Gage configurations for drill bits

Abstract

A drill bit includes a plurality of cutting elements are positioned on the at least two roller cones, wherein cutting elements contributing to an operative gage row of the drill bit comprise less than 31 percent of a total cutting elements of the drill bit that contact the bottom of the borehole. A method to design a roller cone drill bit includes designing an initial bit, testing the initial bit; and adjusting the bit design to optimize at least one of rate of penetration and wear resistance, wherein cutting elements contributing to an operative gage row of the adjusted bit design comprise less than 31 percent of a total of cutting elements on the adjusted bit design that contact a bottom of a borehole.

1 . A drill bit to drill a borehole to a predetermined gage, the drill bit comprising:
 a bit body having a bit axis;   at least two roller cones rotatably secured to the bit body, wherein the at least two roller cones have a generally conical surface and an adjacent heel surface, wherein the heel and conical surfaces form a circumferential shoulder therebetween; and   a plurality of cutting elements positioned on the at least two roller cones;   wherein cutting elements contributing to an operative gage row of the drill bit comprise less than 31 percent of a total of cutting elements of the drill bit that contact a bottom of the borehole.   
   
   
       2 . The drill bit of  claim 1 , wherein cutting elements contributing to the operative gage row of the drill bit comprise less than 29 percent of the total of cutting elements of the drill bit that contact the bottom of the borehole. 
   
   
       3 . (canceled) 
   
   
       4 . The drill bit of  claim 1 , wherein at least one roller cone comprises at least one circumferential row of off-bottom cutting elements positioned on at least one of the heel surface, the conical surface, and the circumferential shoulder. 
   
   
       5 . The drill bit of  claim 4 , wherein the off-bottom cutting elements are at least 0.100 inches from contacting the bottom of the borehole prior to any wear on the bit. 
   
   
       6 . (canceled) 
   
   
       7 . The drill bit of  claim 4 , wherein the off-bottom cutting elements are smaller than the gage inserts contacting the bottom of the borehole. 
   
   
       8 . (canceled) 
   
   
       9 . The drill bit of  claim 1 , wherein at least one roller cone comprises at least one circumferential row of off-bottom cutting elements, wherein at least one cutting element of the circumferential row of off-bottom cutting elements has a geometry selected from the group consisting of weighted profiles, t-crests, bowed slant crests, flat slant crests, conical elements, and semi-round top elements. 
   
   
       10 . The drill bit of  claim 1 , wherein at least one roller cone comprises a circumferential row of off-gage cutting elements positioned on a portion of the conical surface and that contacts the bottom of the borehole. 
   
   
       11 . The drill bit of  claim 10 , wherein the off gage cutting elements are offset from a gage curve a distance of at least 0.020 inches. 
   
   
       12 . (canceled) 
   
   
       13 . The drill bit of  claim 10 , wherein at least one cutting element of the circumferential row of off-gage cutting elements has a geometry selected from the group consisting of weighted profiles, t-crests, bowed slant crests, flat slant crests, conical elements, and semi-round top elements. 
   
   
       14 . (canceled) 
   
   
       15 . The drill bit of  claim 1 , wherein at least one roller cone comprises no cutting elements contributing to the operative gage row of the drill bit. 
   
   
       16 . The drill bit of  claim 15 , wherein the at least one roller cone comprises a circumferential row of off gage cutting elements positioned on a portion of the conical surface and that contact the bottom of the borehole. 
   
   
       17 . The drill bit of  claim 16 , wherein the at least one roller cone comprises at least one circumferential row of off-bottom cutting elements positioned on at teast one of the heel surface, the conical surface, and the circumferential shoulder. 
   
   
       18 . A drill bit to drill a borehole at a predetermined gage, the drill bit comprising:
 a bit body having a bit axis;   at least two roller cones rotatably secured to the bit body, the at least two roller cones having a generally conical surface and an adjacent heel surface, wherein the heel and conical surfaces form a circumferential shoulder therebetween; and   a plurality of cutting elements positioned on the at least two roller cones;   wherein at least one roller cone comprises no cutting elements contributing to an operative gage row of the drill bit.   
   
   
       19 . The drill bit of  claim 18 , wherein the at least one roller cone comprises at least one circumferential row of off-bottom cutting elements positioned on at least one of the group consisting of the heel surface, the conical surface, and the circumferential shoulder. 
   
   
       20 . (canceled) 
   
   
       21 . The drill bit of  claim 18 , wherein the at least one roller cone comprises a circumferential row of off-gage cutting elements positioned on a portion of the conical surface and that contact a bottom of the borehole. 
   
   
       22 . (canceled) 
   
   
       23 . The drill bit of  claim 21 , wherein the off-gage cutting elements are offset from a gage curve a distance of at least 0.020 inches. 
   
   
       24 . (canceled) 
   
   
       25 . The drill bit of  claim 21 , wherein the at least one roller cone comprises at least one circumferential row of off-bottom cutting elements positioned on at least one of the group consisting of the heel surface, the conical surface, and the circumferential shoulder. 
   
   
       26 . The drill bit of  claim 25 , wherein the off-bottom cutting elements comprise a harder material than the cuffing elements of the operative gage row of the drill bit. 
   
   
       27 . The drill bit of  claim 25 , wherein the off-gage cutting elements comprise a softer material than the cutting elements of the operative gage row of the drill bit. 
   
   
       28 . A method to design a roller cone drill bit, the method comprising:
 designing an initial bit, wherein the initial bit comprises:
 a bit body having a bit axis; 
 at least two roller cones rotatably secured to the bit body, wherein the at least two roller cones comprises a generally conical surface and an adjacent heel surface, wherein the heel and conical surfaces form a circumferential shoulder therebetween; and 
 a plurality of cutting elements positioned on the at least two roller cones; 
   testing the initial bit; and   adjusting the bit design to optimize at least one of rate of penetration and wear resistance;   wherein cutting elements contributing to an operative gage row of the adjusted bit design comprise less than 31 percent of a total of cutting elements on the adjusted bit design that contact a bottom of a borehole.   
   
   
       29 . The method of  claim 28 , wherein at least one roller cone comprises at least one circumferential row of off-bottom cutting elements positioned on at least one selected from the group consisting of the heel surface, the conical surface, and the circumferential shoulder, wherein the off-bottom cutting elements are at least 0.100 inches from contacting the bottom of the borehole. 
   
   
       30 . The method of  claim 28 , wherein at least one roller cone comprises no cutting elements contributing to the operative gage row of the drill bit, wherein the at least one roller cone comprises a circumferential row of off-gage cutting elements positioned on a portion of the conical surface and that contact the bottom of the borehole, and wherein the off-gage cutting elements are offset from a gage curve a distance of at least 0.020 inches. 
   
   
       31 . A roller cone drill bit comprising a cutting element, wherein the cutting element terminates in a T-shaped crest. 
   
   
       32 . The roller cone drill bit of  claim 31 , wherein the T-crest contacts a gage of a borehole during drilling. 
   
   
       33 . The roller cone drill bit of  claim 31 , wherein an extended portion of the T-crest cuts at gage.