Patent Publication Number: US-11644039-B2

Title: Pump bottom bearing with temperature sensor in electrical submersible well pump assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to provisional application Ser. No. 62/842,233, filed May 2, 2019. 
    
    
     FIELD OF DISCLOSURE 
     The present disclosure relates to electrical submersible well pump assemblies (ESP), and in particular to a centrifugal pump having a temperature sensor mounted in a bottom bearing. 
     BACKGROUND 
     Electrical submersible pumps (ESP) are commonly used in hydrocarbon producing wells. An ESP includes a pump driven by an electrical motor. The pump is often a centrifugal pump having impellers rotated by a shaft assembly extending from the motor. 
     The rotating impellers cause a normal temperature increase during operation. If liquid well fluid ceases to flow into the pump stages while the impellers are still rotating, the pump stages may experience a rapid temperature increase. That can happen because of a mistakenly closed valve or a large gas bubble entering the pump. If the pump is operating at a much higher speed than conventional, or for a long period of time, the temperature can elevate high enough to cause serious damage, such as diffuser spin, unseated bushing inserts, and in extreme cases, fusing of the impellers to the diffusers. 
     It is known to employ temperature sensors at the discharge adapters of pumps to monitor the temperature of the well fluid as it discharges from the pump. Also, temperature sensors are commonly used to measure the temperature of the motor lubricant in the motor. 
     SUMMARY 
     An electrical submersible pump (ESP) for pumping well fluid from a well has a tubular pump housing with a longitudinal axis and a housing bore that is coaxial with the axis. A plurality of centrifugal pump stages are in the housing bore, each of the stages having an impeller and a diffuser. A rotatable shaft, mounted on the axis within the housing, rotates the impellers. The housing has a non-rotatable bearing with a passage through which the shaft extends. A sensor hole extends through the housing and into the bearing. A temperature sensor locates within the sensor hole. 
     In the embodiment shown, the bearing has a hub through which the passage extends. An outer wall coaxially extends around the hub and is spaced radially outward therefrom. A plurality of support arms extends from the hub to the outer wall. The sensor hole extends from one end of the bearing into one of the support arms. 
     The sensor hole may have a closed end spaced radially outward from the passage in the bearing. In the example shown, the sensor hole is inclined relative to the axis at an acute angle less than 90 degrees. The bearing is located in a bottom portion of the pump in the embodiment shown. 
     The ESP further comprises a motor and a seal section for sealing around a motor shaft, the seal section being between the motor and the pump. The housing comprises a cylindrical body and a base secured to a lower end of the body, the base having a connector for connecting the seal section to the pump. The bearing is located in the base. The sensor hole extends through the base into the bearing. 
     The ESP may also have a sensing unit located at one end of the ESP. A sensor line leads from the temperature sensor to the sensing unit. The sensing unit may comprise a motor gauge unit mounted to a lower end of a motor. The sensor line extends from the temperature sensor in the bearing to the motor gauge unit in one embodiment. 
     In the embodiment shown, the housing comprises a cylindrical body and a base having a threaded upper portion secured to a lower end of the body. The base has a base bore in which the bearing is mounted. The base has a connector flange with bolt holes for connecting the pump to a lower module of the ESP/A neck of smaller outer diameter than the upper portion and the connector flange defines a downward facing shoulder. The sensor hole has a sensor hole base portion extending upward and inward from the shoulder toward the axis. The sensor hole has a bearing portion aligned with the sensor hole base portion and extending within the bearing. A fitting secures the sensor line to the sensor hole base portion at the shoulder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic side view of an electrical submersible pump assembly having a pump housing with a temperature sensor in accordance with this disclosure. 
         FIG.  2    is an axial sectional view of lower portions of the pump of the ESP in  FIG.  1   . 
         FIG.  3    is top view of the bottom bearing of the pump of  FIG.  2   , shown removed from the pump. 
         FIG.  4    is a sectional view of the bottom bearing of  FIG.  3   , taken along the line  4 - 4  of  FIG.  3   . 
         FIG.  5    is a partially sectioned perspective view of the bottom bearing of  FIG.  3    shown within the base of the pump. 
     
    
    
     While the disclosure will be described in connection with the preferred embodiments, it will be understood that it is not intended to limit the disclosure to that embodiment. On the contrary, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the scope of the claims. 
     DETAILED DESCRIPTION 
     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 method and system of the present disclosure 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 thorough and complete, and will fully convey its scope to those skilled in the art. Like numbers refer to like elements throughout. In an embodiment, usage of the term “about” includes +/−5% of the cited magnitude. In an embodiment, usage of the term “substantially” includes +/−5% of the cited magnitude. 
     It is to be further understood that the scope of the present disclosure 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. In the drawings and specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for the purpose of limitation. 
