Downhole Tool for Cemented Casing Removal
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Solution Overview
Problem
Existing wellbore removal techniques face challenges with aged and corrosive casings that cannot withstand milling loads, and poor cement bonding, limiting the ability to form new lateral or sidetracks in hydrocarbon production wells.
Innovation Solution
A downhole tool system comprising a top sub-assembly, piston sub-assembly, cutting sub-assembly, and hanger sub-assembly, which de-bonds cement layers, cuts through casings, and engages the cut portions with slips to facilitate removal of tubulars from wellbores, utilizing a motor-driven shaft assembly and oscillating pistons to fracture cement and cutting blades to sever the casing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If milling operations are applied to aged and corrosive casings, then new lateral or sidetrack windows can be formed, but the casings cannot withstand the milling load due to their degraded condition
Solution Approach 1:
The removal process is divided into distinct stages: first de-bonding the cement layer from the casing, then cutting the casing, and finally retrieving the cut portion. This segmentation allows each operation to be optimized independently, with the cutting operation occurring after the casing has been weakened by cement removal, thus avoiding the need for high-strength casing during cutting operations.
Solution Approach 2:
The cement layer is de-bonded from the casing before the cutting operation. This preliminary action of removing the cement layer weakens the casing structure and eliminates the need for high milling loads, as the cutting blades can operate more easily on the exposed casing without the full weight and friction of the cement sheath.
2Ease of operation
If cement layer is removed from casing, then cutting operation becomes easier, but the cement layer must be broken or de-bonded first
Solution Approach 1:
The de-bonding and cutting operations are combined into a single integrated tool assembly that performs both functions. The tool includes a de-bonding mechanism with pistons or rollers that contact the cement layer, and a cutting mechanism with blades that cut the casing, all within one tool body that can be deployed and retrieved as a single unit.
Solution Approach 2:
The tool employs dynamic, oscillating pistons or rollers that repeatedly contact the cement layer to progressively de-bond it from the casing. This dynamic action allows the tool to adapt to varying cement bond strengths and progressively work its way through the cement layer, making the de-bonding process more effective and controllable.
3Productivity
If cuts are made through the casing, then the cut portion can be retrieved, but the casing must be weakened or de-bonded first to facilitate cutting
Solution Approach 1:
The cement layer is de-bonded from the casing before the cutting operation begins. This preliminary action removes the protective cement sheath and weakens the casing structure, making it more susceptible to cutting. The cutting blades can then penetrate the casing more easily without requiring excessive force that would risk casing failure.
Solution Approach 2:
The cutting operation is segmented into progressive stages where the tool makes multiple passes or uses multiple blades to gradually cut through the casing. This segmentation allows the cutting process to be controlled and distributed over time, preventing sudden structural failure of the casing while still achieving complete separation.
4Productivity
If multiple operations (de-bonding, cutting, retrieval) are performed, then complete casing removal is achieved, but the tool complexity increases
Solution Approach 1:
The de-bonding mechanism, cutting mechanism, and retrieval mechanism are merged into a single integrated tool assembly. The tool body houses all three subsystems, allowing them to operate in sequence during a single wellbore intervention. This integration eliminates the need for multiple separate tools and multiple wellbore entries, reducing overall operational complexity despite the multiple functions performed.
Solution Approach 2:
The tool is designed as a universal multi-functional device that can de-bond cement, cut casing, and retrieve cut portions all within one tool system. The same tool assembly performs multiple operations that would traditionally require separate specialized tools, thereby reducing the overall complexity of the intervention process despite the sophisticated nature of each individual function.
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
Enables the efficient removal of cemented casings, allowing for new path creation and sidetrack formation by de-bonding cement, cutting through casings, and retrieving the cut sections, addressing issues of aged and corrosive casings and poor cement bonding.
Implementation Method 1
a piston sub-assembly coupled with the top sub-assembly and including a plurality of pistons configured to moveably contact a portion of a casing installed in the wellbore to at least de-bond a portion of a cement layer installed between the portion of the casing and the subterranean formation from the portion of the casing
Implementation Method 2
a cutting sub-assembly coupled with the top sub-assembly and the piston sub-assembly and including at least one cutting blade configured to moveably cut through the portion of the casing adjacent the de-bonded portion of the cement layer
Implementation Method 3
a hanger sub-assembly coupled with the top sub-assembly, the piston sub-assembly, and the cutting sub-assembly and including at least one set of slips moveable to engage the cut portion of the casing
Data Source
AI summary
Techniques for removing a tubular from a wellbore include running a downhole tool on a downhole conveyance into a wellbore formed from a terranean surface into a subterranean formation; activating a piston sub-assembly to repeatedly move pistons to contact a portion of a casing installed in the wellbore to at least de-bond a cement layer installed between the portion of the casing and the subterranean formation from the portion of the casing; activating a cutting sub-assembly to move a cutting blade to cut through the portion of the casing adjacent the de-bonded portion of the cement layer; activating a hanger sub-assembly to move a set of slips into contacting engagement with the cut portion of the casing; and running the downhole tool on the downhole conveyance out of the wellbore with the cut portion of the casing engaged with the set of slips.