Estimation and calibration of downhole buckling conditions

Abstract

A method for estimating an axial force transfer efficiency of a drillstring in a borehole includes lifting the drillstring so that the drill bit is off the bottom of the borehole, measuring a hook load, slacking off a first reference amount of the hook load, determining a first weight on bit at the bottom of the drillstring and determining the axial force transfer efficiency based, at least in part, on the measured hook load, the first weight on bit, and the first reference amount of hook load.

What is claimed is: 
     
       1. A method for estimating an axial force transfer efficiency of a drillstring in a borehole, the drillstring comprising a drill bit, the method comprising:
 lifting the drillstring so that the drill bit is off the bottom of the borehole; 
 measuring a hook load; 
 slacking off a first reference amount of the hook load; 
 determining a first weight on bit at the bottom of the drillstring; and 
 determining the axial force transfer efficiency based, at least in part, on the measured hook load, the first weight on bit, and the first reference amount of hook load. 
 
     
     
       2. The method of  claim 1 , further comprising:
 slacking off a second reference amount of the hook load; 
 determining a second weight on bit at the bottom of the drillstring; and 
 wherein determining the axial force transfer efficiency is further based, at least in part, on the second weight on bit and the second reference amount of hook load. 
 
     
     
       3. The method of  claim 2 , further comprising:
 slacking off one or more subsequent reference amounts of the hook load; 
 determining one or more corresponding subsequent weights on bit at the bottom of the drillstring; and 
 wherein determining the axial force transfer efficiency is further based, at least in part, on the one or more corresponding subsequent reference amounts of hook load and the one or more corresponding subsequent weights on bit. 
 
     
     
       4. The method of  claim 3 , wherein the first reference amount of hook load, the second reference amount of hook load, and the one or more subsequent reference amounts of hook load are between 5 and 10 kips. 
     
     
       5. The method of  claim 2 , wherein slacking off a first reference amount of the hook load and slacking off the second reference amount of the hook load are performed while the drillstring is rotating. 
     
     
       6. The method of  claim 5 , further comprising:
 altering the rotation rate of the drillstring between slacking off the first reference amount of the hook load and slacking off the second reference amount of the hook load. 
 
     
     
       7. The method of  claim 2 , wherein slacking off the first reference amount of the hook load and slacking off the second reference amount of the hook load are performed while the drillstring is not rotating. 
     
     
       8. The method of  claim 1 , wherein determining an axial force transfer efficiency is further based, at least in part, on one or more of: one or more time-depth measurements from the drillstring; one or more local magnetic parameters; a rotation rate of the drillstring; a torque on bit of the drillstring; one or more bending moments of the drillstring; a mud weight; and one more borehole diameters. 
     
     
       9. The method of  claim 1 , further comprising:
 performing a drilling operation in a subterranean formation; and 
 altering a rate of penetration of a wellbore in the subterranean formation based, at least in part, on the determined axial force transfer efficiency of the drillstring. 
 
     
     
       10. A system for controlling one or more drilling operations, comprising:
 at least one processor; and 
 a memory including non-transitory executable instructions for estimating an axial force transfer efficiency of a drillstring, wherein the executable instructions cause at least one processor to: 
 lift the drillstring so that the drill bit is off the bottom of a borehole; 
 measure a hook load; 
 slack off a first reference amount of the hook load; 
 determine a first weight on bit at the bottom of the drillstring; and 
 determine an axial force transfer efficiency based, at least in part, on the measured hook load, the first weight on bit, and the first reference amount of hook load. 
 
     
     
       11. The system of  claim 10 , wherein the executable instructions further cause the at least one processor to:
 slack off a second reference amount of the hook load; 
 determine a second weight on bit at the bottom of the drillstring; and 
 determine the axial force transfer efficiency based, at least in part, on the measured hook load, the first weight on bit, the second weight on bit, the first reference amount of hook load, and the second reference amount of hook load. 
 
     
     
       12. The system of  claim 11 , wherein the first reference amount and the second reference amount are between 5 and 10 kips. 
     
     
       13. The system of  claim 11 , wherein slacking off the first reference amount of the hook load and slacking off the second reference amount of the hook load are performed while the drillstring is rotating. 
     
     
       14. The system of  claim 11 , wherein slacking off the first reference amount of the hook load and slacking off the second reference amount of the hook load are performed while the drillstring is not rotating. 
     
     
       15. The system of  claim 10 , wherein the executable instructions further cause the at least one processor to:
 alter a rotation rate of the drillstring between slacking off the first reference amount of the hook load and slacking off the second reference amount of the hook load. 
 
     
     
       16. The system of  claim 10 , wherein the executable instruction further cause the one processor to determine the axial force transfer efficiency further based, at least in part, on one or more of: one or more time-depth information; one or more local magnetic parameters; a rotation rate of the drillstring; a torque on bit of the drillstring; one or more bending moments of the drillstring; a mud weight; and one more borehole diameters. 
     
     
       17. The system of  claim 10 , wherein the executable instructions further cause the at least one processor to:
 control a drilling operation in a subterranean formation; and 
 alter the rate of penetration of a wellbore in the subterranean formation based, at least in part, on the determined axial force transfer efficiency of the drillstring. 
 
     
     
       18. A system for controlling one or more drilling operations, comprising:
 a drillstring including a drill bit; 
 at least one processor; and 
 a memory including non-transitory executable instructions for estimating an axial force transfer efficiency of a drillstring, wherein the executable instructions cause at least one processor to: 
 alter the hook load by a first reference amount; 
 measure a first weight on bit at the bottom of the drillstring; 
 alter the hook load by a second reference amount; 
 measure a second weight on bit at the bottom of the drillstring; and 
 determine an axial force transfer efficiency based, at least in part, on the first and second reference amounts of hook load, the first weight on bit, and the second weight on bit. 
 
     
     
       19. The system of  claim 18 , wherein:
 the executable instructions that cause at least one processor to alter the hook load by a first reference amount cause the at least one processor to:
 increase hook load by the first reference amount; and 
 
 the executable instructions that cause at least one processor to alter the hook load by a second reference amount cause the at least one processor to:
 increase hook load by the second reference amount. 
 
 
     
     
       20. The system of  claim 18 , wherein the first reference amount and the second reference amount are between 5 and 10 kips.