CUTTER ASSEMBLY

Abstract

There is a cutter assembly for a roller reamer for downhole drilling. The cutter assembly has a first end block and a cutting element having a plurality of cutting projections. The cutting element is rotatably mounted to the first end block. The cutter assembly further has (a) a primary locking assembly having a primary bore in the first end block for screwing in a primary screw to attach the cutter assembly to a reamer body and (b) a secondary locking assembly. The secondary locking assembly has a secondary bore in the first end block having a threaded section and a secondary bolt screwed into the threaded section. The secondary bolt has a head and a threaded portion. The secondary bolt is for unscrewing out such that the head is received in a locking bore of the reamer body to attach the cutter assembly to the reamer body.

Claims

1. A cutter assembly for a roller reamer for downhole drilling, the cutter assembly comprising: a first end block; a cutting element comprising a plurality of cutting projections, wherein the cutting element is rotatably mounted to the first end block; wherein the cutter assembly further comprises: a primary locking assembly comprising a primary bore in the first end block for screwing in a primary screw to attach the cutter assembly to a reamer body; and a secondary locking assembly comprising: a secondary bore in the first end block comprising a threaded section; and a secondary bolt screwed into the threaded section, the secondary bolt comprising a head and a threaded portion, wherein the secondary bolt for unscrewing out such that the head is received in a locking bore of the reamer body to attach the cutter assembly to the reamer body.

2. The cutter assembly of claim 1, further comprising a biasing member arranged to bias the secondary bolt in an unscrewing direction.

3. The cutter assembly of claim 2, wherein the biasing member is a spring arranged in the secondary bore.

4. The cutter assembly of claim 1, wherein the secondary bolt further comprises a radial projection between the head and the threaded portion, wherein the radial projection shoulders against the reamer body to prevent the secondary bolt from unscrewing further.

5. The cutter assembly of claim 1, further comprising a second end block, and wherein the cutting element is rotatably mounted between the first end block and the second end block.

6. The cutter assembly of claim 5, wherein the primary locking assembly further comprises a primary bore in the second end block for screwing in a primary screw to attach the cutter assembly to the reamer body.

7. The cutter assembly of claim 1, wherein each end block is a cutter block comprising a plurality of cutting projections.

8. The cutter assembly of claim 1, wherein the secondary bore comprises a counter-bore section for receiving the head of the secondary bolt screwed into the threaded bore such that the head is flush with an outer surface of the first end block.

9. The cutter assembly of claim 1, wherein the primary bore is transverse to the secondary bore.

10. The drilling assembly of claim 9, wherein the primary bore is perpendicular to the secondary bore.

11. A roller reamer comprising: the cutter assembly of claim 1; a reamer body comprising: a recess for receiving a cutter assembly; a primary receiving bore for receiving the primary screw when it is screwed in to retain the cutter assembly in the recess; and a secondary receiving through bore extending from an outer surface of the reamer body to the recess for receiving the head of the secondary bolt when it is unscrewed out to retain the cutter assembly in the recess.

12. The roller reamer of claim 11, wherein the primary bore is transverse to the secondary bore.

13. The roller reamer of claim 12, wherein the primary bore is perpendicular to the secondary bore.

14. The roller reamer of claim 11, wherein the roller reamer comprises a plurality of cutter assemblies according to claim 1, wherein the reamer body comprises: a plurality of recesses corresponding to the plurality of cutter assemblies; a plurality of primary receiving bores corresponding to the plurality of recesses for receiving the corresponding primary screw when it is screwed in to retain the corresponding cutter assembly in the corresponding recess; and a plurality of secondary receiving through bores corresponding to the plurality of recesses and each extending from an outer surface of the reamer body to the corresponding recess for receiving the head of the corresponding secondary bolt when it is unscrewed out to retain the corresponding cutter assembly in the corresponding recess.

15. The roller reamer of claim 14, wherein the plurality of cutter assemblies are N cutter assemblies and the plurality of recesses are N recesses, and wherein the N recesses are arranged with N-fold rotational symmetry around the reamer body.

16. The roller reamer of claim 15, wherein N is three.

17. A method of assembly a roller reamer comprising the steps of: a. providing a cutter assembly according to claim 1; b. providing a reamer body comprising: a recess for receiving the cutter assembly; a primary receiving bore for receiving the primary screw when it is screwed in to retain the cutter assembly in the recess; and a secondary receiving through bore extending from an outer surface of the reamer body to the recess for receiving the head of the secondary bolt when it is unscrewed out to retain the cutter assembly in the recess, c. inserting the cutter assembly into the recess; d. screwing a primary screw through the primary bore into the primary receiving bore to retain the cutter assembly to the reamer body; and e. unscrewing the secondary bolt until the head is within the secondary receiving through bore.

