Roller cone bits with reduced packing

Abstract

A roller-cone drill bit in which a large groove is machined into the backface of each cone, near the crack where the cone meets the arm assembly. By making the outer lip of this crack more exposed to the open volume of turbulent flow, turbulence near the crack is increased, deposit of sediments near the crack is reduced, and infiltration of sediments through the crack is also reduced. Drill bit lifetime has been shown to be greatly extended by this change.

1 - 30 . (canceled)  
   
   
       31 . A bit for downhole rotary drilling, comprising: 
 a body supporting at least one arm/spindle structure; and    a cutting element mounted on said arm/spindle structure through one or more rotary bearings;    wherein said cutting element and said arm/spindle structure jointly define a crack which is interposed between said bearings and the cuttings-laden fluid;    and wherein said cutting element incorporates a groove, in the back face thereof, which defines a channel having a shape factor of more than 0.5 (defined with reference to a round tube's shape factor of 1.0).    
   
   
       32 . The bit of  claim 31 , wherein said groove is defined both by a recess in said cone, and also by a recess in said arm.  
   
   
       33 . The bit of  claim 31 , wherein a finger extends into said groove for a length of more than 0.100 inches.  
   
   
       34 . A method for downhole rotary drilling, comprising the use of a bit according to  claim 31 .  
   
   
       35 . A rotary cutting component for a roller-cone drill bit, comprising: 
 cutters on a body; and    a seal gland, and a backface outboard of said gland; said backface terminating in a dihedral angle of at least 75 degrees.    
   
   
       36 . A method of designing a bit for rotary drilling, comprising the actions of: 
 adding additional space, where the dynamic crack between cone and arm enters open mud volume, to increase the peak flow velocity at the opening of crack.    
   
   
       37 . A drill rig, comprising a bit according to  claim 31.