Mooring Effect on Wave Frequency Response of Round Shape FPSO

2015 ◽  
Vol 74 (5) ◽  
Author(s):  
C. L. Siow ◽  
J. Koto ◽  
H. Yasukawa ◽  
A. Matsuda ◽  
D. Terada ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Model Experiment ◽  
Wave Frequency ◽  
Mooring System ◽  
Simulation Test ◽  
Mooring Lines ◽  
Motion Response ◽  
Motion Data ◽  
Model Scale ◽  
Round Shape

This paper presents the motions response of moored Round Shape FPSO model due to the wave effect. The proposed of this research is analyzed the possibility of model motion response affected by different mooring system attach to the model. Model experiment was applied in this research to collect motion data for the study. Besides, the numerical simulation using diffraction potential, diffraction potential with Morison Heave correction and ANSYS frequency domain study were also applied in this research to generate comparative data to the experimental results. To investigate the effect of the mooring system to motion response, the model experiment was firstly conducted by attached model scale catenary mooring lines to Round Shape FPSO model. After that, the experiment was repeated by attached model scale taut mooring lines to the same model. The results obtain from the regular wave experiment tests and numerical simulation test were presented in this paper. This research concluded that the mooring systems would not give significant effect to wave frequency motion response after compared the motion result obtain from model experiment conducted using different mooring system.  

Validation of Mooring Simulations (for Mooring Integrity Assessment) With In-Service Tension Measurements

2021 ◽  
Author(s):  
Willemijn Pauw ◽  
Remco Hageman ◽  
Joris van den Berg ◽  
Pieter Aalberts ◽  
Hironori Yamaji ◽  
...  
Keyword(s):  
Numerical Models ◽  
Weather Conditions ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Data Set ◽  
Integrity Assessment ◽  
Motion Data ◽  
Load Cells ◽  
Line Loads

Abstract Integrity of mooring system is of high importance in the offshore industry. In-service assessment of loads in the mooring lines is however very challenging. Direct monitoring of mooring line loads through load cells or inclinometers requires subsea installation work and continuous data transmission. Other solutions based on GPS and motion monitoring have been presented as solutions to overcome these limitations [1]. Monitoring solutions based on GPS and motion data provide good practical benefits, because monitoring can be conducted from accessible area. The procedure relies on accurate numerical models to model the relation between global motions and response of the mooring system. In this paper, validation of this monitoring approach for a single unit will be presented. The unit under consideration is a turret-moored unit operating in Australia. In-service measurements of motions, GPS and line tensions are available. A numerical time-domain model of the mooring system was created. This model was used to simulate mooring line tensions due to measured FPSO motions. Using the measured unit response avoids the uncertainty resulting from a prediction of the hydrodynamic response. Measurements from load cells in various mooring lines are available. These measurements were compared against the results obtained from the simulations for validation of the approach. Three different periods, comprising a total of five weeks of data, were examined in more detail. Two periods are mild weather conditions with different dominant wave directions. The third period features heavy weather conditions. In this paper, the data set and numerical model are presented. A comparison between the measured and numerically calculated mooring line forces will be presented. Differences between the calculated and measured forces are examined. This validation study has shown that in-service monitoring of mooring line loads through GPS and motion data provides a new opportunity for mooring integrity assessment with reduced monitoring system complexity.

Numerical simulation of the mooring capacity comparison of the subsea suspended manifold with two mooring schemes

2022 ◽  
pp. 147509022110701
Author(s):  
Ning Xu ◽  
Honglin Zhao ◽  
Yufang Li ◽  
Yingying Wang ◽  
Shimin Zhang
Keyword(s):  
Numerical Simulation ◽  
Production System ◽  
System Model ◽  
Mooring System ◽  
Conceptual Scheme ◽  
Fluid Density ◽  
Next Generation ◽  
Motion Response ◽  
Steel Catenary Riser ◽  
Steep Wave

The next-generation underwater production system (NUPS) is based on the suspension cluster manifold (SCM) as a new conceptual scheme. SCM mooring stability is essential for establishing NUPS. Therefore, comparing the SCM mooring stability in different mooring systems is vital for evaluating system adaptability. This paper detailed two mooring schemes designed for the SCM, including the steel catenary riser (SCR) mooring system and the new steep wave (NSWR) mooring system. OrcaFlex software was used to establish the mooring system model, analyzing the static motion response of the SCM under the current and fluid density. Furthermore, the mooring system adaptability in the cluster wellhead layout was also evaluated and compared. The results showed that the maximum offset of the SCM with the SCR mooring system was within 2 m under the current, while the deflection of the SCM with the NSWR mooring system was within 1.5° in extreme fluid densities. Furthermore, the SCM with the SCR mooring system displayed superior station-keeping capability in the current, while the NSWR mooring system exhibited better stability when transporting extreme fluid densities and was more adaptable in cluster wellhead layouts.

