US3664443A

US3664443A - Dual circulation bumper subs

Info

Publication number: US3664443A
Application number: US880751A
Authority: US
Inventors: John David Campbell
Original assignee: Walker Neer Manufacturing Co Inc
Current assignee: Walker Neer Manufacturing Co Inc
Priority date: 1969-11-28
Filing date: 1969-11-28
Publication date: 1972-05-23
Anticipated expiration: 1989-05-23

Abstract

A dual circulation bumper sub comprising an outer, hollow tubular member connectable to outer tube of a string of dual tube pipe and an inner, hollow tubular member disposed inside the outer tubular member and connectable to the inner tube of a dual tube pipe string. The outer and inner tubular members have slip joints to allow vertical expansion of both the inner and outer tubular members without destroying the torque transmitting capability or the dual circulation characteristics of the dual string drilling pipe.

Description

United States Patent Campbell 5] May 23, 1972 54] DUAL CIRCULATION BUMPER SUBS 3,283,835 11/1966 Kellner ..175/215 x 3,311,180 3/1967 Gilreath et a1. ..175/321 X [72] Dam] Campbell Fans 3,319,726 5/1967 Brown ...175/321 x [73] Assignee: Walker-Neer Manufacturing Co., Inc., 3,329,221 7/1967 Walker ...l75/321 X Wichita Falls, Tex. 3,354,950 11/1967 Hyde ..175/32l X 2 F] d: N 2 1969 [2 1 l e m Primary Examiner-James A. Leppink 1 pp 880,751 Attomeyl-loward E. Moore and Gerald G. Crutsinger 52 us. c1 ..175/293, 175/215, 175/321 [57] ABSTRACT [51] f "Ezlb 1/10 E21 b 17/00 A dual circulation bumper sub comprising an outer, hollow tu- [58] Fleld of Search 175 215, 293, 321; 64/23; hula, member connectable to outer tube f a swing f dual 285/302 tube pipe and an inner, hollow tubular member disposed inside the outer tubular member and connectable to the inner [56] Reerences cued tube of a dual tube pipe string. The outer and inner tubular P have to expansion both the inner and outer tubular members w1thout destroymg the MCCllntOCk t X tor ue tran mitting ca ability o the dual circulation charac- 9 3 1 1962 teristics of the dual string drilling pipe. 3,225,566 12/1965 3,259,198 7/1966 14Clains, l6 DrawlngFlgures PATENTED MM 2 3 I972 SHEET 5 OF 5 BY 2M ATTURNEYS' DUAL CIRCULATION BUMPER SUBS BACKGROUND OF INVENTION In conventional rotary drilling, a long string of drill pipe having a cutting bit at the lower end thereof is rotated to grind its way through the earth. Bumper subs are installed in the drill string to provide a joint capable of vertical expansion and contraction during drilling, fishing and testing operations.

Bumper subs serve several important functions. In both offshore and inland drilling operations bumper subs are employed to maintain accurate weight control on the bit by installing a predetermined weight of drill collars in the string of drill pipe below the bumper subs. This maintains the string of drill pipe above the bumper sub in tension while maintaining a constant downward force on the drill bit.

The telescopic connection in a bumper sub compensates for vertical movement of floating drilling platforms employed in offshore drilling operations while maintaining a constant controlled weight on the drill bit.

The telescopic connection in a bumper sub also provides a means for exerting a quick upward or downward blow to free a string of drill pipe which is stuck in caving formations.

Heretofore, no suitable bumper sub had been developed for use in drilling operations which employed dual drill pipe with drilling fluid being circulated down through the annulus between the pipes and up through the inner tube carrying cuttings and cores to the surface. Such drilling operations are described in Henderson, U. S. Pat. No. 3,208,539, dated Sept. 28, 1965; and Elenburg, U. S. Pat. No. 3,416,617, dated Dec. 17, 1968; and U. S. Pat. No. 3,4l9,092,dated Dec. 31, 1968.

The use of concentric dual passage drilling pipe is advantageous in many operations because of the continuous supply of core samples or chips which may be laid out on the surface in the exact order penetrated to provide valuable engineering data. The use of concentric dual passage drill pipe offers significant advantages over conventional single passage drill pipe for drilling through areas in which loss of circulation of drilling fluid occurs from the induced fracturing of formations by the pressure exerted by the drilling fluid on the fonnation. Use of concentric dual passage drill pipe also significantly reduces the cost of drilling in cavernous formations.

