Steerable drilling tool

Abstract

A downhole steering tool will steer the angle of the drill bit for drilling directional wells. The steering tool includes a steering housing which is mounted on the drill string above the drill bit. The steering housing can be held against rotation while the drill string rotates to cause the bit to drill in a desired direction. Guide members are mounted on the steering housing. The guide members may engage the borehole. The guide members can be turned about an axis which is perpendicular to the longitudinal axis of the steering housing. Turning the guide members causes the steering housing to rotate relative to the borehole in one direction or the other as the housing slides downward in the borehole. Reorienting the steering housing allows steering of the drill bit.

What is claimed is:  
     
         1 . A steering apparatus for use in directional drilling a borehole with a drill string and a drill bit, comprising: 
 a steering housing mounted on the drill string above the drill bit;    a clutch connected between the drill string and the steering housing; and    at least one angulatable guide member mounted to the steering housing, and having a protuberance from the steering housing.    
     
     
         2 . The apparatus according to    claim 1   , wherein said protuberance comprises a blade for engaging a sidewall of the borehole.  
     
     
         3 . The apparatus according to    claim 1   , wherein said at least one angulatable guide member includes a rotary member defining a steering axis which is approximately perpendicular to a longitudinal axis of the steering housing.  
     
     
         4 . The apparatus according to    claim 3   , wherein said protuberance comprises a blade for engaging a sidewall of the borehole.  
     
     
         5 . The apparatus according to    claim 1   , further comprising a motor mounted in the steering housing and coupled to said at least one angulatable guide member.  
     
     
         6 . The apparatus according to    claim 1   , wherein said at least one angulatable guide member comprises an extensible and retractable, angulatable guide member.  
     
     
         7 . The apparatus according to    claim 1   , further comprising at least one stabilizer blade connected to the steering housing having an outer diameter which is greater than an outer diameter of the steering housing and less than an outer diameter of said protuberance.  
     
     
         8 . The apparatus according to    claim 1   , further comprising: 
 an annular cam member mounted in the steering housing, said annular cam member having a cam slot; and    a pin extending eccentrically from said at least one angulatable guide member into engagement with the cam slot.    
     
     
         9 . The apparatus according to    claim 1   , wherein said at least one angulatable guide member comprises a plurality of angulatable guide members evenly spaced around a circumference of the steering housing.  
     
     
         10 . The apparatus according to    claim 1   , wherein the steering housing has an upper portion and a lower portion, and the lower portion has a longitudinal axis which is at angle relative to a longitudinal axis of the upper portion.  
     
     
         11 . A steering apparatus for use in directional drilling a borehole with a drill string and a drill bit, comprising: 
 a steering housing mounted on the drill string above the drill bit;    a means for allowing rotation of the drill string relative to the steering housing connected between the drill string and the steering housing; and    a means for engaging a sidewall of the borehole mounted in the steering housing including a means for independently turning said means for engaging the sidewall of the borehole.    
     
     
         12 . The apparatus according to    claim 11   , wherein said means for engaging a sidewall of the borehole comprises a plurality of blades.  
     
     
         13 . The apparatus according to    claim 11   , wherein said means for independently turning comprises an angulatable guide member.  
     
     
         14 . The apparatus according to    claim 13   , wherein said means for engaging a sidewall of the borehole comprises a plurality of blades.  
     
     
         15 . The apparatus according to    claim 11   , wherein said means for independently turning comprises a plurality of motors mounted in the steering housing and operationally coupled to said means for engaging a sidewall of the borehole.  
     
     
         16 . The apparatus according to    claim 11   , wherein said means for engaging the sidewall of the borehole comprises a plurality of extensible and retractable blades.  
     
     
         17 . The apparatus according to    claim 11   , wherein said means for allowing rotation of the drill string relative to the steering housing comprises a clutch.  
     
     
         18 . The apparatus according to    claim 11   , wherein the actuator compnses: 
 an annular cam member mounted in the steering housing, said annular cam member having a cam slot; and    a pin extending eccentrically from said means for independently turning into engagement with the cam slot.    
     
     
         19 . The apparatus according to    claim 11   , wherein the steering housing has a lower portion and an upper portion, and the lower portion has a longitudinal axis which is inclined relative to a longitudinal axis of the upper portion.  
     
     
         20 . The apparatus according to    claim 19   , wherein said means for engaging a sidewall of the borehole is located on the upper portion of the steering housing.  
     
     
         21 . A method of steering a drill bit for directional drilling a well wherein the drill bit forms a borehole with a sidewall, comprising: 
 (a) penetrating the sidewall of the borehole with a guide member;    (b) rotating the drill string and the drill bit independent from the guide member; and    (c) selectively angulating the guide member to change an orientation relative to the borehole.    
     
     
         22 . The method according to    claim 21   , further comprising: 
 retracting the guide member away from the sidewall of the borehole.    
     
     
         23 . The method according to    claim 22   , further comprising selectively rotating the drill string and the drill bit together with the guide member.  
     
     
         24 . The method according to    claim 21   , wherein said step of angulating the guide member in one direction causes the drill bit to rotate relative to the borehole in a counterclockwise direction, and angulating the guide member sufficiently in an opposite direction causes the drill bit to rotate relative to the borehole in a clockwise direction.