Abstract:
A through tubing conveyed electrical submersible pumping system for use in a wellbore. The system includes a tubing string with an attached deployed drive system having a pump motor and a pump engaging receptacle, a pumping assembly insertable into the tubing deployed system, and sealing elements on both the tubing string and pumping assembly. Engaging the sealing elements while inserting the pumping assembly forms a seal. The system further includes mating latch members on the pumping assembly and the tubing string, the latch members selectively activated by engaging one another. The latch may include locking fingers disposed on the pumping system and a shoulder protruding into the tubing string; wherein inserting the pumping system into the tubing deployed system locking fingers with the shoulder for securing the pumping system to the tubing string.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of co-pending U.S. Provisional Application Ser. No. 60/987,999, filed Nov. 14, 2007, the full disclosure of which is hereby incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of Invention 
         [0003]    The present disclosure relates to a through tubing submersible pump having a mechanically locking seal for sealing flow between the pump and the tubing. 
         [0004]    2. Description of Prior Art 
         [0005]    Submersible pumping systems are often used in hydrocarbon producing wells for pumping fluids from within the well bore to the surface. These fluids are generally liquids and include produced liquid hydrocarbon as well as water. One type of system used in this application employs an electrical submersible pump (ESP). ESPs are typically disposed at the end of a length of production tubing and have an electrically powered motor. Often, electrical power may be supplied to the pump motor via cable strapped to the exterior of the production tubing. ESP&#39;s may comprise centrifugal pumps or progressing cavity pumps. Progressing cavity pumps (PCP) are positive displacement pumps that consist of a helical steel rotor inside a synthetic elastomer bonded to a steel tube (stator). As the rotor turns within the stator, fluid moves through the pump from cavity to cavity. The resulting pumping action increases the pressure of the fluid, allowing production to the surface. 
         [0006]      FIG. 1   a  depicts a partial sectional view of a prior art submersible ESP system disposed in a wellbore. The ESP production system  2  shown comprises a pumping system  12  on production tubing  8 ; where the tubing  8  is suspended within a cased wellbore  4 . The downhole pumping system  12  comprises a pump section  13 , a seal section  14 , and a motor  17 . The seal section  14  equalizes fluid pressure in the motor  17  with pressure in the wellbore fluid. An electrical conduit  15  is strapped externally to the tubing  8 , pump section  13 , and seal section  14 . Energizing the motor  17  drives a shaft (not shown) coupled between the motor  17  and the pump section  13 . 
         [0007]    Inlets  16  provided at the bottom of the pump section housing provide a passage for formation fluid to flow from the annulus between the casing  5  and system  12  into the pump section  13 . Perforations  7  project into an adjacent formation  6  to provide a source for the formation fluid. As illustrated by the arrows, the formation fluid flows from the formation  6 , through the perforations  7 , up the annulus, and to the inlets  16 . Fluid drawn into the inlets  16  is pressurized within the pump section  13 , and then discharged into the tubing  8 . 
         [0008]    When installing an ESP through tubing, the pump assembly is lowered into and suspended within the production tubing. Typically the motor is mounted to the lower end of the production tubing, and the pump assembly stabs into engagement with the drive shaft of the motor. In this configuration the pump discharges into the production tubing.  FIG. 1   b  provides in partial sectional view an example of a prior art through tubing conveyed ESP initially deployed in a wellbore and before installing the pump. In  FIG. 1   b , a tubing deployed drive system  19  is shown on production tubing  8  disposed in a cased wellbore  4 . The tubing deployed drive system  19  illustrated comprises an engaging receptacle  20 , a seal section  14 , and a motor  17 . 
         [0009]      FIG. 1   c  depicts a partial sectional view of an example of a through tubing conveyed ESP system having a pump installed. In  FIG. 1   c , an ESP production system  2  is formed when a downhole pumping assembly  21  is inserted within a tubing deployed drive system  19 , a packer  22  is installed within the tubing  8  at the top of the pump, and a tubing anchor  23  is installed within the tubing  8  at the top of the packer. The downhole pumping assembly  21  comprises an engaging base (not detailed) compatible with the engaging receptacle  20 , an inlet section (not detailed), a pump section, and a receptacle (not detailed) suitable for use with downhole tooling commonly found in oilfield practice. A stinger on the packer  22  sealingly inserts into the tooling receptacle at the top of the pump assembly  21 , and a stinger on the tubing anchor  23  sealingly inserts into a like receptacle at the top of the packer. The packer  22  serves to isolate the produced fluids from the well bore, and the tubing anchor  23  serves to secure the pumping assembly  21  within the tubing  8 . 
