Drilling assembly with underreaming bit and method of use

Abstract

Embodiments provide apparatuses and methods for drilling and underreaming, particularly to underreamer expansion bits. Underreamer drill assemblies and underreaming bits manufactured in accordance with various embodiments may help to resist over-excavating or undermining, which may result in a more stable bore hole.

1 . An underreamer drill assembly comprising:
 a center shaft having a central axis, a proximal end, and a distal end, wherein the center shaft is configured to receive drive energy from a driver at the proximal end and adapted to couple to a bit body at the distal end;   a bit body adapted to couple to the center shaft and configured to couple to at least one underreamer arm; and   at least one underreamer arm configured to underream a bore hole having a side wall, wherein the center shaft, bit body, and underreamer arm form a distal cutting face that is substantially perpendicular to the central axis, and wherein the underreamer drill assembly is configured to direct air, water, or flush media substantially away from the side wall of the bore hole.   
     
     
         2 . The underreamer drill assembly of  claim 1 , wherein the center shaft and bit body are adapted to direct air, water, or flush media substantially along the central axis and perpendicular to the distal cutting face. 
     
     
         3 . The underreamer drill assembly of  claim 1 , wherein the center shaft and bit body are adapted to direct air, water, and flush media substantially along the central axis and perpendicular to the distal cutting face. 
     
     
         4 . The underreamer drill assembly of  claim 1 , wherein the at least one underreamer arm is configured to be extended against the side wall of the bore hole. 
     
     
         5 . The underreamer drill assembly of  claim 1 , wherein the at least one underreamer arm comprises a distal pilot surface, a proximal upper surface, and an axial height spanning the distance between the distal pilot surface and the proximal upper surface. 
     
     
         6 . The underreamer drill assembly of  claim 5 , wherein the axial height is less than 8 inches. 
     
     
         7 . The underreamer drill assembly of  claim 5 , wherein the axial height is less than 6 inches. 
     
     
         8 . The underreamer drill assembly of  claim 5 , wherein the axial height is between about 2 and about 4 inches. 
     
     
         9 . The underreamer drill assembly of  claim 1 , wherein the distal cutting face comprises a plurality of compact cutting inserts. 
     
     
         10 . The underreamer drill assembly of  claim 9 , wherein the compact cutting inserts are replaceable. 
     
     
         11 . The underreamer drill assembly of  claim 9 , wherein the compact cutting inserts comprise carbide buttons. 
     
     
         12 . The underreamer drill assembly of  claim 1 , wherein the center shaft, bit body, and underreamer arms are modular. 
     
     
         13 . The underreamer drill assembly of  claim 12 , wherein the bit body is adapted to be removed and replaced with a second bit body having a different diameter. 
     
     
         14 . The underreamer drill assembly of  claim 12 , wherein the center shaft is adapted to be removed and replaced with a second center shaft that is adapted to couple to a different drive mechanism. 
     
     
         15 . The underreamer drill assembly of  claim 1 , wherein the center shaft comprises a drive adapter. 
     
     
         16 . The underreamer drill assembly of  claim 15 , wherein the drive adapter is configured to receive rotational torque, impact energy, vibration, or linear feed force from a drive mechanism. 
     
     
         17 . The underreamer drill assembly of  claim 16 , wherein the adapter is configured to move the center shaft in response to the rotational torque, impact energy, vibration, or linear feed force. 
     
     
         18 . The underreamer drill assembly of  claim 16 , wherein the drive mechanism is a down hole hammer or a drill rod for hydraulic hammer. 
     
     
         19 . The underreamer drill assembly of  claim 1 , wherein the center shaft is adapted at or near the distal end to couple to the bit body via a hex or spline drive mechanism. 
     
     
         20 . An underreamer drill assembly comprising:
 a center shaft having a central axis, a proximal end, and a distal end, wherein the center shaft is configured to receive drive energy from a driver at the proximal end and adapted to couple to a bit body via a hex drive mechanism at the distal end;   a bit body adapted to couple to the center shaft via the hex drive mechanism and configured to couple to at least one underreamer arm; and   at least one underreamer arm configured to underream a bore hole having a side wall;   
       wherein the center shaft, bit body, and underreamer arm form a distal cutting face that is substantially perpendicular to the central axis; 
       wherein the underreamer drill assembly is configured to direct air, water, or flush media substantially along the central axis and perpendicular to the distal cutting face; and 
       wherein the center shaft is configured to transmit drive energy from the driver to the at least one arm and move the at least one arm from a retracted position to an extended position.