Patent ID: 6899175

Claim:
A method of producing a shock wave in a well having a borehole extending into a formation comprising the steps of: positioning a device having a chamber and an internal bore in liquid in the borehole such that the internal bore is in fluid communication with liquid in the well, said internal bore and said chamber having cross-sectional areas, said cross-sectional area of the internal bore being less than the cross-sectional area of the chamber; delivering liquid into the bore; moving a piston on a piston assembly through the bore to pressurize liquid in the chamber; moving the piston out of the bore into the chamber for releasing pressurized liquid through the bore into the liquid in the well to form shock waves in the liquid, said piston assembly including a rod and a piston, said rod extending through a second bore in sealing relation with said rod; and; adjusting the distance between the device and the bottom of the well to a distance which is sufficient to adjust the frequency of reflected waves traveling back and forth between the device and the bottom of the well relative to the dominant frequency of the formation.