US3297100A - Dual drill stem method and apparatus - Google Patents

Description

Jan. 10, 19 7 s. H. CREWS 3,297,100

DUAL DRILL STEM METHOD AND APPARATUS Filed April 15, 1964 4 Sheets-Sheet l INVENTOR. SIM H. CREWS A T TOQA/EYS Jan. 10, 1967 S. H. CREWS DUAL DRILL STEM METHOD AND APPARATUS 4 Sheets-Sheet 2 Filed April 13, 1964 Jan. 10, 1967 s. H. cREws 3,297,100

DUAL DRILL STEM METHOD AND APPARATUS Filed April 13, 1964 4 Sheets-5heet 15 M H CREWS S. H. CREWS DUAL DRILL STEM METHOD AND APPARATUS Jan. 10, 1967 4 Sheets-Sheet 4.

Filed April 13, 1964 WW VM 7 INVENTOR. $1M H CREW S United States Patent 3,297,100 DUAL DRILL STEM METHOD AND, APPARATU Sim H. Crews, Mercury, Nev., assignor to Large Mine Shaft Drillers, incorporated, Amarillo, Tern, a corporation of Texas Filed Apr. 13, 1964, Ser. No. 359,214 2 Claims. Cl. 175-195) This invention relates to improved methods and apparatus for drilling holes downwardly into the earth, and especially to the rotary drilling of relatively large diameter mine shafts and the like.

It is a well developed practice in forming both small and large diameter wells to drill into the earth with a rotating bit secured at the lower end of a string of rods or drill pipe while earth cuttings produced by the bit are flushed to the surface and removed from the well bore by liquids, gases or combinations thereof under controlled pressures. In the past several years, however, additional development work has led to improved drilling rates and lower costs for drilling relatively small diameter wells such as those used in the production of water, gas and oil. This development work has centered upon increasing the weight or pressure applied to cutting bits and utilizing increased pneumatic or hydraulic flow rates and volumes in the well bore for keeping the hole face clean and lifting larger bit cuttings to the surface.

The application of such increased bit pressure in relatively large diameter shaft boring has been accomplished reasonably well, However, the application of sufficient hydraulic and/or pneumatic flow rates and volumes in large diameter bores for continually cleaning the hole face and carrying bit cuttings to the surface has heretofore not been accomplished. This has been somewhat due to the prohibitively high fluid volumes involved, but in greater measure to the excessively high power requirements and quantity of pumping equipment necessary to produce high enough return flow velocities in the drill stem-well bore annulus to lift reasonably large bit cuttings while providing high pressure bottom jets to clean the hole face.

The principal objects of the present invention are: to provide a method and apparatus for drilling larger diameter holes which utilizes a dual drill stem forming two conduits in addition to the drill stem-well bore annulus; to provide such a method and apparatus wherein one of the conduits may be used to conduct a fluid to the bit with sufiicient pressure to cleanse the hole face with high pressure bottom jets and the second conduit may be used to conduct a high volume-relatively low pressure fluid into the drilling area to improve the drill stemwell bore annulus fluid return velocities; to provide such a method and apparatus wherein the second conduit may alternatively be used to conduct the fluid back to the earth surface with the required velocity for lifting relatively large bit cuttings; to provide such a method and apparatus which permits the application of greater weight for producing a higher penetration rate with a consequent reduction in drilling costs; to provide such a method and apparatus which permits the rapid and convenient application and removal of a dual fluid passage bit, a dual fluid passage drill collar string, a dual fluid passage drill pipe string, and a dual fluid passage kelly for producing relatively large diameter earth holes such as mine shafts; to provide in the practice of rotary drilling dual drill string apparatus so constructed that concentric inner 3,297,160 Patented Jan. 10, 1967 and outer pipes may be respectively easily joined and removed for insertion into and removal from the well bore; to provide such a dual drill string apparatus wherein joints of inner pipes project above respective lower joining collars of the respective outer pipe open joint so that the inner pipes may be held securely while being joined or uncoupled from succeeding inner pipes; to provide such apparatus wherein the respective dual string inner pipes are of approximately the same length as the outer pipes and are concentrically spaced therewithin by means of wings or spacers extending into the passageway between the outer and inner pipes; to provide such apparatus wherein the inner pipes are free to move longitudinally within the outer pipes so as to permit easy exposure of the inner pipe joints as Well as complete removal of the inner pipes from the outer pipes when desired; to provide unique accessory tools to facilitate the handling and joining of the relatively movable inner and outer pipes of a dual drill string section; and to provide such a method and apparatus which is relatively simple in construction, versatile in operation and yet highly effective in use.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of this invention.

