Rotary Milling Tool with Leading Cutters for Borehole Tubing
Solution Overview
Problem
Conventional section mills face inaccuracies and vibrations during tubing removal in boreholes due to non-uniform internal diameters caused by corrosion and debris, leading to unstable tool positioning and inefficient cutting.
Innovation Solution
A rotary milling tool with extensible elements featuring leading cutters that expose a renewed internal surface for accurate positioning, followed by further cutters that remove remaining metal and stabilize the cutting process, ensuring precise cutting and reduced vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional section mills use drillstring components to locate the axis relative to tubing, then the tool can be inserted and positioned, but positioning accuracy deteriorates due to non-uniform internal diameters caused by corrosion and debris
Solution Approach 1:
The patent applies preliminary action by using leading cutters to create a renewed, uniform internal surface on the tubing before the guide surfaces engage. This pre-processing step removes corrosion and debris that would otherwise cause positioning inaccuracies, ensuring that when the guide surfaces contact the tubing, they do so against a clean, consistent surface for accurate and stable positioning.
Solution Approach 2:
The patent introduces an intermediary mechanism - the leading cutters - that mediate between the tool's positioning system and the degraded tubing surface. These cutters act as a buffer that prepares the interface between the guide surfaces and tubing, transforming the problematic non-uniform surface into a reliable positioning surface without requiring the guide surfaces themselves to handle the corrosion and debris directly.
2Stability of the object's composition
If the milling tool uses guide surfaces to contact the tubing interior surface, then positioning stability improves, but cutting efficiency deteriorates when the surface is non-uniform due to corrosion and debris
Solution Approach 1:
The patent segments the cutting function into distinct stages: leading cutters that prepare the surface and further cutters that perform the main cutting operation. This segmentation allows the leading cutters to focus solely on creating a uniform surface for stable guide surface contact, while the further cutters handle the bulk material removal, thereby maintaining both positioning stability and cutting efficiency without compromising either function.
3Productivity
If conventional mills cut through tubing with non-uniform internal surfaces, then tubing removal is achieved, but vibrations increase leading to unstable tool positioning and reduced cutting accuracy
Solution Approach 1:
The patent applies preliminary action by having leading cutters create a renewed, uniform internal surface before the main cutting operation. This pre-processing eliminates corrosion and debris that would cause vibrations during cutting, ensuring that when the further cutters remove the tubing, they do so against a clean, consistent surface, thereby reducing vibrations and maintaining stable tool positioning throughout the cutting process.
Data Source
AI summary
Tubing in a borehole is removed using a rotary milling tool comprising a plurality of elements projecting from or extensible from the body of the tool. The elements are distributed azimuthally around the tool body. The elements comprise cutters to remove material from the tubing and outward facing guide surfaces for sliding contact with an inner surface of the tubing. As the tool is rotated and advanced, forward cutters contact the inner surface removing material from the tubing and exposing a renewed interior tubing surface with a diameter swept out by the cutter. The outward facing guide surfaces extend the same distance from the tool body as the forward cutters producing a sliding contact with the newly created inward facing surface. Further cutters, disposed behind the outward facing guide surfaces, with respect to motion of the tool through the tubing, remove the remaining portion of the tubing.