Determination of unconfined compressive strength from drilling data and drill bit parameters

Abstract

A method for monitoring a drilling operation includes: providing a drill bit for drilling a wellbore into a geological formation using a drilling motor for rotating the drill bit; determining depth of cut (DOC) of the drill bit and torque exerted on the drill bit by the drilling motor using parameters measured while drilling the wellbore; simulating drilling of a hypothetical wellbore using a hypothetical drill bit similar or identical to the drill bit and determining a function that provides strength of a hypothetical geological formation from the DOC of the hypothetical drill bit and the torque exerted on the hypothetical drill bit; and determining strength of the geological formation using the function and the determined DOC and the torque.

1 . A method for monitoring a drilling operation, comprising:
 providing a drill bit for drilling a wellbore into a geological formation using a drilling motor for rotating the drill bit;   determining depth of cut (DOC) of the drill bit and torque exerted on the drill bit by the drilling motor using parameters measured while drilling the wellbore;   simulating drilling of a hypothetical wellbore using a hypothetical drill bit similar or identical to the drill bit and determining a function that provides strength of a hypothetical geological formation from the DOC of the hypothetical drill bit and the torque exerted on the hypothetical drill bit; and   determining strength of the geological formation using the function and the determined DOC and the torque.   
     
     
         2 . The method of  claim 1 , further comprising:
 identifying a zone of interest of the geological formation using the determined strength thereof; and   drilling a lateral wellbore at the zone of interest.   
     
     
         3 . The method of  claim 1 , further comprising:
 identifying an unstable zone in the geological formation using the determined strength thereof; and   fracturing the geological formation at a buffer distance from the unstable zone.   
     
     
         4 . The method of  claim 1 , further comprising:
 drilling the wellbore into the geological formation using the drill bit and the drilling motor; and   measuring the parameters while drilling the wellbore.   
     
     
         5 . The method of  claim 4 , wherein:
 drilling the wellbore also uses a drilling rig,   the parameters are measured at the drilling rig, and   the DOC of the drill bit and torque exerted thereon are determined also using performance data of the drilling motor.   
     
     
         6 . The method of  claim 4 , wherein at least one of the parameters is measured downhole. 
     
     
         7 . The method of  claim 4 , wherein:
 the drilling of the hypothetical wellbore is simulated before drilling the wellbore, and   the strength of the geological formation is determined while drilling the wellbore.   
     
     
         8 . The method of  claim 1 , further comprising:
 further simulating drilling of the hypothetical wellbore using the hypothetical drill bit and determining a second function that provides weight on bit (WOB) of the simulated drilling from the DOC of the hypothetical drill bit and the torque exerted on the hypothetical drill bit;   determining weight on bit (WOB) using the second function and the determined DOC and the torque.   
     
     
         9 . The method of  claim 8 , further comprising planning a centralizer program of a downhole tubular using the determined WOB. 
     
     
         10 . The method of  claim 1 , wherein the drill bit is a PDC drill bit. 
     
     
         11 . A method for monitoring a drilling operation, comprising:
 providing a drill bit for drilling a wellbore into a geological formation using a drilling motor for rotating the drill bit;   determining depth of cut (DOC) of the drill bit and torque exerted on the drill bit by the drilling motor using parameters measured while drilling the wellbore;   simulating drilling of a hypothetical wellbore using a hypothetical drill bit similar or identical to the drill bit and determining a function that provides weight on bit (WOB) of the simulated drilling from the DOC of the hypothetical drill bit and the torque exerted on the hypothetical drill bit; and   determining WOB using the function and the determined DOC and the torque.   
     
     
         12 . The method of  claim 11 , further comprising:
 drilling the wellbore into the geological formation using the drill bit and the drilling motor; and   measuring the parameters while drilling the wellbore.   
     
     
         13 . The method of  claim 12 , wherein:
 drilling the wellbore also uses a drilling rig,   the parameters are measured at the drilling rig, and   the DOC of the drill bit and torque exerted thereon are determined also using performance data of the drilling motor.   
     
     
         14 . The method of  claim 12 , wherein:
 the drilling of the hypothetical wellbore is simulated before drilling the wellbore, and   the WOB is determined while drilling the wellbore.   
     
     
         15 . The method of  claim 11 , further comprising planning a centralizer program of a downhole tubular using the determined WOB.