Annulus Balanced Subsurface Safety Valve Control System
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Solution Overview
Problem
Existing subsurface safety valves require substantial pressure and time to close due to the need for a large biasing force, which is inefficient and unreliable, especially when the valve is set deep in a well, as they depend on a minimum pressure differential that may not always be present.
Innovation Solution
A system that alternately connects the piston chamber of the safety valve to well pressure or a pressurized fluid source using a valve controller, allowing the valve to open with pressure greater than the annulus pressure and close by balancing pressure across the piston with well pressure, reducing the biasing force and closing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large biasing force is applied to close the valve, then the valve can be closed reliably, but substantial pressure must be applied to open the valve and the closing time increases
Solution Approach 1:
The piston chamber is divided into two separate chambers that can be independently pressurized. This segmentation allows the biasing force to be applied locally to one chamber while the other chamber provides counter-pressure, eliminating the need for a large overall biasing force while maintaining reliable valve closure.
Solution Approach 2:
Both piston chambers are exposed to well pressure, creating equipotential conditions that balance the pressures acting on the piston. This eliminates the need for substantial pressure differentials to open the valve, as the well pressure itself provides the balancing force.
2Length of moving object
If the valve is set very deep in a well, then it can protect deeper formations, but the fluid column in the control line must be lifted by the biasing device requiring substantial pressure
Solution Approach 1:
The well pressure itself is utilized to balance the piston chambers, eliminating the need for the biasing device to lift the fluid column. The system uses the existing well pressure to perform the work that would otherwise require substantial additional pressure, allowing the valve to be set at greater depths without increasing control line pressure requirements.
3Force
If substantial pressure is applied to the control line to open the valve, then the valve can be opened against the biasing force, but a corresponding substantial pressure differential must be applied across the piston
Solution Approach 1:
By segmenting the piston chamber into two independently controllable chambers, the system can apply biasing force to one chamber while maintaining counter-pressure in the other chamber. This segmentation allows valve opening with reduced pressure differential, as the well pressure balances the forces rather than requiring a large external pressure differential.
4Reliability
If the biasing device exerts large biasing force to close the valve, then the valve can be closed reliably, but flowing fluid through the long control line takes substantial time
Solution Approach 1:
By exposing both piston chambers to well pressure, the system creates equipotential conditions that balance the pressures acting on the piston. This eliminates the need for large pressure differentials and reduces the time required to flow fluid through the control line, enabling rapid valve closure while maintaining reliability.
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 solution reduces the pressure needed to open the valve, allows for rapid closure regardless of annulus pressure levels, and ensures reliable operation by balancing piston pressure, eliminating dependence on minimum annulus pressure.
Implementation Method 1
A piston of the safety valve which displaces in response to a pressure differential between chambers exposed to the piston
Implementation Method 2
A valve controller alternately exposes at least one of the chambers to pressure in an annulus surrounding the safety valve, and to pressure greater than that in the annulus
Implementation Method 3
Pressure is applied via a control line to an opposite side of the piston to displace the piston after overcoming a biasing force applied by a spring or other biasing device
Data Source
AI summary
A control system for an annulus balanced subsurface safety valve. A system for operating a safety valve in a well includes a piston of the safety valve being responsive to displace due to a pressure differential between chambers exposed to the piston; and a valve controller which alternately exposes at least one of the chambers to pressure in an annulus surrounding the safety valve, and to pressure greater than that in the annulus. A method of operating a safety valve in a well includes the steps of: opening the safety valve by biasing a piston of the safety valve to displace in response to a pressure differential between a chamber exposed to pressure greater than well pressure, and another chamber exposed to well pressure; and closing the safety valve by exposing both of the chambers to the well pressure.