AU2022203456B2

AU2022203456B2 - Drill Bit

Info

Publication number: AU2022203456B2
Application number: AU2022203456A
Authority: AU
Inventors: Graeme Michel Adriaens; Paul Wolfgang Kalisch
Original assignee: Wallis Eng Pty Ltd
Current assignee: Wallis Engineers Pty Ltd
Priority date: 2015-11-27
Filing date: 2022-05-20
Publication date: 2024-06-13
Anticipated expiration: 2036-11-28
Also published as: AU2022203456A1; AU2016265977A1; AU2024219726A1

Abstract

A drill bit comprises a tubular body, a first end of the tubular body configured to be coupled to the lower end of a drill string; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body; and a return located on an outer wall of the tubular body proximal to the plurality of polycrystalline diamond cutting surfaces. In use, a fluid flowing through a passage formed between an inner wall and the outer wall is directed into the hollow space of the tubular body and substantially towards the first end of the tubular body by the return. A drill string comprising the drill bit and a method of using the drill bit are also disclosed.

Description

Drill Bit

Field of the Invention

[0001] The present invention relates to a drill bit for sub-surface drilling.

Background

[0002] Sub-surface drilling is used in exploration to probe sub-surface features of interest by extracting samples of the sub-surface rock, such as in exploration for potential mine sites. The extracted samples are analysed to determine the mineralogical, petrological and structural properties of the sub-surface rock to determine whether the potential mine site contains commercially viable ore deposits. In order to extract the samples, a drilling rig is used to bore a hole through the sub-surface rock in a manner that produces rock chips or cored rock.

[0003] Air core drilling is a technique used to extract sub-surface rock samples consisting of rock chips and small chunks of cored rock. The technique uses an air core drill bit that is attached to the end of a drill string. The air core drill bit typically comprises a tubular body and an inner tube that sits inside the hollow space of the tubular body. The drill bit further comprises cutting blades arranged around the drill bit head that are typically made of hardened steel or tungsten carbide. The samples are removed by the injection of compressed air through an annular space, defined by the space between the outer wall of the inner tube and the inner wall of the tubular body, which enters the hollow space of the inner tube through an annular opening. The force of the compressed air causes debris from the action of the drill bit head to be blown back to the surface up through the inner tube as the sample. This provides the benefit that the extracted samples are free from contaminants that other mineral exploration drilling techniques create. However, a substantial disadvantage of the air core drilling technique is that the cutting blades are only suitable for boring through relatively soft, unconsolidated or weathered ground.

[0004] It is also known in the mining industry that a drill bit utilising diamond for a plurality of cutting surfaces is ideal for boring through hard solid rock. Each cutting surface is typically comprised of industrial diamonds set in a softer metallic matrix. During use of the drill bit, the cutting surfaces are designed such that the softer metallic matrix is worn away to expose more diamonds and ensure that the cutting action continues. Unfortunately, friction created by the use of the drill bit generates heat which in turn accelerates the accumulation of damage caused by wear of the cutting surfaces. In order to address the heat generation, water injected through the drill string is used to cool the drill bit in addition to removing drill cuttings by flushing the cuttings to the surface through the gap between the outer wall of the drill bit and the walls of the bored hole. This produces the disadvantage of water washing material from the walls of the bored hole and contaminating the sub-surface rock samples used.

[0005] The present invention seeks to overcome, or at least substantially ameliorate, the disadvantages and/or shortcomings of the background art.

[0006] In this specification the terms "comprising" or "comprises" are used inclusively and not exclusively or exhaustively.

[0007] Any references to documents that are made in this specification are not intended to be an admission that the information contained in those documents form part of the common general knowledge known to a person skilled in the field of the invention, unless explicitly stated as such.

Summary of the Invention

[0008] According to an aspect of the invention, there is provided a drill bit comprising: a tubular body, a first end of the tubular body configured to be coupled to the lower end of a drill string; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body; a return located on an outer wall of the tubular body proximal to the plurality of polycrystalline diamond cutting surfaces, whereby in use a fluid flowing through a passage formed between an inner wall and the outer wall is directed into the hollow space of the tubular body and substantially towards the first end of the tubular body by the return.

