Millable Downhole Plug With Melt-Set Metal Seal and Easy Milling
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Solution Overview
Problem
Existing permanent downhole plugs require complex milling operations due to parts rotating together with the milling tool, and the use of bismuth as a barrier material is costly and inefficient, while existing solutions for forming plugs in wellbore seals are cumbersome and require large amounts of bismuth.
Innovation Solution
A downhole millable permanent plug with a mandrel, sealing elements, and a metal body that expands upon solidification, using bismuth or bismuth alloy to form a seal and anchor, allowing easy milling by wedging the sealing elements radially outward during expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permanent plug is set in a production string, then the production string can be permanently abandoned in the well, but the setting operation requires complex equipment and procedures including a setting tool, overshot, and swab line
Solution Approach 1:
The invention extracts the setting mechanism from complex external equipment and integrates it into the plug body itself. The setting tool is eliminated by incorporating a setting mechanism that uses the existing production string as the setting element, removing the need for overshots, swab lines, and other complex setting equipment.
Solution Approach 2:
The plug performs its own setting operation using the production string as the setting element. The setting mechanism is activated by the production string itself during normal operations, allowing the plug to set itself without requiring external setting tools or complex procedures.
2Reliability
If a permanent plug is set using conventional methods, then the plug can be securely installed, but the process requires multiple trips and specialized equipment including coiled tubing or wireline operations
Solution Approach 1:
The invention segments the plug into deployable sections that can be inserted through the production string in a single operation. The plug body is designed to be divided into sections that expand or deploy after insertion, eliminating the need for multiple trips to complete the installation.
Solution Approach 2:
The plug is pre-configured with setting mechanisms and deployment features that enable immediate setting upon insertion. The setting mechanism is prepared in advance within the plug body, allowing the plug to set itself automatically after being deployed through the production string without requiring subsequent setting trips.
3Ease of repair
If a millable plug body is used, then the plug can be removed by milling, but the plug body material must be specifically designed to be millable while maintaining setting reliability
Solution Approach 1:
The invention applies different material properties to different parts of the plug. The plug body is made of a millable material that can be easily removed by milling, while the setting mechanism uses a separate non-millable material that maintains setting reliability. This local differentiation of material properties allows the plug to be both easily removable and reliably set.
Solution Approach 2:
The plug employs composite construction with a millable plug body material and a non-millable setting mechanism material. This composite structure allows the plug body to be removed by milling while the setting mechanism remains intact to ensure reliable setting during installation.
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
The plug enables easy milling by preventing rotation during milling and reduces the need for large bismuth quantities, providing a cost-effective and efficient sealing solution with both anchoring and sealing functions.
Implementation Method 1
setting mechanisms that utilize the production string as the setting mechanism
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
The present invention relates to a downhole millable permanent plug (1) for permanently sealing of a downhole well (WE). The permanent plug (1) comprises a mandrel (10), a first sealing element (20a) provided radially outside of the mandrel (10), a second sealing element (20b) provided radially outside of the mandrel (10) at a distance from the first sealing element (20a) and a metal body (40) provided radially outside of the mandrel (10) between the first sealing element (20a) and the second sealing element (20b). The plug (1) further comprises a setting system (50) comprising a heater (51) for melting the metal body (40); wherein the permanent well plug (1) is configured to be in the following states: - a run state, in which the first sealing element (20a) and the second sealing element (20b) are radially retracted; - an intermediate state, in which the first sealing element (20a) and the second sealing element (20b) are radially expanded into contact with the well (WE); - a set state, in which the metal body (40) has been melted by the heater (51) and subsequently solidified into contact with the well (WE).