AU2018101723A4

AU2018101723A4 - Drill Rod

Info

Publication number: AU2018101723A4
Application number: AU2018101723A
Authority: AU
Inventors: Hendrik Corporaal
Original assignee: Corporaal Entpr Pty Ltd
Current assignee: Corporaal Enterprises Pty Ltd
Priority date: 2018-11-16
Filing date: 2018-11-16
Publication date: 2019-01-03
Anticipated expiration: 2026-11-16

Abstract

A dual tube drill rod for use in a drill string and a method of forming such a drill rod. The method being applied to an elongate and cylindrical pipe section 11 that has opposite first and second ends12, 13. The method including upset forging each of the first and second ends 12, 13 to increase the wall thickness of the pipe section 11 at each of the first and second ends 12, 13 relative to the wall thickness of the pipe section 14 between the first and second ends 12, 13. Machining the first and second ends 12, 13 to form end connections 15, 16 to form an outer pipe 10. The end connections 15, 16 facilitating connection of an outer pipe 10 to another outer pipe 10 of another drill rod. Inserting an inner tube 33 into the pipe section 11. Fig2

Description

DRILL ROD

Technical Field [0001] The present invention relates to an extension rod in the form of a dual tube drill rod for use in extension drilling arrangements employed in the water boring and mining industries and for example in drilling operations commonly known as reverse cycle [R.C] drilling and reverse flood drilling. In dual tube drill rods, drill cuttings are brought to the ground surface inside the inner tube, as compared to being brought to the ground surface between the outside of a single tube drill pipe and the facing surface of the bore being drilled.

[0002] Extension drilling arrangements employ drill strings that are formed from a plurality of drill rods and drive the drill strings to drill a bore using a surface mounted drilling rig. The present invention relates to a particular form of dual tube drill rod that is considered to provide benefits over existing dual tube drill rods.

Background of Invention [0003] A reference herein to prior art is not to be taken as an admission that that art was known or was part of the common general knowledge as at the priority date of any of the claims.

[0004] Drill strings relevant to the present invention are formed by the connection together of a plurality of dual tube drill rods. A dual tube drill rod is a relatively short 20 length of rod that includes connection arrangements at each end for connecting to other dual tube drill rods to form an elongate drill string. The drill rods have an outside pipe and a coaxial inside tube and the drill rods connect together so as to form a continuous outer pipe and a continuous inner tube forming both a continuous central conduit within the tube and a continuous annular passage between the tube 25 and the outer pipe. The length of a drill string is usually progressively increased by adding drill rods to the drill string so that the depth of drilling can be progressively increased. The addition of drill rods is completed at the surface being drilled by the disconnection of the drilling rig to the drill string and by the addition of a new drill rod to the upper end of the drill string. Thereafter, the drilling rig is reconnected to the

2018101723 16 Nov 2018 new drill rod and drilling can recommence until such time as a further drill rod needs to be connected to the drill string.

[0005] Current dual tube drill rods are formed by welding end connections to each end of a pipe or pipe section (often called a “middle pipe”) to form an outer pipe and inserting an inner tube. The end connections are high tensile threaded connectors (or “tool joints”). The outer pipe has a profile on its inner or internal surface for locating an inner tube.

[0006] The current approach of welding end connections to each end of a pipe section has been in place for many years and is the standard method of dual tube drill 10 rod manufacture. However, typically manufacturers of dual tube drill rods are not accredited by any authorised body and there are no regulations or standards that are required to be complied with. This causes problems, because drill strings can be subjected to very high internal pressures, generated by heated compressed air (for example up to 1000 Psi) and oil. The drill rods of the drill string can be categorised as 15 pressure vessels and are subjected to wear when in use, due to rotation of the drill rods in a very abrasive environment.

[0007] It is known for example, for drill rod connections to have been welded incorrectly using incorrect welding procedures for particular metals resulting in subquality weld connections. This can arise due to operator error or inexperience, and 20 incorrect metal materials being used for the threaded connections. Poor welding or material selection can also result in shrinkage and/or distortion of the pipe section and end connections during manufacture of the drill rods and/or during their use. Poor welding of a connection to a pipe section often requires the drill rod to be reworked or results in failure of the drill rod during use. Failure during use is problematic firstly 25 because of the risk of injury to mining personnel and secondly because failure can occur deep within a drilled bore, and failure requires retrieval of the failed drill rod for drilling to continue. This can result in major disruption to the drilling process with subsequent major financial losses as a result of drilling downtime.

[0008] The present invention seeks to provide a drill rod and a drill string that 30 provides improvements compared to existing dual tube drill rods and drill strings.

