Method of and system for controlling directional drilling

Abstract

A method of and system for controlling directional drilling determines a relationship between surface drill string orientation angle and drill bit face angle. The method uses the relationship to determine a predicted drill bit face angle. The method then uses the predicted drill bit face angle to achieve a target drill bit face angle by calculating a surface drill string correction angle. The correction angle may be displayed to a human driller. Alternatively, the correction angle may be provided as an input to an automated drilling machine.

What is claimed is:  
     
         1 . A method of controlling directional drilling, which comprises: 
 determining a relationship between a first drilling control variable and drill bit face angle;    determining, based upon said relationship, a target first control variable value to achieve a target face angle; and,    correcting current first drilling control variable to said target first drilling control variable to achieve said target face angle.    
     
     
         2 . The method as claimed in  claim 1 , wherein determining said relationship between said first drilling control variable and said drill bit face angle comprises: 
 collecting drill bit face angle and first drilling control variable data.    
     
     
         3 . The method as claimed in  claim 2 , wherein determining said relationship between said first drilling control variable and said drill bit face angle comprises: 
 performing linear regression of said drill bit face angle and said first drilling control variable data, to obtain a mathematical model with drill bit face angle as a response variable and first drilling control variable as an explanatory variable.    
     
     
         4 . The method as claimed in  claim 3 , wherein determining a target first control variable value to achieve a target face angle includes: 
 solving said mathematical model for a measured first drilling control variable value.    
     
     
         5 . The method as claimed in  claim 1 , wherein correcting a current first drilling control variable to said target first drilling control variable to achieve a target face angle. 
 calculating a surface drill string correction angle to achieve said target face angle.    
     
     
         6 . The method as claimed in  claim 5 , including displaying said correction angle.  
     
     
         7 . The method as claimed in  claim 5 , including inputting said correction angle to an automatic drilling machine.  
     
     
         8 . The method as claimed in  claim 1 , wherein said control variable is surface drill string orientation.  
     
     
         9 . The method as claimed in  claim 1 , including: 
 determining a relationship between rate of penetration and a second drilling control variable;    determining a target second drilling control variable value, based upon said relationship between rate of penetration and said second drilling control variable, to achieve an optimum rate of penetration; and,    maintaining said second drilling control variable at said target second drilling control variable value.    
     
     
         10 . The method as claimed in  claim 9 , wherein determining said relationship between rate of penetration and said second drilling control variable includes: 
 collecting rate of penetration data.    
     
     
         11 . The method as claimed in  claim 10 , wherein determining a relationship between rate of penetration and said second drilling control variable includes: 
 performing linear regression of said rate of penetration data and said second drilling control variable data, to obtain a mathematical model with rate of penetration as response variable and second drilling control variable as an explanatory variable.    
     
     
         12 . The method as claimed in  claim 9 , wherein maintaining said second drilling control variable at said target second drilling control variable value includes: 
 displaying said target second drilling control variable value.    
     
     
         13 . The method as claimed in  claim 9 , wherein maintaining said second drilling control variable at said target second drilling control variable value includes: 
 inputting said target drilling control variable value to an automatic drilling machine.    
     
     
         14 . The method as claimed in  claim 9 , wherein said second drilling control variable is pressure differential.  
     
     
         15 . A directional drilling control system, which comprises: 
 means for determining a relationship between a first drilling control variable and a drill bit face angle;    means for predicting, based upon said relationship, a target first drilling control variable to achieve a target drill bit face angle; and,    means for determining a correction to said target first drilling control variable to achieve a target face angle.    
     
     
         16 . The system as claimed in  claim 15 , wherein said means for determining said relationship between said drilling control variable and said drill bit face angle comprises: 
 means for collecting drill bit face angle and first drilling control variable data.    
     
     
         17 . The system as claimed in  claim 16 , wherein said means for determining said relationship between said first drilling control variable and said drill bit face angle comprises: 
 means for performing linear regression of said drill bit face angle and said first drilling control variable data, to obtain a mathematical model with drill bit face angle as response variable and first drilling control variable as an explanatory variable.    
     
     
         18 . The system as claimed in  claim 17 , wherein said means for predicting said predicted drill bit face angle includes: 
 means for solving said mathematical model for said first drilling control variable value.    
     
     
         19 . The system as claimed in  claim 15 , wherein said means for determining a correction to said target first drilling control variable to achieve a target face angle includes: 
 means for calculating a surface drill string correction angle to achieve said target face angle.    
     
     
         20 . The system as claimed in  claim 19 , including a display for displaying said correction angle.  
     
     
         21 . The system as claimed in  claim 15 , including: 
 means for determining a relationship between rate of penetration and a second drilling control variable;    means for determining a target control variable value, based upon said relationship between rate of penetration and said second drilling control variable, to achieve an optimum rate of penetration.    
     
     
         22 . The system as claimed in  claim 21 , wherein said means for determining said relationship between rate of penetration and said second drilling control variable includes: 
 means for collecting rate of penetration data.    
     
     
         23 . The system as claimed in  claim 22 , wherein said means for determining a relationship between rate of penetration and said second drilling control variable includes: 
 means for performing linear regression of said rate of penetration data and said second drilling control variable data, to obtain a mathematical model with rate of penetration as response variable and second drilling control variable as an explanatory variable.    
     
     
         24 . The system as claimed in  claim 21 , including 
 a display for displaying said target second drilling control variable value.    
     
     
         25 . The system as claimed in  claim 21 , including: 
 an automatic drilling machine arranged to receive said target control variable value.    
     
     
         26 . A method of drilling, which comprises: 
 determining a relationship between surface drill string angular orientation and drill bit face angle;    determining, based upon said relationship, a target surface drill string angular orientation to achieve a target face angle;    correcting current surface drill string angular orientation to said target surface drill string angular orientation to achieve said target face angle;    determining a relationship between rate of penetration and a drilling control variable;    determining a target drilling control variable value, based upon said relationship between rate of penetration and said drilling control variable, to achieve an optimum rate of penetration; and,    maintaining said drilling control variable at said target second drilling control variable value.