Study On Porous Media Seepage By Lattice Boltzmann Method

Porous media seepage exists in nature and production widely.It is the foundation of petroleum development and related research is very important.The flow in porous media involves complex interactions,it is difficult to characterize and recognize the characteristics of internal flow clearly.During the oil and gas production process,the relative penneability curve data and the capillary pressure curve data play an important role,but in most cases both of them can only be obtained by experimental methods,which are time-consuming,expensive and easy to be affected by experimental environment and equipment.With the continuous development of computer technology,numerical simulation methods gradually reflect its advantages.Compared with experimental and theoretical methods,numerical simulation methods have greater flexibility.As a promising numerical simulation tool in recent years,the lattice Boltzmann method has the advantages of simple and clear evolution process,easy programming and easy processing of complex boundary conditions.Based on the lattice Boltzmann method,the purpose of this paper is to study the percolation mechanism of porous media more deeply,and to analyze the scientificalness of lattice Boltzmann method in simulating porous media seepage and the influence of parameters on the simulation results to provide some help for the related work in the future.The main research work and understanding are as follows:(1)By using lattice Boltzmann method to simulate Poiseuille flow,roof driving flow and two-phase separation,the feasibility of simulation method and program are verified.(2)Using lattice Boltzmann method to study of porous media seepage needs to consider the applicable conditions of Darcy's law.If the pressure gyradient or displacement force is too large,there will be nonlinear flow.(3)Using lattice Boltzmann method to study the percolation of porous media,the distribution of pressure,density and percolation velocity in porous media can be analyzed intuitively,which provides a new idea and method for the study of porous media seepage.But the results of different boundary conditions are different:compared with the periodic boundary,the pressure boundary can reflect the compressibility,density and pressure variation trend of the fluid,which is more in line with the actual situation.(4)When the lattice Boltzmann method simulates the steady-state method to calculate the phase permeability curve,the initial distribution mode of fluid will affect the results:the more complex the structure of porous media,the more susceptible to the initial distribution of fluid.Therefore,it is necessary to simulate multiple times to get the average value to reduce the differences caused by different distribution patterns.(5)In the simulation process,when the difference in wettability of the two-phase fluid is large,the connectivity of the fluid in the porous medium is strengthened and two-phase fluid tends to converge and flow;when the wettability of the two-phase fluid is close,the fluid flows in a bulk distribution in the porous medium.(6)Using different boundary conditions will affect the relative pemeability results.The lattice Boltzmann method uses the periodic boundary to analyze the influence of wettability,displacement force,and viscosity on the relative permeability curve qualitatively and the obtained results accord with the experimental laws;the distribution characteristics of the pressure and flow velocity,which under pressure boundary conditions,are more consistent with the experimental study.Studying the issue of relative permeability,appropriate boundary conditions need to be selected based on the content of the study.