AU2009201205A1

AU2009201205A1 - Saver sub clamp

Info

Publication number: AU2009201205A1
Application number: AU2009201205A
Authority: AU
Inventors: Bruce William Haines; Todd Andrew Haines
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-03-28
Filing date: 2009-03-27
Publication date: 2009-10-15

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "SAVER SUB CLAMP" The following statement is a full description of this invention, including the best method of performing it known to me/us: TITLE: SAVER SUB CLAMP BACKGROUND OF THE INVENTION Field of the Invention THIS INVENTION relates to a saver sub clamp. 5 The invention particularly relates, but is not limited, to a saver sub clamp which can be used in drilling apparatus incorporating rotary drill strings, where drill pipes, rods or tubes are screw threadably connected to each other. Throughout the specification, the term "drill rods" shall be used to 10 include drill pipes, drill rods, drill tubes or the like. Prior Art Conventionally rotary drill strings have a series of components or drill rods which are coupled together by a male coupling member (or pin), which couples with a complementary female member (or box), to couple adjacent 15 drill rods to each other. The male coupling (or pin) has a screw threaded portion, which has an outer surface which diverges outwardly having regard to a longitudinal axis of the rotary drill string; and this male coupling engages with a socket in the female coupling (or box) having a complementary internal screw threaded surface which converges inwardly having regard to 20 the longitudinal axis. In rotary drill strings, it is well known to have a rotary head coupling which is involved in a drilling process wherein, when drilling a blast hole in a mining procedure deeper than 20 metres, a drill rod is drilled down into the ground. A second drill rod is coupled to the rotary head and then coupled to 25 the first drill rod in the ground, and the second drill rod is drilled to depth.

2 This process may continue until up to, e.g., seven drill rods are drilled down to the desired depth. The drill rods are coupled together using the male and female couplings described above which have coarse tapered threads. These 5 threads wear out on the drill rods and on the rotary head. However, the rotary head threads wear out faster than the drill rod threads, because it is necessary for the rotary head threads to couple with every thread on top of the drill rods as they are used in the drilling process described above. The rotary head is typically mounted on a chain supported on a 10 support frame, which is part of a mast which may extend 50 to 60 feet above the ground. The chain is capable of reciprocating motion up or down the mast, and it may be driven by a sprocket drive. The rotary head typically includes a hydraulic motor for rotating the threaded coupling to an adjacent drill rod; so that when a drill rod is driven into the ground, rotary torque is 15 provided by the hydraulic motor and downward axial force is provided by the rotary head moved down the mast by the chain. The rotary head, when connected to a drill rod, has a top sub or drill collar, which has screw threaded projections at each end. One end projection is screw threadably engaged with a screw threaded socket on the rotary 20 head; and the other end projection is screw threadably engaged with an internal screw threaded surface of the box of a saver sub, which interconnects the top sub to an adjacent drill rod. Thus the saver sub is a tubular drill collar having a coarse internal thread at each end. When the saver sub internal thread wears out, there is a risk that the 3 drill rods will not be able to be gripped by the saver sub, and thus it is possible for an expensive set of drill rods to be lost down a hole in the ground with no chance of retrieval. The saver sub is a consumable component that is usually changed 5 every 4 to 6 weeks in use. Currently the saver sub is coupled to the top sub, tightened up, and then drive tags (which are normally strips of flat bar or round bar approximately 50mm long) are welded onto the top sub and the saver sub. This procedure requires a boilermaker to cut off the old drive tags and weld on the new drive tags. This can be a time consuming process; and 10 there is also occasional damage to the drill electrical system due to incorrect earth connecting procedures; and there is often a delay to get a boilermaker down to the drilling location. There is also always a risk of a fire being started during the welding process. In the petroleum industry, there exists a saver sub clamp that 15 connects a saver sub to a rotary head. The saver sub clamp operates by clamping two halves of a sleeve fitted with break out dies or gripping portions on an internal surface thereof of each half over the top sub and saver sub. Torque is transmitted through the clamp. SUMMARY OF THE PRESENT INVENTION 20 It is, therefore, an object of the present invention to provide a saver sub clamp which overcomes, or at least reduces, the above mentioned disadvantages of the prior art. Other preferred objects of the present invention will become apparent from the following description.