The non-availability of a suitable bumper sub for use with dual concentric drill pipe had heretofore prevented realization of the full advantage of a highly efficient drilling method in operations which required the use of bumper subs.

SUMMARY OF INVENTION I have developed a bumper sub for use with concentric dual passage pipe adapted for drilling with reverse circulation.

The bumper sub comprises an inner tubular member which has a sliding joint to allow the length of the inner tubular member to be varied. An outer tubular member is disposed around the inner tubular member, said outer tubular member having a sliding joint therein to varv the length of the outer tu' bular member. The sliding joint in the inner tubular member may be disposed either above or below the upper ends of the outer tubular member. Positioning of the slip joint in the inner tubular member above or below the ends of the outer tubular member allows the outer tubular member to be constructed with wall thicknesses capable of transmitting torque without requiring that the outside diameter of the outer tubular member be greatly in excess of the outside diameter of the dual concentric tubing string. Positioning the slip joint in the inner tubular member above or below the body of the outer tubular member also minimizes the required inside diameter of the outer tubular member without obstructing flow of drilling fluid through the annular passage between the inner and outer tubular members.

In certain drilling operations the sliding joint in the inner tubular member may be located inside the outer tubular member if there is sufficient internal clearance to accommodate the slip joint in the inner tube without restricting the annular flow passage.

It is therefore a primary object of the present invention to provide a dual concentric passage bumper sub for use in a long string of dual concentric passage drill pipe.

A further object of the invention is to provide a dual concentric passage bumper sub having a'slip joint in the inner tube of the bumper sub wherein the slip joint is positioned relative to the outer body of the bumper sub such that the slip joint will not materially obstruct the annular passage between the inner'and outer tubular members.

A still further object of the invention is to provide a dual concentric passage bumper sub having an outside diameter of approximately the same dimensions as dual concentric passage drill pipe connected thereto.

A still further object of the invention is to provide an attachment for a conventional bumper sub designed for use in conventional drill pipe for converting said conventional bumper sub for use with dual concentric drill pipe without materially reducing the flow rate of drilling fluid through the dual concentric drill pipe.

A still further object of the invention is to provide a dual concentric passage bumper sub for use with dual concentric passage drill pipe having a relatively soft metal wear ring in the slip joint of the inner tube to prolong the life of the inner tube.

Other and further embodiments of the invention will become apparent upon referring to the detailed description hereinafter following and to the drawings annexed hereto.

DESCRIPTION OF THE DRAWING Drawings of preferred embodiments of the invention are annexed hereto so that the invention may be better and more fully understood, in which:

FIG. I is a side elevational view of a bumper sub in a dual concentric passage string of drill pipe, the slip joint in the inner tube being disposed below the slip joint in the outer tube;

FIG. II is a side elevational view similar to FIG. I with the bumper sub in the open position;

FIG. III is a cross sectional view taken along line III-III of FIG. I; 7

FIG IV is a side elevational view of a modified form of a bumper sub in a string of dual concentric passage drill pipe, the slip joint in the inner tube being disposed above the slip joint in the outer tube;

FIG. V is a side elevational view similar to FIG. IV, the bumper sub in the open position;

FIG. VI is a cross sectional view taken along line Vl-VI of FIG. IV; FIG. VII is a side elevational view of another modified form of a bumper sub in a string of dual concentric passage drill pipe, the slip joint in the inner tube being disposed inside the slip joint in the outer tube;

FIG. VIII is a side elevational view similar to FIG. VII with bumper sub in the open position;

FIG. IX is an enlarged cross sectional view taken along line IX-IX of FIG. VII;

FIG. X is an enlarged cross sectional view taken along line X-X of F IG. 111;

FIG. X1 is an enlarged cross sectional view taken along line XI-XI of FIG. 111;

FIG. XII is an enlarged cross sectional view taken along line XII-XII of FIG. III;

FIG. XIII is an enlarged cross sectional view taken along line XIII-XIII of FIG. V1;

FIG. XIV is a partially sectionalized view of another modified form of a bumper sub;

FIG. XV is an enlarged cross sectionalview taken along line XV-XV of FIG. XIV; and

FIG. XVI is an enlarged cross sectional view taken along line XVI-XVI of FIG. XIV.