         [0010]    Energizing the motor  17  then drives shafts (not shown) variously coupled between the motor and the pump assembly  21 . Inlets  16  are provided on the engaging receptacle  20  wherein formation fluid can be drawn into the inlets  16  then into the inlet section of the pump assembly  21  and up into the pump section. Formation fluid flow, represented by arrows, flows into the annulus from perforations  7  extending a surrounding hydrocarbon producing formation  6 . The pump discharges the formation fluid through the packer  22  and the tubing anchor  23  into the tubing  8 . Packer  22  provides sealing between the pump discharge and the inlets  16 , thereby maintaining sufficient pressure in the tubing  8  to force the production fluid up the well bore  4  to the wellhead  9 . Upon reaching the wellhead  9 , the production fluid can be distributed via an attached production line  10 . 
       SUMMARY OF INVENTION 
       [0011]    The present disclosure includes a through tubing conveyed electrical submersible pumping system for use in a wellbore comprising, a tubing string, a seal ring protruding inward from the tubing string inner wall, a tubing deployed drive system having a pump motor, a pumping assembly insertable into the tubing deployed system, a seating cone on the pumping assembly that when engaged with the seal ring forms a seal in the space between the tubing string and the pumping assembly. Engaging the seal ring with the seating cone is accomplished by inserting the pumping assembly into the tubing string to contact the ring and cone. 
         [0012]    An optional latch assembly is provided having corresponding latching components on the pumping assembly and the tubing string. The pumping assembly is selectively latchable within the tubing string by advancing the pumping assembly until the latching components engage. In one embodiment the latching components include locking fingers disposed on the pumping system and a shoulder within the tubing string. Latching may include sliding the fingers past the shoulder, wherein the fingers bend inwards when contacting the shoulder and spring outward when pushed past the shoulder. The fingers abut the shoulder lower surface to provide a retaining force for securing the pumping system within the tubing string. Optionally, the seal ring may comprise the shoulder. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    Some of the features and benefits of the present invention having been stated, others will become apparent as the description proceeds when taken in conjunction with the accompanying drawings, in which: 
           [0014]      FIG. 1   a  is a partial cross sectional view of a prior art electric submersible pump. 
           [0015]      FIG. 1   b  is a partial cross sectional view of a prior art tubing deployed drive system installation of a through tubing conveyed submersible pumping system. 
           [0016]      FIG. 1   c  is a partial cross sectional view of a prior art completed installation through tubing conveyed submersible pump. 
           [0017]      FIG. 2  illustrates in a side sectional view an embodiment of a pumping system. 
           [0018]      FIGS. 3   a  and  3   b  provide side partial sectional views of adjacent sections of a portion of the pumping system of  FIG. 2 . 
           [0019]      FIGS. 4   a  and  4   b  depict adjacent sections of a tubing installation with a seal assembly in a side partial sectional view. 
           [0020]      FIGS. 5   a - 5   c  provide side views of adjacent portions of a completed assembly. 
       
    
    
       [0021]    While the invention will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF INVENTION 
       [0022]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which embodiments of the invention are shown. This invention may, however, be embodied 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 thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
         [0023]      FIG. 2  illustrates an embodiment of a progressing cavity pumping system  24  in a side partial sectional view. The pumping system  24  comprises an engaging base  30  on its lower end externally configured to mate within production tubing  76  ( FIG. 4 ). The engaging base  30  includes a coupling  28  on its lower end configured to mate with an intake coupling (not shown) disposed on the tubing  76 . A lower flex shaft housing  32  connects to the engaging base  30  on an end opposite the coupling  28 . As shown, the lower flex shaft housing  32  is a generally tubular member having apertures on its outer surface configured to receive wellbore production fluid for delivery to the pump section  38 . A mandrel assembly  34  coaxially connects the lower flex shaft housing  32  to the upper flex shaft housing  36 . A flex shaft  31  is shown provided within the pumping system  24  extending from the lower to the upper flex shaft housing  32 ,  36 . 
