US3838953A

US3838953A - Downhole hydraulic motor suitable for roller bits

Info

Publication number: US3838953A
Application number: US00244035A
Authority: US
Inventors: C Peterson
Original assignee: Rapidex Inc
Current assignee: Rapidex Inc
Priority date: 1972-04-14
Filing date: 1972-04-14
Publication date: 1974-10-01
Anticipated expiration: 1991-10-01

Abstract

Downhole drill assembly with features achieving high power and long wear. A hydraulic vane motor combines vanes in stator, thrust-carrying rotor and thrust bearing at end opposite the output end. Compound thrust bearings are shown with both mechanical and hydraulic aspects. A recirculating hydraulic drive system independent of flushing fluid and a drive system using the flushing fluid are shown. A chamber of flushing fluid protects the lower end of the motor from cuttings and a removable wear sleeve protects the sides of the motor from cuttings while supplying the flushing fluid. A drill string assembly for such motor is of ''''H'''' crosssection with hoses retained in the recesses of the ''''H''''.

Description

United States Patent 1191 Peterson 1 DOWNIIOLE HYDRAULIC MOTOR SUITABLE FOR ROLLER BITS [52] US. Cl 418/186, 418/248, 173/73,

175/107, 308/9, 308/231 [51] Int. Cl F03c 3/00, E21b 3/12, Fl6c 17/10 [58] Field of Search 418/102, 150,181, 186,

3,592,570 7/1971 Harms 4182186 3,594,106 7/1971 Garrison 415/502 FOREIGN PATENTS OR APPLICATIONS 1,188,785 4/1970 Great Britain 1. 418/249 Primary Examiner.lohn J. Vrablik [5 7 ABSTRACT Downhole drill assembly with features achieving high power and long wear. A hydraulic vane motor combines vanes in stator, thrust-carrying rotor and thrust bearing at end opposite the output end. Compound thrust bearings are shown with both mechanical and hydraulic aspects. A recirculating hydraulic drive system independent of flushing fluid] and a drive system using the flushing fluid are shown. A chamber of flushing fluid protects the lower end of the motor from cuttings and a removable wear sleeve protects the sides of the motor from cuttings while supplying the flushing fluid. A drill string assembly for such motor is of H crosssection with hoses retained in the recesses of the 5H 12 Claims, 11 Drawing Figures DOWNHOLE HYDRAULIC MOTOR SUITABLE FOR ROLLER BITS BACKGROUND OF THE INVENTION This invention relates to drilling wells.

Wells are preferably drilled using roller bits to break out rock chips and extend the hole downward. These particular bits typically operate with a thrust of 7.000 lbs. per inch of diameter with typical diameters of 8 inches. The thrust on the bit as well as the torque to rotate it is conventionally carried by a rotating string of drill pipe attached to the bit and extending to the top of the hole. The drill string also conveys flushing fluid to the hole bottom to flush rock chips away from the bit. The flushing fluid then returns to the surface through an annular space between the drill string and the hole wall. The upper end of the drill string is rotated by appropriate machinery which permits the string to be advanced as the hole is extended. Periodically, how ever. the drilling must be interrupted in order to add an additional length of drill pipe to the string. The addition of drill pipe involves breaking the flushing line to the old string, screwing the additional length of pipe onto the string with a reasonably leak-tight joint, and connecting the flushing line to the augmented string. Furthermore, from time to time the whole drill string must be pulled from the hole to repair or replace the bit or for some other reason. This is conventionally done by repeatedly raising the string by one length, stopping and unscrewing the uppermost length from the string and raising again. In the aggregate of these operations, the time spent in screwing and unscrewing portions of the pipe string represents an important element of cost in drilling a well.

Downhole drill motors, where conditions permit use, have the advantage of requiring a stationary, not a rotary, drill string. But severe limitations on their usefulness have existed due to the hole size. The necessity of applying driving torque and axial thrust to the drill bit and introducing and removing drilling fluid, all in the confines of an eight inch hole have resulted in severe design compromises. Such motors have found use with diamond drills at speeds of 400 rpm or higher, power for which can be delivered without great torque, but have not been generally acceptable for driving the preferred roller bits at their characteristic low speeds, e.g., less than 150 rpm at high torque thrust and impact loading.

Objects of the present invention include: providing a downhole motor assembly capable of applying high thrust and torque suitable for driving a roller bit; providing such a motor assembly which is of relatively simple construction and comprised of durable components; providing drilling equipment that can be ad vanced into and removed from the hole more expeditiously; and effecting faster and less expensive drilling of holes.

