Abstract:
A system and method is provided for pumping fluid. A pump incorporates composite components that provide a high degree of formability while maintaining wear resistance for use in potentially abrasive environments. The composite components may comprise one or more impellers and/or one or more diffusers.

Description:
BACKGROUND 
   In a variety of environments, such as wellbore environments, pumps are used to produce or otherwise move fluids. For example, multiple stage, centrifugal pumps are used in the production of oil. A centrifugal pump is connected into an electric submersible pumping system located, for example, in a wellbore drilled into an oil-producing formation. The centrifugal pump uses a plurality of stages with each stage having an impeller and a diffuser. The impellers are rotated by a shaft to move the fluid, while the diffusers guide the flowing fluid from one impeller to the next. 
   The fluid can contain particulate matter, such as sand, having abrasive properties. As the fluid flows through the pump, the particulate matter can abrade pump components, potentially shortening the life of the pump. Certain components, such as impellers and diffusers, are particularly susceptible to abrasion during operation of the pump. 
   SUMMARY 
   In general, the present invention provides a system and method that facilitates the pumping of fluids, such as fluids found in a subterranean formation. A pump utilizes pump components that are readily formed to enable the improvement of various pumping parameters, such as pumping efficiency. However, the structure of the pump components enables maintenance of high wear resistance for use in abrasive environments. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Certain embodiments of the invention will hereafter be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and: 
       FIG. 1  is a front elevational of view of a submersible pumping system having a pump, according to an embodiment of the present invention; 
       FIG. 2  is a partial cross-sectional view of an embodiment of the pump illustrated in  FIG. 1 ; 
       FIG. 3  is a cross-sectional view of a portion of the impeller utilized in the pump illustrated in  FIG. 2 ; 
       FIG. 4  is a cross-sectional view of an embodiment of the impeller illustrated in  FIG. 2 ; and 
       FIG. 5  is a cross-sectional view of an embodiment of a diffuser utilized in the pump illustrated in  FIG. 2 . 
   

   DETAILED DESCRIPTION 
   In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those of ordinary skill in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible. 
   The present invention generally relates to a system and method for pumping fluids. The system and method are useful with, for example, a variety of electric submersible pumping systems. However, the devices and methods of the present invention are not limited to use in the specific applications described herein to enhance the understanding of the reader. 
   Referring generally to  FIG. 1 , an example of an electric submersible pumping system  10  is illustrated. Although system  10  can be utilized in numerous environments, one type of environment is a subterranean environment in which system  10  is located within a wellbore  12 . Wellbore  12  may be located in a geological formation  14  containing fluids, such as oil. In certain applications, wellbore  12  is lined with a wellbore casing  16  having perforations  18  through which fluid flows from formation  14  into wellbore  12 . 
   In the embodiment illustrated, system  10  comprises a pump  20  having a pump intake  22 . System  10  further comprises a submersible motor  24  and a motor protector  26  disposed between submersible motor  24  and submersible pump  20 . System  10  is suspended within wellbore  12  by a deployment system  28 . Deployment system  28  may comprise, for example, production tubing, coiled tubing or cable. A power cable  30  is routed along deployment system  28  and electric submersible pumping system  10  to provide power to submersible motor  24 . 
   In the illustrated example, submersible pump  20  is a centrifugal pump having one or more stages  32 , as illustrated in  FIG. 2 . In the example illustrated in  FIG. 2 , only some of the stages  32  are illustrated to facilitate explanation. Submersible pump  20  also comprises an outer housing  34  that is generally circular in cross-section and extends between a first end  36  and a second end  38 . A shaft  40  is rotatably mounted with an outer housing  34  generally along an axis  42  of pump  20 . 
   Each stage  32  comprises a diffuser  44  and an impeller  46 . Generally, impellers  46  rotate with shaft  40  and may be rotationally affixed to shaft  40  by, for example, a key and keyway. The rotating impellers  46  impart motion to fluid flowing through pump  20  and move the fluid from one stage  32  to the next until the fluid is discharged through flow passages  48  at first end  36 . The diffusers  44  are rotationally stationary within outer housing  34  and serve to guide the fluid from one impeller  46  to the next. 
   As illustrated best in  FIG. 3 , each impeller  46  comprises an impeller portion  50  formed from a moldable material  52 . Moldable material  52  may comprise a moldable plastic material. In some applications, for example, the moldable material  52  comprises and arlene sulfide polymer, such as polyphenylene sulfide (PPS). PPS enables the formation of impeller portion  50  with a high degree of accuracy of form and smoothness of surface. These properties facilitate the formation of impellers  46  according to a wide variety of design objectives. For example, flow characteristics are readily optimized to enhance pumping efficiency or other pumping parameters. 
   In the embodiment illustrated in  FIG. 3 , impeller  46  comprises a central section  54 , such as a short hub, having an axial opening  55  therethrough. Axial opening  55  is sized to receive shaft  40 , such that impellers  46  may be stacked along the shaft. The impeller may be held in place rotationally with respect to shaft  40  by a key (not shown) received in a keyway  56  formed along the interior of short hub  54 . If central section  54  is formed as a short hub, the short hub is axially shortened in the sense that moldable material  52  does not extend axially into the diffuser hub of the next sequential diffuser, a location susceptible to wear due to abrasion. In the example illustrated in  FIG. 3 , central section  54  is formed as a short hub. 
