Abstract:
A mud motor bearing assembly for use in drilling a hydrocarbon well. The bearing assembly includes a bearing section containing stationary bearing rigs and rotating bearing rings in stacked arrangement. The bearing rings have wedge-shaped projections. The wedge-shaped projections of two adjacent stationary bearing rings form a recess to accommodate the projection of a rotating bearing ring in sliding engagement. The bearing assembly is capable of bearing both radial and axial loads.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of and claims the benefit of and priority to U.S. patent application Ser. No. 13/469,818, filed on May 11, 2012, which is incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a mud motor bearing assembly and method for drilling hydrocarbon wells and more particularly to a mud motor bearing assembly and method containing a bearing section capable of bearing both radial and axial loads. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the drilling of oil and gas wells, a mud motor may be used for drilling tasks such as straight hole, horizontal, directional and short radius drilling. Mud motors are connected to the drill string to rotate and steer the drill bit. Mud motors typically include a power section and a bearing assembly. Rotation is provided by the power section that may be a positive displacement motor driven by drilling fluid (mud) circulation. The bearing assembly takes up the axial and radial loads imparted on the drill string during drilling. 
         [0004]    The power section of conventional mud motors has a transmission housing, a stator secured within the transmission housing, and a rotor rotatable within the stator. The stator may have a helically contoured inner surface. The rotor may have a helically contoured outer surface. Together, they define a positive displacement fluid pump having a helically shaped progressive cavity. 
         [0005]    The bearing assembly of typical mud motors is threadedly connected to the power section. The bearing assembly includes a bearing housing, a rotatable drive shaft secured within the bearing housing for coupling the rotor to the drill bit, and a transmission shaft for connecting the rotor to the drive shaft. The drive shaft extends downwardly through the bearing housing and is supported within the bearing housing by multiple sets of bearings. The drive shaft is fitted with the drill bit at its lower end. 
         [0006]    Drilling fluid or mud is pumped from the well surface through the drill string or drill pipe to the mud motor. The drilling fluid or mud flows through the cavity formed between the rotor and the stator, through the portion of the transmission housing surrounding the transmission shaft, into the inlet ports provided on the drive shaft, through the drive shaft, and out through the outlet port to flush cuttings from the borehole and cool the drill bit. The drilling fluid drives the rotor to rotate within the stator, with the rotor orbiting around the inner surface of the stator. The transmission shaft transmits the rotational movements of rotor to the drive shaft. The drive shaft rotates concentrically within the bearing housing to drive the drill bit. 
         [0007]    If the drill bit is not in contact with the bottom of the borehole, the high pressure drilling fluid applied through the drill pipe to the mud motor exerts a downwardly-directed axial thrust load to the rotor, transmission shaft, drive shaft and drill bit relative to the bearing housing. This is referred to as an off-bottom thrust load. When the drill bit is brought into contact with the bottom of the borehole, the weight of the entire drill string is imposed on the drill bit. As a result, an upwardly-directed axial thrust load is exerted on the drill bit and drive shaft. This is referred to as an on-bottom thrust load. 
         [0008]    Conventional mud motors use a combination of radial bearings and thrust bearings in order to restrict the radial and axial movement of the motor&#39;s drive shaft. A cross-sectional view of a typical prior art bearing assembly  1  is shown in  FIGS. 1A and 1B . Conventional bearing assembly  1  contains three sets of bearings: upper radial bearings  2 ; thrust or axial bearings  3 ; and lower radial bearings  4 . 
         [0009]    Common radial bearings used in downhole drilling applications are journal bearings, also known as sleeve bearings. A journal bearing is formed from a plain cylindrical sleeve that carries a rotating shaft. Sometimes, journal bearings are also referred to as fluid film bearings because of the presence of a thin film of lubricant formed between the cylindrical sleeve and the rotating shaft. The coefficient of friction experienced by the rotating shaft is dependent, in large part, on whether a fluid film is fully developed. In essence, a fully developed fluid film creates a hydrodynamic pressure sufficient to float the shaft and its respective load relative to the sleeve or journal. The result of a fully developed fluid film is that there is no physical contact between the rotating shaft and the journal during operation. Proper development of a fluid film is generally dependent on adequate lubrication of the bearing journal. 
