Improved Oil Recovery by Application of Ultrasound Waves to Waterflooding

Abstract

Abstract In oil reservoirs about 60% of the original oil in place remains as residual oil after primary and secondary oil recovery because of geological and physical factors. By means of improved oil recovery methods, additional oil can be mobilized. However, there is no universal IOR method to be implemented in any reservoir. Therefore, efforts are made to develop alternative tertiary methods with lower application risk. One of these alternatives is the application of sound/ultrasound waves in the reservoirs to overcome the interfacial tension between oil and water, resulted in reduction of capillary pressure in the pores. In this study, laboratory experiments on core samples were conducted to investigate the effectivity of ultrasound waves on mobilizing additional oil. The core flooding was performed horizontally and vertically and the wave stimulation was applied at original oil in place and at residual oil saturation after initial waterflooding. Oil/water relative permeability were calculated to evaluate the flooding performance in presence and absence of wave stimulation and the rate of oil recovery was determined. In addition, water fractional flow curves were considered to determine the average water saturation after breakthrough in presence and absence of ultrasound waves. Moreover, the effect of wave stimulation on unconsolidated core samples was investigated. Results show that the rate of oil displacement increases due to various identified mechanisms, and the interaction of the generated waves with the fluids in porous media causes changes in relative permeability and in water breakthrough. Wave stimulation at residual oil saturation lead to higher oil recovery than that at original oil in place and therefore, this method is advised to be used in depleted reservoirs. Moreover, wave stimulation on core sample with a compressive strength less than 150 psi (unconsolidated) is not recommended due to sand production.