Improving the Motions of a Semi by the Addition of Heave Plates

2008 ◽  
Author(s):  
Cheng-Yo Chen ◽  
Yun Ding ◽  
Trevor Mills ◽  
John Murray
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
Cost Effective ◽  
Analytical Prediction ◽  
Test Results ◽  
Effective Manner ◽  
Truss Spar ◽  
Heave Plate ◽  
Motion Characteristics ◽  
Plate System

Similar to the manner in which heave plates provide a Truss Spar with low global motions, a heave plate system can be used to significantly mitigate the motions of a conventional semi-submersible. This paper will focus on the global performance of a conventional semi-submersible that has been properly configured with heave plates. The design case is a Gulf of Mexico deepwater environment similar to that for a Spar located in 5,600 feet of water. The system has eight top-tensioned risers (TTR) supported on the top of the semi hull with tensioners, a spread mooring and a 10,000-ton operating payload. Extensive global motion analyses and comprehensive model testing have been carried out to validate the in-place behavior of such a solution. This paper presents the validation results from the analytical prediction and the model test. A semi-submersible with properly configured heave plates can be used as a viable deepwater dry-tree floating solution in such harsh environments as in the Gulf of Mexico. Because of its superior motion characteristics, this solution is also more SCR friendly and can be a better wet-tree application as compared to conventional semi-submersibles. The analytical and model test results demonstrate that the excitation of a semi-submersible hull by wind, wave and current can be adequately mitigated by the proper placement and sizing of a heave plate system. The analysis and testing also indicates that to achieve suitable motions in a cost effective manner requires incorporating fabrication and installation issues into the heave plate system. The in-place behavior of this solution has been validated and thus proving the concept provides a viable cost effective dry-tree floating solution for deepwater developments.

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.

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.

Numerical Prediction of Spar Motions Considering Top Tension Riser Stiffness

2004 ◽  
Author(s):  
Cheng-Yo Chen ◽  
Prahoro Nurtjahyo
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
Pitch Angle ◽  
Motion Prediction ◽  
Test Results ◽  
Proposed Model ◽  
Comparison Results ◽  
Truss Spar ◽  
Righting Moment ◽  
Delta Model

Spar motions are often predicted without explicitly considering the stiffness effect of the buoyancy can of top tension risers (TTRs). This may result from the inability of most motion prediction programs to take this effect into consideration. The forces exerted by the TTR buoyancy can on the spar provide a net beneficial righting moment. Hence, neglecting the effect of TTR stiffness could produce excessive predicted spar motions, particularly maximum pitch angle. The derived spar configurations based on such predicted motions are likely to be conservative and not optimal. This paper proposes a simple “Linearized P-Delta” model to account for the effect of TTR stiffness on spar motions. The predicted motions using the proposed model are compared with the model test results for a production truss spar in the Gulf of Mexico. The comparison results indicate that the proposed model is quite rigorous and correlates reasonably well with the model test results.

Improved Strake Design for Vortex Induced Motions of Spar Platforms

2005 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Test Program ◽  
Test Set ◽  
Test Methodology ◽  
Spar Platforms ◽  
Truss Spar ◽  
Set Up

An extensive model test program was conducted to explore the effectiveness of alternate strake designs to reduce Truss Spar VIV response. Different strake configurations were tested to minimize VIV response. The paper presents results of the model tests. The model test set-up is described, important parameters that are modeled (including hull and truss geometry, strake configuration, mass and mooring properties) and considerations of instrumentation and test methodology are discussed. The paper also describes the analysis of the test results and shows the effectiveness of new strake design. The present results are compared with VIV response of existing Truss Spars with conventional strake design.

Generalized Kinematic Modeling of Reconfigurable Machine Tools

1998 ◽  
Vol 124 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Yong-Mo Moon ◽  
Sridhar Kota
Keyword(s):  
Machine Tools ◽  
Screw Theory ◽  
Cost Effective ◽  
Mathematical Representation ◽  
Kinematic Modeling ◽  
Effective Manner ◽  
Systematic Selection ◽  
Motion Characteristics ◽  
Set Up ◽  
Representation Scheme

To accommodate frequent changes in product design and to be able to process a family of products in a timely and cost-effective manner, the next generation of machine tools should be reconfigurable. Reconfigurability enables reduction not only in machine design lead time but more significantly a reduction in machine set-up and ramp-up time. The essential characteristics of Reconfigurable Machine Tools (RMTs) include modularity, convertibility, flexibility, and cost-effectiveness. This paper presents a mathematical representation scheme using screw theory that lays the foundation for systematic design of reconfigurable machine tools. The motion characteristics of a set of desired machining tasks as well as stored library of machine modules are captured in a common representation scheme. A simple design example to illustrate the application of this methodology for systematic selection and synthesis of reconfigurable machine tools is presented.