[0009] In an embodiment of the invention, each of the plurality of polycrystalline diamond cutting surfaces is in the form of a cylindrical insert. In an embodiment of the invention, at least one of the plurality of polycrystalline diamond cutting surfaces is in the form of a cylindrical insert. In an embodiment of the invention, at least one of the plurality of polycrystalline diamond cutting surfaces is in the form of a half-cylindrical insert.

[0010] In an embodiment of the invention, the cylindrical insert is replaceable.

[0011] In an embodiment of the invention, the cylindrical insert comprises at least one layer of the plurality of polycrystalline diamonds is bonded to a carbide core.

[0012] In an embodiment of the invention, the drill bit further comprises one or more ports configured to direct the fluid to the plurality of polycrystalline diamond cutting surfaces.

[0013] In an embodiment of the invention, a secondary fluid is introduced with the fluid to the passage.

[0014] According to a second aspect of the invention, there is provided a drill string comprising the drill bit as defined above.

[0015] According to a third aspect of the invention, there is provided a drill string comprising: a tubular body, a first end of the tubular body configured to be coupled to further drill string members; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body; a passage located between an inner wall and an outer wall of the tubular body; wherein the passage terminates at an opening in the inner wall of the tubular body so as to be proximal to the plurality of polycrystalline diamond cutting surfaces, whereby in use a fluid flowing through the passage is directed into the hollow space of the tubular body and substantially towards the first end of the tubular body by the opening.

[0016] According to a fourth aspect of the invention, there is provided a method of drilling comprising: providing a drill bit with a tubular body, and a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body at a lower end of a drill string; engaging the drill bit in a drilling operation; directing a fluid through a passage located between an inner wall and an outer wall of the tubular body and out of an opening in the inner wall of the tubular body so as to be proximal to the plurality of polycrystalline diamond cutting surfaces, whereby in use the fluid flowing through the passage is directed into the hollow space of the tubular body and substantially towards a first end of the tubular body by the opening. The allows the fluid flowing through the passage towards the first end to carry drilled debris towards the first end during drilling operation.

[0017] In an embodiment of the invention, the fluid flow from the opening assists in the dissipation of heat created at the plurality of polycrystalline diamond cutting surfaces.

[0018] In an embodiment of the invention, fluid flow from the opening encourages material cut by the plurality of polycrystalline diamond cutting surfaces to be entrained and carried through the hollow space of the tubular body.

[0019] In an embodiment the method further comprises introducing a second fluid into the passage.

[0020] In an embodiment the first fluid is air. In an embodiment the second fluid is water. In an embodiment the method further comprises controlling the ratio of first fluid to second fluid.

[0021] In an embodiment the ratio is controlled according to the water content of the returned fluid from the first tubular body.

[0022] In an embodiment the ratio is controlled according to the water content obtained from the ground penetrated in the drilling operation.

[0023] Also according to the present invention there is provided a drill bit capable of being coupled to a double walled tubular drill rod of a drill string having an inner wall and an outer wall spaced from the inner wall, the space between the inner and outer walls for allowing a fluid to travel therethrough towards the drill bit, the drill bit comprising: a tubular body, a first end of the tubular body configured to be coupled to a lower end of the drill string; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around an opening to a hollow space of the tubular body, the hollow space arranged to lead to an inside of the inner wall of the drill rod when the drill bit is coupled to the drill rod; at least one port in the tubular body for directing fluid onto the polycrystalline diamond cutting surfaces, the fluid then able to enter the opening to the hollow space while carrying cuttings created by operation of the polycrystalline cutting surfaces, the port arranged to receive fluid from the space between the inner and outer walls when the drill bit is coupled to the drill rod; a return located on an inner surface of the an outer wall of the tubular body adjacent to an end of the inner wall of the drill rod when the drill bit is coupled to the drill rod, the return being proximal to the plurality of polycrystalline diamond cutting surfaces, the return configured to direct fluid to flow through a passage formed between the inner surface of the outer wall of the tubular body and the inner wall of the drill rod when the drill bit is coupled to the drill rod, the fluid flow being directed into the inside of the inner wall of the drill rod and substantially towards the first end of the tubular body by the return.

