AU2006201921A1 - Drilling apparatus and method - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service: SMS ASSET HOLDINGS PTY LTD Swick Drilling Australia PO Box 74 Guildford WA 6935

AUSTRALIA

Kent Jason SWICK Griffith Hack, Patent and Mark Attorneys, 19th Floor, 109 St Georges Terrace, Western Australia, 6000.

Trade Perth, Standard Complete Specification for the invention entitled: DRILLING APPARATUS AND METHOD The following is a full description of this invention, including the best method of performing it known to me:- 2 DRILLING APPARATUS AND METHOD Field of the Invention The present invention relates to a drilling apparatus and method, in particular to a drilling apparatus and method for drilling holes in consolidated or unconsolidated strata such as required for geo-environmental exploration and development, and installation of subsurface water-quality monitoring devices.

Background of the Invention Reverse circulation drilling is widely used in the mining industry for hard rock developments, including mine shaft construction, ore and water exploration and geotechnical analysis. The method employs a dual wall drill rod fitted with a drilling tool such as for example, a compressed air driven percussion hammer or a rotating drill bit. A fluidising medium, either compressed air, water, or drilling fluid is used to flush the drill bit, mobilise the resultant cuttings and facilitate ready recovery thereof.

The fluidising medium is supplied under high pressure to the cutting bit through the annulus disposed between inner and outer walls of the drill rod, and the mobilised cuttings and fluidising medium are forced back to the surface under pressure via a central lumen of the drill rod. The cuttings are then separated from the fluidising medium in an inline cyclone.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 3 When compressed air is used as the fluidising medium, the compressed air is frequently also forced up an annulus formed between the outer wall of the drill rod and the drill hole wall, generating large volumes of dust and occupational health and safety concerns for the operator. Additionally, the central passage of the drill rod can become blocked with clay, damp drill cuttings and/or rock fragments entrained in the compressed air and mobilised cuttings, at which point the velocity of air flow through the central passage drops. This drop in velocity leads to poor purging of drill cuttings and can lead to slow penetration rates, difficult drilling parameters and may also result in seizure of the drill bit, as will be described later.

There are several disadvantages associated with using reverse circulation drilling. Typically, reverse circulation drilling is capital intensive as it requires specialised drilling rods, a high pressure, high volume compressor and additional equipment. The vehicles on which the drilling rigs are transported are large and cumbersome, and one frequently has to cut access roads into areas where they will be operating.

Accordingly, an application for permission to drill for exploration purposes can be compromised if this particular technique is employed because the environmental impact of the drilling rig is far from negligible.

Vacuum drilling methods are also widely used in the mining industry, particularly in respect to operations where shallow bores are required. Typically, a vacuum pump is attached to a Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 4 swivel on top of a single wall drill rod, and air and mobilised cuttings are drawn through the lumen of the drill rod by the vacuum pump. To achieve continuous air flow, the annulus defined by the bore hole wall and the drill rod wall acts as a conduit for atmospheric air to travel to the drill bit. The cuttings are separated from the air stream in an inline cyclone. Cyclone overflow is passed through a bag filter and then an oil bath or paper element prior to the vacuum pump.

In suitable ground conditions, vacuum drilling methods demonstrate advantages over reverse circulation drilling techniques because the vacuum drilling method relies on low pressure air flow and does not require a compressor. In comparison, the vacuum drilling rig is compact and lightweight. The vacuum drilling method has up to 100% sample recovery and controls dust emissions. It suits shallow, small diameter drill holes and its compact nature allows for the system to be fitted onto small tractors, thereby improving its mobility in off-road areas, such as forested, uncleared terrain.

The effectiveness and efficiency of vacuum drilling is dependent on maintaining a clear, internal passage of the drill rod and the annulus around the drill rod free from blockages. Any restriction of either space will reduce the velocity of air flow, hence lowering the ability of the fluidizing medium to mobilise the cuttings and remove them from the vicinity of the drill bit. Seizure of the drill bit can occur when the removal of cuttings is compromised in this Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 5 way.

Typically, the drill bit becomes plugged with material when blockages occur because the driller has continued to drill for a brief period prior to realising that air circulation around the drill bit has been compromised or has ceased. Blockages occur both inside the bit body and the lower part of the drill rod. In the event of a blockage, the driller will have to "trip out" or pull the rods and clear the drill pipe and bit by using levers, pry bars as well as rattling or jarring the rods with a hammer.

Blockages frequently occur in unconsolidated ground, such as loose gravel or sand, because the annulus around the drill rod collapses or rock fragments become wedged in the drill bit.

