AU2015354408B2

AU2015354408B2 - Drill bit

Info

Publication number: AU2015354408B2
Application number: AU2015354408A
Authority: AU
Inventors: David HANNS
Original assignee: Drillterra Tech Pty Ltd
Current assignee: Drillterra Technologies Pty Ltd
Priority date: 2014-11-26
Filing date: 2015-11-26
Publication date: 2021-05-20
Anticipated expiration: 2035-11-26
Also published as: AU2015354408A1; WO2016082002A1

Abstract

A drill bit including a main body portion including three legs extending therefrom, with the three legs being arranged around a periphery of the main body portion. A conical cutter is rotatably mounted on each leg, where the conical cutters are positioned to allow a clearance between the conical cutter and the main body portion. A protrusion extends from the main body portion into the clearance, wherein the protrusion encourages drill cuttings away from a base region of the main body portion where the legs meet the main body portion.

Description

DRILL BIT

Technical Field

The present invention relates to a drill bit, and particularly to a tri cone drill bit.

Background

With reference to Figure 1, a typical tri cone drill bit is shown which includes a main body portion with a generally cylindrical outer surface which includes a threaded portion (not shown) by which the drill bit is connected to the end of a drill string (not shown).

Extending from the main body 2 in an axial downward direction (although Figure 1 shows the drill bit in the reversed orientation), are three legs equally spaced about a central longitudinal axis of the main body portion.

The three legs are connected to three conical cutter elements which are able to rotate relative to the legs which are fixed with respect to the main body portion. The conical cutting elements are typically provided with several rows of teeth.

Inspection of drill bits during operational life has consistently shown that the flow of air and fragmented material must take a specific path in order to exit from under and then around the bit.

Therefore, it would be advantageous to provide a tri cone drill bit, which would overcome at least some of the disadvantages of previously known approaches in this field, or would provide a useful alternative.

The present invention seeks to provide a drill bit which facilitates the removal of fragmented material from under the drill bit and hence provide a drill bit which provides increased efficiency during the drilling operation.

Summary

According to a first aspect, the present invention provides a drill bit including a main body portion including three legs extending therefrom, the three legs arranged around a periphery of the main body portion; a conical cutter rotatably mounted on each leg, the conical cutters positioned to allow a clearance between the conical cutter and the main body portion; a protrusion extending from the main body portion into the clearance, wherein the protrusion encourages drill cuttings away from a base region of the main body portion where the legs meet the main body portion.

In one form, the protrusion forms an apex substantially equidistant to the three legs. In a further form the protrusion includes a sloping surface between the apex and a base region of the main body portion. In an additional form the sloping surface continues through the base region of the main body portion, emerging at an outer surface of the main body portion. In a still further form, the protrusion includes a plurality of sloping faces converging at the apex. In another form the sloping faces are convex, defining a ridge between the sloping faces.

In one form, the drill bit further includes one or more air outlets located on the base region of the main body portion and configured to direct air substantially toward the conical cutters. In another form the one or more air outlets are elongated with a long axis in the direction radial to the longitudinal axis of the main body portion. In a further form, the air outlets are located at the periphery of the base region of the main body portion, between the region occupied by the legs. In a still further form, the legs and one or more air outlets are positioned within the ridges, the sloping face then forming channels for drill cuttings to flow therethrough, the channels originating from the apex, passing between the legs and one or more air outlets, and continuing through to the outside surface of the main body portion. According to a final form the air outlets are in the form of nozzels.

In one form the apex of the protrusion is approximately level with the bottom of the cutting cones.

In one form the legs are configured to twist around the main body portion.

In one form the air outlet is integrated into the legs, and wherein the legs twist away from the integrated air outlet thus locating the air outlet substantially between the cutting cones.

In one form the cutting cone is configured with teeth at the tip of the cutting cone.

Brief Description of the Accompanying Figures

The present invention will become better understood from the following detailed description of various non-limiting embodiments thereof, described in connection with the accompanying figures, wherein:

Figure 1 is a view of a prior art tri cone drill bit; Figure 2 is a view of a tri cone drill bit in accordance with the present invention; Figure 3 is an alternative view of a tri cone bit in accordance with the present invention, shown in a rendered presentation; Figure 4 is a plan view in accordance with the present invention; Figure 5 is a section view in accordance with the present invention; Figure 6 is an alternate section view in accordance with the present invention; Figure 7 is a view of an alternative embodiment of the present invention; Figure 8 is a view of another alternative view of the present invention.

