Section Mill and Window Cutting for Reliable Wellbore Sealing
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Solution Overview
Problem
Existing methods for plugging and abandoning wellbores fail to provide a satisfactory seal due to leakage through voids and cracks in cement, especially when multiple casing strings are present, risking environmental contamination.
Innovation Solution
A milling system with radial cutout and window mills and section mills is used to cut and remove casing strings, employing pistons to extend and retract arms with ceramic or super-hard material cutters for precise cutting and stabilization, forming windows and sections in the casing to facilitate a secure plug and abandonment process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement plugs are used to seal the wellbore with multiple casing strings, then the wellbore can be abandoned, but leakage occurs through voids and cracks in the cement
Solution Approach 1:
The patent removes casing strings from the wellbore using a milling system with cutting arms that rotate to cut and extract casing sections. By taking out the casing strings that create complex geometries and voids, the patent eliminates the root cause of cement leakage pathways, allowing for a more reliable seal.
Solution Approach 2:
The patent performs preliminary milling and removal of casing strings before setting the cement plug. This preliminary action creates a simplified wellbore geometry without casing obstructions, ensuring that the subsequent cement plug can be set without voids and cracks that would otherwise form around casing strings.
2Stability of the object's composition
If casing strings are left in place during abandonment, then the wellbore structure is maintained, but complete sealing cannot be achieved due to voids and cracks
Solution Approach 1:
The patent extracts casing strings from the wellbore using a milling system that cuts and removes casing sections. This extraction eliminates the structural elements that create voids and cracks, prioritizing seal quality over maintaining the original wellbore structure during abandonment.
Solution Approach 2:
The patent performs preliminary removal of casing strings before setting the final cement plug. This preliminary action ensures that the wellbore is prepared in advance to receive a continuous, void-free cement seal, rather than attempting to seal around existing casing structures.
3Ease of manufacture
If traditional perforation and cement squeezing methods are used, then the process is simple, but satisfactory sealing is not achieved
Solution Approach 1:
The patent replaces the traditional mechanical perforation and cement squeezing system with a milling system that uses rotating cutting arms to physically remove casing strings. This substitution creates a more reliable seal by eliminating the source of voids and cracks, even though the process becomes more complex.
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 system effectively seals the wellbore by ensuring complete removal of casing, reducing leakage and providing a reliable barrier against fluid migration, thus preventing environmental contamination.
Implementation Method 1
The arm may be operated by a piston to move between the retracted position and the extended position
Implementation Method 2
employing pistons to extend and retract arms with ceramic or super-hard material cutters for precise cutting
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
A method for milling a tubular cemented in a wellbore includes deploying a bottomhole assembly (BHA) into the wellbore through the tubular, the BHA comprising a window mill; and extending arms of the window mill and radially cutting through the tubular, thereby forming a window through the tubular, wherein a body portion of each window mill arm engages and stabilizes from an inner surface of the tubular after a blade portion of each window mill arm cuts through the tubular.