Patent Publication Number: US-10760352-B2

Title: Rotor catch assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to drilling motors and, more particularly (although not necessarily exclusively), to assemblies and methods for catching a rotor in a downhole motor assembly. 
     BACKGROUND 
     A downhole motor may utilize fluid energy converted to mechanical energy to provide shaft rotation to a drill string or drill bit. The downhole motor may include a power section having a rotor operating within a stator. Because the stator is a highly loaded section of a drilling tool during operation of the downhole motor, connections within and near the stator may be prone to failure. Failure of the stator connections may result in the separation of components and a risk that these components may be lost downhole. The lost components dropped downhole may prevent further progression in drilling and can cause significant delays. In some instances, the loss of components downhole may even result in a drilling project being abandoned. A procedure known as “fishing” is sometimes used to retrieve the lost components, but this procedure is costly and time-consuming, and may be ineffective. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional schematic diagram depicting a drilling system that includes a catch assembly in a downhole motor assembly according to one aspect of the present disclosure. 
         FIG. 2  is a partial perspective view of a downhole motor assembly having a catch assembly according to one aspect of the present disclosure. 
         FIG. 3  is a cross-sectional view of a rotor knob of the catch assembly of  FIG. 2  according to one aspect of the present disclosure. 
         FIG. 4  is a cross-sectional view of a catch basket of the catch assembly of  FIG. 2  according to one aspect of the present disclosure. 
         FIG. 5  is a cross-sectional view of the downhole motor assembly of  FIG. 2  according to one aspect of the present disclosure. 
         FIG. 6  is a flowchart of an example of a process for installing a catch assembly according to one aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Certain aspects and examples of the present disclosure relate to a downhole motor assembly including a catch assembly to prevent a loss of the rotor downhole subsequent to a connection failure or downhole motor failure in or proximate to a stator. In some aspects, the catch assembly may include a catch basket. The catch basket may be a component of the catch assembly capable of interfering with a portion of the rotor to retain the rotor in a tube of a stator. For example, the catch basket may include an internal shoulder sized to interfere with a rotor knob in the event of a failure of a stator connection downhole of the catch basket and prevent the rotor from exiting the stator tube. In additional aspects, the catch basket may also include an uphole end that may be coupled to an interior surface of a saver sub to retain the rotor in the event of a connection failure between the stator and the saver sub. A downhole portion of the catch basket including the internal shoulder may extend downhole of the saver sub into a stator tube of the stator. The stator tube may be coupled to the saver sub at a connection point downhole of the connection point of the saver sub and the catch basket. 
     The rotor knob may include a flange on an uphole portion of the rotor knob and a threaded end on the downhole portion of the rotor knob for coupling to an uphole end of the rotor positioned in the stator. The flange of the rotor knob may be positioned uphole of the internal shoulder. The body of the rotor knob may extend to the threaded end of the rotor knob positioned downhole of the internal shoulder. In the event of a connection failure or motor failure downhole of the catch basket, the rotor may attempt to exit the stator and fall downhole. The internal shoulder of the catch basket may be sized to interfere with the flange of the rotor knob to prevent the loss of the rotor downhole. In the event of a failure at the connection point of the saver sub and the stator tube, the rotor may be maintained by the connection of the catch basket to the saver sub uphole of the connection point of the save sub and the stator tube. 
     The use of a catch assembly in a downhole motor assembly may result in savings by the reduction of the replacement costs for drilling components that may otherwise be lost downhole. The catch basket may be easily coupled to the saver sub and serve to prevent the loss of expensive drilling components (e.g., the rotor) in the event of connection failures not only downhole of the internal shoulder of the catch basket, but also in the event of a connection failure between the stator tube and the saver sub. Savings may further be realized in the time and labor costs by the reduction in fishing expeditions to retrieve separated components and the resulting delays in drilling operations in performing such fishing expeditions. 
