Failsafe Subsurface Safety Valve Nitrogen Leakage
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Solution Overview
Problem
Deepwater subsurface safety valves (SSVs) with nitrogen chambers are prone to leakage, requiring costly interventions involving semi-submersible drilling vessels, as they fail to close properly when nitrogen leaks, necessitating the removal and replacement of the entire production tubing string, which is expensive and inefficient.
Innovation Solution
A failsafe subsurface-controlled safety valve design featuring a tubular housing with a flapper and operating piston mechanism, where the flow tube interacts with a trigger valve and spring system to automatically close the valve in case of nitrogen leakage or pressure loss, allowing for remote deployment and operation without the need for a riser, utilizing a ROV and support vessel for installation and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a nitrogen chamber is used in the SSV to maintain valve closure, then the valve can remain closed during normal operation, but the nitrogen may leak over time causing the valve to fail to close properly
Solution Approach 1:
The patent incorporates a backup spring mechanism that is pre-loaded and ready to actuate the valve closed position if nitrogen pressure is lost. This backup system provides beforehand cushioning against the potential failure mode of nitrogen leakage, ensuring the valve can still close reliably even when the primary nitrogen charging system fails.
Solution Approach 2:
The spring mechanism is designed to automatically actuate the valve to the closed position when nitrogen pressure is lost, without requiring external intervention. The loss of nitrogen pressure itself triggers the spring to push the valve closed, making the system self-service in responding to the failure condition.
2Reliability
If the entire production tubing string is removed and replaced when the SSV fails, then the valve can be replaced, but the intervention cost becomes extremely high involving semi-submersible drilling vessels
Solution Approach 1:
The patent divides the SSV into separable components, allowing the valve assembly to be independently replaced without removing the entire production tubing string. The valve can be accessed, removed, and replaced through the tree structure, segmenting the replacement operation from the costly full tubing string intervention.
Solution Approach 2:
The failed valve can be extracted and removed from the production tubing string through the tree connection points, allowing replacement of only the valve component rather than the entire tubing string. This extraction principle enables selective replacement of the faulty component while leaving the rest of the system in place.
3Reliability
If a complex intervention operation with multiple vessels is used to replace a failed SSV, then the valve can be replaced, but the time required for the operation becomes very long
Solution Approach 1:
By segmenting the valve replacement operation from the full tubing string intervention, the patent enables a simplified procedure where only the valve assembly needs to be accessed and replaced through the tree structure. This segmentation dramatically reduces the time required compared to complete tubing string removal and replacement.
Solution Approach 2:
The tree is pre-configured with connection points and access mechanisms that allow the valve to be reached and replaced without complex intervention operations. The preliminary setup of the tree structure with proper connection interfaces enables rapid valve replacement when failure occurs.
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
Enables cost-effective and efficient remediation of failed SSVs by allowing the valve to automatically close and be replaced without the need for extensive vessel intervention, reducing operational costs and improving maintenance efficiency in deepwater environments.
Implementation Method 1
a flow tube movable within the bore of the housing between an upper position in which the flapper is engaged with the seat to close the valve and a lower position in which the flapper is disengaged from the seat to open the valve, the flow tube having been displaced from the upper position to the lower position by the production fluid pressure
Data Source
Figure 1A
Figure 1B~1C
Figure 2A
AI summary
Embodiments of the invention generally relate to a failsafe subsurface controlled safety valve. In one embodiment, a failsafe subsurface controlled safety valve assembly (40) includes: a tubular housing (41); a closure member (43) disposed in the tubular housing, wherein the closure member is movable between a closed position and an open position; an operating piston (45) operable to move the closure member between the closed position and the open position; and a trigger piston (46) operable to move the closure member from the open position to the closed position.