Low Friction Centralizer

Abstract

A centralizer for a downhole system, such as but not limited to a casing system. In some embodiments, the centralizer has a tubular body and a plurality of roller ball assemblies circumferentially spaced about the tubular body. Each roller ball assembly includes a plurality of rotatable balls adapted to engage a surface radially offset from the centralizer and rotate relative to the surface in any direction.

1 . A centralizer for a downhole system comprising:
 a tubular body; and   a plurality of roller ball assemblies circumferentially spaced about the tubular body, each roller ball assembly comprising:
 a plurality of rotatable balls adapted to engage a surface radially offset from the centralizer and rotate relative to the surface in any direction. 
   
     
     
         2 . The centralizer of  claim 1 , wherein the tubular body further comprises a plurality of circumferentially spaced raised vanes, each vane having a recess therein, the recess bounded by two radially extending surfaces and an axially extending surface therebetween. 
     
     
         3 . The centralizer of  claim 2 , wherein each vane comprises a plurality of ball receptacles in the axially extending surface, wherein one of the plurality of balls is rotatably seated in each ball receptacle. 
     
     
         4 . The centralizer of  claim 3 , further comprising a retainer plate coupled over each recess, the retainer plate having a plurality of ball receptacles, each ball receptacle aligned with a ball receptacle in the vane, and wherein one of the plurality of balls is rotatably disposed in each pair of aligned ball receptacles and extends through an opening in an outer surface of the retainer plate. 
     
     
         5 . The centralizer of  claim 4 , wherein the outer openings have a diameter less than that of the ball received therethrough. 
     
     
         6 . The centralizer of  claim 1 , wherein each roller ball assemblies comprises:
 a block having a plurality of ball receptacles; and   a retainer plate coupled to the block, the retainer plate having a plurality of ball receptacles, each ball receptacle aligned with one of the plurality of ball receptacles of the block;   wherein one of the plurality of balls is rotatably disposed in each pair of aligned ball receptacles.   
     
     
         7 . The centralizer of  claim 6 , wherein each roller ball assembly comprises an axially extending inner surface and an axially extending outer surface and wherein each ball extends through an opening in the outer surface. 
     
     
         8 . The centralizer of  claim 7 , wherein each ball extends through an opening in the inner surface. 
     
     
         9 . The centralizer of  claim 8 , wherein the openings have a diameter less than that of the ball extending therethrough. 
     
     
         10 . A system comprising:
 a tubular positioned in a wellbore; and   a centralizer supported by the tubular, the centralizer comprising:
 a roller ball assembly having a plurality of rotatable balls engaging a surface radially offset from the centralizer and rotatable over the surface in any direction. 
   
     
     
         11 . The system of  claim 10 , wherein the radially offset surface is a surface bounding a formation surrounding the wellbore and wherein rotation of the balls enables movement of the centralizer relative to the formation. 
     
     
         12 . The system of  claim 10 , wherein the radially offset surface is a surface of another tubular disposed concentrically about the centralizer and wherein rotation of the balls enables movement of the centralizer relative to the another tubular. 
     
     
         13 . The system of  claim 10 , wherein the radially offset surface is a surface of the tubular disposed within the centralizer and wherein rotation of the balls enables movement of the centralizer relative to the tubular. 
     
     
         14 . The system of  claim 10 , wherein the centralizer is threaded to the tubular. 
     
     
         15 . The system of  claim 10 , wherein the centralizer is disposed about the tubular. 
     
     
         16 . The centralizer of  claim 15 , wherein the centralizer is coupled to the tubular, whereby the centralizer is immovable relative to the tubular. 
     
     
         17 . A system comprising:
 two concentric tubulars positioned in a wellbore, the two concentric tubulars comprising an inner tubular and an outer tubular; and   a centralizer disposed therebetween, the centralizer comprising a plurality of balls engaging the tubulars and rotatable in any direction;   wherein rotation of the balls enables relative movement of the tubulars.   
     
     
         18 . The centralizer of  claim 17 , wherein the centralizer further comprises a tubular body having a plurality of circumferentially spaced cutouts. 
     
     
         19 . The centralizer of  claim 18 , wherein, within each cutout, the centralizer further comprises:
 a block coupled to the tubular body, the block having a plurality of ball receptacles; and   a retainer plate coupled to the block, the retainer plate having a plurality of ball receptacles, each ball receptacle aligned with one of the plurality of ball receptacles of the block;   wherein one of the plurality of balls is rotatably disposed in each pair of aligned ball receptacles.   
     
     
         20 . The centralizer of  claim 19 , wherein each block, the retainer plate coupled thereto, and the balls disposed therebetween forms a roller ball assembly, the roller ball assembly having an inner surface and an outer surface, and wherein each ball disposed in the roller ball assembly extends through an opening in the outer surface to rotatably engage the outer tubular, whereby the centralizer moves relative to the outer tubular. 
     
     
         21 . The centralizer of  claim 20 , wherein each ball disposed in the roller ball assembly extends through an opening in the inner surface to rotatably engage the inner tubular, whereby the centralizer moves relative to the inner tubular.