Steerable fixed cutter drill bit

Abstract

A fixed cutter drill bit includes a plurality of gage pads, where certain of the gage pads have an active cutting region adjacent to the end of the gage pad adjacent to the bit face, and a passive region at the end of the gage pad adjacent to the pin-end of the bit. The active regions include forward-facing cutter elements. Other gage pads include an active region on the end adjacent to the pin-end, and a passive region on the gage pad end adjacent to the bit face. The passive and active regions have lengths within the range of 40 to 60 percent of the total axial length of the gage pads. A passive gage pad is positioned on the bit between the gage pads having both active and passive regions.

1 . A drill bit for drilling a borehole having a predetermined full gage diameter, the bit comprising: 
 a bit body having a bit face with a cutting structure thereon, and a pin end opposite the bit face;    at least a first and a second gage pad positioned on the bit body between the bit face and the pin end, wherein the second gage pad is angularly spaced apart from the first gage pad;    wherein the first gage pad comprises a first axial length, an active region including a plurality of generally forward-facing cutter elements having cutting surfaces extending substantially to full gage diameter, and a passive region including a gage-facing surface extending substantially to gage diameter, wherein each of the active and passive regions has a length between 40 and 60 percent of the first axial length; and    wherein the second gage pad comprises a second axial length, a gage-facing surface extending substantially to full gage diameter, and a passive cutting region along substantially all of the second axial length.    
   
   
       2 . The drill bit of  claim 1  wherein the length of the active region of the first gage pad is within the range of 45-55 percent of the first axial length.  
   
   
       3 . The drill bit of  claim 1  wherein the active region of the first gage pad is positioned proximal the bit face.  
   
   
       4 . The drill bit of  claim 1  wherein the active region of the first gage pad is positioned proximal the pin-end.  
   
   
       5 . The drill bit of  claim 1  wherein the first gage pad is disposed at an angular position immediately adjacent the second gage pad.  
   
   
       6 . The drill bit of  claim 1  wherein the cutting surface of each forward-facing cutter element has a cutting face surface area, wherein at least two of the forward-facing cutter elements have cutting surfaces with different cutting face surface areas.  
   
   
       7 . The drill bit of  claim 1  wherein the active region of the first gage pad includes a gage-facing surface and wherein the gage-facing surface of the active region and passive region of the first gage pad are substantially parallel to the bit axis.  
   
   
       8 . The drill bit of  claim 1  wherein the active region of the first gage pad includes a gage-facing surface including a tapered portion oriented at an angle between 0° and 10° relative to the bit axis.  
   
   
       9 . The drill bit of  claim 8  wherein the tapered portion is oriented at an angle between 7° and 10° relative to the bit axis.  
   
   
       10 . A drill bit for forming a borehole in earthen formations, the bit comprising: 
 a bit body having a bit axis, a bit face, and a pin end opposite the bit face;    a plurality of gage pads having first and second ends and disposed about the bit body at angularly spaced-apart positions, the first end of each gage pad being closer to the bit face than to the pin end;    a first of the plurality of gage pads having a length and comprising an active region including a plurality of forward-facing cutter elements and a passive region, each of the active and passive regions of the first gage pad having a length of at least 40 percent of the length of the first gage pad; and    a second of the plurality of gage pads disposed at an angular position immediately adjacent to the first gage pad, the second gage pad having a length and comprising a passive region along substantially the entire length of the second gage pad.    
   
   
       11 . The drill bit of  claim 10  wherein the active region of the first of the plurality of gage pads is positioned adjacent the first end of the first gage pad and wherein the passive region of the first of the plurality of gage pads is positioned adjacent the second end of the first gage pad.  
   
   
       12 . The drill bit of  claim 11  further comprising: 
 a third of the plurality of gage pads disposed at an angular position immediately adjacent to the second gage pad such that the second gage pad is disposed between the first and third gage pads, the third gage pad having a length and comprising an active region including a plurality of forward-facing cutter elements adjacent to the second end of the third gage pad and a passive region adjacent to the first end of the third gage pad, the active and passive regions of the third gage pad each having a length of at least 40 percent of the length of the third gage pad.    
   
   
       13 . The drill bit of  claim 12  further comprising a fourth gage pad disposed at an angular position immediately adjacent to the third gage pad such that the third gage pad is disposed between the second gage pad and the fourth gage pad, the fourth gage pad having a length and comprising a passive region along substantially the entire length of the fourth gage pad.  
   
   
       14 . The drill bit of  claim 10  wherein the active region of the first of the plurality of gage pads is positioned adjacent the second end of the first gage pad and wherein the active region of the first of the plurality of gage pads is positioned adjacent the second end of the first gage pad.  
   
   
       15 . The drill bit of  claim 14  further comprising: 
 a third of the plurality of gage pads disposed at an angular position immediately adjacent to the second gage pad such that the second gage pad is disposed between the first and third gage pads, the third gage pad having a length and comprising an active region including a plurality of forward-facing cutter elements adjacent to the first end of the third gage pad and a passive region adjacent to the second end of the third gage pad, the active and passive regions of the third gage pad each having a length of at least 40 percent of the length of the third gage pad.    
   
