US3255612A

US3255612A - Telescoping drilling device

Info

Publication number: US3255612A
Application number: US344583A
Authority: US
Inventors: James R Mayer; Joe D Tipton
Original assignee: Gardner Denver Inc
Current assignee: Gardner Denver Inc
Priority date: 1964-02-13
Filing date: 1964-02-13
Publication date: 1966-06-14
Anticipated expiration: 1983-06-14

Description

June 14, 1966 J. R. MAYER ETAL TELESCOPING DRILLING DEVICE 2 Sheets-Sheet 1 Filed Feb. 13, 1964 JAMES R. MAYER J05 D. T/Pm/v INVENTORS BY M};

ATTORNEY June 1966 J. R. MAYER ETAL 3,

I'ELESCOPING DRILLING DEVICE Filed Feb. 13, 1964 2 Sheets-Sheet 2 United States Patent 3,255,612 TELESCOPING DRILLING DEVICE James R. Mayer, Dallas, and Joe D. Tipton, Garland,

Tex., assignors to Gardner-Denver Company, a corporation of Delaware Filed Feb. 13, 1964, Ser. No. 344,583 17 Claims. (Cl. 64-235) This invention relates to a drilling device for drilling holes in the earth; and, more particularly, to an extensible drill pipe assembly for use with a self-propelled drilling rig in the drilling of shallow holes.

In many earth drilling operations, such as in quarrying and in geophysical exploration, it is required to drill a number of shallow holes for receiving a blasting charge. Drilling rigs commonly used for such operations may be truck mounted or otherwise self-propelled and are provided with a mast which is raised to a generally vertical position during the drilling operation and which is folded down to a generally horizontal position when the rig is moved from place to place. With rigs of this type, the height of the mast is necessarily limited, in the interest of the portability of the rig; and the depth to which a hole which may be drilled without adding lengths of drill pipe is correspondingly limited.

In some rigs of this type, means are provided for storing one or more extra lengths of drill pipe for use in drilling deeper holes. This necessitates extra equipment on the rig for storing the extra lengths of pipe, for moving the pipe between the stored position and the drilling position, and for making and breaking the pipe connections. As is well known, the necessary operations for adding and/or removing lengths of pipe of a drill string are time consuming.

An object of this invention is to provide a selfcontained, extensible drill pipe assembly which may be normally stored in drilling position within a mast, when it is collapsed to a minimum length, and which may be extended, during the drilling operation, to a maximum length which is greater than the height of the mast. Another object of the invention is to provide an extensible kelly assembly for a drilling rig, of the type described,

having a rotary table drive.

The novel features of the invention, as well as additional objects and advantages thereof, will be understood more fully from the following description when read in connection with the accompanying drawings in which:

FIG. 1 is a longitudinal sectional view of a telescoping kelly assembly according to the present invention, including drive bushings for each portion of the kelly assembly,

and showing the relation of the parts at the beginning of a drilling cycle;

FIG. 2 is a transverse sectional view taken along the line 22 of FIG. 1 looking in the direction of the appended arrows;

FIG. 3 is a transverse sectional view taken along the line 33 of FIG. 1;

FIG. 4 is a partial longitudinal sectional View showing the relation of the parts of the assembly of FIG. 1 at a later point in a drilling cycle;

FIG. 5 is a partial longitudinal sectional view showing the relation of parts of the assembly of FIG. 1 at a still later point in the drilling cycle;

FIG. 6 is a transverse sectional view taken along the line 6-6 of FIG. 5;

FIG. 7 is a transverse sectional view taken along the line 77 of FIG. 5;

3,255,612 Patented June 14, 1966 "Fee FIG. 8 is a partial longitudinal sectional view showing the relation of parts of the assembly of FIG. 1 at a still later point in the drilling cycle.

