Abstract:
An electrical submersible pumping assembly having a seal section and a motor section, and seals that prevent leakage from the seal section and the motor section during assembly. The seals cooperate with a coupling assembly for coupling together shafts from both the seal section and motor section. The coupling assembly outer diameter enlarges at a shoulder that circumscribes its outer surface. In one example, the seal that prevents leakage from the seal assembly provides a sealing interface around the larger diameter portion of the coupling assembly, that is removable by sliding the coupling so its smaller diameter portion is adjacent the seal assembly. The motor section is sealed by another sealing assembly that includes a body that circumscribes the motor shaft to define an annulus, a sealing disk selectively fills the annulus. The sealing disk can also be slid away from within the body while coupling the shafts with the coupling assembly.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application relates to U.S. provisional application 61/121,813 filed on Dec. 11, 2008, the entire specification of which being herein incorporated by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     This invention relates in general to oil and gas production, and in particular to coupling segments of an electrical submersible pump. 
     2. Background of the Invention 
     Electrical submersible pumps (ESP) may be deployed within a wellbore to pump downhole fluid to the surface. Typically, an ESP includes an electrical motor, a seal section, and a pump that is driven by the motor. The pump can discharge pressurized fluid directly into the wellbore or into connected production tubing. A typical seal section includes a diaphragm that is in pressure communication with ambient pressure on one side, and on its other side in pressure communication with the motor section. A body of substantially incompressible equalizing fluid, such as a dielectric fluid, fills the diaphragm, the motor section, and the fluid paths or passageways between the diaphragm and the motor section. Maintaining the pressure within the motor section at substantially ambient pressure minimizes a pressure differential across the housing and seals of the motor section; thereby reducing the chances of a breach in the housing or seals that would allow fluid ingress. 
     Prior to assembling an ESP, the seal section is typically filled with an equalizing fluid and then purged of any air that may remain inside after being filled. When the ESP is vertically assembled, equalizing fluid may leak from the bottom of the seal section as it is being connected to the motor. Any voids formed in the seal section by leaked equalizing fluid, can allow compressible air to reenter the seal section, thereby partially disabling its equalizing abilities. The motor section is also typically filled with fluid prior to assembly. Generally a motor section is not prone to fluid leakage when the ESP is vertically assembled, however the motor section can leak if the ESP is horizontally assembled. 
     SUMMARY OF THE INVENTION 
     Disclosed herein is an example of an electrical submersible pumping assembly having a seal section and a motor section, and seals that prevent leakage from the seal section and the motor section during assembly. When the seal and motor sections are coupled, the seals move out of sealing alignment to allow fluid communication between these sections. The seals cooperate with a coupling assembly for coupling together shafts from both the seal section and motor section. The coupling assembly outer diameter enlarges at a shoulder that circumscribes its outer surface. In one example, the seal that prevents leakage from the seal assembly provides a sealing interface around the larger diameter portion of the coupling assembly, that is removable by sliding the coupling so its smaller diameter portion is adjacent the seal assembly. The motor section is sealed by another sealing assembly that includes a body that circumscribes the motor shaft to define an annulus, a sealing disk selectively fills the annulus. The sealing disk can also be slid away from within the body while coupling the shafts with the coupling assembly. 
     In one example embodiment, the electrical submersible pumping system includes a seal section having a housing with an opening at an end, fluid within the housing, and a seal shaft within the opening in the seal housing, a motor section having a housing having an opening at an end, and a motor shaft extending from the opening in the motor housing, a tubular coupling assembly having a splined axial bore and selectively moveable between a pre-assembly position with the seal shaft partially inserted into an inner end of the coupling assembly and an assembled position axially spaced from the pre-assembly position with the seal shaft fully inserted into the inner end and the motor shaft fully inserted into an outer end of the coupling assembly to transmit torque from the motor shaft to the seal shaft, and a seal section fluid retaining seal mounted to the housing of the seal section and in sealing engagement with an outer diameter portion of the coupling assembly to thereby form a fluid barrier between the outer diameter of the coupling assembly and housing of the seal section when the coupling assembly is in the pre-assembly position and when the coupling assembly is moved to the assembled position, the fluid barrier is removed to define a flow path between the seal section and the motor section. 
