Effective of Ultrasonic Energy on Cleaning near Wellbore Damage

摘要

Experiments were conducted with dynamic and static invasion of drilling and completion fluids into the core for the time period of 10 to 20 hours depending on size of the core. After core was damaged, 20 kHz frequency ultrasonic wave with different amplitudes, 30, 50 and 70%, were used to clean the damage. Sonic incremental time is 5 minutes for small core and 12 minutes for large core. After each sonication, permeability of the core was measured and compared with the initial permeability of the core. CT scan was performed for initial state, after mud invasion and after cleaning.In the study, the sonic horn was put either perpendicular and parallel to the damaged zone to test which way is more effective to clean the damage. The results show that the cleaning efficiency is dramatically increased for horn parallel to the damage zone than the perpendicular one. Ultrasonic cleaning the near wellbore damage is even more effective if the horn is moving when horn is parallel to the damage. The return permeability of simulating wellbore core can be as high as 90% of original permeability. The mechanism is that the parallel position of the horn can make a lot of micro streaming flow into the damaged zone and cany out the fines released by sonic vibrating into the wellbore. The CT scan pictures show the core almost return to its original state after ultrasonic cleaning.