CA1095020A - Down hole well drilling tool - Google Patents

Abstract

ABSTRACT
A down hole well drilling tool, e.g., a turbodrill, which is connected to a string of drill pipe as a rotating shaft for driving a drill bit which may be a rotary bit or a high speed solid head diamond bit. The turbine section has rotor and stator blades which are crescent-shaped in cross section. The bearing shaft is provided with chevron rotary seals positioned below the rotary bearings carrying both radial and vertical thrust. Fluid lubricant fills the space from the rotary seals to a predetermined level above the bearings. A piston seals the lubricant chamber and is pressurized by drilling fluid (i.e., mud) flowing through the tool. A layer of lubricant fluid over-lies the first piston and has a second piston covering said fluid and transmitting pressure from the drilling fluid to the lubri-cant fluid surrounding the bearings. Means is provided to give an indication, at the well surface, of loss of lubricant in the turbodrill. Means is provided to cause the vertical thrust to be carried on the bottom vertical thrust bearings, after the top vertical thrust bearings are worn, and thus extend the drilling life substantially. Another optional feature provides for bal-ancing the pressure across the bearing seals. This is accom-plished in one form of the invention by providing pump means operated by the drilling motor to pump drilling mud away from the bearing seals. In another form of the invention, the flow of drilling fluid is divided into two streams, one of which rotates the drill bit, and the other of which passes through the drill bit. The pressure drop across the drilling motor equals the pressure drop across the drill bit, thus balancing the pressure on the bearing seals.

Description

10~0~.0 DOWN HOLE WELL DRILLING TOOL

This invention relates to down hole drilling motors, such as turbodr~lls and drills operated by positive displacement motors, and to certain improved features therein.

FIELD OF THE INVENTION
Down hole drilling motors were first invented 100 years ago. Down hole drilling motors were first extensively tested in the 1920's. They did not find sidespread use until the 1950's when burbodrills began to be used in the Soviet Union.
By the early 1960's, it is estimated that 85% of the wells in the Soviet Union were being drilled with turbodrills. Down hole drilling motors have found widespread use in the United States for drilling directional holes, but they are not widely used for straight hole drilling because of bearing and seal problems. Commercial down hole drilling motors operate at speeds ranging from 300 to 1,000 rpm whereas roller bits oper-ate most effectively at speeds of 50 to 150 rpm. At high motor speeds, roller bearings fail after periods of about 5 to 15 hours whereas with conventional drilling equipment operating at lower speeds the bearings of roller bits last up to 200 hours.
Down hole motors have had substantial problems in design of radial and vertical thrust bearings, lubrication systems, tur-bine efficiency, housing construction, etc., which have limited substantially the acceptability of down hole motors in petroleum drilling and in other applications.

BRIEF DESCRIPTION OF THE PRIGR ART
Down hole drilling motors were patented soon after the advent of rotary drilling rigs in the 1860's. Cross U.S. Patent ~o~so%o 292,888 dlscloses a single stage axial flow turbodrill which is similar in some respects to modern turbodrills. Scharpenberg .S. Patent 1,482,702 discloses one of the earliest multi-stage turbodrills which was the forerunner of turbodrills currently in use. The Scharpenberg turbodrill contained a lubrication system which allowed the thrust bearing to operate in oil or grease. Drilling fluid acting on a floating piston pressurized the lubricant in the system. The bearings in modern turbodrills operate directly in the abrasive drilling mud, resulting in rapid failures, which limit the application of these drills.
Capeliuschnicoff U.S. Patent 1,681,094 discloses a single staged geared turbodrill. These turbodrills were tested exten-sively in the Soviet Union from 1924 to 1934. The Russians had severe problems with the speed reducers Capeliuschnicoff turbodrill and subsequently changed to the Scharpenberg turbo-drill. Several Russian engineers perfected multistage turbo-drills during the 1940's and 1950's, and by the early 1960's the Russians were drilling 80 to 90~ of their wells with axial flow turbodrills. The Russians licensed turbodrill technology to companies in the United States, France, Germany and Austria.
Turbodrills have had a rather limited commercial acceptance and are used primarily in directional wells.
Virtually all down hole drilling motors have four basic components:
1. Motor section

2. Vertical thrust bearings

3. Radial bearings

4. Rotary seal The bearings and seals can be placed in a separate package or unit at the motor section and thus can be used on any type Or motor (i.e., turbodrills, positive displacement motors, etc.) There are two basic types of down hole drilling motors:
1. Turbodrills 2. Positive displacement Turbodrills utilize the momentum change of drilling fluid (i.e., mud) passing through the curved burbine blades to provide torque to turn the bit. Diamond bits are used on most turbo-drills because these motors turn at speeds of 600 to 1,000 rpm whereas roller-type rock bits operate effectively only at speeds up to about 150 rpm. Positive displacement motors have fixed volumetric displacement and their speed is directly proportional to the flow rate. There are three basic types of positive dis-placement motors in use or currently under development:
1. Moineau motor 2. Flexing vane motor 3. Sliding vane motor These motors have large volumetric displacement and there-fore deliver hlgher torques at lower speeds.
Thrust bearing failures in down hole motors is a problem -because of high dynamic loads produced by the action of the bits and by drill string vibrations. One major oil company placed a recorder at the hole bottom and found that dynamic loads were often 50~ higher than the applied bit weight. It was found on occasion that the bit bounced off bottom and produced loads in excess of 120,000 pounds when drilling at an applied bit weight of 40,000 pounds. These high loads can cause rapid failure of the thrust bearings; consequently these bearings must be greatly overdesigned to operate in the hostile down hole environment.

Two types of bearings have been used in down hole drilling motors:
1. Rubber friction bearings 2. Ball or roller bearings In existing motors, these bearings operate directly in the abrasive drilling mud and usually wear out in 20 to 100 hours.
In addition, the rubber friction bearings have high friction and therefore absorb 30 to 40% of the output torque of the turbodrills. The lift of the vertical thrust bearings can be increased by operating at bit weights which nearly balance the hydraulic down thrust thereby removing most of the load from these bearings.
Radial bearings are required on each side of drilling motors and on each side of the vertical thrust bearings. These radial bearings are usually subJected to lower loads than the thrust bearings and therefore have much longer life. Two basic types of radial bearings are used in down hole motors:
1. Marine bearings 2. Roller or ball bearings Most motors contain marine bearings made of brass, rubber or similar bearing materials. The marine bearings are cooled by circulated mud through them.
Rotary seals are currently the weakest link in down hole motor design. Improved seals would allow the bearings to be sealed in lubricant, thereby increasing their life substantially.
Improved seals would allow bits to be operated at higher pres-sures thereby greatly increasing drilling rate.
There are six basic types of seals that have been tested in down hole motors: -10~0~0 1. Packin~ scals 2. F~ce seals 3. L~byrlntll scals 4. Radial lip seals

5. Constrictions (friction bearlngs and marine bearings)

6. Flo~ metering seals Existing drlllin~ motors allow drilllng mud to continuously leak through the rotary seals by constricting the flow with any of a variety Or seals permitting leaka~e. Sand and otl~er ~brasive particles are filtered out of the mud in the rotary seals which results in rapid failure of the seals. Any substan-tial i~nprovement in turbodrill design will require positive se~ls tYhich allo~ no appreciable leaha~e.
The present invention is such an improvemert in that ~
contemplates a downhole well drilling tool that is adapted for connection at one end to the lower end of a drill string and at the other end to a drill bit to be driven thereby. The drill-ing tool comprises tubular housing means and rotary shaft means supported therein and extending therefrom and adapted to support a drill bit, motor means in the housing means actuated by flow of drilling fluid therethrough and operable to rotate the shaft - means, and bearing means in the housing means comprising a plurality of bearing members spaced longitudinally of and support-ing the rotary shaft means against radial and longitudinal thrust loads. Lubricant fluid fills the space between the housing means and the shaft means around the bearing means and for a pre-determined distance above the uppermost of the bearing members, and piston means seal the space between the shaft means and the housing means above~the lubricant fluid and movable longitudin-ally of the housing means. The piston means is operable by ~ -5-10~020 pressure of drilling fluid to maintain the lubricant fluid uncler pressure to lubricate the bearing means, rotary sealing means is positioned above and spaced from the piston means to prevent contact of drilling fluid therewith, and hydraulic means applies pressure from drilling fluid above the sealing means to the piston means.
In one aspect the invention contemplates a downhole well drilling tool which comprises housiny means adapted to bc conllc~ed to a drill string, a rotary shaft in the housing means and extending downward therefrom and adapted to support a drill bit, and means to rotate the shaft. Upper and lower thrust bearings are positioned around the shaft within the housing means to support the shaft against oppositely directed vertically extending forces, with the upper thrust bearings supporting the shaft against upward thrust during drilling operation, and with lower thrust bearings support-ing downward thrust of the shaft when lifted out of drilling operation. Means operable to shift the relationship of the lower thrust bearings and the shaft cause the shaft to be supported on the lower thrust bearings during drilling operation.
BRIEF DESCRIPTION OF THE DRAWINGS
_ Fig. lA is a view of the uppermost portion of a turbodrill partly in elevation and partly in vertical section, and further broken vertically to reduce the length of the turbine section;
Fig. lB is a view partly in elevation and partly in vertical section of the next successive lower portion of the turbodrill and illustrating an improved turbine seal, Fig. 1~ is a view of the next lower portion of the turbodrill partly in elevation and partly in section and illustrating an im-proved seal and an improved bearing arrangement therein;

