Coupled Analysis of Floating Production Systems

Author(s):  
D. L. Garrett
Author(s):  
Aldo Roberto Cruces Giron ◽  
William Steven Mendez Rodriguez ◽  
Fabrício Nogueira Correa ◽  
Breno P Jacob

Abstract This work presents an enhanced hybrid methodology for the analysis and design of floating production systems (FPS). The semi-coupled (S-C) procedure exploits advantages of coupled and uncoupled models, incorporated into a three-stage sequence of analyses that can be fully automated within a single analysis program, presenting striking reductions of computational costs. The procedure begins by determining, through a full nonlinear static coupled analysis, the mean equilibrium position of the FPS with its mooring lines and risers. Then, it automatically evaluates equivalent 6-DOF stiffness matrices and force vectors representing the whole array of lines. Finally, these matrices/vectors are transferred to the dynamic analysis, solving the global 6-DOF equations of motion restarted from the static equilibrium position. This way, the S-C methodology represents all non-linear effects associated to the lines and consider their influence on the dynamic behavior of the hull. However, in some situations it could still overestimate dynamic amplitudes of LF motions, and/or underestimate amplitudes of line tensions. Thus, to improve the overall accuracy, enhanced procedures are incorporated to better represent damping and inertial contribution of the lines. Results of case studies confirm that this methodology provides results adequate for preliminary or intermediary design stages.


Author(s):  
Aldo Roberto Cruces Girón ◽  
Fabrício Nogueira Corrêa ◽  
Breno Pinheiro Jacob

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.


Author(s):  
Stael Ferreira Senra ◽  
Fabricio Nogueira Correa ◽  
Breno Pinheiro Jacob ◽  
Ma´rcio Martins Mourelle ◽  
Isai´as Quaresma Masetti

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1] The present paper begins describing a “basic” classic, uncoupled methodology, and proceeds with comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented. These issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The companion paper [1] proceeds describing a fully coupled methodology, and some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.


Author(s):  
Aldo Roberto Cruces Girón ◽  
Fabricio Nogueira Corrêa ◽  
Breno Pinheiro Jacob ◽  
Stael Ferreira Senra

Nowadays, coupled analysis tools that allow the simultaneous modelling of the hydrodynamic behaviour of the hull and the structural behaviour of the lines of floating production platforms have been increasingly used. The use of such tools is gradually allowing the introduction of some feedback between the design of risers and mooring systems. In the current practice, that comprises the so-called “hybrid” methodologies, mooring designers have been using these tools to consider the influence of the risers on the platform motions. On the other hand, riser designers can use motions that result from coupled simulations for the analysis of each riser. Such integration is already being implemented in the design practice of Petrobras; however, elsewhere the design of risers and mooring systems may still be performed separately, by different teams, therefore not fully exploiting the benefits that the coupled analysis tools can provide. In this context, this work describes an innovative, fully integrated methodology for the design of mooring systems and risers of floating production systems (FPS). This methodology considers different design stages (from preliminary to advanced), integrating the design activities of mooring lines and risers in a single spiral, allowing gains in efficiency and cost reduction. The initial design stages already include a feedback between riser and mooring analyses. The integrity of the risers can be considered in the mooring design by determining their safe operational zones, and therefore, mooring line pretensions can be modified to improve its structural performance. Then, in advanced stages critical design cases for both mooring and risers systems can be identified and rigorously verified by using fully coupled models. The application of the proposed methodology is illustrated with a case study of a typical FPS, representative of the platforms that have been recently considered for deepwater applications. It should be stressed that the methodology described here does not reflect the current design practice of Petrobras. Presently it is merely a proposal that is being studied and assessed; this work comprises the first draft of the methodology, which will be enhanced and consolidated as the result of current and future studies.


