Systems and methods for determining wear of downhole tools

Abstract

A method of detecting wear of a downhole tool implemented in a subject wellbore includes receiving offset wellbore data for one or more offset wellbores and, based on the offset wellbore data, determining an expected downhole tool index for the downhole tool at one or more measurement depths including an active measurement depth of the subject wellbore. The method further includes receiving subject wellbore data and, based on the subject wellbore data, determining a subject downhole tool index in real time for the downhole tool at the active measurement depth. The method further includes determining the wear of the downhole tool based on comparing the subject downhole tool index to the expected downhole tool index at the active measurement depth in real time.

What is claimed is: 
     
         1 . A method of detecting wear of a downhole tool implemented in a subject wellbore, comprising:
 receiving offset wellbore data for one or more offset wellbores;   based on the offset wellbore data, determining an expected formation stiffness for the downhole tool at a range of measurement depths of the subject wellbore;   receiving subject wellbore data; and   based on the subject wellbore data, determining a subject formation stiffness for an active measurement depth of the subject wellbore; and   in real time:
 determining, a formation stiffness ratio of the subject formation stiffness to the expected formation stiffness for the active measurement depth; and 
 classifying a wear state of the downhole tool based on one or more predetermined thresholds for the formation stiffness ratio. 
   
     
     
         2 . The method of  claim 1 , wherein the offset wellbore data indicates a rate of penetration (ROP), a weight on bit (WOB), and a rotational speed (RPM) for a plurality of runs of respective downhole tools in one or more offset wellbores, and wherein, for each of the plurality of runs, the offset wellbore data indicates a wear state for the respective downhole tools as determined by inspection of the respective downhole tools when removed from an associated offset wellbore. 
     
     
         3 . The method of  claim 2 , wherein the wear state of the respective downhole tools is based on an International Association of Drilling Contractors (IADC) classification for drill bit dull grade. 
     
     
         4 . The method of  claim 3 , further comprising filtering the subject wellbore data to remove offset wellbore data for runs associated with a downhole tool that was severely dull or damaged. 
     
     
         5 . The method of  claim 4 , wherein filtering includes removing wellbore data for runs associated with a downhole tool exhibiting one or more of an inner grade of 4 or higher, an outer grade of 4 or higher, a ring-out characteristic, or a core-out characteristic. 
     
     
         6 . The method of  claim 3 , wherein classifying the wear state of the downhole tool includes classifying the wear state based on the IADC classification. 
     
     
         7 . The method of  claim 1 , wherein receiving the subject wellbore data includes measuring an ROP, a WOB, and an RPM for the subject wellbore at a surface of the subject wellbore. 
     
     
         8 . The method of  claim 1 , further comprising:
 receiving formation data indicating one or more formation boundaries of a formation in which the subject wellbore and the one or more offset wellbores are positioned;   aligning the subject wellbore data and offset wellbore data based on at least one formation boundary of the one or more formation boundaries; and   determining the formation stiffness ratio of the subject formation stiffness to the expected formation stiffness for an aligned active measurement depth of the subject wellbore and the one or more offset wellbores.   
     
     
         9 . The method of  claim 8 , wherein aligning the subject wellbore data and the offset wellbore data includes misaligning one or more measurement depths of the subject wellbore data and of the offset wellbore data. 
     
     
         10 . The method of  claim 8 , wherein the formation data indicates a top formation boundary and a bottom formation boundary for the formation, and wherein aligning includes aligning the offset wellbore data and the subject wellbore data with the top formation boundary and the bottom formation boundary. 
     
     
         11 . The method of  claim 10 , wherein the formation data indicates a variation in thickness of the formation between the subject wellbore and the one or more offset wellbores, and aligning further includes one or more of compressing or stretching the subject wellbore data or the offset wellbore data based on the variation in thickness of the formation. 
     
     
         12 . The method of  claim 1 , further comprising, determining that the classified wear state of the downhole tool exceeds a wear threshold and in response completing at least one of removing the downhole tool or replacing the downhole tool. 
     
     
         13 . A system, comprising:
 at least one processor;   memory in electronic communication with the at least one processor; and   instructions store in the memory, the instructions being executable by the at least one processor to:   receive offset wellbore data for one or more offset wellbores;   based on the offset wellbore data, determine an expected formation stiffness for a downhole tool implemented within a subject wellbore at a range of measurement depths of the subject wellbore;   receive subject wellbore data;   based on the subject wellbore data, determine a subject formation stiffness for an active measurement depth of the subject wellbore; and   in real time:
 determine, a formation stiffness ratio of the subject formation stiffness to the expected formation stiffness for the active measurement depth; and 
 classify a wear state of the downhole tool based on one or more predetermined thresholds for the formation stiffness ratio. 
   
     
     
         14 . The system of  claim 13 , further comprising filtering the subject wellbore data to remove offset wellbore data for runs where an associated downhole tool was dull or damaged. 
     
     
         15 . The system of  claim 14 , wherein filtering includes removing wellbore data for runs where the associated downhole tool exhibits one or more of an inner grade of 2 or higher, an outer grade of 2 or higher, a ring-out characteristic, or a core-out characteristic according to an International Association of Drilling Contractors (IADC) drill bit dull grading. 
     
     
         16 . The system of  claim 13 , further comprising, determining that the classified wear state of the downhole tool exceeds a wear threshold and in response, causing at least one of: the downhole tool to be removed, or the downhole tool to be replaced. 
     
     
         17 . A computer-readable storage medium including instructions that, when executed by at least one processor, cause the at least one processor to:
 receive offset wellbore data for one or more offset wellbores;   based on the offset wellbore data, determine an expected formation stiffness for a downhole tool implemented within a subject wellbore at a range of measurement depths of the subject wellbore;   receive subject wellbore data;   based on the subject wellbore data, determine a subject formation stiffness for an active measurement depth of the subject wellbore; and   in real time:
 determine, a formation stiffness ratio of the subject formation stiffness to the expected formation stiffness for the active measurement depth; and 
 classify a wear state of the downhole tool based on one or more predetermined thresholds for the formation stiffness ratio. 
   
     
     
         18 . The computer-readable storage medium of  claim 17 , further comprising:
 receiving formation data indicating a top formation boundary and a bottom formation boundary of a formation in which the subject wellbore and the one or more offset wellbores are positioned;   aligning the subject wellbore data and offset wellbore data based on the top formation boundary and the bottom formation boundary; and   determining the formation stiffness ratio of the subject formation stiffness to the expected formation stiffness for an aligned active measurement depth of the subject wellbore and the one or more offset wellbores.   
     
     
         19 . The computer-readable storage medium of  claim 18 , wherein the formation data indicates a variation in thickness of the formation between the subject wellbore and the one or more offset wellbores, and aligning further includes one or more of compressing or stretching the subject wellbore data or the offset wellbore data based on the variation in thickness of the formation. 
     
     
         20 . The computer-readable storage medium of  claim 19 , further comprising determining that the classified wear state of the downhole tool exceeds a wear threshold and in response, causing at least one of: the downhole tool to be removed, or the downhole tool to be replaced.