FIG. 1 is a partially schematic sectional view in side elevation showing well drilling apparatus incorporating a preferred embodiment of this invention.

FIG. 2 is a vertical cross-sectional view on a larger scale showing a dual pipe string section engaged with a male pipe thread protector at the lower end thereof.

FIG. 3 is a vertical cross-sectional view on a scale similar to FIG. 2 showing a dual pipe string section engaged with an inner tube suspending plug at the upper end thereof.

FIG. 4 is a cross-sectional view through a dual pipe section taken on the line 4-4, FIG. 2, showing particularly wings or spacers for centering the inner pipe,

FIG. 5 is a fragmentary vertical cross-sectional view through a dual pipe section joint on a scale similar to FIG. 2 illustrating an outer pipe joint as uncoupled and exposing the adjacent inner pipe joint.

FIG. 6 is a vertical cross-sectional fragmentary view on a scale similar to FIG. 2 particularly illustrating a drill bit adapted for use in accordance with this invention. I FIG. 7 is a fragmentary vertical cross-sectional view on a scale larger than that of FIG. 2 illustrating a telescoping inner tube joint contained within the drill string drive stem or kelly.

FIG. 8 is a vertical fragmentary view showing a modified form of swivel head assembly in the drilling position.

FIG. 9 is a vertical fragmentary view showing the modified swivel head of FIG. 8 in connecting or inner pipe joint exposed position.

FIG. 10 is a vertical cross-sectional partially schematic view illustrating another form of drill bit adopted for use in accordance with this invention.

Referring to the drawings in more detail:

The reference numeral 1, in FIG. 1, generally indicates a drilling apparatus particularly adapted for boring relatively large holes or shafts, for example in the order of lO-feet in diameter. The drilling apparatus 1 is illustrated in conjunction with a shaft or bore 2, a portion of which is protected by a well casing 3 having a well head 4 thereon. The drilling apparatus 1 includes a vertical elongated dual drive stem or kelly 5 which extends downwardly through the well head 4 and makes a vertically sliding seal therewith in a well known manner. A rotary drive table 6 is located above the well head 4 and the kelly 5 extends therethrough. The kelly 5 terminates at the upper end 7 thereof in a swivel head 8 having a bail 9 by which the kelly is vertically supported.

The kelly 5 comprises an outer generally square pipe 10 which engages with the rotary drive table 6 and well head 4 and an inner circular pipe 11 of smaller diameter than the inside dimensions of the kelly outer pipe 10 and extending longitudinally within the outer pipe 10. The pipes 10 and 11 form inner and outer concentric flow passageways 12 and 13 respectively within the kelly 5. The swivel head 8 includes an inner gooseneck 14 communicating with the kelly inner passageway 12 and an outer gooseneck 15 surrounding a portion of the inner gooseneck 14 and communicating with the kelly outer passageway 13 in a known manner, the swivel head remaining rotationally stationary when the kelly is rotated by the drive table 6.

The kelly outer pipe 10, in the illustrated example, terminates at the lower end 16 thereof in a threaded drill pipe string pin collar 17 having tapered screw threads 18 of the rapid pitch type. The kelly inner pipe 11 terminates at the lower end 19 thereof in a threaded conduit pipe string pin collar 20 having tapered screw threads 21 of the rapid pitch type. The kelly inner pipe 11 includes a telescoping sealed joint 22 spaced between the swivel head 8 and the pin collar 20, FIG. 7. The joint 22 is comprised of an intermediate coupling portion 23 threadedly engaged at the lower end thereof in a packing collar 24 containing suitable chevron packing 25 and at the upper end thereof in a connector section 26. The coupling portion 23 slightly reduces in diameter intermediate the ends thereof forming an interior upwardly facing shoulder 27 adapted to engage an arresting flange 28 on an inner telescoping tube 29 slightly engaging the packing 25 and which supports the pin collar 20. Thus, the pin collar 20 is permitted to be axially positioned between a first or exposed position illustrated by the broken lines at 30 spaced below the kelly outer pipe pin collar 17 and a second or withdrawn position as illustrated in solid lines at 31 spaced above the kelly outer pipe pin collar 17.