In the drawings, a preferred form of drill pipe assembly according to the present invention is shown as a telescoping kelly assembly for driving a rotary bit which is directly attached to the lower end of the assembly. As best shown in FIG. 1, the principal elements of this assembly comprise an outer drill pipe in the form of a square kelly 11, an inner drill pipe in the form of a fluted kelly 12 telescopically received within the square kelly, a square drive bushing 13 mounted on the square kelly 11 and adapted to be driven by a rotary table, and a fluted drive bushing 14 mounted on the fluted kelly 12 and adapted to be coupled to the square drive bushing 13 in driving relation during a portion of the drilling cycle. A rotary drill bit 15 is secured to the lower end of the square kelly 11; and a swivel coupling 16 is mounted on the upper end of the fluted kelly 12 for the purpose of coupling a rotary swivel thereto.

The exterior surface of the outer or square skelly 11 is square in cross section throughout its length, as best shown in FIGS. 2 and 3, for accommodation by the square opening of the square drive bushing 13. The kelly is provided with a cylindrical bore 19 which extends from the upper end to a point adjacent the lower end. At the lower end, the bore is reduced to define a thickened wall portion 20 into which are formed an internal thread 2i]. opening from the lower end of the kelly for the purpose of securing the drill bit 15 thereto, and an internal thread 22 for the purpose of coupling the fluted kelly 12in the telescoped relation, as will be described. If it is assumed that the telescoping kelly assembly is rotated clockwise,

as viewed from the top of the assembly, the bit thread 21 will be a right-hand thread and the thread 22 will be a left-hand thread, for reasons which will become apparent. The hand of other threads, whichwill be referred to, will be in relation to this same assumed direction of rotation.

An internal right-hand thread 23 is provided at the upper end of the square kelly 11 merging with the bore 19, for the purpose of coupling the fluted kelly in extended relation, as will be described.

Adjacent to the upper end of the square kelly, there is provided a peripheral groove 24, as best shown in FIGS. 1, 2 and 7, the base of the groove being cylindrical and having a diameter equivalent to the smallest dimension of the square section. This groove 24 is provided for accommodating a C-shaped retainer plate 25, best shown in FIG. 7, for the purpose of supporting the square kelly 11 when it is uncoupled from the fluted kelly 12. The retainer plate 25 has a circular periphery and is provided with a slot 26 having a width corresponding to the diameter of the groove 24, the base of the slot 26 defining a semicircle having the same diameter and being concentric with the circular periphery of the retainer, As best shown in FIGS. 5 and 7, the retainer 25 is inserted in the groove 24, defining a stop member lying in a plane transverse to the longitudinal axis of the square kelly. In this assembled relation, the circular periphery of the retainer defines a portion of a circle concentric with the longitudinalnal axis of the kelly. When the retainer rests on the top of the square drive bushing 13 for the purpose of supporting the square kelly 11, the retainer 25 is prevented from being dislodged from its concentric supporting position since it is confined by the ring handle of the square The inner or fluted kelly 12 comprises a generally tubular member having a through bore, and having a cylindrical exterior surface which is dimensioned for a relatively close fit within the bore 19 of the square kelly. The upper end of the fluted kelly is provided with an internal left-hand thread 28 merging with the bore, for receiving the external left hand thread of the swivel coupling 16; and the swivel coupling 16 has an internal lefthand thread 17 for engagement with the external left-hand thread of a rotary swivel. At the lower end of the fluted kelly there is a reduced diameter portion provided with an external left-hand thread 29 for engagement with the internal thread 22 of the square kelly. When the

threads

22 and 29 are engaged, as shown in FIG. 1, the square kelly and fluted kelly are longitudinally and rotationally coupled together in telescoped relation.

The fluted kelly 12 is provided with four longitudinal grooves or flutes 30 of semicircular cross section equally spaced about the periphery thereof, as best shown in FIG. 2, the flutes extending from the upper end of the kelly to a point adjacent to the lower end. The flutes 30 are provided to accommodate drive pins of the fluted drive bushing 14, as will be described subsequently.

