Float Over Installation Method—Comprehensive Comparison Between Numerical and Model Test Results

2006 ◽  
Vol 128 (3) ◽  
pp. 256-262 ◽  
Author(s):  
Arcandra Tahar ◽  
John Halkyard ◽  
Atle Steen ◽  
Lyle Finn
Keyword(s):  
West Africa ◽  
Gulf Of Mexico ◽  
Model Test ◽  
Test Results ◽  
Sea State ◽  
Numerical Predictions ◽  
Single Piece ◽  
Heavy Lift ◽  
Compliant Tower ◽  
Comprehensive Comparison

Installing a large deck onto a platform, such as a spar, using the floatover method is gaining popularity. This is because the operational cost is much lower than other methods of installation, such as modular lifts or a single piece installation by a heavy lift barge. Deck integration can be performed on land, at quay side and will not depend on a heavy lift barge. A new concept for a floatover vessel has been developed for operations in the Gulf of Mexico and West Africa. In this application sea state conditions are essential factors that must be considered in the Gulf of Mexico, especially for transportation. In West Africa, swell conditions will govern floatover deck (FOD) installation. Based on these two different environmental conditions, Technip Offshore, Inc. developed the FOD installation concept using semi-submersible barge type vessels. A significant amount of development work and model testing has been done on this method in recent years on spar floatover. These tests have validated our numerical methods. Another test was conducted to investigate the feasibility of a deck float-over operation onto a compliant tower for a West Africa project. The project consists of a compliant tower supporting a 25,401metricton(28,000s.ton) integrated deck. This paper will describe comparisons between model test data and numerical predictions of the compliant tower floatover operation.

Float Over Installation Method: Numerical and Model Test Data

2004 ◽  
Author(s):  
Arcandra Tahar ◽  
John Halkyard ◽  
Atle Steen ◽  
Lyle Finn
Keyword(s):  
West Africa ◽  
Gulf Of Mexico ◽  
Test Data ◽  
Model Test ◽  
Sea State ◽  
Numerical Predictions ◽  
Offshore Engineering ◽  
Single Piece ◽  
Heavy Lift ◽  
Compliant Tower

Installing a large deck onto a platform, such as a spar, using the floatover method is gaining popularity. This is because the operational cost is much lower than other methods of installation, such as modular lifts or a single piece installation by a heavy lift barge. Deck integration can be performed on land, at quay side and will not depend on a heavy lift barge. A new concept for a floatover vessel has been developed for operations in the Gulf of Mexico and West Africa. In this application sea state conditions are essential factors that must be considered in the Gulf of Mexico, especially for transportation. In West Africa, swell conditions will govern floatover deck (FOD) installation. Based on these two different environmental conditions, Technip Offshore Engineering developed the FOD installation concept using semi-submersible barge type vessels. A significant amount of development work and model testing has been done on this method in recent years on spar floatover. These tests have validated our numerical methods. Another test was conducted to investigate the feasibility of a deck float-over operation onto a compliant tower for the Benguela Belize (BBT) project. The BBT project consists of a compliant tower supporting a 25,401 metric ton (28,000 s. ton) integrated deck. This paper will describe comparisons between model test data and numerical predictions of the compliant tower floatover operation.

Experimental Study on Hydrodynamics of Hybrid Deep-V Monohull With Different Built-Up Appendages

2018 ◽  
Author(s):  
Shuzheng Sun ◽  
Hui Li ◽  
Muk Chen Ong
Keyword(s):  
Model Test ◽  
Performance Model ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Hydrodynamic Characteristics ◽  
Vertical Acceleration ◽  
Test Results ◽  
Regular Waves ◽  
Sea State ◽  
Seakeeping Performance