     In another example embodiment, disclosed herein is a method of forming an electrical submersible pumping system that includes providing a seal section having a seal housing and a seal shaft, providing a motor section having a motor housing and a motor shaft, sliding a coupling partially over an end of the seal shaft and positioning the coupling in a pre-assembly position, setting a seal between the coupling and the seal housing to retain fluid in the seal section housing, inserting an end of the motor shaft into the coupling opposite the seal shaft while the coupling is in the pre-assembly position, and with the motor shaft, pushing the coupling further into the seal section housing, to position the coupling in the assembled position, and disengage the seal from sealing engagement with the coupling so that the motor housing and the seal housing are in fluid communication with each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some of the features and benefits of the present disclosure having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a side sectional view of a submersible pumping system disposed in a wellbore. 
         FIG. 2  is an exploded partially sectional view of an embodiment of a coupling assembly for use with an electrical submersible pumping system in accordance with the present disclosure. 
         FIG. 3  depicts partial assembly of the coupling assembly of  FIG. 2  in a side sectional view. 
         FIG. 4  illustrates an assembled version of the coupling assembly of  FIG. 2  in a side sectional view. 
         FIG. 5  is an exploded partially sectional view of an alternative coupling assembly. 
         FIG. 6  is an assembled version of the coupling assembly of  FIG. 5  in a side sectional view. 
     
    
    
     While the subject device and method will be described in connection with the preferred embodiments but not limited thereto. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the present disclosure as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The method and system of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments are shown. The described method and system may be in many different forms and should not be construed as limited to the illustrated embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be through and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. 
       FIG. 1  is a side partial section view of an example of an ESP system  8 . In this example, the ESP system  8  is disposed in a wellbore  7  that intersects a subterranean formation  6 . The ESP system  8  includes a motor section  36  having an electrical motor (not shown) within for driving a pump  15 . A seal section  10  is also included shown adjacent the motor section  36 . An optional gas separator  17  is shown disposed between the seal section  10  and pump  15 . Fluid inlets  19  project through the gas separator  17  housing to provide a pathway for fluid in the wellbore  7  to enter the ESP system  8 . Fluid discharged from the pump  15  of  FIG. 1  is pumped through production tubing  9  shown connected to the pump  15 ; the pumped fluid may be directed within the production tubing  9  to a production tree  5  located at the surface. 
     Assembling an ESP system  8  includes attaching shafts within adjacent members of the ESP  8 .  FIG. 2  is an exploded side partial sectional view of respective mating portions of the seal section  10  and the motor section  36  being brought together for coupling engagement by an annular coupling  24 . The step of coupling includes inserting the coupling  24  and an adapter plate  50  between the seal section  10  and motor section  36 . As shown in  FIG. 2 , the seal section  10  includes a body  12  with a seal shaft  14  coaxially aligned in the body  12 . The seal shaft  14  lower end projects from the seal body  12  and the seal shaft  14  upper end connects to a pump shaft (not shown) used in driving the pump  15  ( FIG. 1 ). A flange  16  is shown projecting radially outward from the outer surface of the body  12  on its lower end. Bolt holes  18  are formed through the flange  16  and substantially parallel with an axis A X  of the coupling  24 . Bolts (not shown) can be inserted through the bolt holes  18  for securing the seal section  10  to the motor section  36 . The lower portion of the seal body  12  is annular with an opening  20  shown receiving the coupling  24 . Seals  21  are shown provided on the outer surface of the body  12  in the region between the flange  16  and the opening  20 . The coupling  24  as shown is a substantially cylindrical body  26  having a bore  28  circumscribing its axis A X . Female splines provided on the bore  28  outer periphery are contoured to engage and mate with corresponding male splines on the seal shaft  14 . Shown upwardly extending from the motor  36  is a motor shaft  40  having male splines on the outer surface of its upper end configured to engage the female splines in the bore  28 . Flow within the shaft coupling  24  is prevented by a flow barrier  34  sealingly disposed within the bore  28 . A seal  33  is shown on the outer surface of the flow barrier  34 . In the embodiment illustrated, the flow barrier  34  includes a check valve  35 , but the flow barrier  34  can be any device that seals within the bore  28  to prevent fluid communication through the shaft coupling  24 . Alternatively, a disk transverse to the axis A X  and in the bore  28  can be used for blocking flow through the shaft coupling  24 . 
