Evaluation of Safe and Failure Zones of Risers and Mooring Lines of Floating Production Systems

2013 ◽  
Author(s):  
Aldo Roberto Cruces Girón ◽  
Fabrício Nogueira Corrêa ◽  
Breno Pinheiro Jacob
Keyword(s):  
Deep Water ◽  
Production Systems ◽  
Early Stage ◽  
Coupled System ◽  
The Other ◽  
Mooring System ◽  
Mooring Lines ◽  
Global Response ◽  
Design Procedures ◽  
Safe Operating

In recent years, the design procedures of risers and mooring system for floating production systems (FPS) have had more feedback. In this way mooring and risers designers can identify, even in an early stage, the constraints imposed by one system over the other. This work presents an evaluation of the crossing of the information obtained from the analyses of risers and mooring system. Different riser and mooring analysis procedures are applied to a typical FPS for deep water applications. First, failure zones of the riser system are identified, so a safe operating limit zone can be defined. Then, the excursions of the platform are calculated taking into account the global response of the coupled system (hull, mooring lines and risers). Finally, the results are crossed in order to verify if the excursions of the platform are within the safe operating area. The evaluation presented here shows the important of correctly defining the safe operational zones and how the crossing of information can be conservative or not within the design process of mooring lines and risers.

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.

Research on the Optimization of the Offset and the Power Consumption for a DP Assisted Mooring System

2013 ◽  
Author(s):  
Hongchao Wang ◽  
Lei Wang ◽  
Hanlin Liu
Keyword(s):  
Power Consumption ◽  
The Other ◽  
Engineering Practice ◽  
Dynamic Positioning ◽  
Positioning System ◽  
Mooring System ◽  
Mooring Lines ◽  
Positioning Accuracy ◽  
Dynamic Positioning System ◽  
Two Measures

DP assisted mooring system is a new positioning system including mooring system and dynamic positioning system. In this paper, two measures are proposed to reduce the offset and the power consumption of a generic semi-submersible platform which is equipped with a DP assisted mooring system during operation. One is to tighten the windward mooring lines and slacken the leeward mooring lines, the other is to reduce or cancel the forbidden angles of the thrusters adjacent to the failed thrusters. Given that the two measures can both reduce the offset and the power consumption of the semi-submersible unit, it is suggested to combine the two measures together to obtain better positioning accuracy. This paper is helpful to engineering practice.

An Evaluation of the Semi-Coupled Scheme for the Analysis of Floating Production Systems

2014 ◽  
Author(s):  
Aldo Roberto Cruces Girón ◽  
Fabrício Nogueira Corrêa ◽  
Breno Pinheiro Jacob
Keyword(s):  
Deep Water ◽  
Production Systems ◽  
Computational Cost ◽  
The Other ◽  
Coupled Analysis ◽  
Computational Costs ◽  
Analysis Techniques ◽  
Early Design Stages ◽  
Accuracy Of Results ◽  
Low Computational Cost

Analysis techniques and numerical formulations are available in a variety for mooring and riser designers. They are applied in the different stages of the design processes of floating production systems (FPS) by taking advantage of both the accuracy of results and the computational costs. In early design stages, the low computational cost is more valued with the aim of obtaining fast results and taking decisions. So in these stages it is common to use uncoupled analysis. On the other hand, in more advanced design stages, the accuracy of results is more valued, for which the use of coupled analysis is adequate. However, it can lead to excessive computing times. To overcome such high computational costs, new formulations have been proposed with the aim of obtaining results similar to a coupled analysis, but with low computational costs. One of these formulations is referred as the semi-coupled scheme (S-C). Its main characteristic is that it combines the advantages of uncoupled and coupled analysis techniques. In this way, analyses can be performed with very fast execution times and results are superior to those obtained by the classical uncoupled analysis. This work presents an evaluation of the S-C scheme. The evaluation is made by comparing their results with the results of coupled analyses. Both type of analysis were applied in a representative deep water platform. The results show that the S-C scheme have the potentially to provide results with appropriate precision with very low computational times. In this way, the S-C scheme represents an attractive procedure to be applied in early and intermediate stages of the design process of FPS.

Optimal Design Methodology for Multi-Component Mooring Systems in Deep Water

2010 ◽  
Author(s):  
Long Yu ◽  
Jiahua Tan
Keyword(s):  
Optimal Design ◽  
Deep Water ◽  
Design Methodology ◽  
Element Model ◽  
Gas Production ◽  
Mooring Line ◽  
Mooring System ◽  
Offshore Platforms ◽  
Mooring Lines ◽  
Restoring Force

