Downhole Closure Unit for Control Line Sealing
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Solution Overview
Problem
During plug and abandonment of wells, control lines often break or create leaks due to incomplete removal, as existing tools fail to effectively cut or seal the lines within the well tubular metal structure, leading to inefficiencies and increased costs.
Innovation Solution
A downhole assembly with a downhole closure unit comprising a first element that changes state from a fluidly open to closed configuration, using a low-melt-point alloy like bismuth tin to seal the control line, allowing for safe and complete removal of the control line before cementing, thereby preventing leaks and facilitating efficient well abandonment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control line is removed during plug and abandonment, then leak prevention is improved, but control line breaks and creates leaks due to incomplete removal
Solution Approach 1:
The control line is divided into two separate parts: a first part that remains in the well and a second part that is removed. The downhole closure unit connects these two parts, allowing the second part to be pulled out while maintaining fluid communication through the closure unit, thereby preventing leaks without requiring complete removal of the control line.
Solution Approach 2:
The downhole closure unit acts as an intermediary device between the first and second parts of the control line. It provides fluid communication channel that allows the control line to remain functional after the second part is removed, eliminating the need to cut or completely remove the control line while still preventing leaks.
2Ease of operation
If control line is not removed, then operational simplicity is improved, but control line breaks and prevents control of location
Solution Approach 1:
The control line is segmented into a removable second part and a retained first part. This segmentation allows the system to maintain simplicity by not requiring complete removal while ensuring reliability through the closure unit that prevents breaking from compromising the entire control line.
Solution Approach 2:
The downhole closure unit is installed beforehand to provide a backup fluid communication path. This cushioning measure ensures that if the control line breaks during removal operations, the closure unit maintains fluid communication and prevents loss of control over the control line location.
3Reliability
If cement is arranged down the well to create cement plug, then plug and abandonment is achieved, but control line extending across cement plug creates potential leak
Solution Approach 1:
The second part of the control line is extracted or removed from the well before cementing operations. The downhole closure unit remains in place providing fluid communication, allowing the control line to be shortened and removed to a程度 that eliminates the risk of leakage across the cement plug while maintaining necessary functionality.
4Reliability
If tool is used to cut opening in well tubular metal structure and cut control line, then control line sealing is improved, but tool complexity and operational difficulty increase
Solution Approach 1:
Instead of using complex cutting tools to seal the control line, the downhole closure unit serves as an intermediary device that provides sealing through its design. The closure unit's first element with fluid communication channel achieves sealing without requiring cutting operations, thereby maintaining reliability while reducing device complexity.
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 enables secure and leak-free plug and abandonment of wells by effectively sealing the control line, reducing operational costs and ensuring reliable well closure.
Implementation Method 1
the first element may change state from the first state to at least partly liquid or mouldable state for closing the fluid communication channel
Implementation Method 2
the first element may change state from the first state to at least partly liquid or mouldable state
Implementation Method 3
the first element may comprise a material expanding upon solidification
Data Source
AI summary
The present invention relates to a downhole assembly for permanently sealing off a control line controlling a well component of a well tubular metal structure prior to plug and abandonment of a well having a top, comprising a first part of a tubular line, a second part of the tubular line, a downhole closure unit arranged between the first part and the second part of the tubular line and comprising a first element comprising a first opening, a second opening and fluid communication channel between the first opening and the second opening, the first opening being arranged closer to the top than the second opening, the first opening having a first connection to the first part of the tubular line, and the second opening having a second connection to the second part of the tubular line, wherein the first element has a first outer shape in a first state in which the fluid communication channel is open and a second outer shape in a second state in which the fluid communication channel is closed, the second shape being at least partly different from the first outer shape. The invention also relates to a downhole system comprising a well tubular metal structure having an outer face, and the downhole assembly being connected to the outer face and/or the downhole annular barrier. Finally, the invention relates to a method of permanently closing fluid communication in the downhole assembly for permanently sealing off a control line prior to plug and abandonment of a well.