Abstract:
The present invention provides an electric submersible pump assembly with a latch device permitting downhole connecting and disconnecting of the pump and motor. The latch device includes a pump latch connector and a motor latch connector that allows a pump and an electric submersible motor to be disposed in a wellbore independently and then connected. The pump latch connector attaches to the pump and includes a rotor connector box and a stator connector pin. The motor latch connector attaches to the motor and includes a rotor connector pin and a stator connector box. The rotor connector pin is disposable in the rotor connector box and the stator connector pin is disposable in the stator connector box thus connecting the previously suspended motor and motor latch connector to a retrievable pump, with the pump latch connector attached.

Description:
RELATED APPLICATIONS 
     This application claims priority to Provisional Application Ser. No. 60/292,724 entitled “Electric Submersible Motor and Progressive Cavity Pump Assembly” filed May 21, 2001. 
    
    
     FIELD OF INVENTION 
     The present invention relates to the field of submersible pump assemblies, and more particularly but not by way of limitation, to an in situ separable electric submersible pump assembly with a latch device. 
     BACKGROUND OF THE INVENTION 
     In oil wells and the like from which the production of fluids is desired, a variety of fluid lifting systems have been used to pump the fluids to surface holding and processing facilities. It is common to employ various types of downhole pumping systems to pump the subterranean formation fluids to surface collection equipment for transport to processing locations. 
     One such prior art pumping system is a submersible pumping assembly which is supported immersed in the fluids in the wellbore. The submersible pumping assembly has a pump and motor to pressurize and pass the reservoir fluids through production tubing to a surface location. 
     In straight and deviated wells, equipped with seven inch or larger casing, the installation of a submersible pump is known. An existing electric submersible motor—progressive cavity pump installation, by way of example, may consist of the following installation sequence from the bottom of the well to the surface: an electric submersible motor pressure sensing device; an electric submersible motor; an electric submersible motor seal section; a motor gear section; a motor service section which attaches to the stator adapter and a left-hand threaded rotor adapter of the pump with an outside diameter of a three and one half inches. The pump can be attached to a two and seven eighth inch outside diameter EUE tubing and to a tubing adapter with an optional check and bleeder valve. A flat motor cable is also attached to the motor and is spliced to a power cable that runs to the surface along with the tubing. After the tubing is landed and the well sealed off from the surface, the motor cable is connected to a switchboard or variable speed converter and the motor is energized so that the pump will operate as required. 
     The typical electric submersible pump assembly that includes a submersible pump, an electric motor and a connection interdisposed between the pump and the motor uses the connection to allow the pump and motor to be placed in the hole and be removed from the well without separating. Prior art connections have not proved effective in preventing fishing jobs or time consuming workover jobs. Currently the whole electric submersible pump assembly must be pulled out of the hole and run back in whenever a pump failure occurs, such as when a stator or rotor must be changed. 
     There is a need in the industry for an electric submersible pump assembly that will allow the pump rotor or stator to be changed without pulling the motor. Such a system would decrease costs and time associated with workovers. 
     SUMMARY OF THE INVENTION 
     The present invention provides an electric submersible pump assembly with a latch device that includes a pump latch connector and motor latch connector that allows a pump and an electric submersible motor to be placed in the wellbore independently and then connected. The pump latch connector attaches to the pump and includes a rotor connector box and a stator connector pin. The motor latch connector attaches to the motor and includes a rotor connector pin and a stator connector box. The rotor connector pin is disposable in the rotor connector box and the stator connector pin is disposable in the stator connector box thus connecting the previously suspended motor and motor latch connector to the retrievable pump and attached pump latch connector. 
     The advantages, benefits and features of the present invention will become clear from the following detailed description and drawings when read in conjunction with the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a semi-diagrammatical, elevational view of an electric submersible pump assembly constructed in accordance with the present invention. 
     FIG. 2 is an elevational view of latch device components of the electric submersible pump assembly of FIG.  1 . 
     FIG. 3 is an elevational view of a rotor connector pin of the electric submersible pump assembly of FIG.  1 . 
