Patent Publication Number: US-9840871-B2

Title: Downhole mud motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Patent Application No. 62/088,935, filed on Dec. 8, 2014, entitled “DOWNHOLE MUD MOTOR”, which is incorporated by reference herein. An application data sheet containing this priority claim is submitted herewith. 
    
    
     BACKGROUND 
     Field of the Disclosure 
     The present disclosure relates to downhole drilling operations and, more particularly, to a mud motor for downhole drilling. 
     Description of the Related Art 
     Columns or strings of pipe referred to as drill strings are used to transmit drilling fluid and torque to a drill bit used to drill a well hole. Drill strings are hollow so that drilling fluid may be pumped down through the drill string and circulated back to the top, including by way of the void that is between the outer casing of the drill string and the hole in which the drill string is inserted. Mud motors (also referred to as drilling motors) may be included in the drill string and may be used to provide additional rotational power to the drill bit while drilling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an image showing selected elements of an embodiment of a mud motor; 
         FIG. 2  is a cross-sectional image of the mud motor of  FIG. 1 ; and 
         FIG. 3  is an image showing further detail of the mud motor of  FIG. 1 . 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following description, details are set forth by way of example to facilitate discussion of the disclosed subject matter. It should be apparent to a person of ordinary skill in the field, however, that the disclosed embodiments are exemplary and not exhaustive of all possible embodiments. 
     Disclosed herein is a mud motor. In one embodiment, the mud motor includes a rotor head, a motor block, a hollow rotor, an inlet shaft, and an outlet shaft. In the operation of one embodiment, a pressurized drilling mud enters the rotor head through the inlet shaft and is directed through an inlet passage in the rotor head into the motor block. In at least one embodiment, the motor block includes a plurality of pistons axially aligned within cylinder bores concentrically disposed around the outlet shaft and the outlet shaft is substantially centrally positioned within the mud motor. A power plate is located below the pistons in at least one embodiment and the power plate has a centrally located circular opening configured to encompass the outlet shaft, encompasses the outlet shaft with an inclined orientation thereto, and is configured to rotate around the outlet shaft and within the motor block. In at least one embodiment, the motor block includes the power plate and the power plate rotates within the motor block. 
     In at least one embodiment, the outlet shaft vertically extends from the bottom of the rotor head to the bottom of the mud motor and passes through the circular opening of the power plate. In such an embodiment, a hollow rotor that rotates within the outlet shaft is centrally disposed within the outlet shaft and the hollow rotor extends from the rotor head, passes through the motor block and the power plate, and terminates at or below the mud motor. The hollow rotor may be fixedly attached to both the rotor head and the power plate in at least one embodiment. In the operation of at least one embodiment, upon entering the motor block, the drilling mud is directed to sequentially push each of the pistons down upon the angled power plate. The resulting action causes the power plate to rotate. During the rotation of the power plate, the angled orientation of the power plate causes the power plate to sequentially push some or all of the downwardly extended pistons up, thereby expelling some or all of the drilling mud that pushed the pistons down. The drilling mud is expelled from at least one of the pistons by directing it to the hollow rotor through a discharge passage in the rotor head that leads into the hollow rotor. As a result, some or all of the drilling mud that enters the mud motor in such embodiments is discharged from the mud motor through the hollow rotor. The discharge of the drilling mud may occur at the bottom of the mud motor. Because the hollow rotor is fixedly attached to both the power plate and the rotor head, the rotation of the power plate causes the hollow rotor and the rotor head to both rotate as well. The pistons, however, do not rotate around the outlet shaft in such embodiments, but instead substantially remain in their original concentric alignment. In at least one embodiment, the rotation of the rotor head maintains both (i) the timing of the inlet passage in relation to the position of the pistons so that the pressurized drilling mud is sequentially directed through the inlet passage to some or all of the pistons that have been pushed up by the power plate so as to cause the downward stroke of each such piston and (ii) the timing of the discharge passage so that the pressurized drilling mud is directed through the discharge passage out of the motor block and into the hollow rotor from some or all of the pistons during their upward stroke caused by the power plate. 