Fig. lD is a view of the turbodrill partly in elevation and partly in vertical section showing the bottommost portion of the drill including the connection from the drill motor to the drill bit;
Fig. lE is a view partly in elevation and partly in vertical -5a-section of the portion of the turbodrill shown in Fig. lB illu-strating an improved turblne seal and pressure balancing pump;
Fig. lF is a modified view of the portion of the turbodrill shown in Fig. lE, showing an alternative pressure balancing pump.
Fig. 2 is an enlarged view, in vertical section of the one of the turbine rotor rings, showing the turbine blade in eleva-tion;
Fig. 2A is a plan view of the turbine rotor viewed from the line 2A - 2A;
Fig. 3 is an enlarged view, in vertical setion, illustrating one of the turbine stator rings;
Fig. 3A is a plan view seen from the line 3A - 3A of the ^--stator ring shown in Fig. 3;
Fig. 4 is a view in end elevation of one of the stator or rotor blades;
Fig. 5 is a view in elevation, and partially broken section, of a sub-assembly of a turbine stator and rotor;
Fig. 6 is a sectional view taken on the line 6 - 6 of Fig.
lB illustrating a locking ring preventing separation of threaded connected portions of the turbodrill housing;
Fig. 6A is an enlarged detailed sectional view of one of the locking rings illustrated in Fig. 6;
Fig. 6B is an enlarged sectional view of another embodiment of locking ring similar to that illustrated in Fig. 6A;
Fig. 7 is a view partially in section, as in Fig. 6, but including a ring-shaped mechanism for release of the locking ring;
Fig. 7A is an enlarged detailed sectional view showing the relationship of the release mechanism to the locking ring of 6A;
Fig 7B is an enlarged detail sectional view showing the rela-tionship of the release mechansim to the locking ring of Fig. 6B;
Fig. 8 is an enlarged view in vertical section of the middle 10~20 pOrtiOIl of Fig. 1/'\ illustratin.r an Oi-t;iOllal f`e;lt~Ul'e fOl' ~ Vid-ing a flow restriction operable to reverse the loading on the thrust bearings of` the turbodrill, appearing with Figs. 4 and 5;
Fig. 9 is an enlarged detail sectional view, taken in verti-cal section, of the middle portion of Fig. lC, illustrating an optional feature providing for indication of loss of lubrication in the turbodrill;
Fig. lOA is a view of the uppermost portion of a turbodrill, partly in elevation and partly in vertical section and further broken vertically to reduce the length of the turbine section and illustrating one embodiment of an arrangement to provide a balanced pressure across the bearing seals;
Fig. lOB is a view partly in elevation and partly in verti-cal section of the next successive lower portion of the turbodrill and illustrating an improved turbine seal' Fig. lOC is a view of the next lower portion of the turbo-drill partly in elevation and partly in section and illustrating an improved seal and an improved bearing arrangement therein;
Fig. lOD is a view of the turbodrill partly in elevation and partly in vertical section showing the bottommost portion of the drill including the connection from the drill motor to the drill bit;
Fig. llA is a view of the uppermost portion of a modified turbodrill, partly in elevation and partly in vertical section and further broken vertically to reduce the length of the turbine section and illustrating another embodiment of an arrangement to provide a balanced pressure drop across the bearing seals;
Fig. llB is a view partly in elevation and partly in verti-cal section of the next successiv~ lower portion of the modi-fied turbodrill and illustrating an improved turbine seal;
Fig. llC is a view of the next lower portion of the modified 10~0~0 turbodrill partly in elevation and part:ly in section and illu-strating an improved seal and an improved bearing arrangement therein;
Fig. llD is a view of the modified turbodrill partly in ele-vation and partly in vertical section showing the bottommost portion of the drill including the connection from the drill motor to the drill bit;

DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to the drawings by numerals of reference and more particularly to Figs. lA to lD, inclusive, there i3 shown a turbo-drill which is generally designated 10. Turbodrill 10 is very long in relation to its width and requires Figs. lA, lB, lC and lD to show its entire structure even though a substantial portion of the turbine section is omitted in Fig. lA. A typical turbo-drill of this design which is 7 3/4 inches in diameter is about 20.5 feet long. The turbine section represents almost half the length of the turbodrill and it is therefore necessary to omit a large portion of the multi-stage turbine.
At the upper end of turbodrill 10 there is provided a stator housing sub 11 having a threaded box end portion 12 forming a threaded conneciton 13 with the lower end of a drill string 14.
Stator housing sub 11 has an internal longitudinal passage 15 communicating with the open end of drill string 14.
Stator housing sub 11 has a threaded pin potion 16 which is threadedly connected as at 17 in the box end porticn 18 of the stator housing lg. Stator housing box portion 18 has an inter-nal annular grGove 20 therein which mates, when assembled, with an annular groove 21 in the pin portion 16 of stator housing sub 11. A lock ring 22 extends peripherally around the turbo-3 drill in the annular space provided by matching grooves 20 and lO~CiOZO

21 and abuts the walls of said grooves to prevent disassembly ofsaid stator housing from said stator housing sub accidentally.
Stator housing box portion 18 is also provided with a plurality of holes 23 uniformly spaced to provide points for application of pressure to lock ring 22 to permit separation of stator hous-ing 19 from stator housing sub 11. Details of this feature of construction are shown in Figs. 6 and 7, to be described more fully hereinafter. Threaded connection 17 is sealed against leakage by "0" ring 24 positioned in groove 25.
The turbine section of the turbodrill is positioned in the stator housing 19 just below the threaded joint 17 connecting to the stator housing sub 11. The stator portion of the turgbine consists of a plurality of stator members 26 which are shown in more detail in Figs. 3, 3A, 4 and 5. The stator members 26 are annular in shape and provided with vanes or blades 27 which will be described more fully in connection with the detailed drawings of these parts. Stator members 26 have an exterior surface pro-viding a sliding fit in the inner surface of stator housing 19.
Stator members 26 are positioned as a stack of abutting members extending longitudinally within the stator housing 19. In a typical turbodrill having a 7 3/4 inch diameter, there are 50 of the stator members and 50 of the matching rotor members. The stator members are preferably made of a hard beryllium copper alloy which is wear-resistant and whlch has a slightly higher coefficient of expansion than the steel of stator housing 19.
The stack of stator members 26 is maintained under compression in the stator housi3lg 19 with the result that the members are expanded to fit tightly against the inner surface of stator hous-ing 19 and resist slippa~e there~. Also, because of the higher thermal coefficient of expansion, the stator members 26 tend to expand more at the high temperatures encountered in use of the _9_ ~095020 turbodrill with the result that the increase in temperature encountered during operation causes stator members 26 to flt more tightly within stator housing 19 and effectively prevents slip-page therein.
At the upper end of stator housing 19~ there is positioned an annular stator spacer 28 which positions the uppermost stator member 26 relative to the end of stator housing sub 11. At the lower end of stator housing 19 there is a box portion 29 which is internally threaded and receives tubular stator makeup sleeve 30 in a threaded joint 31. The lower end of sleeve 30 is notched as indicated at 32 to receive a wrench for tightening sleeve 30 in threaded joint 31. When stator makeup sleeve 30 is tightened to the positioned shown, the upper end thereof abuts the lower-most stator member 26 and compresses the entire stack of stator members against each other and gainst annular stator spacer mem-ber 28. Stator makeup sleeve 30 when fully tightened maintains the stack of stator members 26 under sufficient compression to press them tightly against the inner surface of stator housing 19 and prevents slippage of the stator members during operation as described above. The lower box end 29 of stator housing 19 is connected in a threaded ~oint 33 to the threaded upper pin end 34 of bearing pack housing 35. Just below threaded joint 33, there is provided annular groove 21a in bearing pack housing 35 and annular groove 20a in stator housing 19 and a spring lock ring 22a positioned therein to prevent separation of the members accidentally. The lower end of stator housing 19 is provided with holes 23a providing points for application of pressure to - lock ring 22a to permit threaded joint 33 to be separated. An "0" ring 24a positioned in groove 25a prevents leakage of fluid through threaded joint 33.
Bearing pack housing 35 extends from threaded joint 33 at its 109~0Z0 upper end to a lower box end portion 36 which is internally threaded ~oint 33 at its upper end to a lower box end portion 36 which is internally threaded and has a threaded ~oint 37 with bearing makeup sub 38. At its extreme upper end, bearing pack housing 35 has an interior diameter defining an inner surface 39 which is an extension or projection of the inner surface of sta-tor makeup sleeve 30. A short distance below the upper end of bearing pack 35, the interior diameter thereof is enlarged at bev-eled surface 40 to surface 41 defining a lubricant chamber which will be subsequently described in more detail. At the lower end of surface 41 defining lubricant chamber, there is a bevel or shoulder 42 opening into a still further enlarged portion having inner surface 43 enclosing the various radial and thrust bearings.
Surface 43 terminates in the interior threaded portion at the lower box end 36 of the bearing pack housing.
At the upper end of the turbodrill, inside stator housing 19, there is positioned rotor shaft 44 which has a generally cylindri-cal exterior surface 45 terminating at the upper end in threaded portion 46 and at the lower end in threaded portion 47. Rotor shaft 44 has a plurality of rotor members 4~ stacked thereon in abutting relationship and blades or vanes 49 vertically aligned with the stator vanes 27.
Reference is now made to Figs. 2 to 5, inclusive, which ill-ustrate the construction and relationship of the stator and rotor members in more detail. In Fig. 3, it is seen that stator member 26 comprises an outer sleeve 50 and inner sleeve 51 with vanes or blade members 27 positioned there between and uniformly spaced around the periphery thereof. The outer surface of outer sleeve 50 abuts the inner surface of stator housing 19 securely to pre-vent slippage of the stator member relative to the housing. Theinner surface of inner sleeve 51 is a smooth bearing surface in which rotor members 48 are guided for smooth rotary motion.

lO~;OZO

Rotor members 48 comprise hub portion 52 from which blade or vane members 49 extend and sleeve portion 53. The exterior surface 54 of sleeve portion 53 is a smooth bearing surface which fits the inner bearing surface of inner sleeve 51 of stator member 26.
The inner surface 55 of sleeve 54 and hub 52 is a smooth surface and is provided with groove or key way 56 for securing rotor mem-bers 48 non-rotatably on rotor shaft 44. In Figs. 4 and 5 there are shown detail end views of the blade or vane nmembers 49 and 27, respectively. The blade or vane members are generally cresent-10 shaped. In Fig. 4 vane or blade member 49 is shown in substan-tially enlarged detail. Vein member 49 has an upper end 57 which is the inlet end of the vane for receiving fluid (i.e. mud) and the lower end 58 which is the outlet or exit end for discharge of fluid from the blade or vane. The shape of the blades or vanes is critical in the design of this turbodrill. In particular, the exit angle of the blade or vane must be in a very narrowly defined range in order to produce a maximum torque in the turbine. In Fig. 4, the line 59 is the center line of the rotor shaft and line 60 is a line normal thereto. The exit angle of the blade or 20 vane 49 is measured as the angle between line 61 and the normal line 60. Line 61 is a tangent to a curve lying on the mid points between the inner curve 62 and outer curve 63 of blade or vane member 49. The angle between lines 60 and 61 must lie within a range from 14 to 23 and an angle of 18 - 21 is preferred.
At this exit angle for the blade or vane member, the maxiumum rotary thrust or torque is obtained for the turbine. As noted, Fig. 4 is an enlarged detail view of vane or blade member 49 of rotor 48. The structure of the vane or blade members 27 of sta-tor 26 is the mlrror image of vane or blade members 49 in all 30 details.

