Reverse-Circulation Milling Tool for Downhole Swarf Control
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Solution Overview
Problem
Existing systems fail to effectively prevent swarf from returning to the surface during borehole casing milling, despite attempts to direct it downhole.
Innovation Solution
A milling tool with a blade shifter mandrel biased by a spring and actuated by reverse circulation, utilizing an auger for downhole reverse circulation to disentrain swarf, eliminating the need for a tubular structure and enabling wireline operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional milling systems are used, then casing can be milled, but swarf returns to surface causing environmental and operational issues
Solution Approach 1:
The patent inverts the conventional flow direction by using reverse circulation to push swarf downhole instead of allowing it to return to surface. The system circulates fluid in the opposite direction (downhole rather than uphole) to transport swarf to a designated discharge location below the milling tool, thereby eliminating surface contamination while maintaining operational simplicity through the natural circulation pattern.
Solution Approach 2:
The patent employs hydraulic circulation systems to control swarf transport. By utilizing fluid pressure and flow dynamics in reverse circulation mode, the system effectively moves swarf particles downhole without requiring complex mechanical conveying mechanisms. The hydraulic system leverages pressure differentials and flow velocity to achieve reliable swarf removal while keeping the overall device structure manageable.
2Object-affected harmful factors
If swarf is directed downhole, then surface contamination is reduced, but incomplete swarf removal persists
Solution Approach 1:
The patent incorporates preliminary action by positioning a swarf trap or collection mechanism at the downhole discharge location before swarf arrives. This preliminary preparation ensures that when swarf is transported downhole by reverse circulation, it is immediately captured and contained, preventing any potential escape or incomplete removal. The system proactively prepares the reception point to guarantee complete swarf containment.
Solution Approach 2:
The system implements feedback mechanisms to monitor swarf transport effectiveness. By observing circulation patterns, pressure differentials, and flow characteristics, the system can detect whether swarf is being fully transported downhole. This feedback allows for real-time adjustments to circulation parameters, ensuring reliable and complete swarf removal while maintaining optimal operational conditions.
3Strength
If tubular structure is used for milling, then structural integrity is maintained, but wireline operation capability is lost
Solution Approach 1:
The patent segments the milling tool structure into modular components that can be independently supported and positioned. Rather than relying on a continuous tubular structure, the tool uses discrete structural elements and support mechanisms that can function without a full tubular body. This segmentation enables the tool to be deployed on wireline while maintaining sufficient structural integrity through strategic reinforcement at critical points.
Solution Approach 2:
The patent employs flexible structural elements and thin-walled components that provide sufficient strength and pressure containment without requiring heavy tubular construction. These flexible structures can withstand operational pressures and mechanical loads while maintaining a compact, lightweight design suitable for wireline deployment. The flexible elements allow the tool to bend and flex during retrieval without compromising structural integrity.
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
Prevents swarf from reaching the surface by ensuring all swarf is directed downhole, reducing the need for surface returns and allowing the tool to be run on non-open ID strings.
Implementation Method 1
a piston that in response to reverse circulation moves the shifter mandrel toward the first end to compress the biaser
Implementation Method 2
a biaser disposed at the first end to bias the shifter mandrel toward the second end
Data Source
AI summary
A milling tool, including an outer housing having a first end and a second end, a blade shifter mandrel movably disposed within the outer housing, a biaser disposed at the first end to bias the shifter mandrel toward the second end, a piston that in response to reverse circulation moves the shifter mandrel toward the first end to compress the biaser, and a blade mounted to the outer housing and in operable contact with the blade shifter mandrel. A method for operating a milling tool, the method including running the milling tool to a target location of a borehole, reverse circulating a fluid in the borehole, biasing the piston with the reverse circulating fluid to deploy the blade. A borehole system, including a borehole in a subsurface formation, a string disposed within the borehole, and a milling tool disposed within or as a part of the string.