scholarly journals An Analysis on the Spread Mooring of the Belida FSO Induced by Squall Loads

Kapal ◽  
2020 ◽  
Vol 17 (1) ◽  
pp. 15-27
Author(s):  
M Murdjito ◽  
Inneke Yulistanty Pravitasari ◽  
Eko Budi Djatmiko
Keyword(s):  
Wind Speed ◽  
Water Depth ◽  
Time Domain ◽  
Sharp Increase ◽  
Diffraction Theory ◽  
Mooring System ◽  
Environmental Loads ◽  
Minute Duration ◽  
Axis Offset ◽  
D Wave

Squall is the occurrence of a sudden sharp increase in wind speed, thus amplifies sea environmental loads. In the South of Natuna Sea, squall can reach an intensity of up to 50 m/s or close to 100 knots. In this water, the Belida FSO operates at a water depth of 77.0 m, tethered to the seabed by a spread mooring system. Squall’s impacts on the FSO mooring system has been examined by implementing time-domain simulations accommodated in a numerical model based on the 3-D wave diffraction theory. The simulations were performed by varying the squall duration of escalation, i.e. 2.5, 5.0, and 10.0 minutes, for the load cases of 1-year extreme operational and 100-year extreme survival conditions propagating at 0°, 45°, 90°, 135°, 180°. The three squall durations of escalation substantially increase the significant wave height Hs by averagely 60%, 50% and 34%, respectively. The largest of the maximum mooring tension due to the sea load directions is found to be brought about the 45° load when magnified by the squall with a 2.5-minute duration of escalation. In this respect, the largest intensities of the operational and survival tension loads may reach some 2,027 kN and 3,318 kN, respectively, which are eventually far below the MBL of 7,685 kN. The largest x-axis offsets in operational and survival conditions are 3.94 m and 10.21 m, respectively. Whereas the largest y-axis offsets for operational and survival loads are found to be 13.31 m and 15.48 m. These y-axis offset intensities are larger than the limiting criteria, i.e. 15% of the water depth or 11.55 m.

scholarly journals Design and Automated Optimization of an Internal Turret Mooring System in the Frequency and Time Domain

2021 ◽  
Vol 9 (6) ◽  
pp. 581
Author(s):  
Hongrae Park ◽  
Sungjun Jung
Keyword(s):  
System Design ◽  
Time Domain ◽  
Initial Conditions ◽  
Minimum Weight ◽  
Optimization Algorithms ◽  
Local Optimization ◽  
Mooring System ◽  
Floating Offshore Wind Turbines ◽  
Global And Local Optimization ◽  
Global And Local

A cost-effective mooring system design has been emphasized for traditional offshore industry applications and in the design of floating offshore wind turbines. The industry consensus regarding mooring system design is mainly inhibited by previous project experience. The design of the mooring system also requires a significant number of design cycles. To take aim at these challenges, this paper studies the application of an optimization algorithm to the Floating Production Storage and Offloading (FPSO) mooring system design with an internal turret system at deep-water locations. The goal is to minimize mooring system costs by satisfying constraints, and an objective function is defined as the minimum weight of the mooring system. Anchor loads, a floating body offset and mooring line tensions are defined as constraints. In the process of optimization, the mooring system is analyzed in terms of the frequency domain and time domain, and global and local optimization algorithms are also deployed towards reaching the optimum solution. Three cases are studied with the same initial conditions. The global and local optimization algorithms successfully find a feasible mooring system by reducing the mooring system cost by up to 52%.

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.

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.

An Innovative Synthetic Mooring Solution for an Octagonal FPSO in Shallow Waters

2010 ◽  
Author(s):  
Mo Fan ◽  
Da Li ◽  
Tuanjie Liu ◽  
Alex Ran ◽  
Wei Ye
Keyword(s):  
Oil And Gas ◽  
Shallow Waters ◽  
Manufacturing Processes ◽  
Mooring System ◽  
Oil And Gas Development ◽  
Mooring Lines ◽  
Environmental Loads ◽  
Design And Manufacturing ◽  
Full Production ◽  
Three Bundles

An octagonal FPSO has been proposed for marginal oil and gas development in shallow waters. A shuttle tanker will be deployed near the FPSO during offloading operations. This new concept simplifies the design and manufacturing processes, yet maintains full production, storage, and offloading functions of a conventional ship-shaped FPSO. However, design of the mooring system for this floating unit imposes technical challenges due to: 1) high environmental loads expected on this unit, 2) large dynamic offsets of the unit in shallow waters, and 3) inadequate performance of catenary mooring systems in shallow waters. Thus, development of a viable station keeping solution becomes a key issue to the new concept FPSO design. In this paper, an innovative mooring system is designed to meet the challenges. The FPSO mooring system consists of pile anchors, bridle chains, anchorage buoys, and polyester ropes. Nine mooring lines are grouped into three bundles which evenly spread around the FPSO. The shuttle tanker is attached to the FPSO with a nylon rope hawser at the bow and secured to pre-installed anchorage buoys at the stern with two other nylon ropes. Analyses have been performed for the FPSO mooring system. It is concluded that the proposed mooring system is fully functional and effective.

Lightweight Materials for Mooring Lines of Deepwater Tension Leg Platforms

1984 ◽  
Vol 21 (03) ◽  
pp. 234-241
Author(s):  
Mamdouh M. Salama
Keyword(s):  
Carbon Fiber ◽  
Water Depth ◽  
Hybrid Composites ◽  
Medium Size ◽  
Mooring System ◽  
Basic Design ◽  
High Modulus ◽  
Mooring Lines ◽  
Lightweight Materials ◽  
Design Requirements

The design of a mooring system for tension leg platforms (TLPs) becomes more complicated as water depth increases. The use of steel mooring lines requires complicated tensioning, handling, and flotation systems. This paper discusses the basic design requirements for the TLP mooring system and identifies several advanced fiber-reinforced lightweight materials as alternatives to steel. High-modulus carbon fiber/KevlarcircleR fiber hybrid composites and Kevlar ropes appear to offer the optimum mooring systems for TLPs used in the development of large and medium-size reservoirs, respectively.