2018101723 16 Nov 2018

Summary of Invention [0009] The present invention provides a method of forming a dual tube drill rod for use in a drill string, the method being applied to an elongate and cylindrical pipe section that has opposite first and second ends the method including,

a. upset forging each of the first and second ends to increase the wall thickness of the pipe section at each of the first and second ends relative to the wall thickness of the pipe section between the first and second ends,

b. machining the first and second ends to form end connections to form an outer pipe, the end connections facilitating connection of an outer pipe to another outer pipe of another drill rod

c. inserting an inner tube into the pipe section.

[0010] The present invention also provides a dual tube drill rod for use in a drill string, the drill rod comprising;

a. an elongate and cylindrical outer pipe that has opposite first and second ends, an inner tube within the pipe, the first and second ends of the outer pipe being upset forged so that the wall thickness of each of the first and second ends is greater than the wall thickness of the pipe section between the first and second ends, and

b. the first and second ends being machined to form end connections that facilitate connection of the formed outer pipe to an outer pipe another drill rod.

[0011] Still further, the present invention also provides drill string comprised of dual tube drill rods formed according to the method above, or in accordance the drill rod described above.

[0012] The outer pipe of a drill rod according to the invention advantageously is formed from a single piece of cylindrical pipe. Each of the opposite ends of the pipe is upset forged in a manner to allow machining of the opposite ends to form the connection (usually a threaded profile) required for one drill rod to connect to a second drill rod. Upset forging consists of heating the cylindrical pipe until it becomes pliable and then applying force to each end with mandrels to shorten the length of the

2018101723 16 Nov 2018 pipe and to thicken the ends. Wrenching (spanner flats) can be milled onto the outside of the ends if needed. By forming the outer pipe of the drill rod in this manner, the outer pipe becomes a weld-free rod, or a single-piece outer pipe, so that the drawbacks discussed above that arise as a result of welds that are required in prior art multiple-piece outer pipe, are avoided. This includes that weaknesses formed at weld regions are eliminated and that a single-piece outer pipe can be formed, such as from heat treated alloy steel.

[0013] Moreover, the single-piece outer pipe that is formed by the present invention can be heat treated once fully formed, and along its full length. In prior art 10 outer pipes that incorporate welds, heat treatment is required to be performed on the respective parts of the outer pipe, prior to the parts being welded together. This is because heat treatment can affect a weld that has been made between two components. Likewise however, welding parts that have already been heat treated can also affect the characteristics of the heat treatment that has taken place prior to 15 welding, particularly in the vicinity of the weld connection.

[0014] A drill rod according to the present invention also eliminates issues of subquality welding or inappropriate welding due to the absence of a need for welded connections. The present invention further advantageously produces an outer pipe from a single material and any shrinkage and/or distortion of the outer pipe can be 20 foreseen given that the material of the outer pipe is uniform and so that the entire outer pipe has the same material properties or characteristics.

[0015] The drill rod according to the invention thus can advantageously form a more reliable drill rod in terms of reduced failure and as will be apparent from the discussion above, a reduction in the likelihood of failure can be advantageous in 25 reducing the likelihood of injury to personnel, reducing drilling downtime and thus reducing financial loss due to drilling downtime.

[0016] In some forms of the invention, the creation of wall thicknesses at the first and second ends of the outer pipe that are greater than the wall thickness of the central or middle pipe section between the first and second ends (hereinafter the 30 “central pipe section”), is achieved by the first and second ends having an inside diameter which is less than the inside diameter of the central pipe section. In these

2018101723 16 Nov 2018 forms of the invention, the outside diameter of the outer pipe can be substantially constant throughout each of the first and second ends and the central pipe section. “Substantially constant” allows for variations in the outside diameter of the outer pipe, such as in the order of millimetres. Thus, in these forms of the invention, the upset forging which is applied to each of the first and second ends causes a reduction in the inside diameter at the first and second ends, but not in an increase in the outside diameter of those ends, or at least with only a very small increase in the outside diameter. If there is an increase in the outside diameter, the first and second ends can be machined in order to ensure that the entire outer pipe has an outside diameter of 10 the required dimension, which is usually required to be a substantially constant outside diameter.

[0017] A reduction in the inside diameter at the first and second ends without a change in the outside diameter means that, as required, the first and second ends increase in wall thickness. This requires that the length of the cylindrical pipe section 15 before upset forging is reduced to allow material flow within the first and second ends to increase the wall thickness. The reduction in length is proportional to the increase in wall thickness of the first and second ends and advantageously, this increase in wall thickness allows the first and second ends to be machined as required to form the relevant end connections and the wall thickness increase gives the ends more 20 strength than if there were no increase. The increase can be relatively minor and in the region of about 1 to 2 mm.

