Fixed Cutter Bit With Centrally Positioned Backup Cutter Elements

Abstract

A drill bit for drilling a borehole in earthen formations. In an embodiment, the bit comprises a bit body having a bit face comprising a cone region, a shoulder region, and a gage region. In addition, the bit comprises at least one primary blade disposed on the bit face, wherein the at least one primary blade extends into the cone region. Further, the bit comprises a plurality of primary cutter elements mounted on the at least one primary blade in the cone region. Still further, the bit comprises a plurality of backup cutter elements mounted on the at least one primary blade in the cone region, wherein the at least one primary blade has a cone backup cutter density and a shoulder backup cutter density, and wherein the cone backup cutter density of the at least one primary blade is greater than the shoulder backup cutter density of the at least one primary blade.

1 . A drill bit for drilling a borehole in earthen formations, the bit comprising: 
 a bit body having a bit face comprising a cone region, a shoulder region, and a gage region;    at least one primary blade disposed on the bit face, wherein the at least one primary blade extends into the cone region;    a plurality of primary cutter elements mounted on the at least one primary blade in the cone region;    a plurality of backup cutter elements mounted on the at least one primary blade in the cone region;    wherein the at least one primary blade has a cone backup cutter density and a shoulder backup cutter density; and    wherein the cone backup cutter density of the at least one primary blade is greater than the shoulder backup cutter density of the at least one primary blade.    
   
   
       2 . The drill bit of  claim 1 , wherein the at least one primary blade extends into the shoulder region, and wherein at least one primary cutter element is mounted on the at least one primary blade in the shoulder region.  
   
   
       3 . The drill bit of  claim 1 , wherein the at least one primary blade has a gage backup cutter density and wherein the cone backup cutter density of the at least one primary blade is greater than the gage backup cutter density of the at least one primary blade.  
   
   
       4 . The drill bit of  claim 1 , wherein the shoulder backup cutter density of the at least one primary blade is zero.  
   
   
       5 . The drill bit of  claim 3 , wherein the gage backup cutter density of the at least one primary blade is zero.  
   
   
       6 . The drill bit of  1  further comprising a central axis and an outer radius, wherein the cone region extends from the central axis to no more than 50% of the outer radius.  
   
   
       7 . The drill bit of  claim 6 , wherein the cone region extends from the central axis to no more than 30% of the outer radius.  
   
   
       8 . The drill bit of  claim 1 , wherein each primary cutter element includes a primary cutting face and wherein each backup cutter element includes a backup cutting face, wherein the primary cutting faces are forward facing and the backup cutting faces are forward facing.  
   
   
       9 . The drill bit of  claim 1 , wherein each primary cutter element includes a primary cutting face and wherein each backup cutter element includes a backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is substantially eclipsed by a primary cutting face.  
   
   
       10 . The drill bit of  claim 1 , wherein each primary cutter element includes a primary cutting face and wherein each backup cutter element includes a backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is partially eclipsed by a primary cutting face.  
   
   
       11 . The drill bit of  claim 1 , wherein the bit comprises no more than two primary blades.  
   
   
       12 . A drill bit for drilling a borehole in earthen formations, the bit comprising: 
 a bit body with a central axis and an outer radius;    a bit face comprising an inner region extending from the central axis to no more than 50% of the outer radius, and an outer region between the inner region and the outer radius;    at least one primary blade disposed on the bit face, wherein the at least one primary blade extends from proximal the central axis into the outer region;    a plurality of primary cutter elements mounted on the at least one primary blade;    a plurality of backup cutter elements mounted on the at least one primary blade;    wherein the at least one primary blade has an inner backup cutter area and an outer backup cutter area; and    wherein the inner backup cutter area of the at least one primary blade is greater than the outer backup cutter area of the at least one primary blade.    
   
   
       13 . The drill bit of  claim 12 , wherein the inner region extends from the central axis to no more than 30% of the outer radius  
   
   
       14 . The drill bit of  claim 12 , wherein the plurality of primary cutter elements are arranged substantially in a first row along the at least one primary blade and the plurality of backup cutter elements are arranged substantially in a second row along the at least one primary blade.  
   
   
       15 . The drill bit of  claim 12 , wherein the outer backup cutter area of the at least one primary blade is zero.  
   
   
       16 . The drill bit of  claim 12 , wherein each primary cutter element includes a primary cutting face and each backup cutter element includes a backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is substantially eclipsed by a primary cutting face.  
   
   
       17 . The drill bit of  claim 12 , wherein each primary cutter element includes a primary cutting face and each backup cuter element includes a backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is partially eclipsed by a primary cutting face.  
   
