Numerical Simulation Study Of Electrowetting-on-dielectric Characteristics In Reservoir Porous Media

Water flooding is the main development way in reservoir at present. In the process of water flooding development, the wettability of reservoir porous media has very important influence on the development effect. If the reservoir wettability is changed from the oil wetting to water wetting, the water flooding recovery can be improved greatly. Electrowetting-on-dielectric(EWOD) can control the wetting situation of fluid on the solid medium by changing the electric field applied between the liquid and solid medium, thus the study of Electrowetting-on-dielectric characteristics in reservoir porous media has great significance.This thesis studied the mechanism of EWOD in the micro-pore saturated oil-water and its influences on water flooding by theoretical analysis and numerical simulation. First, the electric force at the oil-water interface under the electric field condition is analyzed from the perspective of electrohydrodynamic, the contact angle is expressed by electric force, and the physical essence of the electrowetting-on-dielectric in the micro-pore saturated oil-water is explained theoretically.Then, the porous media is simplified as a two-dimensional micro-pore model which is saturated oil-water two-phase, the electric field-flow field-level set function coupled mathematical model of electrowetting-on-dielectric in a micro-pore was developed, the process of electrowetting-on-dielectric in the micro-pore saturated oil-water is also simulated, and the electric potential distribution, pressure distribution, shape and placement changes of the oil-water interface, and contact angle changes are calculated at last. The simulation results further explain the mechanism of the electrowetting-on-dielectric in the micro-pore.The last, based on the mathematical model has been developed, the process of water flooding in the micro-pore with electrowetting-on-dielectric is simulated, and the influences of factors on the Electrowetting-on-dielectric effect in water flooding are discussed. Factors which discussed here are applied electric field, the micro-pore radius, dielectric constant, interfacial tension, oil viscosity, and injection pressure.The results show that the essence of Electrowetting-on-dielectric effect in the micro-pore saturated oil-water is the electric force acting on the oil-water interface, the contact angle of water changed from 120 degrees to 80 degrees, and the wettability of the micro-pore is changed from the oil wetting to water wetting; Electrowetting-on-dielectric has apparent effect on water flooding, with the increasing of the pore radius and rock dielectric constant,and decreasing of the oil-water interfacial tension and oil viscosity, the oil production rate and oil recovery of water flooding become higher. The results from the study provide a theoretical basis for EWOD in the practical application of water flooding development.