[0018] Advantageously, it also expected that by upset forging the first and second ends, the mechanical properties of the outer pipe at those ends is refined by a reorienting of the grain flow of the material of the drill rod into the shape of the tool joint.

The result is expected to be an outer pipe which is inherently stronger than that which has welded connections.

[0019] The machining that is applied to the first and second ends of the outer pipe can be to form respective male and female threads. Thus, one of the first and second ends is machined on the inside surface thereof to form an inside thread, while the 30 opposite end is machined to form an outside thread on the outside surface thereof.

The machining can also include the formation of a seat for seating or locating one end of an inner tube..

2018101723 16 Nov 2018 [0020] The upset forging can be applied at a sufficient load to create the required wall thickness of the first and second ends that allows the machining to proceed. Advantageously, the wall thickness at the first and second ends will not affect the wall thickness of the central pipe section, so that the wall thickness at the central pipe section can be retained at the desired thickness and the wall thickness at the first and second ends can be created as required by suitable load or pressure applied through the upset forging process. This means that the wall thickness of the central pipe section does not have to be the same as the wall thickness of the first and second ends and this can mean that an outer pipe according to the present invention can be 10 of lighter weight than prior art drill rods that are not upset forged and that therefore require the central pipe section to have the same wall thickness as the first and second ends.

Brief Description of Drawings [0021] In order that the invention may be more fully understood, some 15 embodiments will now be described with reference to the figures in which:

[0022] Figure 1 is a cross-sectional view of a drill rod which has been formed according to the present invention.

[0023] Figure 2 is a sectional view of a drill string incorporating two connected drill rods which have been formed according to the present invention.

Detailed Description [0024] Figure 1 is a cross-sectional view of an outer pipe which has been formed according to the present invention for use in forming a dual tube drill rod. The outer pipe 10 is formed from a pipe section 11 and has opposite first and second ends 12 and 13 and a central pipe section 14. The outer pipe 10 would normally be of a length in the order of about 6m (although different sizes are available) but is shown broken through the centre so that the first and second ends 12 and 13 can be clearly illustrated. It is to be appreciated that the central pipe section 14 is of substantially constant outside diameter and of substantially constant wall thickness.

[0025] In the outer pipe 10 as formed, the central pipe section 14 is of thinner wall 30 thickness and greater inside diameter than compared to the first and second ends 12

2018101723 16 Nov 2018 and 13. The outer pipe 10 has been formed by upset forging the original pipe section

11, which, prior to upset forging, was a cylindrical elongate pipe of constant wall thickness. The upset forging applied to the pipe section 11 causes the length of the pipe section 11 to shorten and for the opposite ends to thicken, so that the opposite ends of the pipe section 11 form the respective first and second ends 12 and 13.

[0026] Figure 1 shows the three different inside diameter dimensions IDu, ID12 and ID13 which correspond to the inside diameter (ID) of the respective central pipe section 14 and the first and second ends 12 and 13. In the outer pipe 10, IDi₂and IDi₃are equal and are less than IDu. Thus, as shown in Figure 1, ID₁₂=ID₁₃< IDu Thus, the upset forging that is applied to each of the first and second ends 12 and 13 of the pipe section 11 causes the inside diameter at each of the first and second ends 12 and 13 to reduce. The upset forging also causes the wall thickness T of the pipe section 11 to increase at each of the first and second end sections 12 and 13 relative to the central pipe section 14. Thus, as shown in Figure 1, Ti₂=Ti₃<Tn.

[0027] As shown in Figure 1, the first and second ends 12 and 13 have been formed to create threads, so that a first outer pipe 10 can connect to a second outer pipe 10. In Figure 1, the first end 12 has been machined to create an internal thread 15, while the second end 13 has been formed to create an external thread 16. The ability to create opposite first and second ends 12 and 13 of the pipe section 11 that have initially a thicker wall thickness than the central pipe section 14 between the opposite ends advantageously facilitates machining of the first and second ends 12 and 13 in the manner shown in Figure 1 to create the illustrated threads. This arrangement also means that the wall thickness of the central pipe section 14 between the first and second ends 12 and 13 can be thinner so that, subject to capacity requirements of the outer pipe 10, a wall thickness suitable for the opposite ends to be machined does not need to be maintained throughout the entire length of the outer pipe 10.

[0028] It can be seen in Figure 1, that the wall thickness of the outer pipe 10 transitions from the first and second ends 12 and 13 to the central section 14 at shoulders 17 and 18. It can be seen that the shoulders 17 and 18 provide for an angled transition from the reduced inside diameters at the first and second ends 12 and 13 to the larger inside diameter at the central pipe section 14, rather than an

2018101723 16 Nov 2018 abrupt transition. The angled transition is preferred over an abrupt transition as the latter might affect flow of drilling material through the outer pipe 10.

