Abstract:
An electrical submersible well pump assembly has a motor containing a dielectric lubricant. A seal section is mounted to the motor for reducing pressure differential between the lubricant in the motor and the well bore fluid. The seal section has a head on an end opposite the motor. A pump assembly is mounted to the head of the seal section. An intake is located in the head of the seal section for drawing well bore fluid into the pump assembly.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates in general to electrical submersible well pumps, and in particular to connections between the seal section of the pump assembly and the pump. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electrical submersible well pumps are commonly used for hydrocarbon well production. A typical pump assembly has an electrical motor with a seal section or protector on its upper end. The motor is filled with a dielectric lubricant. The seal section has an equalizer in communication with that lubricant. The equalizer is also in fluid communication with the well bore fluid for equalizing the pressure of the lubricant to that of the well bore fluid. Typically the seal section will also have a thrust bearing for absorbing downward thrust from the pump. 
         [0003]    The pumping assembly may comprise one or more pumps and optionally a gas separator. The pumps are rotary pumps driven by a shaft of the motor. They may be either progressing cavity pumps or they may be centrifugal pumps having a large number of stages, each stage having an impeller and a diffuser. If a gas separator is employed, typically it has a rotary gas separating component for separating gas from the well fluid prior to the well fluid entering the pump. 
         [0004]    A different connector is required on the lower end of the pump depending upon whether the pump is to connect directly to a seal section or to another component of the pumping assembly, such as a gas separator or another pump. The connectors are not readily interchangeable between pumps, thus the manufacturer may be required to keep both types. The reason for having both types of pumps has to do with whether the connector has intake ports or not. If the pump is connecting to an upstream component such as another pump or a gas separator, its connector would not have intake ports in it. If connecting directly to the seal section, the connector would need intake ports. 
         [0005]    As further explanation of the prior art and referring to  FIG. 1 , pump  31  is a centrifugal pump having a number of stages, each stage having an impeller  33  and a diffuser  35 . Pump  31  has a connector  37  on its lower end for connecting to other components of the pumping assembly. Connector  37  has external threads  39  that connect to internal threads in the housing of pump  31 . Connector  37  has a flange  41  on its lower end containing a pattern of holes  43 , each for receiving a bolt  45 . Connector  37  does not have any intake ports leading directly to the exterior for drawing in well bore fluid. The reason is that pump  31  is constructed to be a tandem pump or one for connection to a gas separator below it. In those instances, the intake ports would be in lower connector of the lower tandem pump or in the lower connector of the gas separator. 
         [0006]    If the manufacturer wishes to use pump  31  without connecting it to an upstream component, such as another pump or gas separator, he can do so by connecting it to a separate intake housing  47 . Intake housing  47  is a separate sub that has intake ports  49  for well fluid to pass inward and up to pump  31 . Intake housing  47  has its own short shaft  51  mounted therein and which connects to pump shaft  53  by a coupling  55 . A radial bearing  57  supports intale shaft  51  in housing  47 . Radial bearing  57  does not form a seal. A coupling on the lower end of intake housing shaft  51  will connect it to a seal section shaft (not shown). Intake housing  47  has a radial flange  61  for bolting to the seal section (not shown). While combining pump  31  with intake housing  47  allows a manufacturer to use pump  31  either as a tandem pump or as a single pump without a gas separator, it requires extra expense because of intake housing  47 . 
         [0007]      FIG. 2  illustrates another prior art pump  63  having a pump shaft  65 . A connector  67  has upper exterior threads  69  for engaging mating threads in the interior of the housing of pump  63 . Connector  67  has intake ports  71  for drawing in well fluid to pump  63 . Connector  67  also has radial bearings or bushings  73  for supporting shaft  65 . Bearings  73  do not form a seal. A coupling  75  on the lower end of shaft  65  connects the shaft to the seal section shaft (not shown). Connector  67  also has a flange  77  for bolting directly to the seal section. 
         [0008]    Pump  63  is operable only by connecting it directly to the seal section. It cannot be used as a tandem pump because of its intake ports  71 . In addition, connectors  67  and  37  ( FIG. 1 ) cannot be interchanged. Shaft  65  protrudes farther than shaft  53  ( FIG. 1 ) because of the need for space for intake ports  71 . Consequently, to avoid the expense of having to use a separate intake housing  47 , an operator may choose to stock both types of pumps  31  and  63 . 
       SUMMARY OF THE INVENTION 
       [0009]    In this invention, the seal section between the motor and the pumping assembly has a head on its end with an intake. The intake draws well bore fluid into the pump. The pump assembly, whether it includes is a gas separator, multiple pumps, or a single pump, has a simple connector on its lower end without intake ports. Placing the intake in the head of the seal section allows a standard connector to be utilized on all of the pumps regardless of whether the pump is to be connected directly to the seal section or to an upstream component of the pumping assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an exploded sectional view of one prior art type of pump connector and an intake sub. 
           [0011]      FIG. 2  is a sectional view of another prior art type of pump connector. 
           [0012]      FIG. 3  is a schematic view of an electrical submersible pumping assembly constructed in accordance with this invention. 
           [0013]      FIG. 4A  is an enlarged sectional view of a seal section head and a lower portion of the pump of the assembly of  FIG. 3 . 
           [0014]      FIG. 4B  is a sectional view of a central portion of the seal section of the assembly of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIG. 3 , electrical submersible pumping assembly (ESP)  11  is shown suspended in a cased well  13 . ESP assembly  11  includes a motor  15 , which is normally located on the lower end of the assembly, but in some instances on an upper end. A seal section  17  connects to the upper end of motor  15 . Seal section  17  equalizes the pressure of lubricant within motor  15  to that of the well fluid in the well. 
