Deviated drilling system utilizing steerable bias unit

Abstract

A technique facilitates steering during, for example, a borehole drilling operation. The technique employs a drill string comprising a drill bit and a steering tool for controlling the trajectory of a borehole formed by rotating the drill bit. The steering tool includes a main body and a steering sleeve pivotably mounted to the main body by a joint located to enable pushing contact via the steering sleeve against a surrounding borehole wall at a location between the joint and the drill bit. The steering sleeve is selectively pivoted by a plurality of actuators disposed between the main body and the steering sleeve.

What is claimed is: 
     
         1 . A system for use in a well, comprising:
 a drill string comprising a drill bit and a steering tool for controlling the trajectory of a borehole formed by rotating the drill bit, the steering tool comprising a main body and a steering sleeve pivotably mounted to the main body by a joint located to enable pushing contact via the steering sleeve against a surrounding borehole wall at a location between the joint and the drill bit, the steering sleeve being selectively pivoted by a plurality of actuators disposed between the main body and the steering sleeve.   
     
     
         2 . The system as recited in  claim 1 , wherein the plurality of actuators comprises a plurality of hydraulic actuators. 
     
     
         3 . The system as recited in  claim 1 , wherein the plurality of actuators comprises a plurality of hydraulic ball actuators. 
     
     
         4 . The system as recited in  claim 1 , wherein the steering sleeve comprises a plurality of steering blades. 
     
     
         5 . The system as recited in  claim 1 , wherein the joint comprises a gimbal joint which pivots via pairs of axis pins. 
     
     
         6 . The system as recited in  claim 1 , wherein the steering sleeve comprises a sacrificial liner. 
     
     
         7 . A method, comprising:
 pivotably coupling a steering sleeve, having a sacrificial liner, to a main body to form a steering tool;   using a sacrificial liner positioned along an interior of the steering sleeve;   locating a plurality of actuators between the main body and the steering sleeve;   coupling the steering tool to a drill bit;   rotating the drill bit; and   controlling the drilling orientation of the drill bit by selectively actuating selected actuators of the plurality of actuators to cause the steering sleeve to pivot against a surrounding borehole wall, thus pushing the drill bit.   
     
     
         8 . The method as recited in  claim 7 , wherein pivotably coupling comprises pivotably coupling the steering sleeve to the main body with a gimbal joint. 
     
     
         9 . The method as recited in  claim 8 , wherein controlling comprises pivoting the steering sleeve into contact with the surrounding borehole wall at an axial position between the gimbal joint and the drill bit. 
     
     
         10 . The method as recited in  claim 7 , wherein locating comprises locating a plurality of hydraulic actuators. 
     
     
         11 . The method as recited in  claim 7 , wherein locating comprises locating a plurality of hydraulic ball actuators. 
     
     
         12 . The method as recited in  claim 7 , further comprising constructing the steering sleeve with a plurality of external blades. 
     
     
         13 . The method as recited in  claim 7 , further comprising forming the steering sleeve with a plurality of blades positioned along the exterior of the steering sleeve. 
     
     
         14 . The method as recited in  claim 7 , further comprising forming the steering sleeve with a plurality of helical blades positioned along the exterior. 
     
     
         15 . A system, comprising:
 a steering tool operable to control a trajectory of a borehole during drilling of the borehole, the steering tool comprising:
 a main body; and 
 a steering sleeve pivotably mounted to the main body by a gimbal joint to enable pushing contact via the steering sleeve against a surrounding borehole wall, the steering sleeve being selectively pivoted by a plurality of actuators disposed between the main body and the steering sleeve. 
   
     
     
         16 . The system as recited in  claim 15 , wherein the steering tool further comprises a sacrificial liner positioned along an interior of the steering sleeve. 
     
     
         17 . The system as recited in  claim 15 , wherein the gimbal joint comprises a middle ring having a plurality of pivots, the middle ring being positioned between the main body and the steering sleeve. 
     
     
         18 . The system as recited in  claim 15 , wherein the plurality of actuators comprises a plurality of hydraulic actuators. 
     
     
         19 . The system as recited in  claim 15 , wherein the steering sleeve comprises a plurality of steering blades. 
     
     
         20 . The system as recited in  claim 15 , further comprising a drill bit coupled to the steering tool, wherein the steering sleeve is oriented to apply a steering force against a surrounding wall at an axial position between the gimbal joint and the drill bit.