Adjacent to the lower end of the fluted kelly 12, below the ends of the flutes 30, there is provided a neck 31 formed by a peripheral notch or groove defining a square section of the kelly between axially facing transverse shoulders. The neck 31 is provided for accommodating a kelly connector 32, best shown in FIGS. 5, 6 and 8, which consists of a bushinglike assembly split in a longitudinal plane to define two complementary halves. The connector assembly 32 has a length corresponding to the length of the neck 31 and defines a square bore dimensioned to closely accommodate the square section of the neck 31, so that the connector may be assembled on the fluted kelly in nonrotating and longitudinally fixed relation. The lower end of the connector assembly 32 is provided with an external right-hand thread 33 for mating engagement with the upper thread 23 of the square kelly 11. In FIG. 5, the connector 32 is shown assembled on the fluted kelly and in position to be engaged with the thread 23 of the square kelly. In FIG, 8 the connector thread 33 is shown engaged with the thread 23 of the square kelly; and in this manner the fluted kelly and the square kelly are longitudinally and rotationally coupled together in extended relation. As best seen in FIGS. 6 and 8, the maximum external diameter of the connector 32 is no greater than the smallest dimension of the square kelly section.

When the kellys 11 and 12 are coupled together in telescoped relation as shown in FIG. 1, the rotary drive is through the square drive bushing 13 having a square opening dimensioned for a driving fit with the square kelly. The drive bushing 13 is conventional in most respects, comprising a body having a lower cylindrical portion 36, an adjoining conical portion 37, radial lugs 38 for driving engagement with a conventional rotary table, and a ring handle 39 attached by supporting arms 40. The bushing 13 differs from conventional drive bushings in that it includes an upwardly extending cylindrical flange 41 having an internal gear tooth spline 42 for coupling the fluted drive bushing 14 to the square drive bushing as will be described.

The fluted drive bushing 14 consists of a generally cylindrical body having a cylindrical bore which is slightly larger in diameter than the outer diameter of the fluted kelly 12. The internal bore of the bushing is provided with four longitudinal grooves or flutes 45 of semicircular cross section which are equally spaced within the bore. When the fluted drive bushing is assembled on the kelly 12, the bushing flutes 45 will be in radial registry with the kelly flutes 30 so that cylindrical drive pins 46 may be accommodated within the mating flutes to provide a rotational coupling betwen the drive bushing 14 and the kelly 12. The drive pins 46 are longitudinally retained,

relative to the fluted drive bushing, by means of upper and lower retainer rings 47 and 48, respectively. The retainer ring 47 may be secured to the bushing body by means of bolts, for example; and the retainer ring 48- may be retained by means of a suitable snap ring, for example. Aconventional ring handle 50 is provided at the upper end of the bushing.

The lower end of the bushing 14 is reduced in diameter and is provided with an external gear tooth spline 49, complementary to the internal gear tooth spline 42 of the square drive bushing. The gear tooth splines 42 and 49 are fine tooth splines, to facilitate the coupling of the drive bushings. As will be seen from the discussion of the operation which follows, the splines should be selfengaging when the fluted drive bushing moves downwardly into engagement with the square drive bushing, considering that the principal force for engaging the splines is the weight of the fluted drive bushing. At the time of such engagement the two drive bushings are rotationally coupled through their respective kellys; and, since the two kellys are not coupled in any predetermined angular registration, there is no particular angular registration of the .drive bushings. There will, of course, be some relative rotation between the two drive bushings, which is permitted by the play or backlash in the drive couplings between the two bushings and their respective kellys, This limited relative rotation between the drive bushings will assure that the

splines

42 and 49 will be self-engaging if the pitch of the splines is made sufliciently fine in relation to the amount of such backlash.

When the kellys 11 and 12 are assembled in telescoped relation, as shown in FIG. 1, the fluted drive bushing 14 merely rests on the upper end of the square kelly 11. When the kellys 11 and 12 are coupled in extended relation, as shown in FIG. 8, the assembly is driven through the fluted drive bushing 14 which is coupled to the square drive bushing 13 through engagement of the

respective splines

49 and 42.

