Collet with Ball-Actuated Expandable Seal for Fracking Valves
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Solution Overview
Problem
Downhole tools in fracking operations face challenges with cascading ball-actuated sliding valves, where the bore size reduction from uphole to downhole restricts flow rates due to the need for smaller balls to pass through, leading to reduced fluid flow and increased frictional wear.
Innovation Solution
A flowable collet with a radially expandable portion and a ball seat sloped at an acute angle is used, allowing it to expand under pressure and form a seal with the sliding sleeve, reducing its overall diameter for easier passage and enhancing engagement with the desired sliding sleeve while maintaining sealing integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bore size is reduced from uphole to downhole to allow smaller balls to pass through, then the ball can reach the target downhole sliding valve, but the flow rate is reduced
Solution Approach 1:
The collet is designed with a radially expandable portion that can dynamically change its outer diameter. When collapsed, it has a reduced outer diameter allowing easy passage through uphole sliding valves. When expanded, it provides full engagement with the target sliding valve, maintaining bore size and flow rate without requiring progressive bore reduction.
Solution Approach 2:
The radially expandable portion of the collet can be collapsed to a reduced diameter, allowing it to pass through the bores of uphole sliding valves with minimal restriction. Once positioned at the target downhole sliding valve, it expands to engage the valve fully, effectively nesting the collet within the valve bore without requiring the valve bore itself to be reduced.
2Ease of operation
If the bore size is reduced from uphole to downhole, then smaller balls can pass through, but frictional wear increases
Solution Approach 1:
The collet dynamically adjusts its outer diameter by collapsing during passage through uphole valves to minimize contact and frictional wear, then expanding at the target valve to provide full engagement. This dynamic size adjustment reduces wear compared to a permanently reduced-bore design.
Solution Approach 2:
The collet has different effective diameters at different locations along its travel path - collapsed (smaller diameter) when passing through uphole valves to reduce wear, and expanded (larger diameter) when engaged with the target valve to provide proper sealing and actuation. This local variation in quality reduces overall frictional wear.
3Reliability
If a radially expandable portion is added to the collet, then sealing is improved, but device complexity increases
Solution Approach 1:
The radially expandable portion functions as a flexible structural element that can deform radially to engage and seal against the inner surface of the sliding valve bore. This flexible component provides reliable metal-to-metal sealing without requiring complex multi-component sealing systems.
Solution Approach 2:
The collet's outer diameter parameter is made variable through the radially expandable portion, allowing it to change from a collapsed state (smaller diameter for passage) to an expanded state (larger diameter for engagement and sealing). This parameter change enables improved sealing reliability without adding multiple separate sealing components.
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 collet design ensures reliable engagement and actuation of downhole valves, reducing frictional wear and ensuring consistent fluid flow by allowing the collet to expand and form a metal-to-metal seal, thereby effectively opening desired ports for fracking operations.
Implementation Method 1
radially outwardly expandable by at least 0.09% upon application of a pressure of at least 150 psi acting on a ball
Implementation Method 2
radially expandable portion... radially outwardly expandable
Implementation Method 3
ball seat sloped at an acute angle... expand under pressure
Data Source
AI summary
A sliding valve has a valve body, a sliding sleeve received in a longitudinal bore of the valve body, and a collet receivable in a longitudinal bore of the sliding sleeve. The valve body has one or more fluid ports on an uphole portion of the sidewall thereof. The sliding sleeve is movable between an uphole closed position closing the one or more fluid ports and a downhole open position opening the one or more fluid ports. The collet comprises a metal portion about an uphole end of the collet, and a ball seat having a ball-seat surface radially inwardly sloped from uphole to downhole at an acute slope angle with respect to a longitudinal axis of the collet. The metal portion is radially outwardly expandable under a radially outward pressure to form a metal-to-metal seal at the interface between the collet and the sliding sleeve when the collet is received in the sliding sleeve.