Ultrasound-assisted CO2 flooding to improve oil recovery.

CO2 flooding process as a common enhanced oil recovery method may suffer from interface instability due to fingering and gravity override, therefore, in this study a method to improve the performance of CO2 flooding through an integrated ultraosund-CO2 flooding process is presented. Ultrasonic waves can deliver energy from a generator to oil and affect its properties such as internal energy and viscosity. Thus, a series of CO2 flooding experiments in the presence of ultrasonic waves were performed for controlled and uncontrolled temperature conditions. Results indicate that oil recovery was improved by using ultrasound-assisted CO2 flooding compared to conventional CO2 flooding. However, the changes were more pronounced for uncontrolled temperature conditions of ultrasound-assisted CO2 flooding. It was found that ultrasonic waves create a more stable interface between displacing and displaced fluids that could be due to the reductions in viscosity, capillary pressure and interfacial tension. In addition, higher CO2 injection rates, increases the recovery factor in all the experiments which highlights the importance of injection rate as another factor on reduction of the fingering effects and improvement of the sweep efficiency.