     The outer surface of the body  26  transitions inward proximate its lower end to form a shoulder  27  on the body  26  shown on the side of the flow barrier  34  opposite the seal shaft  14 . A groove  30  is shown circumscribing the outer surface of the body  26  at about is mid section; a retaining ring  32  is provided in the groove  30 . As will be described in further detail below, the coupling  24  is insertable onto the seal shaft  14  by applying an axial force to the retaining ring  32 . 
     The adapter plate  50 , shown between the coupling  24  and the motor section  36 , is a generally disk like member with an axial bore  51  formed therethrough. An upper cavity  54  in the adapter plate  50  circumscribes the bore  51  and faces the coupling  24 . The adapter plate  50  includes a radial flange  53  on its outer surface on the side facing the seal  10 . Bolt holes  52  are axially formed through the flange  53  and border the upper cavity  54 . The upper cavity  54  provides an upper opening  56  on the adapter plate  50 . A corresponding lower cavity  57  is formed on the adapter plate  50  lower surface thereby forming a lower opening  58 . Seals  59  are shown on the outer surface of portion the adapter plate  50  on the portion circumscribing the lower cavity  57  and bore  51 . 
     An annular seal assembly  60  is shown disposed within the lower opening  58  that includes a ring like base  62  shown press fit within and coaxial with the cavity  57 . A flexible seal  64  is shown attached to the base  62  and along its inner radius. In the embodiment of  FIG. 2 , the base  62  has an “L” shaped cross section, with the elongate portion of the “L” adjacent the wall of the cavity  57  and the shorter and horizontally oriented portion of the “L” projecting radially inward from the wall of the cavity  57 . The flexible seal  64  projects radially inward from the base  62  toward the adapter plate  50  axis. In one embodiment, the base  62  is comprised of a metal or metallic material, the flexible seal  64  may be formed from an elastomer or elastomeric material, such as silicone or rubber. 
     Still referring to  FIG. 2 , a housing  38  is provided that encloses therein motor section  36  components, including a portion of the motor shaft  40 . Bolt holes  44 , axially projecting into the body  38 , can be used for attachment via fasteners to the seal section  10 . Optionally, threaded fittings can be used in lieu of the fasteners. A cylindrically shaped housing opening  42  is shown within the housing  38  upper end through which the motor shaft  40  upwardly extends. 
     With reference now to  FIG. 3 , shown in a side partial sectional view is an example of a step of assembling the seal section  10  and the motor section  36 . The coupling  24  is shown inserted within the seal body  12  and with the upper end of the coupling  24  engaging the seal shaft  14 . The adapter plate  50  is coaxially set against the seal section  10  lower end, having its flange  53  positioned adjacent the seal section flange  16  and the seal section bolt holes  18  aligned with the adapter plate bold holes  52 . When so aligned, the lower end of the coupling  24  projects outside of the seal section opening  20  and within the bore  51  of the adapter plate  50 . The entire adapter plate  50  has slid past the shoulder  27  so that it is between the shoulder  27  and the groove  30 . In this configuration, the flexible seal  64  at the inner radius of the seal assembly  60  contactingly circumscribes the outer radius of the coupling  24 . Also, the seals  21  are in sealing contact with the part of the retaining ring  50  that defines the outer periphery of the upper cavity  54 . 
     As shown, the flexible seal  64  circumscribes the coupling  24  at a location along its axis A X  between the shoulder  27  and the groove  30 . The contact between the flexible seal  64  and the outer diameter of the coupling  24  forms a seal interface along the entire outer circumference of the coupling  24 . The seal interface prevents fluid from leaking out of the seal section  10  and around the coupling  24 . Seals on the flow barrier  34  shown extending between the coupling bore  28  and flow barrier  34  prevent fluid from flowing through the coupling  24 . The coupling  24  is secured within the seal section  10  by an interference contact between the retainer ring  32  and the adapter plate  50 . An optional second retainer ring (not shown) may be installed on the coupling  24  between the adapter plate  50  and the shoulder  27  to prevent the coupling  24  from sliding through the adapter plate  50 . The second retainer ring can be removed when the adapter plate  50  is installed onto the seal section  10 . 
