Field of the Invention

The present invention relates to a component for a drill string. The present invention also relates to a drilling assembly including the component and to drilling methods and systems using the component and/or drilling assembly.

Background of the Invention

Despite developments in drilling technology over the last thirty years, the rate of penetration (ROP) achieved in hard rock drilling has only improved marginally. The improved ROP can be largely attributed to the improvements in drilling rigs, with the most significant change being drill rigs capable of generated higher rotation speeds which equates to more cuts per minute and hence increased ROP. For example, in the early 1990’s the fastest rotation speed for a diamond drill was around 600rpm and currently they range from 1100 to 2500rpm.

For hard rock drilling a drill bit is located at the leading end of a drill rod comprised of a number of pipe sections. More pipe sections are attached at the top of the drill rod, allowing greater depths to be drilled as needed. The deeper the drilled hole, the greater the contact surface area between the drill string and the drilled hole, and hence the greater the friction. The higher the friction, the more energy and higher rotation speeds are required to achieve a given ROP. Drilling fluids can be introduced into the drilled hole as lubricants to reduce this friction but, the introduction of fluid into the drilled hole increases the fluid pressure in the drilled hole further increasing the amount of energy required to reach a given rotation speed and ROP. Thus, there is often a “trade-off” when using drilling fluids and the choice of suitable drilling fluids for use with existing drilling assemblies can be constrained accordingly.

The present invention seeks to provide a component for a drill string and associated drilling assemblies, drill strings and drilling methods that address, at least partially, the problems and limitations discussed above with respect to the prior art hard rock drilling systems, methods and components. Summary of the Invention

According to a first aspect, the present invention provides a component for a drill string, the component having a central axis and comprising:

(a) a trailing end;

(b) a leading end; and

(c) at least one fluid flow enhancing element projecting from an outer surface of the component for enhancing fluid flow towards said trailing end, when the drill string is rotated around said axis in a direction of rotation.

The present invention also provides a drill string comprising a component according to the first aspect of the invention.

The present invention also provides a drill assembly comprising a component according to the first aspect of the invention or a drill string as described herein.

According to another aspect, the present invention provides a method of drilling a hole in a substrate, the method comprising the steps of:

(i) drilling a hole in the substrate with a drill string as described herein; and

(ii) delivering a mechanical lubricant to an annulus formed between the drill string and said hole.

Brief Description of the Drawings

Figure 1 a is a side view of a component according to one embodiment of the first aspect of the present invention, shown in the form of a reamer with its leading end at the bottom of the figure;

Figure 1 b is a perspective view of the reamer in Figure 1 a, from its leading end;

Figure 1 c is another perspective view of the reamer of Figure 1 a, shown attached to a drill bit at its leading end;

Figure 1d is a detailed view of the portion marked with an “X” on Figure 2, showing an embodiment of a fluid flow enhancing element in more detail; and Figure 2 is a side view of two reamers depicted in Figure 1a joined together, end to end, as they may appear as part of a drill string.

Detailed Description of the Invention

According to a first aspect, the present invention provides a component for a drill string, the component having a central axis and comprising:

(a) a trailing end;

(b) a leading end; and

(c) at least one fluid flow enhancing element projecting from an outer surface of the component for enhancing fluid flow towards said trailing end, when the drill string is rotated around said axis in a direction of rotation.

Preferably, the drill string comprises a drill bit and a drill pipe. The drill string may also comprise one or more other components selected from the list comprising: a reamer, a stabiliser, a centraliser, a downhole motor, a measurement tool, a logging tool, a transition drill pipe, a heavy weight drill pipe, a drill collar, a connector.

The fluid flow enhancing element can be located on the outer surface of one or more drill string components, such as those listed above, for example a reamer, a drill pipe or a drill bit.

Preferably, the component comprises a generally cylindrical shape and defines a hollow interior extending between the trailing end and the leading end.

Preferably, the trailing end defines a threaded engagement means compatible with a portion of the drill string such as a drill pipe or a reamer.

Preferably, the leading end defines a threaded engagement means compatible with a portion of the drill string such as a drill pipe or a drill bit.

Preferably, the fluid flow enhancing element comprises a foil member including a head portion defining a first leading edge, that in use, faces the direction of rotation.

Preferably, the first leading edge faces towards the leading end of the component. Preferably, the foil member further comprises a tail portion defining a first trailing edge, that in use, faces away from the direction of rotation.

Preferably, the first trailing edge faces away from the leading end of the component.