The drilling apparatus 1 includes a vertically extending dual pipe string 32 comprising a plurality of connected outer or drill string pipes 33 and a plurality of connected inner or conduit string pipes 34 of smaller outside diameter than the inside diameter of the drill string pipes 33 and contained therewithin. The drill string pipes 33 each terminate at the upper end 35 thereof in a threaded drill string box collar 36 having tapered rapid pitch threads 37 thereon and at the lower end '39 thereof in a threaded drill string pin collar 40 having tapered rapid pitch threads 41 thereon adapted to threadedly engage with the box collar 36 of an adjacent drill string pipe 33. The drill string pipes 33 are joined in a string 42 by mating succeeding drill string box and pin collars. The uppermost drill string box collar is joined to the kelly drill string pin collar 16 for suspending the drill pipe string 42 from the swivel head 8.

The conduit string pipes 34 each terminate at the upper end 43 thereof in a conduit string box collar 44 having tapered rapid pitch threads 45 therein and at the lower end 46 thereof in a conduit string pin collar 47 having external tapered rapid pitch threads 48 thereon. The conduit string pipes 34 are respectively joined in a string 49 within the drill pipe string 42 by mating succeeding conduit pipe box and pin collars. The uppermost conduit pipe box collar is mated to the pin collar 20 of the kelly 5 and, as noted further hereinafter, causes the kelly inner pipe joint 22 to telescope upon the breaking or mating of the joint 50 formed at the kelly outer pipe lower end 16. The drill pipe string 42 and concentric conduit pipe string 49 form inner and outer concentric flow passageways 51 and 52 respectively communicating with the kelly flow passageways 12 and 13.

The conduit string pipes 34 each have, in the illustrated example, three radially outwardly extending guides or wings 53 fixed thereto adjacent the box collars 44 thereof and extending into the outer flow passageway 52. The guides or wings 53, however, present a relatively thin profile in cross-section and, therefore, do not significantly block flow through said passageway. The guides or wings 53 terminate at outer ends 54 at respective outer radial dimensions or positions which produce the centering of the respective conduit pipe 34 within the respective drill string pipe 33 but permit a relative longitudinal sliding movement therebetwcen.

A dual fluid passage drill bit 55 is located at the bottom of or axially beneath the dual pipe string 32. The bit 55 comprises a housing 56 having a frusto-conical side wall 57 of greater diameter at the bottom 58 thereof than at the top 59. The housing 56 includes spaced-apart upper and lower walls 61} and 61 secured thereto adjacent the respective top 59 and bottom 58 and forming with the side wall 57 an enclosed frusto-conical chamber 62. The housing upper wall 60 extends radially horizontally outwardly from the top of the housing forming a coupling flange 63 for a purpose noted hereinafter. The housing lower wall '61 has a plurality of downwardly extending legs 64 secured thereto and respectively rotatably supporting at the lower ends thereof frusto-conical rotatable cutters 65 of known design. A plurality of tubes 66 are mounted in and extend through the housing lower wall 61 and form passageways 67 communicating between the chamber '62 and the exterior of the housing 56. The tubes 66 are respectively positioned for directing fluid flow in jets from the chamber 62 downwardly adjacent the respective cutters 6-5 for maintaining the cutting field clear of cuttings or debris, as discussed more fully hereinafter.

An outer vertically extending length of pipe 68 is secured at the lower end 69 thereof in dawnwardly abutting relation to the housing lower wall 61 and extends coaxially upwardly within the chamber 62. The length of pipe 68 extends into the housing upper wall 60 and terminates at the upper end 70 thereof at the elevation of the upper surface 71 of the coupling flange 63. A plurality of radially outwardly and downwardly extending bores 72 extend through the length of pipe 68 intermediate the ends thereof providing flow passageways communicating between the chamber 62 and the interior 73 of the length of pipe 68. An inner length of pipe 74 of smaller outside diameter than the inside diameter of the length of pipe 68 extends coaxially therewithin and also extends downwardly through and is fixed to the housing lower wall 61 forming an open mouth 75 at the lower surface 76 of the housing lower wall 61. The inner length of pipe 74 terminates at the upper end 77 thereof in a conduit string box collar 78 spaced above the coupling flange upper surface 71 and threadedly receiving the lowermost condit string pin collar 79 on the conduit string 49, thus providing communication between the mouth 75 and the inner concentric flow passageway 51.