Parts List 1 prior art drill bit 2 main body portion of the drill bit 3 legs 4 cutting cones 5 base region of main body portion 6 air outlet

7 drill bit according to present invention 8 protrusion 9 apex of protrusion 10 ridge 11 sloping face of protrusion 12 channel 13 outer surface of the main body portion 14 scallops 15 modified air outlet 16 shirt tail 17 bearings

Detailed Description of Embodiments and the Accompanying Figures

A typical tri-cone drill bit is shown in Figure 1. This drill bit 1 may be coupled with a drill string (not shown). The drill bit has a main body portion 2, from which three legs 3 extend in a direction substantially co-linear with the main body portion 2 and the attached drill string. The legs 3 are positioned at even intervals around the periphery of the drill bit, and are each adapted to mount a conical cutter 4. The conical cutters 4 are each configured to rotate around an axis of rotation. The conical cutters 4 will generally have teeth or an abrasive surface such that the three rotating cones form a drill face, cutting or grinding through material placed in contact thereof.

Material removed by the conical cutters 4, referred to as drill cuttings or cuttings, is substantially drawn towards a base region 5 of the main body portion 2, through the rotating action of the cutters 4 and the advance of the drill bit into the hole being drilled. The base region 5 of the main body portion 2 is located in the general region where the legs 3 meet the main body portion 2.

Drill cuttings that are not drawn away from the base region 5 may accumulate in the hole being drilled an in the general vicinity of the drill bit. This accumulation of material can lead to the regrinding of the material, which lowers the productivity of drilling, and leads to additional abrasive wear of the drill bit. Removal of drill cuttings away from the conical cutters 4 and more generally, away from the base region 5, is critical to the drilling efficiency and operational life of the drill bit 1.

Referring still to Figure 1, the drill bit 1 includes one or more air outlets 6. The air outlets are configured to blast high pressure air into the hole being drilled. This air dislodges and removes drill cuttings from in front of the drill face for reasons already described. The air outlets 6 are generally located at the periphery of the main body portion 2, between the legs 3. In certain embodiments, the air outlets 6 are located adjacent or substantially adjacent to the legs 3, whereas in the embodiment of Figure 1, they are equidistant to the legs.

Inspection of tri cone drill bits during operational life has consistently shown that the flow of air and fragmented material must take a specific path in order to exit from under the cones 4 and away from the base region 5. Cuttings generated by the cones 4 fall are projected onto the base region 5 of the main body portion 2 as a hole is being drilled. Due to the flat characteristic of base region 5, drill cuttings will accumulate here and interfere with the flow of cuttings away from the hole. This results in significant turbulence of drill cuttings in the region of the drill bit 1, which causes disruption to the flow of particles trying to exit from under the drill bit and out of the hole.

In addition, the positioning of the air outlets 6 results in a portion of drill cuttings moving away from the base region 5 will become entrained in the air flow directed toward the hole. This entrainment will continually return a portion of the drill cuttings into the hole being drilled by the drill bit 1, instead of exiting away from the drill bit as intended. This phenomenon also adds to the turbulence in the flow of drill cuttings discussed in the paragraph above.

Air blasting of drill cuttings back down into the hole leads to re-grinding of these cuttings. Re-grinding causes significant additional wear on the drill bit and also lowers drilling efficiency due to additional energy expenditure as cuttings are re-ground into smaller and smaller sizes. The additional wear and loss of efficiency caused by re-grinding results in limitations on the drill speed (penetration rates), higher air back pressure and reduced air flow, and significant amounts of dust. Consequently, there is a long felt need to remove cuttings as larger pieces with as little re-grinding as possible.

The present invention seeks to improve the removal rate of drill cuttings, both from the hole being drilled and from the drill bit in order to increase productivity of drilling and reduce abrasive wear on the drill bit.

Figure 2 shows a certain embodiment of a tri cone drill bit 7 according to the present invention. In this embodiment the base region 5 is adapted to include a protrusion 8. This protrusion 8, is configured to extend from the base region 5 into the clearance, or space, between the base region 5 and the cutting cones 4.