     The terms “inner,” “outer,” “internal,” “external,” “interior,” “exterior,” and “between,” as used in the present disclosure may refer to a radial orientation toward or away from the center of the mud motor drilling assembly unless otherwise stated. The terms “uphole,” “downhole,” “above,” and “below,” as used in the present disclosure may refer to an axial orientation toward or away from the surface unless otherwise stated. 
     Various aspects of the present disclosure may be implemented in various drilling systems.  FIG. 1  illustrates an example of such a drilling system  100  that includes a drill string  102 . The drill string  102  of a drilling rig (not shown) may include segmented pipes that may extend below the surface  104  in a borehole, such as a wellbore  106 . The drill string  102  may transmit drilling fluid (or mud) and the torque necessary to operate a drill bit  108 . Also, the weight of the drill string  102  may provide an axial force on the drill bit  108 . The drill string  102  may include a drill pipe  110  and a bottom hole assembly  112 . The bottom hole assembly  112  may be include various components, such as a downhole motor assembly  114  and the drill bit  108  at a downhole end of the drill string  102 . In some aspects, the downhole motor assembly  114  may include a downhole motor having a power section. The power section may include a rotor housed in a stator. The rotor may be connected to the drill bit  108  via a driveshaft. Though placement of the assemblies disclosed herein may vary without departing from the scope of the present subject matter, the assemblies of the present disclosure may be included in the downhole motor assembly  114 . For example, the functional block in the downhole motor assembly  114  in  FIG. 1  may represent a placement of the catch assembly  116  according to one example. 
       FIG. 2  shows a partial cross-sectional view of a catch assembly  116  that may be positioned in the downhole motor assembly  114  of the drilling system  100  of  FIG. 1 , according to one example. The catch assembly  116  includes a catch basket  200 . The catch basket  200  may be a container-like component of the catch assembly  116  that is sized and positionable in the catch assembly  116  to retain components (e.g., a rotor) positioned proximate to or downhole of the catch assembly  116 . The catch basket  200  includes a threaded end  202  on an uphole portion of the catch basket  200  that may be mated with corresponding threads on a saver sub  204  to couple to the catch basket  200  to the saver sub  204 . The saver sub  204  may be coupled to a stator tube  206  of a stator of the downhole motor assembly  114 . The stator tube  206  may be positioned downhole of the saver sub  204 . The catch basket  200  may be positioned internal to the saver sub  204  and the stator tube  206 . For example, the threaded end  202  of the catch basket  200  may be coupled to an interior surface of the saver sub  204 . 
     The catch basket  200  may extend downhole below the end of the saver sub  204  into the stator tube  206 . The catch basket  200  may include an internal shoulder  208  extending from an interior surface of the catch basket  200 . The internal shoulder  208  of the catch basket  200  may be positioned internal to the stator tube  206  and downhole of the saver sub  204  when the catch basket  200  is assembled in the catch assembly  116 . The saver sub  204  and the stator tube  206  may be coupled at a connection point  210  where threads  212  on the saver sub  204  are mated with threads  214  on the stator tube  206 . The connection point  210  may be positioned downhole of the threaded end  202  where the catch basket  200  is coupled to the saver sub  204 . The connection point  210  further may be positioned uphole of the internal shoulder  208  of the catch basket  200 . The threads  212 ,  214  at the connection point  210  may be corresponding threads to allow the saver sub  204  and the stator tube  206  to be coupled. 
     The catch basket  200  may also include a body  216  having an internal surface defining a through-bore  218  internal to the catch basket  200 . In some aspects, the through-bore  218  may extend from the threaded end  202  of the catch basket  200  at the uphole end of the catch basket  200  through the internal shoulder  208  at the downhole end of the catch basket  200 . In additional aspects, the internal surface of the body  216  may be shaped to define portions of the through-bore  218  having varying diameters to allow and prevent varying components of the drilling assembly to pass through the catch basket  200 . For example, a rotor knob  220  may be positioned in the through-bore  218  of the catch basket  200 . The rotor knob  220  may be coupled to an uphole end of a rotor  222 . In some aspects, at least a portion of the through-bore  218  may include a diameter large enough to allow the rotor knob  220  to pass into the catch basket  200 . A portion of the rotor knob  220  may remain internal to the catch basket  200  when the rotor knob  220  is coupled to the rotor  222 . The rotor  222  may be positioned internal to the stator tube  206  and downhole of the saver sub  204  and the catch basket  200 . 