     In this way the drilling mud is directed by the rotor head, in at least one embodiment, to sequentially push some or all of the pistons down onto the power plate and the resulting action causes the power plate to rotate and the rotation of the angled power plate sequentially pushes some or all of the downwardly extended or substantially downwardly extended pistons up, with some or all of the drilling mud being directed from the pistons during their upward stroke out of the motor block and into the hollow rotor. The process repeats itself such that the power plate, the hollow rotor, and the rotor head may remain in substantially continuous rotation while the pressurized drilling mud is directed into and out of the motor block. In some embodiments, the end of the hollow rotor may be connected to a drill bit and thereby add to the torque and rotation of the drill bit during the operation of the mud motor. 
     In one embodiment, a mud motor includes an inlet shaft, a rotor head, a motor block, an outlet shaft, and a power plate. In at least one embodiment, the inlet shaft is disposed at a top end of the mud motor and the motor block includes a plurality of cylinder bores concentrically disposed around the outlet shaft with each cylinder bore including a piston configured to reciprocate within the cylinder bore. In at least one embodiment, the rotor head is rotatably attached at a first end to the inlet shaft and fixedly attached at a second end to a hollow rotor and the rotor head is configured to rotate within the mud motor and to redirect a fluid received via the inlet shaft into and out of the motor block upon rotation. The hollow rotor may, in at least one embodiment, be centrally disposed within the outlet shaft and the outlet shaft may extend from the second end of the rotor head to a bottom end of the mud motor. 
     In at least one embodiment, the power plate is fixedly attached to the hollow rotor at an angle, disposed at a lower portion of the motor block, and may rotate within the motor block. The attachment of the power plate to the hollow rotor may be accomplished with a timing pin or bolt. The power plate may support a driving end of each of the pistons such that in operation, when a piston is driven against the power plate by the fluid redirected by the rotor head to the motor block, the power plate rotates. In at least one embodiment, the rotation of the power plate in turn causes the hollow rotor affixed to the power plate to rotate which in turn causes the rotor head affixed to the hollow rotor to rotate as well. 
     In at least one embodiment, the cylinder bores remain substantially stationary with respect to their concentrical alignment around the outlet shaft during operation of the mud motor. In at least one embodiment, the rotor head includes an inlet passage that directs some or all of the fluid into the motor block and a discharge passage that directs the fluid out of the motor block and into the hollow rotor. In at least one embodiment, the inlet passage sequentially directs the fluid received from the inlet passage to some or all of the pistons to cause a downward movement of some or all of the pistons and the discharge passage directs some or all of the fluid ejected by some or all of the pistons to the hollow rotor when the rotation of the power plate pushes some or all of the downwardly extended pistons to a non-extended position such that some or all of the fluid within the corresponding cylinder bores is ejected by the pistons during their upward movement. 
     In some embodiments, the mud motor includes a motor block, a rotor head, and a power plate. In at least one of these embodiments, the mud motor may include a plurality of cylinder bores concentrically disposed around an outlet shaft and each of the cylinder bores includes a piston configured to reciprocate within the cylinder bore. The rotor head in some of these embodiments may be attached to a hollow rotor, which may be centrally disposed within the mud motor, and the rotor head may be configured to rotate within the mud motor and to redirect a fluid received into the mud motor to and from the motor block upon rotation. The power plate in at least one of these embodiments may support a driving end of each of the pistons and may be fixedly attached at an angle to the hollow rotor and disposed below the motor block. In other of these embodiments, the power plate may support a driving end of at least one of the pistons. In these embodiments, a piston driven against the power plate by the fluid redirected by the rotor head to the motor block may cause the power plate, the hollow rotor, and the rotor head to rotate and during such operation of the mud motor, the cylinder bores may remain substantially stationary with respect to their concentrical alignment around the outlet shaft. In some of these embodiments, the rotor head includes an inlet passage and the inlet passage directs the fluid to at least one of the pistons. In at least one of these embodiments, the rotor head includes a discharge passage and the discharge passage receives the fluid expelled from at least one of the pistons and directs the expelled fluid to the hollow rotor. 