Rotor members 48 are positioned on rotor shaft 44 in a stacked lO~tSO;~O

relation, as shown in ~ig. lA, with vane or blade members 49 aligned vertically with vane or blade members 27 of stator mem-bers ~6. Rotor members 48 are positioned on shaft 44 with the key ways 56 thereof aligned and aligned with a longitudinally extend-ing groove ill rotor shaft 44. A steel wire (not shown) is inserted in the mating grooves of shaft 44 and rotor members 48 to secure the rotor members non-rotatably thereon. The lower end of the stack of rotor members abuts rotor spacer ring 64 which seats against the upper end 65 of splined connecting member to be sub-sequently described. At the upper end of rotor shaft 44 there is positioned a cap or makeup screw member 66 which is internally threaded at 67 and forms a tight threaded connection with the threaded end portion 46 of rotor shaft 44. When cap member 66 is tightened in positioned its lower end portion 68 abuts the upper-most rotor member 48 and compresses the stack of rotor members tightly on rotor sha~t 44. Cap member 66 is closed at its upper end and has one or more theaded apertures 69 in which there are positioned set screws 70 to secure cap member 66 against loosening during operation.
Upper spline member 71 has an upper end portion 65 abutting rotor spacer ring 64 as previously described. ~pline member 71 is internally threaded and forms a threaded connection 72 with the lower end portion 47 of rotor shaft 44. Spline member 71 is hollow and has an exterior surface 73 spaced from the inner surface of stator makeup sleeve 30 to define an annular passageway therebe-tween.Spline member 71 has a plurality of passages 74 opening into the interior thereof for passage of fluid from the turbine section of the turbodrill. The lower end portion 75 of spline member 71 abuts ring-shaped spline spacer 76. Spline member 71 has a plur-ality of grooves 77 in the lower or box portion 75 thereof which receive spline pins 78. A lower spline member 79 has upper pin 10950~0 portion 80 provided with grooves 81 which receive the other side Or spline pins 78. Spline member 75 has a peripheral shoulder 82 which receives the lower end of space member 76. The lower or box end 83 of spline member 79 is internally threaded to receive the upper end of bearing shaft 84 in a fitted connection as indi-cated at 85. A set screw 86 is provided to prevent loosening of threaded ~oint 85 duringoperation. Spline member 79 has interior longitudinal passage 87 which communicates with passage 74 from spline member 71 at one end and with the interior longitudinal passage 88 in bearing shaft 84 at the other end. Spline member 71 and 79 and spline pins 78 provide a splined drive connection between rotor shaft 44 and bearing shaft 84.
Bearing shaft 84 is provided wlth an upper sleeve 89 which abuts the lower end of spline member 79 at its upper end and abuts another bearing shaft sleeve 90 at its lower end. The outer sur-face of sleeve 89 is spaced from the inner surface 41 of bearing pack housing 35 to define an annular passage 91 in which there are positioned a lubricant grease or oil and a pair of annular-shaped floating piston members 92 and 93, respectively. Piton member 92 comprises a piston body 94 with chevron-shaped seals 95 on one side and elastic compressible seals 96 on the other side.
SEals 95 and 96 are compressed by end cap 97 held in place by a cap screw (not shown). The seals on piton member 92 are of well known design and include a central spac-er member and end spacers which are compressed against the seals by end cap 97. Piston mem-ber 93 is constructed identically to piston member 92 and the detailed parts thereof are not separately identified. Piston mem-bers 92 and 93 have a sliding fit in the space between the inner surface 41 of bearing pack housin,g 35 and the outer surface of sleeve member 89 and have lubricant~ grease or oil positioned between the piston members and in the space below piston member ~O'~t50ZO
93 .
The bottom end of lubricant chamber 91 is derlned by the upper surface of bearing shaft sleeve 90 and the upper end surface of housing upset ring spacer 98. At the lower end of lubricant chamber 91 there are provided a pair of openings closed by pipe plugs 99 and 100, which are used for filling the chamber 91 with lubricant.
The lower end of member 98 is enlarged and has a shoulder portion 101 which abuts the bevel or shoulder 42 on housing 35.
The lower end of spacer 98 abuts the upper end of bearing housing spacer 102. Positioned below sleeve 90 and spacer 102 are a series of radial bearings and vertical thrust bearings which are sealed against lubricant leakage at the bottom of the drill by a radial seal.
The upper radial bearing consists of an outer ring 103 which supports a plurality of equally spaced roller bearing elements 104.
A separate bearing ring 105 is positioned on bearing shaft 84 and completes the radial bearing assmebly. A radial bearing of this design is adequate for high speed turbodrill of the type disclosed herein. A suitable radial bearing for a 7 3/4 inch turbodrill is the MR-64 or MR--88 bearing manufactured by McGill Manufacturing Co., Inc., Valparaiso, Indiana 46383.
A bearing shaft sleeve 106 is positioned on bearing shaft 84 for rotation therewith and abuts the lower end of bearing ring 105 which is also fitted on bearing shaft 84 for rotation therewith. Ring member 107 is fitted tightly inside housing 35 and has sufficient clearance from sleeve 106 to permit ro~ation thereof. The upper end of ring 107 abuts the lower end of bearing ring 103 which is also tightly fitted in housing 35. The lower end of ring 107 is provided with a palr of grooves 108 in which there are positioned compression spring3 109. Spring washer 110 10'350Z0 rlts against co~ ression springs 109 and abuts the upper annular plate or bearing ring 111 Or the uppermost vertical thrust bear-ing. The vertical thrust bearing consists of upper bearing ring 111~ lower bearing ring 112, and a plurality of roller bearing ele-ments 113 spaced equally around the bearing and secured in place by a bearing race (not shown). Upper bearing ring 111 fits tightly against housing 35 and has a clearance relative to sleeve 106.
Lower bearing ring 112 has a tight fit on sleeve 106 and a clear-ance relative to the inner wall surface of housing 35.
A thrust bearing spacer ring 114 is fitted tightly on bear-ing shaft 84 and has a clearance relative to housing 35. The upper end of spacer 114 is provided with a pair of grooves 115 in which there are positioned compression springs 116 which press against lower bearing ring 112. The lower end of spacer 114 abuts bearing shaft sleeve 117 and is provided with a pair of grooves 118 in which there are positioned compression springs 119. The lo~er end of spacer 114 also abuts the upper ring of the lower vertical thrust bearing.
The lower vertical thrust bearing consists of upper ring 120 which fits tightly on bearing shaft sleeve 117 and has a small clearance relative to the inner surface of housing 35. There is also provided a lower bearing ring 121 and a plurality of roller bearings equally spaced and secured in place by a bearing race (not shown). Lower bearing ring 121 fits tightly inside housing 35 and has a slight clearance relative to bearing shaft sleeve 117.
Immediately below the bearing ring 121 is spring washer 123 which bears against compression springs 124 carried in grooves 125 in the upper end of ring member 126. Ring member 126 is the same as ring member 107, but reversed in position.
33 Below ring member 126 and sleeve 117 there is positioned the intermediate radial thrust bearing. This bearing consists of ~0~5020 outer bearing ring 127 which carries a plurality of roller bear-ing members 128 secured thereon for rotary movement. An inner ring 129 is secured on bearin~ shaft 8ll.
Below the intermediate radial bearing, there is positioned bearing housing spacer 130 which fits tightly within the bearing housing 35. There is also positioned bearing shaft upset spacer ring 131 which has a shoulder 132 which abuts against shoulder 133 on the bearing shaft. Space between spacers 130 and 131 is sufficient for passage of lubricant to the lower radial bearing.
Spacers 130 and 131 abut the upper end portions of the lower most radial bearing. This bearing consists of outer ring 134 which has a plurality of equally spaced roller bearing members 135 secured thereon and bearing ring 136. Outer ring 134 is tightly ~itted inside housing 35 and inner bearing ring 136 is fitted on bearing shaft 84 for rotation therewith.
At the lower end of housing 35, bearing makeup sub 38 is tightened against the lower end of bearing ring 134 of the lower most radial bearings. On the bearing shaft 84, there is positioned bearing seal sleeve 137 which, at its upper end abuts the lower end of bearing ring 136 and at its lower end abuts bearing shaft end ring 138 which is fitted on shoulder 139 of the enlarged lower end 140 of the bearing shaft. Bearing makeup sub 138 is secured against separation of its threaded connection by coop-erating grooves 20b and 21b enclosing lock ring 22b. Holes 23b provide for application of pressure for release of lock ring 22b.
Sub 38 is also provided with a pheripheral groove 24b in which there is positloned an "O" rin~ seal 25b.
A dynamic radial seal is provided between sub 38 and seal sleeve 137 to prevent loss of lupricant from the bearings. The seal is a chevron-type seal having upper and lower backup rings 141 and 142, respectively. The middle portion of the seal is a spacer member 143. Above and below the spacer medium are posi-~o~o~o ioned a plurality of chevron seals 144 which are maintained in compression to provide a seal against sub 38 and against sleeve 137 to prevent leakage of lubricant from the bearings d~lL in-]
operation of the turbodrill~ Upper spacer member 141 abuts a retaining ring 145 and is held in place thereby. The lower end of spacer ring 142 abuts compression spring 146 which is posi-tioned in groove 147.
The lower enlarged end portion 140 of bearing shaft 84 is threaded internally as indicated at 148. This threaded opening received and secures in place the hollow connector sub 149 of drill bit 150. The turbodrill is illustrated as driving a rotary-type drill bit 150. It should be understood, however, that any suitable drill bit could be used of the various types used with conventional drills utilizing various types of down hole motors. In particular, the turbodrill is particularly useful with solid head diamond bits as is illustrated in Fox U.S. Patent 3,971,450.

