Mitigating drill string hfto

Abstract

Wellbore operations include rotating a drill string in a wellbore. The drill string includes a rotary steerable system having at least three pads configured to contact the wellbore wall to steer a direction of drilling. The pads are simultaneously actuated while rotating the drill string to mitigate high frequency torsional oscillations.

We claim: 
     
         1 . A wellbore operation comprises:
 rotating a drill string in a wellbore, the drill string including a rotary steerable system having at least three pads configured to contact the wellbore wall to steer a direction of drilling;   measuring a high frequency torsional oscillation (HFTO) amplitude while rotating;   comparing the measured HFTO amplitude with an HFTO threshold; and   simultaneously actuating the at least three pads to mitigate HFTO oscillations when the measured HFTO amplitude exceeds the HFTO threshold.   
     
     
         2 . The wellbore operation of  claim 1 , wherein the measuring, the comparing, and the simultaneously actuating is automatically implemented using a processor deployed in the rotary steerable system. 
     
     
         3 . The wellbore operation of  claim 1 , wherein the measuring further comprises measuring at least one of a collar rotation speed, a collar tangential acceleration, a bit tangential acceleration, and a bit torque. 
     
     
         4 . The wellbore operation of  claim 1 , wherein:
 the measuring further comprises measuring an HFTO frequency; and   the simultaneously actuating comprises simultaneously actuating the at least three pads to mitigate HFTO oscillations when the measured HFTO amplitude exceeds the HFTO threshold and the measured HFTO frequency is within a predetermined HFTO frequency band.   
     
     
         5 . The wellbore operation of  claim 1 , wherein the simultaneously actuating comprises simultaneously actuating the at least three pads for a period of time that is at least 1.5 times a fundamental stick slip period. 
     
     
         6 . The wellbore operation of  claim 1 , wherein the simultaneously actuating reduces a rotation rate of the drill string while said rotating by less than 10 percent. 
     
     
         7 . The wellbore operation of  claim 1 , wherein the simultaneously actuating comprises simultaneously actuating the at least three pads using independently controlled electronic valves in the rotary steerable system. 
     
     
         8 . The wellbore operation of  claim 1 , wherein the simultaneously actuating comprises sequentially actuating the at least three pads at a time interval of less than about  0 . 1  seconds. 
     
     
         9 . The wellbore operation of  claim 1 , wherein:
 the rotary steerable system comprises a roll stabilized control unit; and   the simultaneously actuating comprises rotating the roll stabilized control unit in a direction opposite of a direction of the drill string rotation to achieve a differential rotation rate between a rotation rate of the drill string and a rotation rate of the roll stabilized control unit that exceeds 400 rpm.   
     
     
         10 . A wellbore operation comprises:
 rotating a drill string in a wellbore, the drill string including a rotary steerable system having at least three pads configured to contact the wellbore wall to steer a direction of drilling;   determining operational conditions or times during the wellbore operation at which the drill string is susceptible to high frequency torsional oscillations (HFTO); and   simultaneously actuating the at least three pads to mitigate HFTO oscillations at the determined operational conditions or times when the drill string is susceptible to HFTO.   
     
     
         11 . The wellbore operation of  claim 10 , wherein the operational conditions or times are automatically determined and the simultaneously actuating is automatically implemented using a processor deployed in the rotary steerable system. 
     
     
         12 . The wellbore operation of  claim 10 , wherein the determining further comprises at least one of (i) identifying a local region of the wellbore having a dogleg that exceeds a dogleg threshold, (ii) identifying a time when a rotation rate of the drill string is less than a rotation rate threshold, and (iii) identifying a time when a weight on bit of the drill string is greater than a weight on bit threshold. 
     
     
         13 . The wellbore operation of  claim 10 , wherein the simultaneously actuating comprises simultaneously actuating the at least three pads for a period of time that is at least 1.5 times a fundamental stick slip period. 
     
     
         14 . The wellbore operation of  claim 10 , wherein the simultaneously actuating reduces a rotational rate of the drill string while said rotating by less than 10 percent. 
     
     
         15 . The wellbore operation of  claim 10 , wherein the simultaneously actuating comprises simultaneously actuating the at least three pads using independently controlled electronic valves in the rotary steerable system. 
     
     
         16 . The wellbore operation of  claim 10 , wherein:
 the rotary steerable system comprises a roll stabilized control unit; and   the simultaneously actuating comprises rotating the roll stabilized control unit in a direction opposite of a direction of the drill string rotation to achieve a differential rotation rate between a rotation rate of the drill string and a rotation rate of the roll stabilized control unit that exceeds 400 rpm.   
     
     
         17 . A rotary steerable system comprising:
 a rotary steerable system body including at least three pads deployed therein and configured to contact a wellbore wall to steer a direction of drilling;   a control unit including a processor and at least one sensor configured to measure a high frequency torsional oscillation (HFTO) amplitude; and   wherein the processor is configured to cause the at least one sensor to measure the HFTO amplitude and simultaneously actuate the at least three pads to mitigate HFTO when the HFTO amplitude exceeds a corresponding threshold.   
     
     
         18 . The rotary steerable system of  claim 17 , wherein the at least three pads are simultaneously actuated using corresponding independently controlled electronic valves. 
     
     
         19 . The rotary steerable system of  claim 17 , wherein:
 the control unit is a roll stabilized control unit; and   the processor is configured to simultaneously actuate the at least three pads via rotating the roll stabilized control unit in a direction opposite of a direction of drill string rotation to achieve a differential rotation rate between a rotation rate of the drill string and a rotation rate of the roll stabilized control unit that exceeds 400 rpm.   
     
     
         20 . The rotary steerable system of  claim 19 , further comprising:
 a spider valve in fluid communication with the first, second, and third pads, the spider valve configured to sequentially connect and disconnect the first, second, and third pads from high pressure drilling fluid as the rotary steerable system body rotates with respect to the roll stabilized control unit to sequentially actuate the first, second, and third pads;   first, second, and third nonreturn valves deployed between the spider valve and corresponding ones of the first, second, and third pads; and   the high pressure drilling fluid in each of the first, second, and third pads is vented to a wellbore annulus via a corresponding flow restrictor.