Reduction of the frictional coefficient in a borehole by the use of vibration

A method of rotary drilling a wellbore in extended reach drilling into the earth in a manner to mitigate sticking of a drill string having a drill bit at the lower end thereof, comprising drilling said wellbore by rotating a drill string comprised of sections of drill pipe connected together, and mitigating the tendency of the drill string to stick in the hole by continuously vibrating the drill string with a mechanical vibrator attached to the top of the drill string at a frequency and amplitude to reduce the friction of the drill string against a side of the borehole and promote free movement of the drill string therein, whereby sticking of the drill string in the hole is mitigated.