OPERATION

The turbodrill is assembled as illustrated in Figs. lA, lB, lC, and 1~. The housing is in several sections, as described above, and is threadly connected at several points. Since the turbodrill housing is held stationary and the drill is driven at high speed there are substantial torques placed upon the threaded joints which tend to cause those joints to unscrew. In the past, threaded joints have been protected against unscrewing by use of set screws. However, set screws sometimes come loose themselves and the desired protection for the threaded joint may not be obtained. In this construction, the threaded joints are protected by a lock ring arrangement which is shown in use for se~eral threaded connections. In Fig. 6, the lock ring arrangement is J~0~3t~ 0 shown in considerable detail. In Fig. 6 it is seen that the lock ring 22a has a normal expanded condition. When threaded connec-tion 33 is made, the housing 29 slides past lock ring 22a until grooves 20a and 21a reach a mating relation, at which point, lock ring 22a springs into the position indicated locking the parts together to prevent separation of the thread. In Fig. 7 an appa-ratus is illustrated for releasing the lock ring to permit the threaded ~oint to be unscrewed. The apparatus consists of ring member 151 having a plurality of screws 1~2 around the periphery thereof. The screws 152 are adjusted to enter holes 23a at uni-formly spaced points around the housing 29 and press uniformly against lock ring 22a until it is compressed to point where it clears the edge of groove 20a and permits the threaded joint to be separated. Fig. 6B illustrates the identical arrangement but uses a lock ring 20a which is a straight spring member instead of an annularly deflected spring as in Fig. 6A. The operation is otherwise identical.
During assembly of the apparatus a suitable lubricant grease or oil, which will withstand the temperatures normally encountered by the turbodrill, is introduced through the lower opening 100, after unplugging the same, to fill the lower portion of the turbo-drill with lubricant. The lubricant introduced through opening 100 fills and completely surrounds the bearings and the radial seals. Lubricant is also introduced through opening 99, after unplugging the same to fill the space above piston 93 (as shown in dotted lines) and cause piston 92 (as shown in dotted lines) to rise above it. Sufficient lubrlcant is introduced to cause the pistons to be positioned substantially as shown in full iine in Figs. lB and lC. The holes 99 and 100 are plugged to preYent loss of lubricant.

~o~ o~o When the turbodrill is connected to drill strin~ 1~ as shown in Fig. lA, drilling mud is pumped through the drill string at a high rate of flow and through the turbodrill. The drilling mud flows through passage 15 into the annular space at the upper end of the turbine section. The drilling mud flows through each of the turbine stages causing the turbine to rotate at a high speed. The drilling mud flows past each of the vanes 27 of the stator members 26 and is directed from those vanes at a high velocity against vanes 49 of rotor mem-bers 48. The shape of the vanes of the stator and roto~ mem-bers has been discussed fully in connection with the description of the assembled apparatus. The shape of the vanes, particularly the exit angle, is designed to create a maximum thrust on the rotor members and a maximum torque on the rotor shaft 44 as the drilling mud is pumped through the turbine section. As indicated above, a large number of turbine elements make up the turbine section. In a typical 7 3/4 inch turbodrill there are fifty sets of stator members and fifty sets of rotor members, which results in the production of a high torque and a high speed of turning of the rotor shaft 44.
The rotor shaft 44 which is turning at a high rate of speed is connected by a splined connection, as described above, to bearing shaft 84. The drilling mud flows from the turbine section through the annular space around the splined connection and through the passage in the middle of the splined connection into the hollow passage 88 extending through the bearing shaft to the exterior of the drill where the mud is discharged through the drill bit (whether a rotary bi~ or a solid h~ad bit~ and then flows back up the hole being drilled to remove cuttings from the hole. The drill mud flows at least partly 10~0~0 around the splined connection at the top of the bearing shart and applies a hydraulic force against the upper end of piston 92. The piston 92 is therefore maintained under a high hydrostatic pressure of drilling mud which is flowing through the turbodrill. The pressure on piston 92 presses against the lubricant in the space 91 and applies pressure through piston 93 to maintain the lubricant in the space below the piston 93 and lubricant around the bearings and radial seal under a substantial hydrostatic pressure. In the past, floating pistons have been used to pressurize lubricant systems in turbodrills. However, drilling mud has eventually eroded the pistons and penetrated into the bearing and sealing areas which resulted in the destruction of the working parts of the turbodrill. In this construction, the double piston arrange-ment with lubricant providing a hydraulic fluid between the pistons protects the lower piston against contamination by the drilling mud and provides protection and greater life for the seal.
In the operation of the turbodrill, the design of bearings and of seals is of critical importance. The bearings and the seals in prior art turbodrills are the points where the highest incidence of failure has occurred. The radial bearings are not a major problem in that the radial loads are much smaller than the thrust loads and the space constraints are not so great as on the radial bearings. As described above, roller-type radial bearings are used herein--Mc~Gill MR-64 and MR-88 bearings being a preferred type.
In this turbodrill the thrust bearings are an important feature of construction. There are two sets of thrust bearings used~ The upper thrust bearings carry the upper thrust produced ~0~;020 during drilling. The lower thrust bearings carry produced when , the motor is rotated off bottom and in an alternate embodiment Or the invention carry the operating thrust after the upper bear-ings have worn out. This embodiment is to be described in con-nection with Fig. 8 of the drawings. The preferred thrust bear-illgS described above are roller-type thrust bearings supported between two annular plates or rings. A suitable thrust bearing, which is used in this apparatus, is the ATH734 roller thrust bearing manufactured by Andrews Bearing Corporation~ Spartan-burg, S. Carolina 29304. this bearing will carry a dynamic load of 122,000 pounds.
As noted aboveg the seals in the bearing section and thelubrication system are of substantial importance. The bearings in prior art turbodrills have had very short lives because they operated under direct exposure to the drilling mud. In this improved turbodrill, the entire bearing section is operated with a sealed lubrication system where the oil or grease is pressur-ized by floating pistons as previously described. The seals which prevent the loss of lubricant from the bearing section are most important. The prior art drills which have attempted to use sealed lubricant systems have generally used packing type seals or compressed rubber seals which in many cases apply such high forces to the bearing shaft as to make it difficult to rotate. In this improved turbodrill, the rotary seals for the bearings is a multiple chevron-type seals which prevents loss of lubricant, prevents intrusion of drilling mud to the bearings, thus, increasing substantially the life of the bearings and of the drill. The double piston arrangerrlent not only protects the lower piston but also provides lu,bricant for the bearings after the lower piston reaches its bottom position , as the lubricant io~tjo~o between the pistons then leaks past the lower piston.

AN ALTERNATE EMBODIMENT_ In the operation of a turbodrill, when the upper thrust bearings which carry the load during drilling are worn out or damaged and fail to function, it has previously been necessary to remove the drill from the hole and repair the bearings before the turbodrill can continue to function. Because of the very high cost per hour of operating a drill, trips to the surface for repair or service are to be avoided or delayed as long as possible. In Fig. 8 there is illustrated an alternate embodiment of the invention in which it is possible to operate the turbodrill during drilling operation utilizing the lower thrust bearings are worn out or become damaged.
In Fig. 8 there is shown a detail view in the area of the joint between the stator housing sub and the stator housing.
The cap member 66 on rotor shaft 44 has a tubular sleeve 153 secured thereon as by welding or the like. Sleeve 153 has an upper surface 154 which is beveled to provide a valve seat which is normally opened. In the side walls of sleeve 153 are a plurality of enlarged holes or apertures 155.
During normal operation of the turbodrill the mud flows through the drill as described above, except that in this por-tion of the drill the mud is flowing through and around sleeve 153 berore it enters the annular space around the rotor shaft.
W~len the upper thrust bearings have been damaged or worn out, as indicated by difficulty in operation of the turbodrill, a ball 156 Or steel~ or other suitable material, is dropped through the drill string and se,ats on the beveled surface 154.

When this occurs, the drilling mud can no longer ~low through sleeve 153 but must flow only around it. The flow passage ror 10~0~0 the drilling mud is thererore substantially reduced whlch cre-ates a higher back pressure in -the inlet portion of the turbo-drill. This higher hydrostatic back pressure of drilling mud tends to ~orce the housing upper slightly relative to the rotor and bearing shafts and the drill so that the drill acts as if it is running orf bottom. Under this higher hydrostatic dril-ling mud pressure the lower thrust bearings carry the thrust load Or the drilling operation. The rotor shaft, bearing shaft~
and drill bit can therefore continue to rotate with the lower thrust bearings carrying the entire thrust in a vertical direc-tion. This allows the drilling to continue using the lower thrust bearings without necessitating a trip to the surface for the drill ~or repair of the bearings. The drilling operation can therefore continue until the lower thrust bearings are dam-aged or worn out before it is necessary to bring the drill to the surface for service or repair.