       FIG. 3  is a cross-sectional view of the rotor knob  220  according to one example. The rotor knob  220  includes a flange  300  and a body  302 . The flange  300  may be positioned at an uphole end of the rotor knob  220 . The flange  300  may include a diameter that is greater than a diameter of the body  302 . In some aspects, the flange  300  may form a bulbous portion of the rotor knob  220 . The body  302  of the rotor knob  220  may include a threaded end  304  and a shoulder  306  at a downhole portion of the rotor knob  220 . The threaded end  304  may include threads corresponding to threads in the uphole end of the rotor  222  shown in  FIG. 2  to couple the rotor knob  220  to the rotor  222 . In some aspects, the threaded end  304  may be nose-loaded such that the shoulder  306  may protect the threads on the threaded end  304  from impingent damage. In additional and alternative aspects, the shoulder  306  may engage the uphole end of the rotor  222  when threads on the threaded end  304  of the rotor knob  220  are fully mated with the corresponding threads on the rotor  222 . The flange  300  of the rotor knob  220  may include grooves  308 A,  308 B. In some aspects, the grooves  308 A,  308 B may be sized and positioned to engage a wrench. The wrench may be positioned in the grooves  308 A,  308 B and used to torque the rotor knob  220  to the rotor  222  shown in  FIG. 2 . 
     The rotor knob  220  further may include a center bore  310 . The center bore  310  of the rotor knob  220  may extend through axial length of the rotor knob  220  from the flange  300  at the uphole end of the rotor knob  220  through the threaded end  304  at the downhole end of the body  302  of the rotor knob  220 . In some aspects, the center bore  310  may allow drilling fluid to pass through the rotor knob  220 . In some aspects, the center bore  310  of the rotor knob  220  may also include a downhole portion  312  as shown in  FIG. 3 . The downhole portion  312  of the center bore  310  may provide a coupling point to include a drilling component (e.g., a flow jet) downhole of the rotor knob  220 . For example, in some aspects, the downhole portion  312  may include internal threads, an o-ring, or some other coupling mechanism to couple the drilling component to the rotor knob  220 . 
       FIG. 4  is a cross-sectional view of the catch basket  200  shown in  FIG. 2 . The catch basket  200  includes the threaded end  202  at an uphole portion of the catch basket  200  and the internal shoulder  208  at a downhole portion of the catch basket  200 . The through-bore  218  of the catch basket  200  may include portions  218 A,  218 B,  218 C having varying diameters. For example, portion  218 A of the through-bore  218  may include a diameter sized to allow the rotor knob  220  shown in  FIG. 3  to pass through and into the portion  218 B of the through-bore. Portion  218 C of the through-bore  218  may include a diameter sized to allow the body  302  and the shoulder  306  of the rotor knob  220  to pass through and downhole of the catch basket  200 , but may prevent the flange  300  of the rotor knob  220  to exit downhole of the catch basket  200 . 
     The catch basket  200  further may include bypass ports  400 A,  400 B. In some aspects, the bypass ports  400 A,  400 B may be sized to allow fluid to exit the portion  218 B of the through-bore  218 . In  FIG. 4 , the bypass ports  400 A,  400 B are positioned adjacent to the internal shoulder  208  of the catch basket  200 , though the position of the bypass ports  400 A,  400 B may vary. For example, in some aspects, the bypass ports  400 A,  400 B may be positioned in the internal shoulder  208  to allow fluid to pass through the portion  218 B of the through-bore  218  and directly downhole of the catch basket  200 . In some aspects, the bypass ports  400 A,  400 B may be included in the catch basket  200  to provide a passage for fluid to exit the catch basket  200 . For example, drilling fluid may pass through the bypass ports  400 A,  400 B where a blockage impedes an exodus of the fluid through portion  218 C of the through-bore  218 . Although two bypass ports  400 A,  400 B are shown in  FIG. 4 , any number of bypass ports  400 A,  400 B may be included in the catch basket  200 , including one or none, without departing from the scope of the present disclosure. The catch basket  200  may also include an external shoulder  402 . The external shoulder  402  may be positioned uphole of the internal shoulder  208  on an exterior surface of the catch basket  200 . The external shoulder  402  further may be positioned uphole of the bypass ports  400 A,  400 B. 
