Millable Permanent Downhole Plug with Melt-Set Metal Sealing
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Solution Overview
Problem
Existing permanent downhole plugs require complex milling operations due to rotation of plug parts with the milling tool, and the use of bismuth as an expanding barrier necessitates large amounts, which is a critical raw material.
Innovation Solution
A downhole millable permanent plug with a mandrel, sealing elements, and a metal body that expands radially upon melting and solidification, providing both anchoring and sealing functions, reducing the need for separate anchoring elements and elastomeric seals, and minimizing bismuth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If a milling operation is performed on a permanent plug, then the plug can be removed, but parts of the plug may rotate together with the milling tool preventing effective milling
Solution Approach 1:
The patent extracts the harmful rotational movement by introducing a stationary anchor element that remains fixed in the wellbore during milling operations. The anchor element is deliberately separated from the rotating plug components, preventing the plug from rotating with the milling tool while allowing effective milling to occur.
Solution Approach 2:
The patent applies preliminary anti-action by pre-installing an anchor element that counteracts the unwanted rotation before the milling operation begins. The anchor element is positioned and secured in advance to provide resistance against rotational forces during the subsequent milling process.
2Reliability
If bismuth is used as an expanding barrier material, then sealing and anchoring functions are provided, but large amounts of bismuth are required which is a critical raw material
Solution Approach 1:
The patent segments the barrier function into two separate components: an anchor element for mechanical anchoring and a reduced-quantity bismuth barrier for sealing. This segmentation allows each component to be optimized independently, reducing the total bismuth requirement while maintaining reliable sealing and anchoring functions.
Solution Approach 2:
The anchor element serves multiple functions: it provides mechanical anchoring in the wellbore, prevents rotation during milling operations, and supports the bismuth barrier material. This multi-functionality reduces the need for large amounts of bismuth to perform all functions alone.
3Ease of operation
If steel is used for the mandrel to prevent rotation during milling, then rotation is prevented, but the cost increases compared to cheaper materials like cast iron
Solution Approach 1:
The patent extracts the rotation-prevention function from the mandrel material selection and assigns it to a separate anchor element. This allows the mandrel to be made from cost-effective materials like cast iron while the anchor element, which specifically handles rotation prevention, can be made from higher-strength materials if needed.
Solution Approach 2:
The patent employs a disposable anchor element that can be left in the wellbore to prevent rotation during milling operations. This allows the use of simpler, cheaper mandrel materials since the rotation-prevention function is handled by the sacrificial anchor element rather than requiring expensive steel throughout the entire assembly.
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
Facilitates easy milling of the plug by preventing rotation during milling and reduces the amount of bismuth required, thus lowering costs and reliance on critical raw materials.
Implementation Method 1
a setting system comprising a heater for melting the metal body
Implementation Method 2
the metal body has been melted by the heater and subsequently solidified into contact with the well
Implementation Method 3
the metal body has been melted by the heater and subsequently solidified
Data Source
AI summary
A downhole millable permanent plug, which permanently seals a downhole well, includes a mandrel, first and second sealing elements, a metal body, and a setting system. The mandrel has a longitudinal axis. The first sealing element is provided radially outside of the mandrel. The second sealing element is provided radially outside of the mandrel at a distance from the first sealing element. The metal body is provided radially outside of the mandrel between the first sealing element and the second sealing element. The setting system includes a heater for melting the metal body. The permanent well plug is configured to be in the following states: a run state, in which the first sealing element and the second sealing element are radially retracted; an intermediate state, in which the first sealing element and the second sealing element are radially expanded into contact with the well; and a set state, in which the metal body has been melted by the heater and subsequently solidified into contact with the well.