   
       16 . The drill bit of  claim 15  further comprising a fourth gage pad disposed at an angular position immediately adjacent to the third gage pad such that the third gage pad is disposed between the second gage pad and the fourth gage pad, the fourth gage pad having a length and comprising a passive region along substantially the entire length of the fourth gage pad.  
   
   
       17 . The drill bit of  claim 10  wherein each of the forward-facing cutter elements of the active region of the first gage pad extends substantially to a predetermined full gage diameter.  
   
   
       18 . The drill bit of  claim 10  wherein the first and second of the plurality of gage pads each includes a gage-facing surface including at least a portion that extends substantially to a predetermined full gage diameter and is substantially parallel to the bit axis.  
   
   
       19 . The drill bit of  claim 15  wherein the gage-facing surface of the first of the plurality of gage pads comprises a tapered portion oriented at angle between 0° and 10° relative to the bit axis.  
   
   
       20 . A drill bit for cutting a borehole at a predetermined full gage diameter, the bit comprising: 
 a bit body having at least eight gage pads disposed about the body at angularly spaced-apart positions;    a bit face on the bit body, the bit face comprising a cutting structure cutting the borehole to the full gage diameter;    a pin end on the bit body opposite the bit face;    wherein a first and a second of the gage pads each comprises a plurality of forward-facing cutter elements forming an active cutting region that is closer to the bit face than to the pin end, and a passive region closer to the pin end than to the bit face;    wherein a third and a fourth of the gage pads each comprises a plurality of forward-facing cutter elements forming an active cutting region that is closer to the pin-end than to the bit face, and a passive region that is closer to the bit face than to the pin-end;    wherein the gage pads are angularly spaced about the bit such that each of the first and second gage pads is disposed at a location that is between the third and fourth gage pads; and    wherein four other of the at least eight gage pads includes only a passive cutting region.    
   
   
       21 . The drill bit of  claim 20  wherein one of the four other gage pads is angularly positioned between two of the gage pads having the active and passive regions.  
   
   
       22 . The drill bit of  claim 20  wherein each of the forward-facing cutter elements of each active region extend substantially to the predetermined full gage diameter.  
   
   
       23 . The drill bit of  claim 20  wherein each of the eight gage pads includes a gage-facing surface having at least a portion that extends substantially to the predetermined full gage diameter.  
   
   
       24 . A drill bit for drilling through earthen formations and forming a borehole of a predetermined full gage diameter, the bit comprising: 
 a bit body;    a bit face on the body having a cutting structure for cutting the borehole to full gage diameter;    a pin end on said body opposite the bit face;    a plurality of gage pads angularly spaced about the bit body, each gage pad having a length;    wherein at least a first and a second of the gage pads each comprise forward-facing cutter elements that are positioned closer to the pin end than to the bit face, the first and second gage pads forming a first composite active cutting profile having a length equal to between 40 and 60 percent of the length of the first gage pad, the first composite active cutting profile being located closer to the pin end of the bit than to the cutting face;    wherein each of the first and second gage pads further includes a passive cutting region positioned at a location closer to the bit face than to the pin end and forming a first composite passive cutting profile having a length of between 40-60 percent of the length of the first gage pad; and    a third gage pad disposed at an angular position between the first and second gage pads, wherein the third gage pad is passive.    
   
   
       25 . The drill bit of  claim 24  further comprising: 
 a fourth gage pad disposed an angular position between the first and third gage pads, wherein the fourth gage pad is passive.    
   
   
       26 . The drill bit of  claim 25  further comprising: 
 a fifth gage pad comprising forward-facing cutter elements forming an active cutting region that is closer to the bit face than to the pin end, and further comprising a passive region that is closer to the pin end than to the bit face; and    wherein the fifth gage pad is disposed an angular position between the third and fourth gage pad.    
   
   
       27 . The drill bit of  claim 24  further comprising a fourth and a fifth gage pad, each comprising forward-facing cutter elements that are positioned closer to the bit face than to the pin-end, the fourth and fifth gage pads forming a second composite active cutting profile having a length between 40 and 60 percent of the length of the first gage pad, the second composite active cutting profile being located closer to the bit face than to the pin-end; 
 wherein each of the fourth and a fifth gage pads further comprises a passive cutting region positioned at a location closer to the pin-end than to the bit face, and forming a second composite passive cutting profile having a length between 40 and 60 percent of the length of the first gage pad.    
   
   
       28 . The drill bit of  claim 27  wherein each of the fourth and a fifth gage pads is positioned at a different angular position, and positioned at an angular position that is between the first and second gage pads.  
   
   
       29 . The drill bit of  claim 28  wherein the bit further comprises at least one passive gage pad located at an angular position between each of the first, second, fourth and fifth gage pads.  
   
   
       30 . The drill bit of  claim 27  wherein the first composite active cutting profile overlaps with the second composite active cutting profile by no more than 10 percent of the length of the first gage pad.