Flow Activated Valve Shear Pin Mechanism for Wellbore Plugs
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Solution Overview
Problem
Existing frac plug valve designs fail to allow bypass flow if the perforating gun misfires, preventing the introduction of a replacement gun, and often suffer from issues like ball jamming, variability in flow rates, and difficulty in mill-out times due to hardened steel springs.
Innovation Solution
A valve assembly with a valve member initially pinned in an open position, using shear pins or alternative retainers that allow bypass flow until a predetermined flow rate is reached, shearing the pins to close the valve, ensuring a replacement gun can be run in and allowing subsequent treatments, with a backup seat for emergency closure if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ball is pumped to a seat to close flow, then flow is stopped, but it takes time and water to get the ball pumped to the seat
Solution Approach 1:
The valve member is pre-positioned in the flow path and held open by shear pins before the operation begins. The shear pins are designed to fail at a predetermined flow rate, automatically closing the valve without requiring time-consuming ball pumping operations. This preliminary positioning and automatic activation mechanism eliminates the delay associated with pumping balls to seats.
2Adaptability or versatility
If a caged ball is used that lifts off a seat when the gun is advanced, then the ball can be retained, but if the gun fails to fire there is no way to use flow to deliver a replacement gun as any such flow in the downhole direction seats the ball on the seat
Solution Approach 1:
Instead of using flow to activate the valve (which would prevent replacement gun delivery), the invention uses a mechanical retention mechanism (shear pins) that holds the valve open against the flow. The valve is designed to remain open during gun replacement operations, and only closes when the shear pins fail at the predetermined flow rate. This inverted approach allows both replacement gun capability and flow activation reliability.
3Ease of operation
If spring biased check valves are used, then flow can be controlled, but they will shut with flow in the downhole direction leaving the same problem of how to run in a replacement gun
Solution Approach 1:
The invention removes the spring mechanism from the valve assembly, retaining only the ball, seat, and shear pin components. By extracting the spring element that would cause automatic closing with downhole flow, the valve remains open and controllable during gun replacement operations. The flow control capability is maintained through the ball-seat mechanism, while the spring-induced automatic shutdown is eliminated.
4Reliability
If a ball sits on a spring with a covering cage to retain the ball, then the ball can be held off the seat, but the ball may jam around the spring rather than seating off on the seat for a clean seal
Solution Approach 1:
The invention removes the spring and complex cage structure, retaining only the essential ball, seat, and shear pin components. This simplification eliminates the risk of ball jamming around the spring while maintaining reliable sealing through the direct ball-to-seat contact. The shear pins provide the necessary retention function without introducing mechanical complexity that could cause jamming.
5Strength
If hardened steel springs are used in the valve assembly, then the valve can be biased, but quick mill-out time is essential and springs are not easily millable
Solution Approach 1:
The invention completely removes the hardened steel spring from the valve assembly, eliminating the mill-out problem entirely. The valve biasing function is replaced by the shear pin mechanism, which can be easily milled out. This extraction of the problematic spring component directly addresses the ease of manufacture concern while maintaining the necessary valve functionality through alternative means.
6Extent of automation
If the force on the ball due to flow changes as it moves in the passage due to compressing the spring, then the valve can be actuated, but this adds variability to the predetermined flow rate to close the valve
Solution Approach 1:
The invention removes the spring component that causes variable force on the ball during actuation. Without the spring, the ball experiences consistent flow forces as it moves through the passage, eliminating the variability in the predetermined flow rate needed to close the valve. The shear pin provides a fixed mechanical constraint that fails at a consistent load, ensuring precise and repeatable valve actuation at the desired flow rate.
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 continuous flow through the plug if the gun misfires, ensuring a replacement gun can be introduced, and securely closes the valve with increased flow, addressing issues of ball jamming and spring variability, while facilitating quick mill-out and reliable operation.
Implementation Method 1
flow around the plug above a predetermined level will shear retainers for the plug and let the plug land on its seat closing flow
Data Source
AI summary
A valve assembly for a plug to close off a zone in the well for further treatment above the plug features a valve member initially pinned in an open position where flow up to a predetermined level can move through without dislodging the valve plug to move to its associated seat. If the perforating gun misfires a replacement gun can be run in with flow as the plug is still retained in the position for flow through the plug. On the other hand flow around the plug above a predetermined level will shear retainers for the plug and let the plug land on its seat closing flow in a downhole direction for treatment.