[0024] Further according to the present invention there is provided a drill string comprising: a double walled tubular drill rod having an inner wall and an outer wall spaced from the inner wall, the space between the inner and outer walls for allowing a fluid to travel therethrough towards the drill bit; a drill bit coupled to the drill rod, the drill bit comprising: a tubular body, a first end of the tubular body configured to be coupled to further drill string members; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around an opening to a hollow space of the tubular body, the hollow space arranged to lead to an inside of the inner wall; at least one port in the tubular body for directing fluid onto the polycrystalline diamond cutting surfaces, the fluid then able to enter the opening to the hollow space while carrying cuttings, the port arranged to receive fluid from the space between the inner and outer walls; a passage located between an inner wall tubular body and the outer wall of the drill rod; a return located on an inner surface of the hollow space of the tubular body adjacent to an end of the inner wall of the drill rod, the return being proximal to the plurality of polycrystalline diamond cutting surfaces, the return configured to direct fluid to flow through the passage, wherein a fluid flowing through the passage is directed into the inside of the inner wall and substantially towards the further drill string member by the return.

[0025] Still further according to the present invention there is provided a method of drilling comprising: providing a drill bit with a tubular body, and a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body at a lower end of a drill string; engaging the drill bit in a drilling operation; directing fluid through at least one port in the tubular body onto the polycrystalline diamond cutting surfaces, the fluid then entering an opening to the hollow space while carrying cuttings; directing a fluid through a passage located between an outer wall and an inner wall of the tubular body proximal to the plurality of polycrystalline diamond cutting surfaces, the fluid flowing through the passage being directed into the hollow space of the tubular body and substantially towards a first end of the tubular body by the opening.

Description of Drawings

[0026] In order to provide a better understanding, embodiments of the present invention will be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an end view of a first drill bit; Figure 2 is a cross sectioned view of the drill bit of Figure 1; Figure 3 is an end view of a second drill bit; Figure 4 is a cross sectioned view of the drill bit of Figure 3; Figure 5 is an end view of a third drill bit; Figure 6 is a cross sectioned view of the drill bit of Figure 5; Figure 7 is an end view of a fourth drill bit; Figure 8 is a cross sectioned view of the drill bit of Figure 7; Figure 9 is an end view of a fifth drill bit; Figure 10 is a cross sectioned view of the drill bit of Figure 9; Figure 11 is an end view of a sixth drill bit; Figure 12 is a cross sectioned view of the drill bit of Figure 11; Figure 13 is an end view of a seventh drill bit; and Figure 14 is a cross sectioned view of the drill bit of Figure 13.

Detailed Description

[0027] Figures 1 and 2 illustrate a drill bit 10 used in a drill rig suitable for air core drilling according to a preferred embodiment of the invention. The drill bit 10 comprises a tubular body 12 having a first end 14 in the form of a tubular wall 25 configured to be fitted to an outer tube 26 of an end of a drill string 11. The drill string 11 further comprises an inner tube 24. In an example, a portion 27 of the wall 25 is threaded so that it can be screwed into a complementary threaded lower end of the outer wall 26 of the drill string 11. Other types of coupling/fitting are possible, such as splines or a grub screw(s). A second end 16 of the tubular body 12 has a plurality of polycrystalline diamond cutting surfaces 18 arranged around a hollow space 20 of the tubular body 12. Polycrystalline diamond includes diamond crystals bonded together under high temperature and pressure, which can then be fused/bonded to a substrate. The tubular wall 25 is capable of defining a passage between a central opening 30 and another wall inside the hollow space 20. The inner wall 24 of the drill string 11 can provide the other wall such that a passage 22 is located between the inner wall 24 and an outer wall 25 of the tubular body 12. Due to the outer wall 25 coupling with the outer wall 26, the passage 22 continues as indicated by 22' up the drill string 11 between the inner wall 24 and the outer wall 26. The passage 22 leads to and terminates at an opening 28 in the inner wall 24 so as to be proximal to the plurality of polycrystalline diamond cutting surfaces 18. The wall 25 has a generally U shaped return 32 on its inner surface just past the opening 28. During use of the drill bit 10, a fluid, such as in the form of compressed air, flowing through the passage is directed by the return 32 into the hollow space 20 of the tubular body 12 and substantially towards the first end 14 of the tubular body 12 by the opening 28. The first end 14 of the inner tube 24 is provided with the central opening 30 in which drilled samples (such as a cored sub surface rock (not shown) or rock chips) may be retrieved into the hollow space 20 of the tubular body 12.