According to the invention it is realized that a combi nation of a hydraulic motor with vanes in the stator together with location of the thrust bearing above the rotor enables the design of a greatly improved torque capacity downhole motor of simple construction. The torque carrying rotor is neither restricted in size or shape by the thrust bearing while its effective size is allowed to be larger by having the vanes in the stator. Load-carrying lands are preferably employed between axially spaced ports in the rotor. lln preferred embodiments the thrust bearing is of generous radial dimensions (unrestricted by the torque requirements of the rotor) and preferably it is a compound structure. prcferably with a mechanical hearing and a hydraulic thrust means. the latter utilizing hydraulic pressure of the drill system.

In preferred embodiments a plurality of discrete circumferentially elongated ports are spaced from each other along the rotor length; the central rotor is symmetrical having major and minor diameter circular portions with intervening sloped portions. the ports more than spanning the latter; the internal passages are centered on the axis or are placed in the larger diameter 5 portions of the rotor; the rotor is a one piece. high-load carrying member; and the stationary housing has a passage, as for flushing fluid. In a closed hydraulic system inlet and exhaust passages provide pressure differential for an upper hydraulic thrust bearing and the drive fluid also flows through the mechanical bearings. In an open flushing fluid-drive system, the pressure differential across the flushing nozzle plus that across the motor is utilized and a confined lubricating fluid is pressurized, without mixing, by the flushing fluid. Seals for the hydraulic thrust means double as seals effecting connection between the rotary and stationary passages of the motor. In an embodiment having compound mechanical bearings a crushable element distributes load between the two bearings.

In a preferred embodiment a chamber communicating with the supply of flushing fluid is provided about the lower end of the motor, through which the drive shaft extends. The fluid in the chamber protects the end of the motor from cuttings and provides a means for supplying flushing fluid into the shaft. A disposable wear sleeve surrounding the stationary housing of the motor provides passages for downward supply of flushing fluid as well as protection of the motor from the upward flowing cuttings. A drill string comprises I-I shaped sections interlocked to withstand the torque and provide space for hydraulic lines.

Other features will be understood from the drawings and detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows apparatus according to the invention as it would be used in drilling a well.

FIG. 2 shows in elevation the downhole motor and portions of the apparatus of FIG. I with parts cut away to reveal interior structure! FIG. 3 shows a horizontal cross-section of the apparatus shown in FIG. 2 taken at the plane 3-3 indicated in FIG. 2.

FIG. 3a shows the profile of the rotor of the motor shown in FIG. 1.

FIG. 4 shows in vertical cross-section details of the upper bearings of the motor shown in FIG. 2.

FIG. 5 shows an alternative construction for the upper bearings of the motor shown in FIG. 2.

FIG. 5a is a perspective view of a crushable element of FIG. 5 and FIG. 5b is a stress-strain diagram related to that element.

FIG. 6 shows a perspective view of a portion of the apparatus at the top of the hole.

FIG. 7 shows a cross-section of the drill string extending through the hole.

FIG. 8 shows another embodiment wherein a single fluid serves as both a drive fluid and a flushing fluid.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring particularly to FIG. 1, drilling rig is drilling hole 12. Roller cone bit 14 at the bottom of the hole is rotatively driven by downhole motor assembly 16. Hydraulic supply hose 18, hydraulic return hose 20, and flushing fluid supply hose 22 are connected to the top of motor 16 and extend upward within channels in non-rotating drill string 23 to the top of the hole. The weight of the drill string as well as weight from the surface rig bears upon motor 16, while the reaction torque of the motor is transmitted through the non-rotational string to a restraint at the top of the hole. Referring to FIGS. 2 and 3, downhole motor assembly 16 includes a generally cylindrical housing with a central circular bore 52. Eight equally spaced vertical and radial slots 54 are cut the length of housing 50 and communicate their full length with central bore 52.

Vanes

60, 62, 64, 66, 68, 70, 72, and 74 slide radially within slots 54. Eight cavities 76 are bored the length of housing 50 along the outer edge of the slots. Several springs 80 are distributed along the length of each cavity 76, seating against the back of the cavity and pressing inwards the vane situated in the associated slot. Generally cylindrical elongated rotor 82 is situated within the bore 52 of housing 50. Rotor 82 has a cam-shaped cross-section, as shown particularly in FIG. 3a, with two

circular portions

84 and 86 concentric with the center of the rotor and of major diameter slightly less than the diameter of bore 52 and two

circular portions

90 and 92 concentric about the center of the rotor and of minor diameter less than the major diameter.

