Downhole expandable drive reamer apparatus

Abstract

A downhole expandable drive reamer apparatus is described. The apparatus comprises a body defining a longitudinal axis X-X. At least one roller is disposed on the body and is moveable relative to the body between an inwardly retracted condition and an outwardly deployed condition. A thread or other protrusion is formed on at least one roller and is arranged to engage a surface of a well bore to drive the apparatus to along the well bore when the roller is in the outwardly deployed condition. The rotational axis R-R of the roller is non-parallel to the longitudinal axis X-X of the body.

1 . A downhole expandable drive reamer apparatus for incorporation into a drill string, the apparatus comprising:
 a body defining a longitudinal axis;   at least one roller moveable relative to the body between an inwardly retracted condition and an outwardly deployed condition;   surface engagement means disposed on an outer surface of said at least one roller, the surface engagement means comprising at least one protrusion extending from an outer surface of said at least one roller to engage a surface of a well bore to drive the apparatus along the well bore;   characterised in that the rotational axis of said at least one roller is non-parallel to the longitudinal axis of the body.   
     
     
         2 . An apparatus according to  claim 1 , wherein the angle formed between the rotational axis of said at least one roller and the longitudinal axis of the body is more than zero degrees and no more than five degrees. 
     
     
         3 . An apparatus according to  claim 1 , wherein said at least one roller is rotatably mounted between two pistons, each said piston being arranged to be moved between an inwardly retracted position in the body and an outwardly deployed condition relative to the body in response to pressurisation of fluid in the body. 
     
     
         4 . An apparatus according to  claim 1 , wherein said at least one roller is rotatably mounted between two mounting members, each said mounting member being disposed on respective biasing means to enable each said mounting member to move between an inwardly retracted position in the body and an outwardly deployed condition relative to the body. 
     
     
         5 . An apparatus according to  claim 4 , wherein said biasing means comprises at least one disk spring mounted between the respective mounting member and the body. 
     
     
         6 . An apparatus according to  claim 1 , further comprising a plurality of rollers disposed at different locations around the body. 
     
     
         7 . An apparatus according to  claim 1 , wherein the surface engagement means comprises a thread disposed on an outer surface of said at least one roller. 
     
     
         8 . An apparatus according to  claim 1 , wherein the surface engagement means comprises a plurality of protrusions disposed on an outer surface of said at least one roller. 
     
     
         9 . (canceled) 
     
     
         10 . A drill string comprising a downhole expandable drive reamer apparatus according to  claim 1 . 
     
     
         11 . An apparatus according to  claim 2 , wherein said at least one roller is rotatably mounted between two pistons, each said piston being arranged to be moved between an inwardly retracted position in the body and an outwardly deployed condition relative to the body in response to pressurisation of fluid in the body. 
     
     
         12 . An apparatus according to  claim 2 , wherein said at least one roller is rotatably mounted between two mounting members, each said mounting member being disposed on respective biasing means to enable each said mounting member to move between an inwardly retracted position in the body and an outwardly deployed condition relative to the body. 
     
     
         13 . An apparatus according to  claim 12 , wherein said biasing means comprises at least one disk spring mounted between the respective mounting member and the body. 
     
     
         14 . An apparatus according to  claim 2 , further comprising a plurality of rollers disposed at different locations around the body. 
     
     
         15 . An apparatus according to  claim 2 , wherein the surface engagement means comprises a thread disposed on an outer surface of said at least one roller. 
     
     
         16 . An apparatus according to  claim 2 , wherein the surface engagement means comprises a plurality of protrusions disposed on an outer surface of said at least one roller. 
     
     
         17 . A drill string comprising a downhole expandable drive reamer apparatus according to  claim 2 .