[0028] In an embodiment, the tubular body 12 is comprised of only the outer wall 25. In an alternative embodiment the inner tube 24 ends in the drill string 11, short of the drill bit 10. Instead the inner tube 24 is connected to a core tube, separate from the tubular body 12, which forms the left-hand end portion of the inner tube as drawn in Figure 2. The core tube is positioned within the lower end of the drill string 11, so that its lower end projects into the first end 14 of the tubular body 12 and terminates above the recess 32. The core tube then acts as the end portion of the inner wall 24 to form the passage 22. This arrangement provides the advantage of assisting with the retrieval of cored rock samples.

[0029] Each of the plurality of polycrystalline diamond cutting surfaces 18, shown in Figure 1, are mounted on a pair of members 34a, 34b and are in the form of a substantially cylindrical respective inserts 36a and 36b (generally 36 when singular). The inserts 36a, 36b are arranged side-by-side and in spaced positions on the second end 16 of the tubular body 12 so that they project downwardly in order to cut the presented rock face (not shown). This provides the advantage that each of the substantially cylindrical inserts 36a, 36b may be removed from the members 34a, 34b for replacement once worn down to an ineffective state.

[0030] It would be appreciated by those skilled in the art that the configuration of the plurality of polycrystalline diamond cutting surfaces 18 may be of any shape, size or form as shown in examples depicted by Figures 3 to 14. The configurations are dependent upon the properties of the sub-surface rock that is being targeted for cutting and/or the desired cutting regime.

[0031] In an example, the plurality of polycrystalline diamond cutting surfaces 18 may comprise a large cylindrical insert 36 mounted on a single member 34, as shown in Figures 9 and 10, in order to provide a larger cutting area. In another example, the plurality of polycrystalline diamond cutting surfaces 18 may comprise of a pair of members 34a, 34b wherein one of the members 34b is presented at an angle in order to provide a tapered cutting area such as is shown in Figures 13 and 14.

[0032] In an embodiment, each of the cylindrical inserts 36 comprises at least one layer of the plurality of polycrystalline diamonds bonded to a carbide core.

[0033] In an embodiment, the drill bit 10 further comprises a one or more ports 40 configured to direct the compressed air to the plurality of polycrystalline diamond cutting surfaces 18. This provides the advantage of providing an avenue of direct cooling to the plurality of cutting surfaces 18.

[0034] In an embodiment, a secondary fluid, for example water, is introduced with the compressed air to the passage 22. This provides the advantage of providing a potent source of heat dissipation through the use of a superior heat transfer medium. It would be appreciated by those skilled in the art that the secondary fluid may be controllably introduced with the compressed air.

[0035] It will also be apparent to the person skilled in the art that ground water may also assist in cooling the cutting surfaces 18.

[0036] It can be seen that the embodiment shown in Figures 3 and 4 has two cutting surfaces that orbit the centre of rotation of the drill bit at a lesser radius than another two opposed cutting surfaces.

[0037] It can be seen that the embodiment shown in Figures 5 and 6 has two sets of two smaller cutting surfaces and one larger cutting surface that orbit the centre of rotation of the drill bit.

