Effects of mooring lines and water depth parameters on the dynamic motion of a turret-moored FPSO

2016 ◽  
pp. 15-20
Author(s):  
Montasir Ahmed ◽  
Ashraf Musaad
Keyword(s):  
Water Depth ◽  
Mooring Lines ◽  
Dynamic Motion

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.

scholarly journals Fatigue Life of Mooring Lines on External Turret Floating LNG for Different Pretension and Water Depth

2019 ◽  
Vol 30 (1) ◽  
pp. 19
Author(s):  
Norman Mahdar Sabana ◽  
Eko Budi Djatmiko ◽  
Rudi Walujo Prastianto
Keyword(s):  
Fatigue Life ◽  
Water Depth ◽  
Mooring Lines

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.

Influence of Mooring Lines and Risers on the Trim, Heel and Displacement on FPUs

2015 ◽  
Author(s):  
Cecília Coelho ◽  
Bruna Nabuco
Keyword(s):  
Water Depth ◽  
Mooring System ◽  
Mooring Lines ◽  
Different Types ◽  
Zero Degree ◽  
Displacement Based ◽  
System Configurations ◽  
And Behavior ◽  
Seabed Bathymetry ◽  
Water Depths

By monitoring the variation of weights of floating production units (FPUs), the sum of total weight computed by load calculators on board very often does not match the actual displacement based on the current drafts. Differences can also be observed in the trim and heel of FPUs, which present values different from zero degree in the calculations, but in fact they are frequently kept near zero by ballast control. The mooring lines and risers tensions are one of the most uncertain weight items in loading conditions reported by the crew on board, therefore, this paper aims to assess the influence and behavior of these systems to a variety of situations in which FPUs operate. Analyses were performed for semi-submersibles and FPSOs considering two configurations of mooring system: catenary and taut-leg. The purpose is to evaluate how the magnitude of the resulting force varies — and hence how the trim and heel change — for a range of offsets caused by environmental conditions. The effect of mooring lines and risers is also discussed regarding the water depth by means of case studies considering a range of water depths. Actual lines properties and seabed bathymetry from mooring system models of platforms located offshore Brazil have been taken as reference. In short, the mooring lines and risers loads will be calculated for different types of floating production units, mooring system configurations and water depths in order to evaluate their influence on the trim, heel and displacement of FPUs.

Dropped Polyester Mooring Line Qualification for Reuse

2021 ◽  
Author(s):  
Craig R Gage ◽  
Pierre F Liagre ◽  
Caspar N Heyl ◽  
Cesar Del Vecchio
Keyword(s):  
Gulf Of Mexico ◽  
Water Depth ◽  
Cost Savings ◽  
Mooring Line ◽  
Mooring System ◽  
Potential Cost ◽  
Mooring Lines ◽  
Minimal Damage ◽  
Recovery Effort ◽  
The Impact

The Perdido platform is a spar located in a water depth of 7,825 feet in the Alaminos Canyon Block 857in the Gulf of Mexico. The mooring system consists of nine mooring lines in three groups of three, spacedapproximately 120 degrees apart between each group. Each mooring line is composed of a platform chain,a multi-segment polyester rope including a 120 feet long test insert at the top, a ground chain, a pile chainand other associated connectors. The mooring lines are connected to suction piles. The Minimum BreakStrength for the Perdido polyester mooring line is 4,000 kips. Installation of the spar hull was completed inSeptember 2008 and the topsides was set in March 2009. The spar and its mooring system were originallydesigned for a twenty (20) year life. On May 4, 2019, mooring line # 6 (ML6) was contacted by a marine vessel down line and was severed.Contact occurred along the polyester test insert. A recovery effort was planned, and the mooring line wasreplaced in early June. The original ML6 was recovered from the seafloor on June 4, 2019 as a part of thatcampaign and submitted to an initial inspection. This paper is not intended to go into either the cause of the incident or the replacement of ML6 but willlook to the inspection of the recovered mooring line and explore its suitability for reuse. Initial inspection ofthe lines suggested minimal damage to the polyester rope segments and raised questions to the impacts of 10years of use. Testing was envisioned as a learning opportunity for the impact of service on polyester mooringand was reinforced by the potential cost savings that could be attained though reuse. A methodology wasdeveloped, supported by initial inspections and a suite of testing was performed. The results of these testsare presented in the following, along with a proposed process for assessing and considering reuse of a linefollowing a drop. Additionally, conclusions will be shared for the process, the results, and the potentialramifications for the industry.

