Expanding Piston Subsurface Safety Valve
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Solution Overview
Problem
Subsurface safety valves in the oil and gas industry face challenges with high costs and increased energy requirements due to the need for strong springs and larger pressure control systems to overcome hydrostatic heads, leading to practical limits in depth and cost, particularly in reducing the spread between opening and closing pressures.
Innovation Solution
A subsurface safety valve design featuring an expanding piston assembly with a tapered piston bore, where the piston area increases as it moves, reducing the required control pressure and minimizing the spread between opening and closing pressures by progressively expanding to engage more hydraulic fluid, thus reducing the need for high-pressure systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If conventional hydraulic actuators with fixed-area pistons are used, then the valve can be opened at depth, but the required control pressure increases significantly and the spread between opening and closing pressures increases
Solution Approach 1:
The piston area is made variable rather than fixed. The piston expands radially outward to engage with the tapered bore wall, progressively increasing its effective area as it moves downward. This dynamic area adjustment allows the hydraulic force to increase progressively, matching the increasing hydrostatic pressure head at greater depths, thereby reducing the required control pressure and minimizing the spread between opening and closing pressures.
Solution Approach 2:
The effective piston area parameter is changed during operation. By designing the piston with expandable elements that engage the tapered bore, the piston area transitions from a smaller initial value to a larger final value as the valve opens. This parameter change enables the hydraulic actuator to overcome the increasing hydrostatic pressure without requiring proportionally higher control pressures.
2Force
If stronger springs are used to overcome hydrostatic head, then the valve can operate at greater depths, but the cost increases and the spread between opening and closing pressures increases
Solution Approach 1:
The mechanical spring biasing system is replaced with a hydraulic force generation system. Instead of relying on a strong mechanical spring to provide the biasing force needed to overcome hydrostatic pressure, the invention uses hydraulic pressure acting on an expanding piston to generate the necessary force. This substitution eliminates the need for expensive, high-force springs while reducing the spread between opening and closing pressures.
Solution Approach 2:
Hydraulic pressure is used to generate the opening force instead of mechanical springs. The hydraulic fluid transmitted through the control line acts on the expanding piston, which progressively increases its area to generate sufficient force to overcome the hydrostatic head at depth. This hydraulic approach is more cost-effective and controllable than using strong mechanical springs.
3Stress or pressure
If the piston area is increased to reduce control pressure requirements, then opening force improves, but the valve size and cost increase
Solution Approach 1:
The piston area is made variable rather than fixed. The piston starts with a smaller area and expands radially outward as it moves downward, progressively increasing its effective area. This dynamic expansion allows the piston to generate sufficient hydraulic force without requiring a large initial piston volume, thereby reducing the overall valve size while meeting control pressure requirements.
Solution Approach 2:
The piston expands in the radial dimension rather than requiring a larger axial dimension. By designing the piston with expandable elements that engage the tapered bore wall radially, the effective area increases without proportionally increasing the piston's axial length or overall valve size. This dimensional approach allows force generation while maintaining compact valve dimensions.
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 design allows for reduced pressure requirements to open the valve, smaller and less expensive pressure control systems, and lower operational costs while maintaining safety and efficiency across varying depths.
Implementation Method 1
hydraulic fluid pressure to move the piston assembly from a first position within the piston bore to a second position
Implementation Method 2
the expanding piston is configured to progressively increase its piston area as the piston assembly moves from the first end to the second end
Data Source
AI summary
Disclosed are subsurface safety valves having an expanding piston used to increase the opening force for the safety valve. One disclosed safety valve includes a housing having a piston bore defined therein and configured to receive hydraulic fluid pressure, the piston bore providing a tapered portion having a first end and a second end, wherein a cross-sectional diameter of the tapered portion progressively increases from the first end to the second end, and a piston assembly movably arranged within the piston bore and comprising a piston rod that extends longitudinally within at least a portion of the piston bore and an expanding piston coupled to the piston rod, wherein the expanding piston is configured to move between a contracted configuration and an expanded configuration to sealingly engage the tapered portion as the piston assembly moves between the first and second ends.