Borehole Plug Split Lock Ring for Flow-Back Retrieval
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Solution Overview
Problem
Existing borehole plug designs face high shear loading issues with ratchet teeth breaking under operating pressures, leading to prolonged milling times for removal, especially in applications like fracturing where multiple plugs need to be quickly removed.
Innovation Solution
A split lock ring with a wedge or triangular sectional shape and downhole-oriented surface treatment is used to compress and hold the sealing element, allowing for differential pressure management and easy disengagement of slips when pressure is lowered, enabling plugs to be flowed back to the surface for safe removal without milling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a body lock ring assembly with ratcheting pattern is used to maintain set position, then the plug can hold differential pressure, but the ratchet teeth break under high shear loading within operating pressure range
Solution Approach 1:
The invention removes the vulnerable ratcheting pattern from the lock ring design. Instead of relying on ratchet teeth that break under shear loading, the lock ring uses a smooth bore design that eliminates the ratcheting mechanism entirely, thereby removing the weak point while maintaining pressure holding capability through the lock ring's structural engagement with the mandrel and sealing element.
Solution Approach 2:
The invention replaces the mechanical ratcheting system with a simplified lock ring structure that relies on friction and geometric constraints rather than interlocking teeth. The lock ring engages with the mandrel through a smooth interface and maintains position through the compressed sealing element's reaction force, eliminating the need for ratchet teeth and their associated shear loading vulnerabilities.
2Adaptability or versatility
If multiple plugs are used in zone treatment, then zone isolation is improved, but milling time increases proportionally
Solution Approach 1:
The invention removes the need for milling operation entirely by enabling flow-back retrieval. The lock ring design allows the plug to be released and flowed back to surface through the wellbore using pressure differential, eliminating the time-consuming milling process that previously had to be performed on each plug individually.
Solution Approach 2:
The invention enables recovery of the plug components through flow-back rather than discarding them via milling. The lock ring and other plug components are designed to be released and transported to surface intact, where they can be recovered and reused or properly disposed of, reducing both time and material waste compared to milling each plug in place.
3Ease of manufacture
If readily milled composite materials are used for plug components, then milling removal is facilitated, but cost increases and milling time is prolonged
Solution Approach 1:
The invention removes the dependency on milling by designing a plug retrieval system based on flow-back. The lock ring and composite components are designed to withstand wellbore conditions and enable controlled release, allowing the entire plug assembly to be flowed back without requiring milling, thereby eliminating the time and cost associated with milling composite materials.
Solution Approach 2:
The invention replaces the mechanical milling removal process with a fluid-based flow-back retrieval system. Instead of using milling equipment to remove composite plug material, the system uses pressure differential to flow the plug components back to surface, substituting a mechanical removal process with a hydraulic transport process that is both faster and more cost-effective.
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 shear stress on the lock ring, shortens milling time, and allows for the removal of multiple plugs without the need for milling, reducing costs and efficiently managing differential pressures during treatment and retrieval.
Implementation Method 1
The ring is tapered in cross section to allow it to act as a wedge against reaction force tending to relax the components from the set position
Implementation Method 2
The side of the ring facing the mandrel has a surface treatment that provides minimal resistance in the setting direction and digs into the mandrel to resist reaction forces from the compressed sealing element in the set position
Implementation Method 3
When the treatment is concluded pressure from above is relieved or lowered so that the plug or plugs disengage at slips designed to resist differential pressure from above
Data Source
AI summary
A borehole plug or packer for treating is designed to be flowed back to a surface location after use. When the treatment is concluded pressure from above is relieved or lowered, and well fluid is flowed back, so that the plug or plugs disengages at slips designed to resist differential pressure from above. The application of differential pressure from below causes the lower slips to release one or more of such plugs in the hole into specialized sub surface or surface capture equipment so that well pressure is relieved before removal of the plugs from specialized subsurface or surface capture equipment.