         [0010]    Rolling element-type bearings, such as ball rollers or angular contact rollers, are often used as thrust bearings. U.S. Pat. No. 5,074,681 to Turner et al. discloses an example of ball rollers. U.S. Pat. No. 5,248,204 to Livingston et al. discloses an example of angular contact rollers. Typically, these rolling element-type bearings are lubricated by the drilling fluid (mud) or by clean oil when encased in a sealed oil chamber. Rolling element-type bearings are not tolerant of abrasives and thus wear quickly when exposed to mud lubrication. Once wear occurs, loads between the individual balls become uneven and wear rates accelerate. For the oil-lubricated bearings, once the seals fail, wear occurs in a similar way. Due to the high loads, pressure, and abrasive conditions, bearing life is typically only several hundred hours. 
         [0011]    Another type of thrust bearing used in downhole drilling motors is a hydrodynamic or sliding surface type. U.S. Pat. No. 4,560,014 to Geczy discloses an example of this hydrodynamic bearing type, which uses rigidly mounted pads manufactured of industrial diamond. The diamond pads are mud-lubricated and slide against each other. These bearings, however, are extremely expensive and only marginally increase service life. 
         [0012]    Bearings in the bearing assembly are exposed to harsh conditions. The bearings are subjected to extreme forces and loads. The bearings also encounter abrasives contained within the drilling mud or other lubricants. Bearings have a limited service life due to operational conditions, regardless of the type of thrust bearings used. Failure of the bearings often results in the thrust load being absorbed by the bearing housing as it contacts the drill shaft. Such metal-on-metal contact causes degradation of the bearing housing. Therefore, when the bearings fail, the entire drill string must be removed from the wellbore so that the mud motor can be replaced. The cost to repair and maintain conventional mud motors is significant. Typical mud motors contain numerous components requiring a skilled technician to undertake the repairs. The mud motors may be out of service for extended periods due to the number of components that must be examined or replaced. 
       SUMMARY OF THE INVENTION 
       [0013]    It is an object of the present invention to provide a mud motor bearing assembly that is economical to construct. 
         [0014]    It is a further object of the present invention to provide a mud motor bearing assembly that has a simplified design. 
         [0015]    It is a further object of the present invention to provide a mud motor bearing assembly with a reduced number of components. 
         [0016]    It is a further object of the present invention to provide a mud motor bearing assembly having one bearing section. 
         [0017]    It is a further object of the present invention to provide a mud motor bearing assembly having one bearing section capable of bearing both axial and radial loads. 
         [0018]    These and other objects and advantages are achieved by a novel mud motor bearing assembly of the present invention. The bearing assembly may include a stationary housing, a rotatable drive shaft extending through the housing, and a bearing section. The bearing section may include a first stationary bearing ring having an inner periphery and an outer periphery. The outer periphery of the first stationary bearing ring may be operatively engaged to the stationary housing. The inner periphery of the first stationary bearing ring may include a projection. The bearing section may also include a second stationary bearing ring having an inner periphery and an outer periphery. The outer periphery of the second stationary bearing ring may be operatively engaged to the stationary housing. The inner periphery of the second stationary bearing ring may include a projection. The bearing section may also include a rotating bearing ring having an inner periphery and an outer periphery. The inner periphery of the rotating bearing ring may be operatively engaged to the drive shaft. The outer periphery of the rotating bearing ring may include a projection. The rotating bearing ring may be disposed between the first stationary bearing ring and the second stationary bearing ring such that the projection of the rotating bearing ring is slidably engaged with the projections of the first and second stationary bearing rings. 
         [0019]    The projections of the rotating bearing ring and the first and second stationary bearing rings may be wedge-shaped. The projections of the rotating bearing ring and the first and second stationary bearing rings may also comprise a wear resistant face. 
         [0020]    The wedge-shaped projections of the rotating bearing rings and the stationary bearing rings may each include two side walls. Each side wall may contain a recess for accommodation of a bearing ball. The bearing section may include at least one bearing ball rotatably contained between adjacent side walls of the rotating and stationary bearing rings within the recesses therein. 
         [0021]    The wedge-shaped projections of the rotating bearing rings and the stationary bearing rings may also each include two side walls. Each side wall may contain a wear insert positioned within a recess therein. 
