Oscillating electric field-induced water blocking breakthrough to facilitate CO2 miscible flooding

Abstract

CO2 miscible flooding is a great promising enhanced oil recovery (EOR) method. However, the loss of fracturing fluid in the formation causes water blocking that seriously impedes the realisation of CO2 miscible flooding. To solve this problem, a strategy of applying an oscillating electric field to promote CO2 breaking through water blocking and enhance the miscibility of CO2 and oil is proposed. The electric field with the frequency of 12 THz can maximise the breakthrough efficiency of water blocking, while the 16 THz electric field is most conducive to the miscibility of CO2 and oil. Under the 12 THz oscillating electric field, the prompt destruction of the local hydrogen bonds in water blocking results in the fastest breakthrough of water blocking. However, the expansion of water blocking hinders the miscibility of CO2 and oil to some extent. 16 THz oscillating electric field can induce the electric resonance of hydrogen bonds between water molecules, uniformly breaking hydrogen bonds to the greatest extent. Compared to that under the 12 THz electric field, the miscibility of CO2 and oil under the 16 THz electric field is enhanced due to the reduced expansion of water blocking.