Subsea Workover Riser Compensator for Marine Tension Control
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Solution Overview
Problem
Conventional compensator systems for workover risers in marine environments are prone to failure due to vessel oscillations, leading to potential tensile or compressive failure, and existing weak link systems do not prevent the release of contents, posing safety and environmental risks.
Innovation Solution
A tensioning apparatus that applies constant tension to the workover riser within the marine riser, a length variation apparatus to maintain the upper end of the riser at a fixed deck location, and a latch to separate the riser from the BOP system in case of over-tensioning, ensuring containment of contents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional compensator system is mounted high above the deck to maintain constant tension on the workover riser, then the tension control function is improved, but the risk of man-riding hazards and operator exposure to falling dangers increases
Solution Approach 1:
The patent extracts the compensator system from the vessel deck and relocates it to the seabed, separating the tension control function from the vessel structure. This eliminates the need for high mounting positions and associated man-riding hazards while maintaining constant tension control on the workover riser.
Solution Approach 2:
The patent introduces a seabed-mounted compensator system as an intermediary between the workover riser and the vessel, using the seabed as a stable reference point instead of the oscillating vessel deck. This mediator provides stable tension control without requiring operators to be positioned high above the deck.
2Reliability
If the workover riser is allowed to separate from the BOP system in case of failure, then the risk of equipment damage is reduced, but the risk of contents release and environmental damage increases
Solution Approach 1:
The patent implements a weak link system that预先 (in advance) separates the workover riser from the BOP system upon detecting excessive tension. This preliminary separation action prevents equipment damage while the retainer valve simultaneously closes to contain contents, addressing both protection and environmental concerns.
Solution Approach 2:
The patent segments the riser system into separable sections with a controlled weak link point. This segmentation allows the workover riser to disconnect from the BOP system in failure scenarios, protecting expensive equipment while the retainer valve containment system prevents environmental damage from contents release.
3Reliability
If the upper end of the workover riser is maintained at a fixed height above the vessel deck to prevent over-tensioning, then the risk of tensile failure is reduced, but the complexity of the compensation system increases
Solution Approach 1:
The patent inverts the conventional approach by instead of maintaining a fixed height above the deck, allowing the riser to have sufficient initial length and using a seabed-mounted compensator to absorb vertical movements. This inversion simplifies the system by eliminating complex height control mechanisms while maintaining tensile failure prevention.
Data Source
AI summary
A tensioning apparatus for applying a substantially constant tension to a workover riser (12) includes a first portion (40) adapted to be coupled to a workover riser, a second portion (44) adapted to be coupled to a marine riser (14) and tensioning means (46) for providing relative movement between the first portion and the second portion to, in use, tension the workover riser.