AU2004295689A1

AU2004295689A1 - Flat and bevel chipbreaker insert

Info

Publication number: AU2004295689A1
Application number: AU2004295689A
Authority: AU
Inventors: Francine A. Bradford; Daniel R. Hart; Calvin J. Stowe
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 2003-11-26
Filing date: 2004-11-18
Publication date: 2005-06-16
Also published as: US20050109546A1; GB2424019A; GB2424019B; GB0611242D0; NO20062558L; CN1946916A; WO2005054621A1; RU2006122639A; CA2546938A1

Description

WO 2005/054621 PCT/US2004/038712 Flat and Bevel Chipbreaker Insert BACKGROUND OF THE INVENTION Field of the Invention - This invention is in the field of tools used downhole, in oil or gas wells, to mill or otherwise cut metal objects in the borehole. Background Art - In the drilling, completion, or re-work of an oil or gas well, it often becomes necessary to cut into or through a metal object which is located downhole in the well bore. This can be required, for instance, in cutting through the wall of a well casing, removing a packer, or milling away some other metal obstruction which may be present in the borehole. This type of cutting or milling operation is very different from the type of metal cutting operations typically found in a machine shop environment. The downhole metal cutting operation involves the rotation of a very large tool by a very heavy workstring, by comparison with the typical machine shop operation. The downhole cutting operation itself involves a great deal of vibration and even severe impact, between the cutting tool and the metal object being cut. In fact, much of the force of any such impact or vibration is typically brought to bear directly on the cutting insert or inserts which are mounted on the cutting face of the downhole cutting tool. These cutting inserts are essentially the "teeth" of the cutting tool. They are typically made of a very hard material, such as tungsten carbide. The operator can not closely observe the downhole cutting operation and monitor the condition of the cutting insert or inserts. By contrast, the machine shop operator can closely observe the cutting operation as it progresses, and he can change the cutting insert regularly as its cutting surfaces degrade. Stopping the operation in the machine shop is typically significantly cheaper than pulling a downhole tool from the well bore and checking or changing the tool out. This means that the typical machine shop operation is always done with a basically fresh cutting insert in good condition. The downhole operator, on the other hand, must simply rotate the workstring and rely upon fairly remote indicators of the performance of the tool, such as vibration and rate of penetration, to judge the progress of the cutting operation. As a result, as the cutting operation continues, the cutting insert on the face of the cutting tool 1 WO 2005/054621 PCT/US2004/038712 usually wears away and disintegrates. It is comnlon, in fact, to have multiple cutting inserts on a downhole cutting tool, with the inserts being arranged progressively across the cutting face of the tool. This is done so that, as each cutting insert wears away and disintegrates or falls off the tool, another adjacent cutting insert establishes contact with the work piece, thereby continuing the cutting action. This alleviates the need to pull the work string and replace the tool, or at least delays the necessity of replacing the tool. An unfortunate aspect of this situation is that each cutting insert must remain effective in spite of having its original cutting geometry drastically changed as the cutting operation progresses; that is, the insert will not retain its original cutting edge for very long. If the cutting insert wears to such an extent that the cutting edge is gone, the portion of the insert contacting the work piece can act as a bearing surface. If the cutting insert can not cut effectively after having its original cutting edge worn away, the insert will not be an effective part of the tool, and it can even impede the action of nearby cutting inserts, by acting as a bearing surface, rather than as a cutting surface. It is also known to provide a chip breaking feature on the forward face of a cutting insert for use in the downhole environment, which causes the insert to break off metal chips from the work piece at short lengths, allowing the chips to be more easily removed from the well bore by the flow of drilling fluid. So, as wear progresses across the insert face, through the chip breaking feature, the insert might cease to break off short chips and begin to produce long, thin metal turnings. The long thin turnings are not easily removed from the well bore by the flow of fluid, so this type of insert wear can lead to the clogging of the area around the cutting tool, preventing further penetration of the work piece. Further, if the chip breaking feature contributes in any way to the fragility of the insert body, it can cause the insert to disintegrate prematurely and fall off the cutting tool, resulting in a complete loss of the ability to cut, until the tool body wears sufficiently to allow the adjacent cutting insert to come into play. It is desirable to have, therefore, a cutting insert which is sufficiently robust to withstand the impacts experienced in the downhole environment, and which is designed to break off short metal chips from the work piece, and to continue to 2 WO 2005/054621 PCT/US2004/038712 present an effective cutting geometry to the work piece, even as the original cutting geometry of the insert gradually wears away. BRIEF SUMMARY OF THE INVENTION The present invention, in summary, is a downhole cutting insert which has one or more lands on its cutting face, interspersed with one or more beveled surfaces, creating a robust cutting face on the insert. The juxtaposition of bevels with lands causes the insert to break off metal chips from the work piece at short lengths, allowing the chips to be more easily removed from the well bore by the flow of drilling fluid. Use of alternating multiple bevels and lands allows the insert to continue to effectively form short metal chips, even as the forward face and the edge of the insert gradually degrade. The novel features of this invention, as well as the invention itself, will be best understood from the attached drawings, taken along with the following description, in which similar reference characters refer to similar parts, and in which: BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Figure 1 is an elevation view of a downhole cutting tool which can incorporate a cutting insert according to the present invention; Figure 2 is a top or front elevation view of a first embodiment of a cutting insert according to the present invention; Figure 3 is a top or front elevation view of a second embodiment of a cutting insert according to the present invention; Figure 4 is a partial axial section view of a third embodiment of a cutting insert according to the present invention; Figure 5 is a partial axial section view of a.fourth embodiment of a cutting insert according to the present invention; Figure 6 is a partial axial section view of the cutting insert shown in Figure 2 or Figure 3; and Figure 7 is a partial axial section view of a fifth embodiment of a cutting insert according to the present invention. 