       FIG.  1    illustrates a cased well  11  having an electrical submersible well pump (ESP)  13  of a type commonly used to lift hydrocarbon production fluids from wells. The terms “upward”, “downward”, “above”, “below” and the like are used only for convenience as ESP  13  may be operated in other orientations, such as horizontal. 
     ESP  13  has an electrical motor  15  coupled by a seal section  17  to a centrifugal pump  19 . Pump  19  has an intake port  20  that may be at the lower end of pump  19 , in a separate module, or in an upper part of seal section  17  as shown. If a gas separator (not shown) is employed, intake port  20  would be in the gas separator. 
     Motor  15  contains a dielectric motor lubricant for lubricating the bearings within. A pressure equalizer communicates with the lubricant in motor  15  and with the well fluid for reducing a pressure differential between the lubricant in motor  15  and the exterior well fluid. In this example, the pressure equalizer is contained within seal section  17 . Alternately, the pressure equalizer could be located below motor  15 , and other portions of seal section  17  could be above motor  15 . 
     A string of production tubing  21  extending downward from a wellhead (not shown) supports ESP  13 . Pump  19  discharges well fluid into production tubing  21 . Alternately, ESP  13  could be secured to a string of coiled tubing located within a production conduit. In that event, pump  19  would discharge into an annulus surrounding the coiled tubing within the production conduit. 
     In this example, a power cable  23  extends downward alongside production tubing  21  and has a motor lead on its lower portion that connects to motor  15 . If the ESP is installed on coiled tubing, the power cable would be inside the coiled tubing and the motor would normally be above the pump. 
     In this embodiment, a motor gauge unit  25  secures to the bottom of motor  15 . Motor gauge unit  25  has sensors for measuring parameters of the motor lubricant, such as pressure and temperature. Signals from motor gauge unit  27  may be transmitted to a controller adjacent the wellhead by a separate instrument wire or by superimposing those signals on the motor windings within motor  15  and up power cable  23 . 
     A discharge gauge unit  27  may be mounted to the upper end of pump  19 . Discharge gauge unit  27  has sensors that sense the discharge pressure of the well fluid being pumped by pump  19 . The signals from discharge gauge unit  27  may be transmitted down to motor gauge unit  25  on a signal line (not shown) for communication with the controller at the surface along with the signals from motor gauge unit  25 . Alternately, the signals from discharge gauge unit  27  could be transmitted up a separate instrument wire to the controller at the surface. 
     A pump temperature sensor line  29  extends from the lower portion of pump  19  along the exteriors of seal section  17  and motor  15  to motor gauge unit  25 . Alternately, pump temperature sensor line  29  could extend upward to discharge gauge unit  27 . Also, temperature sensor line  29  could extend directly to a controller at the surface adjacent the wellhead. Sensor line  29  could be a wire or fiber optic line. 
     Referring to  FIG.  2   , pump  19  has a tubular body or housing  31  with a longitudinal axis  33  and a coaxial bore  35 . A base  37 , which may be considered to be a part of housing  31 , secures by an upper threaded section  38  to the threads in the cylindrical portion of housing  31 . Base  37  has features to connect pump  19  to a next lower module, which in this instance is seal section  17 . In this example, the connector comprises an external flange  39  with bolt holes  40  for receiving bolts. A neck  42  extends upward from flange  39  to upper threaded section  38  and has a smaller outer diameter than the outer diameters of flange  39  and upper threaded section  38 . 
     A shaft  41  rotated by motor  15  ( FIG.  1   ) is mounted coaxially within housing  31 . Shaft  41  has a lower splined end for coupling to a shaft in seal section  17  ( FIG.  1   ), the coupling being indicated by the dotted lines. Pump  19  is a centrifugal type, having a large number of stages, each stage comprising a diffuser  43  and an impeller  45 . Diffusers  43  do not rotate relative to housing  31 . Shaft  41  rotates impellers  45  relative to housing  31 . 
     A non-rotating bottom bearing  47  below diffusers  43  and impellers  45  radially stabilizes shaft  41 . Bottom bearing  47  has flow channels  49  to enable the upward passage of well fluid. A similar top bearing (not shown) provides radial stabilization to the upper end of shaft  41 . Bottom bearing  47  locates within an upper portion of the bore in base  37  in this example. 
     A temperature sensor  51 , such as a thermocouple, fiber optic or other temperature sensing device, is located within bottom bearing  47 . A base sensor hole  53  extends inward and upward through the side wall of base  37  and aligns with a bearing sensor hole  55  in bottom bearing  47 . Temperature sensor  51  locates within bearing sensor hole  55 , and temperature sensor line  29  extends through base sensor hole  53  to temperature sensor  51 . Temperature sensor  51  and at least portions of temperature sensor line  29  may have a metal sheath. A conventional swage type fitting  57  secures by threads to base  37 , clamping temperature sensor line  29  in base sensor hole  53 . 