     As illustrated in a side partial sectional view in  FIG. 4 , ESP  8  assembly continues by engaging the seal section  10  with the motor section.  36 . Here the pump shaft  40  is inserted into the bore  28 , which urges the coupling  24  into the seal section  10 . Continued inward urging can move the shoulder  27  past the seal assembly  60 . The seal assembly  60  is no longer in sealing engagement with the coupling  24 , thus removing the fluid barrier at the seal section  10  lower end and allowing fluid communication between the seal  10  and the motor  36 . Seal assembly  60  ceases to seal only after the lower end of seal section  10  is inserted into the cavity at the upper end of motor section  36 . Without the sealing interface between the seal assembly  60  and the coupling  24 , a direct fluid and pressure communication path extends between the motor section  36 , through the retainer  50 , and along the annulus  29  in the space between the coupling  24  and the seal body  12 . The coupling assembly disclosed herein prevents fluid leakage from the seal section  10  prior to ESP  8  assembly, but the barrier it provides is seamlessly removed during assembly to allow pressure communication between the seal section  10  and the motor section  36 . In addition to stemming fluid leakage from the seal section  10 , the coupling assembly also prevents air ingress to the seal section  10 . 
       FIG. 5  depicts an alternative embodiment of a coupling assembly having a motor section retainer plate  80  coupled to the motor section  36 . Here the seal section  10  and motor section  36  are in a horizontal orientation during assembly. The adapter plate  50  as described above is shown attached to the seal section  10  and in sealing contact with the coupling  24  thereby sealing fluid within the seal section  10 . When the ESP  8  is horizontally assembled, connecting the motor section retainer plate  80  to the motor section  36  can seal fluid in the motor section  36 . 
     More specifically, the motor section retainer plate  80 , in the embodiment shown, is an annular member having a bore  81  coaxially formed along its axis. The retainer plate  80  includes an outer cavity  84  formed on its side facing the sealing section  10 . The outer cavity  84  provides an opening  85  on the outer side of the adapter plate  80 . Also included is a flange  83  circumscribing the upper cavity  84  having bolt holes  82  foamed therethrough that are substantially aligned with the axis A X  of the coupling  24 . The bolt holes  82  are shown aligned with bolt holes  44  in the motor section  36 . The adapter plate  80  includes an inner cavity  86  shown facing away from the motor section  36  and substantially coaxial with the axis A X  of the coupling  24 . A middle cavity  87  is provided in the adapter plate  80  between the outer and inner cavities  84 ,  86  and circumscribing the bore  81 . A seal  88  encircles the portion of the adapter plate  80  that circumscribes the inner and middle cavities  86 ,  87  projecting radially outward into sealing contact with the motor housing opening  42 . A lip seal  89  is illustrated within the cavity  86  for sealing between the adapter plate  80  and outer member  72 . 
     An annular sealing assembly  70  is shown coaxially with the axis A X  and in the annular space between the middle cavity  87  and shaft outer diameter. The sealing assembly  70  of  FIG. 5  extends into both the outer and inner cavities  84 ,  86 . In the embodiment shown, the sealing assembly  70  includes an annular outer member  72  having an outer surface contacting the middle cavity  87 . The sealing assembly  70  of  FIG. 5  further includes an annular inner member  74  that occupies the space between the outer member  72  and the outer surface of the motor shaft  40 . A sealing interface is formed between the inner member  74  and the motor shaft  40 . In one embodiment, the outer member  72  is formed from a metal or metallic material, and the inner member  74  includes an elastomer or other resilient flexible material. The inner member  74  has a passage formed to match the splines on the shaft  40 , thereby sealing against the shaft  40 . Thus fluid in the motor section  36  is prevented from leaking out by affixing the motor section retainer plate  80  as illustrated. 
       FIG. 6  provides an assembled view of the embodiment of  FIG. 5 . While coupling the seal section  10  to the motor section  36 , the lower end of the coupling  24  contacts and urges the sealing assembly  70  from the middle cavity  87  and into the larger diameter inner cavity  86 . The inner diameter of the inner cavity  86  exceeds the outer diameter of the sealing assembly  70  to form an annular space between the two, through which fluid in the motor section  36  can flow. Thus pushing the sealing assembly  70  into the inner cavity  86 , removes the fluid flow barrier in the motor section adapter plate  80  thereby allowing fluid communication from the motor section  36 . As noted above, the flow barrier between the lip seal assembly  60  and the coupling  24  is also removed when coupling the seal section  10  to the motor section  36 . Thus open fluid communication between the motor section  36  and the seal section  10  occurs when the two sections are mated. 
     While the invention has been shown in only one of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention. For example, instead of connecting a seal section to a motor section, the lower section could comprise connecting the seal section to a lower tandem seal section.