1D Numerical Simulation On Effect Of Elastic Wave On Oil-Water Flow In Porous Media

As a novel way to enhance oil recovery,the intensified production by low-frequency elastic waves has successfully achieved dynamic oil displacement as the reservoir rock and fluids are affected by the high-power synchronous resonant waves whose frequency lies between a few to hundreds of Hz.This technique,thanks to its higher cost-efficient performance,a simpler working process and the environmental friendliness,has gradually been widely-recognized and enjoyed a bright perspective of field application.However,currently researchers have made inadequate theoretical studies on the intensified production by low-frequency elastic waves,which leads to its poor and unstable performance in the field experiment and even causes the technological underdevelopment.In this connection,this study presents an 1D oil-water fluid-structure interaction（FSI）model on the basis of the Boit theory and the theory of equivalent fluids.Derivation of the mathematical model is conducted based on the 1D physical model incorporating the image reflection on the weakening boundary of the PML perfectly-matched layers.In this way,the numerical solution to this model is obtained by the method of numerical discretization.By comparing the permeability increments and changes in the frequency of elastic waves both from the numerical simulation and the experiment,the model in the thesis is verified and validated as a correct and reliable one.Eventually,the thesis shows how the intensified oil production by low-frequency elastic waves affects relative velocity of oil and water,oil saturation,water saturation,pore pressure and oil recovery,and also how sensitive it is to the wave fluctuation of elastic waves,such as frequency and amplitude,and reservoir properties including initial porosity,initial permeability and initial viscosity of water and oil respectively.Results show that compared with conventional model of Darcy’s flow,the elastic wave fluctuation slightly decreases the oil recovery and increases the relative velocity and pore pressure.Closer to the core of the elastic wave generator will contribute to a better performance of the fluid flow through the porous media.With the given data,the best performance of the intensified oil production by low-frequency elastic waves depends on both the optimized wave frequency（10⁶0Hz）and amplitude（150³00μm）.Changes in the physical properties are much easier to observe in the low-permeability and low-porosity reservoir(basically k₀<30×10^-3μm²,Φ<0.1).Better oil displacement is perceived as the viscosity of oil phase is less than 40mPa.s.As such,these observations tell a better application of the intensified oil production by low-frequency elastic waves in the low-permeability and low-porosity reservoir.