The hydrodynamic characteristics of a hybrid deep-V monohull with different built-up appendages are investigated experimentally in order to improve the resistance and seakeeping performance. Model tests have been carried out to study the hydrodynamic performance between a bare deep-V vessel and a deep-V monohull with different built-up appendage configurations (i.e. a hybrid deep-V monohull). From the model test results, it is found that the existence of the appendages will reduce the amplitude of pitching angle and bow vertical acceleration compared to that of the bare deep-V vessel in heading regular waves. However, the resistances for the hybrid deep-V monohull with built-up appendages are increased 15.6% for Fn = 0.264, and 0.1% for Fn = 0.441 compared to the resistance of the bare deep-V vessel. The model test results of seakeeping performance in irregular waves show that the hybrid deep-V monohull gives a better seakeeping performance than the deep-V vessel. The pitching angle and bow vertical acceleration of the hybrid deep-V monohull containing a built-up appendage are reduced 15.3% and 20.6% compared to the deep-V monohull in irregular waves at Fn = 0.441 in 6th class sea state (H1/3 = 6m).

Motion Comparison Between a Conventional Deep Draft Semi-Submersible and a Dry Tree Semi-Submersible

2009 ◽  
Author(s):  
Anis Hussain ◽  
Edwin Nah ◽  
Rain Fu ◽  
Apurva Gupta
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
Significant Influence ◽  
Extreme Environments ◽  
Test Results ◽  
Numerical Computations ◽  
Deep Waters ◽  
Second Tier ◽  
Motion Characteristics ◽  
Heave Motion

One of the major requirements for a floating vessel designed to support top tensioned risers is to have the heave response within a minimum specified range in extreme environments. The heave has a significant influence on the riser stroke. Usually floater designs aim to use conventional riser tensioners, available commercially, which typically have a maximum stroke range in the order of 30 to 35ft. One of the limitations of traditional Semi-submersible designs to support dry trees is that the heave ranges seen in central Gulf of Mexico (GoM) are outside the range that can apply a conventional tensioner. The Extendable Semi-submersible (E-Semi) utilizes a retractable Second Tier Pontoon (STP) to suppress heave motions and reduce its heave motion in order to support top tensioned risers in central GoM ultra deep waters. The design is based on an established deep draft Semi-submersible with the STP attached. This paper presents a comparison between motion characteristics of the deep draft Semi-submersible with and without the STP attached. The comparison is based on numerical computations to predict the responses together with model test results in the same environments. The analysis essentially shows the effectiveness of the STP is suppressing the heave motion.

Model Testing for Vortex Induced Motions of Spar Platforms

2004 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
State Of The Art ◽  
Model Testing ◽  
Model Tests ◽  
The State ◽  
Test Results ◽  
Test Set ◽  
Vortex Induced Vibrations ◽  
Set Up

The state-of-the art in model testing for Vortex Induced Vibrations (VIV) of Spars is presented. Important issues related to Spar VIV model testing are highlighted. The parameters that need to be modeled including hull geometry, strake configuration, mass and mooring properties and, considerations of test set-up and instrumentation are discussed. Results are presented from model tests of an as-built Spar deployed in the Gulf of Mexico. It is shown that the model test results compare well with the VIV responses measured in the field.

The State of Dry-Tree Semi-Submersible Platforms for Deepwater Gulf of Mexico

2014 ◽  
Author(s):  
Ming-Yao Lee ◽  
Jack Zeng ◽  
Philip Poll
Keyword(s):  
Gulf Of Mexico ◽  
Technology Acceptance ◽  
Model Test ◽  
Water Depth ◽  
Technology Development ◽  
Cost Effective ◽  
Test Results ◽  
Scaled Model ◽  
Size Limits ◽  
Long Stroke