     The mud motor may, in some embodiments, further include a flow bypass valve or jet. The flow bypass jet may be included within the rotor head and may direct all or a portion of the fluid from the inlet shaft to the hollow rotor so as to bypass the pistons. The flow bypass jet may be adjustable with respect to the amount of fluid that is directed by the flow bypass jet to the hollow rotor and thereby control a rotational speed of the mud motor. 
     Throughout this disclosure, a hyphenated form of a reference numeral refers to a specific instance of an element and the un-hyphenated form of the reference numeral refers to the element generically or collectively. Thus, widget  12 - 1  refers to an instance of a widget class, which may be referred to collectively as widgets  12  and any one of which may be referred to generically as a widget  12 . 
     Referring first to  FIG. 1 , an image showing selected elements of an embodiment of mud motor  100  is depicted. In the depicted embodiment, mud motor  100  includes inlet shaft  105  and hollow rotor  115 . Hollow rotor  115 , as depicted in more detail in  FIG. 2 , passes through a lower end  110  of mud motor  100 . When in operation, a pressurized fluid, which may be or which may include drilling mud, may enter inlet shaft  105  and, as is depicted in more detail in  FIG. 2 , may be sequentially directed by rotor head  220  to pistons  225  which, by way of power plate  230 , cause hollow rotor  115  and rotor head  220  to both rotate. The pressurized fluid may exit mud motor  100  by way of hollow rotor  115 . 
     Turning now to  FIG. 2 , an image showing selected elements of an embodiment of mud motor  100  is depicted. In the depicted embodiment, mud motor  100  includes inlet shaft  105 , rotor head  220 , motor block  240 , and outlet shaft  250 . In one embodiment, rotor head  220  may be rotatably coupled to inlet shaft  105  at one end of rotor head  220  and may be fixedly coupled to hollow rotor  115  at an opposite end of rotor head  220  such that rotor head  220  rotates about inlet shaft  105 . 
     In the depicted embodiment, motor block  240  includes a plurality of pistons  225 , a plurality of cylinder bores  260 , and power plate  230 . In the depicted embodiment, rotor head  220  is adjacent to motor block  240  and axially aligned with pistons  225 , and pistons  225  are disposed concentrically around outlet shaft  250 . In one embodiment, pistons  225  are disposed concentrically around outlet shaft  250  within cylinder bores  260  and fixedly attached within motor block  240  so that pistons  225  move in an upward and downward manner within their respective cylinder bores, but do not revolve in a rotational direction about outlet shaft  250  during operation of mud motor  100 . In one embodiment, mud motor  100  includes six of pistons  225  disposed concentrically around outlet shaft  250 . 
     Pistons  225 , in the depicted embodiment, include driving ends  226  which are configured to slidably engage with the upper face of power plate  230 . In one embodiment, power plate  230  has a centrally located circular opening and is configured to rotate inside outlet shaft  250 , and outlet shaft  250  vertically extends from the bottom of rotor head  220  to a bottom end  110  of mud motor  100  and is configured to receive power plate  230 . Hollow rotor  115  is centrally disposed within outlet shaft  250  in the depicted embodiment and may extend from rotor head  220 , pass through motor block  240  and the opening of power plate  230 , and terminate at, below, or near bottom end  110  of mud motor  100 . In at least one embodiment, hollow rotor  115  is fixedly attached to both rotor head  220  and power plate  230  such that the rotation of power plate  230  causes a corresponding rotation of hollow rotor  115  and rotor head  220 . 