         [0022]    Another embodiment of the mud motor bearing assembly of the present invention may include a stationary housing having an inner wall surface defining an interior bore. The bearing assembly may also include a rotatable drive shaft extending through the interior bore of the stationary housing. The rotatable drive shaft may have a tubular drive shaft with a uniform outer diameter terminating at an outlet section with an enlarged outer diameter. The rotatable drive shaft may include a inner bore for passage of drilling fluid. The bearing assembly may also have a bearing section bearing a radial load and an axial load. The bearing section may include at least a pair of stationary bearing rings and at least a pair of rotating bearing rings in stacked arrangement. Each of the stationary bearing rings may have an inner periphery and an outer periphery. The outer periphery of each of the stationary bearing rings may be operatively engaged to the inner wall of the stationary housing. The inner periphery of each of the stationary bearing rings may include a projection. Each of the rotating bearing rings may have an inner periphery and an outer periphery. The inner periphery of each of the rotating bearing rings may be operatively engaged to the tubular drive shaft. The outer periphery of each of the rotating bearing rings may include a projection. The projections of the pair of stationary bearing rings may form a recess that accommodates the projection of one of the pair of rotating bearing rings in sliding engagement. 
         [0023]    The projections of the pair of stationary bearing rings of this embodiment may be wedge-shaped. The projections of the pair of rotating bearing rings may also be wedge-shaped. 
         [0024]    In the embodiment, the bearing section may contain 3 to 6 pairs of stationary bearing rings and rotating bearing rings. The bearing section may contain 6 pairs of stationary and rotating bearing rings. 
         [0025]    Also in this embodiment, the projections of the pair of stationary bearing rings and the projections of the pair of rotating bearing rings may include a wear-resistant face. The wedge-shaped projections of the rotating bearing rings and the stationary bearing rings may each be comprised of two side walls. Each side wall may contain a recess for accommodation of a bearing ball. The bearing section may include at least one bearing ball rotatably contained between adjacent side walls of the rotating and stationary bearing rings within the recesses therein. The wedge-shaped projections of the rotating bearing rings and the stationary bearing rings may also be each comprised of two side walls with each side wall containing a wear insert positioned within a recess therein. 
         [0026]    In the embodiment, an upper end of the stationary housing may be detachably connected to a transmission housing having an inner wall surface defining an interior bore. The bearing section may surround the tubular drive shaft. 
         [0027]    Also in this embodiment, the bearing assembly may include an adaptor having an upper section and a lower section. The lower section of the adaptor may be operatively connected to an upper end of the tubular drive shaft. The upper section of the adaptor may be detachably connected to a transmission shaft. The adaptor may have one or more inlet ports for passage of the drilling fluid from the interior bore of the transmission housing to the inner bore of the rotatable drive shaft. The bearing assembly may also include a channel for passage of the drilling fluid to the bearing section. The channel may be formed by an outer surface of the adaptor and an inner surface of the transmission housing. 
         [0028]    The bearing assembly may further include a spacer containing the bearing section within the bearing assembly. The spacer may comprise an outer spacer held in position by the transmission housing and an inner spacer held in position by the outer spacer. 
         [0029]    The bearing assembly may also include a drill bit assembly operatively connected to the outlet section of the rotatable drive shaft. 
         [0030]    The present invention is also directed to a method of drilling a hydrocarbon well. The method may include the step of providing a mud motor assembly on a drill string. The mud motor assembly may comprise: a stationary housing having an inner wall surface defining an interior bore; a rotatable drive shaft extending through the interior bore of the stationary housing, the rotatable drive shaft having a tubular drive shaft with a uniform outer diameter terminating at an outlet section having an enlarged outer diameter, the rotatable drive shaft including a inner bore for passage of a drilling fluid; a bearing assembly including a bearing section bearing a radial load and an axial load, the bearing section including at least a pair of stationary bearing rings and at least a pair of rotating bearing rings in stacked arrangement, each of the stationary bearing rings having an inner periphery and an outer periphery, the outer periphery of each of the stationary bearing rings operative engaged to the inner wall of the stationary housing, the inner periphery of each of the stationary bearing rings including a projection, each of the rotating bearing rings having an inner periphery and an outer periphery, the inner periphery of each of the rotating bearing rings operatively engaged to the tubular drive shaft, the outer periphery of each of the rotating bearing rings including a projection, the projections of the pair of stationary bearing rings forming a recess that accommodates the projection of one of the pair of rotating bearing rings in sliding engagement; and a drill bit assembly operatively connected to the outlet section of the rotatable drive shaft. The method may also include the step of running the mud motor assembly downhole to a position where drilling is desired. The method include the step of pumping a drilling fluid from a surface of the hydrocarbon well through the drill string to the mud motor assembly to actuate a rotation of the rotatable drive shaft and the drill bit assembly operatively connected thereto. The method includes the step of permitting the bearing section to bear a radial load caused by rotation of the rotatable shaft and an axial load caused by the pumping of the drilling fluid or by a weight of the drill string. 
