Riser Assembly Ballast Module Sag Bend Stability
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Solution Overview
Problem
Existing riser assemblies in the oil and gas industry face issues with unwanted movement due to changes in weight, such as marine growth, affecting buoyancy and tension relief, leading to potential riser diversion or collision with structures, especially in shallow water applications.
Innovation Solution
A riser assembly design incorporating a weight element, such as a ballast module, positioned in the sag bend portion to offset initial buoyancy, and a tethering element to maintain a predetermined distance from the water surface, allowing automatic adjustment to changes in weight and buoyancy, ensuring stable configuration and clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If buoyancy modules are added to support the riser's middle section, then installation cost and installation time are reduced, but the riser assembly becomes sensitive to weight changes causing unwanted movement and configuration diversion
Solution Approach 1:
The patent introduces a ballast module as a weight element that provides a downward force to counterbalance the upward buoyancy force from the buoyancy module. This counterweight mechanism stabilizes the riser assembly by preventing unwanted upward movement and configuration diversion while maintaining the buoyancy support benefits for reduced installation cost and time.
Solution Approach 2:
The patent adjusts the net buoyancy parameter by combining buoyancy modules and ballast modules to achieve a controlled net positive buoyancy. This parameter adjustment allows the riser assembly to maintain stable configuration while still benefiting from reduced installation cost and time compared to alternative configurations.
2Strength
If buoyancy modules are used to counteract riser weight, then tension relief on the flexible pipe is improved, but changes in riser weight due to marine growth cause unwanted movement and reduce lifetime
Solution Approach 1:
The ballast module provides a constant downward counterweight force that balances the buoyancy module's upward force. This stabilization mechanism reduces the sensitivity of the riser assembly to weight changes from marine growth, maintaining consistent tension relief on the flexible pipe throughout the riser's operational lifetime.
Solution Approach 2:
The patent anticipates future weight changes due to marine growth by pre-configuring the ballast module to counterbalance buoyancy forces. This beforehand cushioning approach ensures that the riser assembly remains stable and maintains proper tension relief even as the riser accumulates marine growth over time, thereby extending its operational lifetime.
3Ease of operation
If the riser assembly operates in shallow water, then access and installation are easier, but weight changes cause pronounced height changes leading to collision with structures
Solution Approach 1:
The ballast module provides a stabilizing counterweight force that compensates for buoyancy changes and weight variations. In shallow water applications, this counterweight mechanism prevents pronounced height changes that would otherwise occur with simple buoyancy support, thereby reducing the risk of collision with surface structures while maintaining installation ease.
Solution Approach 2:
The patent controls the net buoyancy parameter to achieve a balanced configuration suitable for shallow water operations. By carefully adjusting the combination of buoyancy and ballast modules, the system maintains stable height and position in shallow water, preventing collision risks while preserving the ease of installation that shallow water provides.
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
The design reduces sensitivity to weight changes, maintains stable configuration, and ensures minimum clearance distances, preventing riser diversion or collision, while allowing for quick and cost-effective installation.
Implementation Method 1
at least one buoyancy element for enabling a portion of the riser to form a hog bend configuration and an adjacent portion of the riser to form a sag bend configuration
Implementation Method 2
a weight element provided between the first end of the riser and the at least one buoyancy element, such that in an initial deployment position, the weight element is provided at least partially in the sag bend portion of the riser
Data Source
AI summary
A riser assembly and method of producing a riser assembly for transporting fluids from a sub-sea location is disclosed. The assembly includes a riser comprising at least one segment of flexible pipe, the riser having a first end for connection to a floating facility and a further end; at least one buoyancy element for enabling a portion of the riser to form a hog bend configuration and an adjacent portion of the riser to form a sag bend configuration; and a weight element provided between the first end of the riser and the at least one buoyancy element, such that in an initial deployment position, the weight element is provided at least partially in the sag bend portion of the riser.