3 WO 2005/054621 PCT/US2004/038712 DETAILED DESCRIPTION OF THE INVENTION As illustrated in Figure 1, a cutting insert according to the present invention can be mounted on a cutting tool 10 designed for use in cutting metal objects downhole, in an oil or gas well. The cutting tool 10 can be a pilot mill, junk mill, casing cutter, window mill, or any other type of downhole cutting tool. The cutting tool 10 has a tool body 12, which is adapted to mount to a work string WS. The tool body 12 has at least one cutting feature, such as the blades 14, attached thereto or formed thereon. Each cutting feature or blade 14 has at least one cutting insert 20 mounted on a cutting face 16 thereof, and oriented to face in the direction 18 in which the blades 14 and the cutting inserts 20 will advance when the cutting tool 10 is rotated. Advancement in the direction 18 will cause the cutting inserts 20 to advance toward and into the downhole metal object or work piece (not shown). The cutting inserts 20 can take various shapes, some of which will be designated as 20, 20A and 20B in the Figures discussed below. Other shapes can also be used without departing from the spirit of the present invention, as long as they exhibit the features described below. Figure 2 shows the forward or front elevation of a round or cylindrical cutting insert 20A, oriented in the drawing the same as the orientation of the cutting inserts 20 on the right hand blade 14 in Figure 1. Where a round or cylindrical insert is discussed herein, it should be understood that a half round or otherwise partially round insert can also be intended, where the context allows. The cutting insert 20A has at least one land 22A and at least one bevel or beveled surface 24A, with a first land 22A being located immediately next to the original leading edge 28A of the cutting insert 20A. Where present, successive lands 22A and bevels 24A are alternatingly arranged from the leading edge 28A toward the axis A of the cutting insert 20A. The cutting insert 20A is shown with three lands 22A and three bevels 24A, but it can have any number of each. The cutting insert 20A can also have a surface 26A substantially orthogonal to the axis A, on the front face of the insert 20A. As illustrated in Figure 3, the cutting insert 20 can also have a rectilinear shaped body, such as the insert 20B. The cutting insert 20B is shown oriented in the drawing the same as the orientation of the cutting inserts 20 on the right hand blade 14 4 WO 2005/054621 PCT/US2004/038712 in Figure 1. Where a rectilinear insert is discussed herein, it should be understood that a square or otherwise rectangular insert can be intended. The cutting insert 20B has at least one land 22B and at least one bevel or beveled surface 24B, with a first land 22B being located immediately next to the original leading edge 28B of the cutting insert 20B. Where present, successive lands 22B and bevels 24B are alternatingly arranged from the leading edge 28B toward the axis of the cutting insert 20B. The cutting insert 20B is shown with three lands 22B and three bevels 24B, but it can have any number of each. The cutting insert 20B3 can also have a surface 26B substantially orthogonal to the axis, on the front face of the insert 20B. Figure 4 shows the most basic illustration of the features of the lands 22 and bevels 24 on the inserts 20 shown in Figures 2 and 3, or on any insert 20 according to the present invention. The insert 20 has a solid body. Each land 22 is a substantially flat surface which is substantially orthogonal to the axis of the cutting insert 20. Each land can be, more specifically, angled between approximately 75 degrees and approximately 90 degrees relative to the insert axis. It can be seen that, on the round insert 20A shown in Figure 2, the land 22A would be a substantially planar, annular, surface, substantially or nearly orthogonal to the axis of the cutting insert 20A. It can further be seen that, on the rectilinear insert 20B shown in Figure 3, the land 22B would be a substantially planar, rectangular or otherwise rectilinear, surface, substantially or nearly orthogonal to the axis of the cutting insert 20B. Each bevel 24 is angled forward, or in the direction 18 of rotation, above or forward of the outwardly adjacent land 22 by a distance 32, at an angle 34 from a plane orthogonal to the axis of the cutting insert 20. The angle 34 can be between approximately 20 degrees and approximately 70 degrees, with a preferred angle of approximately 45 degrees. Put another way, the bevel 24 is also angled relative to the axis of the cutting insert 20, by an angle between approximately 20 degrees and approximately 70 degrees, with a preferred angle of approximately 45 degrees. A representative raised distance 32 could be on the order of approximately 0.015 inch. It can be seen that, on the round insert 20A shown in Figure 2, the bevel 24A would be a substantially frusto-conical surface, angled relative to the axis of the cutting insert 20A. It can further be seen that, on the rectilinear insert 20B shown in Figure 3, the bevel 24B would be a substantially planar, rectangular or otherwise rectilinear, 5 WO 2005/054621 PCT/US2004/038712 surface, angled relative to the axis of the cutting insert 20B. The cutting insert 20 can also have a relief angle 36 between approximately 3 degrees and approximately 9 degrees, which promotes the cutting action of the edge 28 into the work piece. A rear face 40 is provided for mounting the cutting insert 20 on the cutting feature or blade 14 of the cutting tool 10. The distance 32 by which each bevel 24 rises above its outwardly adjacent land 22 terminates the bevel 24 either in the surface 26 or in an inwardly adjacent land 22, as shown in Figure 5, in which the cutting insert 20 has two lands 22 and two bevels 24. This embodiment has been found to be somewhat more robust in resisting impact than the single land, single bevel embodiment shown in Figure 4. As shown in Figure 6, the cutting insert 20 can have three sets of lands 22 and bevels 24, or even more. Each land can be relatively narrow, for example, in the range of approximately 0.004 inch to approximately 0.060 inch. As shown in Figure 7, the cutting insert 20 can also have other features on its leading face 26, such as a depression 38. While the particular invention as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages hereinbefore stated, it is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims. 6