4 In one aspect, the present invention resides in a saver sub clamp, suitable for rotary drill strings, including: a clamp body mountable on a top sub of a rotary drill string and operable to surround an adjacent portion of a saver sub when operably 5 engaged with the top sub; a plurality of bores through the clamp body; and a plurality of clamping members, received in at least some of the bores, and operable to be advanced in an inward direction for clamping engagement with the adjacent portion of the saver sub, to enable releasable 10 connection between the top sub and the saver sub. Preferably, the bores extend substantially radially through the clamp body; and the clamping members are advanced in a substantially inward direction for the clamping engagement. 15 Preferably, the clamp body is an annular clamping ring, machined or otherwise manufactured from high-tensile steel and / or other suitable high strength material(s). Preferably, at or adjacent one end of the clamp ring, an inwardly directed flange is engagable in a complementary circumferential recess 20 about the top sub at the end thereof adjacent the saver sub; and preferably the clamp ring and / or annular flange are welded, or otherwise non releasably-mounted, to the top sub. Preferably, the plurality of bores through the clamp ring are screw threaded to receive complementary studs or screws (e.g., Allen-screws) 5 which comprise, or are incorporated in, the clamping members. The bores may be of stepped profile, having an enlarged diameter adjacent the circumferentially outer face of the clamp ring, to receive the heads of the studs or screws and to enable suitable tools to engage the heads of the 5 studs or screws. The inwardly directed ends of the shanks of the studs or screws may bear directly on the external (preferably circumferential) face(s) of the adjacent portion of the saver sub; or may be provided with hardened balls, ball bearings and / or buttons adapted to force their way into the adjacent 10 portion of the saver sub. The inwardly directed ends of the shanks of the studs or screws may engage outer faces of respective clamping dies, each of which have clamping faces engagable with the adjacent portion of the saver sub, the clamping faces being of, e.g., serrated, wave-like, or other suitable profile to 15 releasably engage the adjacent portion of the saver sub. Axially extending bores may be provided in an annular end face of the clamping ring, the axially extending bores being preferably screw threaded to receive locking grub screws engagable with the shanks of the studs or screws and / or the clamping dies when the saver sub is in non 20 rotatable clamped engagement with the clamp ring, and thereby the top sub. In a second aspect, the present invention resides in a rotary drilling string where a top sub and a saver sub are non-rotatably, releasably, coupled by a saver sub clamp of the present invention as hereinbefore described.