Major diameter portions

84 and 86 are positioned alternately with

minor diameter portions

90 and 92 around the periphery of rotor 82,

with outward sloping portions 96 and inward sloping portions 97 fairing smoothly between minor to major and major to minor circular portions, respectively when viewed clockwise.

Circular portions

84, 86, 90, 92 each extend circumferentially around the rotor surface somewhat more than the circumferential distance between adjacent vanes.

Vanes

60, 62, 64, 66, 68, 72, and 74 bear against rotor 82 throughout the length of the cam-shaped rotor portion. Supply duct 100 and exhaust duct 102 are bored longitudinally through rotor 82 on the diameter bisecting

circular portions

84 and 86. A series of transverse ducts 104 spaced along the rotor length communicate, between duct 100 and the periphery of rotor 82. Similarly, ducts 106 communicate between duct 102 and the periphery of rotor 82. Relieved portions 107 are provided in the surface of rotor 82, defining circumferentially elongated inlet and outlet ports having greater cross-section at the rotor periphery than the cross-section of

ducts

104 and 106. These relieved portions with torque and thrust transmitting metal lands 109 therebetween are in communication with

transverse ducts

104 and 106 and are situated around the rotor surface to extend circumferentially over the

sloped portions

96 and 97 with slight overlap onto adjacent circular portions. The crosssection of the rotor as shown in FIG. 3 is dimensioned so that the rotor can carry both the large torque and large thrust required to operate the roller bit. The placing of slots 54 in the housing enables the full diameter of the rotor to bear torque while the relatively larger diameter shell of the housing lying outward of the slots can readily bear the reaction torque and still conform to the diameter of conventional drill holes. The location of

ducts

100 and 102 on the diameter bisecting the major diameter

circular portions

84 and 86 of the rotor is helpful in assuring large torque-carrying capacity for the rotor while providing passages for the motive fluid.

Sleeve 110 is affixed around housing 50 and ribs 112 to provide a plurality of vertical channels 114. Flushing hose 22 communicates through passage 118 to plenum 116 at the top of assembly 16.- Channels 114 extend from plenum 116 to chamber 120 at the bottom. The output shaft portion 121 extends out of the motor housing, through seal 123, into chamber 120. Bit 14 connected to portion 121 has passages 122 so that chamber 120 communicates with flushing fluid outlet nozzles in the bit 14.

It will be noted that contrary to usual design practice, no thrust bearing is provided in the vicinity of the tool. bearing 139 being provided to take mainly radial loads for positioning the rotor and tool. Instead the thrust is transmitted through the entire length of rotor 82 (which may be 6 feet or longer) to a thrust assembly at the upper end of the motor.

The upper portion of motor assembly 16 is shown more particularly in FIG. 4. Rotor 82 necks down to cylindrical portion providing shoulder 132 with an upward directed thrust surface. Collar 134 fits around portion 130 and rests on rotor shoulder 132. A stationary shoulder extension 136 is attached to housing 50 and extends inward therefrom. Main thrust bearing 138 is situated between shoulder extension 136 and collar 134 to permit relative rotation therebetween. Radial bearing 140 fits between shoulder piece 136 and portion 130 of rotor 82. Upwards from bearing 140, rotor 82 again necks down to a circular section 142 providing an upward facing shoulder 144. Hydraulic pressure collar 146 fits around rotor portion 142 and rests on shoulder 144, to turn with the rotor. Upper collar 148 also fits around portion 142 and rests on the top of hydraulic collar 146 to turn with the rotor. Collar 148 is retained by nut 149 threaded onto the upper end 151 of rotor 82. Stationary piece with internal ledge is attached to stationary shoulder extension 136 and with shoulder extension 136 forms an extension of housing 50. Cap piece 153 encloses the top of rotor 82 forming supply plenum 152 between the end of the rotor and the cap. Duct 100 communicates (through the upper end of the rotor) with plenum 152 as does supply hose 18 through fitting 154. Duct 102 is plugged at its upper end with plug 156. Duct 102 communicates through radial passage 158 in rotor portion 142, circumferential slot 160 in collar 148, and passage 162 in collar 148, through circumferential plenum 164, and

passages

166 and 168 in piece 150 with exhaust hose 20. Duct 102 also communicates through radial passage 184 and circumferential slot 186 in rotor portion 142 and thence through radial slot 188 with the annular region 190 generally occupied by bearing 140.

Duct 100 communicates through radial passage 172 in rotor portion 1'42 with circumferential slot 174 and passage 176 in collar 146 with circumferential plenum 178. Duct 100 also communicates through passage 180 in rotor portion 130 with the annular space 182 generally occupied by thrust bearing 138. Seal 192 prevents major leakage of hydraulic fluid between plenum 178 and region 190.