Numerical Calculation and Model Test Study on a Quay Mooring Semi-Submersible Drilling Platform

2010 ◽  
Author(s):  
Qi Wang ◽  
Xiaopeng Wu ◽  
Haining Lu ◽  
Gang Chen ◽  
Xiaoyuan Wu
Keyword(s):  
Numerical Simulation ◽  
Numerical Calculation ◽  
Static Analysis ◽  
Model Test ◽  
Environmental Conditions ◽  
Dynamic Effect ◽  
Mooring System ◽  
Mooring Lines ◽  
Nonlinear Characteristics ◽  
Test Study

This paper introduces the study in both numerical calculation and model test of a Semi-submersible drilling platform moored along the quayside of Shanghai Waigaoqiao Shipbuilding Co. Ltd. (SWS). To obtain reliable quay mooring system for a SEMI in the out-fitting condition, complicated factors, such as a barge is applied between the SEMI and the quayside, quayside has practical limited conditions, nonlinear characteristics of mooring lines and fenders, etc., are firstly discussed. Then based on several simplifications, static analysis about different environmental conditions, normal and typhoon, are carried out, in order to design the preliminary layouts. Later on, model test with the scale of 1:50 is conducted in the basin of Shanghai Jiao Tong University (SJTU). Results between numerical simulation and model test are compared and the dynamic effect created by wave is investigated. Several principles for quay mooring layout of semi-submersible drilling platform have been concluded.

Numerical Simulation of Motion Response of Multi-Floating Body System Considering Different Gap Between TLP and TAD

2020 ◽  
Author(s):  
Zhigang Zhang ◽  
Shanjun Bao ◽  
Zhaogang Ding ◽  
Zhiyuan Wei ◽  
Haibo Sui ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Floating Body ◽  
Engineering Practice ◽  
Mooring System ◽  
Floating Bodies ◽  
Motion Response ◽  
Significant Difference ◽  
Drilling Operations ◽  
Drilling System ◽  
Simulation Results

Abstract Tender-assisted drilling system meets the strict requirements of deck space of the drilling platform, and provides a relatively safe and comfortable working environment for the staff, which has been widely used in drilling operations in recent years. The significant difference between multi-floating body and single offshore platform is that there may be risk of collision between the floating bodies under extreme metocean conditions or in emergency of mooring system failure. In order to prevent the collision during drilling operations, the initial gap between floating bodies should be designed carefully and provide a reasonable scheme to ensure the safety of the drilling system and the feasibility of drilling operations. Therefore, based on the three dimensional potential flow theory, frequency domain and time domain numerical simulation of the motion response of TLP and TAD is carried out according to the marine environment of West Africa with extreme metocean conditions, the effect of different initial gap on the motion performance of floating bodies is explored and the mechanical characteristics of the mooring system are analyzed. Thus, the reasonable initial gap between TLP and TAD is determined by comparing the simulation results. In general, the numerical simulation results of tender-assisted drilling system may provide reference for engineering practice to some extent.

FPSO Mooring Line Integrity Supervising System Based on Motion Data and Natural Frequency Estimation

2021 ◽  
Author(s):  
José Lucas De Melo Costa ◽  
Asdrubal N. Queiroz Filho ◽  
Ismael H. F. Santos ◽  
Rodrigo Augusto Barreira ◽  
Anna Helena Reali Costa ◽  
...  
Keyword(s):  
Frequency Estimation ◽  
Longitudinal Axis ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Natural Period ◽  
Motion Data ◽  
Initial Hypothesis ◽  
The Difference ◽  
Property Losses

Abstract Offshore production facilities play a central role in the oil industry given the growing demand for energy resources. The mooring system of these floating structures is a critical component for safety maintenance. The timely identification of mooring lines failures can prevent environmental pollution, property losses and further system failures. In this paper we propose a system to detect and classify failures of the mooring lines based on the natural period in the longitudinal axis and in the lateral axis of the long drift oscillatory motion of the platform. The proposal starts from the hypothesis that when a line break occurs, the natural period of oscillation of the platform is increased, and this difference may indicate the malfunction of the mooring system. The proof of concept developed for the proposed system demonstrates the potential of using the natural period to detect failures in mooring lines for floating vessels, validating the initial hypothesis that the difference in a natural period appears when a line breaks and that this difference may detect line break.

Prediction of Extreme Tensions in Mooring Lines of a Floating Offshore Wind Turbine in a 100-Year Storm

2015 ◽  
Author(s):  
Wei-ting Hsu ◽  
Krish P. Thiagarajan ◽  
Michael MacNicoll ◽  
Richard Akers
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Wind Turbine ◽  
Test Data ◽  
Green Energy ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Mooring Lines ◽  
Floating Offshore Wind Turbines

