Removable Wellbore Plugging Using Low-Melting Alloy
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Solution Overview
Problem
Existing tubing plugs in subterranean wells face issues such as fragility, leakage, debris generation, and operational risks during removal, with previous solutions like ceramic discs, dissolvable materials, and mechanical devices failing to provide reliable and safe fluid barrier functionality.
Innovation Solution
A method and apparatus utilizing a metal alloy with a melting point selected based on reservoir temperature, sealed between the tubing and a sleeve, which is heated above its melting point using a thermite element to form a fluid barrier plug that can be easily removed without leaving debris, utilizing a bismuth and tin eutectic alloy for corrosion resistance and controlled dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ceramic discs are used as tubing plugs, then they can provide fluid barrier functionality, but they are fragile and vulnerable to leaking or being accidentally broken
Solution Approach 1:
The patent changes the material parameter from ceramic to low-melting-point alloy, which fundamentally alters the mechanical properties while maintaining the fluid barrier function. The alloy provides both reliability and mechanical strength through its unique phase change behavior at controlled temperatures.
Solution Approach 2:
The invention uses a composite structure combining a low-melting-point alloy with a sheath material, creating a material system that exhibits both the sealing reliability of the alloy and the mechanical protection of the sheath, resolving the strength-reliability contradiction.
2Reliability
If dissolvable materials protected by impermeable sheaths are used, then they can provide fluid barrier functionality, but accidental puncture of the sheath will commence dissolution and cause leaking
Solution Approach 1:
The patent changes the dissolution parameter by using a low-melting-point alloy instead of dissolvable materials, controlled by temperature rather than chemical dissolution. This eliminates the harmful leakage effect while maintaining reliable fluid barrier functionality.
Solution Approach 2:
The invention replaces the chemical dissolution mechanism with a thermal melting mechanism, where the plug is removed by heating above the melting point rather than chemical dissolution, eliminating the risk of accidental leakage.
3Duration of action of stationary object
If slowly dissolving materials are used as tubing plugs, then they can maintain plug function during completion operations, but their dissolution rate is fluid-dependent and difficult to control
Solution Approach 1:
The patent changes the controlling parameter from fluid-dependent chemical dissolution to temperature-controlled thermal melting. The duration and removal timing are precisely controlled by temperature parameters rather than fluid composition, achieving both required duration and controllability.
4Reliability
If mechanical devices, glass, and other materials are used as plugs, then they can function well as plugs, but their removal by cutting or mechanical fracture is high-risk and can result in debris being left in the well
Solution Approach 1:
The invention utilizes the phase transition of the low-melting-point alloy from solid to liquid when heated above its melting point. This phase change allows complete removal of the plug material without mechanical fracture, eliminating debris generation while maintaining reliable plug functionality during completion operations.
Solution Approach 2:
The patent replaces mechanical removal methods (cutting or fracture) with thermal melting, substituting a mechanical system with a thermal system that eliminates harmful debris generation while achieving complete plug removal.
5Ease of manufacture
If downhole manufacturing of casing plugs is performed, then casing plugs can be created, but it requires cumbersome operations after completion has landed, increasing costs and operational risks
Solution Approach 1:
The patent applies preliminary action by pre-attaching the low-melting-point alloy plug to the tubing before well entry. This eliminates the need for complex downhole manufacturing operations, reducing both cost and operational risk while maintaining manufacturing capability.
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 solution provides a reliable, debris-free, and cost-effective removable plugging system that maintains well integrity and safety by ensuring the metal alloy melts at a temperature higher than the reservoir temperature, avoiding damage to well components and ensuring complete removal without leaving residues.
Implementation Method 1
heating the metal alloy above the melting point while the tubing is inserted into the wellbore such that the metal alloy flows from the tubing and the fluid barrier plug is eliminated
Implementation Method 2
GB 2 551 693 A discloses a downhole chemical heater having an actuator for feeding or delivering reactive heat source material or fuel into a heating zone. The chemical heater comprises a heater body housing a chemical reaction heat source material.
Data Source
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AI summary
A method and apparatus are provided for removably plugging a wellbore. The wellbore leads to a reservoir having a reservoir temperature. The method includes: selecting a melting point of a metal alloy based on the reservoir temperature; sealing the metal alloy against an interior wall of a tubing, while the tubing is above a ground in which the wellbore is drilled, such that the metal alloy defines a fluid barrier plug against flow of any portion of the reservoir through the tubing when the tubing is disposed within the wellbore; and heating the metal alloy above the melting point while the tubing is disposed within the wellbore such that the metal alloy flows from the tubing and the fluid barrier plug is eliminated.