A Study on Non-Linear Response of Moored Floating Body Considering Dynamic Motion of Mooring Lines

2013 ◽  
Author(s):  
Keiji Nonaka ◽  
Motohiko Murai ◽  
Atsushi Nagamine
Keyword(s):  
Wind Turbine ◽  
Linear Response ◽  
Floating Body ◽  
Shallow Sea ◽  
Offshore Structure ◽  
Mooring Lines ◽  
Dynamic Motion ◽  
Sea Bottom ◽  
Floating Type ◽  
Sea Area

Recently, the utilization of the ocean space has attracted researcher’s attention which encouraged by the development of resources in seafloor and the offshore structure such as wind turbine. Offshore structure is essential for the utilization of the ocean space. In the case that we install an offshore structure in the shallow sea area, we use simpler structure such as the TLP (Tension Leg Platform) which can reach the sea bottom. However, in recent years the demand for offshore structure in deeper sea area has increased, thus we frequently use more flexible floating type offshore structure with strand chain mooring.

The Design and Installation of Wet Park Configuration for Dynamic Umbilicals in Ultra-Deep Environment

2019 ◽  
Author(s):  
Perdinan Reagan ◽  
Graeme Lovie
Keyword(s):  
Water Depth ◽  
Driving Factor ◽  
Current Direction ◽  
Mooring Lines ◽  
Strong Current ◽  
Close Proximity ◽  
The Stability

Abstract Two dynamic umbilicals in a tethered lazy wave configuration were required to be wet parked in an ultra-deep environment with a water depth in excess of 2900m. The close proximity to the pre-installed mooring lines, along with the in-place configuration requirements (seabed connection location, short seabed tether length, quantity of distribution buoyancy modules) made the design of a viable wet park configuration particularly challenging. Strong current was also a major driving factor. The speed and dominant directionality influences the umbilical hump excursion, the stability of the umbilical and potential interference between the umbilicals and mooring lines. Several different routes were assessed to overcome the key problems as part of the wet park engineering solutions. The installation of these umbilicals into their wet park configurations similarly presents a significant engineering undertaking. An innovative and unconventional solution was chosen for the design of the wet park. The configuration utilises an umbilical ‘cross-over’, which allowed both umbilicals to be laid perpendicular to the dominant current direction and clear of any interference risks. An installation methodology was developed to successfully hook up the tether and lay down the umbilicals. Custom components and installation aids were designed for this purpose.

Polyester Mooring for Ultra-Deepwater Applications

2002 ◽  
Author(s):  
Shankar S. Bhat ◽  
Christian A. Cermelli ◽  
King Him Lo
Keyword(s):  
Water Depth ◽  
Oil And Gas ◽  
Synthetic Fiber ◽  
Mooring Lines ◽  
Deepwater Drilling ◽  
The Past ◽  
Design Methodologies ◽  
Essential Components ◽  
New Material ◽  
Industry Experience

In the past few years, drilling for oil and gas has been conducted in increasingly greater water depth, with recent records approaching 10,000.0 ft water depth. Ultra-deepwater drilling demands increased performance from mooring systems, such as tight watch circle, enhanced reliability, and ease of deployment. Synthetic fiber mooring lines are essential components to help meet these demands. Because of the lack of industry experience with this new material, advanced studies are required to properly design and optimize polyester-based mooring systems for ultra-deepwater drilling. This paper provides information on the performance of polyester mooring lines, based on coupled and un-coupled analyses and compares various design methodologies.

Experimental and Numerical Study on Large Truncation of Deepwater Mooring Line

2009 ◽  
Author(s):  
Yihua Su ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Gang Chen
Keyword(s):  
Dynamic Response ◽  
Water Depth ◽  
Numerical Study ◽  
Unit Length ◽  
Low Frequency ◽  
Model Tests ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Wave Basin

Modeling the deepwater mooring system in present available basin using standard Froude scaling at an acceptable scale presents new challenges. A prospective method is to truncate the full-depth mooring lines and find an equivalent truncated mooring system that can reproduce both static and dynamic response of the full-depth mooring system, but large truncation arise if the water depth where the deepwater platform located is very deep or the available water depth of the basin is shallow. A Cell-Truss Spar operated in 1500m water depth is calibrated in a wave basin with 4m water depth. Large truncation arises even though a small model scale 1:100 is chosen. A series of truncated mooring lines are designed and investigated through numerical simulations, single line model tests and coupled wave basin model tests. It is found that dynamic response of the truncated mooring line can be enlarged by using larger diameter and mass per unit length in air. Although the truncated mooring line with clump presents a “taut” shape, its dynamic characteristics is dominated by the geometry stiffness and it underestimates dynamic response of the full-depth mooring line, even induces high-frequency dynamic response. There are still two obstacles in realizing dynamic similarity for the largely truncated mooring system: lower mean value of the top tension of upstream mooring lines, and smaller low-frequency mooring-induced damping.

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