Stacked Piston Safety Valve for Lower Deepwell Control Pressure
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Solution Overview
Problem
Conventional subsurface safety valves require high control line pressures and are limited in deployment depth due to the need for strong springs to overcome downhole forces, making it challenging to deploy them at greater depths while maintaining safety and efficiency.
Innovation Solution
A stacked piston safety valve with different piston diameters is used, where a smaller piston is actuated by a larger piston in a chamber, reducing the force required to open and close the valve, allowing for lower control line pressures and increased deployment depths by balancing pressure differentials and utilizing weaker springs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the deployment depth of the subsurface safety valve is increased, then the valve can be deployed at greater depths, but the control line pressure required to open the closure mechanism increases
Solution Approach 1:
The single piston is divided into multiple stacked pistons with different diameters. The first piston has a larger diameter and is acted upon by control line pressure, while the second piston has a smaller diameter and works against the spring force. This segmentation allows the system to achieve the necessary force multiplication without requiring proportionally higher control line pressures, enabling deployment at 16,200 feet with only 9,000 psi control line pressure.
Solution Approach 2:
The invention transitions from a single-dimensional force application (one piston) to a multi-dimensional stacked configuration. By arranging pistons of different diameters in a vertical stack and applying pressure differentials across each stage, the system creates a cascading force multiplication effect that overcomes the linear relationship between depth and required control pressure.
2Strength
If stronger springs are used to overcome downhole forces at greater depths, then the valve can be secured at deeper locations, but the control line pressure requirements increase
Solution Approach 1:
The spring force requirement is segmented across multiple piston stages. Instead of using one extremely strong spring that would require proportionally high control pressure, the system uses a first spring acting on the larger-diameter piston and a second spring acting on the smaller-diameter piston. This creates a stepped force application that reduces the peak control line pressure needed.
Solution Approach 2:
The invention changes the diameter parameter of the pistons to create a force transformation ratio. By having the first piston with a larger diameter than the second piston, the system transforms the pressure input into a more efficient force output, allowing weaker springs to achieve the same effective closing force that would otherwise require stronger springs and higher control pressures.
3Device complexity
If a single piston design is used, then the device structure is simpler, but the control line pressure requirements are higher for deep deployment
Solution Approach 1:
The single piston is segmented into multiple stacked pistons with different diameters. The first piston has a larger diameter and is acted upon by control line pressure, while the second piston has a smaller diameter and works against the spring force. This segmentation allows the system to achieve the necessary force multiplication without requiring proportionally higher control line pressures.
Solution Approach 2:
The stacked piston configuration resembles a nested doll structure, where pistons of different diameters are arranged concentrically or in a stacked arrangement within the same valve body. This nested configuration allows multiple force stages to be compactly integrated, increasing functional complexity without proportionally increasing the overall device footprint or operational complexity.
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 reduces control line pressure requirements and enables the deployment of safety valves at greater depths, from 9300 feet to 16,200 feet, while lowering the control line pressure from 15,000 psi to 9,000 psi, enhancing operational safety and efficiency in well systems.
Implementation Method 1
A first control line can selectively communicate a first pressure to the first piston in a downhole direction, thereby causing the first piston to apply a force to the second piston
Implementation Method 2
A spring-loaded retention mechanism for closing a subsurface safety valve may exert sufficient force to overcome downhole forces exerted by fluids in the wellbore
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Certain aspects are directed to a subsurface safety valve. The subsurface safety valve includes a closure mechanism and a piston assembly for actuating the closure mechanism. The piston assembly includes a first piston disposed in a first chamber, a second piston disposed in a second chamber adjacent to the first chamber, and first and second control lines. The second chamber has a second diameter that is smaller than a first diameter of the first chamber. The first control line selectively communicates pressure to the first piston in a downhole direction. The first piston applies force to the second piston in response to pressure being communicated to the first piston. The force can cause the closure mechanism to be actuated. The second control line communicates a second pressure to the first piston in an uphole direction that reduces an amount of force for displacing the second piston an uphole direction.