Numeral references are employed to designate like parts throughout the various figures of the drawing.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIGS. I-III of the drawing the numeral 1 generally designates a dual concentric passage bumper sub comprising an outer, hollow tubular member 8 and an inner hollow tubular member 40.

The outer tubular member is sectionalized and comprises a barrel 2 and a mandrel 6. Barrel 2 has a longitudinally extending bore 4 therethrough and mandrel 6, slidably disposed in said bore 4 in barrel 2 provides a slip joint 7 which is a means to vary the length of the outer, hollow tubular member 8. The mandrel 6 has a bore 10 extending longitudinally therethrough. It should be readily apparent that bore 10 in mandrel 6 and bore 4 in barrel 2 form a longitudinally extending passage through the outer, hollow tubular member 8.

The mandrel 6 is slidably disposed in barrel 2 and a drive sleeve 12 is threadedly secured at 14 to the lower end of barrel 2. Drive sleeve 12 has splines 16 disposed about the inner surface thereof in interengaging relation with splines 18, about an outer surface of mandrel 6. Splines 16 on mandrel 6 are tele scopicallv disposed in interengaging relation with splines 18 in barrel 2 forming a slip joint 7 to allow vertical expansion of the bumper sub 1 without destroying the torque transmitting capability of the string of drill pipe 20.

The upper end of barrel 2 is detachably secured by a threaded connection 22 to a top sub 24 having its upper end detachably secured by a threaded connection 26 to the lower end of outer pipe 28 of a dual concentric tubing string 30.

The lower end of mandrel 6 is detachably secured by a threaded connection 32 to the upper end of the outer pipe 34 of lower dual concentric tubing string 20.

A packing nut 36 is threadedly connected at 37 to the upper end of mandrel 6 to grippingly engage packing 38, forcing said packing into sealing engagement with the inner surface of bore 4 to prevent leakage of drilling fluid between the outer surface of mandrel 6 and the inner surface of barrel 2.

An inner, hollow tubular member 40 comprises an upper slip tube 42 and a lower slip tube 44, telescopically disposed through a portion of the length forming a slip joint 41 thereof, and extends longitudinally through bore 4 in barrel 2 and bore 10 in mandrel 6.

As best illustrated in FIG. III of the drawing, upper slip tube 42 has spacers 46 welded or otherwise rigidly secured to an upper portion thereof, said spacers being rigidly secured to inner tube anchor bracket ring 48, the lower edge of which engages the upper edge of shoulder 50 which extends inwardly into bore 25 extending longitudinally through top sub 24. A hollow retaining screw 52 is detachably connected by threads 53 to upper anchor sub 24 to prevent vertical movement of ring 48. A snap ring 54 is secured in an annular groove 56 in the bore 25 of upper anchor sub 24 to prevent loosening of retaining screw 52.

From the foregoing it should be readily apparent that the inner

tube anchor bracket

46, 48, 52, and 54 provides a means for securing the upper slip tube 42 relative to the upper end of the outer tubular member 8 of bumper sub 1 to prevent longitudinal movement of upper slip tube 42 relative to the upper end of bumper sub 1.

Inner tube spacers 58 are welded or otherwise rigidly secured to upper slip tube 42 at spaced intervals along the length thereof for maintaining upper slip tube 42 in concentric axial alignment with bore 10 through mandrel 6 of the bumper sub 1. As best illustrated in FIG. III of the drawing, spacers 58 are disposed in a spiral arrangement around upper slip tube 42 to efficiently distribute drag forces exerted by drilling fluid flowing thereacross around the surface of the pipe and to maintain desired ductility of the tube. If spacers 58 were welded in straight lines down the length of the pipe the localized heating as a result of welding the spacers to the tube could result in excessive brittleness of the tube along the line of welds. Positioning spacers 58 in a spiral pattern assures that the upper slip tube will be maintained in concentric relation to the bore 10 through mandrel 6 without materially reducing the strength of the slip tube.

A bottom anchor sub 60 is detachably secured by threaded connection 62 to the lower end of the outer pipe or drill collar 34. Bottom anchor sub 60 has a shoulder 64 which extends inwardly into bore 66 which extends longitudinally therethrough for receiving an inner tube anchor bracket ring 48, as hereinbefore described, which is supported by spacers 46, welded or otherwise rigidly secured to lower slip tube 44.