Annular seals

194 and 196 seal the hydraulic fluid from major leakage from high pressure plenums 152 and 178 respectively into low pressure plenum 164 and at the same time provide for the ex' haust connection from passage 162 to passage 166.

In operation. hydraulic power source 34 at the top of the well delivers high pressure hydraulic actuating fluid to hose 18 through which it passes to the bottom of the drill hole and enters downhole assembly 16 through fitting 154. The high pressure hydraulic fluid is delivered through plenum 152 and the rotor 82. (through longitudinal duct 100. and transverse ducts 104, FIGS. 2 and 3) to vane-motor compartments between rotor 82 and housing 50. The high pressure hydraulic fluid flowing into this space acts upon the outward sloped rotor surfaces 96. Corresponding to the inward flow through passages 104 there is an outward flow of hydraulic fluid from the spaces exposed to inward sloping surface portions 97, the pressure drop from surfaces 96 to 97 producing a clockwise torque on the rotor. Exhaust fluid flows through passages 106, duct 102,

passages

158, 160, 162, plenum 164 and

passages

166 and 168 back to exhaust hose 20. The exhaust hydraulic fluid thereupon flows up through hose 20 to the top of the hole where it is delivered to the hydraulic power system for reuse.

In the instantaneous position of the rotor illustrated in FIG. 3,

vanes

62, 66, 70, and 74 are short-circuited by relieved portions 107 in the sloped surfaces 96 and 97 so that no pressure differential obtains across vanes when they are moving as they follow the sloping portions of the rotor surface. Vanes and 68 which are momentarily bearing on minor diameter circular portions 92 and and

vanes

64 and 72 which are momen' tarily bearing on major diameter

circular portions

86 and 84 seal against rotor 82 and sustain the operating pressure of the hydraulic motor. Thus the vanes which sustain a pressure differential bear on circular portions of the rotor and need not move radially while the vanes which bear on the sloping

portions

96 and 97 and must move radially as the rotor turns sustain no pressure differential in the circumferential direction, and therefor are not greatly subject to wear. Vane pairs 68 and 72 and

pair

60 and 64 together with the surface of rotor 82 and the bore of housing 50 momentarily form compartments on opposite sides of the rotor communicating through a passage 104 with inlet duct 100. Vane pairs 64 and 68 and

pair

72 and 60 together with the rotor surface and the housing bore form compartments on opposite sides of the rotor communicating through passage 106 with outlet duct 102. As the rotor turns (clockwise as illustrated in FIG. 3) the roles of the vanes and the communications with the

passages

104, 106 are successively shifted around the axis.

In addition to supplying the driving power to rotate the rotor through the main hydraulic path as just described, the hydraulic fluid is used to provide downward thrust on the bit (FIG. 4) to relieve the loading on the mechanical thrust bearing 138. This is done by means located also at the upper end of the rotor of exposing upwardly directed surfaces (147, 147a, 147b," 179; 189) of the rotor 'to high (supply) pressure and corresponding downwardly directed surfaces (the bit 14; 161; 177) of the rotor to low pressure. In the case of surface 189 the high pressure hydraulic fluid from duct passes through radial passage 180 to the space 182 around bearing 138. The high pressure hydraulic fluid in this space exerts a downward force on the up ward facing surface 189 of collar 134 and a corresponding upward force on the downward face of shoulder extension 136 thereby transmitting thrust from shoulder extension 136 to collar 134 and through that to rotor 82. Hydraulic fluid leaks up in passage 137 between the shoulder extension 136 and rotor portion to the space 190 around radial bearing 140 losing pressure as it does so from friction in the narrow passage. The space 190 communicates through passage 184 with the low pressure exhaust duct 102 where the hydraulic fluid is at low pressure. The hydraulic fluid at exhaust pressure therefor exerts small forces on the up ward facing surface of shoulder extension 136 and downward facing surface 177 of pressure collar 146 which are in communication with space 190. In a simi' lar manner high pressure hydraulic fluid from duct 100 communicates through passage 172, annular passage 174 and passage 176 with plenum 178. The high pressure fluid in plenum 178 provides a downward force on the upward facing surface 179 of pressure collar 146 which is communicated across shoulder 144 to thrust rotor 82 downwards. The reactive upward force is delivered against a downward facing; surface of ledge 170 affixed to the cap piece of the housing 50. The low pressure exhaust fluid which passes through plenum 164- exerts a small upward force on the downward facing portion of collar 148 while the larger pressure of the supply hydraulic fluid in plenum 152 exerts a large downward force on surfaces 147, 147a, and 14712 of the rotor members to further augment the downward thrust. The reaction thrust from housing 150 is transmitted upward through the drill string to the top of the hole.

