US Patent 9145768 Method for reducing stick-slip during wellbore drilling

A method for drilling a wellbore includes operating at least one motor coupled within a drill string to turn a drill bit at an end thereof. An automatic drill string rotation controller causes rotation of the drill string in a first direction until a measured parameter related to torque on the drill string reaches a first selected value. The automatic drill string rotation controller causes rotation of the drill string in a second direction until the measured parameter related to torque is reduced to a second selected value. The drill string is axially advanced to cause the drill bit to extend the wellbore.