According to certain embodiments, the protrusion 8 will converge substantially to an apex 9. In the embodiment of Figure 2, this apex 9 is sharply defined, but in other embodiments, apex 9 may be blunt, or less defined. In the embodiment of Figure 2, the protrusion 8 and the apex 9 are symmetrically arranged on the base region 5 of the main body portion 2. Such a configuration includes the apex 9 being positioned substantially equidistant from each of the legs 3 and the cones 4. Also, in such a configuration, the apex 9 is centred underneath the meeting point of the three cones 4.

As a portion of the drill cuttings are conveyed towards the base region 5 of the main body portion 2 by the rotation of the cones 4 and the advance of the drill bit into the hole being drilled, the cuttings will fall incident on the protrusion 8 rather than the flat base region 5 of the prior art drill bit 1 of Figure 1. Cuttings incident on the protrusion 8 are guided by the sloping face of the protrusion 11 towards the periphery of the base region 5 of the main body portion 2. The effect of the protrusion 8 is to prevent accumulation and turbulence of cuttings in the region of the drill bit. This results in an increase in the kinetic energy of the cuttings and the speed by which cuttings are moved away from the drill bit 7 and the hole being drilled, reducing the regrinding of the cuttings, which in turn leads to greater drilling productivity and reduced abrasive wear on the drill bit.

The protrusion 8 of the drill bit 7 is also advantageous when drilling in soft boggy ground. As is the case with particulate cuttings, the protrusion 8 guides the soft ground and cuttings away from the base region 5 more efficiently than the flat base region of the prior art drill bit 1. This will decrease instances of the drill bit becoming plugged by soft material, which can lead to the drill bit becoming bogged in the hole. The bogging of a drill bit is a major problem which can take extensive down time to rectify and can ultimately lead to early bit failure.

The protrusion 8 of the embodiment showing in Figure 2 is formed from a plurality of sloping faces converging at the apex 9. In the non-limiting embodiment shown, each sloping face is concave, resulting in ridges 10 being formed between adjacent sloping faces 11. These ridges 10 have been arranged in such a manner as to define clear channels 12 in the protrusion 8. These channels offer a path for cuttings to pass unobstructed past obstacles such as the legs 3 and air outlets 15. This effect is further enhanced by smoothly moulding the legs 3 and air outlets 15 into the ridges 10. According to the embodiment of Figure 2, it is possible to continue the sloping face 11 of the protrusion 8 through the base region of the main body portion 5, emerging at an outer surface 13 of the main body portion 2. This effectively produces scallops 14 in the outside surface of the main body portion 2 allowing the channels 12 to continue with a steeper gradient than would otherwise be possible.

It has been found that a protrusion 8 with sloping faces 11 of a constant gradient provide the most efficient path for drill cuttings. This is because the channels 12 formed into such a protrusion 8 will not experience changes of direction that will impede flow. However, it is to be understood that other embodiments are possible without departing from the scope of the invention.

When comparing the prior art drill bit 1 of Figure 1 with the embodiments of Figures 2 to 6, it may seem the case that the available area beneath the cutting cones 4 and the main body portion 2 for cuttings to escape is smaller. It may be reasonable to conclude that the protrusion 8 forms an obstruction that would interfere with the removal of cuttings from the drill site, which would lower drill productivity. However, the configuration of channels 12 provided by the ridges 10 and scallops 14 provides a clear and aerodynamic path for the removal of drill cuttings. Although the available area for drill cuttings to escape may be reduced compared to the prior art drill bit of Figure 1, the defined channels 12 will result in an increase in air velocity through these channels, providing a more efficient path for the removal of drill cuttings. Also, the elevated air velocity through the channels 12 will allow for larger particles to be removed from the drill site, greatly reducing the occurrence of re-grinding.

Furthermore, the flow path provided by the defined channels 12 allows for a more orderly airflow pattern in the vicinity of the drill site. This will minimise air flow disruptions experience in prior art drill bits 1 such as vortexing, and turbulence which greatly reduce the flow of cuttings out of the hole, leading to re-grinding.

In the embodiment of Figures 2 to 6, the protrusion 8 is shown to extend into the clearance between the base region 5 and the legs 3 such that the apex 9 is set at about the same plane as the bottom of the cutting cones 4. It has been found that a substantial protrusion 8 allows significant channels 12 to be formed. However, if the protrusion 8 is made too large, it may obstruct larger drill cuttings and become counter productive. Thus a balance is required in providing a large enough protrusion 8 to allow the benefits of channelling 12 and allowing for enough clearance for larger drill cuttings.