ANOTHER EMBODIMENT OF THE INVENTION

In Fig. 9 there is illustrating still another embodiment Or the invention which provides, as an optional feature, a means ror indicating the loss of lubricant. In Fig. 9 there i~ illus-trated a modification of the rotor at the base of the lubricant passage 91 below piston 93. In this embodiment, rotor shaft 84 is provided with a hole or aperture 157 which opens into the longitudinal interior passage 88. A plug member 158 fits in aperture 151 and extends partly into passage 88. Plug member 158 is provided with an "O" ring seal 159 to prevent loss of lubricant. Plug member 159 is provided with an abutment 160 whi~h extends through a hole or aperture 161 in sleeve 89.
In this embodiment, when the lubrisant has gradually leaked 10'~0~0 from the seal lubrication system, piston 93 gradually drops with the fall in 1ubricant level. In Fig. 9, plston 93 has reached a posltion where it is almost ready to contact abutment 160 on plug member 158. As further lubricant is lost from the system piston 93, under pressure of drilling mud above, will more to a point where it engages abutment 160 and forces the same outward.
The force supplied is sufficient to break the flange 162 on plug 158 and forge the plug into the passage 88 in the rotor shaft 84.
Plug 158 temporarily interreres with the flow of drilling mud through the turbodrill. This is registered on the surface by detection of a very sudden surge in drilling mud back pressure.
This surge in back pressure indicates that there is an obstruc-tion in the turbodrill.
The plug 158 is formed of a friable material which will create the desired obstruction in the drill but which will dis-integrate within a relatively short time as the drilling mud flows past it. The sudden upsurge in back pressure of drilling mud followed by a return of the pressure to normal gives an indication that the indicator plug has been dislodged and that the lubricant is substantially gone from the sealed lubrication system. At this point in the operation the turbodrill can be operated only for a short time and then must be removed to the surface for introduction of more lubricant.

ANOTHER EM~ODIMENT

In Figs. lE and lF of the drawings there is shown an alter-nate embodiment of the invention in which means is provided to relieve the mud pressure against the rotary bearing seals. In this embodiment, pump means is provided in the form of a rotary pump carried on spline member 79 to pump mud away from the rotary sealing piston 92. The pump consists of hub portion 163 10~ 020 supported on spline member 79 and having a plurality Or blade or vane members 164 extending outward therefrom. The vane mem-bers 164 have a shape substantlally the same as vane members 49 but have a pitch which is opposite thereto. The vane members 164 turn within an enlarged housing bore 165 and function as a rotary pump to pump the drilling mud (or other drilling fluid) away from the bearing seals and relieve the pressure thereon.
In the embodiment shown in Fig. lF, the rotary pump, consisting of hub 163 and vanes 164,is positioned on the upper spline mem-ber 71 adjacent to passage 74 therein.
In this embodiment of the invention the various part.s are shown and described in Figs. lA, lB, lC, and lD and function in exactly the same manner. The only difference is in the rotary pump described above which functions to pump mud ~or other dril-ling fluid) away from the rotary seals. The vanes 164 on the pump may be of sufficient pitch to provide any suitable amount of pumping action. As a practical matter, however, sufficient mud pressure would be allowed to reach the sealing piston to maintain the same under sufficient pressure to pressurize the lubricant chamber.

A FURTHE~ EMBODIMENT - --. In this embodiment the down hole drilling motor of Figs.
lA and lD is modified to divide the flow of drilling fluid ~i.e., mud) to balance the pressure on the bearing seals. At the upper end of turbodrill 210 there is provided a stator housing sub 211 having a threaded box end portion 212 forming a threaded connection 213 with the lower end of a drill string 214. Stator housing sub 211 has an internal longitudinal pas-sage 215 communicating with the open end Or drill string 214.

10~CiO~O

$tator housin~ sub 211 has a threaded pin portion 216 which is threadedly connected as at 217 in the box end portion 218 of the stator housing 219. Stator housing box portion 218 has an internal annular groove 220 therein which mates, when assembled~ with an annular groove 221 in the pin portion 216 of stator housing sub 211. A lock ring 222 extends peripherally around the turbodrill in the annular space provided by matching grooves 220 and 221 and abuts the walls of said grooves to pre-vent disassembly of said stator housing from said stator housing sub accidentally. Stator housing box portion 218 is also pro-vided with a plurality of holes 223 uniformly spaced to provide points for application of pressure to lock ring 222 to permit separation of stator housing 219 from stator housing sub 211.
Threaded connection is sealed against leakage by "0" ring 224 positioned in groove 225.
The turbine section of the turbodrill is positioned in the stator housing 219 just below the threaded ~oint 217 con-necting to the stator housing sub 211. The stator portion of the turbine consists of a plurality of stator members 226. The stator members 226 are annular in shape and provided with vanes or blades 227. Stator members 226 have an exterior surface pro-viding a sliding fit in the inner surface of stator housing 219.
Stator members 226 are positioned as a stack of abutting members extending longitudinally within the stator housing 219. In a typical turbodrill having a 7 3/4 inch diameter, there are 50 of the stator members and ~0 Or the matching rotor members.
The stator mernbers are preferably made of a hard beryllium copper alloy which is wear-resistant and which has a slightly higher coefficient of expansion ~han the steel of stator housing 219. The stack of stator members 226 is maintained under com-~o~o~o pression in the stator housing 19 with the result that the mem-bers are ex~anded to fit tightly against the inner surface Or stator housing 219 and resist slippage therein. Also, because ,of,the higher thermal coefficieJIt of expansion, the stator members 26 tend to expand more at the high temperatures encoun-tered in use Or the turbodrill with the result that the increase in temperature encountered during operation causes stator mem-bers 226 to fit more tightly within stator housing 19 and e~fectively prevents slippage therein.
At the upper end of stator housing 219 there is positioned an annular stator spacer 228 which positions the uppermost stator member 226 relative to the end of stator housing sub 211.
At the lower end of stator housing 219there is a box portion 229 which is internally threaded and receives tubular stator makeup sleeve 230 in threaded joint 231. The lower end of sleeve 230 is notched as indicated at 232 to receive a wrench for tighten-ing sleeve 230 in threaded joint 231. When stator makeup sleeve 230 is tightened to the position shown, the upper end thereof abuts the lowermost stator Member 226 and compresses the entire stack o~ stator members against each other and against annuiar stator spacer member 228. ~tator makeup sleeve 230 when fully tightened maintains the stack of stator members 226 under sufficient compression to press them tightly against the inner surface Or stator housing 219 and prevents slippage Or the stator members during operation-as described above.
The lower box end 229 Or stator housing 219 is connected in a threaded joint 233 to the threaded upper pin end 234 of bearing pack housing 235. Just below threaded joint 233 there is provided annular groove 221a in bearing pack housing 235 and annular groove 220a in stator housing 219 and a spring lock ring 222a positioned therein to prevent separation Or the members 10~50~

