Automated zeroing for drilling operations

Abstract

A method for drilling a wellbore. The method comprising monitoring, by a control system, a drilling variable for a drill string in a borehole during drilling of the wellbore by a drilling rig. The method further comprising determining, by the control system, if a steady state condition for the drilling variable occurs. Responsive to determining that the steady state condition for the drilling variable has occurred, the method further comprising determining, by the control system, a zero reference value for the drilling variable, adjusting one or more drilling parameters using the zero reference value determined by the control system, drilling the wellbore in accordance with the one or more drilling parameters.

1 . A method for drilling a wellbore comprising:
 monitoring, by a control system, a drilling variable for a drill string during drilling of the wellbore by a drilling rig;   determining, by the control system and using a set of monitored drilling values of the drilling variable, a current value of the drilling variable, a mean value of the drilling variable, a standard deviation value of the drilling variable, and a statistical critical value of the drilling variable;   determining, by the control system, a steady state condition using the mean value, the current value, the standard deviation value, and the statistical critical value;   determining, by the control system, occurrence of the steady state condition for the drilling variable; and   responsive to determining that the steady state condition for the drilling variable has occurred:
 determining, by the control system, a zero reference value for the drilling variable; 
 adjusting one or more drilling parameters using the zero reference value determined by the control system; and 
 drilling the wellbore in accordance with the one or more adjusted drilling parameters. 
   
     
     
         2 . The method of  claim 1 , wherein the drilling variable is at least one of a hookload variable or a pressure variable. 
     
     
         3 . (canceled) 
     
     
         4 . The method of  claim 1 , wherein obtaining the steady state condition using the mean value further comprises:
 determining a difference between the mean value and the current value;   determining a product of the standard deviation value and the statistical critical value;   comparing the difference and the product;   responsive to the difference being greater than the product:
 indicating that the steady state condition for the drilling variable has not occurred; and 
   responsive to the difference being less than or equal to the product:
 indicating that the steady state condition for the drilling variable has occurred. 
   
     
     
         5 . The method of  claim 1 , wherein determining, by the control system, if the steady state condition for the drilling variable further comprises:
 using window-based computations and a student-t test.   
     
     
         6 . The method of  claim 5 , wherein the window-based computations further comprises:
 determining a time constant of the drilling variable;   determining a sampling time period of the drilling variable;   dividing the time constant by the sampling time period to obtain a division result; and   setting a window length of the window-based computations to, at least, three times the current value of the division result.   
     
     
         7 . The method of  claim 6 , further comprising:
 setting the window length of the window-based computations to, at most, five times the current value of the division result.   
     
     
         8 . The method of  claim 1 , wherein the one or more drilling parameters comprise at least one of weight on bit, rate of penetration, revolutions per minute, differential pressure, toolface, torque. 
     
     
         9 . The method of  claim 1 , wherein determining if the steady state condition for the drilling variable occurs is performed while a drill bit coupled to the drill string is off a bottom of the wellbore. 
     
     
         10 . The method of  claim 1 , further comprising:
 adding a stand of drill pipe to the drill string before determining that the steady state condition for the drilling variable has occurred.   
     
     
         11 . The method of  claim 1 , further comprising:
 adding a plurality of stands of drill pipe to the drill string before determining that the steady state condition for the drilling variable has occurred.   
     
     
         12 . A non-transitory computer-readable medium storing a plurality of instructions for drilling a wellbore executable by one or more processors that cause the one or more processors to perform operations comprising:
 monitoring a drilling variable for a drill string during drilling of the wellbore by a drilling rig;   determining, using a set of monitored values of the drilling variable, a current value of the drilling variable, a mean value of the drilling variable, a standard deviation value of the drilling variable, and a statistical critical value of the drilling variable;   determining a steady state condition using the mean value, the current value, the standard deviation value, and the statistical critical value;   determining occurrence of the steady state condition for the drilling variable; and   responsive to determining that the steady state condition for the drilling variable has occurred:
 determining a zero reference value for the drilling variable; and 
 adjusting one or more drilling parameters responsive to the zero reference value for drilling of the wellbore in accordance with the one or more adjusted drilling parameters. 
   
     
     
         13 . The non-transitory computer-readable medium of  claim 12 , wherein the drilling variable is at least one of a hookload variable or a pressure variable. 
     
     
         14 . (canceled) 
     
     
         15 . The non-transitory computer-readable medium of  claim 12 , wherein the statistical critical value is predetermined and obtained from a system monitoring the drilling variable. 
     
     
         16 . The non-transitory computer-readable medium of  claim 12 , wherein determining that the steady state condition for the drilling variable has occurred further comprises:
 using window-based computations and a student-t test.   
     
     
         17 . A control system for drilling a wellbore comprising:
 a processor;   a memory coupled to the processor, the memory comprising instructions for:
 monitoring, by the control system, a drilling variable for a drill string during drilling of the wellbore by a drilling rig; 
 determining, by the control system and using a set of monitored drilling values of the drilling variable, a current value of the drilling variable, a mean value of the drilling variable, a standard deviation value of the drilling variable, and a statistical critical value of the drilling variable; 
 determining, by the control system, a steady state condition using the mean value, the current value, the standard deviation value, and the statistical critical value 
 determining, by the control system, occurrence of the steady state condition for the drilling variable; and 
 responsive to determining that the steady state condition for the drilling variable has occurred:
 determining, by the control system, a zero reference value for the drilling variable; 
 adjusting one or more drilling parameters using the zero reference value determined by the control system; and 
 providing the one or more adjusted drilling parameters to one or more drilling rig control systems to drill the wellbore in accordance with the one or more adjusted drilling parameters. 
 
   
     
     
         18 . The system of  claim 17 , wherein the drilling variable is at least one of a hookload variable or a pressure variable. 
     
     
         19 . (canceled) 
     
     
         20 . The system of  claim 17 , wherein the statistical critical value is predetermined and obtained from the control system. 
     
     
         21 . The system of  claim 17 , wherein determining, by the control system, if the steady state condition for the drilling variable further comprises:
 using window-based computations and a student-t test.   
     
     
         22 . The system of  claim 17 , wherein determining that the steady state condition for the drilling variable has occurred is performed while a drill bit coupled to the drill string is off a bottom of the wellbore. 
     
     
         23 . The system of  claim 17 , further comprising:
 adding a stand of drill pipe to the drill string before determining that the steady state condition for the drilling variable has occurred.   
     
     
         24 . The system of  claim 17 , further comprising:
 adding a plurality of stands of drill pipe to the drill string before determining that the steady state condition for the drilling variable has occurred.