Numerical Simulation Of Single Phase Seepage In Homogeneous Low Permeability Reservoir Under Low Frequency Vibration

Low-frequency vibration development technology,as a physical recovery method,has been well applied to low and extra-low permeability reservoirs.The research on low-frequency elastic wave propagation in porous media saturated with seepage fluid is the foundation to reveal the mechanism of vibration enhancing oil recovery and parameters optimization.First,this paper introduces the wave induced flow to traditional Biot wave equation,combined with the continuity equations of fluid and solid subjected to fluctuations,state equations of porosity,density and fluid viscosity and starting pressure gradient models in the low permeability reservoir,to form the elastic wave equations in low permeability reservoirs.In order to achieve the simulation of elastic wave propagation in infinite area within a limited reservoir area,this paper uses PML perfectly matched layers and optimizes mesh combination of reservoir region and perfectly matched layers.This paper compares the influence of low frequency vibration on reservoir pressure,fluid seepage velocity and porosity,using the low frequency vibration propagation model in porous media saturated with seepage fluid,to determine the wave equation form used in this article.Meanwhile,this paper studies the variation of permeability in low permeability reservoir under different amplitudes and vibration accelerations and compares this with precious results to verify the reliability of the model.It can be seen from the numerical simulation results that in homogeneous reservoirs,the rock and fluid flow characteristics have shown fluctuations trend.For reservoirs with different permeability and porosities,the improvement of permeability and porosities in low permeability and porosities reservoirs is greater and the fluid velocity is faster under the low frequency vibration.Under the effect of low frequency vibration,the max rock strain is about4.5×10^-4,the porosity can be increased maximally by 20.00%,the permeability can be increased maximally by 25.97%and the fluid seepage velocity is about 1.1×10^-3m/s.There is about 20MPa added to the original pressure,increased by 20.00%.In conclusion,low frequency vibration can be used to improve the permeability and porosity in low permeability reservoir and this can provide the field application of low frequency vibration with some theoretical guidance.