WO2019134930A1

WO2019134930A1 - Drill bit with pcd button inserts

Info

Publication number: WO2019134930A1
Application number: PCT/EP2019/050081
Authority: WO
Inventors: Matthew John Ian LEEMING
Original assignee: Element Six (Uk) Limited
Priority date: 2018-01-08
Filing date: 2019-01-03
Publication date: 2019-07-11
Also published as: GB2570048A; GB201800251D0

Abstract

This disclosure relates to a percussive drill bit comprising PCD studs and a drill bit body protector to limit erosion of the drill bit body near the PCD studs. The drill bit body protector may take various forms such as a continuous hard facing layer, a plurality of cemented carbide studs, a wear resistant plate, a plurality of individual wear resistant washers, and a carbide support post attached to at least some of the PCD studs.

Description

Technical Field

The present disclosure relates to a drill bit for use in mining, oil and gas, and construction operations. It relates particularly but not exclusively to a down-the-hole (DTH) drill bit or a top hammer (TH) drill bit, which are specific types of drill bit used with a primarily percussive action.

Background of the Disclosure

Percussive drilling is used for drilling holes in a wide variety of rock types. Percussive drilling is used in, for example, the oil and gas industry to produce deep well bore holes. It is also used in the construction industry to produce pilings and footings. Percussive drilling is also used in mining operations, to drill holes filled with explosives which are subsequently detonated to allow access to ore within rock formations.

A percussive hammer and drill bit is one of the fastest ways of drilling rock. The hammer resembles a small jack hammer. It is air-powered with a high cyclic rate, and combines its fast action hammer with a rotary drilling action. This combined action rotates its chisel-like tip as it drives into rock formation, breaking it into chips and dust. Because the hammer is pneumatically powered, it has an air exhaust which blows the chips and dust from the bore.

The drill bit is mounted on the lower end of a drill string. The hammer, also known as the percussion mechanism, is located directly behind the drill bit in the case of DTH percussive drilling or above ground for TH percussive drilling. Drill pipes connected to the drill string serve to deliver the necessary feed force and rotation to the hammer and bit, along with compressed air. As the hole gets deeper, additional drill pipes are added successively.

Percussive drill bits are subject to extreme operational conditions, and like any other piece of equipment suffer from wear and tear. Once a drill bit becomes too worn to drill at an adequate rate or make a full-gauge hole, operations must be halted to replace the bit.

A worn prior art percussive drill bit is shown in Figure 1, indicated generally at 10. Button inserts 12 made of wear resistant cemented carbide have been provided on the bit impact face 14 in a bid to extend the operational life of the drill bit 10. However, the steel body 16 of the drill bit has worn away prematurely compared to the button inserts 12, and two of the button inserts 12 have been lost through a fault commonly known as‘button pop-out’. The seats of the two lost button inserts are indicated at 18. The advantages of the button inserts 12 have not therefore been fully realised. It is an object of the invention to provide a drill bit with optimised penetration rate and extended operational life.

Summary of the Disclosure

According to the invention, there is provided a drill bit comprising: a drill bit body having an impact face, a plurality of button inserts, each button insert comprising polycrystalline diamond (PCD) material, and a drill bit body protector to limit erosion of the drill bit body specifically near the button inserts.

During operation of the drill bit, rock chips and dust from the formation being drilled is swept across the impact face. Gradually, the drill bit body erodes away in a phenomenon commonly known as ‘body wash’. The drill bit body protector located proximate the button inserts significantly reduces the rate of erosion of the drill bit body such that the wear resistant benefits of the button inserts can be realised for longer, if not until such a time as the button inserts themselves have worn away. The drill bit body protector significantly reduces the risk of button pop-out occurring. Preferable and/ or optional features of the invention are provided in claims 2 to 16 inclusively. Brief Description of the Drawings

A more complete and thorough understanding of the present embodiment and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein: Figure 1 is a worn prior art drill bit;

Figure 2 is a top plan view of a first embodiment of the drill bit in accordance with the invention; Figure 3 is a perspective view of the drill bit of Figure 2;

Figure 4 is a plan view of a second embodiment of the drill bit;

Figure 5 is a perspective view of the drill bit of Figure 4;

Figure 6 is a plan view of a third embodiment of the drill bit;

Figure 7 is a perspective view of the drill bit of Figure 6;

Figure 8 is a plan view of a fourth embodiment of the drill bit; and

Figure 9 is a perspective view of the drill bit of Figure 8. Detailed Description

Figures 2 and 3 shows a first embodiment of the drill bit, indicated generally at 100. The drill bit 100 comprises a drill bit body 102, a plurality of polycrystalline diamond (PCD) button inserts 104, and a drill bit body protector 106 specifically to limit erosion of the drill bit body 102 proximate the button inserts 104.