6 In a third aspect, the present invention resides in a method of coupling a top sub to a saver sub for a rotary drilling string employing the saver sub clamp of the present invention as hereinbefore described. BRIEF DESCRIPTION OF THE DRAWINGS 5 To enable the present invention to be fully understood, preferred embodiments of the present invention will now be described with reference to the accompanying drawings, in which: FIG. 1 is a perspective view of a portion of a rotary drill string fitted with a saver sub clamp in accordance with a first embodiment of the present 10 invention; FIG. 2 is an "exploded" view corresponding to FIG. 1; FIG. 3 is a perspective view of the clamp ring for the saver sub clamp of the first embodiment; FIG. 4 is a front elevational view thereof; 15 FIG. 5 is a sectional side view thereof taken on line A-A on FIG. 4; FIG. 6 is a sectional side view showing clamping engagement between the saver sub and the saver sub clamp; FIG. 7 is a side elevational view of one of the studs used in association with the clamp ring; 20 FIG. 8 is a perspective view of a portion of a rotary drill string fitted with a sub saver clamp in accordance with a second embodiment of the present invention; FIG. 9 is an "exploded" view corresponding to FIG. 8; FIG. 10 is a perspective view of a portion of a rotary drill string fitted 7 with a saver sub clamp in accordance with a third embodiment of the present invention; FIG. 11 is an "exploded" view corresponding to FIG. 10; FIG. 12 is a "further exploded" view corresponding to FIG. 10; 5 FIG. 13 is a perspective view of a saver sub clamp in accordance with a fourth embodiment; FIG. 14 is an "exploded" view corresponding to FIG. 13; FIG. 15 is a perspective view of a saver sub clamp in accordance with a fifth embodiment; and 10 FIG. 16 is an "exploded" view corresponding to FIG. 15. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In each of the preferred embodiments to be hereinafter described with reference to the accompanying drawings, the rotary drill string 10 has a rotary head 11, mounted on a drilling mast (not shown) and arranged for 15 substantially vertical travel, controlled by a chain (also not shown) on the drilling mast. The rotary head 11, has a hydraulic drive motor (not shown) connected to a drive pump and suitable operating controls by hydraulic pumps and / or hoses (not shown). 20 The hydraulic drive motor in the rotary head is connected (e.g., via a reduction gearbox) to a driving box 12 (rotatably journalled in the rotary head), the driving box 12 having tapered internal screw threads 13. A top sub 14 has a cylindrical body 15, with a driven pin 16, with tapered screw threads 17, engagable with the driving box 12; and a driving 8 pin 18, with tapered screw threads 19. A circumferential recess 20 is provided around the body 15 of the top sub 14 adjacent the base of the driving pin 18. Saver sub 21 has a tubular body 22, with a pair of planar faces 23 (on 5 diametrically opposed sides of the tubular body 22), the planar faces 23 being engagable by deck tools (not shown), for connection/release of the saver sub 21 to the top sub 14 and / or to the drill rod(s) 30. The saver sub 21 has a driven box 24 and driving box 25, with respective tapered internal screw threads 26, 27. The driven box 24 of the 10 saver sub 21 is releasably connectable to the driving pin 18 of the top sub 14; and the driving box 25 is releasably connectable to a drill rod pin 28, with tapered external screw threads 29, at one end of a drill rod 30. Preferably, at least the screw threads 19, 26, 27 and 29 of the driving pin 18 of the top sub 14, the driven box 24 and driving box 25 of the saver 15 sub 21, and of the drill rod pin 28, are two- or multiple-start threads, e.g., of the type known as "Mindrill M 6" threads and disclosed in International Publication WO 02/08566 (issued on International Application PCT/AU01/00895) and / or Australian Design Registration Publications AU 148915 S and AU 149662 S, all in the name of Todd Andrew Haines. 20 While it is preferred that the tapered screw threads 13 and 17 of the driving box 12 on the rotary head and driven pin 16 on the top sub 14, respectively, are of the same profile as hereinbefore described, these threads may be of an alternative profile, e.g., BECO threads. The releasable connection of the saver sub 21 to the top sub 14 of the 9 rotary drilling string 10, using a saver sub clamp 140 of the first embodiment of the present invention, will now be described with reference to FIGS. 1 to 7. The saver sub clamp 140 has a clamp ring 141, e.g., machined from high tensile steel with respective annular end faces 142, 143, cylindrical 5 outer face 144 and cylindrical inner face 145, the inner face 145 defining a central bore 146 of a diameter just slightly larger than the external diameter of the saver sub 21. An integral, inwardly-directed flange 147 is dimensioned to engage the circumferential recess 20 provided around the body 15 of the top sub 14. 10 A plurality (e.g., in this example, twelve) of radial bores 148 extend through the body of the clamp ring 141, the radially extending bores 148 being provided at equal angular spacings in the clamp ring 141 and being of "stepped" configuration, e.g., see FIGS. 3 and 5 where the radially extending bores 148 are internally screw-threaded. (The screw threads being omitted 15 from the drawings for clarity.) Each radially extending bore 148 is adapted to receive a clamping member 149 in the form of a stud 150 having a hexagonal head 151 and a screw threaded shank 152. (The screw threads being complementary to the screw threads of the radially-extending bores 147 and also omitted from the 20 drawings for clarity.) The distal (or inner) ends 153 of the shanks 152 are provided with stainless steel ball bearings or tungsten carbide buttons 154 adapted to engage, and indent, the outer face of the body 22 of the saver sub 21, when coupled to the top sub 14 and releasably secured thereto by the saver sub clamp 140.