From the foregoing it should be readily apparent that lower slip tube 44 is anchored relative to mandrel 6 and moves longitudinally therewith relative to outer barrel 2 and upper slip tube 42.

Suitable sealing means, such as O-rings 68, is disposed between the outer surface of lower slip tube 44 and the inner surface of upper slip tube 42 to prevent leakage of drilling fluid therebetween.

The lower end of bottom anchor sub 60 is detachably secured by threaded connection 68 to a drill collar 70 in a string of concentric drill pipe.

The upper end of upper slip tube 42 is secured through a coupling 72 (FIGS. III and XI) to the lower end of the inner tube 74 of dual concentric upper tubing string 30. The lower end of lower slip tube 44 is secured through a coupling 72 to the upper end of inner tube 76 of lower dual concentric tubing string 20.

An enlarged cross sectional view through one of the couplings72 is illustrated in FIG. XI of the drawing. It should be noted that the upper end of tube 76 is slidably disposed in an enlarged end portion 78 of lower slip tube 44. Suitable sealing means, such as O-ring seals 80, is disposed in annular grooves 82 in the enlarged end portion 78 and is disposed in sealing engagement with the outer surface of tube 76. It should be noted that tube 76 when telescopically disposed in the enlarged end portion 78 of tube 74 is free of axially interengageable stop surfaces which would prevent a limited range of relative axial movement between the respective tubes. Such a connection facilitates simultaneous coupling of outer tubular members and inner tubular members and provides ample compensation for thermal expansion and contraction of the inner tubular members.

From the foregoing it should be readily apparent that I have developed a bumper sub having an annular passage 11 and a concentric passage 13 together with

means

7, 41 for expanding the bumper sub longitudinally to vary the length thereof without destroying the torque transmitting capability thereof.

DESCRIPTION OF A SECOND EMBODIMENT A second embodiment of the invention is illustrated in FIGS. IVVI and XIII. The second embodiment of the invention is very similar to the embodiment illustrated in FIGS. IIII, except that the slip joint 41 between the upper and lower slip tubes is disposed above the barrel 2 of bumper sub 1. Such can be readily accomplished by breaking threaded connections 32 and 62 (see FIG. lII)and removing drill collar 34. The upper end of bottom anchor sub 60 is then threaded onto the lower end of mandrel 6.

The outer tubular components comprising barrel 2 and mandrel 6 of the bumper sub 1 are identical to those hereinbefore described.

Top sub 24' is threadedly secured to the upper end of barrel 2 and has a section of drill pipe 29 threadedly secured to the upper end thereof. The upper slip tube 142 has an enlarged portion 142a on the lower end thereof and the upper end of lower slip tube 144 is telescopically disposed in said enlarged portion. Sealing means 168, best illustrated in FIGS. VI and XIII of the drawing, comprises a lantern ring 168a disposed between vee packing 168k which is maintained in sealing engagement with the outer surface of lower slip tube 144 and the inner surface of upper slip tube 142 between upper packing ring 1680 and lower packing ring 168d. Set screws I68e disengageably secure the upper and lower packing rings to lower slip tube 144 and prevent longitudinal movement of the packing rings relative to the lower slip tube.

Seal means 168 is capable of withstanding greater pressures than O-rings 68, hereinbefore described and illustrated in FIG. X of the drawing. It is desirable to employ sealing means of the type generally designated by the number 168 where the internal dimensions of the outer tubing 128 are large enough to accommodate the enlarged portion 1420 of upper slip tube 142 without significantly reducing the annular flow passage 111.

The embodiment of the invention illustrated in FIG. VI of the drawing is preferred over the embodiment illustrated in FIG. III under conditions where it is possible to use same because the drift of the tube bores made in a drill collar result in a ridge which causes alignment problems in a snugly fitting telescopic connection as illustrated in FIG. III.

Spacers 158 are disposed in spaced apart relation around the enlarged portion 1420 of upper slip tube 142 to maintain the upper slip tube in coaxial concentric alignment with outer drill pipe 128.

DESCRIPTION OF A THIRD EMBODIMENT A third embodiment of the invention is illustrated in FIGS. VII-IX of the drawing. The third embodiment of the invention is similar to the embodiments hereinbefore described, the primary difference being in the positioning of the telescoping slip joint 241, which in the third embodiment is positioned inside bore of mandrel 6 of bumper sub 1.