The drill bit body 102 comprises an impact face 108, an internal conduit (not shown) for supplying pressurised fluid to the impact face, at least one exhaust port 110 in the impact face 108 and in fluid communication with the internal conduit, a gauge wall 112 and a shank 114 adjoining the gauge wall 112.

The drill bit body 102 has a central longitudinal axis. The impact face 108 comprises first and second face portions 108a, 108b, the first face portion 108a extending in a plane perpendicular to the central longitudinal axis, the second face portion 108b extending radially outwardly away from a peripheral edge of the first face portion 108a towards the gauge wall. The first face portion 108a is circular and the diameter of the first face portion 108a is less than the diameter of second face portion 108b.

In this embodiment, the impact face 108 is planar (i.e. flat or substantially flat). Flowever, the impact face 108 may alternatively be curved. If curved, it may be concave or convex. Concave faces are generally considered to excellent all-round performers, used as a general purpose bit for most conditions while drilling a very straight hole. Convex faces are used for a combination of speed and service life. Flat faces are best suited for broken or fragmented ground and hard formations.

The gauge wall 112 extends radially inwardly away from the second face portion 108b, before terminating at the shank 114. The shank 114 has a lateral cross-section with fixed diameter. The diameter of the shank 114 is the same or less than the diameter of the first face portion.

Three flutes 116 with arcuate bases extend axially though the second face portion 108b and the gauge wall 112. The flutes 116 are equi- angularly spaced about the central longitudinal axis. One or more further exhaust ports 110 open onto a corresponding quantity of flutes 116.

In this first embodiment, the drill bit body 102 comprises first and second body portions 102a, 102b, joined together at an interface 102c. The first body portion 102a is made from a conventional steel or an alloy thereof. The second body portion 102b comprises a cemented carbide layer, for example, tungsten carbide (WC) and this constitutes the drill bit body protector 106 in this embodiment. Alternatively, the drill bit body protector 106 may comprise a metal matrix composite, for example, titanium carbide (TiC) in a steel matrix, which is bonded to the steel first body portion 102a.

As a further alternative, the second body portion 102b may comprise a low melting point carbide (LMC) material, characterised by its iron base. Exemplary materials are described in US 8,968,834, US 8,846,207 and US 8,753,755. Other wear resistant materials could be used instead.

Two spherical button inserts 104 are arranged on the first face portion, near the primary exhaust port 110. Three additional button inserts 104 are arranged on the second face portion 108b, in- between the flutes 116. Each button insert 104 is seated in a correspondingly shaped recess in the impact face. The function of the plurality of button inserts 104 is to provide a cutting edge, enabling the drill bit to bite into the rock formation, and/ or to protect the drill bit body from erosion.

The diameter of each button insert 104 is 11 mm. Elowever, any diameter of button insert 104 may be used, for example, from 6 mm to 30 mm, preferably from 12 mm to 20 mm. The length of each button insert 104 is typically 10 mm to 40 mm. Optionally, short button inserts 104 may be used instead, typically having a length from 5 mm to 12 mm. The button inserts 104 are preferably brazed into position.

Alternatively, the button inserts 104 may be hemi-spherical, ballistic, or dome shaped and any combination of these shapes with spherical button inserts may be used. In particular, the shape of the button inserts 104 located on the first face portion 108a may be different to those located on the second face portion 108b.

In the embodiment where the first body portion 102a comprises tungsten carbide, the button inserts 104 are preferably secured in place in the impact face 108 using brazing. In the embodiment where the first body portion 102a comprises a metal matrix composite, the button inserts 104 are preferably shrink fitted in place.

Figures 4 and 5 shows a second embodiment of the down-the-hole drill bit, indicated generally at 200. For the sake of brevity, only the differences between the first and second embodiments are described here; all other aspects of the drill bit remain the same as for the first embodiment.

In this embodiment, the drill bit body 202 is monolithic, made from a single bulk material, which is a conventional steel or an alloy thereof.

In addition to the PCD button inserts 104, the drill bit body protector comprises a plurality of wear resistant studs 204, each seated in a correspondingly shaped recess (not shown). The studs 204 are secured to the body 202 using brazing, but alternatively press-fitting, shrink fitting, gluing or any other means of attachment could be used instead. Optionally, the wear resistant studs 204 are serrated, and preferably are pressed into position.

