Autodriller Utilizing Intermediate ROP Setpoint

Abstract

Apparatus and methods for automatically controlling selected drilling operations. The apparatus may be a control system operable to control rate of penetration (ROP) by a drill bit of a drill string for drilling a wellbore. The control system may include a sensor operable to facilitate an ROP measurement indicative of a measured ROP and a controller comprising a processor and a memory storing computer program code. The controller may be operable to receive the ROP measurement, determine an intermediate ROP setpoint based on the ROP measurement, and determine an ROP command based on the intermediate ROP setpoint, wherein the ROP command is to be received by a drawworks and is indicative of an intended ROP.

What is claimed is: 
     
         1 . An apparatus comprising:
 a system operable to control rate of penetration (ROP) by a drill bit of a drill string for drilling a wellbore, wherein the system comprises:
 a sensor operable to facilitate an ROP measurement indicative of a measured ROP; and 
 a controller comprising a processor and a memory storing computer program code, wherein the controller is operable to:
 receive the ROP measurement; 
 determine an intermediate ROP setpoint based on the ROP measurement; and 
 determine an ROP command based on the intermediate ROP setpoint, wherein the ROP command is to be received by a drawworks and is indicative of an intended ROP. 
 
   
     
     
         2 . The apparatus of  claim 1  wherein the controller is operable to determine the intermediate ROP setpoint by adding a step value to the ROP measurement. 
     
     
         3 . The apparatus of  claim 2  wherein the controller is further operable to receive an ROP upper limit setpoint defined by rig personnel, and wherein the step value comprises a percentage of the ROP upper limit setpoint. 
     
     
         4 . The apparatus of  claim 1  wherein the controller is further operable to receive an ROP upper limit setpoint defined by rig personnel, and wherein the controller is operable to determine the intermediate ROP setpoint by:
 limiting the ROP measurement to the ROP upper limit setpoint; and 
 adding a step value to the limited ROP measurement. 
 
     
     
         5 . The apparatus of  claim 1  wherein the controller is further operable to receive an ROP upper limit setpoint defined by rig personnel, and wherein the controller is operable to determine the intermediate ROP setpoint by:
 adding a step value to the ROP measurement to determine a first intermediate ROP setpoint; 
 limiting the first intermediate ROP setpoint between an acceleration limit and a deceleration limit to determine a second intermediate ROP setpoint; and 
 limiting the second intermediate ROP setpoint with the ROP upper limit setpoint. 
 
     
     
         6 . The apparatus of  claim 1  wherein the controller is an ROP controller operable to:
 receive a normalized weight on bit (WOB) output from a WOB controller; 
 receive a normalized torque on bit (TOB) output from a drilling torque controller; 
 receive a normalized differential pressure (DeltaP) output from a DeltaP controller; and 
 determine the ROP command based further on one or more of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output. 
 
     
     
         7 . The apparatus of  claim 1  wherein the controller is an ROP controller operable to:
 receive a normalized weight on bit (WOB) output from a WOB controller; 
 receive a normalized torque on bit (TOB) output from a drilling torque controller; 
 receive a normalized differential pressure (DeltaP) output from a DeltaP controller; 
 find a smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output; and 
 determine the ROP command by taking a product of the intermediate ROP setpoint and the smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output. 
 
     
     
         8 . A method comprising:
 commencing operation of a control system for controlling rate of penetration (ROP) by a drill bit of a drill string for drilling a wellbore, wherein the operating control system:
 receives an ROP measurement; 
 determines an intermediate ROP setpoint based on the ROP measurement; and 
 determines an ROP command based on the intermediate ROP setpoint, wherein the ROP command is to be received by a drawworks and is indicative of an intended ROP. 
   
     
     
         9 . The method of  claim 8  wherein determining the intermediate ROP setpoint comprises adding a step value to the ROP measurement. 
     
     
         10 . The method of  claim 9  wherein the operating control system also receives an ROP upper limit setpoint defined by rig personnel, and wherein the step value comprises a percentage of the ROP upper limit setpoint. 
     
     
         11 . The method of  claim 8  wherein the operating control system also receives an ROP upper limit setpoint defined by rig personnel, and wherein determining the intermediate ROP setpoint comprises:
 limiting the ROP measurement to the ROP upper limit setpoint; and 
 adding a step value to the limited ROP measurement. 
 
     
     
         12 . The method of  claim 8  wherein determining the intermediate ROP setpoint comprises:
 adding a step value to the ROP measurement to increase the ROP measurement; and 
 limiting the increased ROP measurement between an acceleration limit and a deceleration limit. 
 
     
     
         13 . The method of  claim 8  wherein the operating control system also:
 receives a normalized weight on bit (WOB) output from a WOB controller; 
 receives a normalized torque on bit (TOB) output from a drilling torque controller; 
 receives a normalized differential pressure (DeltaP) output from a DeltaP controller; and 
 determines the ROP command further based on one or more of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output. 
 
     
     
         14 . The method of  claim 8  wherein the operating control system also:
 receives a normalized weight on bit (WOB) output from a WOB controller; 
 receives a normalized torque on bit (TOB) output from a drilling torque controller; 
 receives a normalized differential pressure (DeltaP) output from a DeltaP controller; 
 finds a smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output; and 
 determines the ROP command by taking a product of the intermediate ROP setpoint and the smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output. 
 
     
     
         15 . A computer program product comprising:
 a non-transitory, computer-readable medium comprising computer instructions executable by a processor of a control system communicatively connected with a drawworks for raising and lowering a drill string, wherein the computer instructions, when executed by the processor, cause the control system to:
 receive a rate of penetration (ROP) measurement; 
 determine an intermediate ROP setpoint based on the ROP measurement; and 
 determine an ROP command based on the intermediate ROP setpoint, wherein the ROP command is to be received by a drawworks and is indicative of an intended ROP. 
   
     
     
         16 . The computer program product of  claim 15  wherein execution of the computer instructions also causes the control system to determine the intermediate ROP setpoint by adding a step value to the ROP measurement. 
     
     
         17 . The computer program product of  claim 16  wherein execution of the computer instructions also causes the control system to receive an ROP upper limit setpoint defined by rig personnel, and wherein the step value comprises a percentage of the ROP upper limit setpoint. 
     
     
         18 . The computer program product of  claim 15  wherein execution of the computer instructions also causes the control system to:
 receive an ROP upper limit setpoint defined by rig personnel; and 
 determine the intermediate ROP setpoint by:
 limiting the ROP measurement to the ROP upper limit setpoint; and 
 adding a step value to the limited ROP measurement. 
 
 
     
     
         19 . The computer program product of  claim 15  wherein execution of the computer instructions also causes the control system to:
 receive a normalized weight on bit (WOB) output from a WOB controller; 
 receive a normalized torque on bit (TOB) output from a drilling torque controller; 
 receive a normalized differential pressure (DeltaP) output from a DeltaP controller; and 
 determine the ROP command further based on one or more of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output. 
 
     
     
         20 . The computer program product of  claim 15  wherein execution of the computer instructions also causes the control system to:
 receive a normalized weight on bit (WOB) output from a WOB controller; 
 receive a normalized torque on bit (TOB) output from a drilling torque controller; 
 receive a normalized differential pressure (DeltaP) output from a DeltaP controller; 
 find a smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output; and 
 determine the ROP command by taking a product of the intermediate ROP setpoint and the smallest one of the normalized WOB output, the normalized TOB output, and the normalized DeltaP output.