     FIG. 4A is an elevational view of a stator connector pin of the electric submersible pump assembly of FIG.  1 . 
     FIG. 4B is a projected end view of a stator connector pin of.the electric submersible pump assembly of FIG.  1 . 
     FIG. 5 is a partial cross-section elevational view of a rotor connector box of the electric submersible pump assembly of FIG.  1 . 
     FIG. 6A is a partial cross-section elevational view of a stator connector box of the electric submersible pump assembly of FIG.  1 . 
     FIG. 6B is the projected end view of the stator connector box of the electric submersible pump assembly of FIG.  1 . 
     FIG. 7 is a partially cutaway, cross-sectional, elevational view of the assembled and coupled latch device of FIG.  2 . 
    
    
     DESCRIPTION 
     Referring to the drawings, and more particularly to FIG. 1, shown therein is an electric submersible pump assembly  10 , sometimes also referred to as an ESP assembly. The electric submersible pump assembly  10  has, as arranged from bottom to top, a motor assembly  12  including a motor service section  14 , a latch device  16 , a pump  18 , production tubing  20 , and a packer  21 . The motor assembly  12  has an electric submersible motor  22  with possible attachments, such as a seal section, gear section and sensing devices that are well known by those skilled in the art. The electric submersible pump assembly  10  is placed in a wellbore  24  below ground level or surface  26  and extending through a reservoir, also known as the production zone  28 . The latch device  16  includes a pump latch connector  30  and a motor latch connector  32 . 
     FIG. 2 shows the pump latch connector  30  of the latch device  16  connected to a rotor  34  and a stator  36  of the pump  18 . The pump latch connector  30  includes a stator connector pin  38  and a rotor connector box  40 . A stator coupling  42 , with internal right-hand box threads, attaches the stator connector pin  38  to the stator  36 . A rotor coupling  44 , with left-hand threads, attaches the rotor connector box  40  to the rotor  34 . 
     FIG. 2 also shows the motor latch connector  32  which includes a rotor connector pin  46  and a stator connector box  48 . The motor service section  14  is bolted to the stator connector box  48 . The rotor connector pin  46  attaches to the motor shaft  49  of the motor service section  14  with left-hand threads  50 . The pump latch connector  32  can be placed in the wellbore, with the motor assembly  12  using motor tubing  52  that can be non-upset (EUE) motor tubing  52 , and a tubing collar, not separately designated in FIG. 1 wherein is shown a power cable  54  attached to the motor tubing  52 . 
     FIG. 3 shows the rotor connector pin  46  having a device body  55  which includes a guide pin  56  on an upper end portion  57 , an easy-catch hex, involute spline member  58 , a lower end portion  60 , which can include a base which includes the external threads  50 . The easy-catch hex, involute spline member  58  is an engaging member that can be a locking means as well as a locating means. The rotor connector pin  46  screws into the motor shaft  49  of the motor service section  14  via the threads  50 . 
     FIG. 4A shows the stator connector pin  38  which has a device body  61  with a lower end portion  62 , external right-hand threads  63 , male easy-catch, hex spline members  64 , an upper end portion  65 , and grooves  66 . The device body  61  of the stator connector pin  38  defines a central cavity that is concentric on the longitudinal axis of the stator connector pin  38 . The male easy-catch, hex spline members  64 , that are engaging members, can be a locking means as well as a locating means. The stator connector pin  38  is joined to the stator coupling  42  via the threads  63  (see FIG.  2 ). Of course, the stator connector pin  38  could be connected in alternate ways, such as with a pin or by welding. 
     FIG. 4B shows the projected end view of the stator connector pin  38  with the threads  63  that connect with the box threads of the stator coupling  42  shown in FIG.  2 . The male easy-catch, hex spline members  64  and grooves  66  that interconnect with the stator connector box  48  are also shown. 