A safety joint 80 is located between the ends of the inner length of pipe '74 to produce a separation of the conduit pipe string 49 adjacent the lowest part thereof, that is, within the drill bit 55 in case an excessive torque is applied on the conduit pipe string 49.

A drill collar 81 comprises a tube 82 of similar diametrical dimensions as the body of the drill string pipes 33 and has a radial coupling flange 83 fixed to the lower end thereof which matches and is bolted to the bit coupling flange 63. A suitable ring seal 84 is located between the respective flanges 83 and 63 in high pressure contact caused by the bolts 85 urging the respective coupling flanges toward each other. The ring seal 84 prevents the escape of fluid from between said latter flanges.

The drill collar tube 82 terminates at the upper end 86 thereof in a drill string pipe box collar 87 which is spaced below the box collar 88 on the lowermost conduit string pipe 89, that is, the inner pipe coupled to the drill bit inner length of pipe 74. The box collar 87 threadedly receives the lowermost drill string pipe pin collar 90 for supporting and driving the drill bit 55 and producing communications between the outer flow passageway 52 and the chamber 62.

Tubular or ring-shaped weights 91 have an inside diameter slightly greater than the outside diameter of the drill collar tube 82 and are telescoped over said latter tube and rest on the drill collar flange 83 for transmitting the weight thereof to the drill bit 55. The weights 91 may be suitably coupled together by bolts such as at 92 and the uppermost weight 91, in the illustrated example, has a conical-shaped upper surface 93 to aid in withdrawing the drill bit from the shaft or bore 2 with a minimum of interference.

The threads joining the respective outer or drill string pipes 33 are of opposite hand from the threads joining the inner or conduit string pipes 34 whereupon the conduit string may be rotated by the drill string through the bit rather than directly from the kelly outer pipe 10. The respective conduit string pipes 34 and drill string pipes 33 are of substantially equal length whereby each conduit string pipe box collar 44, that is the upper end of each conduit string pipe 34, extends above the corresponding drill string pipe box collar 36. This is due to the relative positions of the respective conduit and drill string box collars 78 and 87 associated with the bit inner length of pipe 74 and the drill collar 81. Thus, as described more fully below, as the dual pipe string is assembled and disassembled, the respective conduit string pipe joint is exposed for grasping and manipulation as best illustrated in FIG. 5.

Referring to FIGS. 2 and 3, two accessory tools are depicted which are useful in the practice of this invention. They are respectively a male pipe thread protector 94 and an inner tube suspending plug 95. The protector 94 is in the shape of an inverted cap having an internal thread 96 adapted to threadedly engage the respective drill string pin collar 44]. The protector 94 includes an upwardly projecting inner cone 97 terminating in a shoulder 98 and pin 99 for receiving the respective conduit string pin collar 4-7 and positioning same so that the conduit string pipe 34 is, with the aid of the wings 53, centered within the drill string pipe 33 and the conduit string box collar 44 is spaced above the drill string pipe box collar 36. The protector 9 preferably includes a central bore or passageway 100 through which a cable or other suspending member (not shown) may be inserted for handling the dual pipe section.

The suspending plug 95 comprises a cap member having a tapered and radially extending flange portion 101 adapted to be axially received in a drill string box collar 36 but not pass therethrough. The suspending plug 95 includes an inner depending pin 192 having tapered threads 153 at the lower end thereof for threadedly receiving a conduit string box collar 44 for suspending a conduit stringpipe 34 Within a drill string pipe 33 in a position whereby the conduit string pin collar 47 projects below the respective drill string pin collar 40. The suspending plug 95 includes a suitable bore or passageway 104 through which a cable or other suspending member (not shown) may pass for convenience in handling. The utility of the thread protector 94 and suspending plug 95 is noted below.