[0029] The first end 12 has also been machined to form a seat 20 for seating an end of an inner tube, or for supporting a section of an inner tube. An annular bush can be seated at the seat 20, or a bearing or other suitable locator. The inclusion of an inner tube (which is not shown in Figure 1) forms the outer pipe 10 into a reverse circulation dual tube drill rod whereby a dual wall pipe is formed for reverse circulation of drilling fluids for example.

[0030] Figure 2 illustrates a portion of a drill string 30 according to the invention, in which a pair of drill rods 31 and 32, which employ the same or similar outer pipe 10 of Figure 1, have been threadably connected together and a section of the drill string has been cut away to show an inner tube 33 located within the drill string 30. In Figure 2, a bush 34 is seated within the first end 35 of the drill rod 32 and extending through the bush 34, is the inner tube 33. The inner tube 33 can be of any conventional form.

The bush 34 includes longitudinal openings (not visible in Figure 2) that extend in the longitudinal direction of the drill string 30, to allow flow that occurs through the drill string 30 to flow through the bearing 34.

[0031] It can clearly be seen in Figures 1 and 2 that the respective drill rods of those figures are weld-free, single-piece drill rods. This results in the benefits that have been outlined hereinbefore.

[0032] Where any or all of the terms comprise, comprises, comprised or comprising are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, 25 steps or components.

[0033] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope of the present invention.

2018101723 16 Nov 2018 [0034] Future patent applications may be filed in Australia or overseas on the basis of or claiming priority from the present application. It is to be understood that the following provisional claims are provided by way of example only, and are not intended to limit the scope of what may be claimed in any such future application.

Features may be added to or omitted from the provisional claims at a later date so as to further define or re-define the invention or inventions.

Claims

1. A method of forming a dual tube drill rod for use in a drill string, the method being applied to an elongate and cylindrical pipe section that has opposite first and

5 second ends, the method including,

b. machining the first and second ends to form end connections to form an

10 outer pipe, the end connections facilitating connection of an outer pipe to another outer pipe of another drill rod

c. inserting an inner tube into the pipe section.

2. A method according to claim 1, the increased the wall thickness of the pipe section at each of the first and second ends by the upset forging causing the inside

15 diameter of the pipe section at each of the first and second ends to be reduced.

3. A method according to claim 1 or 2, further including heat treating the outer pipe along its full length.

4. A method according to any one of claims 1 to 3, further including machining the outside surface of the first and second ends to a standard drill rod outside

20 diameter.

5. A method according to any one of claims 1 to 4, further including machining the inside surface of the first end to include a thread.

6. A method according to any one of claims 1 to 5, further including machining the outside surface of the second end to include a thread.

25

7. A method according to any one of claims 1 to 6, further including machining the inside surface of the first end to include a seat for seating one end of the inner tube.

2018101723 16 Nov 2018

8. A method according to claim 7, the seat being for seating a bearing applied at the end of the inner tube.

9. A drill rod formed according to the method of any one of claims 1 to 8.

10. A dual tube drill rod for use in a drill string, the drill rod comprising an elongate and

5 cylindrical outer pipe section that has opposite first and second ends, an inner tube within the pipe, the first and second ends of the outer pipe being upset forged so that the wall thickness of each of the first and second ends is greater than the wall thickness of the pipe section between the first and second ends and the first and second ends being machined to form end connections that facilitate

10 connection of the formed outer pipe to an outer pipe of another drill rod.

11. A drill rod according to claim 10, the drill rod being heat treated along its full length.

12. A drill rod according to claim 10 or 11, the inside diameter of the pipe section at the first and second ends being reduced compared to the inside diameter of the

15 pipe section between the first and second ends.

13. A drill rod according to any one of claims 10 to 12, the outside surface of the outer pipe being of substantially constant outside diameter and the inside surface of variable diameter including that the inside diameter between the first and second ends is generally greater than the inside diameter at each of the first and second

20 ends.

14. A drill rod according to any one of claims 10 to 13, the outer pipe being machined at the inside surface of the first end to include a thread.

15. A drill rod according to any one of claims 10 to 14, the outer pipe being machined at the outside surface of the second end to include a thread.

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16. A drill rod according to any one of claims 10 to 15, the outer pipe being machined at the inside surface of the first end to include a seat for seating one end of the inner tube.

17. A drill string comprised of drill rods formed according to anyone of claims 1 to 9.

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18. A drill string comprised of drill rods according to anyone of claims 10 to 18.