Multi-component mooring systems, one of the crucial equipments of offshore platforms, play an important role in deep water oil&gas production because of relative low cost and light weight. A single mooring line can be constructed by combination of wire ropes, chains, fiber ropes, buoys and connectors etc. and provide adequate restoring force at fairlead point of platforms. Although the static and dynamic analyzing approaches for a determined multi-component system have been studied already, it is still hard to design and predetermine an appropriate mooring system that can satisfy the codes with multi-component lines. Referred to the conventional mooring system design method, this paper brings out an optimal design methodology for multi-component mooring systems. According to quasi-static method, at extreme offset position of the platform, an optimization model for designing the multi-component mooring line with biggest tension in deep water has been provided. Then, with the aid of design wave method and morison equation, a finite element model has been used to calculate mooring line dynamics at each fairlead point in time domain. The nonlinear interaction of mooring lines and seabed has also been investigated. Heave and surge of the platform have also been considered. Both 2D and 3D mooring system models have been built to search the interference of the lines and directional influence of environment loads like current and wave. The paper applied this set of analyzing methods and processes into a deep water semisubmersible serving at South China Sea. Compared with the results calculated by other software, the methodology mentioned in the paper got similar result with less weight and bigger restoring force.

scholarly journals STRUCTURAL BEHAVIOUR OF FULLY COUPLED SPAR–MOORING SYSTEM UNDER EXTREME WAVE LOADING

2014 ◽  
Vol 19 (Supplement_1) ◽  
pp. S69-S77 ◽  
Author(s):  
A. B. M. Saiful Islam ◽  
Mohammed Jameel ◽  
Suhail Ahmad ◽  
Mohd Zamin Jumaat ◽  
V. John Kurian
Keyword(s):  
Response Time ◽  
Deep Water ◽  
Mooring Line ◽  
Mooring System ◽  
Wave Loading ◽  
Extreme Wave ◽  
Spar Platform ◽  
Mooring Lines ◽  
Time Histories ◽  
Fully Coupled

Floating spar platform has been proven to be an economical and efficient type of offshore oil and gas exploration structure in deep and ultra-deep seas. Associated nonlinearities, coupled action, damping effect and extreme sea environments may modify its structural responses. In this study, fully coupled spar–mooring system is modelled integrating mooring lines with the cylindrical spar hull. Rigid beam element simulates large cylindrical spar hull and catenary mooring lines are configured by hybrid beam elements. Nonlinear finite element analysis is performed under extreme wave loading at severe deep sea. Morison's equation has been used to calculate the wave forces. Spar responses and mooring line tensions have been evaluated. Though the maximum mooring line tensions are larger at severe sea-state, it becomes regular after one hour of wave loading. The response time histories in surge, heave, pitch and the maximum mooring tension gradually decreases even after attaining steady state. It is because of damping due to heavier and longer mooring lines in coupled spar–mooring system under deep water conditions. The relatively lesser values of response time histories in surge, heave, pitch and the maximum mooring tension under extreme wave loading shows the suitability of a spar platform for deep water harsh and uncertain environmental conditions.

Numerical Study on Hydrodynamic Behavior of Deepwater Spar Platform with Different Mooring Configurations

2011 ◽  
Vol 137 ◽  
pp. 50-58
Author(s):  
Jin Wei Sun ◽  
Xiu Tao Fan ◽  
Xiao Zheng Wan ◽  
Shi Xuan Liu
Keyword(s):  
Static Analysis ◽  
Numerical Study ◽  
Coupled System ◽  
Element Model ◽  
System Structure ◽  
Mooring Line ◽  
Mooring System ◽  
Performance Study ◽  
Spar Platform ◽  
Mooring Lines

The motion performance of Spar platform and dynamic characteristics for the mooring lines under different mooring configurations have been studied both in static analysis and coupled dynamic analysis. First, 3D hydrodynamic finite element model is built and the effects of the mooring system are taken into account by giving the specified pre-tension, angle and stiffness of the mooring lines on the fairleads. And hydrodynamic analysis of Spar platform is performed by the way of utilizing potential flow theory in frequency domain in order to calculate the hydrodynamic coefficients. Then, static analysis is applied to obtain restoring stiffness curves for the mooring system, structure displacements and mooring line tensions etc.. At last, coupled time domain analysis of the motion response of Spar is conducted for the coupled system and the dynamic tensions of mooring lines are calculated. The research results can be served as a reference for the selection and the performance study for mooring systems during preliminary design.

Innovative Concept of a Drilling and/or Production Platform for Operating in Arctic and Deep Water

2007 ◽  
Author(s):  
Frank Chou ◽  
Susobhan Ghosh ◽  
Kevin Huang
Keyword(s):  
Deep Water ◽  
Winter Season ◽  
Arctic Region ◽  
Mooring System ◽  
Floating Platform ◽  
Mooring Lines ◽  
Arctic Condition ◽  
Strong Current ◽  
Production Platform ◽  
Conical Structure

