The fast growing offshore industry has come up with advanced technology that makes it possible to produce oil and gas on deeper offshore sites. One of the interests now is to look for a structure and systems that are reliable and cost effective for ultra deep water operation. Tension leg platform (TLP) concept is currently been viewed for this ultra deepwater operation. TLP differ from other type of floating platform in a sense that the hull buoyancy exceed its weight, the hull is vertically moored at a draft below the displacement thus creating constant tension in the mooring line. The problem for the development of TLP beyond 1500 meters water depth is the material for the tendon. Conventional tendon made by steel is too heavy and proven to be unpractical in ultra deep water. New material is needed, that is lightweight and stiffer, and this material needs to meet the structural performance characteristic for practical development. This research is intended to demonstrate the performance of reduced weight tendons in ultra-deep water. The effect of weight reduction on motion response of the TLPs in regular and irregular waves and the performance differences between conventional tendons and reduced weight tendons in term of motion response also will be investigated. Based on the review it is known and widely accepted that numerical analysis is the most practical and economical way to analyze the structure, but because of the simplification and assumption of the numerical calculation a validation is needed. The numerical analysis will be done using industrial accepted software, ANSYS AQWA. For the purpose of validation, model test is proposed to be done in the test basin, but due to very limited water depth in the test basin, truncation method will be used instead of common traditional test. This method also known as hybrid method that uses numerical calculation to predict the cut off portion of the tether lines and using physical model test in the upper portion.
Table of Contents
1.1 Introduction
1.2 Environmental loads
1.3 TLP tether system
1.4 TLP tendon material
1.5 Analytical method and approach
1.6 Motion response of tension leg platform
1.7 Model test with truncation method
1.8 Review of guideline, regulation and standard
1.9 Conclusion
Objectives and Topics
This work aims to evaluate the performance of reduced-weight tendons for Tension Leg Platforms (TLPs) operating in ultra-deep water environments, addressing the limitations of conventional steel tendons. The research investigates motion responses under regular and irregular waves and explores numerical analysis as a practical method, validated by truncated model testing, to ensure structural reliability and cost-effectiveness in deep-sea oil and gas production.
- Weight reduction techniques for TLP tendon systems.
- Numerical analysis and modeling of hydrodynamic loads in ultra-deep water.
- Dynamic response and motion behavior of TLPs under environmental stress.
- Validation of truncation methods for scale-model testing in basins.
- Review of industry standards and design criteria for compliant offshore structures.
Excerpt from the Book
1.4 TLP tendon material
The material aspect of the tendon is one of the big concerns in the development of TLP. Going deeper than 1000 meters made steel tendons unpractical, this is because of the fact that the weight is excessively high. Steel tendons also have a serious issue with elasticity that causes a resonance problem. Other factor that excludes the use of steel tendon in deep water is the cost effective issue. All these pushed the development of a new lightweight tendon.
One of the early notable and important studies on TLP tendon is made by Hanna et al. (1989), where they account the effect of several parameters including tension, weight, material and hydrostatic pressure on the TLP tendons. Lightweight materials are proposed to reduce tendon top tension, which have a lower tendon weight in air. Steel tendons can be used in deep water by increasing the ratio between diameter and wall thickness (D/t), but due to hydrostatic collapse in deep water, D/t ratio for steel tendons allowable only up to 15. For this reason new lightweight material are needed for deep water purpose, and their performance need to be clarify.
The performance of composite tendon compared to conventional steel tendon is studied by Wu (1999). This comparison shown some several superiority of composite tendon compared to traditional steel tendon, these includes significant reduction of horizontal offset, reduce pretension and maximum dynamic tension. The results of the TLP motion at center gravity are given in Table 3.
Summary of Chapters
1.1 Introduction: Provides an overview of TLP technology, the historical development of compliant offshore structures, and the scope of the literature review regarding environmental loads and model testing.
1.2 Environmental loads: Discusses the fundamental forces—wind, waves, tide, and current—acting on offshore structures and reviews studies on dynamic behavior and computational methods like BEM.
1.3 TLP tether system: Focuses on the structural integrity, fatigue, and reliability of tendons, highlighting maintenance challenges and the need for improved material performance in deep water.
1.4 TLP tendon material: Examines the limitations of conventional steel tendons and the potential of lightweight composite materials to overcome resonance and cost issues in ultra-deep water.
1.5 Analytical method and approach: Reviews various numerical approaches and computational tools used to predict TLP behavior, establishing the importance of these methods for safe design.
1.6 Motion response of tension leg platform: Discusses stochastic responses, including springing and slow-drift, and the influence of geometry on the platform's overall dynamic behavior.
1.7 Model test with truncation method: Explores the challenges of basin depth and introduces hybrid model testing and truncation methods as essential tools for accurate validation.
1.8 Review of guideline, regulation and standard: Summarizes the influence of international standards and classification society rules on the design and structural reliability of TLP systems.
1.9 Conclusion: Synthesizes the literature findings, reinforcing the necessity for weight-reduced tendons and hybrid validation methods to support future ultra-deep water exploration.
Keywords
Tension Leg Platform, TLP, Ultra-deep water, Tendon, Tether system, Offshore industry, Hydrodynamic loads, Numerical analysis, Model test, Truncation method, Structural reliability, Fatigue, Composite material, Motion response, Offshore design standards.
Frequently Asked Questions
What is the primary focus of this research paper?
The paper is a comprehensive literature review focused on the performance of reduced-weight tendons for Tension Leg Platforms (TLPs) specifically designed for ultra-deep water operations.
What are the central thematic fields covered in the text?
The text covers TLP structural design, environmental load analysis, tether/tendon material science (steel vs. composites), numerical modeling approaches, and experimental validation through model testing.
What is the primary objective or research question?
The main objective is to demonstrate the performance benefits of lightweight tendons in ultra-deep water and identify reliable methods for analyzing and validating TLP motion responses.
Which scientific methods are analyzed for TLP evaluation?
The work reviews numerical analysis methods, computational fluid dynamics (CFD), frequency and time domain simulations, and experimental basin testing using truncation (hybrid) methods.
What is covered in the main section of the document?
The main body examines the environmental impact on TLP motion, the mechanical integrity of tether systems, material comparisons between steel and composites, and the standardization of global performance analysis.
Which keywords best characterize the work?
Key terms include Tension Leg Platform (TLP), ultra-deep water, tendon, composite materials, hydrodynamic loads, and truncation methodology.
Why is the "truncation method" considered vital for this research?
Due to the limited water depth in test basins compared to the actual depth of ultra-deep water sites, truncation methods allow researchers to accurately simulate tether dynamics and scale models without requiring impractically deep basins.
How does the document address the limitations of conventional steel tendons?
It highlights that steel tendons are too heavy and prone to resonance at depths exceeding 1000 meters, proposing that lightweight, stiffer composite materials can improve structural efficiency and reduce costs.
- Quote paper
- Syed Ahmad Fathi Syed Mohd Khair (Author), 2014, Literature Review On The Performance of Reduced Weight Tendon TLP in Ultradeep Water, Munich, GRIN Verlag, https://www.grin.com/document/375396
