Plug Assembly Shear Ring and Snap Ring Mechanism
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Solution Overview
Problem
Existing plug assemblies for petroleum well boreholes are not robust enough and often have many moving parts, leading to malfunctions in harsh well conditions with high pressure and temperature, and are not easily opened or closed without risking debris or accidental actuation.
Innovation Solution
A plug assembly with a frangible disc that can be opened by controlled pressure differential, featuring a plug, a breaker object, a shear ring, and a snap ring, where the shear ring shears to allow axial movement and the snap ring locks the seat in place, ensuring complete and predictable breaking without partial opening or debris entry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a plug assembly with many moving parts is used to enable opening and closing, then the plug can be opened and closed, but the reliability decreases due to malfunctions in harsh well conditions
Solution Approach 1:
The plug assembly is divided into distinct functional segments: a frangible disc for fluid blocking, a shear ring for controlled activation, and a snap ring for positioning. This segmentation allows each component to perform its specific function reliably without complex interactions between moving parts, reducing malfunction risk while maintaining operability.
Solution Approach 2:
The shear ring is pre-positioned and pre-loaded against the frangible disc during assembly. The snap ring is pre-installed to hold the shear ring in its initial position. These preliminary actions ensure that when activation pressure is applied, the sequence of events (shear ring movement, frangible disc breaking) occurs automatically without requiring additional control mechanisms or moving parts during operation.
2Ease of operation
If a frangible disc is used to block fluid flow, then the plug can be opened by breaking the disc, but debris may enter the well during breaking
Solution Approach 1:
The shear ring acts as an intermediary component between the activation pressure and the frangible disc. It controls the breaking process by shearing in a predetermined manner, which directs the fragmentation of the frangible disc in a controlled way that minimizes debris dispersal into the wellbore.
Solution Approach 2:
The frangible disc is designed to break into controlled fragments rather than large debris pieces. The breaking process, while necessarily creating some debris, is converted into a benefit by ensuring the fragments are small and manageable, and by using the shear ring to direct the breaking force in a way that prevents uncontrolled debris dispersal.
3Ease of operation
If the plug assembly is designed to be opened by pressure differential, then opening can be achieved, but accidental actuation may occur
Solution Approach 1:
The shear ring is designed with specific mechanical properties (strength, thickness, geometry) that establish a high threshold pressure differential required for activation. This parameter setting ensures that normal pressure fluctuations during well operations are insufficient to trigger opening, while a deliberately applied pressure surge can reliably activate the mechanism.
Solution Approach 2:
The snap ring is pre-installed to hold the shear ring in its locked position against the frangible disc. This preliminary anti-action creates a mechanical barrier that prevents accidental activation by normal pressure variations, while still allowing deliberate activation when sufficient pressure is applied to overcome the snap ring's holding force.
4Strength
If metal plugs are used for robustness, then strength is improved, but removal results in debris and damage to tubing
Solution Approach 1:
The frangible disc is designed as a disposable component made of frangible material that is intended to be broken and discarded after serving its temporary fluid blocking function. This eliminates the need for complex removal operations that could damage tubing, as the disc simply breaks into small fragments that can be safely managed.
Solution Approach 2:
The plug assembly uses composite construction: a frangible material for the disc that breaks cleanly, combined with metal components (shear ring, snap ring) for structural support and controlled activation. This composite approach provides the robustness needed for harsh well conditions while ensuring clean, controlled deactivation without metal-on-metal damage.
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
The plug assembly maintains a fluid-tight barrier until broken, then fully opens with predictable and repeatable pressure, minimizing the risk of malfunction and debris entry, and stays in place once open, ensuring non-restricted fluid flow and safety.
Implementation Method 1
the shear ring is arranged such that when a threshold pressure differential is applied to a surface of the plug, the shear ring shears, and allows for axial movement of the seat
Implementation Method 2
when a threshold pressure differential is applied to a surface of the plug
Data Source
AI summary
A plug assembly arranged in a housing including: a plug, a breaker object, a seat, a shear ring and a snap ring. The plug is supported by the seat and the shear ring prevents the seat from moving in an axial direction. The shear ring is arranged such that when a threshold pressure differential is applied to a surface of the plug, the shear ring hears and allows for axial movement of the seat. The plug assembly has a first position, a second position, and a third position. In the first position, the plug is not in contact with the breaker object, in the second position, the shear ring has sheared and the plug is in contact with the breaker object causing the plug to break, and in the third position, occurring during or after the plug makes contact with the breaker object, the snap ring is arranged to lock the seat into place to prevent the seat from moving axially.