Fixed cutter drill bits including cutter elements with variable exposures

Abstract

A fixed cutter drill bit for drilling an earthen formation includes a bit body having a central axis and a bit face. The bit body is configured to rotate about the central axis in a cutting direction of rotation. The bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit. The drill bit also includes a cutting structure disposed on the bit face. The cutting structure includes a primary blade extending radially from proximal the bit axis through the cone region and the shoulder region to the gage region. The blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side. In addition, the drill bit includes a plurality of cutter elements mounted to the cutter-supporting surface of the primary blade in the cone region, the shoulder region, and the gage region. The cutter elements are arranged in a row proximal the leading side of the primary blade and extending radially from the cone region proximal the bit axis to a gage pad extending from the primary blade. The plurality of cutter elements comprises a plurality of high-aspect ratio cutter elements in the cone region. Each cutter element has an exposure H measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the cutter element distal the primary blade. The exposure H of one or more of the high-aspect ratio cutter elements in the cone region is greater than the exposure H of one or more cutter elements in the shoulder region and the gage region.

What is claimed is: 
     
         1 . A fixed cutter drill bit for drilling an earthen formation, the drill bit comprising:
 a bit body having a central axis and a bit face, wherein the bit body is configured to rotate about the central axis in a cutting direction of rotation, wherein the bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit;   a cutting structure disposed on the bit face, wherein the cutting structure includes a primary blade extending radially from proximal the bit axis through the cone region and the shoulder region to the gage region, wherein the blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side; and   a plurality of cutter elements mounted to the cutter-supporting surface of the primary blade in the cone region, the shoulder region, and the gage region, wherein the cutter elements are arranged in a row proximal the leading side of the primary blade and extending radially from the cone region proximal the bit axis to a gage pad extending from the primary blade;   wherein the plurality of cutter elements comprises a plurality of high-aspect ratio cutter elements in the cone region;   wherein each cutter element has an exposure H measured perpendicularly from the cutter-supporting surface of the primary blade to a cutting tip of the cutter element distal the primary blade;   wherein the exposure H of one or more of the high-aspect ratio cutter elements in the cone region is greater than the exposure H of one or more cutter elements in the shoulder region and the gage region.   
     
     
         2 . The fixed cutter drill bit of  claim 1 , wherein each high-aspect ratio cutter element has a central axis, a leading end relative to the cutting direction of rotation, a trailing end relative to the cutting direction of rotation and opposite the leading end, a cutting face at the leading end, a longitudinal axis oriented perpendicular to the central axis, a length measured parallel to the longitudinal axis and a width measured perpendicular to the longitudinal axis, wherein the central axis intersects the leading end and the trailing end;
 wherein each high-aspect ratio cutter element has an aspect ratio equal to the ratio of the length of the high-aspect ratio cutter element to the width of the high-aspect ratio cutter element, wherein the aspect ratio of each high-aspect ratio cutter element is greater than 1.0 and less than or equal to 2.0.   
     
     
         3 . The fixed cutter drill bit of  claim 1 , wherein the exposure H of one or more of the high-aspect ratio cutter elements in the cone region is at least 1.5 times greater than the exposure H of each cutter element in the shoulder region and the gage region. 
     
     
         4 . The fixed cutter drill bit of  claim 3 , wherein the exposure H of each high-aspect ratio cutter element in the cone region ranges from 6.0 mm to 15.0 mm and the exposure H of each cutter element in the shoulder region and the gage region ranges from 5.0 mm to 20.0 mm. 
     
     
         5 . The drill bit of  claim 1 , wherein each pair of radially adjacent cutter elements is spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent cutter elements;
 wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region is greater than the minimum distance D between each pair of radially adjacent cutter elements in the shoulder region and the gage region.   
     
     
         6 . The fixed cutter drill bit of  claim 5 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region ranges from 4.0 mm to 20.0 mm and the minimum distance D between each pair of radially adjacent cutter elements in the shoulder region and the gage region ranges from 1.0 mm to 3.0 mm. 
     
     
         7 . The fixed cutter drill bit of  claim 6 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region ranges from 10.0 mm to 12.0 mm. 
     
