Patent Publication Number: US-6907925-B2

Title: PC pump inlet backwash method and apparatus

Description:
FIELD OF THE INVENTION 
   The present invention relates to downhole moineau pump assembly used on producing oil wells. 
   BACKGROUND OF THE INVENTION 
   A downhole moineau pump assembly used on a producing oil well consists of a stator, a rotor that extends through the stator, and a surface mounted top drive unit that rotates the rotor. The rotor and stator sealingly engage each other at spaced intervals to form a series of annular spaces. As the rotor rotates, fluids are drawn through an inlet and up the series of annular spaces between the rotor and the stator. 
   In oil wells with high solids content, the downhole moineau pump assembly periodically ceases to function due to a build up of solids blocking the inlet. 
   SUMMARY OF THE INVENTION 
   What is required is a downhole moineau pumping assembly which has means for reducing or eliminating solids accumulations blocking the inlet. 
   According to the present invention there is provided a downhole moineau pump assembly which includes a stator with a rotor extending through the stator. The rotor and stator sealingly engage each other at spaced intervals to form a series of annular spaces. A primary inlet is provided for fluids to enter a first of the series of annular spaces. A surface mounted top drive unit rotates the rotor. As the rotor rotates, fluids are drawn through the primary inlet and up the series of annular spaces between the rotor and the stator. A portion of the rotor is hollow with a central flow passage extending from a secondary inlet spaced from the primary inlet to the primary inlet. Means is provided for diverting a portion of the fluids being pumped to surface into the secondary inlet and pumping them under pressure down the central flow passage of the rotor to the primary inlet thereby washing accumulated solids from the primary inlet. 
   With the downhole moineau pump assembly, as described above, a portion of the fluids being pumped to surface are diverted through the secondary inlet and pumped under pressure down the central flow passage of the rotor to wash solids away from the primary inlet. This continual washing of solids away from the primary inlet reduces, if not eliminating entirely, blockages of the primary inlet due to accumulated solids. 
   There are various technologies suitable for use in pumping them under pressure down the central flow passage of the rotor to the primary inlet to achieve the desired washing action. Beneficial results have been obtained through the use of an “orbiting” drive in which the secondary inlet has a plurality of radially extending forwardly angled vanes. As the rotor rotates the rotary motion of the vanes exert pressure to direct fluids into the secondary inlet. This form of orbiting drive is preferred as it does not need a separate power source. The rotational motion of the rotor is converted by the vanes of the orbiting drive into a pumping force. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein: 
       FIG. 1  is a side elevation, in section, of a downhole moineau pump assembly constructed in accordance with the teachings of the present invention. 
       FIG. 2  is a top plan view, in section, of the orbiting drive of the downhole moineau pump assembly illustrated in FIG.  2 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The preferred embodiment, a downhole moineau pump assembly generally identified by reference numeral  10 , will now be described with reference to  FIGS. 1 and 2 . 
   Structure and Relationship of Parts: 
   Referring to  FIG. 1 , pump assembly  10  includes a stator  12 . A rotor  14  extends through stator  12 . Rotor  14  and stator  12  sealingly engaging each other at spaced intervals to form a series of annular spaces  16 . A primary inlet  18  is provided for fluids to enter a first of series of annular spaces  16 . A surface mounted top drive unit  20  rotates rotor  14  such that, as rotor  14  rotates, fluids are drawn through primary inlet  18  and up series of annular spaces  16  between rotor  14  and stator  12 . A portion of rotor  14  is hollow with a central flow passage  22  extending from a secondary inlet  24  spaced from primary inlet  18 , to primary inlet  18 . 
   An orbiting drive  26  is provided for diverting a portion of fluids being pumped up through series of annular spaces  16  into secondary inlet  24  and pumping them under pressure down central flow passage  22  of rotor  14 . Fluids exit central flow passage through high pressure nozzle  28  that is proximate to primary inlet  18 . 
   Referring to  FIG. 2 , orbiting drive  26  has a peripheral wall  30  which defines secondary inlet  24 . Orbiting sub  26  has a plurality of radially extending forwardly angled vanes  32 , such that as rotor  14  rotates, the rotary motion of vanes  32  exert pressure to direct fluids through ports  34  in wall  30  in orbiting drive  26  and into secondary inlet  24 . 
   Operation: 
   The use and operation of downhole moineau pump assembly generally identified by reference numeral  10 , will now be described with reference to  FIGS. 1 and 2 . Referring to  FIG. 1 , downhole moineau pump assembly  10  is provided as described above. As rotor  14  rotates, fluids are drawn through primary inlet  18  and up series of annular spaces  16  between rotor  14  and the stator  12 . Referring to  FIG. 2 , rotary motion of vanes  32  exerts pressure to direct fluids through ports  34  and into secondary inlet  24 . Referring to  FIG. 1 , fluids pumped under pressure down central flow passage  22  of rotor  14  and out through high pressure nozzle  28  serve to wash solids away from primary inlet  18  to reduce or eliminate blockages of primary inlet  18  due to accumulated solids. 
   The form of orbiting drive  26  in the illustrated embodiment is preferred as it does not need a separate power source. The rotational motion of rotor  14  is converted by vanes  32  of orbiting sub  26  into a pumping force. 
   In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
   It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.