Claims

1. A metal cutting insert for use on a downhole tool in an oil or gas well, said insert comprising: a solid body, said body having an axis; a rear face on said body, for mounting said body to a downhole type metal cutting tool; a front face on said body, opposite said rear face, for presentation to a downhole metal object to be cut; a plurality of lands formed on said front face of said body, each said land being substantially orthogonal to said axis of said body; and a plurality of bevels formed on said front face of said body, each said bevel being angled relative to said axis of said body, forward of an adjacent said land.

2. The metal cutting insert recited in claim 1, wherein each said land is angled no less than 75 degrees relative to said axis of said body.

3. The metal cutting insert recited in claim 1, wherein each said bevel is angled between 20 degrees and 70 degrees relative to said axis of said body.

4. The metal cutting insert recited in claim 1, wherein a first said land is formed at an edge of said front face.

5. The metal cutting insert recited in claim 4, wherein a first said bevel is formed adjacent to said first land.

6. The metal cutting insert recited in claim 5, wherein said plurality of lands and said plurality of bevels are formed at alternating locations across said front face. 7 WO 2005/054621 PCT/US2004/038712

7. The metal cutting insert recited in claim 1, wherein: each said land is a substantially planar rectilinear surface; and each said bevel is a substantially planar rectilinear surface.

8. The metal cutting insert recited in claim 7, wherein said insert body is a substantially rectilinear solid.

9. The metal cutting insert recited in claim 1, wherein: each said land is a substantially planar annular surface; and each said bevel is a substantially frusto-conical surface.

10. The metal cutting insert recited in claim 9, wherein said insert body is substantially cylindrical.

11. A downhole metal cutting tool for gas or oil wells, comprising: a tool body adapted for lowering into an oil or gas well to rotatingly cut a downhole metal object; at least one metal cutting insert for mounting on said downhole tool body, said at least one insert having a solid body with an axis; a front face on said at least one insert body, for presentation to said downhole metal object; at least one land formed on said front face of said at least one insert body, said at least one land being substantially orthogonal to said axis of said at least one insert body; and at least one bevel formed on said front face of said at least one insert body, said at least one bevel being angled above said at least one land, relative to said axis of said at least one insert body. 8 WO 2005/054621 PCT/US2004/038712

12. The downhole metal cutting tool recited in claim 11, further comprising: a plurality of said lands; and a plurality of said bevels; wherein said plurality of lands and said plurality of bevels are formed at alternating locations across said front face of said at least one insert body.

13. The downhole metal cutting tool recited in claim 12, wherein: a first said land is formed at an edge of said front face of said at least one insert body; and a first said bevel is formed adjacent to said first land.

14. The downhole metal cutting tool recited in claim 12, wherein each said land is angled no less than 75 degrees relative to said axis of said at least one insert body.

15. The downhole metal cutting tool recited in claim 12, wherein each said bevel is angled between 20 degrees and 70 degrees relative to said axis of said at least one insert body.

16. The downhole metal cutting tool recited in claim 12, wherein: each said land is a substantially planar rectilinear surface; and each said bevel is a substantially planar rectilinear surface.

17. The downhole metal cutting tool recited in claim 16, wherein said insert body is a substantially rectilinear solid.

18. The downhole metal cutting tool recited in claim 12, wherein: each said land is a substantially planar annular surface; and each said bevel is a substantially frusto-conical surface. 9 WO 2005/054621 PCT/US2004/038712

19. The downhole metal cutting tool recited in claim 18, wherein said insert body is substantially cylindrical. 10