       FIG. 5  shows a cross-sectional view of the catch assembly  116  shown in  FIG. 2 . The threaded end  202  of the catch basket  200  may be mated with internal threads  500  on the saver sub  204  to couple the catch basket  200  to the interior surface of the saver sub  204 . The exterior surface of the catch basket  200  may be positioned radially adjacent to the interior surface of the saver sub  204  downhole of the threaded end  202  of the catch basket  200  between the threaded end  202  and the external shoulder  402  of the catch basket  200 . The external shoulder  402  may be shaped to correspond to a portion of the saver sub  204  proximate to the threads  212  and the connection point  210  between the saver sub  204  and the stator tube  206  at threads  212 ,  214 . The external shoulder  402  may extend radially from the exterior surface of the catch basket  200  such that the portion of the saver sub  204  proximate to the threads is positioned axially adjacent to the external shoulder  402 . The interior surface of the stator tube  206  downhole of the threads  214  may be positioned radially adjacent to the external shoulder  402  when the saver sub  204  and the stator tube  206  are coupled at the connection point  210 . 
     The rotor knob  220  may be positioned in the through-bore  218  defined by the body  216  of the catch basket  200 . The rotor knob  220  may be coupled to the rotor  222  by mating the threaded end  304  of the rotor knob  220  to internal threads  502  on the uphole end of the rotor  222 . The flange  300  of the rotor knob  220  may be positioned in the portion  218 B of the through-bore  218 . The body  302  of the rotor knob  220  may extend from the portion  218 B through the portion  218 C of the through-bore to the rotor  222  positioned below the catch basket  200 . The flange  300  may be positioned uphole of the internal shoulder  208 . In some aspects, the body  302  of the rotor knob  220  may include an axial length to provide space in the portion  218 B of the through-bore  218  between the flange  300  and the internal shoulder  208  to allow for axial movement of the rotor knob  220  in the portion  218 B of the through-bore  218 . The body  302  of rotor knob may further include a diameter sized to allow the body  302  to pass through the portion  218 C of the through-bore  218  within the internal shoulder  208 . In some aspects, the diameter of the body  302  may provide space in the portion  218 C of the through-bore  218  to allow for eccentric movement of the rotor  222  during operation of the downhole motor. 
     In some aspects, a drilling component may be coupled to the rotor  222  downhole of the rotor knob  220 . The rotor  222  may include a portion  504  for receiving the drilling component. The portion  504  may include an opening sized for the drilling component to be positioned in the rotor  222 . In some aspects, the drilling component may be coupled to the rotor  222  via threading or another coupling mechanism in the downhole portion  312  of the rotor knob  220  shown in  FIG. 3 . In some examples, the drilling component may include a flow jet. A flow jet may be included in the rotor  222  to optimize the performance of drilling fluid flowing through the rotor  222 . In one example, the rotor  222  may be included in the power section of a positive displacement or pseudo-positive displacement downhole motor operating in the wellbore  106  shown in  FIG. 1 . The speed of the downhole motor may be governed by the rate of flow of drilling fluid through the rotor  222 . The flow jet may be coupled to the rotor  222  at portion  504  to allow additional drilling fluid to flow than the drilling fluid used to produce power to the downhole motor. The additional fluid may allow cuttings removed from the wellbore  106  by the drill bit  108  shown in  FIG. 1  to be effectively floated to the surface  104  (e.g., when the drilling fluid used to produce power to the downhole motor is insufficient to float the cuttings to the surface  104 ). 