A bottom anchor sub 60 is threadedly secured to the lower end of mandrel 6 and inner tube anchor bracket ring 48 is secured thereto, as hereinbefore described to support lower slip tube 244. Coupling 72 on the lower end of lower slip tube 244 is employed to connect said slip tube to the upper end of an inner tube of dual concentric tubing string.

A drill collar 228 is threadedlv secured to the upper end of top sub 224 which has its lower end threadedly secured to the upper end of barrel 2 of bumper sub 1. Upper slip tube 242 is suspended from inner tube anchor bracket ring 48 in the upper end of drill collar 228.

Lower slip tube 244 is slidably disposed in upper slip tube 242 and suitable sealing means, such as O-rings 268, seals the space therebetween.

Spacers 258 maintain

slip tubes

242 and 244 concentricallv aligned in the bore 10 of mandrel 6.

Slip joint 241 may be disposed inside mandrel 6 under circumstances where it is deemed expedient to do so if there is sufficient internal clearance in bore 10 to accommodate the slip joint. In most drilling operations, if the outside diameter of mandrel 6 and barrel 2 are to be maintained at approximately the same diameter as that of the tubing string and drill collars, the inside diameter of bore 10 through mandrel 6 will necessarily be smaller than the diameters of bores through the drill pipe and drill collars. This results from the necessity of making the walls of barrel 2 and mandrel 6 thicker than that the conventional tubing string to allow space for the splined connection which is capable of transmitting torque from the upper end of the string of drill pipe to the bit at the lower end thereof.

In most drilling operations positioning slip joint 241 inside bore 10 of mandrel 6 would result in excessive reduction of the area of the annular flow passage 211 around the outside of upper slip tube 242.

DESCRIPTION OF A FOURTH EMBODIMENT A fourth embodiment of the invention, illustrated in FIGS. XIV-XVI, is similar to the embodiments hereinbefore described, except that the inner tube slip joint assembly 340 illustrated therein is arranged to be employed in combination with a conventional single passage bumper sub 301 to convert said conventional bumper sub to a dual concentric passage bumper sub.

A conventional single passage bumper sub 301 has a top sub 324 secured to the upper end thereof by a threaded connection 322.

An upper slip tube 342 is suspended from top sub 324 by an inner tube anchor bracket ring 348 and said upper slip tube extends downwardly through the bore of the conventional bumper sub 301. Suitable splice collars 342s may be employed to connect standard lengths of tubing to form desired longitudinal dimensions.

Spacers 358 are disposed along the length of upper slip tube 342 for maintaining said upper slip tube in concentric relation to the bore through conventional bumper sub 301.

As best illustrated in FIGS. XIV and XV, a packing sub 385 is detachably secured by a threaded connection 386 to the lower end of the conventional bumper sub 301. The lower end of packing sub 385 is detachably secured by a threaded connection 387 to the upper end of slip joint sub 390.

Lower slip tube 344 is suspended from an inner tube anchor bracket ring 348 in the upper end of slip joint sub 390. The upper slip tube 342 extends downwardly through the bore of conventional single passage bumper sub 301 and is telescopically disposed in the bore 345 of lower slip tube 344.

Suitable sealing means 368 is rigidly secured to the lower slip tube 344 to prevent leakage between the outer surface of upper slip tube 342 and the inner surface of lower slip tube 344.

Sealing means 368 comprises a packing cup 3680 welded or otherwise rigidly secured at 368b to the upper end of lower slip tube 344. Packing 3686 is disposed in an annular chamber 368ain packing cup 368a and has bushings 368d in pressing engagement with the upper and lower surfaces thereof urging the packing material 3680 in pressing relation with a lantern ring 368e. A stuffing nut 368f is detachably secured in the upper end of packing cup 368a by a threaded connection 368g to exert pressure to urge packing 3680 into sealing engagement with the upper and lower slip tubes. A wiper ring 369 is disposed in an annular groove 369a adjacent the upper end of stuffing nut 368f to prevent entry of solid matter into the space 368h between upper slip tube 342 and lower slip tube 344. Set screws 368k are employed to lock stuffing nut 368f relative to packing cup 368a to prevent loosening of the stuffing nut.

