Removal of formation damage induced by drilling and completion fluids with combination of ultrasonic and chemical technology

- Severe formation damage can be generated by drilling fluids and completion fluids.
- The combination of ultrasonic and chemical technology in permeability remedy is experimentally investigated.
- A combination of ultrasonic and chemical technique shows its advantages in treating formation damage.
- The combination technology is beneficial for long-chain polymer degradation, solid removal and chemical reaction.

Drilling fluids and completion fluids usually contains solids, high amounts of molecular and long-chain polymers, which may result in severe permeability damage. The application of ultrasonic waves has been widely used for formation remedy but the effectiveness on polymer-induced damage is limited by downhole acoustic intensity. Thus, the combination of ultrasonic and chemical (acid and chlorine dioxide) technology has been experimentally investigated in this paper. The effect of core initial permeability and the ultrasonic irradiation characteristics, including frequency and time interval, on the cleaning results were then investigated by an ultrasonic technique such that the optimal ultrasonic parameters could be selected. Experimental results demonstrate that the ultrasonic energy and frequency have positive relationships with cleaning effectiveness, and treatment time duration was measured to extend beyond 60 min to ensure a sufficient physicochemical reaction. A comparison with the plugging removal effect with independent chlorine dioxide (ClO2), acidizing, ultrasonic remedial treatments, and a combination of ultrasonic and chemical techniques indicates that the combination technique can produce better cleaning results because of the good coordination among the acid, oxidant and ultrasonic wave. The integration of acid, oxidant and ultrasonic technology is beneficial for long-chain polymer degradation and the removal of iron ion precipitation and solids, whereas ultrasonic energy can extend the chemical activation time3, increase the reaction rate and enhance the byproduct removal.