accidentally. The lower end Or stator housing 219 is provided `with holes 223a providing points for application of pressure to lock ring 22a to permit threaded joint 233 to be separated. An - "O" ring 224a positioned in groove 225a prevents leakage of fluid through threaded ~oint 233.
Bearing pack housing 235 extends from threaded joint 233 at its upper end to a lower box end portion 236 which is inter-nally threaded and has a threaded Joint 237 with bearing makeup sub 238. At its extreme upper end, bearing pack housing 235 has an interior diameter defining an inner surface 239 which is an extension or pro;ection of the inner surface of stator make-up sleeve 230. A short distance below the upper end of bearing pack 235 the interior diameter thereof is enlarged at beveled surface 240 to surface 241 defining a lubricant chamber which will be subsequently described in more detail. At the lower end of surface 241 defining lubricant chamber there is a bevel or shoulder 242 opening into a still further enlarged portion having inner surface 243 enclosing the various radial and thrust bearings. Surface 243 terminates in the interior threaded por-tion at the lower box end 236 Or the bearing pack housing.
At the upper end of the burbodrill, inside stator housing219, there is positioned rotor shaft 244 which has a generally cylindrical exterior surface 245 terminating at the upper end in threaded portion 246 and at the lower end in threaded por-tion 247. Rotor shaft 244 has a plurality Or rotor members 248 stacked thereon in abutting relationship and blades or vanes 249 vertically aligned with the stator vanes 227.
Stator member 226 comprises an outer sleeve 250 and inner sleeve 251 with vanes or blade m~mbers 227 positioned therebe-tween and uniformly spaced around the periphery thereof. Theouter surrace Or outer sleeve 250 abuts the inner surface of 10'~020 stator housing 219 securely to prevent sllppage of the stator member relative to the housing. The inner surface of inner sleeve 251 is a smooth bearing surface in which rotor members 248 are guided for smooth rotary MOtiOn.
Rotor members 248 comprise hub portion 252 from which blade or vane members 249 extend and sleeve portion 253. The exterior surface 254 of sleeve portion 253 is a smooth bearing surface which fits the inner bearing surface of inner sleeve 251 of stator member 226. The inner surface 255 Or sleeve 253 and hub 252 is a smooth surface and is provided with groove or keyway ~not shown) for securing rotor members 248 non-rotatably on rotor shaft 244. The bl~de or vane members are generally crescent-shaped in CrQSS-SectiOn. Vane member 249 has an upper end which is the inlet end of the vane for receiving fluid (i.e., mud) and a lower end which is the outlet or exit end for discharge of fluid from the blade or vane. The shape of the blades or vanes is critical in the design of this turbodrill.
In particular, the exit angle of the blade or vane must be in a very narrowly defined range in order to produce a maximum torque in the turbine. The exit angle of the blade or vane 249 is measured as the angle between a tangent to a curve lying on the mid points between the inner curve and outer curve of blade or vane member 249 and a line normal to the center line of the rotor. The exit angle must lie within a range from 14~ to 23 and ~n an~le of 18 to 21 is preferred. At this exit angle for the blade or vane member, the maximum rotary thrust or torque is obtained for the turbine. The structure of the vane or blade members 227 of stator 226 is the mirror image of vane or blade members 249 in all details.
Rotor members 248 are positioned on rotor shaft 244 in a stacked relation, as shown in Fig. 10A, with vane or blade mem-~0~5020 bers 249 aligned vertically with vane or blade members 227 of stator members 226. ~otor members 248 are positioned on shaft 244 with the keyways thereof aligned and aligned ~Jith a longi-tudinally extending groove in rotor shaft 244. A steel wire (not shown) is inserted in the mating grooves (not shown) of shaft 244 and rotor members 248 to secure the rotor members non-rotatably thereon. The lower end of the stack of rotor members abuts rotor spacer ring 264 which seats against the upper end 265 of splined connecting member to be subsequently described. At the upper end of rotor shaft 244 there is posi-tioned a cap or makeup screw member 266 which is internally threaded at 267 and forms a tight threaded connection with the threaded end portion 246 of rotor shaft 244. When cap member 266 is tightened in position its lower end portion 268 abuts the uppermost rotor member 248 and compresses the stack of rotor members tightly on rotor shaft 244. Cap member 266 has a central opening 366 and has one or more threaded aper-tures 269 in which there are positioned set screws 270 to secure cap member 266 against loosening during operation. At the lower end of the turbine section ad~acent to the lowermost rotor vanes, there are provided one or more openings 235a through the wall of housing 19 for discharge of drilling fluid therethrough; optionally, a shield 236a may be provided out-side openings 335.
Upper spline member 271 has its upper end portlon 265 abut-ting rotor spacer ring 264 as previously described. Spline mem-ber 271 is internally threaded and forms a threaded connection 272 with the lower end portion 247 of rotor shaft 244. Spline member 271 is hollow and has an exterior surface 273 spaced 3 from the inner surface of stator makeup sleeve 230 to define an annular passageway therebetween. The lower end portion 275 ~o~o~o Or spllne member 271 abuts ring-shaped spline spacer 276.
Spline member 271 has a plurality of grooves 277 in the lower or box portion 275 thereof which receive spline pins 278. A
lower spline member 279 has upper pin portion 280 provided with grooves 281 which receive the other side of spline pins 278.
Spline member 279 has a peripheral shoulder 282 which receives the lower end of spacer member 276. The lower or box end 283 of apline member 279 is internally threaded to receive the upper end of bearing shaft 284 in a threaded connection as indicated at 285. A set screw 286 is provided to prevent loosening of threaded ~oint 285 during operation. Spline member 279 has interior longitudinal passage 287 which communicates with pas-sage 274 in member 271 and opening 366 at one end and with the interior longitudinal passage 288 in bearing shaft 284 at the other end. Spline members 271 and 279 and spline pins 278 pro-vide a splined drive connection between rotor shaft 244 and bearing 284.
Bearing shaf't 284 is provided with an upper sleeve 289 which abuts the lower end of spline member 279 at its upper end and abuts another bearing shaft sleeve 290 at its lower end.
The outer surface of sleeve 289 is spaced from the inner sur-face 241 of bearing pack housing 235 to define an annular pas-sage 291 in which there are positioned a lubricant grease or oil and a paid Or annular-shaped floating piston members 292 and 292, respectively. Piston member 292 comprises a piston body 2g4 with chevron-shaped seals 295 on one side and elastic compressible seals 296 on the other side. Seals 295 and 296 are compressed by end cap 297 held in place by a cap screw (not shown). The seals on piston member 292 are of well known design and include a central spacer member and end spacers which are compressed against the seals by end cap 297. Piston ~-o~ o member 293 is constructed identlcally to piston member 292 and t.he detailed parts thereof are not separately identified. Pis-tOIl members 292 and 293 have a sliding fit in the space between the inner surface 241 of bearing pack housing 235 and the outer surface of sleeve member 289 and have lubrlcant, grease or oil positioned between the piston members and in the space below piston member 293.
The bottom end of lubricant chamber 291 is defined by the upper surface of bearing shaft sleeve 290 and the upper end surface of housing upset ring spacer 298. At the lower end of lubricant chamber 291 there are provided a pair of openings closed by pipe plugs 299 and 300, which are used for filling the chamber 291 with lubricant.
The lower end of member 298 is enlarged and has a shoulder portion 301 which abuts the bevel or shoulder 242 on housing 235.
The lower end of spacer 293 abuts the upper end o~ bearing hous-ing spacer 302. Positioned below sleeve 290 and spacer 302 area series of radial bearings and vertical thrust bearings which are sealed against lubricant leakage at the bottom of the drill by a radial seal.
The upper radial bearing consists of an outer ring 303 which supports a plurality of equally spaced roller bearing elements 304. A separate bearing ring 305 is positioned on bearing shaft 284 and completes the radial bearing assembly. A radial bearing of this design is adequate for a high speed turbodrill of the type disclosed herein. A suitable radial bearlng for a 7 3/4 inch turbodrill is the MR-64 Or MR-88 ~earing manufactured by McGill Manufacturing Co., Inc.~ Valparaiso, Indiana 46383.
A bearing shaft sleeve 306 is positioned on bearing shaft 30 284 for rotation therewith and abuts the lower end of bearing ring 305 which is also fitted on bearing shaft 284 for rotation ~0~3S020 therewith. Ring member 307 is fitted tightly lnside houslng 235 and has suf`flcient clearance from sleeve 306 to per~it rotation thereof. The upper end of ring 307 abuts the lower end of bearing ring 303 which is also tightly fitted in housing 235.
The lower end oI' ring 307 is provided with a pair of grooves 308 in which there are positioned compression springs 30g. Spring washer 310 fits against compression springs 309 and abuts the upper annular plate or bearing ring 311 of the uppermost verti-cal thrust bearing. The vertical thrust bearing consists of upper bearing ring 311, lower bearing ring 312, and a plurality of roller bearing elements 313 spaced equally around the bear-ing and secured in place by a bearing race (not shown). Upper bearing ring 311 fits tightly against housing 235 and has a clearance relative to sleeve 306. Lower bearing ring 312 has a tight fit on sleeve 306 and a clearance relative to the inner wall surface of housing 235.
A thrust bearing spacer ring 314 is fitted tightly on bear-ing shaft 284 and has a clearance relative to housing 235. The upper end of spacer 314 is provided with a pair of grooves 315 in which there are positioned compression springs 316 which press against lower bearing ring 312. The lower end of spacer 314 abuts bearing shaft sleeve 317 and is provided with a pair of grooves 318 in which there are positioned compression springs 319. The lower end of spacer 314 also abuts the upper ring of the lower verticaI thrust bearing.
The lower vertical thrust bearing consists of upper ring 320 which fits tightly on bearing shaft sleeve 317 and has a small clearance relative to the inner surface of housing 235.
There is also provided a lower bearing ring 321 and a plurality 30 of roller bearings equally spaced and secured in place by a bearing race ~not shown). Lower bearing ring 321 fits tightly ~0~3 5~ZO
inside hollslng 235 and has a sllght clearance relatlve to bear-ing shaft sleeve 317. Immediately below the lower bearing ring 321 is spring washer 323 whlch bears against compression sprlngs 324 carried ln grooves 325 in the upper end of ring mem-ber 326. Ring member 326 is the same as rlng member 307, butreversed in position.
Below ring member 326 and sleeve 317 there is positioned the intermediate radlal thrust bearlng. This bearing consists of outer bearing ring 327 which carries a plurality of roller bearing members 328 secured thereon for rotary movement. An inner ring 329 is secured on bearing shaft 284.
Below the lntermediate radial bearing there is positioned bearing housing spacer 330 which fits tightly within the bear-ing housing 235. There is also positioned bearing shaft upset spacer ring 331 which has a shoulder 332 which abuts against shoulder 333 on the bearing shaft. Space between spacers 330 and 331 is sufficient for passage of lubricant to the lower radial bearing.
Spacers 330 and 331 abut the upper end port~ons of the 20 lowermost radial bearing. This bearing consists of outer ring 334 which has a plurality of equally spaced roller bearing mem-bers 33~ secured thereon and bear-ing ring 336. Outer-ring 334 is tightly fitted inside housing 235 and inner bearing ring 336 is fitted on bearing shaft 284 for rotation therewith.
At the lower end of housing 235, bearing makeup sub 238 is tightened against the lower end Or bearing ring 334 of the lowermost radial bearings. On the bearing shaft 2~4 there is - positioned bearing seal sleeve 337 which, at its upper end, abuts the lower end of bearing ring 336 and at its lower end 30 abuts bearing shaft end ring 338 which is fitted on shoulder 339 of the enlarged lower end 340 of the bearing shaft.

10~5020 Bearlng makeup sub 238 is secured against separation of its threaded connection by cooperating grooves 220b and 221b enclos-ing lock ring 222b. Holes 223b provide for application of pres-sure for release of lock ring 222b. Sub 238 is also provided with a peripheral groove 224b in which there is positioned an "O" ring seal 225b.
A dynamic radial seal is provided between sub 238 and seal sleeve 337 to prevent loss of lubricant from the bearings. The seal is a chevron-type seal having upper and lower backup rings 341 and 342, respectively. The middle portion of the seal is a spacer member 343. Above and below the spacer medium are posi-tioned a plurality of chevron seals 344 which are maintained in compression to provide a seal against sub 238 and against sleeve 337 to prevent leakage of lubricant from the bearings during operation of the turbodrill. Upper spacer member 341 abuts a retaining ring 345 and is held in place thereby. The lower end of spacer ring 342 abuts compression spring 346 which is posi-tioned in groove 347.
The lower enlarged end portion 340 of bearing shaft 284 is threaded internally as indicated at 348. This threaded opening receives and secures in place the hollow connector sub 349 (having internal passageway 351) of drill bit 350. The turbo-drill is illustrated as driving a rotary-type drill bit 350.
It should be understood, however~ that any suitable drill bit could be used of the various types used with conventional drills utilizing various types of down hole motors. In particular, the turbodrill is particularly useful with solid head diamond bits as is illustrated in Fox, U.S. Patent 3,971,450.