Packing sub 385 has a bore 385a extending longitudinally therethrough. An enlarged flow passage 3851) is formed intermediate opposite ends of the bore 385a to maintain the flow rate of drilling fluid at substantially constant rate as said fluid flows down the annular passage 311, through bore 385a, and through flow passage 385b to prevent obstruction of the flow of the fluid as it moves around sealing means 368.

The lower end of upper slip tube 342 has means disposed thereabout to minimize metal to metal wear between the surfaces of the

slip tubes

342 and 344. In the particular embodiment of the invention illustrated in FIGS. XIV and XVI of the drawing, the means to minimize wear is a relatively soft wear ring 392 secured to upper slip tube 342. Wear ring 392 is constructed of softer metal than lower slip tube 344 and said ring is positioned so as to be economically replaceable when it is necessary to do so.

A coupling 72, hereinbefore described with relation to FIG. IX, is welded or otherwise rigidly secured to the lower end of lower slip tube 344 and has O-rings and 82 disposed therein to telescopically receive and seal about inner tube of dual concentric drill pipe.

From the foregoing description of four embodiments of my invention, it should be readily appreciated that one or more of the described embodiments may be better suited for a specific operation depending upon the specific operating conditions.

Though it is very undesirable to do so, it is often necessary to employ drill collars above a bumper sub to minimize the possibility of pumping the sub open by circulation pressures during drilling operations. However, when a pressure balanced bumper sub is utilized there is no particular necessity for adding weight above the expanding joint, but conventional single passage pressure balanced bumper subs are quite com plex and cannot be efficiently serviced in the field.

If a pressure balanced bumper sub is utilized the slip joint 41 in the inner slip tubes is preferably installed above the bumper sub and in a section of drill pipe which normally has a greater inside diameter than the inside diameter of a drill collar or the passage through a bumper sub.

The embodiments illustrated in FIGS. VI, XIII and IX provide operational pressure characteristics which enhance the operational characteristics of bumper sub 1. Conventional bumper subs tend to pump open because there is a pressure differential between the fluid inside the sub and the fluid in the annulus in the hole outside the sub. The greater the differential fluid pressure, the greater the tendency of the sub to open or expand.

Referring to FIG VI, it be noted that fluid pressure in annular passage 111 exerts a downward force, indicated bv arrow P,, on the upper end of packing nut 36 tending to move mandrel 6 downwardly relative to barrel 2. The magnitude of force P is equal to the projected horizontal area of packing nut 36 times the pressure in the passage 111. The downwardly directed force on the bit at the lower end of the drill string can be similarly computed.

Fluid moving upwardly through the

inner tubes

142 and 144 is at lower pressure than fluid moving downwardly through annular passage 111 because of the resulting pressure drop across the bit nozzle (not shown) and because circulating fluid is lost around the bit, the quantity depending upon the characteristics of the formation through which drilling is being accomplished and the efficiency of packing or sealing devices employed between the drilling string and the walls of the well.

Pressure of fluid in passage 111 is applied through annulus 143 to exert an upwardly directed force P on lower packing ring 168d of seal 168. Since seal 168 is secured through lower slip tube 144, anchor bracket ring 48, and bottom anchor sub 60 to mandrel 6, the upwardly directed force P opposes the downwardly directed force P to reduce the tendency of the sub to be pumped open.

The reduced pressure in passage 113 exerts a downward force I on upper packing ring 1680 of seal 168. However, force P is of smaller magnitude than forces P and P It should be readily apparent that seal means 168 and annular passage 143 may be of dimensions to constitute means for sealing between upper and

lower tubes

142 and 144 and also constitute pressure actuated means to substantially equalize resultant vertical pressure initiated forces to prevent opening or extending of the bumper sub 1 as a result of the pressure differential between the passage 1 11 and passage 1 13. i It should also be readily apparent that force I causes the inner tube 144 to be maintained in tension which allows the walls of the inner tube to be much thinner, providing maximum cross-sectional area for the flow passages, than would be feasible if said tube were in compression since it is a long unsupported column.

The lower end of the enlarged portion 142a of upper tube 142 opens to the pipe annulus, passage 111, which under normal operating conditions is free of chips and earth cuttings minimizing scoring of the inside sealing surface of the enlarged portion 142a of the upper tube 142.