The operation of the device will now be described for the drilling of a single hole. At the beginning of a drilling. operation, the assembly will be in telescoped relation, as shown in FIG. 1, wherein the kellys 11 and 12 are coupled together through engagement of the

respective threads

22 and 29. The square drive bushing 13 would be seated in drive relation in a conventional rotary tables; and the kellys would be supported through a rotary swivel to which the swivel coupling 16 is attached, the fluted drive bushing 14 resting on the upper end of the square kelly as shown.

It is assumed, as indicated previously, that the rotary drive by the rotary table is clockwise as viewed from the top of the drilling assembly; and, accordingly, the bit thread 21 is a right-hand thread to assure that the bit 15 will remain coupled to the lower end of the square kelly during the drilling operation. During the first portion of the drilling cycle, the square kelly 11'is driven by the square drive bushing; and the fluted kelly, the swivel coupling, and the rotating portion of the rotary swivel will drag due to friction and will have a tendency to rotate counterclockwise to the square kelly. Accordingly, the

threads

17, 28, 29 and their mating threads are left-hand threads to prevent a breakout of those threaded connections during the normal drilling operation; that is, these threaded connections are self-tightening or self-maintaining.

The first portion of the drilling cycle will continue until the upper end of the square kelly have moved downwardly into the square bore of the square drive bushing, but remains in driving engagement with the square drive bushing, as shown in FIG. 4. The fluted drive bushing 14 has also moved downwardly, permitting full engagement of the

splines

42 and 49 of the two drive bushings. The first portion of the drilling cycle is then concluded; and the kellys 11 and 12 must be coupled in extended The threaded connection between the kellys 11 and 12 must first be broken; and this is accomplished by first raising the assembly of the kellys 11 and 12 and the drive bushing 14 to a position where the annular groove 24,

at the upper end of the square kelly, lies just above the ring handle 39 of the square drive bushing. The C- shaped retainer 25 may now be inserted in the groove 24, and the assembly then lowered to a position where the retainer 25 rests on the upper surface of the flange 41 of the square drive bushing. This position of the square kelly and retainer 25 is shown in FIGS. and 7; and it is seen that the retainer is confined by the ring handle 39 and its supporting arms so that the retainer 25 may not become dislodged from locking engagement with the groove 24 of the square kelly. The square kelly is now supported by the rotary table independently of the remainder of the assembly.

In order to break out the threaded coupling between the kellys 11 and 12, represented by the

threads

22 and 29, the fluted kelly may be prevented from rotating by placing a breakout wrench on the fluted drive bushing 14 (which may be provided with suitable wrench engaging surfaces) and the rotary table rotated in a counterclockwise direction to thereby rotate the square kelly counterclockwise relative to the fluted kelly. After this coupling has been broken, the assembly of the fluted kelly and fluted drive bushing may then be raised to the position shown in FIG. 5 wherein the neck 31 lies above the upper end of the square kelly 11. During this raising of the fluted kelly, the fluted drive bushing will remain in its position engaging the upper end of the square kelly until the drive pins 46 are engaged by the lower ends of the flutes 30; The fluted drive bushing is then at its lowermost position relative to the fluted kelly, and the bushing will then be raised with the kelly as indicated in FIGS.

The neck 31 of the fluted kelly is now exposed so that the kelly connector 32 may be assembled on the neck; and the two halves of the connector 32 will be retained in position, as shown in FIG. 5, merely by friction due to the close fit which is provided for these parts.