   As illustrated, a plurality of vanes  57  extend radially outward from short hub  54 . In this embodiment, vanes  57  also are formed from moldable material  52  and integrally molded with short hub  54 . Each of the vanes  57  includes an internal flow passage  58  through which fluid flows in the direction of arrow  60  during operation of pump  20 . The fluid is directed through corresponding flow passages of the next sequential diffuser, as explained more fully below. 
   Each impeller  46  further comprises a sleeve  62 , as illustrated best in  FIG. 4 . Each sleeve  62  is positioned axially adjacent its corresponding short hub  54  such that it extends into the hub of the next adjacent diffuser (see  FIG. 2 ). Thus, sleeve  62  serves as an axial extension of short hub  54 , extending into an area susceptible to wear. Accordingly, sleeves  62  are formed from a wear resistant material relative to moldable material  52 . For example, sleeves  62  may be formed of a metal material less susceptible to abrasion than moldable material  52 . One material that provides good abrasion resistance is a nickel cast iron, such as a ni-resist material. Each sleeve  62  may be formed as a separate component within the impeller  46 . Alternatively, the sleeve may be attached to or molded with the moldable material  52 . 
   In the embodiment illustrated, sleeve  62  is generally circular and has an opening  64  sized to slide over shaft  40 , similar to short hub  54 . Additionally, each sleeve  62  may have a keyway  66  that cooperates with a key along shaft  40  to prevent rotation of sleeve  62  with respect to the shaft. The wear resistant sleeve  62  provides radial support for the impeller and increases bearing and pump life, especially when pumping fluids with substantial particulate content. 
   The impeller  46  also may comprise a thrust ring  68  disposed between the impeller  46  and the next adjacent diffuser. The thrust ring is disposed on a side of impeller  46  opposite sleeve  62 . Thrust ring  68  may be formed of a metal material or other wear resistant material. 
   Referring generally to  FIG. 5 , an embodiment of diffuser  44  is illustrated. In this embodiment, diffuser  44  is a composite diffuser in which a portion  70  of the diffuser is formed from a moldable material  72 . The moldable material  72  facilitates formation of diffuser designs that enhance pumping characteristics, such as pumping efficiency, similar to that described above with respect to impellers  46 . Moldable material  72  may be a moldable plastic, such as an arlene sulfide polymer. For example, PPS is a material that is readily moldable and can be formed with a smooth surface texture to enhance flow characteristics 
   The illustrated diffuser  44  also comprises a reinforcement member  74  able to reinforce moldable material  72 . For example, reinforcement member  74  may comprise a ring  76  disposed circumferentially along a radially outlying region  78  of diffuser  44 . Ring  76  comprises a plurality of gripping features  80  that hold ring  76  in place with respect to moldable material  72 . For example, gripping features  80  may comprise perforations formed through ring  76 , as illustrated. In the embodiment of  FIG. 5 , reinforcement member  74  is integrally molded with moldable material  72 , and thus is fixed in place along radially outlying region  78  of the diffuser. Furthermore, ring  76  may be formed of a metal material, such as nickel cast iron, e.g. ni-resist, or stainless steel. 
   Diffuser  44  comprises a hub portion  82  having an axial opening  84  sized to rotatably receive sleeve  62  of the next adjacent impeller  46 . A diffuser body portion  86  extends from hub portion  82  to radially outlying region  78 . Body portion  86  has a plurality of diffuser flow passages  88  for directing fluid in the direction of arrows  90  as the fluid moves from an upstream impeller to the next sequential downstream impeller. Each diffuser  44  also may comprise a bearing sleeve  92  disposed along the interior of hub portion  82 . Bearing sleeve  92  may be formed of a wear resistant material, such as a metal material, e.g. ni-resist or stainless steel. As illustrated, bearing sleeve  92  has a plurality of external gripping features, e.g. protuberances  94  that extend radially outward into the moldable material  72  of hub portion  82 . These features secure bearing sleeve  92  within diffuser  44 . Bearing sleeve  92  provides a wear resistant material in which sleeve  62  of the next adjacent impeller  46  rotates during operation of pump  20 . Bearing sleeve  92  also can serve as a second reinforcement member to structurally reinforce diffuser  44 . 
   The composite diffuser  44  enables, for example, greater accuracy of form and smoothness of surface due to moldable material  72 . Simultaneously, reinforcement member  74  provides added strength to resist mechanical loads and pressure loads. It should be noted that reinforcement member  74  may have other configurations or be formed of other materials. For example, the member may be formed of wire mesh or be formed as single or multiple reinforcement components disposed along radially outlying region  78  and/or along body portion  86  or hub portion  82 . 
   Although only a few embodiments of the present invention have been described in detail above, those of ordinary skill in the art will readily appreciate that many modifications are possible without materially departing from the teachings of this invention. Accordingly, such modifications are intended to be included within the scope of this invention as defined in the claims.