         [0016]    Seal section  17  has a head  19  on its upper end. Head  19  forms a part of seal section  17  and has intake ports  21  for drawing well fluid into head  19 . ESP  11  may include an optional gas separator  23 , which connects to the upper end of seal section head  19 . Gas separator  23  separates gas from the well fluid flowing into intake  21  and discharges the gas out the gas outlet  25 . The liquid components flow upward to a pump  27  that connects to the upper end of gas separator  23 . Pump  27  may be a centrifugal pump or another type of rotary pump, such as a progressing cavity pump. Pump  27  is suspended by a string of tubing  29  through which the pump discharges. Gas separator  23  is employed only if conditions merit; in many instances pump  27  would connect directly to seal section head  19 . Another pump could optionally be connected to the upper end of pump  27  in a tandem arrangement. 
         [0017]    Referring to  FIG. 4A , pump  27  has a standard connector  79  on its lower end that is employed whether pump  27  connects directly to seal section  17 , to another pump, or to gas separator  23  ( FIG. 3 ). In  FIG. 4A , pump  27  is shown being directly connected to head  19  of seal section  17 . Connector  79  has exterior threads on its upper end that engage internal threads in the housing of pump  27 . Connector  79  has a flange  83  with a bolt pattern  85 . Connector  79  does not have intake ports to the exterior. 
         [0018]    Seal section head  19  has a flange  87  on its upper end that has a bolt pattern  89  that mates with bolt pattern  85 . Connector  79  thus attaches directly to seal section head  19 , if desired. A lower portion of connector  79  inserts into seal section head  19  and is sealed to seal section head  19  by a seal  90 . Seal section  17  has a cylindrical housing  91  with internal threads  93  at its upper end. Seal section head  19  has external threads  95  on a lower interior portion that extend into housing  91 . Threads  95  mate with threads  93  to secure head  19  to seal section housing  91 . A seal  97  seals head  19  to the interior of seal section housing  91 . 
         [0019]    Seal section head  19  has an axial passage  99  extending through it. Seal section  17  has a shaft  101  that extends through it. Shaft  101  extends upward through axial passage  99 . A bushing  103  in passage  99  radially stabilizes shaft  101 , but does not seal. A seal assembly  105  is located above bushing  103  for sealing shaft  101  to passage  99 . Seal assembly  105  may be a variety of types and combinations of seals. In this type, it includes a rotating member that rotates with shaft  101  and is urged by a spring against a stationary member. Seal assembly  105  seals a cavity  107  in head  19  from a cavity  109  in the interior of seal section  17 . Seal head cavity  107  is in fluid communication with well bore fluid because of intake ports  21 . Cavity  109  is in fluid communication with lubricant of motor  15  ( FIG. 3 ). Seal assembly  105  thus seals the lubricant from the well bore fluid. 
         [0020]    Pump  27  has a pump shaft  111  that extends downward a short distance below connector  79 . A coupling  113  connects pump shaft  111  to seal section shaft  101 . Coupling  113  is located within seal head cavity  107 . 
         [0021]    Seal section  17  ( FIG. 3 ) may be a variety of types and will normally have a thrust bearing (not shown) to absorb thrust imposed on its shaft  101  by pump  27 . In one example, as illustrated in  FIG. 4B , an equalizer bag  115  is located in housing  91 . Bag  115  is an elastomeric flexible container that has its upper and lower ends sealed around a central tube  117 . Tube  117  has ports  119  that communicate with an annular space between shaft  101  and tube  117 . The annular space is in communication with lubricant in motor  15  ( FIG. 3 ). Dotted lines in  FIG. 4A  illustrate schematically that central tube  117  extends upward to seal section head  19 , where it attaches and seals to provide a flow path for lubricant from motor  15  ( FIG. 3 ). 
         [0022]    Equalizer bag  115  has well fluid on its exterior so that it will equalize or at least greatly reduce any pressure difference between the motor lubricant and the well bore fluid. In this embodiment, a port  121  extends downward from the exterior of head  19  to the interior of seal section housing  91  to deliver well fluid to the exterior of bag  115 , as illustrated by the dotted lines in  FIG. 4A . Other types of seal sections are feasible. In another type (not shown), the equalizer comprises a labyrinth chamber rather than a flexible bag. The labyrinth chamber has U-tubes arranged to allow the well fluid and lubricant to contact each other, but prevent the heavier well fluid from flowing upward through the U-tubes and back downward into the motor. Some seal sections may employ multiple bags; others may employ multiple labyrinth chambers; and others may employ a combination of the two. 
         [0023]    In the operation of ESP  11 , in one mode, pump  27  is connected directly to seal section head  19 . When motor  15  is energized, well fluid will be drawn through intake ports  21  for being acted on by pump  27 . Seal section  17  protects the lubricant in the motor from contamination by the well bore fluid. Seal section  17  also equalizes the pressure of the lubricant to that of the well bore fluid. 
         [0024]    In another mode, as shown in  FIG. 3 , pump  27  with its connector  79  ( FIG. 4A ) would attach to the upper end of gas separator  23 . Gas separator  23  in that instance could have a connector that is substantially the same as connector  79  for connecting to seal section head  19 . The well fluid would flow into intake ports  21  of seal section head  19 , then to gas separator  23 . Pump  27  and its connector  79  could alternately be employed as an upper or middle tandem pump, in which case connector  79  would connect to the upper end of a lower pump, and the lower pump would connect to seal section head  19 . 
         [0025]    The invention has significant advantages. By placing the intake in the head of the seal section, connectors for the pumping assemblies may be standardized. The same pump could be used as a single, stand-alone pump, or one connected to a gas separator, or one connected to a lower tandem pump. 
         [0026]    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.