     FIG. 5 shows the device body  67  of the rotor connector box  40  with an involute female spline member  68 , a lower end portion  69 , a guide-shoe  70 , an upper end portion  71  and left-hand internal threads  72 . The involute female spline member  68 , which is an engaging member, can be a locking means as well as a locating means. The device body  67  of the rotor connector box  40  defines a central cavity  73  concentric thereto on the longitudinal axis of the rotor connector box  40 . The dimensions of the cavity  73  are determined to accept the rotor connector guide pin  56  (FIG.  2 ). FIG. 5 also shows the position of the rotor coupling  44 , with left-hand external threads  74 , as attached to the rotor connector box  40 . The threads  72 ,  74  connecting the rotor coupling  44  and the rotor connector box  40  must either be left handed, or specially tightened and spot welded together. This is necessary so that this joint does not unscrew during operation. 
     FIG. 6A shows the stator connector box  48  that has a device body  76 , an upper end portion  77 , easy-catch internal hex spline members  78 , grooves  79 , external tubing threads  80 , a lower end portion  81  and fastener openings  82 . The easy-catch internal hex spline members  78 , that are engaging members, can be a locking means as well as a locating means. The device body  76  of the stator connector box  48  defines a central cavity  83  concentric thereto on the longitudinal axis of the stator connector box  48 . The fastener openings  82  are spatially disposed to accept the fasteners  85  to attach the stator connector box  48  to the housing of the motor service section  14  (FIG.  2 ). 
     FIG. 6B shows a projected end view of the stator connector box  48  with fastener openings  82 , internal spline members  78  and internal grooves  79 . The spline members  64  and grooves  66  of the stator connector pin  38  engage with the internal spline members  78  and grooves  79  of the stator connector box  48  such that when engaged, the longitudinal axis of the stator connector pin  38  is coincident with the longitudinal axis of the stator connector box  48 . 
     FIG. 7 shows the assembled and coupled latch device  16 . As discussed above, the stator connector box  48  is attached to the housing of the motor service section  14  with the fasteners  85  and the rotor connector pin  46  screwed onto the motor shaft  49  of the motor service section  14 . Also the rotor connector box  40  is connected onto the pump rotor  34  with the rotor coupling  44 , and the stator connector pin  38  is secured to the stator  36  by being screwed into the stator coupling  42 . 
     In FIG. 7, the assembled latch device  16  is shown coupled having one common longitudinal axis. The rotor connector pin  46  is coupled in the central cavity  75  of the rotor connector box  40  such that the external involute spline members  58  of the rotor connector pin  46  have interlocated with the internal involute spline members  68  of the rotor connector box  40 . Also the spline members  64  of the stator connector pin  38  are located in the internal grooves  79  of the stator connector box  48 . 
     The assembled and coupled latch device  16  has a stationary assembly including the stator coupling  42 , stator connector pin  38 , stator connector box  48 , which with the stator  36  and the housing of the motor service section  14 , provide the engaged, stationary portion of the electric submersible pump assembly  10  (FIG.  1 ). The assembled and coupled latch device  16  also includes the rotor coupling  44 , rotor connector box  40 , rotor connector pin  46 , which with the pump rotor  34  and motor shaft  49 , provides the engaged rotating portion of the electric submersible pump assembly  10  that can freely rotate within the assembled and coupled stationary portion. 
     In the present invention, the externally threaded stator connector box  48  is connected into motor tubing  52 , which can be 4½ inch tubing for example, used to locate the motor assembly  12 , motor service section  14  and motor latch assembly  32  in the wellbore  24  near the production zone  28 . The pump  18  and pump latch connector  30  are shown placed in the tubing used to locate the motor assembly  12  and shown coupled with motor latch connector  32 . 
     As shown in FIG. 1, the motor assembly  12 , including the motor latch connector  32 , is placed in the wellbore  24  on the motor tubing  52  having the flat cable  54  attached but without the pump  18  attached. The motor assembly  12  and motor latch connector  32  are landed and the cable  54  is connected to a switchboard or variable speed controller  86 . 
