Percussion drilling apparatus and method for measurement while drilling

Abstract

A measurement tool for use in pneumatic percussion drilling comprises a body comprising one or more measuring instruments positioned in a drill string above a pneumatically operated hammer of the drill string.

1 .- 18 . (canceled) 
     
     
         19 . A measurement tool for use during pneumatic percussion drilling, the measurement tool comprising:
 a body comprising one or more measuring instruments positioned in a drill string above a pneumatically operated hammer of the drill string, wherein the drill string comprises a reverse circulation hammer drill.   
     
     
         20 . A measurement tool according to  claim 19 , wherein the body is positioned immediately above the pneumatically operated hammer. 
     
     
         21 . A measurement tool according to  claim 19 , wherein the measuring instrument comprises one or more orientation and/or inertial movement sensors. 
     
     
         22 . A measurement tool according to  claim 21 , wherein the measuring instrument comprises one or more gyroscopes. 
     
     
         23 . A measurement tool according to  claim 21 , wherein the measuring instrument comprises one or more accelerometers. 
     
     
         24 . A measurement tool according to  claim 19 , wherein the measuring instrument comprises a gamma ray detector. 
     
     
         25 . A measurement tool according to  claim 19 , wherein the measuring instrument is connected to the body by one or more dampers for dampening shock/vibration from the pneumatic percussion drilling that is experienced by the measuring instrument. 
     
     
         26 . A measurement tool according to  claim 19 , wherein the measuring instrument is within a compartment in an annular portion of the body. 
     
     
         27 . A measuring tool according to  claim 26 , wherein the compartment is within an outer diameter of the body. 
     
     
         28 . A measuring tool according to  claim 26 , wherein the compartment is within an annular portion of the body, radially outward of a fluid return channel. 
     
     
         29 . A measurement tool according to  claim 26 , wherein the compartment is within an annular portion of the body between fluid supply channels. 
     
     
         30 . A measurement tool according to  claim 26 , wherein the compartment is sized relative to the instrument so that movement of the instrument during percussion drilling is clear of the walls of the compartment. 
     
     
         31 . A measurement tool according to  claim 19 , wherein the body has one or more fluid supply channels and a fluid return channel. 
     
     
         32 . A drilling apparatus comprising a body comprising one or more measuring instruments positioned in a drill string above a pneumatically operated hammer of the drill string, wherein the drill string comprises a reverse circulation hammer drill. 
     
     
         33 . A method of measuring a measurement tool during reverse circulation (RC) pneumatic percussion drilling operations comprising the steps:
 drilling a hole using a drill string having an RC drill bit, a pneumatic hammer for the RC drill bit and a measuring instrument above the hammer; and   measuring the orientation of the tool as the hole is being drilled.   
     
     
         34 . A method according to  claim 33 , wherein during each pause in drilling the measuring instrument takes a measurement. 
     
     
         35 . A method according to  claim 34 , wherein the measurement comprises a calibration measurement. 
     
     
         36 . A method according to  claim 34 , wherein the pause in drilling comprises an addition or removal of a drill rod. 
     
     
         37 . A method according to  claim 35 , wherein the measurement comprises taking a first measurement at a first position then rotating 180 degrees and taking a second measurement at a second position. 
     
     
         38 . A method according to  claim 37 , wherein the first measurement is recorded when at the second position and the second measurement is recorded at the first position. 
     
     
         39 . A method according to  claim 33 , wherein the method further comprises damping vibrations/shock experienced by the measuring instrument. 
     
     
         40 . A measurement tool according to  claim 19 , wherein the measurement tool is connected immediately above the hammer in place of a standard drill rod in the drill string.