During the drilling operation flushing fluid, which may be air or water or prepared mud. is delivered by the flushing fluid supply to hose 22 and thence to the downhole assembly 16 where it flows through passage 118 and down the outside of assembly 16 through channels 114, then through chamber 120 and passages 122 to the center of bit 14. The flushing fluid then flows out through the bit where it entrains rock chips and then flows upwards past the downhole assembly 16 through the space between the sleeve 110 and hole 12 then upwards through spaces in drill string 23 to the surface where it is discarded along with the chips or processed for reuse. The supply flushing fluid (e.g.. compressed air) in the chamber 120, at pressure higher than at the bit protects the end of the motor, especially seal 123, from the abrasive cuttings. extending the life of the seal. The wear sleeve 110 (which is removable and replaceable when worn out) protects the exterior of the motor housing from the upward flow of abrasive cuttings.

Radial bearing 140 maintains the centering of the rotor 82 in its housing 50 while permitting rotation and also acts as a reverse thrust bearing to prevent the rotor from dropping out of housing 50* when the rig is suspended off the bottom of the hole. As the hole is drilled deeper, the required torque for turning the bit is transmitted from an anchor block 38 (FIG. 1) firmly fixed to the ground at the top of the hole, through successive lengths 24 of drill string 23 to housing 50 of downhole assembly 16. This torque is applied to the moving rotor through the cam shaped portion of the rotor, and the rotor transmits the torque to the bit at the cutting surface. The thrust for driving the hole is transmitted by a ram 40 to the drill string 23 and thence to the housing 50 of the downhole assembly 16. The thrust is transferred from the stationary housing portion 50 to the rotor by means of the thrust bearing 138 and the hydraulic thrust surfaces.

An important feature of the described embodiment is that the thrust is applied to the rotor at a level above that at which the torque is applied to the rotor. This permits deeper shoulders on the rotor at the points where the thrust is applied since at the level the thrust is applied the core section of the rotor need not have the strength to carry any torque and can therefore be of diminished section. The larger shoulders thus obtained are particularly advantageous in permitting a larger thrust bearing 138 with increased strength and operating life. (similarly, in regions where torque is applied there is no need of comprimise in design to provide room for the thrust bearing).

The use of the hydraulic pressure collars to deliver thrust to the rotor has the important advantage that it reduces the load on the main thrust bearing and thereby contributes to a greater bearing life and has the further advantage that it to a large degree provides automatic adjustment of the bit thrust to the bit torque. This adjustment occurs because when the bit is cutting into hard rock it requires a greater torque. This implies a larger pressure differential between the hydraulic supply and exhaust with corresponding larger thrust force delivered across the pressure collars. The assembly 16 therefore automatically delivers a greater thrust when it is needed for drilling through harder rock.

The seals as described have a double function in both providing the seal between rotary and stationary parts and also in defining the hydraulic thrust system. Equally the hydraulic fluid of the thrust system gradually flows through the bearings (see e.g., passages 180, 137, 184) thus providing cleaning, and with appropriate design, even cooling.

In a typical construction of the embodiment just described, the bit is 8 inches in diameter and the motor is sized smaller than 8 inches to permit escape of the flushing fluid past its exterior. The torque-carrying portion of the rotor is approximately 6 feet long, the difference in radius between major and minor circular arcs of the rotor is A; inch and the hydraulic system provides a throughput of approximately 250 gallons per minute, with pressure ranging up to 2,000 psi, to drive the rotor at speeds between 100 and l50 rpm with power delivered to the bit ranging up to 290 horse power, the thrust applied to the rotor is approximately 60,000 pounds under drilling load, with severe shock loading of which significantly more than half can be borne by the hydraulic system, and the remainder by the mechanical thrust bearing, the latter ensuring proper positioning of the rotor and bit during operation.

As shown particularly in FIG. 6 and 7 drill string 23 is made up offitted lengths 24 with H-shaped cross sections. Key plates 26 attached to the bottom of each length slide over the length immediately below to form a torque transmitting joint 28. A similarly constructed joint connects the bottom length 24 to assembly 16.

