  
Fengyuan Jiang
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Reliability Analysis ◽  
Failure Probability ◽  
Environmental Data ◽  
Mooring Lines ◽  
Widespread Application ◽  
Floating Structures ◽  
Extreme Response ◽  
Artificial Neural

The harsh marine environment is a significant threat to the safety of floating structure systems. To address this, mooring systems have seen widespread application as an important component in the stabilization of floating structures. This article proposes a methodology to assess the reliability of mooring lines under given extreme environmental conditions based on artificial neural network–Bayesian network inference. Different types of artificial neural networks, including radial basis function neural networks and back propagation neural networks, are adopted to predict the extreme response of mooring lines according to a series of measured environmental data. A failure database under extreme sea conditions is then established in accordance with the failure criterion of mooring systems. There is a failure of mooring lines when the maximum tension exceeds the allowable breaking strength. Finally, the reliability analysis of moored floating structures under different load directions is conducted using Bayesian networks. To demonstrate the proposed methodology, the failure probability of a sample semi-submersible platform at a water depth of 1500 m is estimated. This approach utilizes artificial neural networks’ capacity for calculation efficiency and validates artificial neural networks for the response prediction of floating structures. Furthermore, it can also be employed to estimate the failure probability of other complex floating structures.

Coupled Dynamic Analyses of Deep-Water Semi-Submersible With New Spread Mooring System

2020 ◽  
Author(s):  
S. Chandrasekaran ◽  
Arvind Kumar Jain ◽  
Syed Azeem Uddin
Keyword(s):  
Fatigue Life ◽  
Deep Water ◽  
Production Systems ◽  
Irregular Waves ◽  
Mooring System ◽  
Mooring Lines ◽  
Dynamic Positioning System ◽  
Exploration And Production ◽  
Ocean Environment ◽  
Offshore Oil

Abstract Offshore complaint structures dominate the deepwater oil exploration and production due to their adaptive geometric form and well-established construction practices. Semi-submersible is one of the widely preferred, floating production systems due to its form-dominant ability, better stability characteristics, and best constructional features. It is usually position-restrained using a dynamic-positioning system (active-restraining) or mooring system (passive-restraining); being less-sensitive to freak ocean environment is an added advantage. The Semi-submersible, chosen for the present study is based on a similar configuration of a 6th generation deep-water Hai Yang Shi You (HYSY) – 981 platforms, commissioned by the China National Offshore Oil Corporation (CNOOC) in 2012. A sixteen-point, spread catenary-mooring without submerged buoy (case-1) in the form of chain-wire-chain type configuration is used for position-restraining. Response behavior of the semi-submersible with a conventional spread catenary-mooring system with a submerged buoy (case-2) is compared. API spectrum is used for computing wind loads, while the JONSWAP spectrum is used to represent irregular waves for various directions of wave heading. The effect of non-linearly varying current is considered up to 10% of water depth. Numerical analyses of the semi-submersible are carried out under 10-years, and 100-years return period events using Ansys Aqwa. Under wind, wave, and current loads, motion responses of the Semi-submersible at 1500 m and 2000 m water depths are investigated for both the cases in time-domain. Dynamic mooring tension variations arise from the environmental loads are further investigated for a fatigue failure using the S-N curve approach. It is found that the fatigue life of the mooring lines after the inclusion of the buoy is enhanced. It was also observed that, during failure of mooring lines there is an increase in tension of the mooring lines which are adjacent to the failed mooring lines and this is due to the transfer of mooring load and hence reducing their fatigue life.

From Soft Mooring System to Active Positioning in Laboratory Experiments

2020 ◽  
Author(s):  
Thomas Sauder ◽  
Galin Tahchiev
Keyword(s):  
Laboratory Experiments ◽  
Low Frequency ◽  
Positioning System ◽  
Mooring System ◽  
Passive System ◽  
Active System ◽  
Floating Structures ◽  
Main Components

Abstract This paper presents an active positioning system aimed at replacing the classical “passive” soft horizontal mooring system used in seakeeping tests of floating structures. We discuss the limitations of the passive approach, present the main components of the active system, and demonstrate its ability to reproduce results obtained with the passive system. We then show how the active system allow controlling the low-frequency damping applied to the floater. We conclude on the possibilities offered by this apparatus.

Influence of Nonlinear Mooring Stiffness on Hydrodynamic Performance of Floating Bodies

2009 ◽  
Author(s):  
Huilong Ren ◽  
Jian Zhang ◽  
Guoqing Feng ◽  
Hui Li ◽  
Chenfeng Li
Keyword(s):  
Equilibrium Position ◽  
Equations Of Motion ◽  
Offshore Structures ◽  
Hydrodynamic Performance ◽  
Coupled Analysis ◽  
Mooring System ◽  
Main Function ◽  
Ocean Engineering ◽  
Mooring Lines ◽  
Floating Structures

Coupled dynamic analysis between floating marine structures and flexible members such as mooring lines and risers, is a challenging work in the ocean engineering field. Coupled analysis on mooring-buoy interactions has been paid more and more concern for recent years. For floating offshore structures at sea, the motions driven by environmental loads are inevitable. The movement of mooring lines occurs due to the excitation on the top by floating structures. Meanwhile the lines restrict the buoy’s motion by forces acting on the fareleads. Positioning is the main function of mooring system, its orientation effects can’t be ignored for floating structures such as semi-submersible, FPS, and TLP, especially when the buoy’s equilibrium position shifting to another place. Similar as hydrostatic restoring forces, mooring force related with the buoy’s displacement can be transformed into mooring stiffness and can be added in the differential equations of motion, which is calculated at its equilibrium point. For linear hydrodynamic analysis in frequency domain, any physical quantity should be linear or be linearized, however mooring stiffness is nonlinear in essence, so the tangent or differential stiffness is used. Steel chains are widely used in catenary mooring system. An explicit formulation of catenary mooring stiffness is derived in this article, which consists of coupled relations between horizontal and vertical mooring forces. The effects of changing stiffness due to the shift of equilibrium position on the buoy’s hydrodynamic performance are investigated.

Risk Assessment of Subsea X-Tree System

2011 ◽  
Vol 148-149 ◽  
pp. 1000-1006 ◽  
Author(s):  
Chang Yong Wang ◽  
Hong Huan Zhang ◽  
Meng Lan Duan
Keyword(s):  
Risk Assessment ◽  
Risk Analysis ◽  
Reliability Analysis ◽  
Deep Water ◽  
Production System ◽  
Oil And Gas ◽  
Oil And Gas Exploration ◽  
Analysis Process ◽  
Subsea Production System ◽  
Exploration And Development

That the oil and gas exploration and development is extending into deep water proceeds the rapidly shift to subsea production system. However, complex subsea equipment and frequency offshore accidents aroused the concern on the risk assessment of subsea system. The paper illustrates the hazard aspects which should be focused on in the subsea equipment compared with the surface equipment. The hazards identification and risk analysis on subsea X-tree system is carried out. A general risk-prevent process of subsea X-tree system is illustrated, so does the reliability analysis process. Besides, some commendations on subsea detection and maintenance are presented in the paper.

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