Subsea Riser Support Groove for Lazy-Wave Hogbend Installation
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Solution Overview
Problem
The installation of subsea risers, particularly lazy-wave risers, is complex and time-consuming due to the need for assembling and attaching numerous buoyancy modules, which poses safety risks and increases costs, especially in deep water where traditional methods are impractical and require expensive vessels.
Innovation Solution
A method involving a buoyant structure with support elements and buoyancy tanks that can be assembled on the seabed or pre-assembled on a vessel, allowing for the deballasting of ballast water to lift the riser and form a hogbend region, reducing the need for expensive vessels and simplifying the installation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional buoyancy modules are assembled and attached to the riser, then the hogbend is supported and top tension is reduced, but the installation becomes complex and time-consuming with increased safety risks and costs
Solution Approach 1:
The buoyant support structure is divided into multiple buoyant modules that can be independently assembled and attached to the riser at different locations. Each module provides localized buoyancy support to create the hogbend profile, allowing for modular installation that reduces overall complexity while maintaining support stability.
Solution Approach 2:
The buoyant modules are pre-assembled and prepared before being deployed to the riser. This preliminary preparation allows for controlled attachment during installation, reducing on-site complexity and installation time while ensuring proper positioning for stable hogbend support.
2Shape
If numerous buoyancy modules are assembled and attached to form the hogbend, then the riser curvature is maintained, but the installation time increases significantly
Solution Approach 1:
Multiple buoyant modules are combined into integrated buoyant support structures that can be attached as unified units to the riser. This merging approach maintains the required curvature profile while reducing the number of separate assembly operations, thereby decreasing installation time.
Solution Approach 2:
Pre-fabricated buoyant support structures serve as intermediary components between the riser and the buoyancy force. These pre-assembled units simplify the installation process by eliminating the need to attach numerous individual buoyancy elements during the main installation operation.
3Manufacturing precision
If workers assemble buoyancy modules on the pipelaying vessel, then the modules are properly positioned, but safety risks increase due to proximity to the firing line
Solution Approach 1:
The invention employs pre-assembled buoyant support structures that can be deployed as complete units rather than requiring workers to assemble individual modules on the vessel. This approach prioritizes worker safety by eliminating on-vessel assembly operations near the firing line, while positioning accuracy is maintained through pre-fabrication quality control.
4Length of stationary object
If deep water installation is performed with traditional methods, then the riser can be installed, but expensive vessels are required
Solution Approach 1:
The installation system is segmented into modular buoyant support units that can be deployed from less expensive vessels. This segmentation allows deep water installation capability without requiring the most expensive heavy-lift vessels, as the modular approach can be handled by standard pipelaying vessels equipped with basic lifting capacity.
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 method allows for the efficient installation of subsea risers with reduced operational costs and safety risks, enabling the use of lower-cost vessels and eliminating the need for deadweight, while maintaining the stability and curvature of the riser.
Implementation Method 1
forming a hogbend region of the riser by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed
Data Source
Figure 1a~1c
Figure 1d~1f
Figure 2~3
AI summary
A method of installing a subsea riser comprises placing an elongate negatively-buoyant support on the seabed and, when laying the riser on the seabed, guiding a riser portion onto the support to extend along and be cradled by the support. A hogbend region of 5 the riser is then formed by conferring positive buoyancy on the support to lift the support and the riser portion away from the seabed. An element of the support comprises a riser support disposed in a longitudinally-extending open-ended gap between buoyancy volumes disposed on opposite sides of 0 the gap. Coupling formations such as hinge portions can couple the element to a like element. When so coupled, the gaps of those elements align to define an upwardly-opening, longitudinally-extending groove to receive the riser.