   
       18 . The drill bit of  claim 12 , wherein the bit comprises no more than three primary blades.  
   
   
       19 . The drill bit of  claim 18 , wherein the bit comprises no more than two primary blades.  
   
   
       20 . A drill bit for drilling a borehole in earthen formations, the bit comprising: 
 a bit body having a central axis and a bit face comprising a cone region, a shoulder region, and a gage region;    at least one primary blade disposed on the bit face, wherein the at least one primary blade begins substantially proximal the central axis and extends towards the gage region;    at least one secondary blade disposed on the bit face, wherein the at least one secondary blade begins at a radial distance “D” from the central axis and extends toward the gage region, the radial distance “D” being a radius defining the cone region;    a plurality of primary cutter elements mounted on the at least one primary blade, wherein the primary cutter elements are disposed in a first row extending along the at least one primary blade from substantially proximal the central axis toward the gage region;    a plurality of backup cutter elements mounted on the at least one primary blade, wherein the backup cutter elements are disposed in a second row extending along the at least one primary blade within the cone region.    
   
   
       21 . The drill bit of  claim 20 , wherein the bit body further comprises an outer radius, wherein the distance “D” is no more than 50% of the outer radius.  
   
   
       22 . The drill bit of  claim 20 , wherein the bit body further comprises an outer radius, wherein the distance “D” is no more than 30% of the outer radius.  
   
   
       23 . The drill bit of  claim 21 , wherein the at least one primary blade has a cone backup cutter density and a shoulder backup cutter density.  
   
   
       24 . The drill bit of  claim 23 , wherein the cone backup cutter density of the at least one primary blade is greater than the shoulder backup cutter density of the at least one primary blade.  
   
   
       25 . The drill bit of  claim 24 , wherein the shoulder backup cutter density of the at least one primary blade is zero.  
   
   
       26 . The drill bit of  claim 21 , wherein the at least one primary blade has a cone backup cutter area and a shoulder backup cutter area.  
   
   
       27 . The drill bit of  claim 26 , wherein the cone backup cutter area of the at least one primary blade is greater than the shoulder backup cutter area of the at least one primary blade.  
   
   
       28 . The drill bit of  claim 27 , wherein the shoulder backup cutter area of the at least one primary blade is zero.  
   
   
       29 . A drill bit for drilling a borehole in earthen formations, the bit comprising: 
 a bit body having a central axis and a bit face comprising a cone region, a shoulder region, and a gage region;    at least one primary blade disposed on the bit face, wherein the at least one primary blade begins proximal the central axis and extends toward the gage region;    a plurality of primary cutter elements mounted on the at least one primary blade in the cone region;    a plurality of backup cutter elements mounted on the at least one primary blade in the cone region; and    wherein the at least one primary blade is free of backup cutter elements in the shoulder region.    
   
   
       30 . The drill bit of  claim 29 , wherein the plurality of primary cutter elements are arranged in a first row along the at least one primary blade, and wherein the plurality of backup cutter elements are arranged in a second row along the at least one primary blade substantially parallel to the first row.  
   
   
       31 . The drill bit of  claim 29 , wherein the at least one primary blade is free of backup cutter elements in the gage region.  
   
   
       32 . The drill bit of  claim 29 , wherein each primary cutter element has a forward-facing primary cutting face and wherein each backup cutter element has a forward-facing backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is substantially eclipsed by a primary cutting face.  
   
   
       33 . The drill bit of  claim 29 , wherein each primary cutter element has a forward-facing primary cutting face and wherein each backup cutter element has a forward-facing backup cutting face, wherein the primary cutter elements and the backup cutter elements are mounted on the at least one primary blade such that, in rotated profile, each backup cutting face is partially eclipsed by a primary cutting face.  
   
   
       34 . The drill bit of  claim 29 , wherein the bit further comprises an outer radius and at least one secondary blade, wherein the at least one secondary blade begins at a distance “D” from the central axis and extends toward the gage region.  
   
   
       35 . The drill bit of  claim 36 , wherein the distance “D” is no more than 50% of the outer radius.  
   
   
       36 . The drill bit of  claim 35 , wherein the distance “D” is no more than 30% of the outer radius.  
   
   
       37 . The drill bit of  claim 29 , wherein the bit comprises no more than three primary blades.  
   
   
       38 . The drill bit of  claim 37 , wherein the bit consists of two primary blades.  
   
   
       39 . The drill bit of  claim 38 , wherein the two primary blades are spaced generally opposite each other.