Casing rotary steerable system for drilling

Abstract

A system for drilling a deviated borehole, comprises a drill string, a bending mechanism supported on the drill string, a drill bit supported on the bending mechanism such that the axis of the bit does not align with the axis of the drill string where it connects to the bending mechanism, and a liner supported on at least one of the bit and the drill string and having upper and lower ends, wherein the bending mechanism is disposed within the liner such that the upper and lower liner ends are not co-axial.

1 . A system for drilling a deviated borehole, comprising:
 a drill string;   a bending mechanism supported on the drill string;   a drill bit supported on the bending mechanism such that the axis of the bit does not align with the axis of the drill string where it connects to the bending mechanism; and   a liner supported on at least one of the bit and the drill string and having upper and lower ends,   wherein said bending mechanism is disposed within said liner such that said upper and lower liner ends are not co-axial.   
     
     
         2 . The system according to  claim 1  wherein the bending mechanism contacts the inside of said liner at at least three axially spaced-apart locations. 
     
     
         3 . The system according to  claim 1  wherein the bending mechanism includes a counter-rotating device that maintains the orientation of the bending substantially fixed relative to the borehole. 
     
     
         4 . The system according to  claim 1  wherein the bending mechanism includes a mandrel that is stiffer than the liner. 
     
     
         5 . The system according to  claim 4  wherein the mandrel is constructed of a material that comprises beryllium. 
     
     
         6 . The system according to  claim 1  wherein the lower end of the liner is attached to the bit and the liner rotates with the bit. 
     
     
         7 . The system according to  claim 1  wherein the upper end of the liner is attached to the drill string. 
     
     
         8 . The system according to  claim 1 , further including a stabilizer disposed between the liner and the borehole.