18. The method of claim 17, further comprising: providing a plurality of cutter assemblies according to claim 1, and wherein the reamer body comprises: a plurality of recesses corresponding to the plurality of cutter assemblies; a plurality of primary receiving bores corresponding to the plurality of recesses for receiving the corresponding primary screw when it is screwed in to retain the corresponding cutter assembly in the corresponding recess; a plurality of secondary receiving through bores and corresponding to the plurality of recesses and each extending from an outer surface of the reamer body to the corresponding recess and for receiving the head of the corresponding secondary bolt when it is unscrewed out to retain the corresponding cutter assembly in the corresponding recess, wherein the method further comprises carrying out steps c, d, and e for each corresponding recess and cutter assembly.

19. The method of claim 18, wherein the plurality of cutter assemblies are N cutter assemblies and the plurality of recesses are N recesses, wherein the N recesses are arranged with N-fold rotational symmetry around the reamer body.

20. The method of claim 19, wherein N is three.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0028] The present specification references, by way of example only, the accompanying drawings in which:

[0029] FIG. 1 shows a perspective view of a cutter assembly;

[0030] FIG. 2 shows a side view of a roller reamer with the cutter assembly of FIG. 1 installed; and

[0031] FIGS. 3A and 3B show cross-sectional views along III of the roller reamer of FIG. 2 showing the screwing and unscrewing of a secondary locking assembly.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0032] A cutter assembly 100 is shown in FIG. 1. This cutter assembly 100 is for use in a roller reamer 200 for downhole drilling, as shown in FIG. 2.

[0033] The cutter assembly 100 includes a first end block 10 and a second end block 10. Between the first and second end blocks 10, a cutting element 12 is rotatably mounted. In some examples, the cutter assembly 100 may comprise only a single end block 10, and the cutting element 12 may be retained between the single end block 10 and a suitable receiving point on the reamer body 20 of the roller reamer 200. This does not substantially alter the operation of the roller reamer 200, and any element that would otherwise be provided in the second end block 10 is instead provided in the reamer body 20.

[0034] The cutting element 12 may be supported between the end blocks 10 by one or more bearing washers 18. These bearing washers 18 allow the cutting element 12 to easily rotate with respect to the end blocks 10. The cutting element 12 contacts the wall of the borehole and friction with the wall causes it to rotate in use to cut the side walls of the borehole. In order to do so, the cutting element 12 includes a plurality of cutting projections 12a. There may also be one or more cutting projections 12a formed on the end blocks 10, as appropriate, making the end blocks 10 into a cutter block.

[0035] The cutter assembly 100 is attached to a reamer body 20 to form a roller reamer 200 as shown in FIG. 2. Particularly, the reamer body 20 may include a recess for receiving this cutter assembly 100. The recess may be generally shaped to conform to outer surfaces of the cutter assembly 100. In particular examples, the reamer body 20 may include a plurality of recesses arranged circumferentially around it. That is, the recesses may each be at the same axial position along the drill string, but spaced circumferentially. The recesses may be equally spaced around the reamer body 20. For example, the reamer body 20 may include three recesses, which are spaced 120? from one another. In general, there may be N recesses, which are arranged with N-fold rotational symmetry. That is, the N recesses may be spaced (360/N?) from one another around the reamer body 20.

[0036] The cutter assembly 100 is primarily attached to the reamer body 20 via a primary locking assembly 14. This primary locking assembly consists of a threaded fastener in the form of a screw or bolt or the like, such as a primary screw, which is screwed into a primary receiving bore in the reamer body 20 to attach the cutter assembly 100 to the reamer body 20. In particular embodiments this may be a socket head cap screw, or any other suitable threaded fastener. For example, the primary locking assembly 14 may comprise a primary bore in the first end block 10 which receives the threaded fastener. The threaded fastener will then protrude out of an opposite surface of the first end block 10 for screwing into the reamer body 20. The primary bore may also itself be threaded, to receive this threaded fastener.

[0037] By screwing into, this means that the corresponding action is taken to drive the threaded fastener in the direction of the screw thread. For example, in a right-handed screw screwing into would mean driving the screw in a clockwise direction. Unscrewing is the opposite action, which drives the threaded fastener in the opposite direction. For example, in a right-handed screw unscrewing out of would mean driving the screw in an anti-clockwise direction.

[0038] With respect to an axial direction defined along the length of the drill pipe, the threaded fastener of the primary locking assembly 14 may be driven in a radial direction towards the centre of the reamer body 20 as it is screwed in.

[0039] A secondary locking assembly 16 is also provided for retaining the cutter assembly 100 to the reamer body 20. A secondary bore is formed in the first end block 10. This secondary bore includes an internal threaded section, into which a secondary bolt 17 is screwed. With the cutter assembly 100 inserted into the recess of the reamer body 20, the secondary bore is aligned with a secondary receiving through bore 22 formed in the reamer body 20.