Similarly, blockages occur in clay soils or wet terrain where there is an increased tendency for the lumen of the drill rod to become occluded or the drill bit plugged with material.

As a result of the downtime and occupational health and safety issues caused by blockages, vacuum drilling methods are often limited to shortened drilling seasons to avoid winter rains which cause clay soils to become water-logged, swell and cause blockages. Additionally, vacuum drilling methods are restricted from drilling on unconsolidated ground.

The present invention seeks to overcome at least some of the aforementioned disadvantages to vacuum drilling.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 N- 6-

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It is to be understood that, although prior art use and publications may be referred to herein, such reference does not constitute an admission that any of these form a part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

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IND

In accordance with a first aspect of the invention there is provided a drilling apparatus comprising a drill stem having a first passage in fluid communication with a second passage, a drill bit connected to the drill stem and provided with a cuttings passage through which cuttings formed by the drill bit can pass to the first passage, an apparatus for providing a fluidizing medium to the drill bit through the second passage to fluidize the cuttings, and an extraction apparatus in communication with the first passage for extracting the fluidized cuttings therefrom.

In one embodiment of the invention the drill stem has a first wall and a second wall outside the first wall and the first wall defines the first passage, and the spacing between the first and second walls is the second passage.

In one arrangement the first and second walls are cylindrical and concentrically disposed relative to one another, such that the first passage is a central passage and the second passage is an annular channel.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 7 Typically, the first and second walls are spaced by a distance less than the diameter of the first passage.

In one embodiment the drill bit is provided with at least one channel extending from the second passage to an outer surface of the drill bit in an arrangement whereby a portion of the fluidizing medium is directed from the second passage to the cuttings formed at the outer surface of the drill bit. Up to of the fluidizing medium is directed through the or each said channel.

In one embodiment of the invention the diameter of the cuttings passage is less than the diameter of the first passage.

In one embodiment the apparatus for providing a fluidizing medium is arranged in fluid communication with the second passage and supplies the fluidizing medium at positive pressure.

Typically, the fluidizing medium is supplied at low pressure.

The apparatus for providing the fluidizing medium may be a compressor or a pump.

In one embodiment the fluidizing medium is compressed air.

Typically, the compressed air is delivered at about 1 bar.

In an alternative embodiment the fluid is a liquid.

Kirstie/keep/speci/other specis/P5884 Ovacuumdrilling 9/05/2006 8 In one embodiment of the invention the extraction device for extracting the fluidized cuttings is arranged in fluid communication with the first passage and applies a negative pressure to the first passage to extract the fluidized cuttings. Typically, the extraction device comprises a vacuum pump. A negative pressure of between -10 kPa to kPa may be applied to the first passage.

In one embodiment the drilling apparatus further comprises a separating device arranged to separate the fluidized cuttings from the fluidizing medium. Typically, the separating device is configured upstream of the extraction device. The separating device may be a cyclone.

In one embodiment, the drilling apparatus further comprises a device to heat the fluidizing medium.

In accordance with a second aspect of the invention there is provided a method of drilling comprising feeding a drill stem having an first passage and a second passage and a drill bit into a substrate, delivering a fluid through the second passage and mobilizing cuttings formed at the drill bit, and extracting the fluidized cuttings through the first passage of the drill stem.

In one embodiment the step of delivering a fluid through the second passage comprises directing a flow of compressed air under low positive pressure through the second passage of the drill stem. Typically, the step of extracting the fluidized cuttings comprises applying a negative pressure to the first Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 9 passage of the drill stem. The negative pressure may be kPa to -80 kPa.

In one embodiment of the invention the method further comprises the step of separating the fluidized cuttings from the fluid.

In the description and claims of the invention, except where the context requires otherwise due to express language or necessary implication, the words "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features, but not to preclude the presence or addition of further features in various embodiments of the invention.

Brief Description of the Drawings Preferred embodiments, incorporating all aspects of the invention, will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a drilling apparatus in accordance with the present invention; Figure 2 is a schematic view of a drill stem and drill bit of the drilling apparatus shown in Figure 1; and Figure 3 is a perspective view of a leading face of the drill bit shown in Figure 2.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 10 Detailed Description of the Preferred Embodiments of the Invention Before the preferred embodiment of the present apparatus is described, it is understood that this invention is not limited to the particular materials described, as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing the particular embodiment only, and is not intended to limit the scope of the present invention in any way. It must be noted that as used herein, the singular forms and "the" include plural reference unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs.