10 The outer ends of the radially extending bores 148 will be dimensioned to enable engagement of the respective heads 151 of the studs 150 by, e.g., sockets fitted to pneumatic or hydraulic power tools to drive the clamping members 149 into, and out of, engagement with the body 22 of the 5 saver sub 21. A circumferential safety groove 31 may be provided around the body 22 of the saver sub 21 - see FIG. 2. The safety groove 31 is provided intermediate the end face of the driven box 24 and the portion of the body 22 normally engaged by the clamping members 149 when the saver sub 21 is 10 coupled and clamped to the top sub 14. If any of the clamping members 149 inadvertently work loose, and the saver sub 21 rotates relative to the top sub 14 in a de-coupling direction, the ball bearings or buttons 154 at the ends 153 of the shanks 152 of the studs 150 will engage the safety groove 31 and prevent further de-coupling rotation. 15 The clamp ring 141 of the saver sub clamp 140 will be mounted onto the top sub 14, with the flange 147 engaged with the circumferential recess 20 about the body 15 of the top sub 14 and will be welded or otherwise securely mounted thereto. This will be effected under controlled conditions in the factory to ensure that the clamp ring 141 cannot inadvertently become 20 released from the top sub 14. While it is possible that the clamp ring 141 could be manufactured integrally with the top sub 14, this would require complex manufacturing techniques including difficult machining and possibly less effective machining/hardening of the threads 19 on the driving pin 18 of the top sub 11 14. FIGS. 8 and 9 illustrate the releasable connection of the saver sub 21 to the top sub 14 of the rotary drilling string using a saver sub clamp 240 of the second embodiment of the present invention. 5 The clamp ring 241 of the saver sub clamp 240 will be of substantially identical configuration to the clamp ring 141, except that the radial bores 248 are of uniform diameter throughout their length and are adapted to receive clamping members 249 in the form of clamping screws 250 with hexagonal sockets 251 (at the outer ends of the shanks 252) for engagement by 10 complementary Allen-keys. The distal (or inner) ends 253 of the shanks 252 may be provided with the stainless steel ball bearings or tungsten carbide buttons 254; or these may be omitted and the distal (or inner) ends 253 of the clamping screws 250 may simply bear on the outer face of the body 22 of the saver sub 21. 15 NB: It is not possible to generate the same torque, and thereby clamping force, with the screws 250 of the second embodiment compared with the studs 150 of the first embodiment. Referring to the third embodiment of FIGS. 10 to 12, the clamp ring 341 of the sub saver clamp 340 is modified from the clamp ring 241 of the 20 second embodiment by the provision of respective axially extending bores 355 from the end face 343 of the clamp ring to the radial bores 548. Each clamping member 349 includes a clamping screw 350 where the inner end 353 of each screw 350 engages an outer face 356 of a respective clamping die 357 having a patterned, e.g., serrated or grooved clamping face 12 358 to engage the outer face of the body 22 of the saver sub 21. Locking countersunk washers 359 are provided in each axially extending bore 355 to lock the clamping screws 350 against release when the saver sub 21 is coupled to the top sub 14. The countersunk washers 359 5 are retained by tapered socket-head screws (not shown.) When a drill rod 30 is to be replaced in the drill string 10, the drill rod 30 is uncoupled from the saver sub 21 and racked away e.g. in a carousel. The studs 150, screws 250, 350 are rotated to move radially outwardly, relative to the clamping ring 141, 241, 341, and thereby the body 22 of the 10 saver sub 21 to allow the saver sub 21 to be unscrewed from the top sub 14. The saver sub 21 is rotated through 1800 relative to the top sub 14; the drill rod pin 28 of the new drill rod 30 is rotatably connected to the "fresh" driving box 25 (formerly the driven box 24) of the saver sub 21; and the "fresh" driven box 24 (formerly the driving box 25) of the saver sub 21 is 15 connected to the driving pin 18 of the top sub 14. The studs 150, screws 250, 350 are torqued (tightened) up and drilling can recommence. In this manner, the wear on individual screw threads, particularly the screw threads in the respective boxes 24, 25 of the saver sub2l, is more evenly spread across the threads to minimise thread wear and maximise the 20 life of the pin threads on the drill rod pins 28 of the drill rods 30. FIGS. 13 and 14 illustrate the fourth embodiment, where the screws 350 in uniform diameter radial bores 348 of the saver sub clamp 340 of the third embodiment are replaced by studs 450 in "stepped" radial bores 448 in the clamp ring 441 of saver sub clamp 440.

13 The inner ends 453 of the shanks 452 of the studs 450 engage the outer ends 456 of respective clamping dies 457, each having a "jaw-like" clamping face 458. The clamping dies 457 are of substantially T-section in end view and 5 are received in complementary axial grooves or guides 461 in the inner face 445 of the clamp ring 441. The axial bores 455, extending from the end face 453 of the clamp ring 441, are arranged so that the countersunk washers 459 are received in recesses 460 in the outer ends 456 of the clamping dies 457. The clamping 10 dies 457 are releasably retained in the axial grooves or guides 461 by the studs 450 and countersunk washers 459. The flange 457 is engaged with the recess 20 on the top sub 14, and the saver sub clamp 440 operates in the manner of the clamps 140, 240, 340 hereinbefore described. 15 FIGS. 15 and 16 illustrate a fifth embodiment, where the saver sub clamp 540 has a clamp ring 541 and studs 550 of the same configuration as the clamp rings 141 and studs 150 of the saver sub clamp 140 of the first embodiment illustrated in FIGS. 1 to 7. Hardened steel circular jaws 554 have circular, disc-like heads 562, 20 and spigots 563 are engaged in bores 564 in the inner (or distal) ends 553 of the shanks 552 of the studs 550. Each circular jaw 554 has a "serrated" clamping face 558 to engage the outer face of the body 22 of the saver sub 21 when the clamp ring 541 is mounted on the top sub 14 as hereinbefore described.

