Sonic vibrations

 “Method for improving the efficiency and perfecting the rotative drilling through percussive rotation and hydrodynamic pressure absorption.”
During the 1930s the engineer Dr Ion Basgan was the first to introduce sonic vibrations in the drill pipe string of a conventional rotary drilling rig. The sonic currents caused the steel pipe string to oscillate up and down and thus to produce powerful blows on the bottom of the borehole through the rotating drill bit. This enabled the depth and speed of drilling to be greatly increased. It also enabled the drill to bore a truly vertical hole without distortion, which was not always possible with the old method. For example, at the Moreni oil fields in Romania in 1938 a bore hole was drilled 1,915 metres (6,300 feet) deep in 30 days by this method. Picure taken in Steaua Romana Moreni oilfield.