Method and apparatus for directional drilling

Abstract

A method of and system for directional drilling reduces the friction between the drill string and the well bore. A downhole drilling motor is connected to the surface by a drill string. The drilling motor is oriented at a selected tool face angle. The drill string is rotated at said surface location in a first direction until a first torque magnitude without changing the tool face angle. The drill string is then rotated in the opposite direction until a second torque magnitude is reached, again without changing the tool face angle. The drill string is rocked back and forth between the first and second torque magnitudes.

What is claimed is: 
     
       1. A method of drilling a well, which comprises:
 (a) orienting a downhole drilling motor at a selected face angle, said drilling motor being connected by a drill string to a surface drilling location;   (b) rotating said drill string at said surface location in a first direction until a first measured torque magnitude is reached at said surface location; and then,   (c) rotating said drill string in the direction opposite said first direction until a second measured torque magnitude is reached at said surface location.   
     
     
       2. The method as claimed in  claim 1 , including repeating steps (b) and (c) while drilling with said drilling motor. 
     
     
       3. The method as claimed in  claim 1 , wherein said second torque magnitude is substantially equal to said first torque magnitude. 
     
     
       4. The method as claimed in  claim 1 , wherein said second torque magnitude is less than said first torque magnitude. 
     
     
       5. The method as claimed in  claim 1 , wherein:
 said drill string is rotated in said first direction to said first torque magnitude without changing said face angle; and,   said drill string is rotated in said direction opposite said first direction to said second torque magnitude without changing said face angle.   
     
     
       6. The method as claimed in  claim 5 , wherein said second torque magnitude is substantially equal to said first torque magnitude. 
     
     
       7. The method as claimed in  claim 5 , wherein said second torque magnitude is less than said first torque magnitude. 
     
     
       8. The method as defined in  claim 1  wherein said first torque magnitude is selected so that the drill string is rotated to a selected position therealong. 
     
     
       9. The method as defined in  claim 8  wherein the selected position along the drill string is a position at which reactive torque from said drilling motor substantially is stopped by friction between the drill string and a wall of a wellbore. 
     
     
       10. A method of drilling a well, which comprises:
 (a) determining the face angle of a downhole drilling motor, said downhole drilling motor being connected to a surface location by a drill string;   (b) rotating said drill string at said surface location in a first direction until a first measured torque magnitude is reached at said surface location without changing said face angle; and then   (c) rotating said drill string in the direction opposite said first direction until a second measure torque magnitude is reached at said surface location without changing said face angle.   
     
     
       11. The method as claimed in  claim 10 , including repeating steps (a) and (b) while drilling with said drilling motor. 
     
     
       12. The method as claimed in  claim 10 , wherein said second torque magnitude is substantially equal to said first torque magnitude. 
     
     
       13. The method as claimed in  claim 10 , wherein said second torque magnitude is less than said first torque magnitude. 
     
     
       14. A directional drilling system, which comprises:
 a torque sensor for determining torque applied to a drill string by rotating means;   a controller for operating said rotating means to rotate said drill string in a first direction until a first torque magnitude is determined and then in a direction opposite said first direction until a second torque magnitude is determined.   
     
     
       15. The system as claimed in  claim 14 , wherein said second torque magnitude is substantially equal to said first torque magnitude. 
     
     
       16. The system as claimed in  claim 14 , wherein said controller operates said rotating means to rotate said drill string until said first and second torque magnitudes are reached without changing bit face angle. 
     
     
       17. The system as claimed in  claim 14  further comprising means for calculating a value of said first torque magnitude such that said drill string is rotated to a position along said drill string at which reactive torque from a drilling motor is stopped by friction between the drill string and a wall of a wellbore. 
     
     
       18. The system as claimed in  claim 14 , wherein said second torque magnitude is less than said first torque magnitude. 
     
     
       19. The system as claimed in  claim 14 , wherein said rotating means comprises a top drive. 
     
     
       20. The system as claimed in  claim 14 , wherein said rotating means comprises a rotary table. 
     
     
       21. A method of drilling a well, comprising:
 (a) orienting a downhole drilling motor at a selected face angle, said drilling motor being connected by a drill string to a surface location;   (b) automatically rotating said drill string at said surface location in a first direction until a first measured torque magnitude is reached at the surface location; and then   (c) automatically changing rotation of said drill string to the direction opposite said first direction until a second measured torque magnitude is reached at the surface location; and then   (d) automatically changing rotation of said drill string to the first direction until the first measured torque magnitude is reached.   
     
     
       22. The method as claimed in claim 21, further comprising repeating (b), (c) and (d) while drilling the well with said drilling motor. 
     
     
       23. The method as claimed in claim 21, wherein said first measured torque magnitude corresponds to a change in the face angle. 
     
     
       24. The method as claimed in claim 21, wherein said second measured torque magnitude is less than said first measured torque magnitude. 
     
     
       25. The method as claimed in claim 21 further comprising:
 (e) measuring said second torque magnitude at said surface location; and,   (f) automatically changing rotation of said drill string to the first direction when said second torque magnitude is substantially equal to said first torque magnitude.