2014 ◽  
Vol 48 ◽  
pp. 21-32 ◽  
Author(s):  
Aloísio Carlos de Pina ◽  
Bruno da Fonseca Monteiro ◽  
Carl Horst Albrecht ◽  
Beatriz Souza Leite Pires de Lima ◽  
Breno Pinheiro Jacob

Author(s):  
Fabrício Nogueira Corrêa ◽  
Breno Pinheiro Jacob

Traditionally, the design practice of floating production systems (FPS) employed uncoupled numerical tools where firstly the hydrodynamic analysis of the hull is performed with the lines represented by scalar models (leading to the hull motions); subsequently, these motions are prescribed at Finite Element (FE) models of the lines. Nowadays, it is widely acknowledged that coupled analysis tools should be employed for deep-water applications, considering that the overall behavior is dictated by the interaction between the hydrodynamic behavior of the hull and the structural behavior of the lines. In this context, considering that in some situations the use of coupled formulations can lead to excessive computing times, this work presents a formulation for the analysis of FPS, referred here as the semi-coupled (S-C) strategy. Its goal is to attain faster simulations than a coupled formulation, with better accuracy than usually provided by the classical uncoupled scheme. In this strategy, for each load case a coupled static simulation is performed. From this simulation a global 6-DOF stiffness matrix that represents the array of lines is automatically calculated and added to the global matrix for the subsequent dynamic analysis to solve the equations of motion of the hull. Therefore, this dynamic analysis will adequately consider the nonlinear stiffness contribution of the lines, as well as the effect of the current profile acting on them, all evaluated at the static mean position for each load case. Case studies are presented to compare the computational costs and accuracy of this S-C strategy with coupled formulations.


Author(s):  
Jun Yan ◽  
Qi Su ◽  
Yufeng Bu ◽  
Zhixun Yang ◽  
Qingzhen Lu ◽  
...  

Abstract A new type of umbilical cable named ‘strong-electricity composite umbilical cable’ is composed of electronic cables, optical cables, steel tubes and structural strengthening components. It can be regarded as a key piece of industrial equipment in subsea production systems that provide control functions, strong electric and hydraulic remote transmission. when it is oriented at a power supply with a relatively high rated voltage, power transmission will produce a lot of heat. Then, the cross-sectional temperature increases, which affects the performances of its material and mechanical responses. Therefore, electro–thermal–mechanical coupled analysis is critical for the cross-sectional design of the strong-electricity composite umbilical cable. Accordingly, a multi-physics coupled analysis was performed based on two typical umbilical cable cross-sections. Finite element models were established and subjected to electro–thermal analysis to obtain a temperature distribution of the two sections at different current capacities. Based on results of temperature field analysis, the section models were subjected to thermal–mechanical analysis. The results of the two types of analyses are compared and differences are discussed, which illustrate the multi-physics coupled effect cannot be neglected. The armored layers will relatively reduce the heat dissipation performance, but compared with the umbilical cable model without the armored layers, the model with double-armored layers is less affected by temperature, so its capacity of resistance external pressure is relatively better. The proposed coupled analysis methodology provides a new guidance for the design of the strong-electricity composite umbilical cables.


Author(s):  
Fabri´cio Nogueira Correa ◽  
Stael Ferreira Senra ◽  
Breno Pinheiro Jacob ◽  
Isai´as Quaresma Masetti ◽  
Ma´rcio Martins Mourelle

The objective of this paper is to study different analysis methodologies for the design of floating production systems. The main issues are the use of uncoupled and coupled analysis methods, and the integration in the analysis and design of the mooring system and the risers. This paper is a companion to another paper also presented in the OMAE2002 Conference [1]. That paper describes a “basic” classic, uncoupled methodology, and comments on some refinements in the representation of the behavior of the lines in the motion analysis of the vessel. Comments regarding the introduction of some level of integration between mooring line and riser behavior are also presented in the companion paper [1], and these issues are illustrated with studies applying some of the considered design methodologies to the P-18 semi-submersible platform in Campos basin. The present paper proceeds describing some hybrid methodologies that combine coupled and uncoupled analysis tools, and illustrates their application to a DICAS system for deepwater applications in Campos basin.


Author(s):  
Chul-hee Jo ◽  
Do-youb Kim ◽  
Yu-ho Rho

Flexible risers have been used extensively in recent years for floating and early production systems. Such risers offer the advantage of having inherent heave compliance in their catenary thereby greatly reducing the complexity of the riser-to-rig and riser-to subsea interfaces. Another advantage with flexible risers is their greater reliability. Concerns about fatigue life, gas permeation and pigging of lines have been overcome by extensive experience with these risers in production applications. In this paper, flexible riser analysis results were compared through coupled and uncoupled dynamic analyses methods. A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. For this study, SPM (Single Point Mooring) system for an FSU in shallow water was considered. This optimization model was integrated with a time-domain global motion analysis to assess both stability and design constraints of the flexible riser system.


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