     The pump  18 , for example a progressive cavity or centrifugal pump, with the pump latch connector  30  is lowered on coiled tubing or other suitable tubing, such as 2½ coil tubing or 2½ production tubing  20  for example, into the previously installed motor tubing  52 . As the pump  18  is lowered into the well, the guide pin  56  (FIG. 2) of the rotor connector pin  46  first contacts the guide-shoe  70  of the rotor connector box  40 . The guide pin  56  of the rotor connector pin  46  guides the rotor connector pin  46  into the rotor connector box  40  until the lower end portion  62  of the stator connector pin  38  contacts the upper end portion  77  of the stator connector box  48 . The male easy-catch, hex spline members  64  and grooves  66  of the stator connector pin  38  will interconnect with the internal hex spline members  78  and internal grooves  79  of the stator connector box  48 , thus helping to guide the rotor connector pin  46  into the rotor connector box  40 . 
     Finally, the external spline member  58  on the rotor connector pin  46  will interconnect with the involute female spline member  68  of the rotor connector box  40 , thereby allowing torque transfer through the rotor connector pin  46  and rotor connector box  40 . The well is then prepared for operation as one skilled in the art would currently prepare the well for production. It should be noted that the upper end portion  77  of the stator connector box  48  and the lower end portion  62  of the stator connector pin  38  cooperate to serve as sturdy guides, protecting the more closely spaced spline member  58  and spline member  68 ; these also serve as a stop to protect the spline members  58 ,  68  from being over run. 
     Once the production tubing  20  is in place and the motor cable  54  is connected to a switchboard or variable speed converter  86 , the pump  18  can then be energized by the motor  22  as required to operate the pump  18 . 
     An alternative procedure for setting the motor assembly  12  is to attach the motor tubing  52  with the motor assembly and the motor connector latch via a tubing collar (not shown) and locate the motor assembly  12  in the wellbore. The motor tubing  52  can be released if another device, such as a packer, is being used to hold the motor assembly  12  in place, or the motor tubing  52  can stay attached to the motor assembly  12  as described herein and hung from the packer  21  (FIG.  1 ). The motor tubing  52  can also be hung from the surface  26  as described above. 
     Referring to FIG. 1, a production stream  92  enters the wellbore  24  from the production zone  28  and flows to the electric submersible pump assembly  10 . The motor-powered pump  18  such as a progressive cavity which is well suited to this invention, is energized and the production stream  92  is drawn into the pump  18  and pumped thereby through the production tubing  20  to the surface  26 . If significant gas is present in the fluid stream, it can be advantageous to use a gas separator-type pump intake or other known methods to handle the gas expansion. 
     In the event that the pump  18  fails, or for some other reason must be replaced, the motor  22  is de-energized and the pump  18  and the pump latch connector  30  are released from the motor latch connector  32  by lifting the production tubing  20 , or other release technique well known in the art. Once release is achieved, the production tubing  20 , the pump  18  and the pump latch connector  30  are pulled out of the wellbore  24 . This allows such pump repairs as may be necessary to be completed and the pump  18  can then be placed back in the wellbore  24 . This is especially helpful at remote locations in conjunction with a coil tubing unit, such as in offshore wells drilled from a drilling platform that is no longer on location. The coil tubing can be used for the production tubing  20  and the pump  18  pulled by the coil tubing unit. The current invention is well adapted to many types of pumps, as one skilled in the art would be aware, such as the progressive cavity pump or centrifugal pumps mentioned above or other types of pumps that well known in the industry. 
     When the pump  18  is ready to be located back into the wellbore  24 , the pump  18  and attached pump latch connector  30  are placed in therein such as with coil tubing to couple with the motor assembly  12  and motor latch connector  32  that remained in the wellbore  24 . 
     If the motor  22  is to be pulled out of the wellbore  24 , the packer  21  and any other device holding the motor assembly  12  in the wellbore  24  must be released. The motor assembly  12  can be pulled after the pump  18  was removed. 
     It is clear that the present invention is well adapted to carry out the objects and to attain the ends and advantages mentioned as well as those inherent therein. While presently preferred embodiments of the invention have been described in varying detail for purposes of the disclosure, it will be understood that numerous changes can be made which will readily suggest themselves to those skilled in the art and which are encompassed within the spirit of the invention disclosed and as defined in the above text and in the accompanying drawings.