Tri-cone bits for horizontal and hard formation drilling applications

Abstract

The present invention discloses a tri-cone drill bit comprising: three head sections with upper parts thereof jointed together to form a bit body, three cones rotatably mounted to lower ends of the head sections respectively, nozzle sockets designed on the bit body between respective head sections and each having a hole in which a nozzle is mounted, wherein gage cutters are mounted to an upper trailing side of each head O.D. surface to form a gage holding surface thereon, and a leading side of each head section is backwardly slanted as a whole. The design of gage surface at trailing sides of head sections increases the bit's stability, reduces lateral vibration and also reduces tendency of bit deflection in horizontal drilling applications and effective working life of the bit is improved. Backward slant of leading sides of head sections facilitates upward carrying of drilling cuttings and improves drilling efficiency. Jets from the nozzles are respectively directed to the leading side of each following cone, which enhances bottom hole cleaning and cooling of cutting elements and leads to a longer working life and higher ROP of the bit.

1 . A tri-cone drill bit for horizontal and hard formation drilling applications comprising:
 three head sections with upper parts thereof jointed together to form a bit body, three cones rotatably mounted to lower ends of respective head sections,   nozzle sockets designed on the bit body between respective head sections and each having a hole in which a nozzle is mounted,   wherein gage cutters are mounted to an upper trailing side of each head O.D. surface to form a gage surface thereon, and a leading side of each head section is backwardly slanted as a whole.   
   
   
       2 . The drill bit as defined in  claim 1  wherein said backward slant of the leading side of each head section is in the range of 10° to 50°. 
   
   
       3 . The drill bit as defined in  claim 2  wherein said backward slant of the leading side of each head section is in the range of 10° to 30°. 
   
   
       4 . The drill bit as defined in  claim 1  wherein a jet from said nozzle in each nozzle socket is directed to the leading side of a respective rotationally following cone. 
   
   
       5 . The drill bit as defined in  claim 2  wherein a jet from said nozzle in each nozzle socket is directed to the leading side of a respective rotationally following cone. 
   
   
       6 . The drill bit as defined in  claim 4  wherein a jet potential core of the jet from the nozzle has a minimum distance of zero from cutting elements of the rotationally following cone. 
   
   
       7 . The drill bit as defined in  claim 5  wherein a jet potential core of the jet from the nozzle has a minimum distance of zero from cutting elements of the rotationally following cone. 
   
   
       8 . The drill bit as defined in  claim 1  wherein a portion of the upper trailing side of each head O.D. surface where the gage cutters are mounted has a diameter less than the gage diameter by 0 to 2 mm. 
   
   
       9 . The drill bit as defined in  claim 2  wherein a portion of the upper trailing side of each head O.D. surface where the gage cutters are mounted has a diameter less than the gage diameter by 0 to 2 mm. 
   
   
       10 . The drill bit as defined in  claim 1  wherein said gage cutters are tungsten carbide inserts or diamond enhanced WC inserts. 
   
   
       11 . The drill bit as defined in  claim 2  wherein said gage cutters are tungsten carbide inserts or diamond enhanced WC inserts. 
   
   
       12 . The drill bit as defined in  claim 1  wherein each head O.D. surface have the upper trailing side extended backwardly by a certain distance where gage cutters are arranged. 
   
   
       13 . The drill bit as defined in  claim 1  wherein two or three rows of said gage cutters, with 2 to 3 gage cutters in each row, are mounted to head O.D. surfaces in a staggered manner. 
   
   
       14 . The drill bit as defined in  claim 12  wherein two or three rows of said gage cutters, with 2 to 3 gage cutters in each row, are mounted to head O.D. surfaces in a staggered fashion.