Retrieval System Safety Unit Anchoring Mechanism
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Solution Overview
Problem
Existing retrieval systems for well components, such as plugs, often get stuck when the intervention tool is submerged in a well and cannot be disconnected due to a restriction, leading to failure in releasing the tool from the plug.
Innovation Solution
A retrieval system comprising a tool string with a connection tool, a force generator, and an anchoring section, along with a safety unit that surrounds the tool string and has projectable elements to anchor it, allowing the tool string to move relative to the restriction, enabling the connection tool to be released by applying a hammering force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the intervention tool is submerged into the well and docks in a restriction to retrieve a plug, then the plug can be pulled by retracting the connection tool, but the tool cannot be disconnected when the plug is stuck because the tool cannot move downwards due to the restriction
Solution Approach 1:
The system is divided into two independent parts: the tool string (intervention tool) and the safety unit (casing). The tool string performs the retrieval operation while the safety unit provides a backup anchoring mechanism. This segmentation allows the tool string to be released independently by hammering, while the safety unit remains anchored to the restriction, resolving the disconnection problem.
Solution Approach 2:
The safety unit acts as an intermediary between the tool string and the restriction. Instead of the tool string directly anchoring to the restriction (which prevents disconnection), the safety unit mediates by providing its own anchoring points on the tool string. This intermediary structure allows the tool string to be released while the safety unit remains in place.
2Strength
If the tool string is anchored directly to the restriction for stable retrieval, then the retrieval operation can proceed, but the tool string cannot be released by hammering when stuck
Solution Approach 1:
The anchoring function is segmented between two components: the safety unit provides the primary stable anchoring to the restriction, while the tool string provides a secondary, releasable anchoring through its projectable elements. This segmentation allows stable retrieval while maintaining release capability through the tool string's independent anchoring mechanism.
Solution Approach 2:
The safety unit is positioned beforehand to provide a backup anchoring mechanism. When the tool string becomes stuck, the safety unit's projectable elements can engage with the restriction to prevent catastrophic failure, cushioning the impact of the stuck condition and allowing for safe tool release.
3Stability of the object's composition
If the safety unit surrounds the tool string with a tight fit to prevent lateral movement, then the tool string is securely positioned, but the projectable elements cannot project sufficiently to anchor the tool string
Solution Approach 1:
The safety unit has different diameters at different locations: a first diameter at the open end that is larger than the tool string diameter, and a second diameter at the closed end that is smaller. This local variation in geometry allows the projectable elements to project sufficiently for anchoring while maintaining secure positioning of the tool string in the intermediate region.
Solution Approach 2:
The safety unit transitions from a uniform cylindrical shape to a tapered or conical shape, changing the dimensional characteristics along its length. This dimensional change creates the necessary space for projectable element extension while maintaining tool string stability, effectively using the longitudinal dimension to resolve the conflict between fit and projection capability.
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3
AI summary
The present invention relates to a retrieval system for retrieving a well component, such as a plug, from a well tubular metal structure having a restriction and a top, said retrieval system comprising a tool string having a longitudinal extension and comprising a connection tool configured to connect with the well component, a force generator having a first part and a second part which is connectable with the connection tool and movable in relation to the first part for providing the axial force in the longitudinal extension, an anchoring section having at least one projectable element for anchoring the tool string, wherein the retrieval system further comprises a safety unit surrounding the tool string and having at least one wall and at least one abutment face configured to abut the restriction, said at least one projectable element abutting. Furthermore, the present invention relates to a downhole system and to a downhole well component retrieval method.