Floating offshore wind turbines (FOWTs) contribute to an emerging green energy technology, by exploiting higher and consistent wind speeds above the ocean. There are several challenges facing the design of mooring system of FOWTs, including installation costs, stability of light-weight minimalistic platforms, and shallow depths (50–300m). The extreme tension in mooring lines of a light displacement platform in shallow-water is dominated by snap loads. This is because light pre-tension requirements in the line may be insufficient to prevent the mooring lines from being exposed to wave motion induced slack and shock events. In this paper, we present a comparative analysis of a semi-submersible based FOWT exposed to a 100-year storm condition, based on model test data and numerical simulations of well-known industry standard software. The data was obtained from a 1/50th-scale FOWT with the wind turbine modeled after the NREL 5MW wind turbine. The software, OrcaFlex, was used for numerical simulations of the mooring system. NREL’s FAST software was coupled to OrcaFlex to obtain aerodynamic loads along with hydrodynamic load for FOWT analyses. The numerical simulation of the moored FOWT in a 3-hour storm was executed in both the frequency-domain and the time-domain to determine the dynamic behavior of the platform and mooring system, respectively. Snap–type impact events were observed in both test data and numerical simulation. Tension maxima were fitted into extreme value distributions and comparisons are made between simulated and measured data. It is seen that snap events follow a different exceedance probability distribution compared to the cycle-to-cycle tension maxima.

scholarly journals Transient Responses Evaluation of FPSO with Different Failure Scenarios of Mooring Lines

2021 ◽  
Vol 9 (2) ◽  
pp. 103
Author(s):  
Dongsheng Qiao ◽  
Binbin Li ◽  
Jun Yan ◽  
Yu Qin ◽  
Haizhi Liang ◽  
...  
Keyword(s):  
Service Condition ◽  
Mooring Line ◽  
Mooring System ◽  
Transient Effects ◽  
Floating Platform ◽  
Transient Responses ◽  
Mooring Lines ◽  
Performance Deterioration ◽  
Steady State Responses ◽  
Influence Process

During the long-term service condition, the mooring line of the deep-water floating platform may fail due to various reasons, such as overloading caused by an accidental condition or performance deterioration. Therefore, the safety performance under the transient responses process should be evaluated in advance, during the design phase. A series of time-domain numerical simulations for evaluating the performance changes of a Floating Production Storage and Offloading (FPSO) with different broken modes of mooring lines was carried out. The broken conditions include the single mooring line or two mooring lines failure under ipsilateral, opposite, and adjacent sides. The resulting transient and following steady-state responses of the vessel and the mooring line tensions were analyzed, and the corresponding influence mechanism was investigated. The accidental failure of a single or two mooring lines changes the watch circle of the vessel and the tension redistribution of the remaining mooring lines. The results indicated that the failure of mooring lines mainly influences the responses of sway, surge, and yaw, and the change rule is closely related to the stiffness and symmetry of the mooring system. The simulation results could give a profound understanding of the transient-effects influence process of mooring line failure, and the suggestions are given to account for the transient effects in the design of the mooring system.

Value of information of in situ inspections of mooring lines

2021 ◽  
pp. 1748006X2098740
Author(s):  
Jorge Mendoza ◽  
Jacopo Paglia ◽  
Jo Eidsvik ◽  
Jochen Köhler
Keyword(s):  
Pitting Corrosion ◽  
Value Of Information ◽  
Structural Reliability ◽  
Structural Safety ◽  
Statistical Dependence ◽  
Mooring System ◽  
Mooring Lines ◽  
Corrosion Condition ◽  
Chain Links

Mooring systems that are used to secure position keeping of floating offshore oil and gas facilities are subject to deterioration processes, such as pitting corrosion and fatigue crack growth. Past investigations show that pitting corrosion has a significant effect on reducing the fatigue resistance of mooring chain links. In situ inspections are essential to monitor the development of the corrosion condition of the components of mooring systems and ensure sufficient structural safety. Unfortunately, offshore inspection campaigns require large financial commitments. As a consequence, inspecting all structural components is unfeasible. This article proposes to use value of information analysis to rank identified inspection alternatives. A Bayesian Network is proposed to model the statistical dependence of the corrosion deterioration among chain links at different locations of the mooring system. This is used to efficiently update the estimation of the corrosion condition of the complete mooring system given evidence from local observations and to reassess the structural reliability of the system. A case study is presented to illustrate the application of the framework.

Qualification and Certification of Polyester Rope for Seabed Contact

2017 ◽  
Author(s):  
Øystein Gabrielsen ◽  
Kjell Larsen
Keyword(s):  
Water Flow ◽  
Water Depth ◽  
Test Method ◽  
Mooring System ◽  
Qualification Test ◽  
Mooring Lines ◽  
Norwegian Sea ◽  
Flow Through ◽  
Full Scale Tests ◽  
Certification Requirements

The Aasta Hansteen spar in the Norwegian Sea is designed to be moored with a taut polyester rope mooring system. The water depth at the field is 1300 meters, and due to the short installation season the most efficient hookup is with pre-installed mooring lines, which require the mooring lines to be laid down on the seabed. DNV certification does not allow seabed contact for polyester ropes unless proven that no soil ingress and damage takes place. To be able to certify the ropes Statoil developed a test method including contact with soil, rope movement and forced water flow through the filter construction. Full scale tests were performed with actual rope and Aasta Hansteen soil, both in laboratory and at site. This paper discusses the certification requirements and presents adequate qualification test together with results from testing.

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