Hoses

18, and 22 are secured within the channels of drill string lengths 24 by keepers 30. Hoist cable 32 is connected to the downhole motor assmbly l6 and also passes up through a channel in drill string 23. At the top of the hole, hydraulic supply equipment 34 is connected to

hydraulic hoses

18 and 20 and flushing fluid supply equipment 36 is connected to flushing hose 22. At the top of the hole drill string 23 passes through anchor block 38 which prevents it from rotating. Ram 40 engages the top of the uppermost length 24 of drill string 23 to apply downward force on the drill string. Delivery pulleys 42 deliver hoses I8, 20 and 22 to the channels of the drill string 23 from supply coils 44. Cable 32 is wound onto the drum of hoist 33.

As the hole is drilled deeper into the ground, the whole drill string 23 descends into the hole driven by ram 40 with

hoses

18, 20, and 22 being payed out through pulleys 42. Eventually it becomes necessary to add an additional length 24 to string 23. This may be done by withdrawing ram 40 and engaging the additional length to the end of the string and resuming the ram drive on the augmented string. It may be noted that the addition of the length requires no disturbance of the hose connections and no threading of the new length onto the string to make a hydraulic joint. so that the addition can be effected very quickly.

Assembly 16 is hoisted to the surface when necessary by drawing up cable 32 by winch 33 while removing successive lengths of the drill string. During the hoisting operation, the hoses remain intact and are withdrawn and coiled so that the hoisting can be continued without interruption.

FIG. 5 shows an alternative embodiment for the upper end of the motor assembly wherein rotor housing 50 is attached to first shoulder extension 200 which in turn is connected to second shoulder extension 202 which in turn is connected to piece 204 and cap 205. extending over rotor 82a and having

fittings

206 and 208 for connection with hydraulic power hoses l8 and 20, respectively. Thrust bearing 210 carries thrust be tween downward facing surface 212 of extension 200 and upward facing surface 214 of rotor collar 216. Second thrust bearing 218 similarly carries thrust between downward facing surface 220 of housing extension 202 and upward facing surface 222 of rotor collar 224, collar 224 being fitted around necked down portion 226 of rotor 82a. Crushable spacer 230 fits around rotor portion 226 between collar 224 and collar 216. This embodiment includes duct work for conducting hydraulic fluid to motor and radial bearing essentially the same as in the embodiment previously described. In the initial assembly of the alternative embodiment, crushable collar 230 is tall enough so that thrust applied from the drill string is transmitted across bearing 218 to collar 224 then through the crushable collar to collar 216, with extension 200 and bearing 210 carrying little if any load. As the thrust load is increased, however. crushable collar 230 reaches its stress-strain yield point A, FIG. 5b, and inelastically deforms while the housing 50 with

extensions

200, 202 and 204 settle slightly downwards around rotor 82a. This inelastic crushing continues until the thrust load is appropriately shared between

bearings

210 and 218, and bearing surface 212 establishes the final reference height so that the rotor is FIGS. positioned when subjected to working load. The use of the crushable collar provides an automatic adjustment of the column length for equitable sharing of the load between the two thrust bearings which could otherwise be accomplished only by very exacting tolerances in the structure parts, and thus makes possible the use of compound mechanical bearings within the tight confines of well holes.

FIG. 8 shows an embodiment in which a single fluid, i.e., hydraulic drilling mud, is used for flushing, rotationally driving the downhole motor 250 and providing axial thrusts on the rotor. Rotor 252 has a central portion 254 with a cam shaped cross section similar to that of rotor 82 described above. Vanes 256 and housing 258 are disposed around the rotor in a manner similar to that described above. Thrust bearing 260, centering

bearings

262 and 264, and collar 266 have structure and function similar to analogous parts of motor 16. Rotor 252 has inlet channel 270 centrally bored through its upper portion which communicates with inlet plenum 276 and through passages 272 with inlet ports 274 confined to the upper portion of cam shaped portion 254. Discharge channel 278 is centrally bored through the lower portion of rotor 252 and communicates through passages 280 with discharge ports 282. At its lower end channel 278 communicates with flushing fluid outlet 284 (FIG. 2) in bit 14 adapted to discharge fluid against work area 286.

Protruding thrust collars

290, 292, and 294 fit around the upper portion of rotor 252 with inwardly protruding housing extensions 297 and 299 interspersed therebetween. Thrust chambers 306 are defined between upwardly directed surfaces 308 of the rotor thrust collars and downwardly directed surfaces 310 of the stationary housing extensions. Similarly, lower pressure chambers 296 are defined between downwardly directed surfaces 298 of the thrust collars and upwardly directed surfaces 300 of the housing extensions. Seals 316 isolate thrust chambers 306 and low pressure chambers 296 from one another while the chambers communicate respectively through

passages

312 and 314 with inlet channel 270 at inlet pressure and through passage 302 and bleed port 304 with the space exterior of the housing at discharge pressure.