In conducting a drilling operation, the drill bit 55 is placed on a horizontal surface with the cutters 65 extending downwardly. In this position, the inner length of pipe 74 extends above the coupling flange 63. The drill collar 81 is picked up. When picked up, the drill collar 81 contains therewithin a conduit string pipe 34 suspended by a suspending plug 95 which causes the respective conduit pipe pin collar 47 to project below the drill collar coupling flange 83. With the box collar 78 on the bit pipe '74 projecting freely upwardly and the conduit string pipe pin collar 47 projecting freely downwardly from the coupling flange 83, the respective box and pin collars are easily grasped by known tools to form a joint therebetween. The drill collar is then lowered and the coupling flange 83 bolted to the coupling flange 65 of the bit 55. The lowering of the drill collar 81 causes the upper end or box collar 88 of the first conduit string pipe 34 to project above the box collar 87 of the drill collar 81. The weights 91 may be telescoped over the drill collar 81 at this time or prior to lifting the drill collar as desired. The bit and drill collar assembly is then lowered into the shaft or bore 2 until the upper end of the drill collar is positioned at the upper surface of the rotary drive table 6, suitable conventional slips (not shown) being used to suspend same therefrom.

The inner tube suspending plug 95 is then removed from the first conduit string pipe and placed in the next dual string section to be installed. The male pipe thread protector 94, which is used in storing the loose dual string sections, is removed, thus permitting the conduit pipe 34 to extend below the lower end of the respective drill pipe 33 as the inner tube suspending plug 95 engages the drill string pipe box collar 36. The dual pipe section is then suspended over the center of the drive table 6 and because the upper and lower portions of the inner coupling are exposed as in FIG. 5, they are easily grasped for joining. The suspended drill string pipe 33 is then lowered to the position illustrated by the broken lines 155 (FIG. 5) and joined to the adjacent drill pipe box collar (either on the drill collar 31 or preceding drill pipe 33). It is apparent that as each dual pipe section is added, the upper end or box collar of the conduit pipe will be exposed for joining to a subsequent exposed lower end or pin collar of a conduit pipe 34 suspended from Within a drill pipe 33.

' The joining operation continues until the bit reaches the bottom or face 106 of the shaft or bore 2 and then the dual drive stem or kelly 5 is connected to the uppermost conduit pipe 34 and drill pipe 33 in the same manner. When the kelly outer pipe 10 is lowered to threadedly engage the uppermost drill pipe box collar as, the telescoping sealed joint 22 takes up the necessary longitudinal displacement of the kelly inner pipes 11. The slips (not shown) are removed in the normal manner from the drive table 5 and a conventional drive bushing 1t inserted to produce the driving engagement between the table 6 and the outer kelly pipe 10.

During the drilling operation, liquids, gases and/or mixtures of these fluids may be forced in various paths through the inner flow passageway 51, outer flow passageway 52 and the bore-drill pipe annulus 108. As a preferred example, a suitable drilling liquid may be pumped through the outer gooseneck 15 downwardly through the outer flow passageway 52 in the path illustrated by the arrows 1% at high pressure to produce very high velocity but relatively low volume jets 110 issuing from the tubes 56 which keeps the bottom or face 106 of the bore 2 washed free of cuttings for maximum drilling speed. The relatively low volume issuing from the tubes 66 is, however, insuflicient to produce the necessary velocity in the bore-drill pipe annulus 108 to lift the relatively large cuttings to the surface which is necessary for efficient drilling. In order to sufficiently increase the liquid velocity in the annulus 108, a large volume of drilling liquid is forced at relatively low pressures through the inner gooseneck 14, down the inner flow passageway 51, and out the open mouth 75 at the bit, as illustrated by the arrows 111, which latter fluid when combined with the jetting fluid produces the desired upward flow velocity in the annulus 108. The fluid in the annulus 108 subsequently issues from a pipe 112 communicating through the well head 4 at the surface. In one alternative flow pattern,,it might be desirable to greatly reduce the total volume of drilling liquid used but maintain sufficient velocity for carrying relatively large cuttings to the surface. In the latter case, a relatively high but generally static gas or liquid pressure may be maintained through the pipe 112 in the annulus 108 and the cuttings forced upwardly through the open mouth 75 and inner flow passageway 51 and out the inner gooseneck 14, the drilling liquid being pumped at high pressure and relatively low volume downwardly through the outer flow passageway 52.