         [0031]    The method may further comprise the step of channeling a portion of the drilling fluid to the bearing section to form a hydrodynamic fluid film therein. 
         [0032]    In the method of the present invention, the bearing section may contain 3 to 6 pairs of stationary bearing rings and rotating bearing rings. The projections of the pair of stationary bearing rings and the projections of the pair of rotating bearing rings may include a wear-resistant face or wear insert. 
         [0033]    The many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims and the following detailed description of the preferred embodiments and read in conjunction with the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIGS. 1A and 1B  are a sequential cross-sectional view of a prior-art bearing assembly. 
           [0035]      FIGS. 2A and 2B  are a sequential cross-sectional view of an embodiment of the bearing assembly of the present invention. 
           [0036]      FIG. 3  is a partial cross-sectional view of the bearing assembly shown in  FIG. 2A . 
           [0037]      FIG. 4  is a partial cross-sectional view of an alternative embodiment of the bearing assembly of the present invention. 
           [0038]      FIG. 5  is a partial cross-sectional view of a first alternative embodiment of the bearing assembly of the present invention. 
           [0039]      FIG. 6  is a partial cross-sectional view of a second alternative embodiment of the bearing assembly of the present invention. 
           [0040]      FIG. 7  is partial cross-sectional view of a third alternative embodiment of the bearing assembly of the present invention. 
           [0041]      FIG. 8  is schematic view of an alternative hydrodynamic bearing ring that could be used in the bearing assembly of the present invention. 
           [0042]      FIG. 9  is a schematic representation of the bearing assembly of the present invention of  FIG. 2  on a drill string. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0043]    With reference to the figures where like elements have been given like numerical designation to facilitate an understanding of the present invention, and particularly with reference to the embodiment of the present invention illustrated in  FIGS. 2A and 2B , bearing assembly  10  is shown threadedly connected to transmission housing  12  and supporting drive shaft  14 , which is threadedly connected to adapter  16  which in turn is threadedly connected to transmission shaft  18 . Bearing assembly  10  restricts both the radial movement and axial movement of drive shaft  14 . 
         [0044]    With reference to  FIGS. 2A and 2B , bearing assembly  10  includes bearing housing  20 . Bearing housing  20  has upper end  22  and lower end  24 . Bearing housing also has outer surface  26  and inner surface  28 . Threads  30  contained in inner surface  28  of upper end  22  cooperate with corresponding threads  32  on outer surface  34  of transmission housing  12  to detachably or threadedly connect bearing assembly  10  to transmission housing  12 . 
         [0045]    As seen in  FIGS. 2A, 2B, and 3 , bearing assembly  10  includes bearing section  36 . Bearing section  36  may include stacked or cooperating bearing rings in series. Each series includes first stationary bearing ring  38 , second stationary bearing ring  38 , and rotating bearing ring  40 . Stationary bearing rings  38  each have inner periphery  42  and outer periphery  44 . Outer periphery  44  of each stationary bearing ring  38  may be affixed to inner surface  28  of bearing housing  20  such that stationary bearing rings  38  are prevented from rotating relative to bearing housing  20 . Stationary bearing rings  38  may be affixed to inner surface  28  of bearing housing  20  by various methods such as by a weld, a pin, a brace, a bolt, or a screw. Stationary bearing rings  38  could also be made integral with bearing housing  20 . Inner periphery  42  of each stationary bearing ring  38  has outwardly extending projection  46 . Outwardly extending projection  46  may be wedge-shaped. Stationary bearing rings  38  are secured to or by bearing housing  20  by friction due to holding the rings in compression or by splines, keys, or other similar arrangement. 