     Subsequent to a connection failure in the stator tube  206  or any other housing downhole of the connection point  210  of the stator tube  206  and the saver sub  204  shown in  FIG. 5 , the rotor  222  may attempt to exit the stator tube  206  and fall in a downhole direction. As the rotor  222  moves in the downhole direction, the flange  300  of the rotor knob  220  may engage the internal shoulder  208  of the catch basket  200 . The internal shoulder  208  may prevent the flange  300  of the rotor knob  220 , and, by extension, the rotor  222  from continuing to move in the downhole direction out of the stator tube  206 , as the diameter of the flange  300  may be greater than the diameter of the portion  218 C of the through-bore  218  within the internal shoulder  308 . As the flange  300  of the rotor knob  220  engages the internal shoulder  208  of the catch basket  200  in the stator tube  206 , a load may be passed through the rotor  222  to the rotor knob  220 . The load may continue to pass from the flange  300  of the rotor knob  220  to the catch basket  200  via the internal shoulder  208 . The load may then pass through the cross-section of the catch basket  200  and into the saver sub, via the threaded end  202  of the catch basket  200  and the threads  500  of the saver sub  204 , to retain the rotor  222 . 
     The catch assembly  116  of  FIG. 5  may also prevent a loss of the rotor  222  downhole subsequent to a failure of the connection of the stator tube  206  to the saver sub  204  at the connection point  210 . Upon a connection failure at the connection point  210  based on a failure of the threads  214  of the stator tube  206 , the remains of the threads  214  may move downhole to the external shoulder  402  of the catch basket  200 . A load may pass from the stator tube  206  to the catch basket  200  via the external shoulder  402 . The load may then pass through the cross-section of the catch basket  200  and into the saver sub  204 , via the threaded end  202  of the catch basket  200  and the threads  500  of the saver sub  204 , to the retain the stator tube  206  and the rotor  222 . Upon a connection failure at the connection point  210  based on a failure of the threads  212  of the saver sub  204 , the stator tube  206  may move downhole, causing the rotor  222  internal to the stator tube  206  to also move downhole. As the rotor  222  moves downhole, the flange  300  of the rotor knob  220  may engage the internal shoulder  208  of the catch basket  200  and transfer a load through the cross-section of the catch basket  200  into the saver sub  204 , via the threaded end  202  of the catch basket  200  and the threads  500 . 
       FIG. 6  is a flowchart describing a process for assembling the catch assembly  116  according to one example. The process is described with respect to the catch assembly  116  shown in  FIG. 5 , although other implementations are possible without departing from the scope of the present disclosure. 
     In block  600 , the catch basket  200  is coupled to an internal surface of the saver sub  204 . In some aspects, the catch basket  200  and the saver sub  204  may be threadably coupled by mating the threaded end  202  of the catch basket  200  and the corresponding threads  500  on the internal surface of the saver sub  204 . In some aspects, the threaded end  202  of the catch basket  200  may include male threads and the threads  500  may include female threads to allow the catch basket  200  to be coupled to the saver sub  204 . In other aspects, the threaded end  202  may include female threads for mating with male threads  500 . The profile of the exterior surface of the catch basket  200  may correspond to the interior profile of the saver sub such that the catch basket  200  and the saver sub  204  are positioned radially adjacent to each other between the threaded end  202  of the catch basket  200  and the external shoulder  402  of the catch basket  200 . The external shoulder  402  may extend from the exterior surface of the catch basket  200  such that a portion of the saver sub  204  proximate to the threads  212  may be axially adjacent to the external shoulder  402 . In some aspects, the through-bore  218  of the catch basket  200  may be aligned with a through-bore of the saver sub  204  and any additional components coupled to the drill string  102  shown in  FIG. 1  uphole of the catch basket  200  to allow drilling tools and components to be positioned down-hole from the surface  104  via the through-bore  218 . 