The embodiment illustrated in FIG. IX offers the same pressure balancing characteristics hereinbefore described in relation to the embodiment illustrated in FIG. VI.

The selection of a particular tvpe of sealing means to be employed between the upper and lower slip tubes evolves primarily from a careful consideration of the dimensions of tubing strings, the required flow rate of drilling fluid necessitated for the particular drilling operation, and necessity for pressure balancing capabilit However, it should be readily appreciated that I have developed a dual passage bumper sub which allows the advantages of reverse circulation through dual concentric drilling strings to be realized in drilling operations which require the use of a bumper sub.

Having described may invention I claim:

1. Dual passage expandible pipe comprising, in combination, an expandible outer tubular member having a bore extending longitudinally therethrough; torque transmitting means secured between opposite ends of the outer tubular member; an upper slip tube; means to suspend an upper end of said upper slip tube in an upper end of the outer tubular member; a lower slip tube; means in the lower end of the outer tubular member for securing a lower end of the lower slip tube; a slip joint between the upper and lower slip tubes; means for securing the outer tubular member and slip tubes to a string of dual passage drill pipe and surfaces on said lower slip tube arranged such that fluid pressure in the annular passage between the outer tubular member and the slip tubes exerts an upward force acting through the lower slip tube tending to shorten the outer tubular member.

2. The combination called for in claim 1 wherein the upper slip tube and the lower slip tube are telescopically disposed one inside the other to form a slip joint; and with the addition of sealing means in pressure contact with surfaces of the upper and lower slip tubes to prevent passage of fluid therebetween.

3. The combination called for in claim 2 with the addition of a wiper ring carried by one of the slip tubes in wiping engagement with a surface of the other slip tube to prevent the entr of solid particles into the sliding connection.

4. The combination called for in claim 2 with the addition of an enlarged flow passage intermediate opposite ends of the bore through the outer tubular member, said enlarged flow passage being disposed about the sealing means.

5. The combination called for in claim 2 wherein the outer tubular member is a bumper sub, said bumper sub having a bore extending longitudinally therethrough; wherein one of the slip tubes extends through the bore of the bumper sub.

6. A string of dual concentric passage drill pipe comprising, in combination, dual concentric drill pipe having an inner tube and an outer tube; a bumper sub connected to the drill pipe, said bumper sub having a bore extending therethrough; a first expanding joint in said bumper sub for varying the length between opposite ends of the bumper sub, said expanding joint being adapted to transmit torque; an inner tube extending longitudinally through the bore of said bumper sub; a second expanding joint in the inner tube vertically spaced from the bumper sub; means for securing a portion of the inner tube which extends through the bumper sub below the first expanding joint relative to the lower end of the bumper sub; and means for securing a portion of the inner tube which extends through the bumper sub above the first expanding joint relative to the upper end of the bumper sub; and surfaces on said inner tube arranged such that fluid pressure in the annular passage between the bumper sub and the inner tube exerts an upward force acting through the inner tube tending to shorten the bumper sub.

7. An attachment for a conventional torque transmitting bumper sub comprising a barrel and a mandrel disposed in telescopic relation and having a bore extending longitudinally therethrough comprising, in combination, a top sub connectable to the upper end of the barrel; an upper slip tube secured to the top sub arranged to extend through the bore of the barrel and mandrel of the bumper sub; a packing sub connectable to the lower end of the bumper sub; a lower slip tube secured relative to the packing sub, said bottom slip tube being adapted to be positioned in telescopic sliding relation with a portion of the upper slip tube which extends below the barrel and mandrel; means for sealing between the upper and lower slip tubes; surfaces on said lower slip tube arranged such that fluid pressure in the annular passage between the packing sub and the slip tubes exerts an upward force acting through the lower slip tube tending to shorten the bumper sub; and means on the top sub and the packing sub connectable to a string of dual passage drill pipe.

8. A pressure balanced dual passage bumper sub comprising, an outer hollow tubular member; vertically expandable torque transmitting means in said outer hollow tubular member; an inner hollow tubular member in said outer hollow tubular member, said inner and outer tubular members being arranged to form first and second flow passages; vertically expandable means in said inner tube; means securing opposite ends of the inner tubular member relative to ends of the outer tubular member; and surfaces on the inner tubular member having projected effective horizontal areas arranged such that fluid pressure in the annular passage between the inner and outer tubular members exerts an upward force acting through the inner tubular member tending to shorten the outer tubular member.