Referring to the accompanying figures where like numerals refer to like features, there is shown a drilling apparatus in accordance with an embodiment of the present invention.

The drilling apparatus 10 includes a drill bit 20 connected to a distal end 32 of a drill stem 30. In this example, the drill stem 30 and drill bit 20 are fed into a substrate by rotational force supplied by a drill head 40 comprising a gear box and drive motors 42. The drill head 40 is mounted and supported for longitudinal translation on a mast 44.

Typically, the drilling apparatus 10 of the present invention is capable of drilling up to 50 m depth in consolidated or Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 11 unconsolidated strata. The preferred range of the diameter of the drill hole is 20-50 mm, however it will be understood that the drilling apparatus 10 can be readily adapted to produce drill holes with diameters outside of this range. In addition to drilling in earth strata, the drilling apparatus could be used to drill in overhead strata, side walls, and for other purposes, including but not limited to bore hole drilling for installation of rock bolts, explosive charges, and subsurface water-quality monitoring devices.

In this example, the drill stem 30 has an inner cylindrical wall 36 defining a central passage 31, and a concentrically disposed outer cylindrical wall 38 defining an annular channel 33 between the inner and outer cylindrical walls 36, 38. The spacing between the inner and outer cylindrical walls 36, 38 is less than the diameter of the central passage 31.

The central passage 31 is in fluid communication with the annular channel 33 in an arrangement whereby the annular channel 33 and the central passage 31 define a sequential flow path for a fluidizing medium within the drill stem and drill bit 20 of the drilling apparatus 10 of the present invention.

Typically, the drill stem 30 is provided with a plurality of stabilizing members 35 disposed in the annular channel 33 and extending between the inner and outer cylindrical walls 36, 38 to provide structural support thereto and maintain centralization of the inner cylindrical wall 36 within the Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 12 outer cylindrical wall 38. In this example, the stabilizing members 35 are a plurality of equiangularly spaced lugs disposed at regular intervals along the length of the drill stem 30. Alternatively, the stabilizing members 35 may be 0rings or circlips. The stabilizing members 35 are typically provided with longitudinally disposed apertures therethrough so as not to unduly restrict or disturb directional flow of the fluidizing medium through the annular channel 33.

The drilling apparatus 10 also includes an apparatus for providing a fluidizing medium 50 to fluidize cuttings formed at the drill bit 20. The fluidizing medium may be compressed air or a liquid. In this example said apparatus is a compressor 50 connected to an air swivel 52 via a conduit 54.

The air swivel 52 is disposed at an opposing end 34 of the drill stem adjacent to the drill head 40. The air swivel 52 is connected in fluid communication with the annular channel 33 of the drill stem 30 so as to direct a flow of compressed air from the compressor 50 to the drill bit In this example, the compressor 50 provides low pressure compressed air as a fluidizing medium to fluidize cuttings formed at the drill bit 20. Typically, the compressed air is provided at a pressure of about 1 bar.

The compressor 50 may also be provided with a device for heating the compressed air delivered through the annular channel 33 of the drill stem 30. This feature is particularly useful in instances where clay soils or particles of a substrate which swells when hydrated Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 13 accumulate in the central passage 31 of the drill stem In these instances a stream of heated air may be delivered through the annular channel 33 and then subsequently withdrawn through the central passage 31. As the heated air passes over and dries the accumulated particles in the central passage 31, the accumulated particles shrink. The shrunken particles can then be readily removed from the central lumen 31.

Additionally, the drilling apparatus 10 includes an extraction apparatus for extracting the fluidized cuttings through the central passage 31 of the drill stem 30. In this example the extraction apparatus is a vacuum pump connected to a sample swivel 62 via a conduit 64. The sample swivel 62 is disposed adjacent to the drill head 40 in fluid communication with the central passage 31 of the drill stem The vacuum pump 60 is arranged to apply a negative pressure to the central lumen 31 to remove the fluidized cuttings formed at the drill bit. Typically, a negative pressure of between -10 kPa to -80 kPa is applied to the central passage 31.

The drilling apparatus 10 may further include a separating device 70 arranged to separate the fluidized cuttings from the fluid. In the example illustrated in the figures, the separating device 70 is a cyclone 72 configured upstream of the vacuum pump 60. The cyclone 72 is a closed system so that the separated cuttings can be contained therein and the negative pressure applied to the central passage 31, sample Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 14 swivel 62 and conduit 64 is maintained and not compromised throughout the drilling procedure.

Referring to Figures 2 and 3, the drill bit 20 and drill stem 30 are shown in detail.