14 The studs 550 are selectively rotated to urge the clamping faces 558 of the tungsten carbide buttons 554 into, or out of, engagement with the body 22 of the saver sub 21. It will be readily apparent to the skilled addressee that the buttons 554 5 can be manufactured from other high strength materials, including metals, ceramics, polymers and / or mixtures of same. As the clamp rings 141, 241, 341, 441, 541 of the saver sub clamps 140, 240, 340, 440, 540 are fitted and secured to the top subs 14 in the factory, a high degree of mounting accuracy can be achieved; a skilled boiler 10 maker is not required to remove/replace the saver sub clamps; and the economic lives of the top subs 14 (and the saver subs 21) is increased. Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention. 15 20

Claims

1. A saver sub clamp, suitable for rotary drill strings, including: a clamp body mountable on a top sub of a rotary drill string and operable to surround an adjacent portion of a saver sub when operably engaged with the 5 top sub; a plurality of bores through the clamp body; and a plurality of clamping members, received in at least some of the bores, and operable to be advanced in an inward direction for clamping engagement with the adjacent portion of the saver sub, to enable releasable 10 connection between the top sub and the saver sub.

2. A saver sub clamp, as claimed in Claim 1, wherein: the bores extend substantially radially through the clamp body; and the clamping members are advanced in a substantially inward direction for the clamping engagement. 15

3. A saver sub clamp, as claimed in Claim 1 or Claim 2, wherein: the clamp body is an annular clamping ring, which is machined or otherwise manufactured from high-tensile steel and / or other suitable high strength material(s).

4. A saver sub clamp as claimed in Claim 3, wherein: 20 at or adjacent one end of the clamp ring, an inwardly directed flange is engagable in a complementary circumferential recess about the top sub at the end thereof adjacent the saver sub; and the clamp ring and / or annular flange are welded, or otherwise non releasably-mounted, to the top sub. 16

5. A saver sub clamp as claimed in Claim 3 or Claim 4, wherein: the plurality of bores through the clamp ring are screw-threaded to receive complementary studs or screws which comprise, or are incorporated in, the clamping members. 5

6. A saver sub clamp as claimed in Claim 5, wherein: the plurality of bores are of stepped profile, each having an enlarged diameter adjacent the circumferentially outer face of the clamp ring, to receive heads of the studs or screws and to enable suitable tools to engage the heads of the studs or screws. 10

7. A saver sub clamp as claimed in Claim 5 or Claim 6, wherein: inwardly directed ends of shanks of the studs or screws bear directly on external (optionally circumferential) face(s) of the adjacent portion of the saver sub; or are provided with hardened balls, ball bearings and / or buttons adapted to force their way into the adjacent portion of the saver sub. 15

8. A saver sub clamp as claimed in Claim 7, wherein: the inwardly directed ends of the shanks of the studs or screws engage outer faces of respective clamping dies, each of which have clamping faces engagable with the adjacent portion of the saver sub, the clamping faces being of serrated, wave-like, or other suitable profile to 20 releasably engage the adjacent portion of the saver sub.

9. A saver sub clamp as claimed in any one of Claims 5 to 8, wherein: axially extending bores are provided in an annular end face of the clamping ring, the axially extending bores each being screw-threaded to receive respective locking grub screws engagable with the shanks of the 17 studs or screws and / or the clamping dies, when the saver sub is in non rotatable clamped engagement with the clamp ring, and thereby the top sub.

10. A rotary drilling string incorporating a top sub and a saver sub which are non-rotatably and releasably coupled by a saver sub clamp as claimed in 5 any one of Claims 1 to 9.

11. A saver sub clamp, substantially as hereinbefore described, with reference to FIGS. 1 to 7; or FIGS. 8 and 9; or FIGS. 10 to 12; or FIGS. 13 to 16; of the accompanying drawings.

12. A rotary drilling string incorporating a top sub and a saver sub which 10 are non-rotatably and releasably coupled by a saver sub clamp, substantially as hereinbefore described, with reference to FIGS. 1 to 7; or FIGS. 8 and 9; or FIGS. 10 to 12; or FIGS 13 to 16; of the accompanying drawings.

13. A method of coupling a top sub to a saver sub for a rotary drilling string employing the saver sub clamp as claimed in any one of Claims 1 to 9, 15 or Claim 11. 20