Roller cone bits, methods, and systems with anti-tracking variation in tooth orientation

Abstract

A roller cone drill bit in which the orientations of the teeth are varied within a single row, and/or between the heel row of one cone and the heel row of another cone, to prevent tracking.

What is claimed is:  
     
         1 . A roller cone bit comprising: 
 a plurality of non-axially-symmetric teeth mounted on rotatable elements, wherein ones of said teeth which follow the same path on a cutting face have different axial orientations;    whereby the likelihood of tracking is reduced.    
     
     
         2 . The bit of  claim 1 , wherein a first plurality of said teeth are contiguous and all have said first orientation, and a second plurality of said teeth are contiguous and all have said second orientation.  
     
     
         3 . A bit for downhole rotary drilling, comprising: 
 a rotatable element which includes a row of teeth;    wherein a first one of said teeth has a first orientation and a second one of said teeth has a second orientation which differs from said first orientation.    
     
     
         4 . The bit of  claim 3 , wherein a first plurality of said teeth are contiguous and all have said first orientation, and a second plurality of said teeth are contiguous and all have said second orientation.  
     
     
         5 . A bit for downhole rotary drilling, comprising: 
 a body having an attachment portion capable of being attached to a drill string;    cutting elements rotatably attached to said body, each said element including multiple rows of teeth;    wherein at least one of said rows on at least one said cutting element includes first and second teeth which are non-axisymmetric;    wherein said first tooth has a first orientation and said second tooth has a second orientation which differs from said first orientation.    
     
     
         6 . The bit of  claim 5 , wherein said bit is a tricone bit.  
     
     
         7 . The bit of  claim 5 , wherein a first plurality of said teeth are contiguous and all have said first orientation, and a second plurality of said teeth are contiguous and all have said second orientation.  
     
     
         8 . A drill bit, comprising: 
 a plurality of rotatable elements mounted to roll along a cutting face when said drill bit is rotated under load, each said rotatable element having a heel row and inner rows of teeth thereon;    wherein ones of said teeth in the heel row of a first one of said plurality of rotatable elements have crest orientations which are different from ones of said teeth in the heel row of a second one of said plurality of rotatable elements.    
     
     
         9 . A roller cone bit comprising: 
 a plurality of cones, each cone having a circumferential outermost row containing a plurality of teeth;    a first cone, having in its outermost row a first plurality of teeth having a first axial orientation; and,    a second cone, having in its outermost row, a second plurality of teeth having a second axial orientation which is not the same as said first axial orientation.    
     
     
         10 . The roller cone bit of  claim 9 , further comprising a third cone, having in its outermost row, a third plurality of teeth having a third axial orientation which is not the same as said first or said second axial orientation.  
     
     
         11 . A rotary drilling system, comprising: 
 a drill string which is connected to a bit; and    a rotary drive which rotates at least part of said drill string together with said bit;    wherein said bit comprises 
 a plurality of rotatable elements mounted to roll along a cutting face when said drill bit is rotated under load, each said rotatable element having teeth thereon;  
 wherein ones of said teeth which follow the same path on a cutting face have different axial orientations.  
   
     
     
         12 . The rotary drilling system of  claim 11 , wherein a first plurality of said teeth are contiguous and have a first orientation, and a second plurality of said teeth are contiguous have a second orientation which is different from said first orientation.  
     
     
         13 . A rotary drilling system, comprising: 
 a drill string which is connected to a bit; and    a rotary drive which rotates at least part of said drill string together with said bit;    wherein said bit comprises 
 a plurality of rotatable elements mounted to roll along a cutting face when said drill bit is rotated under load, each said rotatable element having an outer row and inner rows of teeth thereon;  
 wherein a first plurality of said teeth have crest orientations which are different from the crest orientations of a second plurality of teeth in said bit  
   
     
     
         14 . The rotary drilling system of  claim 13 , wherein said first plurality and said second plurality of teeth are on the same row of the same cone on said bit.  
     
     
         15 . The rotary drilling system of  claim 13 , wherein said first plurality of teeth are on the heel row of a first one of said rotatable elements and said second plurality of teeth are on the heel row of a second one of said rotatable elements which is different from said first one.  
     
     
         16 . A method of designing a bit for rotary drilling, comprising the actions of: 
 determining an optimal range of orientations for teeth for each row of each cone;    providing a variation in the orientations of ones of said teeth which follow the same path on a cutting face;    whereby tracking is reduced.    
     
     
         17 . The method of  claim 16 , wherein a plurality of said teeth have an orientation at a first end of said optimal range of orientations and a second plurality of said teeth have an orientation at an opposite end of said optimal range.  
     
     
         18 . A method for rotary drilling, comprising the actions of: 
 (a.) installing, on the drill string, a rotary drill bit whose tooth orientation has been optimized to provide a variation in the orientations of ones of said teeth which follow the same path on a cutting face;    (b.) rotating at least a portion of said drill string which includes said drill bit;    whereby tracking is reduced.    
     
     
         19 . The method of  claim 18 , further comprising pumping mud down said drill string to exit said rotary drill bit.