     
         8 . The fixed cutter drill bit of  claim 5 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region is at least 1.5 times the minimum distance D between each pair of radially adjacent cutter elements in the shoulder region and the gage region. 
     
     
         9 . The fixed cutter drill bit of  claim 8 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region is at least 2.0 times the minimum distance D between each pair of radially adjacent cutter elements in the shoulder region and the gage region. 
     
     
         10 . The fixed cutter drill bit of  claim 1 , wherein each cutter element in the cone region is a high-aspect ratio cutter element. 
     
     
         11 . The fixed cutter drill bit of  claim 1 , wherein the plurality of cutter elements comprises a plurality of low-aspect ratio cutter elements in the shoulder region or the gage region. 
     
     
         12 . The drill bit of  claim 11 , wherein each pair of radially adjacent cutter elements is spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent cutter elements;
 wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements is substantially the same as the minimum distance D between each pair of radially adjacent low-aspect ratio cutter elements.   
     
     
         13 . The drill bit of  claim 1 , wherein each pair of radially adjacent cutter elements is spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent cutter elements;
 wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements in the cone region is substantially the same as the minimum distance D between each pair of radially adjacent cutter elements in the shoulder region and the gage region.   
     
     
         14 . The fixed cutter drill bit of  claim 1 , wherein the plurality of cutter elements comprises:
 the plurality of high-aspect ratio cutter elements arranged in the row extending radially from proximal the central axis of the drill bit through the cone region and into the shoulder region;   a plurality of low-aspect ratio cutter elements arranged in the row and extending radially from the plurality of high-aspect ratio cutter elements in the shoulder region through the shoulder region and the gage region to the gage pad.   
     
     
         15 . The fixed cutter drill bit of  claim 1 , wherein the plurality of cutter elements comprises:
 the plurality of high-aspect ratio cutter elements arranged in the row extending radially from proximal the central axis of the drill bit through the cone region and the shoulder region to the gage region   a plurality of low-aspect ratio cutter elements arranged in the row and extending radially through the gage region to the gage pad.   
     
     
         16 . The fixed cutter drill bit of  claim 1 , wherein each high-aspect ratio cutter element has a central axis, a leading end relative to the cutting direction of rotation, a trailing end relative to the cutting direction of rotation and opposite the leading end, a cutting face at the leading end, a longitudinal axis oriented perpendicular to the central axis, wherein the central axis intersects the leading end and the trailing end;
 wherein one or more of the high-aspect ratio cutter element is oriented at a non-zero tilt angle α measured in a front view of the primary blade from the longitudinal axis of the high-aspect ratio cutter element to a reference axis A passing through a cutting tip of the high-aspect ratio cutter element and oriented perpendicular to a cutting profile of the plurality of cutter elements mounted to the primary blade.   
     
     
         17 . A fixed cutter drill bit for drilling an earthen formation, the drill bit comprising:
 a bit body having a central axis and a bit face, wherein the bit body is configured to rotate about the central axis in a cutting direction of rotation, wherein the bit face includes a concave cone region extending radially from the central axis, a convex shoulder region extending radially from the cone region, a nose at the intersection of the cone region and the shoulder region, and a gage region extending radially from the shoulder region to a full gage diameter of the drill bit;   a cutting structure disposed on the bit face, wherein the cutting structure includes a plurality of circumferentially-spaced primary blades, wherein each primary blade extends radially from proximal the bit axis through the cone region and the shoulder region to the gage region, wherein each primary blade has a leading side relative to the cutting direction of rotation, a trailing side relative to the cutting direction of rotation, and a cutter-supporting surface extending from the leading side to the trailing side;   a plurality of gage pads, wherein each gage pad extends from an end of each primary blade distal the bit axis in the gage region;   a plurality of high-aspect ratio cutter elements mounted to the cutter-supporting surface of each primary blade and arranged in a row proximal the leading side of the primary blade that extends radially from proximal the bit axis through the cone region to the shoulder region, into the shoulder region, or to the gage region; and   a plurality of low-aspect ratio cutter elements mounted to the cutter-supporting surface of each primary blade and arranged in a row proximal the leading side of the primary blade that extends radially from the row of high-aspect ratio cutter elements through the shoulder region or the gage region to the gage pad.   
     
