Frac Plug Breakable Threads Prevent Premature Setting
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Solution Overview
Problem
Conventional frac plugs experience premature setting due to fluid pumping, which causes pressure changes and movement of the slips and cones, leading to inadequate positioning at the desired depth.
Innovation Solution
The frac plug design incorporates breakable threads and screws to secure the slips and cones to the mandrel, limiting linear movement and preventing premature deployment until an activation operation is performed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional slips and cones are loaded on an outer mandrel and held free-floating, then the frac plug can be assembled and deployed, but the elements move or swab during fluid pumping causing premature setting
Solution Approach 1:
The breaks threads and coupling mechanisms are pre-installed on the mandrel before deployment. These preliminary structural arrangements are designed to fail at specific points under controlled conditions, ensuring that the slips and cones remain secured during pumping operations until the intended setting moment occurs.
Solution Approach 2:
The coupling mechanisms utilize threads designed to change their mechanical properties under specific stress conditions. The breakable threads maintain integrity during normal pumping pressures but are engineered to fail at predetermined stress thresholds, transforming the structural state from secured to deployed based on pressure parameters.
2Speed
If fluid is pumped around the frac plug to position it at desired depth, then the wireline can be pumped down hole, but pressure changes cause movement of slips and cones leading to premature deployment
Solution Approach 1:
The breakable threads and coupling mechanisms are designed to resist the harmful effect of pressure-induced movement before the intended setting point. These preliminary protective structures counteract the swabbing and movement forces generated during fluid pumping, maintaining element stability until the activation pressure is reached.
Solution Approach 2:
The breakable threads serve as an intermediary element between the slips/cones and the mandrel. This intermediate coupling mechanism allows controlled force transmission during pumping while providing a predetermined failure point that enables reliable deployment when activation pressures are reached.
3Reliability
If the elements are secured with breakable threads and screws, then linear movement is limited and premature setting is prevented, but the device complexity increases
Solution Approach 1:
The coupling system is segmented into multiple independent breakable thread sections and coupling mechanisms distributed along the mandrel. Each segment independently secures specific elements (slips, cones) with dedicated breakable threads, allowing localized failure and deployment while maintaining overall structural simplicity through modular repetition of the same basic coupling design.
Data Source
AI summary
Utilizing threads and coupling mechanisms to selectively secure slips and cones directly to a mandrel, wherein a distal end of the lower slips includes projections configured to interface with depressions within a cap of the frac plug to limit the relative rotation of the slips.