[0038] It can be seen that the embodiment shown in Figures 7 and 8 has a plurality of sizes and orbital radius of the cutting surfaces, and that every other cutting surface is a half cylindrical insert 36'. It can also be seen that the embodiment of Figures 9 and 10 has another arrangement of three relatively larger cutting surfaces.

[0039] It can be seen that the embodiment shown in Figures 11 and 12 has two sets of leading cutting surfaces and one trailing cutting surface that orbit the centre of rotation of the drill bit.

[0040] The method of operation and use of the drill bit 10 used in a drill rig suitable for air core drilling will now be described in more detail.

[0041] The drill bit 10 bores a hole by rotation of the drill bit 10, having a plurality of polycrystalline diamond cutting surfaces 18 arranged around a hollow space 20 of a tubular body 12, at a lower end of a drill string. During use, the plurality of polycrystalline diamond cutting surfaces 18 cut the presented rock face and create rock chips and/or cored rock sample(s) that enter a central core passage 30. A fluid, in the form of compressed air, is directed through a passage 22 located between an inner wall 24 and an outer wall 26 of the tubular body 12. The fluid then exits out of an opening 28 in the inner wall 24 of the tubular body 12 so as to be proximal to the plurality of polycrystalline diamond cutting surfaces 18. During use of the drill bit 10, the fluid flowing through the passage 22 is directed by the return 32 into the hollow space 20 of the tubular body 12 and substantially towards the first end 14 of the tubular body 12, so as to encourage the rock chips and/or cored rock sample to be entrained and carried through the hollow space 20 of the tubular body 12 towards the surface.

[0042] If there is insufficient water content in the returned sample for a given drill rate for a given hardness of ground being drilled, the amount of water introduced as a secondary fluid is controlled. For example if the water content of the returned flow is too low, water can be added. If the amount of returned water is too high, less water is added. If the rock is particularly hard (and thus the amount of friction increased) - determined by the rate of return and or the power applied to rotate the drill string, the amount of water may be increased. If the hardness decreases the amount of water added may be decreased.

[0043] In an embodiment of the invention, the fluid flow from the opening 28 assists in the dissipation of heat created at the plurality of polycrystalline diamond cutting surfaces 18.

[0044] Modifications may be made to the present invention within the context of that described and shown in the drawings. Such modifications are intended to form part of the invention described in this specification.

Claims

1. A drill bit capable of being coupled to a double walled tubular drill rod of a drill string having an inner wall and an outer wall spaced from the inner wall, the space between the inner and outer walls for allowing a fluid to travel therethrough towards the drill bit, the drill bit comprising: a tubular body, a first end of the tubular body configured to be coupled to a lower end of the drill string; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around an opening to a hollow space of the tubular body, the hollow space arranged to lead to an inside of the inner wall of the drill rod when the drill bit is coupled to the drill rod; at least one port in the tubular body for directing fluid onto the polycrystalline diamond cutting surfaces, the fluid then able to enter the opening to the hollow space while carrying cuttings created by operation of the polycrystalline cutting surfaces, the port arranged to receive fluid from the space between the inner and outer walls when the drill bit is coupled to the drill rod; a return located on an inner surface of the an outer wall of the tubular body adjacent to an end of the inner wall of the drill rod when the drill bit is coupled to the drill rod, the return being proximal to the plurality of polycrystalline diamond cutting surfaces, the return configured to direct fluid to flow through a passage formed between the inner surface of the outer wall of the tubular body and the inner wall of the drill rod when the drill bit is coupled to the drill rod, the fluid flow being directed into the inside of the inner wall of the drill rod and substantially towards the first end of the tubular body by the return.

2. A drill bit according to claim 1, wherein at least one of the plurality of polycrystalline diamond cutting surfaces is in the form of a cylindrical insert.

3. A drill bit according to claim 1, wherein at least one of the plurality of polycrystalline diamond cutting surfaces is in the form of a half-cylindrical insert.

