Removal of Near-wellbore Formation Damage by Ultrasonic Stimulation

The plugging removal effect under ultrasonic waves and the effect of rock properties, technical parameters, and ultrasonic parameters on the cleaning results were studied using the self-developed dynamic flow apparatus and the artificial cores damaged by in situ fines, inorganic scale, drilling mud, paraffin deposition, and polymer. The experimental results proved that ultrasonic cleaning is the most effective to inorganic scale damage, and the optimum ultrasonic irradiation time is about 80100 min. In addition, for the five types of damage, the increase of ultrasonic frequency and power drastically improve the permeability recovery rate. The results also indicated that, in in situ fines and inorganic scale experiments, the increase of initial core permeability increases the cleaning effect, and the trend is opposite in drilling mud, paraffin deposition, and polymer experiments.