         [0046]      FIGS. 2A, 2B, and 3  also show that each rotating bearing ring  40  has inner periphery  48  and outer periphery  50 . Inner periphery  48  may be operatively engaged or connected to outer surface  52  of drive shaft  14  such that rotating bearing rings  40  rotate with the rotation of drive shaft  14 . Rotating bearing rings  40  may be operatively connected to drive shaft  14  by a variety of methods including by a pin, a bolt, or a screw. Outer periphery  50  of each rotating bearing ring  40  has outwardly extending projection  54 . Outwardly extending projection  54  may be wedge-shaped. Rotating bearing rings  40  are secured to or by drive shaft  14  by friction due to holding the rings in compression or by splines, keys, or other similar arrangement. 
         [0047]    With reference to  FIGS. 2A, 2B and 3 , first stationary bearing ring  38 , rotating bearing ring  40 , and second stationary bearing ring  38  are in a stacked arrangement within bearing housing  20 . Rotating bearing ring  40  is disposed between first stationary bearing ring  38  and second stationary bearing ring  38 . Outwardly extending projection  54  of rotating bearing ring  40  slidably engages outwardly extending projections  46  of first and second stationary bearing rings  38  as drive shaft  14  rotates within bearing housing  20 . 
         [0048]    Again with reference to  FIGS. 2A and 3 , bearing means  36  may be supported within bearing housing  20  by shoulder  56  in lower end  24  of bearing housing  20  and by adapter  16  and transmission housing  12  via inner spacer  58  and outer spacer  60 . 
         [0049]      FIG. 4  depicts an alternative bearing section  36 . In the alternative bearing section  36 , sides  62  of outwardly extending projections  46  of stationary bearing rings  38  and sides  64  of outwardly extending projections  54  of rotating bearing rings  40  each have recess  66  that accommodates bearing ball  68 . When first stationary bearing ring  38 , rotating bearing ring  40 , and second stationary bearing ring  38  are in a stacked arrangement within bearing housing  20 , rotating bearing ring  40  is disposed between first stationary bearing ring  38  and second stationary bearing ring  38 . A first ball bearing  68  is situated in recesses  66  of and between first stationary bearing ring  38  and rotating bearing ring  40 . A second ball bearing  68  is situated in recesses  66  of and between second stationary bearing ring  38  and rotating bearing ring  40 . Outwardly extending projection  54  of rotating bearing ring  40  slidably engages outwardly extending projections  46  of first and second stationary bearing rings  38  as drive shaft  14  rotates within bearing housing  20 . Ball bearings  68  rotate within recesses  66  as rotating bearing ring  40  slidably engages outwardly extending projections  46  of first and second stationary bearing rings  38  as drive shaft  14  rotates within bearing housing  20 . Ball bearings  68  function to enhance the sliding engagement of bearing rings  38 ,  40  and to take up wear that otherwise would be incurred by bearing rings  38 ,  40 . Gap  70  provides a separation between stationary bearing rings  38  and rotating bearing rings  40  through which drilling fluid, mud, or other lubricant can travel, thereby coating the rings  38 ,  40 . The coating cools bearing rings  38 ,  40  during rotation to lessen their wear. 
         [0050]      FIG. 5  shows another alternative bearing section  36 . Recesses  66  in sides  62 ,  64  of respective stationary and rotating bearing rings  38 ,  40  includes inserts  72 . Inserts  72  in opposing sides  62 ,  64  of respective stationary bearing rings  38  and rotating bearing rings  40  are in cooperative engagement such that during rotation of rotating bearing rings  40 , opposing or adjacent inserts  72  are in sliding engagement and take up wear. Gaps  70  provide a pathway for drilling fluid, mud, or lubricant to cool bearing rings  38 ,  40  and inserts  72  to lessen wear. Inserts  72  could be made in a variety of shapes. 
         [0051]      FIG. 5  shows insert  72  as being substantially rectangular-shaped. 
         [0052]      FIG. 6  shows insert  72  as being substantially triangular-shaped. 
         [0053]      FIG. 7  shows another alternative bearing section  36 . Sides  62 ,  64  of respective stationary and rotating bearing rings  38 ,  40  contain insert  72  affixed thereon rather than housed in a recess. Insert  72  may be affixed to stationary and rotating bearing rings by a variety of methods such as by a weld, a pin, screwed, or bolted. Insert  72  could also be made integral with bearing rings  38 ,  40 . 
         [0054]    Stationary bearing rings  38  and rotating bearing rings  40  may be made of hardened material such as heat-treated metal, carbide steel, copper, or a metal alloy. Ball bearings  68  and inserts  72  may be made of hardened material such as heat-treated metal, carbide steel, copper, metal alloy, ceramics, wood or elastomeric plastic. 