Probabilistic Modeling and Analysis of Riser Collision

2002 ◽  
Vol 124 (3) ◽  
pp. 132-138 ◽  
Author(s):  
Bernt J. Leira ◽  
Tore Holma˚s ◽  
Kjell Herfjord
Keyword(s):  
Water Depth ◽  
Deep Water ◽  
Time Domain ◽  
Collision Frequency ◽  
Joint Modeling ◽  
Fatigue Lifetime ◽  
Modeling And Analysis ◽  
Analysis And Design ◽  
Extreme Response ◽  
Probabilistic Context

Analysis and design of deep-water riser arrays requires that both collision frequency and resulting stresses in the pipes are addressed. Within a probabilistic context, the joint modeling of the current magnitude and surface floater motions must be taken into account. The present paper gives an outline of the general analysis setup, and response statistics obtained as a result of time domain simulations are described. Utilization of the analysis is also discussed in relation to estimation of extreme response and fatigue lifetime. As an example of application, a specific Spar buoy riser configuration at a water depth of 900m is considered.

Coupled Analysis of an FPSO and Dry Tree Unit Connected by a Gravity Actuated Pipe (GAP)

2008 ◽  
Author(s):  
Mamoun Naciri ◽  
Helene Schaegis ◽  
Guillaume Ardoise
Keyword(s):  
South China Sea ◽  
Modal Analysis ◽  
South China ◽  
Water Depth ◽  
Time Domain ◽  
Coupled Analysis ◽  
Transfer Lines ◽  
Field Development ◽  
Fluid Transfer ◽  
First Time

MURPHY Sabah Oil Co. Ltd. has developed the Kikeh Field located offshore Malaysia in the South China Sea in a water depth of 1325m. This field development is based on a Floating Production Storage and Offloading unit (FPSO) and a Spar Dry Tree Unit (DTU). Fluids are transported in fluid transfer lines (FTL) using SBM’s newly developed and patented Gravity Actuated Pipe (GAP) system. To our knowledge this is the first time two large moored floaters are connected together by a slender body closing a gap of 1600m. It was not clear at the beginning of the project to what extent the first and second order motions of the two floaters were coupled, if at all, owing to the presence of the GAP system. To investigate the extent of coupling, both frequency domain (modal analysis) and time domain analyses of the FPSO, GAP system and Dry Tree Unit were performed. The salient features and results are presented.

Setpoint Chasing for Thruster-Assisted Position Mooring

2007 ◽  
Author(s):  
Dong T. Nguyen ◽  
Asgeir J. So̸rensen
Keyword(s):  
Force Control ◽  
System Simulation ◽  
Extreme Conditions ◽  
Mooring System ◽  
Integral Control ◽  
Proportional Control ◽  
Environmental Loads ◽  
Damping Control ◽  
Simulation And Experiment ◽  
The Mean

This paper presents a new concept for control of thruster-assisted position moored vessel using setpoint chasing. The mooring system is designed to compensate the mean environmental loads up to a certain limit of the environmental conditions. In the present industrial position mooring (PM) system, the thrusters are used to damp the vessel’s dynamical motions and to provide compensation of any line break. The main contribution in this paper is to extend the damping control used in industrial PM system with improved restoring and mean force control. In order to avoid conflicting control action with the mooring system, the equilibrium position of the uncontrolled vessel will be found using setpoint chasing. The setpoint chasing with proportional control will be developed to prevent a possible resonance situation by shifting the natural frequency of the moored vessel out of the bandwidth of the excitation loads. The setpoint chasing with integral control will improve the ability to prevent line break in extreme conditions by compensating the mean drift loads together with the mooring system. Simulation and experiment will be carried out to verify the advantages of the setpoint chasing strategies.

Research on the Static and Dynamics Characteristics of Soft Yoke Mooring System Based on Multi-Rigid Body Interaction

2020 ◽  
Author(s):  
Hongwei Wang ◽  
Zizhao Zhang ◽  
Gang Ma ◽  
Rongtai Ma ◽  
Jie Yang
Keyword(s):  
Time Domain ◽  
Rigid Bodies ◽  
Coupled Analysis ◽  
Mooring System ◽  
Accurate Analysis ◽  
Restoring Force ◽  
Stiffness Characteristics ◽  
The Time Domain ◽  
Multi Body ◽  
Good Agreement

Abstract Select the common mooring system-soft yoke mooring system as the research object. The soft yoke mooring system is regarded as a structure composed of multiple rigid bodies, and the theoretical analysis of multi-body dynamics is used to discuss the interaction of multi-rigid bodies. The classical HYSY113 FPSO is selected as an example, for the soft yoke mooring system, the stiffness characteristics and static restoring force curved compared with those of software OrcaFlex, and they are in good agreement, which verify the reliability of the formula derived, and it is a prerequisite for the accurate simulations in further steps. Coupled analysis to the whole system in time domain is also carried out both in OrcaFlex and AQWA, and the representative response of the FPSO under different environmental conditions is compared, the results are consistent well with each other. It is a good reference for the future study in this field. Good static characteristics are a prerequisite for accurate analysis of time-domain motion. By comparing the results in the time domain, it is found that under the same working conditions, the analysis results calculated by different commercial software (AQWA and OrcaFlex) may be different. We need to perform design analysis based on the characteristics of the software.

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