Method and system for extending reach in deviated wellbores using selected vibration frequency

A method for extending reach of a coiled tubing string in a deviated wellbore includes determining a frequency of vibration of the tubing string based on a function of the bending resonance of the tubing string and vibrating the tubing string at the determined frequency while the tubing string is inside the wellbore. Embodiments may also include a non-transitory computer-readable storage medium to execute the foregoing method and a system for extending reach of a coiled tubing string in a deviated wellbore.