The drill bit 20 includes a drill blade 22 with cutting edges mounted on a solid cylindrical bit blank 24, and a bit body 26 arranged to be connectable to the distal end 32 of the drill stem 30 with a threaded joint 21 formed therebetween.

The bit body 26 comprises a cylindrical lower wall portion 26a welded at a lower edge 23 thereof to an upper surface 24a of the bit blank 24, and a cylindrical upper wall portion 26b having a threaded portion 25 and a plurality of spanner flats 27 equidistantly spaced around a circumferential periphery of the upper wall portion 26b to facilitate application of rotational force thereto to tighten or loosen the threaded joint 21.

The bit blank 24 is provided with a cuttings passage 27 extending between the upper surface 24a and a lower surface 24b of the bit blank 24, in fluid communication with the central passage 31 of the drill stem 30. The cuttings passage 27 is disposed in a central portion of the bit blank 24 proximal to the drill blade 22. It will be understood that the function of the cuttings passage 27 is to allow ingress of cuttings formed by the drill blade 22 into the central passage 31 of the drill stem 30, while at the same time filtering cuttings having a particle size which may be sufficiently large to block the central passage 31 of the Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 15 drill stem 30. Typically the diameter of the cuttings passage 27 is less than the diameter of the central passage 31 of the drill stem Additionally, the lower surface 24b of the bit blank 24 is provided with a chamfered portion 29 disposed adjacent to the cuttings passage 27. The chamfered portion 29 is configured to encourage a flow of particles with a particle size larger than the diameter of the cuttings passage 27 over the lower surface 24b of the bit blank 24 and away from the cuttings passage 27 to prevent blockages.

The upper surface 24a of the bit blank 24 has an annular recess 35 arranged to receive a lowermost edge 37 of the inner wall 26 of the drill stem 30 thereby defining a Ushaped flow path connecting the annular channel 33 to the central passage 31 of the drill stem 30. In the present example, a lower portion 39 of the inner wall 26 is outwardly tapered.

In this example, the bit blank 24 includes at least one channel 41 extending from the annular recess 35 to an outer surface of the bit blank 24 disposed proximal to the lower surface 24b. It will be understood that the function of the channel 41 is to direct a portion of the fluidizing medium from the annular channel 33 to an outer surface of the drill bit 20. The externally directed fluidizing medium flows over the lower surface 24b of the bit blank 24 to accelerate cuttings formed at the drill blade 22 and induce turbulence, thereby contributing to fluidization of the cuttings. Up to Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 16 of the fluidizing medium may be directed externally of the drill bit 20 in this way.

During use, the drill stem 30 and drill bit 20 are fed into a substrate by rotational force supplied by the drill head The drill head 40 is mounted and supported for longitudinal translation on a mast 44. Compressed air at about 1 bar, or an alternative fluidizing medium, is supplied by the compressor 50 and directed through conduit 54 to air swivel 52 and thence to the annular channel 33 of the drill stem Up to 70% of the compressed air stream travelling through the annular channel 33 is directed through the channel 41 to the outer surface of the bit blank 24, and flows over the lower surface 24b of the bit blank 24 to accelerate cuttings formed at the drill blade 22 and induce turbulence, thereby contributing to fluidization of the cuttings. The remaining portion of the compressed air stream flows through the Ushaped channel connecting the annular channel 33 and the central passage 31 and also contributes to fluidization of the cuttings in the central passage 31.

Once the cuttings around the drill bit 20 are mobilized in the compressed air as described above the negative pressure applied by the vacuum pump 60 to the central passage 31 facilitates ingress of the fluidized cuttings through the centrally disposed aperture 27 in the bit blank 24 into the central passage 31 of the drill stem Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 17 The fluidized cuttings are drawn through the length of the central passage 31 and then directed by sample swivel 62 along conduit 64 into the cyclone 70. The cuttings are separated from the air in the cyclone While the fluidizing medium is simultaneously applied at a positive pressure through the annular channel 33 of the drill stem 30, it is not applied at a pressure which overrides the negative pressure applied to the central passage 31 by the vacuum pump 60. It is important, nevertheless, to maintain a continual flow of fluidizing medium from the annular channel 33 through the central passage 31 so that the vacuum pump does not draw a continuous stream of air through an annulus defined by the bore hole wall and the outer wall 38 of the drill stem It will also be understood that although a portion of the fluidizing medium is directed externally of the drill bit to flow over the lower surface 24b of the bit blank 24 and accelerate cuttings formed at the drill blade 22, the fluidizing medium is applied at a low pressure, and not at a sufficiently high pressure for the fluidizing medium to be substantially directed through the annulus disposed between the outer wall 38 of the drill stem 30 and the bore hole wall, and generate dust therefrom.