The assembly of the fluted kelly, fluted drive bushing,

and connector 32 is now'lowered to engage the connector thread 33 with the thread 23 at the upper end of the square drive bushing. These threads are right-hand threads; and'the connection is now made by again pre venting rotation of the fluted kelly by means of a breakout wrench attached to the fluted drive bushing, for example, and driving the rotary table and square kelly in a counterclockwise direction. The kellys 11 and 12 are now longitudinally and rotationally coupled in extended relation for continued drilling. The assembly of the two kellys and the fluted drive bushing is now raised sufliciently to permit removal of the retainer 25 from the square kelly; and the assembly is then lowered to the position where the bit 15 is again bottomed. In this position, the spline 49 of the fluted drive bushing is, at least, partially engaged with the spline 42 of the square drive bushing. When drilling is resumed the kellys 11 and 12 will first be rotated through both drive bushings, while the square kelly '11 is in driving engagement with the square drive bushing 13; and then the drive will be through the coupled drive bushings acting on the fluted kelly alone, after the square kelly 11 has passed through the square drive bushing as shown in FIG. 8. The drilling may then continue to a depth permitting by the length of the coupled kellys 11 and 12. During this portion of the drilling operation, the square kelly will tend to rotate counterclockwise relative to the fluted kelly; therefore, the right-hand threaded connection, defined by the

threads

23 and 33, is self-tightening or self-maintaining.

To again assemble the kellys in the telescoped relation, and remove the assembly from the hole, a procedure somewhat the reverse of that described must be followed,

namely: raise the assembly to support the square kelly by means of the retainer 25; break the threaded

connection

23, 33, and remove the connector 32; lower the fluted kelly 12 to a position to make the threaded

coupling

22, 29; and raise the entire assembly out of the hole, removing the retainer 25.

What has been described is a self-contained, telescoped kelly assembly, particularly adapted for use with selfpropelled drilling rigs, which may be used in a collapsed or telescoped condition in the same manner as a conventional kelly to drill a shallow hole limited to the length of the kelly which can be accommodated in a drilling'rig. This kelly may be extended to increase the effective length thereof, and renders a drilling rig much more versatile in its ability to drill deeper holes without the necessity for pipe storage means and pipe handling means for extra lengths of drill pipe.

What is claimed is:

1. In a drilling device:

a first drill pipe having means at its lower end for attaching a drill bit thereto;

a second drill pipe, dimensioned to be telescopically received within said first drill pipe;

complementary coupling means disposed adjacent to the lower ends'of said first and second drill pipes, respectively, for coupling said pipesin telescoped relation to define a relatively short drill pipe assemy;

and complementary coupling means disposed adjacent to the upper end of said first drill pipe and adjacent to the lower end of said second drill pipe, respectively, for coupling said pipes in extended relation to define a relatively long drill pipe assembly.

2. The invention set forth in claim 1 wherein said first named coupling means is self-maintaining for one direction of relative rotation of said drill pipes;

and wherein said second named coupling means is self- =maintaining for the opposite direction of relative rotation of said drill pipes.

3. In a drilling device:

a first drill pipe having means at its lower end for attaching a drill bit thereto; a second drill pipe, dimensioned to be telescopically received within said first drill p p said first drill pipe having a lower internal thread and said second drill pipe having a lower external thread; said threads being mutually engageable, when said pipes are in telescoped relation, to longitudinally and rotationally couple said pipes;

said first drill pipe having an upper internal thread; an externally threaded member mountable on said second drill pipe, adjacent to its lower end, in long-itudinally fixed and nonrotatable relation thereto; and the thread of said member being mutually engageable with the upper internal thread of said first pipe, when said pipes are in extended relation, to longitudinally androtationally couple said pipes.

4. The invention set forth in claim 3 wherein saic threads for coupling said pipes in telescoped relation define a first threaded connection and are of one hand, whereby said first connection is self-maintaining for one direction of relative rotation of said drill pipes;

and wherein said threads for coupling said pipes in extended relation define a second threaded connection and are of the opposite hand, whereby said second connection is self-maintaining for the opposite direction of relative rotation of said drill pipes.