During the drilling operation, the bit driving torque is transmitted by the rotary drive table 6 to the kelly outer pipe 10, drill pipe string 42 and drill collar 81 to the bit 55 and the conduit pipe string 49 rotates therewith passively through the connetcion with the bit inner pipe 74. The conduit pipe string 49 may rotate with respect to the stationary swivel head 8 either within the swivel head itself or within the telescoping joint 22 as desired. As noted above, the coupling threads on the drill pipe string are of opposite hand from the conduit pipe string to permit the above driving configuration without unscrewing the respective joints. It is to be understood, however, that other coupling configurations with or without threaded connectors may be used without departing from the scope of this invention. In making up or breaking apart the dual drill string apparatus and during the drilling operation, the guides or wings 53 maintain the inner conduit pipes substantially concentrically positioned within the drill pipes but do not interfere with the longitudinal sliding therewithin for exposing the inner conduit pipe joints. It will be appreciated that upon the removal and breaking apart of the dual drill stem the outer or drill pipe joint is first unscrewed and separated which exposes the inner or conduit pipe joint for grasping in order to properly unscrew. Further, if it is desired to remove the inner or conduit string from the drill pipe string, it is not necessary to break apart the respective joints of the drill pipe string, but rather the conduit string may be independently rotated for breaking the safety joint 80 whereupon the inner or conduit string may be lifted longitudinally without disturbing either the bit, drill collar or drill pipe string. Persons skilled in the drilling art will appreciate that other materials rather than drilling fluids may be pumped through the passageways abovedescribed, for example, compositions for cementing or plugging a shaft.

A modified form of swivel head assembly or dual kelly structure is illustrated in FIGS. 8 and 9 and differs from the kelly structure described above in the means for obtaining a variation in relative axial positioning of the pin collar 113 on the kelly inner pipe 114 with respect to the pin collar 115 of the kelly outer pipe 116. FIG. 8 illustrates the kelly structure in drilling position with the kelly inner pipe pin collar 113 urged upwardly past the outer pipe pin collar 115 by the inner pipe box collar 117 on the inner pipe string in response to engagement of the outer pipe box collar 118 with the outer kelly pipe pin collar 115. Instead of a telescoping joint 22 as described above (FIG. 7) the upward displacement of the pin collar 113 in the embodiment of FIGS. 8 and 9 is permitted by slidably displacing the entire kelly inner pipe 114 upwardly through a suitable seal structure 119 in the outer pipe gooseneck swivel assembly 120. The inner pipe gooseneck swivel assembly 121 is conventional except for freedom of vertical displacement with respect to the swivel assembly 120, referring to FIG. 9 the modified kelly structure is shown with the inner pipe collars 113 and 117 exposed in which position the inner pipe gooseneck swivel assembly may rest upon the seal structure 113 to support the kelly inner pipe 114.

An additional dual passageway drill bit configuration is illustrated in FIG. and comprises a body or housing 122 rotatably supporting three tiers of bits or cutters 123, 124, and 125 on respectively greater radii. An interior passageway 126 extends downwardly through the body or housing 122 and enlarges at 127 and 127 forming chambers which communicate respectively with discharge tubes 128 and 129. The tubes 128 and 129 open at the contact levels of the respective cutters 124 and 125. The passageway 126 opens downwardly at 130 adjacent the lower cutters 123. Fluid forced downwardly through the passageway 126 will discharge at the opening 130 and from the tubes 128 and 129 to clear cuttings adjacent the respective bits or cutters.

An eductor collar 131 includes a flange 132 bolted to the supporting flange 133 of the drill bit housing 122. An interior tube 134 communicates with the passageway 126 and extends upwardly coaxially within the eductor collar 131 defining an outer passageway 135, having a blind lower end 135'. The tube 134 terminates at the upper end thereof in a box collar 136 which is spaced upwardly from the flange 132 a distance which will result in the upward displacement of the inner tube joints with respect to the outer tube joints for access to said inner tube joints when breaking down or building up the drill string, as noted above with respect to the drill bit 55.

