Downhole Wireline Cutting Tool Shear Mechanism
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Solution Overview
Problem
Current methods for severing wirelines in wellbore operations are either inefficient or cause unpredictable damage, particularly when relying on points of weakness or explosive ballistic release tools, which can lead to incomplete separation and ancillary damage.
Innovation Solution
A wireline cutting tool comprising an upper and lower tubular sub, a knife housing with tapered bore, and a plunger that applies distinct shear loads to pinch and sever the wireline, ensuring a clean and predictable cut, with an electrical connection sub for signal transmission and a method involving two-step shear loads to manage the cutting process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a point of weakness is used in the wireline to allow pulling out the downhole tool, then the tool can be retrieved if stuck, but the wireline may fray and interfere with fishing operations
Solution Approach 1:
The wireline release system is segmented into distinct functional zones: a protected cutting mechanism section and a sacrificial weak point section. The cutting mechanism includes a housing with a bore, a plunger, and a knife that can sever the wireline in a controlled manner, while the weak point is positioned separately to provide retrieval capability without fraying interference
Solution Approach 2:
A fishing neck is introduced as an intermediary component that provides a secure attachment point for fishing operations. The fishing neck is positioned above the cutting mechanism and weak point, allowing fishing tools to engage with the downhole tool without encountering frayed wireline ends
2Productivity
If explosive ballistic release tools are used to sever the wireline, then the wireline can be cut, but unpredictable damage may occur to tools and wellbore
Solution Approach 1:
The explosive cutting mechanism is replaced with a mechanical cutting system consisting of a plunger that drives a knife through the wireline. This mechanical substitution eliminates the unpredictable damage associated with explosives while maintaining effective wireline severing capability. The knife is contained within a housing that directs the cutting action precisely
Solution Approach 2:
A grease pocket is positioned between the plunger and the knife to provide cushioning and control the cutting action. The grease absorbs excess energy and ensures a controlled, predictable cut rather than a violent severing, preventing damage to surrounding tools and wellbore structures
3Ease of operation
If a single shear load is used to release the plunger, then the mechanism activates, but complete separation of the wireline cannot be ensured
Solution Approach 1:
The shear load mechanism is segmented into two distinct stages with different shear strengths. The first shear pin has a lower shear strength to initiate plunger movement and begin the cutting process, while the second shear pin has a higher shear strength to complete the wireline separation. This segmentation ensures complete separation while maintaining easy activation
Solution Approach 2:
The first shear pin is designed to fail at a lower load to perform the preliminary action of releasing the plunger and initiating the cutting process. This preliminary action prepares the system for the second, more forceful shear event that completes the separation, ensuring reliable full detachment
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 efficient and predictable severing of wirelines, reducing the risk of damage to tools and wellbores, while ensuring complete separation of the wireline, facilitating the retrieval of downhole tools without leaving remnants.
Implementation Method 1
A wireline cutting tool includes a plunger configured to slide up the bore of the lower sub in response to a first shear load applied by a wireline
Implementation Method 2
The knives are configured to slide up the bore of the knife housing from the second end towards the first end in response to a second shear load
Data Source
AI summary
A wireline cutting tool. The wireline cutting tool comprises an elongated tubular body. A knife housing resides within the tubular body proximate an upper end, while a plunger resides within the tubular body proximate a lower end. An electric wireline passes through a bore of the knife housing and the plunger en route to an electrical connection sub. The electrical connection sub includes a pin that transmits signals from the electric wireline down to a downhole tool. The plunger is configured to slide up the bore of the lower sub in response to a first upward shear load applied by the wireline. This causes the plunger to act against knives residing within the knife housing. The knives are configured to travel up the bore of the upper sub in response to a second upward shear load applied by the plunger, pinching the wireline until severed. The second shear load is greater than the first shear load, creating a two-stage cutting tool.