The use of semi-submersible platforms has become increasingly popular due to its ability to carry large topsides and the possibility for quayside integration. With recent exploration successes in ultra-deepwater fields of the Gulf of Mexico, major oil and engineering companies are keen to look for a safe, reliable and cost-effective dry-tree option to maximize the value of deepwater field developments. Dry-tree semi-submersible (DTS) emerges as such an option to overcome the water depth and size limits imposed by TLP and Spar, respectively, and enables the platform to carry a large well array and payloads in ultra-deep water. This paper presents the offshore industry’s multi-year efforts to mature two promising semi-submersible platform concepts that can accommodate long-stroke dry-tree risers and have large drilling and production capabilities. Results of technology development and qualification will be highlighted with details on hull performance and hull/riser interfaces. Key structural, mooring and riser analyses and scaled model test results including the long-stroke riser tensioning system will be presented. Remaining challenges that need to be overcome to advance the DTS concepts from “technology acceptance” to “project readiness” will also be discussed.

Horizontal Installation of TLP Tendons

2012 ◽  
Author(s):  
Guang (George) Li ◽  
Robert Kipp ◽  
Steve Leverette
Keyword(s):  
West Africa ◽  
Gulf Of Mexico ◽  
North Sea ◽  
Significant Cost ◽  
Bottom Part ◽  
The North ◽  
The World ◽  
Heavy Lift ◽  
The North Sea ◽  
Foundation Pile

Tension Leg Platforms (TLPs) are ideal supports for dry-tree top tension riser systems because their tendons exhibit high tensile stiffness and significantly reduce the heave, pitch, and roll motions of the platforms. Since the first TLP (Hutton) was installed in the North Sea in 1984, a total of 24 TLPs have been installed throughout the world with 16 of them installed in the Gulf of Mexico. Currently there are new TLP projects proposed in regions off the coast of Malaysia, West Africa, Brazil and Western Australia. Heavy-lift vessels were used to install tendons for most of these TLP’s. Tendon joints were assembled vertically from bottom part to top part. Using a heavy-lift vessel introduces significant cost and schedule challenge to TLP projects, especially ones located in remote regions. A horizontal tendon installation methodology is presented in this paper. This innovative approach involves horizontal assembly of TLP tendon segments on a construction barge. The partially assembled tendon is then incrementally pulled out through a stinger at the barge stern and secured with a hold back clamp so that the next tendon joint can be connected. The process repeats itself until the whole tendon is assembled and deployed. The tendon is then upended to a vertical configuration and connected to a TLP or a foundation pile. In this paper, we examine the alternative equipment and configuration options in the horizontal installation methodology. We outline rationales to select the appropriate options and measures to reduce project cost and risks.

A Truss Semisubmersible Optimized for the Post Katrina Environment in Gulf of Mexico Correlated With Model Test

2009 ◽  
Author(s):  
Chan K. Yang ◽  
John Murray ◽  
Hanseong Lee ◽  
Myoungkeun Choi ◽  
Cheng-Yo Chen ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
Oil And Gas ◽  
Vertical Motion ◽  
Scale Model ◽  
Natural Period ◽  
Steel Catenary Riser ◽  
Numerical Predictions ◽  
Wave Basin ◽  
Global Performance

This paper presents a Truss Semisubmersible (Truss Semi) design optimized to meet the post-Katrina Gulf of Mexico (GoM) environment criteria, with global performance correlated in 1:50 scale model tests in a wave basin. A conventional semisubmersible with a ring pontoon is facilitated with heave plates supported by the truss structure to increase heave natural period. The size of the semisubmersible hull and the configuration of the heave plates are optimized through frequency domain analysis to minimize the vertical motion enough to allow the dry trees to accommodate top tensioned production risers. The system includes eight production top tension risers (TTRs) connected to the production deck and a single drilling riser connected to the drilling deck. All of the TTRs are connected through the hydro-pneumatic tensioner system. One gas export and one oil export steel catenary riser (SCR) export the oil and gas to the storage facility. Structures designed for this deepwater area (4,300 ft) of the central Gulf of Mexico (GoM) must be designed to meet newly proposed environmental criteria [1]. The optimized Truss Semi was tested in the Offshore Technology Research Center (OTRC) model basin, to confirm the global performance, such as motion, air gap and loads on the heave plates. The numerical predictions correlate well with the model test results.