     In block  602 , the saver sub  204  may be coupled to the stator tube  206 . In some aspects, the saver sub  204  and the stator tube  206  may be threadably coupled at a connection point  210  by mating the external threads  212  on the saver sub  204  with corresponding internal threads  214  on the stator tube  206 . The catch basket  200  may extend from the saver sub  204  downhole into the stator tube  206  such that the connection point  210  is positioned uphole of the internal shoulder  208  of the catch basket  200 . The internal shoulder  208  may be positioned downhole of the connection point  210  and internal to the stator tube  206  as shown in  FIG. 5 . In some aspects, the portion  218 C of the through-bore  218  may be aligned with an opening in the uphole end of the rotor  222  to allow at least a portion of the rotor knob  220  to pass through portions  218 B,  218 C of the through-bore  218  and into the opening in the uphole end of the rotor  222 . 
     In block  604 , the rotor knob  220  is coupled to the uphole end of the rotor  222 . For example, the threaded end  304  of the rotor knob  220  may be mated with corresponding threading  502  in the uphole end of the rotor  222 . In some aspects, a wrench may be lowered into the through-bore  218  of the catch basket  200  to engage the rotor knob  220 . In some aspects, the wrench may be positioned in the grooves  308 A,  308 B of the rotor knob  220  shown in  FIG. 3 . The wrench may be rotated to torque the threaded end  304  of the rotor knob to the rotor  222 . For example, the wrench may be rotated until the shoulder  306  of the rotor knob  220  engages the rotor  222  indicating that the rotor knob  220  is fully coupled to the rotor  222 . In another example, the wrench may be rotated to nose-load the threaded end  304 . The rotor knob  220  may be coupled to the rotor  222  such that the flange  300  of the rotor knob  220  is positioned in the portion  218 B of the through-bore  218  of the catch basket  200  uphole of the internal shoulder  208 . The body  302  of the rotor knob  220  may extend from the flange  300  positioned in the catch basket  200  to the threaded end  304  downhole of the catch basket  200  and coupled to the rotor  222 . 
     Although the process of  FIG. 6  is described in a particular order, the order of assembling the catch assembly  116  may vary without departing from the scope of the present disclosure. For example, in some aspects, the rotor knob  220  may be positioned in the catch basket  200  and coupled to the rotor  222  prior to coupling the catch basket to the saver sub  204 . The rotor  222  may be pulled uphole out of the power section of the downhole motor to allow threaded end  202  of the catch basket  200  to access the internal threads  500  on the saver sub  204  and complete the catch assembly  116 . 
     In some aspects, downhole motor assemblies are provided according to one or more of the following examples: 
     Example #1 
     A catch assembly may include a rotor knob including a flange and a knob body that has a downhole threaded end couplable to an end portion of a rotor. The catch assembly may also include a catch basket positionable internal to a saver sub and a stator tube. The catch basket may include an uphole threaded end couplable to the saver sub. The catch basket may also include an internal shoulder positionable uphole of the end portion of the rotor and downhole of a connection point between the saver sub and the stator tube. The catch basket may also include a catch basket body defining a through-bore extending from the uphole threaded end to the internal shoulder. At least one portion of the through-bore may be sized to receive the flange of the rotor knob. 
     Example #2 
     The catch assembly of Example #1 may feature the internal shoulder being sized to prevent a loss of the rotor downhole by interfering with the flange of the rotor knob. 
     Example #3 
     The catch assembly of Examples #1-2 may feature the uphole threaded end being positionable uphole of the connection point between the saver sub and the stator tube to prevent a loss of the rotor downhole subsequent to the stator tube separating from the saver sub. 
     Example #4 
     The catch assembly of Examples #1-3 may feature the flange being positionable uphole of the internal shoulder. 
     Example #5 
     The catch assembly of Examples #1-4 may feature the flange including grooves sized to engage a wrench for coupling the flange to the end portion of the rotor. 
     Example #6 
     The catch assembly of Examples #1-5 may feature the internal shoulder being positionable downhole of the saver sub and internal to the stator tube. 
     Example #7 
     The catch assembly of Examples #1-6 may feature the catch basket also including at least one bypass port proximate to the internal shoulder. 
