Eccentric Stabilizer for Use in a Synchronous Rotary Steerable System

Abstract

A method and apparatus for steering a drilling assembly ( 200 ) during drilling operations for oil and gas. The steering assembly being disposed in a borehole ( 10 ) and comprising a drill bit ( 120 ) attached to a drill collar (210) having an eccentric stabilizer ( 220 ) disposed thereupon. The eccentric stabilizer either in an engaged state whereupon rotating concentrically with the drill collar, or in a released state whereupon as the drill collar rotates the eccentric stabilizer is positioned eccentrically relative to the drill collar creating a lateral deflection in the borehole that may be used for changing the direction of the drilling assembly.

What is claimed is: 
     
         1 . A downhole assembly coupling to a drilling string for drilling a borehole, the assembly comprising:
 a drill body rotating with the drillstring;   an engagement mechanism disposed on the drill body and operable between engaged and disengaged conditions;   a drill bit rotating with the drill body for drilling the borehole; and   a rotatable stabilizer eccentrically disposed on the drill body, the rotatable stabilizer rotating with the drill body when engaged by the engagement mechanism in the engaged condition, the rotatable stabilizer being rotatable eccentrically relative to the drill body when released by the engagement mechanism in the disengaged condition, the rotatable stabilizer eccentrically rotated relative to the drill body and creating a lateral force on the drill body to change drilling trajectory thereof.   
     
     
         2 . The assembly of  claim 1 , wherein the drill body comprises an eccentric section on which the at least one rotatable stabilizer is rotatably disposed, the eccentric section offset from a rotational axis of the drill body. 
     
     
         3 . The assembly of  claim 2 , wherein the rotatable stabilizer comprises a sleeve have an eccentric passage rotatably disposed on the eccentric section. 
     
     
         4 . The assembly of  claim 2 , wherein the at least one rotatable stabilizer when engaged by the engagement mechanism positions concentrically relative to the drill body. 
     
     
         5 . The assembly of  claim 2 , wherein the at least one rotatable stabilizer when disengaged by the engagement mechanism positions eccentrically relative to the drill body. 
     
     
         6 . The assembly of  claim 1 , wherein the engagement mechanism comprises one or more of a pin, a clutch, a spring, a piston, a valve, a ball-release mechanism, a lock, a slot, or a combination thereof. 
     
     
         7 . A downhole assembly coupling to a drilling string for drilling a borehole, the assembly comprising:
 a drill body rotating with the drillstring;   a drill bit rotating with the drill body for drilling the borehole;   an inner sleeve eccentrically disposed on the drill body and rotatable relative thereto;   an outer sleeve eccentrically disposed on the inner sleeve and rotatable relative thereto; and   an actuator disposed on the drill body and operable between first and second conditions, the actuator engaged with the inner sleeve and selectively engageable in the first and second conditions with the outer sleeve, the actuator in the first condition selectively engaged with the outer sleeve and orienting a combined eccentricity of the inner and outer sleeves concentrically on the drill collar, the actuator in the second condition selectively engaged with the outer sleeve and orienting the combined eccentricity of the inner and outer sleeves eccentrically on the drill collar.   
     
     
         8 . The assembly of  claim 7 , wherein the actuator comprises an axial member slideably engaged with the inner sleeve. 
     
     
         9 . The assembly of  claim 8 , wherein the actuator is linearly and rotationally movable relative to the drill body. 
     
     
         10 . The assembly of  claim 7 , wherein the actuator comprises a first stop disposed thereon, the first stop engageable with a first portion of the outer sleeve when the actuator is in the first condition. 
     
     
         11 . The assembly of  claim 10 , wherein the actuator in the first condition radially aligns the first stop with the first portion. 
     
     
         12 . The assembly of  claim 10 , wherein the actuator comprises a second stop disposed thereon, the second stop engageable with a second portion of the outer sleeve when the actuator is in the second condition. 
     
     
         13 . The assembly of  claim 12 , wherein the actuator in the second condition radially aligns the second stop with the second portion. 
     
     
         14 . The assembly of  claim 7 , wherein the actuator comprises a linear actuator component operable to move a portion of the actuator linearly relative to the drill body. 
     
     
         15 . The assembly of  claim 14 , wherein the actuator comprises a clutch component operable to couple at least a portion of the rotation of the drill body to a portion of the actuator. 
     
     
         16 . A method of drilling a borehole with a downhole assembly coupled to a drilling string, the method comprising:
 rotating a drill bit about a rotational axis of the downhole assembly;   directing the rotational axis in the borehole by combining a first eccentricity of a sleeve relative to a second eccentricity of an eccentric section of the downhole assembly on which the rotatable sleeve is disposed;   drilling a first trajectory by orienting the combined eccentricity of the sleeve and the eccentric section concentric to the rotational axis; and   drilling a second trajectory offset from the first trajectory by orienting the combined eccentricity of the sleeve and the eccentric section eccentric to the rotational axis.   
     
     
         17 . The method of  claim 16 , wherein drilling the first trajectory comprises orienting the eccentric section within an eccentric passage of the sleeve so that the sleeve is concentric to the rotational axis; and engaging the sleeve so oriented with the rotation of the drilling assembly. 
     
     
         18 . The method of  claim 17 , wherein drilling the second trajectory offset from the first trajectory comprises disengaging the sleeve from the rotation of the drilling assembly; and orienting the eccentric section within the eccentric passage of the sleeve so that the sleeve is eccentric to the rotational axis. 
     
     
         19 . A method of drilling a borehole with a downhole assembly coupled to a drilling string, the method comprising:
 rotating a drill bit about a rotational axis of the downhole assembly;   directing the rotational axis in the borehole by combining a first eccentricity of a first rotatable sleeve relative to the downhole assembly with a second eccentricity of a second rotatable sleeve relative to the first rotatable sleeve;   drilling a first trajectory by orienting the combined eccentricity of the first and second sleeves concentric to the rotational axis; and   drilling a second trajectory offset from the first trajectory by orienting the combined eccentricity of the first and second sleeves eccentric to the rotational axis.   
     
     
         20 . The method of  claim 19 , wherein drilling the first trajectory comprises orienting at least one of the first and second sleeves relative to the other of the first and second sleeves so that the combined eccentricity is concentric to the rotational axis. 
     
     
         21 . The method of  claim 19 , wherein drilling the second trajectory offset from the first trajectory comprises orienting at least one of the first and second sleeves relative to the other of the first and second sleeves so that the combined eccentricity is eccentric to the rotational axis.