5. In a drilling device:

a first drill pipe having means at its lower end for attaching a drill bit thereto; means defining an internal thread within said first drill pipe adjacent to its lower end; means defining an internal thread within said first drill pipe adjacent to its upper end;

a second drill pipe dimensioned to be telescopically received within said first drill pipe;

means defining an external thread at the lower end of said second drill pipe for threaded engagement with said internal thread at the lower end of said first drill pipe to longitudinally and rotationally couple said first and second pipes in telescoped relation, to define a relatively short drill pipe assembly;

said second drill pipe having a neck adjacent to the lower end thereof, defined by a portion of noncircular cross section between axially facing shoulders; an externally threaded connector defined by two half sections of a sleevelike member formed to be nonrotatably mounted and longitudinally fixed on said second drill pipe at said neck; and said connector being engageable with said internal thread at the upper end of said first drill pipe to longitudinally and rotationally couple said first and second drill pipes in extended relation, to define a relatively long drill pipe assembly.

- 6. In a rotary drilling device:

a first drill pipe having a noncylindrical exterior surface defining a kelly; a second drill pipe, dimensioned to be telescopically received within said first drill pipe, having a noncylindrical exterior surface defining a kelly;

a first drive bushing mounted on said first kelly in driving relation thereto, adapted to be driven by a rotary table; a second drive bushing mounted on said second kelly in driving relation thereto; coupling means on said first and second drive bushings for rotationally coupling same when moved axially into engagement with each other;

means for longitudinally and rotationally coupling said kellys together in telescoped relation, to define a relatively short drill pipe assembly; said telescoped kelly assembly adapted to be driven by said first drive bushing acting on said first kelly;

and means for longitudinally and rotationally coupling said kellys together in extended relation, to define a relatively long drill pipe assembly; said extended kelly assembly adapted to be driven by said first and second drive bushings coupled together and acting on said second kelly.

7. The invention set forth in claim 6 wherein said coupling means for coupling said kellys in telescoped relation is self-maintaining for one direction of relative rotation of said kellys;

and wherein said coupling means for coupling said kellys in extended relation is self-maintaining for the opposite direction of relative rotation of said kellys.

8. The invention set forth in claim 6 wherein said coupling means for coupling said kellys in telescoped and extended relation are defined, respectively, by first and second threaded connections.

9. The invention set forth in claim 8 wherein the threads of said first connection are of one hand, whereby said first connection is self-maintaining for one direction of relative rotation of said kellys;

and wherein the threads of said second connection are of the opposite hand, whereby said second connection is self-maintaining for the opposite direction of relative rotation of said kellys.

10. The invention set forth in claim 6 including:

means at the lower end of said first kelly for attaching a drill bit thereto;

and means at the upper end of said second kelly for attaching same to a rotary swivel device to provide support means for said second kelly and for said assembled kellys.

11. The invention set forth in claim 10 including removable, external shoulder means for attachment to said first kelly; said first kelly having means adjacent to the upper end thereof for receiving said removable shoulder means;

and said removable shoulder means being adaptable to engage said first drive bushing to support said first kelly during the coupling and uncoupling of said kellys.

12. The invention set.forth in claim 10 including:

means on said first kelly defining a peripheral groove;

and a retainer plate having slot means for engagement with said peripheral groove, to define a longitudinally fixed shoulder on said first kelly; said plate being engageable with an upper surface of said first drive bushing to longitudinally support said first kelly.

13. The invention set forth in claim 12 wherein said first drive bushing includes a ring handle mounted concentrically of said bushing; and wherein said retainer plate is provided with a circular periphery dimensioned to be received and confined within said bushing handle.

14. The invention set forth in claim 6 wherein said coupling means for said drive bushings is defined by complementary gear tooth splines provided on said first and second drive bushings, respectively.

15. The invention set forth in claim 14 wherein said gear tooth splines are fine pitch splines, to provide for self-coupling of said bushings when moved axially into engagement with each other.