Preferably, the foil member further comprises a second leading edge, that in use, faces the direction of drilling.

Preferably, the second leading edge is curved or arcuate.

Preferably, the foil member further comprises a second trailing edge, that in use, faces away from the direction of drilling.

Preferably, the second trailing edge is straight.

Preferably, the foil member is located on the component such that a main axis of the second trailing edge is offset at an angle of 65-85°, 70-85°, 73-82°, 75-80°, 76-79° or about 77.5° to a main vertical or a longitudinal axis of the component or the central axis. Said angle is related to the drilling speed or rotation of the component. Preferably, the lower the drilling speed the smaller said angle (a smaller angle corresponds to a foil member that is angled more downwards on the component) to ensure the requisite amount of lift is provided. A foil member located on the component such that a main axis of the second trailing edge is offset at an angle of 75-80° to a main vertical or a longitudinal axis of the component or the central axis is suitable for drilling rotation speeds of 820-1350rpm.

Preferably, the foil member comprises a tail portion extending away from the head portion.

Preferably, the tail portion extends away from the leading end of the component.

Preferably, the tail portion tapers away from the head portion.

Preferably, the foil member is located on the component such that a foil chord defined by the foil member intersects a plane, passing through the component at a right angle to the longitudinal axis of the component, to define an angle therebetween of about 5- 20°, 7.5-17.5°, 10-15° or about 12.5°. Said angle is related to the drilling speed or rotation of the component. Preferably, the lower the drilling speed the larger said angle (a larger angle corresponds to a foil member that is angled more downwards on the component) to ensure the requisite amount of lift is provided. A foil member located on the component such that a foil chord defined by the foil member intersects a plane, passing through the component at a right angle to the longitudinal axis of the component, to define an angle therebetween of 10-15 is suitable for drilling rotation speeds of 820-1350rpm.

Preferably, the foil member is a foil such as an air foil or hydro foil. However, the foil member can be any object shaped such that when the drill string is rotated, the component including the foil member imparts a lifting force on or otherwise enhances flow of fluid around the drill string and away from the drill bit.

Preferably, the fluid low enhancing element further comprises at least one insert of relatively hard material.

Preferably, the foil member further comprises at least one insert of relatively hard material.

Preferably, the hard material is located on the head portion of the foil member.

Preferably, the at least one insert is located at or near the second trailing edge of the foil member.

Preferably, when in use as part of a drill string, the at least one fluid flow enhancing element is adapted to increase a fluid flow rate in an annulus formed around the drill string.

Preferably, the fluid flow rate in the annulus is increased by increasing an effective volume of the annulus.

For the purposes of the present invention the term “effective volume of the annulus” is intended to refer to the volume available in the annulus for carrying drilled material. In this regard, whilst not being limited to any particular mechanism, applicant understands the component of the present invention results in the formation of additional pathways for drilled material in the annulus.

Preferably, the component comprises a plurality of fluid flow enhancing elements. Preferably, the plurality of fluid flow enhancing elements are arranged around the outer surface of the component to define a path therebetween for fragments of drilled material.

Preferably, the plurality of fluid flow enhancing elements are spaced equidistantly from each other.

Preferably, the plurality of fluid flow enhancing elements comprises 3, 4 or 5 fluid flow enhancing elements.

Preferably, when there is a plurality of fluid flow enhancing elements, a portion of a first fluid flow enhancing element overlaps with a portion of a second fluid flow enhancing element, adjacent thereto.

Preferably, the path is at least 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16 or 17 mm wide at its widest point.

Preferably, the path comprises a main axis with an angle of about 10°, 15°, 20°, 25°, 26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35° 36°, 37°, 38°, 39°, 40°, 41°, 42°, 43°, 44°, 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80° to the vertical.

Preferably, the component comprises a plurality of rows of fluid flow enhancing elements wherein each said row is spaced apart along the length of the outer surface of the component.

Preferably, the plurality of rows of fluid flow enhancing elements are spaced equidistantly from each other.

Preferably, the component is a drill string component selected from the list comprising: reamer, drill pipe, drill bit, core drill bit.

When the component is a drill bit or reamer, the fluid flow enhancing element may be provided on a shank portion of the drill bit or reamer.

When the component is a drill pipe, the fluid flow enhancing element may be provided on a part of the outer surface of the drill pipe. When the component is a dedicated component, it is adapted to be fitted to the drill string at one or more locations on the drill string. Thus, the component may comprise one or more drill string attachment points.

The present invention also provides a drill string comprising a component or a plurality of components as described herein.