The studs 204 are preferably made from cemented carbide material, for example, tungsten carbide (WC).

The studs 204 are arranged in the impact face 108 and in the gauge wall 112. Ten of the studs 204 are provided in the first face portion 108a, and eight studs 204 surround each of the three button inserts 104 on the second face portion 108b. A further nine studs 204 are provided near the aforementioned three button inserts 104 but on the gauge wall 112, in-between the flutes 116. Each stud 204 has a diameter of 4mm, although other sizes could be used.

The spacing between studs 204 has been found to be important in order to provide sufficient wear protection. Preferably, the studs 204 are spaced apart by 3 mm to 10 mm, and ideally around 5 mm.

Ideally, the studs 204 are evenly distributed about the impact face 108, and around the button inserts 104.

Turning now to Figures 6 and 7, in which a third embodiment of the drill bit is indicated generally at 300. Again, for brevity, only the differences between the first and third embodiments are described here.

In this embodiment, like the second embodiment, the drill bit body 202 is monolithic, made from a single bulk material, which is a conventional steel or an alloy thereof.

The key difference is that the drill bit body protector comprises a single protective plate 302 fully covering the first face portion 108a, and also a plurality of washers 304 on the second face portion 108b. The protective plate 302 and washers 304 prevent wear of the drill bit body 202 around the button inserts 104.

The protective plate 302 extends across the first face portion 108a, underneath the button inserts 104. The shape of the protective plate 302 matches that of the first face portion 108a such that it does not matter whether or not the first face portion 108a is circular; the protective plate 302 is shaped accordingly. The protective plate 302 is not necessarily a separate rigid component joined to the drill bit body 202, it could comprise surface hardening or a layer of a different material applied to the drill bit body 202. For example, it may comprise an LMC hard facing, as mentioned earlier.

The quantity of washers 304 corresponds to the quantity of button inserts 104. Each button insert 104 has one washer 304 positioned underneath it and against the second face portion 108b, and is secured in place by at least the button insert 104. Each washer 304 has a diameter greater than the diameter of the button insert 104 it protects, for example, at least 2mm more, preferably between 3 mm and 5 mm more.

The protective plate 302 and washers 304 preferably comprise the same wear resistant material, which is significantly more wear resistant that the material of the drill bit body 202 that it protects. Preferably, the protective plate 302 and washers 304 comprise cemented carbide material, for example, tungsten carbide (WC).

The drill bit body protector need not have both protective plate and washers 304, it could consist of only the protective plate or only the washers 304.

Turning now to Figures 8 and 9, a fourth embodiment of the drill bit is indicated generally at 400. Again, for brevity, only the differences between the first and fourth embodiments are described here.

Again, like the second embodiment, the drill bit body 202 is monolithic, made from a single bulk material.

The key difference is the drill bit body protector comprises a plurality of support posts 402, one for each of the button inserts 104. Each support post 402 is joined to a corresponding button insert 104, for example, using brazing, depending on the shape of the button inserts 104 used. The support post 402 is elongate, and preferably cylindrical. The support post 402 extends away from the button insert 104 into the drill bit body 202, generally aligned with the central longitudinal axis of the drill bit body 202. Flowever, since the drill bit body 202 itself tapers inwardly, a portion of the support post 402 protrudes outside of the drill bit body 202 and is exposed (best seen in Figure 9). This enables the support post 402 to be subject to erosion in preference to the softer drill bit body. The support post 402 acts as sacrificial wear material to the drill bit body 202.

The support post 402 comprises a wear resistant material that is significantly more wear resistant than the drill bit body 202 which suffers from body wash. The support post 402 may comprise cemented carbide material, for example, tungsten carbide (WC).

Not all of the button inserts 104 need necessarily have a corresponding support post 302. The button inserts 104 situated on the second face portion 108b may exclusively have the support posts 402, as seen in Figure 9. Flowever, the button inserts 104 situated on the first face portion 108a may alternatively exclusively have the support posts 302. As a further alternative, all button inserts 104 both on the first and second face portions 108a, 108b may have a support post 402. To avoid erosion of any exposed support posts 402 which are not fully embedded within the drill bit body 202, the drill bit 300 may further comprise an annular guard 408 for protecting the support posts 402 from wear.