Different angles for the sloping face of the protrusion 11 may also find benefit for different applications. For example, when drilling hard ground, it may be advantageous to use a shallow angle, allowing the legs 3 to be larger and hence stronger. In applications such as this, the amount of steel used internally in the bit could also be increased to impart additional strength.

The reduction in regrinding due to the present invention may also reduce abrasive wear to the shirt tails 16 of the bit 7. These shirt tails 16 protect the bearings 17 of the rotating cones. When sealed bearings are used, excessive shirt tail 16 wear causes the bearings 17 to become exposed and leak lubricating fluid, leading to drill failure. As sealed bearings are generally preferred to normal air bearings in mining and oil field applications, the present invention may lead to productivity gains in these industries. However, the present invention is suitable and advantageous for use with open air bearings with rollers as well as sealed journal or roller bearings.

The quick removal of drill cuttings by preserving their velocity and kinetic energy and other debris from the hole being drilled is a key factor in drill productivity and reduced production costs. Referring once more to Figure 1, in typical tri cone bits, the exit point of the air outlet 6 are positioned between legs 3 at a distance substantially equidistant to each leg. This arrangement results in the air outlet occupying approximately 1/3 of the space available between the legs. A large portion of the drill cuttings attempting to exit from the base region 5 of the main body portion 2, may become entrained in the high pressure air emanating from the air outlet 6. A portion of this entrained material will be re-blasted into the hole being drilled instead of being removed, leading to the regrinding of cuttings.

According to an embodiment of the present invention, the air outlets 15 can be shaped to occupy a smaller portion of the path available to drill cuttings to flow away from the drill bit. In a particular non-limiting embodiment, the air outlet can elongated 15 with a long axis orientated in a direction substantially radial to the longitudinal axis of the main body portion. In another non-limiting form, the air outlet 15 can be positioned closer to the legs 3 of the drill bit 7. Such an arrangement reduces the resistance to drill cuttings exiting the base region of the drill bit, and reduces the regrinding of material returned to the drill hole by entrainment in blast air.

In the embodiment of Figure 2, the elongated air outlet 15 is positioned within a ridge 10 of the protrusion 8. Otherwise stated, the air outlet 15 is positioned outside of a channel 12, formed for the conveyance of drill cuttings and debris away from the drill bit 7. This arrangement completely removes the air outlet 15 from the path of cuttings flowing away from the drill bit 7 by way of the channel12.

In certain embodiments, the cutting cones 4 can be configured with additional cutting teeth at the portion of the cone furthest from the legs. This will reduce instances of coring which can lead to uneven drilling at the centre portion of the hole where the individual drill cones meet.

In effect, the drill bit 7 may actually have less available area for cuttings to be removed when compared to the prior art bit 1, which is contrary to conventional wisdom in drill design. However, this configuration leads to faster and more developed air-flow within the channels 12 allowing for larger particles to be removed from the drill site with greater efficiency and less regrinding. The formation of ridges 10 in order to define the channels 12 in the protrusion 8 allows the air outlets 15 to be placed in a position where they do not obstruct the flow of particles. The placement of air outlets 15 within the path of cuttings is a major drawback of prior art bits 1, which results in the air blasting of cuttings back into the hole. The combined effect of providing channels 12 and locating the air outlets 15 away from the channels provides for a faster, unobstructed and more developed flow path for drill cuttings. This allows for more efficient conveyance of cuttings away from the drill site and greatly reduced occurrences of re-grinding. By reducing re-grinding, drilling is more efficient with less wear of the drill bit, allowing for drilling operations at faster speeds and increase air flow and pressure which increases drill productivity.

An alternative embodiment is shown in Figure 7. Here the drill bit 7 is configured with legs 3 that are twisted around the main body portion 2. The twist is configured towards the direction of rotation. This embodiment also involves the channels 12 being configured with a twist between the apex 9 of the protrusion 8 and the space between the legs 3. In the embodiment of figure 7, the air outlet 15 is integrated with the twisted leg 3, which positions the air outlet 15 outside of the flow path defined by the channels 12. The twist of the legs 3 angle the cutting cones 4 away from the air outlet 15. The ability of the twisted legs 3 to be offset from the integrated air outlets 15 allows the air outlets to be located away from a central region of the cutting cones, such as in the embodiment of Figure 7 where the air outlets 15 are positioned between the cones, where obstruction to air flow may be reduced.

