US Patent 7588099 Horizontal drilling system with oscillation control

A system and method for controlling drill string frictional forces during horizontal drilling are provided. The system includes a top drive having a motor that transmits a torque to a drill string to rotate the drill string, and an automated controller operably connected to the top drive to send at least one command signal to the top drive to initiate the rotation of the drill string. The controller monitors torque feedback signals, indicating that a torque limit on the drill string is exceeded, and/or a turn feedback signals indicating that the drill string is stalled to control the direction of the torque applied to the drill string when either the torque limit is exceeded or the drill string stalls.