Freestanding Hybrid Riser System Bending Moment Management
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Solution Overview
Problem
Current freestanding hybrid riser systems face challenges in deep water installations due to high operational costs, complex design requirements, and limited availability of suitable installation vessels, as well as issues with maintenance and fatigue caused by dynamic movements and external loads.
Innovation Solution
The improved freestanding hybrid riser system features new configurations at the top and bottom interfaces, including a spatial portal structure for the top riser assembly and a flexible element at the base, which reduces static loads and bending moments, and employs the Reel Method for installation, allowing the use of more readily available vessels and reducing maintenance complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional rigid riser designs are used in ultra-deep waters, then structural strength is maintained, but fatigue and buckling occur due to dynamic loads
Solution Approach 1:
The riser system is divided into multiple segments: a rigid riser section connected to a flexible riser section. The rigid section provides structural strength and stability near the platform, while the flexible section absorbs dynamic loads and reduces fatigue in ultra-deep water conditions. This segmentation allows each part to perform its optimal function without compromising the other.
Solution Approach 2:
The hybrid riser system combines rigid and flexible materials/structures to create a composite system that leverages the advantages of both. The rigid portion provides structural integrity and resistance to buckling, while the flexible portion provides fatigue resistance and adaptability to dynamic environmental conditions, resolving the contradiction between strength and reliability.
2Reliability
If flexible risers are used in deep water, then fatigue resistance improves, but strength and installation difficulty worsen
Solution Approach 1:
The system segments the riser into flexible and rigid portions, placing the flexible section where fatigue resistance is critical (in the dynamic environment) and the rigid section where structural strength is paramount (near the platform and wellhead). This spatial segmentation allows the flexible riser to provide fatigue resistance without compromising overall system strength.
3Reliability
If complex design requirements are imposed on freestanding hybrid riser systems, then performance in deep water improves, but operational costs and installation complexity increase
Solution Approach 1:
The rigid riser section serves multiple functions: it provides structural support, maintains system stability, reduces dynamic loads on the flexible section, and facilitates installation using conventional vessels. By making the rigid section multi-functional, the design achieves improved deep water performance without proportionally increasing overall system complexity.
4Reliability
If traditional installation methods are used, then proper installation is achieved, but vessel availability and installation speed are limited
Solution Approach 1:
The rigid riser section is pre-assembled and prepared onshore or on the installation vessel before deployment. This preliminary preparation allows for quality control and reduces the complexity and time required during actual installation operations, enabling faster deployment while maintaining installation quality through standardized procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces static loads and fatigue on the riser components, simplifies maintenance, and lowers operational costs by enabling faster installation with more accessible vessels, enhancing the system's durability and operational efficiency in deep water environments.
Implementation Method 1
a floating tank, the pull from which provides the system with stability
Implementation Method 2
a flexjoint, which attenuates the bending moment transmitted by the lower strengthening joint to the base of the riser or to the rigid jumper
Data Source
AI summary
A freestanding hybrid riser system (FHRS) and a method of installation which makes it possible to use vessels that are more available on the world market. The invention relates to a top riser assembly (TRA) having multiple, offset connection points such that a first bending moment is applied to the TRA by a buoyant unit, and an opposing bending moment is applied to the TRA by a flexible jumper.