When the drill string comprises a plurality of components it is preferred that they be located at predetermined positions in the drill string. In this regard, the number and location of each component within the plurality of components will vary depending on the operating requirements of the user.

The present invention also provides a drilling assembly comprising a component as described herein or a drill string as described herein.

The drilling assembly may further comprise a casing wherein an annulus is defined between the casing and the drill string. Preferably, the casing is suitable for reverse circulation drilling.

Applicant has found that the combination of features of the component of the present invention, enhances the removal of fragments of drilled material created during drilling and therefore improves the drilling efficiency. Whilst the present invention is not limited to any mechanism of action, applicant understands that the component of the invention operates to:

(a) create up hole velocity during rotation;

(b) counteract the G-force placed on the fragments of drilled material to be removed; and

(c) generate a low-pressure area during rotation that lifts the fragments of drilled material into the annulus or other escape path.

According to another aspect, the present invention provides a method of drilling a hole in a substrate, the method comprising the steps of:

(i) drilling said hole with a drill string, wherein said drill string includes a component having a central axis and comprising: (a) a trailing end;

(b) a leading end; and

(c) at least one fluid flow enhancing element projecting from an outer surface of the component for enhancing fluid flow towards said trailing end, when the drill string is rotated around said axis in a direction of rotation; and

(ii) delivering a mechanical lubricant to an annulus formed around the drill string.

Preferably, the substrate is rock such as hard rock.

Preferably, the mechanical lubricant is a bead, such as a synthetic bead.

Preferably, the bead is spherical.

Preferably, the bead has a size of 100 to 1000 microns, 100-500 microns or 350-1000 microns.

Preferably, the mechanical lubricant has a specific gravity of 1 .02-1 .15. In this regard, the specific gravity of the mechanical lubricant can be adjusted to ensure that the lubricant remains in the annulus and or suspended therein for the desired time in a given method.

Advantages

Whilst not limited to the following applicant believes the present invention has a number of advantages including one or more of the following:

(a) more efficient transfer of drill cuttings;

(b) more efficient transfer of drill cuttings by increased velocity of fluid in the annulus;

(c) higher rotation speeds;

(d) improved ROP;

(e) attenuating or removing the formation of undesirable fluid flows, such as vortexes, in or around the drill string and/or parts thereof such as reamers;

(f) attenuating or removing the undesirable grinding/re-grinding of drill cuttings in the annulus by reamers and/or other parts of the drill string; (g) enables the efficient use of different drilling fluids such as mechanical lubricants; and

(h) enables the use of lower viscosity drilling fluids and hence lower operating pressures.

General

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. The invention includes all such variation and modifications. The invention also includes all of the steps and features referred to or indicated in the specification, individually or collectively and any and all combinations or any two or more of the steps or features.

Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirety by reference, which means that it should be read and considered by the reader as part of this text. That the document, reference, patent application or patent cited in this text is not repeated in this text is merely for reasons of conciseness. None of the cited material or the information contained in that material should, however be understood to be common general knowledge.

The present invention is not to be limited in scope by any of the specific embodiments described herein. These embodiments are intended for the purpose of exemplification only. Functionally equivalent products and methods are clearly within the scope of the invention as described herein.

The invention described herein may include one or more range of values (e.g., size etc). A range of values will be understood to include all values within the range, including the values defining the range, and values adjacent to the range which lead to the same or substantially the same outcome as the values immediately adjacent to that value which defines the boundary to the range.

Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. For the purposes of the present invention the terms “leading” and “trailing” when used in relation to the fluid flow enhancing element refer to positions of features relative to a direction of movement, when in use. Depending on the context herein, this direction of movement could be the direction of rotation of the drill string, such as for the first leading and first trailing edges or the direction of drilling, such as for the second leading and second trailing edges.

Other definitions for selected terms used herein may be found within the detailed description of the invention and apply throughout. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which the invention belongs.

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. In the various Figures the same reference numerals have been used to identify similar elements.

Detailed Description of the Preferred Embodiments

An embodiment of the first aspect of the present invention is a component in the form of a reamer shell, generally indicated by the numeral 10, in Figures 1 a-1 c and 2. In use, the reamer shell 10 is oriented in the drilling direction depicted by arrow 8 in the Figures. Whilst the embodiment depicts a reamer shell it will be appreciated that the component could be in the form of a separate component that does not perform the role of a reamer. Embodiments comprising other drill string components could be dedicated to creating the desired fluid flow in the annulus as described elsewhere herein e.g., a drill bit or a drill pipe.