16. In a rotary drilling device:

a first drive bushing mounted on said first kelly in driving relation thereto, adapted to be driven by a rotary table; a second drive bushing mounted on said second kelly in driving relation thereto; first complementary coupling means on said first and second drive bushings for rotationally coupling same when moved axially into engagement with each other;

second complementary coupling means disposed adjacent to the lower ends of said first and second kellys, respectively, for coupling said kellys in telescoped relation to define a relatively short kelly assembly adapted to be driven by said first drive bushing;

and third complementary coupling :means disposed adjacent to the upper end of said first kelly and adjacent to the lower end of said second kelly, respectively for coupling said kellys in extended relation to define a relatively long kelly assembly adapted to be driven by said first and second drive bushings coupled together.

17. In a rotary drilling device:

a first drill pipe having a noncylindrical exterior surface defining a kelly; a second drill pipe, dimensioned to be telescopically received within said first drill pipe, having a noncylindrical exterior surface defining a kelly,

a first bushing mounted on said first kelly in driving relation thereto, adapted to be driven by a rotary table; a second drive bushing mounted on said second kelly in driving relation thereto; coupling means on said first and second drive bushings for rotationally coupling same when moved axially into engagement with each other;

said first kelly having a lower internal thread and said second kelly having a lower external thread; said threads being mutually engageable and defining a first threaded connection to longitudinally and rotationally couple said kellys in telescoped relation; said telescoped kelly assembly adapted to the driven by said first drive bushing;

9 10 said first kelly having an upper internal thread; an ex- References Cited by the Examiner ternilly thrieaded member mountedd on said sec- UNITED STATES PATENTS 0nd elly, a jacent to its lower end an longitudina ly fixed in nonrotatable relation thereto; and the thread 1897434 2/1933 Lq et 64 23-5 of said member being mutually engageable with the 5 'Q 1/1937 Miner 64 23 upper internal thread of said first kelly and defining 2222207 11/1940 Tels et 3,038,547 6/1962 Deely 6423.5

a second threaded connection to longitudinally and rotationally couple said kellys in extended relation; MILTON KAUFMAN Primary Examiner said extended kelly assembly adapted to be driven by said first and second drive bushing coupled to- 0 BROUGHTON DURHAM Examiner gether. H. C. COE, Assistant Examiner.

Claims

6. IN A ROTARY DRILLING DEVICE: A FIRST DRILL PIPE HAVING A NONCYLINDRICAL EXTERIOR SURFACE DEFINING A KELLY; A SECOND DRILL PIPE, DIMENSIONED TO BE TELESCOPICALLY RECEIVED WITHIN SAID FIRST DRILL PIPE, HAVING A NONCYLINDRICAL EXTERIOR SURFACE DEFINING A KELLY; A FIRST DRIVE BUSHING MOUNTED ON SAID FIRST KELLY IN DRIVING RELATION THERETO, ADAPTED TO BE DRIVEN BY A ROTARY TABLE; A SECOND DRIVE BUSHING MOUNTED ON SAID SECOND KELLY IN DRIVING RELATION THERETO; COUPLING MEANS ON SAID FIRST AND SECOND DRIVE BUSHINGS FOR ROTATIONALLY COUPLING SAME WHEN MOVED AXIALLY INTO ENGAGEMENT WITH EACH OTHER; MEANS FOR LONGITUDINALLY AND ROTATIONALLY COUPLING SAID KELLYS TOGETHER IN TELESCOPED RELATION, TO DEFINE A RELATIVELY SHORT DRILL PIPE ASSEMBLY; SAID TELESCOPED KELLY ASSEMBLY ADAPTED TO BE DRIVEN BY SAID FIRST DRIVE BUSHING ACTING ON SAID FIRST KELLY; AND MEANS FOR LONGITUDINALLY AND ROTATIONALLY COUPLING SAID KELLYS TOGETHER IN EXTENDED RELATION, TO DEFINE A RELATIVELY LONG DRILL PIPE ASSEMBLY; SAID EXTENDED KELLY ASSEMBLY ADAPTED TO BE DRIVEN BY SAID FIRST AND SECOND DRIVE BUSHING COUPLED TOGETHER AND ACTING ON SAID SECOND KELLY.