Drill string torsional damping

Abstract

Vibrations in a drill string are damped with a sleeve that circumscribes and is rotatable about a portion of the drill string. Ribs project radially outward from an outer surface of the sleeve and into sidewalls of the wellbore to rotationally couple the sleeve and wellbore. A coupling device restricts free rotation of the sleeve about the drill string, and which is selectively engaged to counteract vibrational forces in the drill string. The coupling device can include a clutch-like device to introduce friction between the drill string and the sleeve, that is powered hydraulically or electrically. Activating the coupling device is based on a timer or in response to vibration sensed in the drill string.

What is claimed is: 
     
         1 . A system for damping oscillations in a drill string for use in a wellbore comprising:
 a pipe string;   and   a damping system comprising,
 a sleeve selectively rotatable around a portion of the pipe string and selectively engaged to a sidewall of the wellbore, and 
 a coupling unit configured to vary a coupling strength between the pipe string and the sleeve. 
   
     
     
         2 . The system of  claim 1 , wherein the coupling unit comprises one or more magnets and an electrical conduit, and the variation of the coupling strength is caused by varying an electrical current through the electrical conduit. 
     
     
         3 . The system of  claim 1 , further comprising one or more ribs on an outer surface of the sleeve that project towards the sidewall of the wellbore. 
     
     
         4 . The system of  claim 1 , wherein the damping system comprises a sensor for sensing a vibration parameter indicative of a vibration of the system in the wellbore and wherein the coupling unit varies the coupling strength in response to the sensed vibration parameter. 
     
     
         5 . The system of  claim 4 , further comprising a controller in communication with the sensor, the controller configured to initiate the coupling unit to vary the coupling strength based on the sensed vibration parameter. 
     
     
         6 . The system of  claim 4 , wherein the controller is configured to split the sensed vibration parameter in a first and second vibration portion having a frequency from a first and second frequency range, respectively. 
     
     
         7 . The system of  claim 1 , wherein the coupling unit comprises a coupling selected from the group consisting of a brake type coupling and a magnetic coupling. 
     
     
         8 . The system of  claim 1 , wherein the coupling unit comprises a magnetorheological fluid, wherein the coupling strength is varied by energizing the magnetorheological fluid. 
     
     
         9 . The system of  claim 6 , wherein at least one of the first and second frequency range is a discrete frequency value. 
     
     
         10 . The system of  claim 9 , wherein at least one of the first and second frequency range is a static frequency component. 
     
     
         11 . A method for damping oscillations in a drill string operated in a wellbore, the method comprising:
 lowering at least a portion of a pipe string into the wellbore, the pipe string comprising a damping system including a sleeve and a coupling unit;   engaging the sleeve to a sidewall of the wellbore;   varying, by the coupling unit, a coupling strength between the pipe string and the sleeve.   
     
     
         12 . The method of  claim 11 , wherein the coupling unit comprises one or more magnets and an electrical conduit, and the variation of the coupling strength is caused by varying an electrical current through the electrical conduit. 
     
     
         13 . The method of  claim 11 , further comprising projecting one or more ribs on an outer surface of the sleeve towards the sidewall of the wellbore. 
     
     
         14 . The method of  claim 11 , further comprising sensing, with a sensor in the damping system, a vibration parameter indicative of a vibration of the drill string in the wellbore and varying the coupling strength in response to the sensed vibration parameter. 
     
     
         15 . The method of  claim 14 , wherein the variation of the coupling strength by the coupling unit is initiated by a controller in communication with the sensor based on the sensed vibration parameter. 
     
     
         16 . The method of  claim 14 , further comprising splitting, by the controller, the sensed vibration parameter and a first and second vibration portion having a frequency from a first and second frequency range, respectively. 
     
     
         17 . The method of  claim 11 , wherein the coupling unit is varying the coupling strength by at least one of a hydraulic coupling, a magnetic coupling, or an electromagnetic coupling. 
     
     
         18 . The method of  claim 11 , wherein the coupling unit comprises a magnetorheological fluid, and wherein the variation of the coupling strength comprises energizing the magnetorheological fluid. 
     
     
         19 . The method of  claim 16 , wherein at least one of the first and second frequency range is a discrete frequency value. 
     
     
         20 . The method of  claim 19 , wherein at least one of the first and second frequency range is a static frequency component.