     Turning now to  FIG. 3 , selected elements of rotor head  220  are illustrated. Rotor head  220  may include inlet passage  305 , discharge passage  310 , and flow bypass jet or valve  315 . In the depicted embodiment, inlet passage  305  is configured to receive inlet shaft  105  at inlet passage port  300  and further configured to direct pressurized fluid received via inlet shaft  105  via inlet passage port  300  into motor block  240  and onto some or all of pistons  225  when pistons  225  are at their substantially upward or non-extended position (or have reached their apex of travel upward by the rotation of power plate  230 ). In the depicted embodiment, the base of inlet passage  305  is exposed to a plurality of pistons  225  that are adjacent to one another. In at least one embodiment, the base of inlet passage  305  is exposed to half of the total number of concentrically disposed pistons  225  with some or all of such pistons  225  to which the base of inlet passage  305  is exposed occupying a position within their respective cylinder bores  260  which is just after apex of travel to just before base of travel for pistons  225 . In the depicted embodiment, discharge passage  310  is exposed to a plurality of pistons  225  that are adjacent to one another and is configured to direct some or all of the fluid that is expelled from pistons  225  during their upward travel to hollow rotor  115 . As depicted in  FIG. 2 , it will be appreciated that while all of pistons  225  will, at some time during the operation of mud motor  100 , be exposed to both inlet passage  305  and discharge passage  310 , such exposure will occur in a sequential, not simultaneous manner. In other embodiments, at least one of pistons  225  may be exposed simultaneously to both inlet passage  305  and discharge passage  310  during the operation of mud motor  100 . 
     In a preferred embodiment, inlet passage port  300  is rotatably attached to inlet shaft  105 , and inlet passage  305  and discharge passage  310  are both rigidly attached to hollow rotor  115 . A pin or bolt may be inserted into timing passage  320  and may serve to fixedly secure the position of rotor head  220  with hollow rotor  115  and thereby align and maintain the position of inlet passage  305  and discharge passage  310  over pistons  225  so as to ensure the pressurized fluid is directed to pistons  225  in a sequential manner via inlet passage  305  when pistons  225  are substantially at their upward travel position. A similar pin or bolt may be configured to fixedly attach power plate  230  to hollow rotor  115  and thereby align and maintain the position of power plate  230  to pistons  225 . 
     In the operation of an embodiment of mud motor  100 , pressurized fluid is introduced into rotor head  220  at inlet passage port  300  through inlet shaft  105 . Rotor head  220  directs some or all of the pressurized fluid by way of inlet passage  305  onto pistons  225 . Some or all of pistons  225  are consequently pushed downward within their respective cylinder bores  260 . The resulting reaction force of pistons  225  pushing down on power plate  230  in such embodiment causes power plate  230  to revolve in a rotational direction within motor block  240  and outlet shaft  250 . In concert with this action, hollow rotor  115 , which is fixedly attached to power plate  230  in such embodiment, rotates within outlet shaft  250  and in turn causes rotor head  220 , which is fixedly attached to hollow rotor  115 , to rotate. As power plate  230  rotates in such embodiment, its angular position causes pistons  225  that are in a downwardly extended position to be sequentially pushed upward. As pistons  225  are pushed upward in such embodiment, some or all of the pressurized fluid in the corresponding cylinder bores  260  exits rotor head  220  through discharge passage  310  and is ejected into hollow rotor  115  by way of discharge passage  310 . As rotor head  220  rotates in such embodiment, inlet passage  305  and discharge passage  310  direct some or all of the pressurized fluid to enter into and be discharged from cylinder bores  260  for some or all of pistons  225  such that for every half revolution of power plate  230 , at least some of pistons  225  change from a downward direction to an upward direction. Thus, while pistons  225  remain in a substantially fixed position in such embodiment with respect to their concentric location about outlet shaft  250 , power plate  230 , hollow rotor  115 , and rotor head  220  rotate when pressurized fluid is introduced into motor block  240 . 
     In one embodiment, rotor head  220  includes bypass jet  315  which may selectively direct some or all of the pressurized fluid from inlet passage  305  to hollow rotor  115  so that some or all of the pressurized fluid bypasses pistons  225 . In this manner, the speed or number of rotations of power plate  230 , hollow rotor  115 , and rotor head  220  may be selectively controlled. 
     To the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited to the specific embodiments described in the foregoing detailed description.