Hybrid drill bit with high pilot-to-journal diameter ratio

Abstract

The invention disclosed and taught herein is directed to an improved hybrid drill bit and associated elements having at least two rolling cutters, each rotatable around separate spindles on the bit, and at least one fixed blade. The improved drill bit expands the pilot pin to journal diameter ratio within the body of the rolling cutter, but within the confines of the allowable space of the rolling cutter.

1 . A hybrid drill bit for use in drilling through subterranean formations, the hybrid drill bit comprising:
 a shank disposed about a longitudinal centerline and adapted to be coupled to a drilling string;   at least one fixed blade extending from the shank, the fixed blade comprising at least one cutting element extending from a surface of the fixed blade;   at least two rolling cutter legs extending from the shank, comprising a spindle having an axis of rotation, the spindle comprising:
 a journal disposed about the axis of rotation, the journal having a journal diameter; and 
 a pilot pin coupled to the journal and extending along the axis of rotation toward the longitudinal centerline, the pilot pin having a pilot pin diameter, the pilot pin diameter to journal diameter having a ratio of equal to or greater than 0.60; and 
   at least two rolling cutters coupled to the rolling cutter legs distally from the shank and adapted to rotate about the axis of rotation on the journal and pilot pin, the rolling cutters comprising cutting elements extending from a surface of the rolling cutters.   
   
   
       2 . The hybrid drill bit of  claim 1 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.60 and less than or equal to 1.0. 
   
   
       3 . The hybrid drill bit of  claim 1 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.70 and less than or equal to 1.0. 
   
   
       4 . The hybrid drill bit of  claim 1 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.80 and less than or equal to 1.0. 
   
   
       5 . The hybrid drill bit of  claim 1 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.90 and less than or equal to 1.0. 
   
   
       6 . The hybrid drill bit of  claim 1 , further comprising a bearing disposed around the journal, the pilot pin, or a combination thereof, the bearing having a contact length along the axis of rotation with the journal, the pilot pin, or a combination thereof. 
   
   
       7 . The hybrid drill bit of  claim 6 , wherein the pilot pin diameter to journal diameter ratio is calculated including the bearing on the journal, pilot pin, or a combination thereof. 
   
   
       8 . The hybrid drill bit of  claim 1 , wherein the rolling cutters comprise an end having a truncated surface. 
   
   
       9 . The hybrid drill bit of  claim 1 , wherein the pilot pin comprises a thrust face approximately perpendicular to the axis of rotation. 
   
   
       10 . A hybrid drill bit for use in drilling through subterranean formations, the hybrid drill bit comprising:
 a shank disposed about a longitudinal centerline and adapted to be coupled to a drilling string;   at least one fixed blade extending from the shank, the fixed blade comprising at least one cutting element extending from a surface of the fixed blade;   at least two rolling cutter legs extending from the shank, comprising a spindle having an axis of rotation, the spindle comprising:
 a journal disposed about the axis of rotation, the journal having a journal diameter; and 
 a pilot pin coupled to the journal and extending along the axis of rotation toward the longitudinal centerline, the pilot pin having a pilot pin diameter, the pilot pin diameter to journal diameter having a ratio of equal to or greater than 0.60. 
   
   
   
       11 . The hybrid drill bit of  claim 10 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.60 and less than or equal to 1.0. 
   
   
       12 . The hybrid drill bit of  claim 10 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.70 and less than or equal to 1.0. 
   
   
       13 . The hybrid drill bit of  claim 10 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.80 and less than or equal to 1.0. 
   
   
       14 . The hybrid drill bit of  claim 10 , wherein the pilot pin diameter to journal diameter ratio is equal to or greater than 0.90 and less than or equal to 1.0. 
   
   
       15 . The hybrid drill bit of  claim 10 , further comprising a bearing disposed around the journal, the pilot pin, or a combination thereof, the bearing having a contact length along the axis of rotation with the journal, the pilot pin, or a combination thereof. 
   
   
       16 . The hybrid drill bit of  claim 15 , wherein the pilot pin diameter to journal diameter ratio is calculated including the bearing on the journal, pilot pin, or a combination thereof. 
   
   
       17 . The hybrid drill bit of  claim 10 , wherein the pilot pin comprises a thrust face approximately perpendicular to the axis of rotation.