A sweep tube 137 is secured to the eductor collar 131 and communicates with the outer passageway 135 at one end 138 thereof. The other end 139 of the sweep tube opens downwardly and sweeps within the area 140 of high turbulence near the cutters. By controlling the pressure in the well bore 141, the discharge from the passageway 125 together with cuttings may be urged through the sweep tube end 139 into the outer passageway 135 and then upwardly through the outer string passageway 142 formed by a modified outer drill string section 143 and communicating with the passageway 135 at 144. The modified outer drill string section 143 has a weight 145 secured thereto having an upper conical surface 146 to aid in withdrawing the drill bit and a lower flange 147 secured by bolts to an upper flange 148 of the eductor collar.

It is to be understood that while certain forms of this invention have been illustrated and described, it is not to be limited to the specific method or arrangement of parts herein described and shown except insofar as such limitations are included in the claims.

What I claim and desire to secure by Letters Patent is:

1. In combination with earth drilling apparatus a vertical elongated kelly, a rotary drive table through which said kelly extends for rotating same, said kelly having an outer non-circular pipe engaging said drive table and an inner pipe of smaller diameter than the inside dimensions of said kelly outer pipe and extending longitudinally within said kelly outer pipe forming inner and outer concentric flow passageways within said kelly, said kelly outer pipe terminating at the lower end thereof in a drill string coupling collar, said kelly inner pipe terminating at the lower end thereof in a conduit string coupling collar, said kelly inner pipe having a longitudinally telescoping sealed joint spaced above said latter coupling collar permitting the longitudinal positioning of said latter coupling between a first position depending below said kelly outer pipe coupling collar and a second position spaced above said kelly outer pipe coupling collar.

2. Earth drilling apparatus including a vertically extending dual pipe string, said dual pipe string comprising a plurality of connected outer pipes and a plurality of connected inner pipes of smaller outside diameter than the inside diameter of said outer pipes and contained within said outer pipes, said outer pipes each terminating at the upper and lower ends thereof in outer pipe coupling members, said inner pipes each terminating at the upper and lower ends thereof in inner pipe coupling members, said inner pipes individually being longitudinally s-lidable and rotatable with respect to adjacent outer pipes, means for longitudinally positioning said inner pipes with respect to said outer pipes whereby the uncoupling of a pair of outer pipe coupling members exposes a coupled pair of inner pipe coupling members for grasping, a dual kelly having an outer pipe with a lower coupling member normally coupled to said connected cuter pipes, said dual kelly having an inner pipe with a lower coupling member coupled to said connected inner pipes and normally positioned above said outerpipe lower coupling member, and a longitudinal sliding seal structure cooperating between said kelly inner and outer pipes permitting longitudinal displacement between said kelly inner and outer pipes for exposing said inner pipe lower coupling member below said outer pipe lower coupling member when said kelly outer pipe coupling member is uncoupled.

References Cited by the Examiner UNITED STATES PATENTS Canfield 175-215 Covender 175-320 Steele 17570 Thompson 175320 Murphy 175215 CHARLES E. OCONNELL, Primary Examiner. J. A. LEPPINK, Assistant Examiner.

Claims (1)

1. IN COMBINATION WITH EARTH DRILLING APPARATUS A VERTICAL ELONGATED KELLY, A ROTARY DRIVE TABLE THROUGH WHICH SAID KELLY EXTENDS FOR ROTATING SAME, SAID KELLY HAVING AN OUTER NON-CIRCULAR PIPE ENGAGING SAID DRIVE TABLE AND AN INNER PIPE OF SMALLER DIAMETER THAN THE INSIDE DIMENSIONS OF SAID KELLY OUTER PIPE AND EXTENDING LONGITUDINALLY WITHIN SAID KELLY OUTER PIPE FORMING INNER AND OUTER CONCENTRIC FLOW PASSAGEWAYS WITHIN SAID KELLY, SAID KELLY OUTER PIPE TERMINATING AT THE LOWER END THEREOF IN A DRILL STRING COUPLING COLLAR, SAID KELLY INNER PIPE TERMINATING AT THE LOWER END THEREOF IN A CONDUIT STRING COUPLING COLLAR, SAID KELLY INNER PIPE HAVING A LONGITUDINALLY TELESCOPING SEALED JOINT SPPACED ABOVE SAID LATTER COUPLING COLLAR PERMITTING THE LONGITUDINAL POSITIONING OF SAID LATTER COUPLING BETWEEN A FIRST

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