Estimation of rock abrasiveness and rock strength using bit response data

Abstract

Some implementations include a method which comprises determining a drilling efficiency of a drill bit at a first depth in a wellbore formed in a subsurface formation based, at least in part, on a bit wear level of the drill bit, determining a cutting force mechanical specific energy of the drill bit at the first depth, and determining a rock strength of the subsurface formation at the first depth based on the drilling efficiency and the cutting force mechanical specific energy of the drill bit.

1 . A method comprising:
 determining a drilling efficiency of a drill bit at a first depth in a wellbore formed in a subsurface formation based, at least in part, on a bit wear level of the drill bit;   determining a cutting force mechanical specific energy of the drill bit at the first depth; and   determining a rock strength of the subsurface formation at the first depth based on the drilling efficiency and the cutting force mechanical specific energy of the drill bit.   
     
     
         2 . The method of  claim 1 , further comprising:
 determining an average rock abrasiveness factor based, at least in part, on a cutter wear volume of a plurality of primary cutters disposed along a face of the drill bit.   
     
     
         3 . The method of  claim 2 , further comprising:
 determining, via a bit-rock interaction tool, a cutter dull severity for each primary cutter of the plurality of primary cutters;   determining a cutter wear depth of the plurality of primary cutters based on the cutter dull severity; and   determining the cutter wear volume of the plurality of primary cutters based on the determined cutter wear depth.   
     
     
         4 . The method of  claim 3 , further comprising:
 determining a weight on bit (WOB) and a torque on bit (TOB) on the drill bit along a drilling depth of the wellbore based, at least in part, on a given rate of penetration of the drill bit, a given quantity of revolutions per minute of the drill bit;   determining a mechanical specific energy of the drill bit based on the WOB and TOB of the drill bit along the drilling depth; and   determining a plurality of values of the drilling efficiency of the drill bit along the drilling depth of the wellbore.   
     
     
         5 . The method of  claim 1 , further comprising:
 determining an input energy to a primary cutter of the drill bit at the first depth along a drilling depth of the wellbore;   determining a required energy for the primary cutter of the drill bit to wear to a bit wear level; and   determining a bit wear level at the first depth along the drilling depth of the wellbore.   
     
     
         6 . The method of  claim 1 , wherein determining the cutting force mechanical specific energy of the drill bit at the first depth comprises determining the cutting force mechanical specific energy based on a cutting force weight on bit and a cutting force torque on bit. 
     
     
         7 . The method of  claim 1 , wherein the rock strength is a confined compressive strength of the subsurface formation at the first depth. 
     
     
         8 . One or more non-transitory, machine-readable media having instructions stored thereon that are executable by a processor, the instructions comprising:
 instructions to determine a drilling efficiency of a drill bit at a first depth in a wellbore formed in a subsurface formation based, at least in part, on a bit wear level of the drill bit;   instructions to determine a cutting force mechanical specific energy of the drill bit at the first depth; and   instructions to determine a rock strength of the subsurface formation at the first depth based on the drilling efficiency and the cutting force mechanical specific energy of the drill bit.   
     
     
         9 . The one or more non-transitory, machine-readable media of  claim 8 , further comprising:
 instructions to determine an average rock abrasiveness factor based, at least in part, on a cutter wear volume of a plurality of primary cutters disposed along a face of the drill bit.   
     
     
         10 . The one or more non-transitory, machine-readable media of  claim 9 , further comprising:
 instructions to determine, via a bit-rock interaction tool, a cutter dull severity for each primary cutter of the plurality of primary cutters;   instructions to determine a cutter wear depth of the plurality of primary cutters based on the cutter dull severity; and   instructions to determine the cutter wear volume of the plurality of primary cutters based on the determined cutter wear depth.   
     
     
         11 . The one or more non-transitory, machine-readable media of  claim 10 , further comprising:
 instructions to determine a weight on bit (WOB) and a torque on bit (TOB) on the drill bit along a drilling depth of the wellbore based, at least in part, on a given rate of penetration of the drill bit, a given quantity of revolutions per minute of the drill bit, and a known rock strength;   instructions to determine a mechanical specific energy of the drill bit based on the WOB and TOB of the drill bit along the drilling depth; and   instructions to determine a plurality of values of the drilling efficiency of the drill bit along the drilling depth of the wellbore.   
     
     
         12 . The one or more non-transitory, machine-readable media of  claim 8 , further comprising:
 instructions to determine an input energy to a primary cutter of the drill bit at the first depth along a drilling depth of the wellbore;   instructions to determine a required energy for the primary cutter of the drill bit to wear to a bit wear level; and   instructions to determine a bit wear level at the first depth along the drilling depth of the wellbore.   
     
     
         13 . The one or more non-transitory, machine-readable media of  claim 8 , wherein the instructions to determine the cutting force mechanical specific energy of the drill bit at the first depth comprise instructions to determine the cutting force mechanical specific energy based on a cutting force weight on bit and a cutting force torque on bit. 
     
     
         14 . An apparatus comprising:
 a processor; and   one or more machine-readable media having instructions stored thereon that are executable by the processor, the instructions comprising:
 instructions to determine a drilling efficiency of a drill bit at a first depth in a wellbore formed in a subsurface formation based, at least in part, on a bit wear level of the drill bit; 
 instructions to determine a cutting force mechanical specific energy of the drill bit at the first depth; and 
 instructions to determine a rock strength of the subsurface formation at the first depth based on the drilling efficiency and the cutting force mechanical specific energy of the drill bit. 
   
     
     
         15 . The apparatus of  claim 14 , further comprising:
 instructions to determine an average rock abrasiveness factor based, at least in part, on a cutter wear volume of a plurality of primary cutters disposed along a face of the drill bit.   
     
     
         16 . The apparatus of  claim 15 , further comprising:
 instructions to determine, via a bit-rock interaction tool, a cutter dull severity for each primary cutter of the plurality of primary cutters;   instructions to determine a cutter wear depth of the plurality of primary cutters based on the cutter dull severity; and   instructions to determine the cutter wear volume of the plurality of primary cutters based on the determined cutter wear depth.   
     
     
         17 . The apparatus of  claim 16 , further comprising:
 instructions to determine a weight on bit (WOB) and a torque on bit (TOB) on the drill bit along a drilling depth of the wellbore based, at least in part, on a given rate of penetration of the drill bit, a given quantity of revolutions per minute of the drill bit, and a known rock strength;   instructions to determine a mechanical specific energy of the drill bit based on the WOB and TOB of the drill bit along the drilling depth; and   instructions to determine a plurality of values of the drilling efficiency of the drill bit along the drilling depth of the wellbore.   
     
     
         18 . The apparatus of  claim 14 , further comprising:
 instructions to determine an input energy to a primary cutter of the drill bit at the first depth along a drilling depth of the wellbore;   instructions to determine a required energy for the primary cutter of the drill bit to wear to a bit wear level; and   instructions to determine a bit wear level at the first depth along the drilling depth of the wellbore.   
     
     
         19 . The apparatus of  claim 14 , wherein the instructions to determine the cutting force mechanical specific energy of the drill bit at the first depth comprise instructions to determine the cutting force mechanical specific energy based on a cutting force weight on bit and a cutting force torque on bit. 
     
     
         20 . The apparatus of  claim 14 , wherein the rock strength is a confined compressive strength of the subsurface formation at the first depth.