     Example #8 
     The catch assembly of Examples #1-7 may feature the through-bore including a first portion. The first portion may be internal to the uphole threaded end and may include a first diameter. The through-bore may also include a second portion axially between the uphole threaded end and the internal shoulder. The second portion may include a second diameter. The through-bore may also include a third portion internal to the shoulder. The third portion may include a third diameter. The first diameter and the second diameter may be greater than an outer diameter of the flange to allow the flange to pass through the first portion. The third diameter may be less than the outer diameter of the flange to prevent the flange from passing through the third portion. 
     Example #9 
     A downhole motor assembly may include a rotor including an uphole end positionable internal to a downhole end of a stator tube. The downhole motor assembly may also include a rotor knob including a flange and a knob body. The flange may have a first diameter larger than a diameter of the knob body. The knob body may be couplable to the uphole end of the rotor. The downhole motor assembly may also include a saver sub couplable to the stator tube at a connection point between the saver sub and the stator tube. The downhole motor assembly may also include a catch basket. The catch basket may include an uphole end couplable to the saver sub uphole of the connection point. The catch basket may also include an internal shoulder positionable downhole of the connection point and axially between the flange of the rotor knob and the uphole end of the rotor. 
     Example #10 
     The downhole motor assembly of Example #9 may feature the internal shoulder being positionable downhole of the saver sub. The internal shoulder may be sized to prevent a loss of the rotor downhole by interfering with the flange of the rotor knob. 
     Example #11 
     The downhole motor assembly of Examples #9-10 may feature the saver sub including internal threads corresponding to external threads on the uphole end of the catch basket and positionable uphole of the connection point between the saver sub and the stator tube to prevent a loss of the rotor downhole subsequent to the stator tube separating from the saver sub. 
     Example #12 
     The downhole motor assembly of Examples #9-11 may feature the flange including grooves sized to engage a wrench for coupling the flange to the uphole end of the rotor. 
     Example #13 
     The downhole motor assembly of Examples #9-12 may feature the catch basket also including at least one bypass port proximate to the internal shoulder. 
     Example #14 
     The downhole motor assembly of Examples #9-13 may feature the catch basket further including an external shoulder positionable downhole of the connection point to receive an axial load from the stator tube subsequent to the stator tube at least partially separating from the saver sub. 
     Example #15 
     The downhole motor assembly of Examples #9-14 may feature the diameter of the knob body of the rotor knob being sized to eccentrically move within a center bore of the internal shoulder during operation of the rotor. 
     Example #16 
     The downhole motor assembly of Examples #9-15 may feature the rotor knob including a center bore to allow drilling fluid to pass between the catch basket and the rotor during operation of the rotor. 
     Example #17 
     A method may include coupling a catch basket to an interior surface of a saver sub. The catch basket may include a through-bore sized to allow a rotor knob to pass through the through-bore. The method may also include coupling the saver sub to a stator tube at a connection point uphole of an internal shoulder of the catch basket. The method may also include coupling the rotor knob to an uphole end of a rotor positioned in the stator tube to position a flange of the rotor knob uphole of the internal shoulder. 
     Example #18 
     The method of Example #17 may feature coupling the catch basket to the interior surface of the saver sub to include mating an uphole threaded end of the catch basket with internal threading on the saver sub uphole of the connection point. 
     Example #19 
     The method of Examples #17-18 may feature coupling the saver sub to the stator tube to include positioning the internal shoulder of the catch basket internal to the stator tube. 
     Example #20 
     The method of Examples #17-19 may feature coupling the rotor knob to the uphole end of the rotor to include lowering a wrench into the through-bore of the catch basket. Coupling the rotor knob to the uphole end of the rotor may also include positioning the wrench in grooves of the rotor knob. Coupling the rotor knob to the uphole end of the rotor may also include mating, via the wrench, a downhole threaded end of the rotor knob with threading on the uphole end of the rotor. 
     The foregoing description of the examples, including illustrated examples, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or to limit the subject matter to the precise forms disclosed. Numerous modifications, adaptations, uses, and installations thereof can be apparent to those skilled in the art without departing from the scope of this disclosure. The illustrative examples described above are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts.