Rod string sonic stimulator and method for facilitating the flow from petroleum wells

In a petroleum well pumping system for pumping liquid out of said well having a tubing string running down the well, a rod string of an elastic material within and running along said tubing string, vibration generator means for providing vibrational energy to said rod string at a frequency such as to effect resonant standing wave vibration thereof, and a plurality of sonic impeller elements mounted on said rod string at spaced intervals therealong, the improvement being means for unclogging and removing contaminants from the earthen formation surrounding the well and from perforations in the tubing string comprising:

• a piston member attached to the bottom end of said rod string, said piston member being immersed in the liquid in said well and being driven by said vibrational energy, said piston member radiating said energy into the liquid and thence to said formation to free contaminants therein, said piston member being dimensioned so as to operate as a monopole in said liquid at the frequency of said vibrational energy.