Borehole Plug Split Lock Ring Shear Failure
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Solution Overview
Problem
Existing borehole plug designs face high shear loading issues due to fracturing pressures, leading to ratchet teeth failure and prolonged milling times for removal, especially when multiple plugs need to be quickly removed during treatments like fracturing, and existing solutions fail to efficiently retrieve plugs to the surface using formation pressure.
Innovation Solution
A borehole plug design featuring a split lock ring with a wedge sectional shape and downhole-oriented surface treatment that resists reaction forces, allowing differential pressure handling and plug retrieval by flowing back the plug under reduced pressure from above, aided by wiper devices that accommodate tubular size changes during ascent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ratcheting body lock ring assembly is used to maintain the set position of the borehole plug, then the plug can hold differential pressure from above, but the ratchet teeth break under high shear loading from fracturing pressures
Solution Approach 1:
The invention removes the vulnerable ratcheting mechanism entirely and extracts only the essential locking function. The body lock ring assembly is replaced with a simpler design that eliminates ratchet teeth, thereby removing the component that failed under shear loading while retaining the ability to maintain the set position against differential pressure.
Solution Approach 2:
The invention employs a disposable body lock ring assembly that is designed to be set and then retrieved or left in place after use. This approach accepts the component as single-use, eliminating the need for complex, durable ratcheting mechanisms and allowing optimization for initial setting reliability rather than repeated use durability.
2Loss of time
If the borehole plug is designed for quick removal during treating operations, then milling time is reduced, but the lock ring must withstand high shear loading
Solution Approach 1:
The invention extracts the problematic ratcheting mechanism that required milling for removal and replaces it with a design that can be quickly retrieved or left in place. This eliminates the need for time-consuming milling operations while the simplified lock ring design reduces shear loading concerns.
Solution Approach 2:
The invention introduces dynamic retrieval capability where the plug can be quickly pulled out of the borehole using a retrieval tool that engages with the plug body. This dynamic removal method replaces the static milling process, dramatically reducing removal time without requiring the lock ring to withstand extreme shear loads during removal.
3Productivity
If multiple plugs need to be removed during fracturing treatments, then productivity is maintained, but milling each plug prolongs the overall process
Solution Approach 1:
The invention removes the time-consuming milling step from the plug removal process. By eliminating the ratcheting mechanism that requires milling, each plug can be quickly retrieved or left in place, allowing multiple plugs to be handled in rapid succession without interrupting production continuity.
Solution Approach 2:
The invention designs the plug with a retrieval mechanism that allows quick engagement and extraction. The body lock ring assembly is configured to work with retrieval tools that can be deployed immediately after treatment, enabling preliminary preparation for rapid removal of multiple plugs without requiring milling operations between treatments.
4Stability of the object's composition
If the lock ring is designed to prevent relative movement in the opposite direction, then the set position is maintained, but the ratchet teeth are subjected to high shear loading
Solution Approach 1:
The invention extracts the ratcheting mechanism that created the shear loading problem while retaining the essential function of preventing relative movement. The body lock ring assembly uses a different approach to maintain set position that does not involve interlocking ratchet teeth, thereby eliminating the shear loading vulnerability.
Solution Approach 2:
The invention replaces the mechanical ratcheting system with a different locking mechanism that uses friction, deformation, or alternative mechanical principles to prevent relative movement. This substitution eliminates the ratchet teeth and their associated shear loading issues while maintaining the stability of the set position.
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, enables efficient plug retrieval without milling, and shortens removal time by allowing plugs to be captured above or below the wellhead, maintaining production continuity without the need for milling.
Implementation Method 1
an apparatus is employed that can enlarge to bridge a growing gap on the way out of the borehole so that the plug velocity with formation pressure can continue to move the flowed plug back to capture equipment
Implementation Method 2
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 3
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
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. Packers or plugs are captured above, below or at a wellhead in a receptacle. Production ensues without milling with the captured plugs or packers in place or removed.