OPERAT-ION
The turbodrill is assembled as illustrated in Figs. 10A, 10B, 10C, and 10D. The housing is in several sections, as des-~o~ozo cribed above~ and is threadedly connected at several polnts.
Since the turbodrill housing is held statlonery and the drill is driven at high speed, there are substantial torques placed upon the threaded joints which tend to cause those joints to unscrew. In the past, threaded ~oints have been protected against unscrewing by use of set screws. However, set screws sometimes come loose themselves and the desired protection for the threaded joint may not be obtained. In this construction, the threaded ~oints are protected by the lock ring arrangement which is shown in use for several threaded connections.
During assembly of the apparatus a suitable lubrlcant grease or oil, which will withstand the temperatures normally encountered by the turbodrill, is introduced through the lower opening 300, after unplugging the same, to fill the lower por-tion of the burbodrill with lubricant. The lubricant introduced through opening 300 fills and completely surrounds the bearings and the radial seals. Lubricant is also introduced through opening 299, after unplugging the same, to fill the space above -piston 293 (as shown in dotted lines) and cause piston 292 ~as shown in dotted lines) to rise above it. Sufficient lubricant is introduced to cause the pistons to be positioned substan-tially as shown -in full line in Figs. lOB and lOC. The holes 2~9 and 300 are plugged to pre~ent loss of lubricant.
When the turbodrlll is connected to drill string 214 as shown in Fig. lOA~ drilling mud is pumped through the drill string at a high rate of flow and through the turbodrill. The drilling mud flows through passage 215 and divides into two streams, one of which flows through passage 366 and the other of which flows into the annular space at the upper end of the turbine section. The drilling mud which flows through each of the turbine stages causes the turbines to rotate at high speed.

~o~o~o One stream Or drllling mud flows past each Or the vanes 227 of the stator members 226 and is directed from those vanes at a hlgh velocity against vanes 249 of rotor members 248. The shape of the vanes of the stator and rotor members has been discussed fully in connection with the description of the assembled appa-ratus. The shape of the vanes, particularly the exit angle, is designed to create a maximum thrust on the rotor members and a maximum torque on the rotor shaft 244 as the one stream of dril-ling mud is pumped through the turbine section. As indicated above, a large number of turbine elements make up the turbine section. In a typical 7 3/4 inch turbodrill, there are fifty sets of stator members and fifty sets of rotor members, which results in the production of a high torque and a high speed of turning of the rotor shaft 244. The stream of drilling mud p2S-sing through the turbine section exits through passages 235 into the annulus (drill hole) around the turbodrill. The pres-sure of the drilling mud at the point of exit is essentially the hydrostatic pressure in the drill hole.
The rotor shaft 244 which is turning at a high rate of 20 speed is connected by a splined connection, as described above, to bearing shaft 284. Some of the drilling mud flows from the turbine section into the annular space around the splined con-nection at the top of the bearing shaft and applies a hydraulic force against the upper end of piston 292. The piston 292 is therefore maintained under the hydrostatic pressure of the stream of drilling mud which is exiting from the turbine section. The pressure on piston 292 presses against the lubricant in the space 291 and applies pressure through piston 293 to maintain the lubricant in the space below the piston 293 and lubricant around 3o the bearings and radial seal under a substantial hydrostatic pressure. In the past, floating pistons have been used to pres-lO~iOZO
surize lubricant systems in turbodrllls. However, drllllng Mud has eventually eroded the plstons and penetrated into the bearlng and sealing areas which resulted in the destruction of the work-lng parts Or the turbodrill. In this constructlon, the double piston arrangement with lubricant providing a hydraulic fluid between the pistons protects the lower piston against contamina-tion by the drilling mud and provides protection and greater li~e for the seal.
In the operation of the turbodrill, the design of bearings and of seals is of critical importance. The bearings and the seals in prior art turbodrills are the points where the highest incidence of failure has occurred. The radial bearings are not a major problem in that the radial loads are much smaller than the thrust loads and the space constraints are not so great as on the radial bearings~ As described above, roller-type radial bearings are used herein, McGill MR-64 and MR-88 bearings being a preferred type.
In this turbodrill the thrust bearings are an important feature of construction. There are two sets of thrust bear-ings used. The upper thrust bearings carry the upper thrustproduced during drilling. The lower thrust bearings carry the load produced when the mo~or is rotated off bottom. The pre--ferred thrust bearings described above are roller-type thrust bearings supported between two annular plates or rings. A
suitable thrust bearing, which is used in this apparatus, is the ATH734 roller thrust bearing manufactured by Andrews Bearing Corporation, Spartanburg, S.C. 29304. This bearing will carry a dynamic load of 122,000 pounds.
As noted above, the seals in the bearing section and the lubrication system are of substantial importance. The bearings in prior art turbodrills have had very short li~es because they 10"3~i020 operated under direct exposure to the drllling mud. In thls lmproved turbodrill, the entire bearing section is operated wlth a sealed lubrication system where the oil or grease is pressurized by floating pistons as previously described. The seals which prevent the loss of lubricant from the bearing sec-tion are most important. The prior art drills which have attempted to use sealed lubricant systems have generally used packing type seals or compressed rubber seals which in many cases apply such high forces to the bearing shaft as to make it difficult to rotate. In this improved turbodrill, the rotary seal for the bearings is a multiple chevron-type seal which pre-vents loss of lubricant, prevents intrusion of drilling mud to the bearings, thus increasing substantially the life of the bearings and of the drill. The stream of drilling mud which passes through passages 366~ 274, 288 and 351 and exits into the space adjacent the drill bit is balanced in pressure against the bottom hole pressure, and that pressure is applied against the bottom seals. As a result, there is no pressure drop across the bearing seals. The theory of operation is given below.
Drilling mud passes through the motor in two streams. The ma~ority of the mud passes (Qt) through the turbine blades and then vents to the annulus above the rotary seal. The remaining mud (Qb) passes through the rotor and through the drill bit.
The distribution of flow through these two passageways is con-trclled by the diameter of the noz~les used in passage 351 of the bit. The smaller the noz71es, the smaller the amount of fluid passing through the drill bit. The fact that mud is vented directly from the bottom of the turbine blades to the annulus allows annulus mud press~re to be applied to the float-~0~5Q20 lng piston in the lubricant reservoir. Consequently, the rotary seal ls sub~ected to annulus ~nud pressure on each side, thereby removing all differentlal mud pressure ~rom the rotary seal.
This design reduces the mud pump pressure requlred to operate the burbodrill since with conventional turbodrllls the bit pressure and turbine pressure are additive whereas with this design they operate in parallel. This concept can be used equally well with positive displacement motors (e.g., Moineau, vane, gear, etc.) The total ~10W~ Q, through the motor equals:

Q = Qt + Qb (1) where Qt = Flow rate through turbodrill passage 235 Qb = Flow rate through drill bit passage 151 The pressure drops across the drill bit and turbodrill are equal since they are in parallel:

Pb = Pt (2) Additional constrictions can be placed in series with either the turbodrill or the bit if so desired in order to alter the respective flow rates. The size of these constrictions can ~ be automat cally controlled in order to give the motor spe-cific operating characteristics. For exa~ple, this can be varled as a function Or flow rates, pressure drops, torques, bit weights or rotary speed.
The bit pressure drop varies as:
Pb = klwQ~ (3) where kl is a constant equal to:

kl =

~ LO~t~j~ZO
where w = Mud Density (lb/gal) Qb = Mud Flow Rate through Bit (GPM) C = Nozzle Coefficient ( 0.95) A = Nozzle Area tin2) The turbine pressure drop equals:
Pt = k2WQ~
where k2 = Design Constant ~ = Mud Density (lb/gal) Qt = Mud Flow Rate through Trubodrill (GPM) Combining Equations 2, 3, and 4:

klw Qb2 = k2WQ~
2 (5) A

Qt = ~ (6) Qb A
Equation 6 shows that the ratio of the flow rates through the turbodrill and through the bit is inversely proportional to the nozzle area and that it is independent Or the flow rate.
Therefore, once the bit nozzles are selected, this ratio remains constant! This greatly simplifies the operation of this pres-sure balanced turbodrill.
Substituting Equation 6 into Equation 1 yields:

~ * A (7) which shows that as A~ 0, all Or the flow is through the turbo-drill (Qt~ Q~ and that flow through the turbodrill decreases as A increases.
Means for preventing drill hole erosion is required. This ~0~5~ZO

is done by slanting the exit passage 235 or by placing sleeve 236 around the motor to direct the fluid upward.