     
         18 . The fixed cutter drill bit of  claim 17 , wherein each high-aspect ratio cutter element has a central axis, a leading end relative to the cutting direction of rotation, a trailing end relative to the cutting direction of rotation and opposite the leading end, a cutting face at the leading end, a longitudinal axis oriented perpendicular to the central axis, a length measured parallel to the longitudinal axis and a width measured perpendicular to the longitudinal axis, wherein the central axis intersects the leading end and the trailing end;
 wherein each high-aspect ratio cutter element has an aspect ratio equal to the ratio of the length of the high-aspect ratio cutter element to the width of the high-aspect ratio cutter element, wherein the aspect ratio of each high-aspect ratio cutter element is greater than 1.0 and less than or equal to 2.0.   
     
     
         19 . The fixed cutter drill bit of  claim 17 , wherein each pair of radially adjacent high-aspect ratio cutter elements on each primary blade are spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent high-aspect ratio cutter elements;
 wherein each pair of radially adjacent low-aspect ratio cutter elements on each blade are spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent low-aspect ratio cutter elements;   wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements is greater than the minimum distance D between each pair of radially adjacent low-aspect ratio cutter elements.   
     
     
         20 . The fixed cutter drill bit of  claim 19 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements ranges from 4 mm to 20 mm and the minimum distance D between each pair of radially adjacent low-aspect ratio cutter elements ranges from 1.0 mm to 3.0 mm. 
     
     
         21 . The fixed cutter drill bit of  claim 19 , wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements is at least 1.5 times the minimum distance D between each pair of radially adjacent low-aspect ratio cutter elements. 
     
     
         22 . The fixed cutter drill bit of  claim 17 , wherein each pair of radially adjacent high-aspect ratio cutter elements on each primary blade are spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent high-aspect ratio cutter elements;
 wherein each pair of radially adjacent low-aspect ratio cutter elements on each blade are spaced apart a minimum distance D measured parallel to the cutter-supporting surface of the primary blade between the pair of radially adjacent low-aspect ratio cutter elements;   wherein the minimum distance D between each pair of radially adjacent high-aspect ratio cutter elements is substantially the same as the minimum distance D between each pair of radially adjacent low-aspect ratio cutter elements.   
     
     
         23 . The fixed cutter drill bit of  claim 17 , wherein each high-aspect ratio cutter element has an exposure H measured perpendicularly from the cutter-supporting surface of the corresponding primary blade to a cutting tip of the high-aspect ratio cutter element distal the corresponding primary blade;
 wherein each low-aspect ratio cutter element has an exposure H measured perpendicularly from the cutter-supporting surface of the corresponding primary blade to a cutting tip of the low-aspect ratio cutter element distal the corresponding primary blade;   wherein the exposure H of one or more high-aspect ratio cutter elements is greater than the exposure H of each low-aspect ratio cutter element.   
     
     
         24 . The fixed cutter drill bit of  claim 23 , wherein the exposure H of each of the low aspect-ratio cutter elements is the same;
 wherein the exposure H of the radially outermost high-aspect cutter element positioned radially adjacent the row of the low-aspect ratio cutter elements is the same as the exposure H of each of the low aspect-ratio cutter elements;   wherein the exposure H of each high-aspect ratio cutter element radially positioned between the central axis of the drill bit and the radially outermost high-aspect ratio cutter element is greater than the exposure of each low-aspect ratio cutter element.   
     
     
         25 . The fixed cutter drill bit of  claim 24 , wherein the exposure H of each high-aspect ratio cutter element radially positioned between the central axis of the drill bit and the radially outermost high-aspect ratio cutter element is at least 1.25 times greater than the exposure H of each low-aspect ratio cutter element. 
     
     
         26 . The fixed cutter drill bit of  claim 18 , wherein one or more high-aspect ratio cutter elements is oriented at a non-zero tilt angle α measured in a front view of the corresponding primary blade from the longitudinal axis of the high-aspect cutter element to a reference axis A passing through a cutting tip of the high-aspect ratio cutter element and oriented perpendicular to a cutting profile of the plurality of cutter elements mounted to the primary blade.