         [0055]      FIG. 8  shows a further alternative bearing section  36 . Bearing section  36  may include one or more hydraulic bearings  74 . Bearing  74  may be a one-piece thrust bearing that uses geometry-induced hydrodynamic lubrication to support heavy thrust loads on a lubricant film. Bearing  74  tolerates high impact loads without performance degradation and reduces friction which permits higher load/speed combinations, cooler operation and extended operational life. Bearing  74  is commercially available from Kalsi Engineering under the model name Kalsi Bearing. 
         [0056]    As seen in  FIGS. 2A, 2B and 9 , pressurized drilling fluid or mud is pumped from well surface  76 , through drill string  78 , and to mud motor  80  in wellbore  81 . The fluid or mud travels through the interior of transmission housing  12  to adaptor  16 . The fluid or mud may passes through conduits  82  in adaptor  16  and down through the inner bore of drive shaft  14  and to drill bit  84  to actuate drill bit  84 . Some of the drilling fluid or mud is diverted into channel  86  and flows through bearing section  36  to lubricate and cool stationary and rotating bearing rings  38 ,  40 . Additionally, as rotation commences, the drilling fluid is distributed across the faces of bearing ring outwardly extending projections  46 ,  54 , resulting in the formation of a hydrodynamic fluid film within bearing section  36 . Excess drilling fluid may be discharged from bearing assembly  10  through outlet channel  88  in lower end  24  of bearing housing  20 . In an embodiment, the bearing ring projections  46 ,  54  may have one or more grooves on their faces in order to facilitate the flow of drilling fluid through bearing section  36 . Gaps  70  between the opposing faces of projections  46 ,  54  also promote the flow of the drilling fluid or mud throughout bearing section  36 . 
         [0057]    When drive shaft  14  is first rotated, metal-on-metal contact may occur between stationary bearing rings  38  and rotating bearing rings  40 . Additionally, the drilling fluid flowing within bearing section  36  typically contains highly abrasive particles. In light of this operating environment, the faces of bearing ring outwardly extending projections  46 ,  54  can have wear resistant inserts to prevent premature bearing failure such as inserts  72  mentioned herein. The wear resistant inserts can be constructed out of tungsten carbide, silicon carbide, and other metals having sufficient hardness. 
         [0058]    Thrust bearing section  36  absorbs hydraulic loading from the motor and mechanical loads imposed during drilling operations. As shown in  FIGS. 2A and 2B , bearing section  36  may have a plurality of stationary bearing rings  38  longitudinally stacked within bearing housing  20 , with a plurality of rotating bearing rings  40  disposed between stationary bearing rings  38 . In this stacked arrangement or configuration, the thrust load is evenly dispersed across the face of the bearing ring projections  46 ,  54 . As each additional bearing ring  38 ,  40  is added to bearing section  36 , additional surface area is available to disperse the thrust load. Accordingly, the thrust load on any given bearing ring  38 ,  40  is inversely proportional to the number of bearing rings  38 ,  40  in bearing section  36 . 
         [0059]    Bearing section  36  of the present invention is double acting. Bearing rings  38 ,  40  are in sliding contact between adjacent rings  38 ,  40 . Thrust loading is distributed throughout the bearing rings  38 ,  40 . Thrust loading is evenly split through the number of rings  38 ,  40  comprising bearing section  36 . Maximum axial wear of bearing rings  38 ,  40  is determinative of the maximum axial play of the bearings. 
         [0060]    The mud motor and/or bearing assembly  10  of the present invention contains fewer operational components than conventional mud motors. For example, bearing section  36  eliminates the need for bearing assembly  10  to contain upper radial and lower radial bearings. The mud motor and/or bearing assembly  10  of the present invention has less connections and more standard connections than conventional mud motors. No special maintenance tools are required for the present invention. Accordingly, the mud motor and/or bearing assembly  10  of the present invention is more economical to manufacture and operate. Furthermore, bearing section  36  of the present invention is more reliable and less prone to wear than conventional mud motors and bearing assemblies. 
         [0061]    While preferred embodiments of the present invention have been described, it is to be understood that the embodiments described are illustrative only and that the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalents in view of the many variations and modifications naturally occurring to those skilled in the art from a perusal hereof.