Numerous variations and modifications will suggest themselves to persons skilled in the relevant art, in addition to those already described, without departing from the basic inventive concepts. All such variations and modifications are to be Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 18 considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006

Claims (26)

1. A drilling apparatus comprising a drill stem having a first passage in fluid communication with a second passage, a drill bit connected to the drill stem and provided with a cuttings passage through which cuttings formed by the drill O bit can pass to the first passage, an apparatus for providing IND a fluidizing medium to the drill bit through the second passage to fluidize the cuttings, and an extraction apparatus in communication with the first passage for extracting the fluidized cuttings therefrom.

2. The drilling apparatus according to claim 1, wherein the drill stem has a first wall and a second wall outside the first wall and the first wall defines the first passage, and the spacing between the first and second walls is the second passage.

3. The drilling apparatus according to claim 2, wherein the first and second walls are cylindrical and concentrically disposed relative to one another, such that the first passage is a central passage and the second passage is an annular channel.

4. The drilling apparatus according to claim 2 or claim 3, wherein the first and second walls are spaced by a distance less than the diameter of the first passage.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 20 The drilling apparatus according to any one of claims 1 to 4, wherein the drill bit is provided with at least one channel extending from the second passage to an outer surface of the drill bit in an arrangement whereby a portion of the fluidizing medium is directed from the second passage to the cuttings formed at the outer surface of the drill bit.

6. The drilling apparatus according to claim 5, wherein up to 70% of the fluidizing medium is directed through the or each said channel.

7. The drilling apparatus according to any one of the preceding claims, wherein the diameter of the cuttings passage is less than the diameter of the first passage.

8. The drilling apparatus according to any one of the preceding claims, wherein the apparatus for providing a fluidizing medium is arranged in fluid communication with the second passage and supplies the fluidizing medium at positive pressure.

9. The drilling apparatus according to claim 8, wherein the fluidizing medium is supplied at low pressure.

10. The drilling apparatus according to claim 8 or claim 9, wherein the apparatus for providing the fluidizing medium is a compressor or a pump. Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 21

11. The drilling apparatus according to any one of the preceding claims, wherein the fluidizing medium is compressed air.

12. The drilling apparatus according to claim 11, wherein the compressed air is delivered at about 1 bar.

13. The drilling apparatus according to claim 9 or claim wherein the fluid is a liquid.

14. The drilling apparatus according to any one of the preceding claims, wherein the extraction device for extracting the fluidized cuttings is arranged in fluid communication with the first passage and applies a negative pressure to the first passage to extract the fluidized cuttings.

The drilling apparatus according to claim 14, wherein the extraction device comprises a vacuum pump.

16. The drilling apparatus according to claim 14 or claim wherein a negative pressure of between -10 kPa to -80 kPa is applied to the first passage.

17. The drilling apparatus according to any one of the preceding claims, further comprising a separating device arranged to separate the fluidized cuttings from the fluidizing medium. Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 22

18. The drilling apparatus according to claim 17, wherein the separating device is configured upstream of the extraction device.

19. The drilling apparatus according to claim 17 or claim 18, wherein the separating device comprises a cyclone.

The drilling apparatus according to any one of the preceding claims, further comprising a device to heat the fluidizing medium.

21. A method of drilling comprising feeding a drill stem having an first passage and a second passage and a drill bit into a substrate, delivering a fluid through the second passage and mobilizing cuttings formed at the drill bit, and extracting the fluidized cuttings through the first passage of the drill stem.

22. The method according to claim 21, wherein the step of delivering a fluid through the second passage comprises directing a flow of compressed air under low positive pressure through the second passage of the drill stem.

23. The method according to claim 21 or claim 22, wherein the step of extracting the fluidized cuttings comprises applying a negative pressure to the first passage of the drill stem.

24. The method according to claim 23, wherein the negative pressure is -10 kPa to -80 kPa.

Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006 23 The method according to any one of claims 21 to 24, further comprising the step of separating the fluidized cuttings from the fluid.

26. A drilling apparatus substantially as hereinbefore described with reference to the accompanying Figures. Dated this 9th day of May 2006 SMS ASSET HOLDINGS PTY LTD By Their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia. Kirstie/keep/speci/other specis/P5884 0_vacuumdrilling 9/05/2006