         [0024]    The pump section  38  of  FIG. 2  comprises a progressing cavity pump having a rotor  40  and a stator  42 . The rotor  40  outer dimensions correspond in shape and profile to the stator  42 . The rotor  40 , which preferably comprises metal, has an exterior helical configuration and splined lower end. The rotor  40  is configured to rotate within the stator  42 , wherein the stator  42  is preferably formed from an elastomeric material. The stator  42  is shown having double helical cavities located along its axis through which the rotor  40  rotates. Rotation of the rotor  40  therefore progressively urges production fluid axially up within the housing  39  and on to the pump discharge. The rotor  40  connects to the flex shaft  31  on one end so that rotating the flex shaft  31  drives the rotor  40 . As discussed in more detail below, the flex shaft  31  is driven by a pump motor. A centralizer  44  is shown provided in the pumping system  24  proximate to its upper end. The centralizer  44  includes a plurality of outwardly extending bowed elements for coaxially aligning the pumping system  24  within the tubing. The method and apparatus disclosed herein may include a centrifugal pump in place of or addition to a progressing cavity pump. 
         [0025]      FIGS. 3   a  and  3   b  are side cross sectional views of a lower portion of the insertable pumping system  24  of  FIG. 2 . Shown in  FIG. 3   a , the mandrel assembly  34  comprises a locking mandrel  46 , locking fingers  48 , and a seating cone  50 . The locking mandrel  46  is a generally annular structure having external threads on both of its ends. Engaging threads on a mandrel  46  end with threads on the lower flex shaft housing  32  shown in  FIG. 3   b . A threaded connection  47  couples the mandrel  46  and lower flex shaft housing  32 . Engaging threads on the mandrel  46  end opposite the threaded connection  47  with threads on the upper flex shaft housing  36  forms a threaded connection  55  coupling the mandrel  46  to the upper flex shaft housing  36 . 
         [0026]    An annular base  51  circumscribes a portion of the mandrel  46 . Corresponding threads on the mandrel  46  outer surface and base  51  inside are engaged to form a threaded connection  49  that couples the base  51  to the mandrel  46 . The locking fingers  48  extend from the annular base  51  toward the upper flex shaft housing  36  shown aligned generally parallel with the housing axis  45 . The fingers  48  terminate to form a free end  52  on the end of the locking fingers  48  opposite the base. The locking mandrel  46  outer diameter transitions outward to form a profile  53 , where the profile  53  outer diameter is greater than the outer diameter of mandrel  46  portion circumscribed by the fingers  48 . The space between the profile  53  and free ends  52  defines a void  57  circumscribing the mandrel  46 . 
         [0027]    The seating cone  50  is annularly disposed around the mandrel  46  and adjacent the upper portion of the profile  53 . The seating cone  50  has a generally ring like structure, wherein its outer diameter is illustrated as increasing with distance away from the profile  53  then remaining constant. The seating cone  50  end opposite the profile  53  is adjacent the upper flex shaft housing  36 . The profiled section of the seating cone  50  forms a leading edge  54  disposed at an angle to the axis  45  of the pumping system. 
         [0028]    Provided in a side cross sectional view of  FIG. 4  is an illustration of a tubing crossover  56  shown formed on a lower end of production tubing  76 . The tubing crossover  56  includes a sealing assembly  64 , an intake nipple  62 , an engaging receptacle  58 , and an intake coupling  59 . The intake coupling  59  is disposed within the engaging receptacle  58  and shown coupled to a motor driven shaft  61  and configured to receive the coupling  28  ( FIG. 3   b ). A pump motor  85  is shown coupled to the crossover  56  to provide rotational energy for driving the pumping system  24 . A seal  84  is also provided for equalizing pump motor  85  internal pressure with ambient pressure. Thus for connecting to a pump motor, the lower end of the engaging receptacle  58  is flanged for connection to the seal  84  and pump motor  85 . An optional gear reducer (not shown) may be included between the seal  84  and the pump motor  85 . The intake nipple  62  is threadingly connected on one end to the engaging receptacle  58  ( FIG. 4   b ) and on its opposite end to the seal assembly  64 . Apertures  63  are provided on the intake nipple  62  for enabling passage of wellbore fluid into the tubing crossover  56 . 
         [0029]    In the embodiment of  FIG. 4   a , the seal assembly  64  is shown integral within the tubing string  76  and connected to the string  76  lower end and the tubing crossover  56  upper end. In the embodiment shown the seal assembly has a lower seating nipple  66  (or mandrel), an upper seating nipple  70  (or mandrel), and a seating ring  74 . The lower seating nipple  66  has a generally annular configuration and is threaded on the outer circumference of its lower end. Corresponding threads are formed on the inner diameter of the upper end of the intake nipple  62 . Mating the threads of the intake nipple  62  with those of the lower seating nipple  66  forms a threaded connection  67  thereby connecting these two members. Optionally, as illustrated, the lower seating nipple  66  wall thickness is greater than the intake nipple  62  wall thickness. The thickness difference forms a reduced inner diameter in the region along the axis  45  surrounded by the seal assembly  64 . 