9. A pressure balanced dual passage bumper sub comprising, a barrel having a passage extending therethrough; a mandrel telescopically disposed in said barrel, said mandrel having a passage therethrough; interengaging means between the barrel and the mandrel allowing longitudinal movement between the barrel and the mandrel but preventing relative rotational movement; seal means between the barrel and the mandrel; an upper slip tube; means for securing the upper slip tube relative to the barrel; a lower slip tube telescopically disposed in the upper slip tube forming a joint, at least one of said slip tubes extending through both of the passages in the barrel and mandrel forming inner and outer concentric passages through the bumper sub, said joint being vertically spaced from the barrel and mandrel; packing retainers secured around the lower slip tube with packing grippingly secured therebetween to seal between the upper and lower slip tubes; surfaces on the seal means between the slip tubes, said surfaces being in fluid communication with each of the inner and outer concentric passages through the bumper sub; and wherein the mandrel has a surface on the upper end thereof, the effective horizontal projected areas of the surfaces on the packing retainers being greater than the effective horizontal projected areas of the surface on the upper end of the mandrel.

10. A dual concentric passage bumper sub comprising, a barrel having a longitudinally extending bore; a mandrel having an end slidably disposed in said bore in the barrel, said mandrel having a bore extending longitudinally therethrough; inter-engaging means between the barrel and the mandrel to transmit torque therethrough; means to secure an end of the barrel to an end of an outer pipe of tubing having dual concentric passages; means to secure an end of the mandrel to an end of an outer pipe of tubing having dual concentric passages; a continuous slip tube extending through the bores of the mandrel and the barrel, said slip tube having an end extending out of the barrel and mandrel and being slidably disposed in telescoping relation with an inner tube of tubing having dual concentric passages to form a sliding connection; means to secure the other end of the continuous slip tube to an end of an inner tube of dual concentric passage tubing; seal means between the mandrel and the barrel spaced from the inter-engaging means; packing retainers secured around the slip tube; packing grippinglv secured between the packing retainers and arranged to engage walls of the inner pipe of the tubing having dual concentric passages; and surfaces on at least one of the packing retainers positioned such that fluid pressure in the outer passage exerts an upward force acting through the slip tube tending to urge the mandrel into the barrel.

11. The combination called for in claim 10 wherein the sliding connection between tube and the inner tube is disposed above the upper end of the barrel and mandrel.

12. The combination called for in claim 10 wherein the sliding connection between the slip tube and the inner tube is disposed below lower ends of the barrel and the mandrel.

13. The combination called for in claim 10 with the addition of a wear ring around the end of the slip tube to maintain the surfaces of the slip tube and the inner tube in spaced apart relation.

14. The combination called for in claim 13 with the addition of a wiper ring secured between the slip tube and the inner tube, said wiper ring being adapted to prevent entry of foreign matter into space therebetween.

Claims

3. The combination called for in claim 2 with the addition of a wiper ring carried by one of the slip tubes in wiping engagement with a surface of the other slip tube to prevent the entry of solid particles into the sliding connection.

10. A dual concentric passage bumper sub comprising, a barrel having a longitudinally extending bore; a mandrel having an end slidably disposed in said bore in the barrel, said mandrel having a bore extending longitudinally therethrough; inter-engaging means bEtween the barrel and the mandrel to transmit torque therethrough; means to secure an end of the barrel to an end of an outer pipe of tubing having dual concentric passages; means to secure an end of the mandrel to an end of an outer pipe of tubing having dual concentric passages; a continuous slip tube extending through the bores of the mandrel and the barrel, said slip tube having an end extending out of the barrel and mandrel and being slidably disposed in telescoping relation with an inner tube of tubing having dual concentric passages to form a sliding connection; means to secure the other end of the continuous slip tube to an end of an inner tube of dual concentric passage tubing; seal means between the mandrel and the barrel spaced from the inter-engaging means; packing retainers secured around the slip tube; packing grippingly secured between the packing retainers and arranged to engage walls of the inner pipe of the tubing having dual concentric passages; and surfaces on at least one of the packing retainers positioned such that fluid pressure in the outer passage exerts an upward force acting through the slip tube tending to urge the mandrel into the barrel.