AN ALTERNATE EMBODIMENT

In Figs. llA, lls, llC and llD there is shown an alternate embodiment of this turbodrill in which a different arrangement of passageways is used for balancing the pressure on the bear-ing seals. In the embodiment of the invention shown in these figures the structure is almost identical to that shown in Figs.
10A, 10B, 10C and 10D. Therefore, the same reference numerals are used in describing this embodiment where the parts are the same as in the previous embodiment. In fact, the changes between the two embodiments are such that only the features that are changed need be described.
In this embodiment, the ports or openings 235, in housing 219 and the peripheral shield 236 are eliminated. In this embodiment, spline member 271 has a plurality or passages 263 opening into the interior thereof for passage of fluid from the turbine section of the turbodrill. In this embodiment, a hollow tube 262 is positioned in opening 366 in cap member 266 and is sealed against leakage by an "O" ring 261. Tube 262 has an out-side diameter that is smaller than the passages through which it extends, thus leaving an annular passage around it for passage of drilling mud as will be subsequently described. The bottom end of tube 262 terminates inside the upper end of passage 261 in drill bit 350, which passage opens to the bottom of the drill hole through drill bit 350. Tube 262 is sealed in passage 261 by "O" ring 260. Tube 262 may be threaded at either or both of its ends and held rigidly in place by a threaded connection, if desired, in which case the "O" rings do not support the tube but merely seal against leakage. The cavity 259 in the lower end 340-~o~o~o of the bearing shart is vented to the lower end of the bore hold either through a plurality Or enlarged passages 258 in the threaded base Or drill bit 350 or, optionally, through enlarged passages 257 (shown in dotted line) through the wall of the enlarged por-tion 340 Or the bearing shaft. Passages 257, if used, are prefer-ably inclined upward to prevent erosion of the bore hole. With the exception o~ the features described above, the present embod-iment is the same as that shown in Figs. lOA, lOB, lOC and lOD.

OPERATION

In this embodiment, the drilling mud passes through the turbodrill in two streams. The ma~ority of the mud passes (Qt) through the turbine blades and through passage 263 in spline mem-ber 271 into the annular space around tube 262. The mud then passes on through this annular space through the bearing section into the enlarged interior space 25g in the lower end portion 340 of the bearing shaft. This larger flow of drilling mud then passes out into the bore hole either through passages 258 in the drill bit or passages 257 in enlarged portion 340 of the bearing shaft. This mud flow, which passes through the turbine section, 20 is operable to cause the turbine to rotate the drill bit ror carrying on the drilling operation. The smaller stream of drill mud passes into tube 262 and vents into the bottom Or the drill hole through passage 261 in drill bit 350. The distribution of flow through the smaller opening 261 or through the large passages 258 or 257 is controlled by the diameter of nozzles provided for flow control. The smaller the nozzle in passage 261 the smaller the amount Or mud passing through the drill bit. The fact that mud is vented from tne bottom Or the turbine blades to the bottom of the drill hole allows bsttom hole mud pressure to be applied to the floating piston in the lubricant reservoir. The bottom 10~5020 lubricant seals are llkewise sub~ected to bottom hole mud pres-sure. Conse~uently, the rotary seals are sub~ected to bottom hole mud pressure on each side and thus removing all differential mud pressure rrom the rotary seal.
The total flow, Q, through the motor equals:

Q Qt Qb where Qt = Flow rate through turbodrill passages 263 and 258 (or 257) Qb = Flow rate through drill bit passage 261 The pressure drops across the drill bit and turbodrill are equal since they are in parallel:

Pb = Pt Additional constrictions can be placed in series with either the turbodrill or the bit if so desired in order to alter the respective ~low rates. The size of these constrictions can be automatically controlled in order to give the motor specific operating characteristics. For example, this can be varied as a function of flow rates, pressure drops, torques, bit weights or rotary speed.
The bit pressure drop varies as:
_ ~ Q2 A2 (3) where k is a constant equal to:

kl =
l2û40C2 where w = Mud Density (lb/gal) Qb = Mud Flow ~ate through Bit (GPM) C = Nozzle Coefficient (0.95 A = Nozzle Area (in2) 10~ 0 The turbine pressure drop equals:

Pt = k2WQt (4) where _ k2 = Design Constant w = Mud Density (lb/gal) Qt = Mud flow Rate through Turbodrill (GPM) Combining Equations 2, 3, and 4:

klw Qb _ 2 A2 k2WQt (5) Qb ~ (6) Equation 6 shows that the ratio of the flow rates through the turbodrill and through the bit is inversely proportional to the nozzle area and that it is independent of the flow rate.
Therefore,~once the bit nozzles are selected, this ration remains constant! This greatly simplifies the operation of this pressure balanced turbodrill.
Substituting Equation 6 into Equation 1 yields-~ - ~r1/~Z t A (7) which shows that as A-~0, all of the flow is through the turbo-_ drill (Q~j~Q) and that flow through the turbodrill decreases as A20 increases.

The arrangements described in the last two examples above have provided for balancing the pressure on the bearing seals for a turbodrill. The arrangement of flow passages would work euqaily well in a down hole motor of the positive displacement type (e.g.
Moineau, vane, gear, etc. type motors).
While this invention has been described fully and completely, with special emphasis upon two preferred embodiments, it should be understood that within the scope of the appended cliams this invention may be practiced otherwlse than as speci~ically described herein.

Claims (15)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A downhole well drilling tool comprising housing means adapted to be connected to a drill string, a rotary shaft in said housing means and extending downward therefrom and adapted to support a drill bit, means to rotate said shaft, upper and lower thrust bearings positioned around said shaft within said housing means to support said shaft against opposite-ly directed vertically extending forces, said upper thrust bearings supporting said shaft against upward thrust during drilling operation, said lower thrust bearings supporting downward thrust of said shaft when lifted out of drilling operation, and means operable to shift the relationship of said lower thrust bearings and said shaft to cause said shaft to be supported on said lower thrust bearings during drilling operation.

2. A downhole well drilling tool according to Claim 1 in which one of said bearings comprises a plurality of radially extending bearing rollers lying in a plane normal to said shaft and supported between spaced annular plates, one of said plates being secured on said shaft for rotation therewith and the other of said plates being secured in said housing means.

3. A downhole well drilling tool according to Claim 1 in which said shaft rotating means is actuated by flow of drilling fluid through said tool.

4. A downhole well drilling tool according to Claim 3 in which said shaft rotating means is a turbine comprising a plurality of stator blades fixed in said housing means, a rotor shaft rotatably supported in said housing means, a plurality of rotor blades supported on said rotor shaft and cooperable with fluid flowing through said stator blades to effect rotation of said rotor shaft, and means operatively connecting said rotor shaft to said first named rotary shaft for effecting rotation thereof.

5. A downhole well drilling tool comprising housing means adapted to be connected to a drill string, a rotary shaft in said housing means and extending downward therefrom and adapted to support a drill bit, said housing means, and shaft being hollow and providing a longitudinal passageway for drilling fluid flowing from said drill string, means to ro-tate said shaft, upper and lower thrust bearings positioned around said shaft within said housing means to support said shaft against vertically extending forces, said upper thrust bearings supporting said shaft against upward thrust during drilling operation, said lower thrust bearings supporting said shaft when lifted out of drilling operation, and drilling fluid actuated means operable to shift the relationship of said thrust bearings and said shaft to cause said shaft to be supported on said lower thrust bearings during drilling operation.

6. A downhole well drilling tool according to Claim 5 in which each of said bearings comprises a plurality of radially extending bearing rollers lying in a plane normal to said shaft and supported between spaced annular plates, one of said plates being secured on said shaft for rotation therewith and the other plate being secured in said housing means.

7. A downhole well drilling tool according to Claim 6 in which said fluid actuated means includes means to change the pressure drop of drilling fluid flowing through said passage-way to shift the relationship between said bearings and said shaft upon predetermined increase in pressure drop.

8. A downhole well drilling tool according to Claim 5 in which said fluid actuated means includes means to change the pressure drop of drilling fluid flowing through said passage-way to shift the relationship between said bearings and said shaft upon predetermined increase in pressure drop.

9. A downhole well drilling tool according to Claim 8 in which said means to change the pressure drop of drilling fluid comprises valve means in said passageway closeable to restrict the flow of fluid through said passageway.

10. A downhole well drilling tool according to Claim 9 in which said valve means includes a normally open valve port adapted to be closed by a ball plug dropped through a drill string.

11. A downhole well drilling tool according to Claim 10 in which said valve port is in a member operatively supported on said shaft.

12. A bearing pack for a downhole well drilling tool comprising a housing to be connected to the housing of a well drilling fluid actuated downhole motor, a rotary bearing shaft positioned in said bearing pack housing having one end adapted to support a drill bit and another end adapted to be driven by the rotary shaft of a well drilling fluid actuated downhole motor when assembled thereon, upper and lower thrust bearings positioned around said bearing shaft within said bearing pack housing to support said bearing shaft against oppositely directed vertically acting forces, said upper thrust bearing supporting said bearing shaft against upward thrust during drilling operation, said lower thrust bearing supporting downward thrust of said bearing shaft when lifted out of drilling operation, and means to cause said lower thrust bearing to support said bearing shaft during drilling operation upon change in pressure drop of drilling fluid in said downhole drilling motor.

13. A downhole well drilling tool according to Claim 5, Claim 7 or Claim 8 in which said shaft rotating means is a turbine comprising a plurality of stator blades fixed in said housing means, a rotor shaft rotatably supported in said housing means, a plurality of rotor blades supported on said rotor shaft and cooperable with fluid flowing through said stator blades to effect rotation of said rotor shaft, and means operatively connecting said rotor shaft to said first named rotary shaft for effecting rotation thereof.

14. A downhole well drilling tool according to Claim 9, Claim 10 or Claim 11 in which said shaft rotating means is a turbine comprising a plurality of stator blades fixed in said housing means, a rotor shaft rotatably supported in said housing means, a plurality of rotor blades supported on said rotor shaft and cooperable with fluid flowing through said stator blades to effect rotation of said rotor shaft, and means operatively connecting said rotor shaft to said first named rotary shaft for effecting rotation thereof.

15. A downhole well drilling tool according to Claim 12 in which said downhole motor is a turbine comprising a plurality of stator blades fixed in said motor housing, a rotor shaft rotatably supported in said motor housing, a plurality of rotor blades supported on said rotor shaft and cooperable with fluid flowing through said stator blades to effect rotation of said rotor shaft, and means operatively connecting said rotor shaft to said first named rotary shaft for effecting rotation thereof.