Active gauge protection for drill bits

Abstract

A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, the drill bit comprising a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter; and a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.

1 . A drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, the drill bit comprising:
 a blade comprising a gauge cutter operable to cut an earth formation at the gauge diameter; and   a protective insert coupled the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance, wherein the protective insert is operable to engage the casing inner wall to substantially prevent the gauge cutter from engaging the casing inner wall as the drill bit is positioned through a selected length of the casing.   
     
     
         2 . The drill bit of  claim 1 , wherein the protective insert ablates at a greater rate than the gauge cutter. 
     
     
         3 . The drill bit of  claim 2 , wherein the protective insert comprises a tungsten carbide insert. 
     
     
         4 . The drill bit of  claim 2 , wherein the protective insert comprises a matrix material. 
     
     
         5 . The drill bit of  claim 2 , wherein the protective insert comprises a diamond impregnated insert. 
     
     
         6 . The drill bit of  claim 2 , wherein the protective insert is operable to ablate to allow the gauge cutter to engage the rock formation. 
     
     
         7 . The drill bit of  claim 6 , wherein the protective insert ablates from about the overgauge distance to about gauge diameter once the drill bit engages the rock formation. 
     
     
         8 . The drill bit of  claim 7 , wherein the protective insert is positioned adjacent to the gauge cutter. 
     
     
         9 . The drill bit of  claim 8 , wherein the protective insert is positioned on the drill bit at about 90 degrees to a vertical centerline of the drill bit. 
     
     
         10 . The drill bit of  claim 9 , wherein the protective insert comprises a smooth bearing surface operable to allow the drill bit to rotate within the casing. 
     
     
         11 . The drill bit of  claim 10 , wherein the overgauge distance is about the drift distance. 
     
     
         12 . The drill bit of  claim 10 , wherein the overgauge distance is less than the drift distance. 
     
     
         13 . The drill bit of  claim 12 , wherein the overgauge distance is a range from about 0.005″ to about 0.050″. 
     
     
         14 . The drill bit of  claim 10 , wherein the protective insert comprises a substantially dome shaped surface. 
     
     
         15 . The drill bit of  claim 10 , wherein the protective insert comprises a substantially elliptical shaped surface. 
     
     
         16 . The drill bit of  claim 14 , wherein the protective insert is brazed to the drill bit. 
     
     
         17 . A method of protecting a gauge cutter of a drill bit having a selected gauge diameter and operable to be positioned within a casing positioned within a rock formation, the casing comprising an casing inner wall having a casing inner diameter greater than the gauge diameter, wherein the positioning of the drill bit within the casing defines a drift distance corresponding to the distance between the gauge diameter and the casing inner diameter, comprising the steps of:
 positioning a protective insert on the drill bit such that a portion of the protective insert extends beyond the gauge diameter by a selected overgauge distance;   positioning the drill bit within the casing; and   substantially preventing the gauge cutter from contacting the casing inner wall along a selected length of the casing.   
     
     
         18 . The method of  claim 17 , further comprising the step of abrading the protective insert to about gauge diameter to allow the gauge cutter to engage the rock formation. 
     
     
         19 . The method of  claim 18 , further comprising the step of allowing the drill bit to rotate within the casing. 
     
     
         20 . The method of  claim 19 , further comprising the step of absorbing a portion of the impact of the drill bit contacting the casing inner wall. 
     
     
         21 . The method of  claim 19 , further comprising the step of centering the drill bit within the casing inner wall for a selected length of the casing.