Jaber Taheri Shakib - Division of Petroleum Engineering, Faculty of upstream Petroleum Industry, Research Institute of Petroleum Industry (RIPI), Tehran.
Hassan Naderi - Division of Petroleum Engineering, Faculty of upstream Petroleum Industry, Research Institute of Petroleum Industry (RIPI), Tehran
Yaser Salimidelshad - Division of Petroleum Engineering, Faculty of upstream Petroleum Industry, Research Institute of Petroleum Industry (RIPI), Tehran.
Ezzatollah Kazemzadeh - Division of Petroleum Engineering, Faculty of upstream Petroleum Industry, Research Institute of Petroleum Industry (RIPI), Tehran

Inorganic and organic scales are one of the crucial problems associated with oil and gas wells which severely reduce production of reservoir. One of the new technologies in reducing skin is using ultrasonic waves method. Ultrasonic waves are mechanical waves that their frequency is higher than 20 KHz. These waves as a mechanical method and or resonator of chemical reactions are efficient in removing formed scales near wellbore region. It should be noted that these waves also cause some changes in the rock which are not addressed well in the literature. In this paper, mechanism of effectiveness of the ultrasonic waves on core samples after petrophysical changes such as porosity and permeability is discussed. Several numbers of core samples exposed to ultrasonic wave at a frequency of 22 KHz and a power of 1000 w and their petrophysical properties measured. Ultrasonic waves arise expansion and contraction fluctuations in their propagating path which are a function of Lame coefficient and hardness factor. Primary results reveal that the permeability of core samples under ultrasonic waves altered severely due to cavitation phenomenon. SEM images show microfractures in the wave propagation path in a regular order. Furthermore, cores petrophysical and geomechanical parameters show some alterations which are discussed in detail in this study.

Ultrasonic, Core, Wormhole, Limestone, Dolomite