The annular guard 408 extends circumferentially around and contiguous the drill bit body 202, in the region of the support ports 402. In the region of the flutes 116, the annular guard 408 is spaced apart from the drill bit body 202 by an air gap 410.

The annular guard 408 is preferably made from steel or an alloy thereof, and may comprise the same material as the bulk material of the drill bit body 202.

While this invention has been particularly shown and described with reference to embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims.

Although the flushing medium has been described as being pressurised air, a by-product of the hammer action, the pressurised fluid to exit the exhaust ports 110 could be a liquid instead. In fact, the exhaust ports 110 are not essential to the invention and may be entirely omitted.

Similarly, the flutes 116 in each drill bit body are not essential to the invention and may be omitted too.

Although two button inserts 104 have been described on the first face portion 108a and three button inserts 104 on the second face portion 108b, any quantity of button inserts 104 may be used, for example, four, five, six or more.

It is of utmost important that each button insert 104 is retained in place on the impact face 108 for as long as possible by limiting, if not eliminating, erosion of the drill bit body near the button inserts by incorporating one or more of the drill bit body protectors described herein.

The drill bit could be used for rotary drilling as well as percussive drilling.

Certain standard terms and concepts as used herein are briefly explained below.

As used herein, polycrystalline diamond (PCD) material comprises a plurality of diamond grains, a substantial number of which are directly inter-bonded with each other and in which the content of the diamond is at least about 80 volume per cent of the material. Interstices between the diamond grains may be substantially empty or they may be at least partly filled with a filler material or they may be substantially empty. The filler material may comprise sinter promotion material. PCBN material comprises grains of cubic boron nitride (cBN) dispersed within a matrix comprising metal, semi-metal and or ceramic material. For example, PCBN material may comprise at least about 30 volume per cent cBN grains dispersed in a binder matrix material comprising a Ti-containing compound, such as titanium carbonitride and or an Al-containing compound, such as aluminium nitride, and or compounds containing metal such as Co and or W. Some versions (or "grades") of PCBN material may comprise at least about 80 volume per cent or even at least about 85 volume per cent cBN grains.

Claims

1. A drill bit comprising:

a drill bit body having an impact face,

a plurality of button inserts, each button insert comprising polycrystalline diamond (PCD) material, and

a drill bit body protector to limit erosion of the drill bit body proximate the button inserts.

2. A drill bit as claimed in claim 1, the drill bit body having a central longitudinal axis, wherein the impact face comprises first and second face portions, the first face portion extending in a plane perpendicular to the central longitudinal axis, the second face portion extending radially outwardly from the first face portion.

3. A drill bit as claimed in claim 2, wherein the button inserts are arranged on the first face portion and optionally also on the second face portion.

4. A drill bit as claimed in claim 1, 2 or 3, wherein the drill bit body protector is arranged on the impact face.

5. A drill bit as claimed in claim 4, comprising a gauge face extending from the impact face, wherein the drill bit body protector is also arranged on a gauge face of the drill bit body.

6. A drill bit as claimed in any preceding claim, wherein the drill bit body comprises first and second body portions joined together at an interface, the impact face being located on the second body portion.

7. A drill bit as claimed in claim 6, wherein the drill bit body protector comprises cemented carbide on or in the second body portion.

8. A drill bit as claimed in claim 6, wherein the drill bit body protector comprises a metal matrix composite on or in the second body portion.

9. A drill bit as claimed in any preceding claim, wherein the drill bit body protector comprises a plurality of spaced apart cemented carbide studs.

10. A drill bit as claimed in claim 9, wherein the studs are spaced apart by a distance of between 3 mm and 10 mm, preferably between 3 mm and 7 mm, or preferably about 5 mm.

11. A drill bit as claimed in claim 9, wherein the studs are spaced apart by a distance of 1 to 3 times the diameter of the stud.

12. A drill bit as claimed in any preceding claim, wherein the drill bit body protector comprises a protective plate.

13. A drill bit as claimed in any preceding claim, the drill bit body protector comprising a washer to be placed contiguously against selected button inserts.

14. A drill bit as claimed in any preceding claim, wherein the drill bit body protector comprises an elongate support post, each support post being joined to one of the button inserts and extending axially into the drill bit body.

15. A drill bit as claimed in claim 14, further comprising an annular guard for protecting the support posts from wear, said annular guard extending circumferentially around the drill bit body.

16. A drill bit as claimed in any preceding claim, wherein the button inserts have a diameter of 6 mm to 30 mm, or preferably from 12 mm to 20 mm, or preferably 11 mm.