         [0030]    The upper seating nipple  70  includes two sections, where one of the sections has a smaller outer diameter and is threaded on its outer surface. The lower seating nipple  66  has an end with threads on its inner surface engaging the threaded surface on the upper seating nipple  70  to form a threaded connection  71 . A profile  68  is provided on the lower seating nipple  66  inner circumference spaced inward from the threaded connection  71 . A seating ring  74  is shown disposed between the profile  68  and an abutment  72  along end of the upper seating nipple  70  end. The combination of the abutment  72  and the profile  68  creates a generally rectangular space in which the seating ring  74  is disposed. Tightly coupling the lower seating nipple  66  to the upper seating nipple  70 , the threaded connection  71  secures the seating ring  74  between these two members. 
         [0031]    As shown, the seating ring  74  inner diameter is less than the lower and upper nipple  66 ,  70  inner diameters. The seating ring  74  smaller inner diameter forms a protrusion extending inside the tubing string  76  having coplanar upper and lower sides  73 ,  77  extending inward respectively from the upper seating nipple  70  and the lower seating nipple  66 . The upper and lower sides  73 ,  77  are connected by an inner surface  79  to form an abutment shoulder protruding within the tubing string  76 . Optionally, the seating ring inner surface  79  is profiled adjacent the upper side  73  to conform to the seating cone leading edge  54 .  FIG. 4   b  further illustrates an intake coupling  59  within the engaging receptacle  58 ; the intake coupling  59  is driven by the motor  85  through its coupling with motor driven shaft  61 . A seal section  84  is schematically depicted disposed between the motor  85  and the engaging receptacle  58 . 
         [0032]      FIGS. 5   a - 5   c  show in a side sectional view an embodiment of a completed assembly  78  of a pumping system  24  disposed within a tubing crossover  56 . Forming the completed assembly  78  requires applying a latching force to squeeze the locking fingers  48  axially through the smaller diameter of the seating ring  74 . Those skilled in the art can determine and apply a latching force without undue experimentation. As the locking fingers  48  engage the seating ring  74  they are pushed radially inward toward the axis  45  and snap radially outward when urged past the seating ring  74 . A spring force inherent in the locking fingers  48  pushes the fingers  48  outward so they abut the seating ring  74  lower edge and create contacting engagement for latching the pumping system  24  to the tubing string  76 . 
         [0033]    With reference now to  FIG. 5   b , the pumping system  24  and tubing crossover  56  components are dimensioned to ensure the free ends  52  provide an axial force on the seating ring  74  when installed. The axial force sealingly engages the seating ring  74  with the seating cone  50 . Moreover, the seating cone  50  profiled edge  54  sealingly mates with the similarly profiled edge on the seating ring  74 . Decoupling the pumping system  24  and the tubing string  76  is accomplished by applying a pulling force onto the pumping system  24  to uncouple the latch, determining and applying a decoupling force is also within the capabilities of those skilled in the art. 
         [0034]    The sealing engagement between the seating cone  50  and the seating ring  74  isolates the intake  32  of the pumping system  24  from the pump discharge. An advantage of the system disclosed herein is a pressure seal can be formed substantially concurrent with pump insertion into a tubular member, such as the production tubing  76 . An additional advantage of the system disclosed is the combination of the seating cone  50  and the seating ring  74  can receive at least a portion of axial forces produced during pumping, such as the pump shaft thrust. The downward coupling of the pumping system  24  with the tubing installation  56  provides additional mechanical connectivity of the flex shaft  31  and coupling  28  ( FIG. 3   a ) with the intake coupling  59  establishing a power path from the motor  85  to the pump  38 . In the embodiment of  FIG. 5   c , tabs on the pump section  38  lower end mates with profiles provided in the receptacle  58 . The tabs cooperate with the profiles can prevent the pump section  38  from rotating during operation. Further, the downward installation secures the pumping system engaging base  30  ( FIG. 3   a ) within the tubing crossover engaging receptacle  58  establishing mechanical connectivity between the external elements of the pumping system  24  and the tubing deployed system. This mechanical connectivity also links the pump stator  42  to the receptacle  58 . 
         [0035]    It is to be understood that the invention is not limited to the exact details of construction, operation, exact materials, or embodiments shown and described, as modifications and equivalents will be apparent to one skilled in the art. For example, embodiments exist where the downward facing shoulder engaged by the free ends of the fingers is a dedicated element apart from the seal ring. In the drawings and specification, there have been disclosed illustrative embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. Accordingly, the invention is therefore to be limited only by the scope of the appended claims.