Lubricating cylinder 320 is provided in the top of the housing 258. A rolling diaphram 322 is contained therein and sealed to the cylinder walls by a retainer 326, dividing the cylinder into two chambers. The flushing fluid side chamber 324 communicates through hole 335 to the inlet flushing fluid or mud pressure from bore 277. The opposite chamber 328 is filled with lubricant. Chamber 328 is sealed by cap 330. By this means lubricant at inlet flushing fluid pressure from chamber 328 feeds through oil line 336, channel 332, and passage 334 to hearing 262 and then through a leakage along the rotor to bearing 260. If desired, lubricant pressure exceeding inlet pressure can be produced by a spring 337 acting against the top (flushing fluid side) of the diaphram 322.

In the operation of the embodiment shown in FIG. 8, pressurized flushing fluid is supplied from a pump at the top of the hole through hose 277 to entrance plenum 276. This fluid then flows from plenum 276 through channel 270 and into the motor chambers between vanes 256 where it provides the forces to rotate the rotor 252. The fluid is discharged (now at a reduced pressure corresponding to the work done in turning the rotor) from the chambers through passages 280 leading to channel 278. From channel 278 the fluid flows into the bit where it is directed through an outlet with substantial pressure drop and increased velocity against the working face to remove chips as they are cut. The fluid, now carrying the chips in suspension, then passes up through the space between the housing 258 and the hole wall past the motor 250 and then continues up the hole to the top. Chambers 306 are maintained at the pressure of the inlet fluid by communication with channel 270 through passages 312 while chambers 296 are maintained at the pressure ofthe discharge fluid by communication with the motor periphery through passages 302. thus providing several stages of fluid-generated thrust on the rotor and thereby on the bit. The inlet pressure of the flushing fluid is applied to the top of the diaphram 322 to pressurize lubricant in reservoir 328. This lubricant is thus supplied at high pressure to

bearings

262 and 260 to lubricate them while keeping them free from contact with abrasives which are frequently present in the flushing fluid.

I claim:

ll. A downhole drill assembly capable ofdriving roller bits and the like, said assembly comprising in combination a stationary elongated housing of outer diameter sized for insertion into a drill hole and having an inner bore, a plurality of axially elongated sliding vanes disposed in and extending inwardly from axially elongated slots in the bore of said stationary housing. a rotor having a corresponding elongated cam-shaped rotor portion disposed within said housing and resiliently engaged by said vanes to form axially elongated compartments, inlet and exhaust passages for actuating fluid extending through said rotor and communicating with successive compartments as said rotor turns. said passages sized and located such that the rotor has a metal cross-sectional area effective to transmit both the torque and thrust associated with driving drill bits, and thrust bearing means located above said cam-shaped rotor portion, positioned to transmit thrust between said housing and said bit through the structure of said rotor portion, said thrust bearing means including a mechanical thrust bearing for positioning said rotor axially, an upwardly directed thrust surface associated with said rotor and means for applying actuating fluid at pressure generally corresponding to pressure in said inlet passage axially downward against said thrust surface to transmit downward thrust from upper supporting elements to said rotor and therethrough to said drilling bit.

2. The downhole drill assembly of claim 1 wherein said rotor portion has an internal, axially extending passage for fluid and communicating therewith a plurality of axially aligned discrete ports opening to the periphcry of said rotor portion, said ports being spaced from one another along the axial length of the rotor portion and load bearing metal lands therebetween.

3. The downhole drill assembly of claim 2 wherein said ports are circumferentially elongated at the periphery of said rotor portion, and lateral passages extending from said ports to the axially extending passage have flow cross sections smaller than said ports at said periphery.

4. The downhole drill assembly of claim 2 wherein the periphery of said rotor portion has circumferential circular portions of major diameter connected by sloped portions with circular portions of minor diameter, said circular portions centered on the rotor axis of rotation, the circumferential spacing of said vane dividers being uniform, the circumferential length of said portions of major and minor diameters being greater than the circumferential spacing between vanes, each said port being sufficiently long in the circumferential dimension to effectively communicate with both circumferential ends of one of said sloped portions, while slightly overlapping a circular portion at each end.

5. The downhole drill assembly of claim 2 wherein said rotor portion is an integral structure defining the thrust and torque transmitting metal cross-section throughout the length of said compartment. and having a torque and thrust transmitting output means at its lower end.

6. The downhole drill assembly of claim 1 wherein said rotor has internal. elongated, axially extending passages for both inlet and exhaust of actuating fluid.