Shallow Water STL Mooring and Riser System

2009 ◽  
Author(s):  
Qinzheng Yang ◽  
Muthu Chezhian ◽  
Geir Olav Hovde
Keyword(s):  
Shallow Water ◽  
Wave Height ◽  
Model Test ◽  
Water Depth ◽  
Significant Wave Height ◽  
Mooring Line ◽  
Test Results ◽  
Sea State ◽  
Significant Wave ◽  
The Impact

A shallow water disconnectable STL turret mooring and riser system has been developed for water depth between 30 and 50 m. This technology is based on APL’s disconnectable STL (Submerged Turret Loading) and STP (Submerged Turret Production) technologies which had been widely applied for water depth between 70 m to 2600 m for FPSOs and LNG offshore terminals. The advantage of disconnectable system is that the mooring and riser system can be designed to a preferred sea state. When the sea state is higher than design sea state (like hurricane), the vessel can be disconnected and sail away. The shallow water STL system consists of STL buoy, mooring lines, riser system and landing pad. The interface with vessel is the same as traditional STL system. The mooring and riser system are connected to the vessel through STL buoy and can be pulled into vessel by using ship winch. Unlike traditional STP and STL buoys, the shallow STL buoy has a net weight and will stay on the landing pad when disconnected from vessel. The landing pad is designed to support the impact load from STL buoy and supply enough friction for the STL buoy to stay in position during 100-year storm. The mooring system design has taken the advantage of directionality of weather when close to the shore by using different mooring line length in different directions. Further an innovative Hold-Back-Wave riser configuration has been developed for shallow water system. The riser configuration has a larger flexibility compared to traditional wave configuration and has proved to be feasible for significant wave height at least 7 m when connected to the vessel and 10+ m when disconnected from the vessel. Model test for the disconnectable shallow water turret mooring and riser system had been performed in MARINTEK, Trondheim with a LNG re-gasification vessel model at 30 m water depth. For connected system, significant wave height Hs = 6 m and 8 m has been tested. The mooring and riser system perform well, as predicted. For disconnected system (when the buoy sitting on the landing pad), significant wave height Hs = 10 m has been tested. The STL buoy is sitting on the landing pad without significant movement and the riser system performs well. SIMO program has been used to calibrate the model test results with numerical simulations. By adjusting surge, sway, yaw damping and 2nd order wave drift force, the calibrated SIMO model agrees well with model test results and can be used for similar development.

Investigation Into Float-Over Installations of Minimal Platforms by Hydrodynamic Model Testing

2005 ◽  
Author(s):  
J. Xia ◽  
S. Hayne ◽  
G. Macfarlane ◽  
D. Field ◽  
Y. Drobyshevski
Keyword(s):  
Model Test ◽  
Load Transfer ◽  
Test Results ◽  
Numerical Predictions ◽  
Wave Basin ◽  
Transfer Operation ◽  
Response Amplitude Operators ◽  
Jack Up ◽  
Standard Software ◽  
Insight Into

The idea of using float-over installations for minimal facilities platforms was shown to offer significant advantages, especially when coupled with a substructure installed by a jack-up rig. Recently, float-over installations of minimal facilities have been conducted by the cantilevered method by ICON Engineering Pty Ltd (ICON). The operation involves the platform topsides being loaded and transported to site on a barge, skidded over the barge bow, and lowered onto the jacket. The paper presents results of a research project undertaken by the Australian Maritime College (AMC) in conjunction with ICON, with the objective to investigate motions of a barge and loads exerted on the jacket when the two are docked together for a smooth load transfer operation. The model of an installation barge has been tested in the AMC wave basin and response amplitude operators of the barge motions have been determined for both the free floating and docked conditions. A range of wave periods and heights has been investigated. Model test results have been used to verify numerical predictions used in the design, and to get insight into uncertainties, which may otherwise be difficult to assess using standard software.

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