     Bottom bearing  47  has an axial bore with a shaft passage  60  defined by a non-rotating bushing  59 , which may be of a carbide material. Bushing  59  comprises a journal portion of bearing  47 . Shaft  41  will typically have a shaft sleeve  61  that is keyed to shaft  41  for rotation. Shaft sleeve  61  is in rotational sliding engagement with bottom bearing bushing  59 . Bearing sensor hole  55  has a closed end that is radially outward from bushing  59 . 
     Referring to  FIGS.  3  and  4   , bottom bearing  47  has a cylindrical outer wall  63  that coaxially surrounds a cylindrical inner wall or hub  65 . A number of support arms  67  (three shown) extend from hub  65  to outer wall  63 . The spaces between arms  67  define flow channels  49 . Arms  67  may be integrally formed with hub  65  and outer wall  63 . Arms  67  are located in radial planes from axis  33  in this example, and they are evenly spaced apart at 120 degree angles. Each arm  67  may have flat sides  68  that are parallel with each other. An axially extending slot  69  in outer wall  63  receives an anti-rotation pin (not shown). The anti-rotation pin engages a mating slot (not shown) in the bore of base  37  ( FIG.  5   ) to prevent rotation of bottom bearing  47  relative to base  37 . 
     Each arm  67  has an upper end  71  that may be rounded and recessed below the upper end of outer wall  63 . Each arm  67  has a lower end  73  that may be substantially flush with the lower end of outer wall  63 . The upper end of hub  65  may be substantially flush with each arm upper end  71 . The lower end of hub  65  is substantially flush with the lower end  73  of each arm  67  in this example. Bushing  59  is secured in the bore of hub  65  by a lower shoulder in the bore of hub  65  and a conventional retainer ring on  74  engaging the bore of hub  65  on the upper end bushing  59 . 
     Bearing sensor hole  55  extends into the lower end  73  of one of the arms  67  and has a closed upper end within arm  67  a short distance radially outward from bushing  59 . Bearing sensor hole  55  is in a plane parallel with and between the flat sides  68  of arm  67 . Bearing sensor hole  55  has a smaller diameter than the thickness of arm  67  measured from one side  68  to the opposite side  68 . In this example, bearing sensor hole  55  is located in a radial plane of axis  33 . Bearing sensor hole  55  extends upward and inward at an acute angle relative to axis  33  that is less than 90 degrees and is illustrated to be about 20 degrees. The closed upper end of bearing sensor hole  55  is closer to bushing  59  than to the exterior of outer wall  63 . 
     Referring to  FIG.  5   , bottom bearing  47  fits within a counterbore  75  of base  37 , landing on an upward-facing shoulder  76 . Bottom bearing  47  may be simply dropped in place, or secured to base  37  in various manners, such as by a press-fit. Alternately, bottom bearing  47  could be integrally formed with base  37 . 
     The upper end of base sensor hole  53  is separated from the lower end of bearing sensor hole  55  in this example by a short distance or gap  78  due to a conical band  77  extending downward from upward facing shoulder  76  in the bore of base  37 . However, it would be feasible to make the upper end of base sensor hole  53  flush with the lower end of bearing sensor hole  55 . Swage fitting  57  secures to a threaded hole  79  in base  37 . Threaded hole  79  extends upward and inward from a downward facing shoulder  81  at the upper end of base neck  42 . 
     In operation, as pump  19  operates, it will increase in temperature to a normal operating temperature. Liquid well fluid flowing through pump  19  will provide cooling for the components, including bottom bearing  47 . In the event pump  19  become gas locked, or a valve for the flowing well fluid is accidentally closed, the rotating shaft  41  could rapidly increase the temperature of bottom bearing  47 , causing damage to bottom bearing  47 . The spinning impellers  45  would also rapidly increase in temperature. It unchecked, impellers  45  could fuse to diffusers  43 . This rapid increase particularly occurs when pump  19  is operating at a much higher speed than a conventional speed. 
     Temperature sensor  51  will sense the temperature and send a signal over sensor line  29  to motor gauge unit  25 , which in turn transmits the signal to the controller adjacent the wellhead. In case of a rapid temperature increase, the controller will quickly take remedial action, such as slowing the speed of pump  19  or completely shutting it down. Locating temperature sensor  51  in bottom bearing  47  places it closer to the pump intake  20  than the diffusers  43  and impellers  45  so that it will encounter a rise in temperature due to a loss in liquid well fluid flow before the temperature rise occurs in diffusers  43  and impellers  45 . 
     The present disclosure described herein, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned, as well as others inherent therein. While one embodiment of the disclosure has been given for purposes of disclosure, numerous changes exist in the details of procedures for accomplishing the desired results. These and other similar modifications will readily suggest themselves to those skilled in the art, and are intended to be encompassed within the scope of the appended claims.