Downhole motor-pump assembly

Abstract

A downhole motor-pump assembly disposed within a tubular string includes a rotor and a stator. The rotor has a first rotor portion and a second rotor portion. The first rotor portion has a first geometrical shape and the second rotor portion has a second geometrical shape. The first geometrical shape differs from the second geometrical shape. The stator has a first stator section and a second stator section. The first stator section is spaced from the second stator section by a gapped region. The first rotor portion is located within the first stator section and the second rotor potion is located within the second stator section. The differing geometry causes a difference in displacement in the first and second sections per revolution of the rotor. Therefore the difference in displacement must be made up and is induced into the tool at the gap or drillings between sections, and this additional volume is effectively pumped.

What is claimed is: 
     
         1 . A downhole motor-pump assembly disposed within a tubular string, the motor-pump assembly comprising:
 a rotor, the rotor having a first rotor portion and a second rotor portion, the first rotor portion having a first geometrical shape and the second rotor portion having a second geometrical shape, the first geometrical shape differing from the second geometrical shape; and   a stator having a first stator section and a second stator section, the first stator section being spaced from the second stator section by a gapped region, wherein the first rotor portion is located within the first stator section and the second rotor portion is located within the second stator section.   
     
     
         2 . The downhole motor-pump assembly of  claim 1  wherein the rotor is configured such that the first geometrical shape displaces a first volume of fluid upon rotation of the rotor and the second geometrical shape displaces a second volume of fluid upon rotation of the rotor. 
     
     
         3 . The downhole motor-pump assembly of  claim 2  wherein the second volume of fluid is greater than the first volume of fluid. 
     
     
         4 . The downhole motor-pump assembly of  claim 1  wherein the rotor is configured such that the first rotor section defines a first orbital path upon rotation of the rotor and the second rotor section defines a second orbital path upon rotation of the rotor, the first orbital path and second orbital path being substantially similar to each other, allowing the rotor sections to be common and rigid. 
     
     
         5 . The downhole motor-pump assembly of  claim 1  wherein the rotor freely rotates within the stator. 
     
     
         6 . The downhole motor-pump assembly of  claim 1  wherein the first stator section has a first internal profile that is substantially similar to the first geometrical shape and the second stator section has a second internal profile that is substantially similar to the second geometrical shape. 
     
     
         7 . The downhole motor-pump assembly of  claim 1  wherein the rotor is a single, one-piece member. 
     
     
         8 . The downhole motor-pump assembly of  claim 1  wherein the rotor is configured to be rotated by fluid flowing through the tubular string. 
     
     
         9 . A tubular string comprising:
 a downhole motor-pump assembly, the downhole motor-pump assembly including:
 a stator, the stator having a first stator section and a second stator section, the first stator section being spaced from the second stator section by a gapped region; and 
 a rotor, wherein the rotor is configured to rotate freely within the stator; and 
   a string body, wherein the downhole motor-pump assembly is disposed within the string body and configured such that the rotor rotates within the stator when fluid is urged downstream within the tubular string.   
     
     
         10 . The tubular string of  claim 9  wherein the rotor has a first rotor portion and a second rotor portion, the first rotor portion having a first geometrical shape and the second rotor portion having a second geometrical shape, the first geometrical shape differing from the second geometrical shape. 
     
     
         11 . The tubular string of  claim 10  wherein the rotor is a single, one-piece member. 
     
     
         12 . The tubular string of  claim 10  wherein the string body includes a pump opening fluidly connected to the gapped region, the pump opening located downstream of the downhole motor-pump assembly. 
     
     
         13 . The tubular string of  claim 12  wherein the pump opening is configured to enable wellbore fluid and debris to be pumped therethrough. 
     
     
         14 . The tubular string of  claim 13  wherein the tubular string includes a filter positioned between the gapped region and the pump opening. 
     
     
         15 . The tubular string of  claim 14  wherein the filter is configured to enable wellbore fluid to pass therethrough while preventing passage of debris particles. 
     
     
         16 . The tubular string of  claim 12  wherein the downhole motor-pump assembly comprises an inlet opening and an outlet opening, 
     
     
         17 . The tubular string of  claim 16  wherein the gapped region is located between the inlet and outlet openings. 
     
     
         18 . A downhole motor-pump assembly comprising:
 a stator having a first stator section and a second stator section; and   a single rotor;   wherein the single rotor is positioned within the first and second stator sections, the downhole motor-pump assembly being devoid of any wobble shafts or couplings.   
     
     
         19 . The downhole motor-pump assembly of  claim 18  further comprising a thrust bearing. 
     
     
         20 . The downhole motor-pump assembly of  claim 19  wherein the thrust bearing is configured to transfer any unbalanced thrust load associated with rotation of the single rotor.