7. The downhole drill assembly of claim 6 wherein said passages extend parallel to each other along the length of said compartments, a hydraulic supply conduit for pressurized driving fluid connected to the upper end of said inlet passage. a hydraulic exhaust conduit connected to the upper end of said axial exhaust passage, both of said conduits adapted to communicate upwardly through said hole.

8. The downhole drill assembly of claim 1 wherein a supply pressure plenum is defined about the upper end of said rotor between the housing, and said rotor and said thrust surface comprises an upwardly directed end surface of said rotor.

9. The downhole drill assembly of claim 8 wherein said rotor has a reduced portion below said end surface of smaller diameter than said end surface and a thrust collar mounted on said rotor below said reduced diameter portion, means exposing the upper surface of said thrust collar to supply pressure and means exposing the downwardly directed surface of said thrust collar and the downwardly directed surface of said rotor above said reduced diameter portion to exhaust pressure.

10. The downhole drill assembly of claim 9 wherein said mechanical thrust bearing is disposed between a lower shoulder of said rotor and an upper shoulder of said housing. said lower shoulder defining an upwardly directed surface exposed to pressure generally corresponding to pressure in said inlet passage.

11. The downhole drill assembly of claim 1 including stationary inlet and exhaust conduits for communicating from above with said inlet and exhaust passages through said rotor. said passages and conduits cooperating to define a hydraulic loop. said means for applying actuating fluid downward against said thrust surface including means introducing inlet pressure to said upwardly directed thrust surface. and means for venting a cooperating downwardly directed surface associated with said rotor to exhaust pressure of said hydraulic loop.

12. The downhole drill assembly of claim 11 wherein said rotor has an upward extension beyond said vane motor compartments, said extension carrying said thrust means and having internal supply and exhaust passages, and a sealing means effectively sealing the thrust means from loss of hydraulic fluid and simultaneously effecting the fluid connection between said passages in the rotor and corresponding stationary passages.

Claims

1. A downhole drill assembly capable of driving roller bits and the like, said assembly comprising in combination a stationary elongated housing of outer diameter sized for insertion into a drill hole and having an inner bore, a plurality of axially elongated sliding vanes disposed in and extending inwardly from axially elongated slots in the bore of said stationary housing, a rotor having a corresponding elongated cam-shaped rotor portion disposed within said housing and resiliently engaged by said vanes to form axially elongated compartments, inlet and exhaust passages for actuating fluid extending through said rotor and communicating with successive compartments as said rotor turns, said passages sized and located such that the rotor has a metal cross-sectional area effective to transmit both the torque and thrust associated with driving drill bits, and thrust bearing means located above said cam-shaped rotor portion, positioned to transmit thrust between said housing and said bit through the structure of said rotor portion, said thrust bearing means including a mechanical thrust bearing for positioning said rotor axially, an upwardly directed thrust surface associated with said rotor and means for applying actuating fluid at pressure generally corresponding to pressure in said inlet passage axially downward against said thrust surface to transmit downward thrust from upper supporting elements to said rotor and therethrough to said drilling bit.

2. The downhole drill assembly of claim 1 wherein said rotor portion has an internal, axially extending passage for fluid and communicating therewith a plurality of axially aligned discrete ports opening to the periphery of said rotor portion, said ports being spaced from one another along the axial length of the rotor portion and load bearing metal lands therebetween.

5. The downhole drill assembly of claim 2 wherein said rotor portion is an integral structure defining the thrust and torque transmitting metal cross-section throughout the length of said compartment, and having a torque and thrust transmitting output means at its lower end.

6. The downhole drill assembly of claim 1 wherein said rotor has internal, elongated, axially extending passages for both inlet and exhaust of actuating fluid.

7. The downhole drill assembly of claim 6 wherein said passages extend parallel to each other along the length of said compartments, a hydraulic supply conduit for pressurized driving fluid connected to the upper end of said inlet passage, a hydraulic exhaust conduit connected to the upper end of said axial exhaust passage, both of said conduits adapted to communicate upwardly through said hole.

10. The downhole drill assembly of claim 9 wherein said mechanical thrust bearing is disposed between a lower shoulder of said rotor and an upper shoulder of said housing, said lower shoulder defining an upwardly directed surface exposed to pressure generally corresponding to pressure in said inlet passage.

11. The downhole drill assembly of claim 1 including stationary inlet and exhaust conduits for communicating from above with said inlet and exhaust passages through said rotor, said passages and conduits cooperating to define a hydraulic loop, said means for applying actuating fluid downward against said thrust surface including means introducing inlet pressure to said upwardly directed thrust surface, and means for venting a cooperating downwardly directed surface associated with said rotor to exhaust pressure of said hydraulic loop.