The reamer shell 10 has a generally cylindrical body including a hollow 11 extending therethrough. The hollow 11 is centred on an axis in the form of central axis 12 around which, in use, the reamer shell 10 is rotated by a drill string (not shown) in a direction of rotation 14 (see Figure 1 b). The reamer shell 10 includes a shank 16 with a trailing end 18 that includes a first attachment means in the form of a first threaded portion 20 (see Figure 1 c) to enable the reamer shell 10 to be conveniently attached and detached from a drill string. In this regard, the reamer shell 10 can be attached to another reamer shell (see Fig 2), a drill pipe or any other component of the drill string.

On the leading end 19 of the shank 16 is a second attachment means in the form of second threaded portion 21 to enable the reamer shell 10 to be conveniently attached to and detached from a drill bit 22 (see Fig 1 c).

The reamer shell 10 further comprises a plurality of fluid flow enhancing elements in the form of three sets of foil members in the form of foils 50, 52 and 54 located on the outer surface of the shank 16. Each set 50, 52 and 54 is spaced apart along the length of the shank 16 and comprises four foils 50a-d, 52a-d and 54a-d located on, raised from and spaced equidistantly around the outer surface of the shank 16.

The spaces 110 between adjacent foils (50a-d, 52a-d and 54a-d) in each set 50, 52 and 54 defines a path for fragments of drilled material produced during the drilling process. The foils 50a-d, 52a-d and 54a-d reduce the pressure between the reamer and the inner surface of a drilled hole and enhance fluid flow away and hence the transfer of drilled material away from the drill bit 22, during use, with drilled material being transferred away from the drill bit 22 via an annulus between the reamer shell 10 and the inner surface of a drilled hole. This annulus includes the path for fragments of drilled material partially defined by spaces 110 between adjacent foils (50a-d, 52a- d and 54a-d).

As best seen in Figure 1d, the main axis 112 of the second trailing edge 105 of each foil defines an angle 1 13 of about 75-80° or 77.5° with the main vertical or longitudinal axis 116 of the reamer shell 10. The main axis 112 of the second trailing edge 105 and how angle 113 is determined is best illustrated in Figure 1 d. The angle 113 of about 75-80° or 77.5° is based on the most common drilling speed used in hard rock drilling. Flowever, the angle 113 can be varied depending on the drilling speed and other operational requirements.

Again, best shown in Figure 1d, each foil 50a-d, 52a-d and 54a-d includes an arcuate shaped head portion 60 that defines a first leading edge 63 facing the direction of rotation and a tapered, tail portion 62 that defines a first trailing edge 65 and extends away from the arcuate shaped head portion 60 and the drill bit 22.

Each foil 50a-d, 52a-d and 54a-d also defines a foil chord 101 and is located and oriented on the shank 16 such that foil chord 101 intersects a plane 103 that passes through the shank 16 at a right angle to the longitudinal axis of the shank to define an angle 118 of about 12.5°. The foil chord 101 and plane 103 and how angle 118 is determined is best illustrated in Figure 1 d. The angle 118 of about 12.5° is based on the most common drilling speed used in hard rock drilling. However, the angle 118 can be varied depending on the drilling speed and other operational requirements. The second trailing edge 105 of the tail portion 62 is straight and the second leading edge 107 of the tail portion 62 is curved or arcuate.

Each foil 50a-d, 52a-d and 54a-d includes three inserts of a relatively hard material in the form of tungsten inserts 112a-c located towards the edge of the arcuate shaped head portion 60 and seven tungsten inserts 114a-g in the trailing edge 105 of the tail portion 62 at the edge thereof. The foils 50a-d, 52a-d and 54a-d also include a plurality of relatively hard material inserts in the form of buttons 80 spread across the remainder of their main face or surface 82 of the foil. Again, this is best shown in Figure 1d.

Applicant has found that the combination of features of the present invention, such as the shape, location and orientation of foils 50a-d, 52a-d and 54a-d on the shank 16, enhances the removal of fragments of drilled material created during drilling, reduces undesirable grinding of drilled material by the reamer and lowers the risk of the drill string getting stuck during the drilling process due to high fluid pressure created between the reamer and the wall of a drilled hole. Whilst the present invention is not limited to any mechanism of action, applicant understands that the reamer shell 10 of the invention operates to reduce the pressure created by the reamer during the drilling process that is applied against the walls of the drilled hole. This is believed to reduce the likelihood of a drill string getting “locked” or stuck against the walls of the drilled hole. All of these factors work to improve ROP.