Wear indication apparatus and method

Abstract

Apparatus and method for monitoring the wear of a downhole tool, and providing indication of the degree of wear to an operator at the well surface. A pressurized fluid path within the cutting element matrix can exhibit a pressure drop when wear of the matrix progresses into the fluid path, or rotating torque can exhibit a drop when wear of the matrix progresses to wear pads within the cutting element matrix. Other wear indicators can also be built into the cutting element matrix. Progression of wear down to the indicator can be directly measured at the well surface, or relayed to the surface via a downhole communication system.

1 . A system for monitoring wear of a downhole tool, comprising: 
 a working profile formed on a downhole tool, said working profile being adapted to perform work on a structure downhole in a well bore;    a wear indicator within said working profile, said wear indicator being initially protected from physical contact with said downhole structure by said working profile;    a sensor adapted to measure an operating parameter of said downhole tool;    where said wear indicator is adapted to alter the value of said operating parameter when wear of said working profile has progressed sufficiently to expose said wear indicator to contact with said downhole structure.    
   
   
       2 . The system recited in  claim 1 , wherein said downhole tool comprises a tool selected from the group including a mill, a rotary shoe, a cutter, and a drill bit.  
   
   
       3 . The system recited in  claim 1 , wherein said working profile comprises a matrix of cutting elements.  
   
   
       4 . The system recited in  claim 1 , wherein: 
 said wear indicator comprises a pressurized fluid path in said working profile;    said sensor comprises a pressure sensor measuring fluid pressure in said fluid path; and    said fluid path is adapted to cause a drop in said fluid pressure upon sufficient progression of wear of said working profile to open said fluid path.    
   
   
       5 . The system recited in  claim 1 , wherein: 
 said wear indicator comprises a wear resistant pad;    said sensor comprises a torque sensor measuring the torque required to rotate said downhole tool; and    said wear resistant pad is adapted to cause a drop in said torque upon sufficient progression of wear of said working profile to bring said downhole structure into contact with said wear resistant pad.    
   
   
       6 . The system recited in  claim 1 , wherein: 
 said wear indicator comprises a quantity of a discernible medium imbedded within said working profile;    said sensor is adapted to detect the presence of said discernible medium in fluid returning from the wellbore to the surface; and    said quantity of discernible medium is adapted to be released into said fluid upon sufficient progression of wear of said working profile to bring said downhole structure into contact with said quantity of discernible medium.    
   
   
       7 . The system recited in  claim 6 , wherein said discernible medium is selected from the group including a magnetic material, a chemical tracer, and a visibly contrasting material.  
   
   
       8 . The system recited in  claim 1 , further comprising an output device adapted to provide a signal of an alteration in said value of said operating parameter indicating said progression of wear.  
   
   
       9 . The system recited in  claim 8 , wherein said output device comprises an operator interface.  
   
   
       10 . The system recited in  claim 9 , wherein said operator interface comprises a fluid pressure gage.  
   
   
       11 . The system recited in  claim 9 , wherein said operator interface comprises a torque meter.  
   
   
       12 . The system recited in  claim 8 , wherein said output device comprises a control system interface adapted to provide an input signal into a control system.  
   
   
       13 . A method for monitoring wear of a downhole tool, comprising: 
 providing a wear indicator in a working profile of a downhole tool;    providing a sensor adapted to measure an operating parameter of said downhole tool;    operating said downhole tool to perform work downhole in a wellbore;    altering the value of said operating parameter with said wear indicator, when wear of said working profile has progressed sufficiently to expose said wear indicator to contact with a downhole structure; and    sensing said alteration in said value of said operating parameter with said sensor.    
   
   
       14 . The method recited in  claim 13 , further comprising: 
 providing a pressurized fluid path as said wear indicator and a pressure sensor as said sensor;    opening said fluid path when wear of said working profile has progressed sufficiently to expose said fluid path to contact with a downhole structure; and    sensing a drop in the pressure in said fluid path with said pressure sensor.    
   
   
       15 . The method recited in  claim 13 , further comprising: 
 providing a wear resistant pad as said wear indicator and a torque sensor as said sensor;    bearing weight with said wear resistant pad when wear of said working profile has progressed sufficiently to expose said wear resistant pad to contact with a downhole structure; and    sensing a drop in the torque required to rotate said downhole tool with said torque sensor.    
   
   
       16 . The method recited in  claim 13 , further comprising: 
 imbedding a quantity of discernible medium in said working profile;    releasing said quantity of discernible medium from said working profile when wear of said working profile has progressed sufficiently to expose said quantity of discernible medium to contact with a downhole structure; and    discerning the escape of said discernible medium from said working profile.