Down hole excitation system for loosening drill pipe stuck in a well

A method for freeing a section of drill pipe stuck in a well bore a substantial distance from the surface, said stuck section of pipe being connected to a drill string running to the surface, comprising the steps of,

• determining the location of the stuck section of pipe,
• disengaging the drill string running to the surface from the stuck section of pipe at a predetermined distance above the point where the pipe is stuck,
• withdrawing the disengaged drill string from the bore hole,
• connecting an orbiting mass oscillator unit and drive means for such unit to the bottom end of the drill string withdrawn from the bore hole and to be reinstalled therein,
• connecting a grappling device for engaging the stuck section of drill pipe to the bottom of the oscillator unit,
• lowering the drill string to be reinstalled along with the oscillator and grappling device into the well bore to effect the engagement of the grappling device with the stuck section of drill pipe,
• running a pressurized stream of liquid through the drill string to cause the drive means to rotatably drive the oscillator so as to generate lateral vibrational energy at a predetermined frequency, said energy being coupled to the stuck section of drill pipe to implement the freeing thereof, the frequency of said energy being such as to effect resonant standing wave vibration of the stuck section of pipe at a low order harmonic.