A concept of an innovative floating platform using a conical structure was originally developed for operation in arctic region. It is called as MCAD (MonoCone Arctic Drilling Platform). The conical structure is used to reduce ice-loading as it facilitates ice to break in flexure while riding the slope of the conical surface. For supporting the weight of the platform, equipment, and ballast, a base structure with sufficient buoyancy is added at the base of conical structure. To ensure the platform with adequate stability, a heavy (solid) ballasting system that can be lowered to adjust the vertical center of gravity of the platform is incorporated in the system. The conceptual platform configuration has been analyzed for a large payload of more than 25,000 ST operating in approximately 125 feet of water depth. In the winter season, the platform is subjected to more than 12,000 ST of ice load. For warmer season the platform has been designed to survive a 45 feet significant wave height with 80 knots wind, and a very strong current of 6 knots. To withstand such magnitude of ice forces, mooring system using 32 lines was designed. For lower ice loads in a milder environment, the number of mooring lines can be reduced considerably. For operating in the warmer season, the platform was analyzed for design environments of operating and survival conditions. The motion responses in these conditions were found to be excellent in comparison to other deepwater concepts in use. With the promising motion response results of the conceptual platform with such a high payload, the concept is expected to provide operating company an alternative for deepwater application as well. Since the concept has been developed for a very large payload, the excess payload may be utilized as storages of produced oil. Mooring system for operating in deep water has been developed, and has been compared with that of the system for arctic condition. This paper describes the concept identifying the salient features. The effects of various features on the design and platform performance are also described. The ballast system with its lowering system makes this concept attractive for easy installation without the assistance of a large derrick vessel, a significant reduction of installation time is also expected. Results of stability, motion and mooring analyses is presented in the paper as well. Preliminary structural analyses were carried out to confirm the viability of the concept in operational, installation and survival conditions.

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.

Cognitive Functioning and Other Discriminatory Variables in Anorexic Patients

2005 ◽  
Vol 27 (1) ◽  
pp. 191-210 ◽  
Author(s):  
Carmen García-Alba
Keyword(s):  
Cognitive Functioning ◽  
Research Study ◽  
Early Stage ◽  
Developmental Period ◽  
The Other ◽  
Model Synthesis ◽  
Consistent Function ◽  
Current Article ◽  
Rorschach Variables ◽  
Underlying Pathology

This study is part of a larger research study (doctoral dissertation), in which a comparative study with adolescent samples is done: 50 anorexic restricting patients (ANP), 50 patients diagnosed with depression (DP) and 50 non patients (NP). The proposed objective is two-fold: 1) To try to clarify the existing relationship between Anorexia (AN) and Depression (D), investigated from diverse disciplines but without conclusive results. 2) To detect in the ANP personality different traits from those of other groups, which should, if possible, allow to detect them at an early stage for an adequate prognosis. The current article presents the Rorschach findings in relation to the cognitive functioning of the ANP. In them, the following has been detected: (1) An information processing similar to that of the other groups, even with a more complete (L ≤ .99), more complex (DQ+↑) and better discriminated (Zd↑) grasp of the stimulus; (2) Mediating processes very similar to those of the other groups, sharing with them the perceptive maladjustments (X–%↑) and an excessive individualism (Xu%↑); (3) A clearly differentiating ideation disorder. Definitely, the ANP use predominantly ideation (M↑), but their thought, usually well-adjusted (MQo↑), presents eventual operations of delusional type (MQnone↑). Above that, their thinking is marked by a great passivity (Mp↑), which makes them more vulnerable to accept ideas without criticizing them and it results in a very inefficient thinking, which spins around these concepts without finding solutions, entering into a sort of ruminating which is completely unproductive. The differences toward the obsessive pathology are established. The discriminant analysis conducted with all the Rorschach variables that resulted as significant throughout the research, provides quite a consistent function which discriminates the ANP: MQnone↑, Mp↑, FD↓, Ma↑, MQo↑, AdjD↑, Sum H↑, (H)↑. Based on this we can understand that these adolescents, being in a developmental period of big changes and disorientations in relation with their own image, confronted with life events, and possibly starting off with some biologic vulnerability: (1) Due to the alterations of their ideation, accept without criticism (Mp) irrational ideas dominating in our culture, in which slimness appears as the only model, synthesis of intelligence, beauty and success; remaining captured in this type of mental activity (MQnone), which they cannot escape nor criticize (Mp), despite they reason adequately on other topics (MQo); (2) Their alterations of self-perception [(H)] make them hide themselves in a fantasized image, which is the axis of their interests and the only thing that really matters to them; (3) The resources they have to decide on behaviors and to finish these deliberately (AdjD), and their scarce tendency to the introspection (FD) lead to their decision of not eating, based on distorted and passively accepted thinking, which has great power and thus, so difficult to modify. Finally, based on the Rorschach data obtained, the hypothesis of a personality disorder as underlying pathology is pointed out.

The Application of UX Research in New Energy Vehicle Innovation

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Menghan TAO ◽  
Ning XIAO ◽  
Xingfu ZHAO ◽  
Wenbin LIU
Keyword(s):  
Early Stage ◽  
Rapid Expansion ◽  
The Other ◽  
Innovative Product ◽  
Stage Of Development ◽  
New Energy ◽  
New Energy Vehicle ◽  
The One ◽  
New Energy Vehicles ◽  
Degree Of Innovation

New energy vehicles(NEV) as a new thing for sustainable development, in China, on the one hand has faced the rapid expansion of the market; the other hand, for the new NEV users, the current NEVs cannot keep up with the degree of innovation. This paper demonstrates the reasons for the existence of this systematic challenge, and puts forward the method of UX research which is different from the traditional petrol vehicles research in the early stage of development, which studies from the user's essence level, to form the innovative product programs which meet the needs of users and being real attractive.

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