4. A drill bit according to claim 2 or 3, wherein at least one of the inserts is replaceable.

5. A drill bit according to any one of claims 1 to 4, wherein the plurality of polycrystalline diamonds are bonded to a carbide core.

6. A drill bit according to any one of claims 1 to 5, wherein a secondary fluid is introduced with the fluid to the passage.

7. A drill string comprising the drill bit according to any one of claims 1 to 6.

8. A drill string comprising: a double walled tubular drill rod having an inner wall and an outer wall spaced from the inner wall, the space between the inner and outer walls for allowing a fluid to travel therethrough towards the drill bit; a drill bit coupled to the drill rod, the drill bit comprising: a tubular body, a first end of the tubular body configured to be coupled to further drill string members; a second end of the tubular body having a plurality of polycrystalline diamond cutting surfaces arranged around an opening to a hollow space of the tubular body, the hollow space arranged to lead to an inside of the inner wall; at least one port in the tubular body for directing fluid onto the polycrystalline diamond cutting surfaces, the fluid then able to enter the opening to the hollow space while carrying cuttings, the port arranged to receive fluid from the space between the inner and outer walls; a passage located between an inner wall tubular body and the outer wall of the drill rod; a return located on an inner surface of the hollow space of the tubular body adjacent to an end of the inner wall of the drill rod, the return being proximal to the plurality of polycrystalline diamond cutting surfaces, the return configured to direct fluid to flow through the passage, wherein a fluid flowing through the passage is directed into the inside of the inner wall and substantially towards the further drill string member by the return.

9. A method of drilling comprising: providing a drill bit with a tubular body, and a plurality of polycrystalline diamond cutting surfaces arranged around a hollow space of the tubular body at a lower end of a drill string; engaging the drill bit in a drilling operation; directing fluid through at least one port in the tubular body onto the polycrystalline diamond cutting surfaces, the fluid then entering an opening to the hollow space while carrying cuttings; directing a fluid through a passage located between an outer wall and an inner wall of the tubular body proximal to the plurality of polycrystalline diamond cutting surfaces, the fluid flowing through the passage being directed into the hollow space of the tubular body and substantially towards a first end of the tubular body by the opening.

10. A method according to claim 9, wherein the fluid flow from the at least one port assists in the dissipation of heat created at the plurality of polycrystalline diamond cutting surfaces.

11. A method according to claim 9 or 10, wherein fluid flow from the at least one port encourages material cut by the plurality of polycrystalline diamond cutting surfaces to be entrained and carried through the hollow space of the tubular body.

12. A method according to claim 11, wherein fluid flow from passage between the outer wall and the inner wall of the tubular body which is directed into the hollow space assists material cut by the plurality of polycrystalline diamond cutting surfaces to be carried through the hollow space of the tubular body.

13. A method according to any one of claims 9 to 12, wherein the method further comprises introducing a second fluid to a first fluid, the fluids being directed into the passage and the at least one port.

14. A method according to claim 13, wherein the first fluid is air.

15. A method according to claim 13 or 14, wherein the second fluid is water.

16. A method according to any one of claims 13 to 15, wherein the method further comprises controlling the ratio of first fluid to second fluid.

17. A method according to claim 16, wherein the ratio is controlled according to the water content of a returned fluid from the inner wall of the tubular body.

18. A method according to claim 16, wherein the ratio is controlled according to the water content obtained from a rate of ground penetrated in a drilling operation.

19. A drill bit according to any one of claims 1 to 6 or a drill string according to claim 7 or 8, wherein the return directs the flow of fluid into the hollow space so as to encourage the rock chips and/or cored rock sample to be entrained and carried through the hollow space through the drill string towards the surface.

20. A drill bit according to any one of claims 1 to 6 or a drill string according to claim 7 or 8, wherein the return is U shaped to change the direction of fluid flow heading towards the second end of the tubular body so as to be heading towards the first end of the tubular body when the fluid enters the hollow space so as to provide sufficient fluid flow to encourage the rock chips and/or cored rock sample to be entrained in fluid flow through the hollow space through the drill string towards the surface.