Subsea Riser Anchoring with Bend Controllers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flexible subsea risers in the oil and gas industry face challenges with excessive bending and fatigue in the sag bend section due to dynamic loads from waves and tides, as existing anchoring systems either fail to resist these forces effectively or are impractical for shallow water installations.
Innovation Solution
A subsea flexible riser installation system featuring a seabed foundation with an upright rigid locating structure and a clamp that engages with a locating formation on the riser, using a pulling system to lock the riser in place and incorporate bend controllers to restrict curvature and manage bending moments, allowing the riser to follow a predetermined path and resist fatigue-promoting movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a free-hanging catenary configuration is used, then the riser can be installed without intermediate support, but the sag bend section experiences excessive bending and fatigue damage
Solution Approach 1:
The patent applies preliminary action by pre-positioning the riser in a controlled configuration during installation using a guided reel system. The riser is paid out from a reel through a guide mechanism that ensures proper positioning and minimizes bending stresses before the riser is left to hang freely, thus preventing fatigue damage while maintaining installation simplicity
Solution Approach 2:
The patent introduces an intermediary guided reel system that acts as a mediator between the riser and the sea floor. This intermediary device controls the riser's path during installation, ensuring it follows a predetermined trajectory that avoids excessive bending in the sag bend section, thereby protecting the riser while maintaining ease of installation
2Reliability
If intermediate buoyant support is provided, then the sag bend section is isolated from dynamic movement, but the riser assumes an undulating shape and requires complex anchoring
Solution Approach 1:
The patent extracts the buoyant support element from the system, eliminating the need for intermediate buoyancy modules. Instead, the riser is allowed to hang freely in a catenary configuration, but with a simplified anchoring system that uses a single anchor point and a guided reel during installation, thus reducing complexity while maintaining fatigue protection through proper initial positioning
Solution Approach 2:
The patent applies preliminary action by pre-positioning the riser correctly during installation using the guided reel mechanism. This preliminary positioning ensures the riser starts in an optimal configuration that minimizes dynamic movement in the sag bend section, eliminating the need for complex intermediate support structures
3Length of moving object
If a shallow water anchoring system is used, then the riser can be anchored close to the surface, but existing systems are impractical or fail to resist wave and tide forces effectively
Solution Approach 1:
The patent applies dynamics by designing an anchoring system that allows controlled movement rather than rigid fixation. The guided reel mechanism and flexible riser configuration enable the system to dynamically respond to wave and tide forces, absorbing energy through controlled motion while maintaining effective anchoring in shallow water conditions
Solution Approach 2:
The patent changes the parameters of the anchoring system by using a movable guided reel mechanism during installation that can be positioned at optimal locations. This allows the system to adapt to shallow water conditions by adjusting the anchoring geometry and riser configuration to maximize resistance to wave and tide forces while maintaining practical feasibility
Data Source
AI summary
A subsea flexible riser installation has a seabed foundation and a steep-configuration flexible riser anchored to the seabed by the foundation. An attachment formation is fixed relative to the riser and a locating formation is fixed relative to the foundation, both at positions elevated above the seabed. The locating formation is engaged with the attachment formation on the riser. This holds the attachment formation and the riser against movement when engaged, protecting the base of the riser from over-bending and fatigue.