In contrast with the embodiments of Figure 2 to 6, the embodiment of Figure 7 only requires the legs 3 to be located in the ridges 10, rather than both the legs and the air outlets 15. This configuration allows for fewer and wider channels 12. Moreover, the space saving provided by the twisted leg 3 configuration allows for the use of thicker and stronger legs when compared to the embodiments of Figures 2 to 6, particularly at the region where the legs join with the base region 5 of the main body portion 2, whilst still providing adequate space for the provision of channels 12. This configuration may lead to a drill bit 7 with more robust legs 3, which may reduce wear of the bit. As the twist is configured towards the direction of rotation of the drill bit 7, the legs 3 will maintain structural integrity under severe operational loads by the fact that the torsional forces will be aligned to be transferred along the long axis of the legs, rather than across the legs, which may lead to a shear stress in straight leg drill bits. Figure 8 depicts a similar embodiment to Figure 7, with a modified leg design.

The air outlet in the present invention may be a simple aperture, as represented in Figure 2, or a nozzle, is desired for the drilling application.

The foregoing describes only some embodiments of the present invention, and modifications and/or changes can be made thereto without departing from the scope and spirit of the invention, the embodiments being illustrative and not restrictive.

In the context of this specification, the word "comprising" means "including principally but not necessarily solely" or "having" or "including", and not "consisting only of". Variations of the word "comprising", such as "comprise" and "comprises" have correspondingly varied meanings.

Industrial Applicability

The present invention can be utilised in the field of open cut mine drilling and underground drilling, and in particular applications such as mining, water well drilling, well and ore sample drilling, exploration drilling, oil and gas drilling and tunnelling.

Claims

1. A drill bit including: a main body portion including three legs extending therefrom, the three legs arranged around a periphery of the main body portion; a conical cutter rotatably mounted on each leg, each of the conical cutters being positioned to allow a clearance between the conical cutter and the main body portion; a protrusion extending from the main body portion into the clearance; and a plurality of channels for drill cuttings to flow therealong, that each originate upon the protrusion and proximal to a protrusion apex and extend between adjacent legs, and continue through to an outside surface of the main body portion; wherein each of the three legs are shaped to curve around the main body portion in a direction of rotation of the conical cutter mounted thereto; and each of the plurality of channels are curved, along at least a portion from proximal to the protrusion apex to between the adjacent legs, to substantially match the curvature of the legs.

2. A drill bit according to claim 1 wherein the protrusion apex is substantially equidistant to the three legs.

3. A drill bit according to claim 1 or 2 wherein each of the plurality of channels are at least partially formed by a sloping surface between the apex and a base region of the main body portion.

4. A drill bit according to claim 3 wherein each of the plurality of sloping surfaces continues through the base region of the main body portion, emerging at an outer surface of the main body portion.

5. A drill bit according to claim 3 or 4 wherein a ridge is defined between each adjacent pair of the plurality of sloping surfaces.

6. A drill bit according to any one of the preceding claims, further including one or more air outlets located on the base region of the main body portion and configured to direct air substantially toward the conical cutters.

7. A drill bit according to claim 6 wherein the one or more air outlets are elongated with a long axis in the direction radial to the longitudinal axis of the main body portion.

8. A drill bit according to claim 6 or 7 wherein the air outlets are located at the periphery of the base region of the main body portion and between an adjacent pair of the legs.

9. A drill bit according to claim 5 wherein the ridges extend from proximal to the protrusion apex to one of the legs.

10. A drill bit according to any one of claims 6 to 8, wherein the air outlets are in the form of nozzles.

11. A drill bit according to any one of the preceding claims, wherein the protrusion apex is approximately level with the bottom of the cutting cones.

12. A drill bit according to claim 6 or 7, wherein the air outlet is integrated into the legs such that the legs curve away from the air outlet, thereby positioning the air outlet to direct air substantially between the cutting cones.

13. A drill bit according to any one of the preceding claims, wherein the cutting cone is configured with teeth at the tip of the cutting cone.

14. The drill bit according to any one of the preceding claims, wherein each of the plurality of channels extend into scallops located on the outer surface of the main body portion.

15. The drill bit according to any one of the preceding claims, wherein each of the legs extend along the main body portion; and the curvature of the leg extends substantially therealong.