Centralizer

Abstract

A centraliser ( 1 ) has a substantially annular body ( 6 ), a substantially cylindrical bore extending longitudinally through the body ( 6 ), and at least one roller ball ( 29 ). The roller ball ( 29 ) is preferably secured to the centraliser ( 1 ) in a manner which enables the roller ball ( 29 ) to rotate in all directions with respect to the centraliser ( 1 ), and one roller ball ( 29 ) is secured within at least one aperture ( 9; 109 ) provided in the sidewall of the body ( 6 ). Preferably, an assembly ( 27, 28, 39; 127, 128, 139 ) is provided to house the rollerball ( 29 ) within the at least one aperture ( 9; 109 ), and the roller ball ( 29 ) may be arranged to project either outwardly or inwardly from the sidewall.

1 . A centraliser comprising a substantially annular body, a substantially cylindrical bore extending longitudinally through the body, the annular body comprising at least one roller ball.  
     
     
         2 . A centraliser according to  claim 1 , wherein the roller ball is secured to the centraliser in a manner which enables the roller ball to rotate in all directions with respect to the centraliser.  
     
     
         3 . A centraliser according to either of claims  1  or  2 , wherein the centraliser is provided with at least one aperture, and the roller ball is secured within the aperture.  
     
     
         4 . A centraliser according to  claim 3 , wherein the at least one aperture is formed in a sidewall of the centraliser.  
     
     
         5 . A centraliser according to  claim 4 , wherein the at least one aperture is formed in a blade of the centraliser.  
     
     
         6 . A centraliser according to any of  claims 3  to  5 , wherein the at least one aperture is arranged wholly through the sidewall.  
     
     
         7 . A centraliser according to any of claims  3  to  6 , wherein at least one of the apertures is arranged such that the roller ball is arranged to project outwardly from the sidewall.  
     
     
         8 . A centraliser according to any of  claims 3  to  7 , wherein at least one of the apertures is arranged such that the roller ball is arranged to project inwardly from the sidewall.  
     
     
         9 . A centraliser according to any of  claims 3  to  8 , wherein an assembly is provided to house the roller ball within the at least one aperture.  
     
     
         10 . A centraliser according to any of  claims 3  to  9 , wherein the at least one aperture is provided with a shoulder which is adapted, in use, to bear against a portion of the assembly.  
     
     
         11 . A centraliser according to any of  claims 3  to  10 , wherein a plurality of apertures are provided, such apertures being spaced apart in the longitudinal direction of the body.  
     
     
         12 . A method of running a string of tubulars into a well bore, the method comprising providing a centraliser comprising a substantially annular body, and a substantially cylindrical bore extending longitudinally through the body, and the annular body comprising at least one roller ball.  
     
     
         13 . A roller ball assembly for use with a centraliser having an engagement mechanism, the roller ball assembly comprising a roller ball and a housing for the roller ball, the housing comprising an engagement mechanism capable of engagement with the engagement mechanism of the centraliser.  
     
     
         14 . A roller ball assembly according to  claim 13 , wherein the housing comprises an inner surface which substantially corresponds to the shape of the roller ball, and an aperture to permit a portion of the roller ball to project outwardly therefrom.  
     
     
         15 . A roller ball assembly according to  claim 14 , wherein the housing further comprises a seal to prevent ingress of debris from outside of the housing into the interior of the housing, in use.  
     
     
         16 . A roller ball assembly according to any of claims  claim 13  to  15 , wherein the housing is provided in at least two parts to permit the insertion of the roller ball into the housing.  
     
     
         17 . A roller ball assembly according to any of  claims 13  to  16 , wherein the engagement mechanisms comprise screw threads.  
     
     
         18 . A roller ball assembly according to  claim 17 , wherein the screw threads of the roller ball assembly are provided on an outer surface of the housing.