The Effect of Mooring System and Sheared Currents on Vortex Induced Motions of Truss Spars

2003 ◽  
Author(s):  
Radboud R. T. van Dijk ◽  
Arjan Voogt ◽  
Paul Fourchy ◽  
Saadat Mirza
Keyword(s):  
Gulf Of Mexico ◽  
Mooring System ◽  
Test Results ◽  
Current Profile ◽  
Scaled Model ◽  
Production Platform ◽  
Helical Strakes ◽  
Truss Spar ◽  
Set Up ◽  
Program Show

Since 1996 Spars have been used as production platform in the Gulf of Mexico. Spar Vortex Induced Motions (VIM) in strong currents like the hurricane and loop currents are an important consideration for the design of the mooring system and risers. This is important for the extreme offsets as well as fatigue in risers and the mooring system. This paper compares the VIM behavior of a truss Spar in sheared currents, like the Hurricane current in the Gulf of Mexico, with tow test results. Experiments have been carried out on a scaled model in both a complete mooring system and in a towing set-up with a simplified horizontal mooring. The Spar model consists of a hard tank with removable helical strakes, a truss section and a square soft tank. The results of this model test program show that both the choice of the mooring system and current profile have a significant influence on the VIM response of the Spar. The paper discusses the results of this research and also addresses important issues and considerations for VIM model tests.

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.

Hepatology

2012 ◽  
Author(s):  
John J. Poterucha
Keyword(s):  
Liver Disease ◽  
Cost Effective ◽  
Biliary Cirrhosis ◽  
Test Results ◽  
Liver Test ◽  
Effective Manner ◽  
Chief Complaints ◽  
History Of ◽  
Abnormal Liver Test ◽  
Cholestatic Diseases

The evaluation of patients who have abnormal liver test results includes many clinical factors: the chief complaints of the patient, patient age, risk factors for liver disease, personal or family history of liver disease, medications, and physical examination findings. Because of these many factors, designing a standard algorithm for the evaluation of abnormal liver test results is difficult and often inefficient. Nevertheless, with basic information, abnormalities can be evaluated in an efficient, cost-effective manner. Diseases that predominantly affect the biliary system are called cholestatic diseases. They can affect the microscopic ducts (eg, primary biliary cirrhosis) or the large bile ducts (eg, pancreatic cancer causing obstruction of the common bile duct), or both (eg, primary sclerosing cholangitis).

scholarly journals A Single-Well Gas-Assisted Gravity Drainage Enhanced Oil Recovery Process for U.S. Deepwater Gulf of Mexico Operations

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1743
Author(s):  
Bikash D. Saikia ◽  
Dandina N. Rao
Keyword(s):  
Gulf Of Mexico ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Scale Up ◽  
Cost Effective ◽  
Recovery Process ◽  
Recovery Factor ◽  
Gravity Drainage ◽  
Effective Manner ◽  
Single Well

The U.S. Deepwater Gulf of Mexico (DGOM) area that has some of the most prolific oil reservoirs is still awaiting the development of a viable enhanced oil recovery (EOR) process. Without it, DGOM will remain severely untapped. Exorbitant well costs, in excess of $200 million, preclude having extensive injection patterns, commonly used in EOR design frameworks. Aside from injection patterns, even operationally waterflooding has met with significant challenges because of injectivity issues in these over pressurized turbidities. The gas-assisted gravity drainage (GAGD) EOR process, that holds promise for deepwater environments because of lesser injectivity issues, among others, has been adapted in this work to overcome these limitations. A novel design in the form of a single well—gas assisted gravity drainage (SW-GAGD) process, has been demonstrated to emulate the benefits of a GAGD process in a cost-effective manner. Unlike conventional GAGD processes, which need multiple injectors and separate horizontal production wells, the SW-GAGD process just uses a single well for injection and well production. The performance of the process has been established using partially scaled visual glass models based on dimensional analyses for scale up of the process. The recovery factor has been shown to be in the range of 65–80% in the immiscible mode alone, and the process is orders of magnitude faster than natural gravity drainage. A toe-to-heel configuration of the SW-GAGD process has also been tested and for the configuration to be immune from reservoir layering, the toe of the well should ideally end at the top of the payzone. Better sweep of the payzone and consequent high recovery factor of 80% OOIP was observed, if the heel part of the bottom lateral is located in a lower permeability zone.

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.

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