[0040] The secondary bolt 17 comprises a threaded portion for screwing into and out of the internal threaded section, and a head. The head can be received in the secondary receiving through bore 22 of the reamer body 20 to retain the cutter assembly 100 within the reamer body 20. This is achieved by unscrewing the secondary bolt 17 until the head is received in this secondary receiving through bore 22. The secondary bolt may comprise a radial projection (relative to the direction of unscrewing as an axial direction) between the head and the threaded portion. This radial projection may shoulder against the reamer body 20 to prevent the secondary bolt from unscrewing further.

[0041] By unscrewing, this means that the secondary bolt 17 is progressively extracted from the internal threaded section. In particular examples, the threaded section and secondary receiving through bore 22 may be in a direction which is generally transverse to the radial direction and the axial direction. That is, the direction of unscrewing the secondary bolt 17 may be transverse to the direction of screwing the threaded fastener of the primary locking assembly 14. In particular, this may be generally perpendicular.

[0042] The first end block 10 may include a counter-bore section 34 in the secondary bore. This counter-bore 34 may receive the head of the secondary bolt 17 when the secondary bolt 17 is screwed into the internal thread. In particular, the head of the secondary bolt 17 may be totally received within this counter-bore 34 such that the head is flush with the outer surface of the first end block 10. Of course, the secondary bolt 17 may go further beyond flush into the first end block 10.

[0043] FIG. 3A shows a cross-section along line Ill in FIG. 2. This shows the secondary bolt 17 received within the first end block 10 such that the cutter assembly 100 is ready for insertion into the recess of the reamer body 20. The cutter assembly 100 is inserted into the recess and the threaded fastener of the primary locking assembly 14 is screwed into the reamer body 20 to attach the cutter assembly to the reamer body 20. This insertion aligns the internal threaded section with the secondary receiving through bore 22 of the reamer body 20, the position shown in FIG. 3A.

[0044] Then, the secondary bolt 17 can be unscrewed from the threaded section until the head of the secondary bolt 17 is received within the secondary receiving through bore 22 as shown in FIG. 3B. This thereby further fixes the cutter assembly 100 to the reamer body 20.

[0045] In this sense, the cutter assembly 100 is securely retained within the reamer body 20 to form the roller reamer 200. If the secondary bolt 17 fails for whatever reason, such as shearing or any other damage, it is entirely constrained within the roller reamer 200. This means that it would not cause any further damage to the roller reamer 200 or the drill string even in the event of a catastrophic failure.

[0046] The secondary locking assembly may further comprise a biasing member 32, such as a spring 32, provided within the secondary bore. This may be in the threaded section of the secondary bore, or any other suitable section. The biasing member 32 may bias the secondary bolt 17 in the unscrewing direction. That is, screwing in of the secondary bolt 17 may for example compress the spring 32. Thus, the biasing member 32 forces the secondary bolt 17 towards the fixed position shown in FIG. 3B.

[0047] In arrangements including a first and second end block 10, the second end block 10 may have its own primary locking assembly 14. The second end block 10 may also have its own secondary locking assembly 16. In other examples, the first end block 10 may only have a primary locking assembly 14 and the second end block 10 may only have a secondary locking assembly 16. These locking assemblies would operate in the same manner as described above, with any of the discussed modifications.

[0048] As discussed above, the roller reamer 200 may include a plurality of cutter assemblies 100 installed within the reamer body 20. Each cutter assembly 100 may be installed in the same method as discussed above, with the reamer body 20 including a corresponding plurality of primary receiving bores and secondary receiving through bores 22 as appropriate for the selected cutter assemblies 100.

[0049] A method of assembly a roller reamer 200 is disclosed. The method comprises the steps of: (a) providing a cutter assembly 100 as discussed above, and (b) a reamer body 20 as discussed above. The cutter assembly 100 may be (c) inserted into the recess of the reamer body 20. A primary screw is then (d) screwed through the primary bore into the primary receiving bore of the reamer body 20 to retain the cutter assembly 100 to the reamer body 20. Finally, the secondary bolt 17 is (e) unscrewed until the head is within the secondary receiving through bore 22.

[0050] If the reamer body 20 includes a plurality of recesses as discussed above, the method may further comprises: providing a plurality of cutter assemblies 100 as discussed above. Steps c, d, and e can then be carried out for each corresponding recess and cutter assembly 100.

[0051] For example, the reamer body 20 may include N recesses which receive N cutter assemblies 100. If the N cutter assemblies include two end blocks 10, a primary locking assembly in each end block 10, and a secondary locking assembly only in the first end block 10, there will be a corresponding primary receiving bore for each primary locking assembly and a corresponding secondary receiving through bore for each secondary locking assembly. That is, 2N primary receiving bores and N secondary receiving through bores formed in the reamer body 20. This is a typical arrangement, and in this typical arrangement N may be 3.