| Oil-gas migration,accumulation,exploitation,gathering,processing,storage and transportation in petrochemical industry involve complex oil-gas flow and heat transfer.Multiphase flow and heat transfer are involved in many production process such as oil and gas migration process in the reservoir rock,oil and gas processing,storage and transportation process.The exploration of mechanism for multiphase flow and heat transfer in the porous media is becoming more and more important for the fields of oil drilling and development.Reservoir rock is a typical porous media,and its internal structure is very complex.Therefore,the process of multiphase flow and heat transfer in porous media is very complicated.So far,the laws of flow and heat transfer in porous media have not been fully understood.Lattice Boltzmann method(LBM) is a numerical method of mesoscopic scale.After decades of research and development,its basic theory and model can be developed and improved.It is accurate,effective and flexible that the fluid flow and heat transfer in the porous media are vestigated using LBM with unique advantages in dealing with complicated boundary.It provides technical reference and theoretical foundation for accurately simulating the complex multiphase flow and heat transfer process in reservoir rocks and revealing the distribution of flow and temperature field.According to the single relaxation time(SRT) method of LBM,the fluid flow model in porous media was established.The finite size particle(FSP) method was used to construct porous media skeleton and movable suspended particles.The rebound scheme was adopted to solve the interactions of fluid and solid skeleton,and the momentum exchange method was used to deal with the interactions between the fluid and suspended particles.According to the multi-component DDF method,a double-distribution lattice Boltzmann model for fluid flow and heat transfer in porous media was established.Periodic boundary scheme,rebound scheme and non-equilibrium extrapolation method were used to deal with flow boundary such as pressure,velocity,non-slip,and thermal boundary such as adiabatic and isothermal,and so on.The spherical particles produced by finite size particles were used as the skeleton of porous media.The seepage behavior of oil-water mixture in porous media was studied using LBM.The model was validated by simulation Poiseuille flow and analysis seepage law of fluid in the linear region,transition region and strong inertial region.The simulation results were compared with the experimental results,the basic formula of seepage flow and the simulation results using the multi-relaxation time(MRT) method.It shows that the accuracy and stability of the model can be used to simulate the seepage of porous media in the reservoir.The seepage flow under different inlet/outlet pressure difference was simulated,and the distributions of flow behavior with Re in linear region,transition region and strong inertial region were analyzed.Reynolds stress and viscous stress were calculated and compared in different areas.The results show that the viscous stress is much larger than Reynolds stress in the linear,the two are equivalent in the transition region,and Reynolds stress is greater than the viscous stress in the strong inertial region.Reynolds stress increases with the increase of Re,and the effect of porous media structure on Reynolds stress decreases with the increase of Re.The influence of water content in crude oil on seepage flow in porous media was simulated.It is found that the seepage velocity decreases with the increase of water content under the same pressure difference between inlet and outlet,and the reduce degree of seepage velocity decreases with the inlet/oulet pressure difference increase(water content increased from 0.0 to 0.5,the velocity decreased by 53.4% when ?P=100 Pa,46.9% when ?P=5000 Pa,and 30.8% when ?P=30000 Pa).It shows that the influence of water content in crude oil on seepage behavior is different in linear region,transition region and strong inertial region.The FSP-DDF coupling model of fluid flow and heat transfer in porous media was constructed.The flow and thermal boundary conditions of the model were verified by the natural convection of two-dimensional square cavity(when Ra?10~6,the error is less than or equal to 1%,and Ra?10~7,the error is within 4%)and three-dimensional cube.The thermal diffusion process of the fluid around the sphere at a constant high temperature was simulated.The fluid flow and heat transfer in porous media were simulated using FSP-DDF coupling model based on pore scale,and the detailed temperature and velocity distribution in complex porous media were obtained.The influence of the seepage velocity on flow and heat transfer process was discussed.Simulation results show that the velocity fluctuations produced by the structure of porous media increases with the increase of Re.The axial distribution of fluid temperature in the strong inertia region will fluctuate obviously with the increase of seepage velocity.The influence of water content in crude oil on the fluid temperature distribution in porous media was analysed.It is found that the fluid temperature varies uniformly with the water content in linear and transition region,and the higher the water content,the greater the influence on the distribution of fluid temperature in the strong inertial region.The effects of the particle number in the pores of reservoir on seepage and heat transfer were obtained.The influence of heat conduction on the heat transfer is weaker than convective heat transfer in the heat transfer process dominated by convective heat transfer and the fluid under the same mass force,and the total heat transfer effect decreases with the increase of the particle number in the pores.The interaction model between fluid and moving particles was established to study the sedimentation law of solid particles in the pores.First,the drag coefficients under different Re were calculated by analyzing the forces exerted on a single spherical particle in a uniform flow field with infinite boundary.The results are in good agreement with the experimental results.The process of single particle passing through flat channel with fluid was studied.The results show that the distance of particle settlement decreases with the increase of particle diameter(50?200?m) and solid-fluid density ratio(1.2?3.0),and increases with the increase of fluid velocity.The simulation calculation of four cases with different relative positions of the double particles at the initial time indicates that the different positions of the particles have a great impact on the settlement of the particles,which is affected by the inlet and outlet effects and is related to the velocity of the fluid and the vertical position of the particles.The settlement of a single particle in a curved channel was studied.The results show that the movement of a single particle in a curved channel is affected by the effects of inlet and outlet and the fluctuations of the wall surface.The heat transfer process of the four cases with different relative positions of the double particles at the initial time was analyzed.It indicates that the change of the particle temperature mainly depends on the vertical position of the particles and the residence time at different vertical positions.Finally,the processes of multi-particle moving with fluid and heat transfer in the curved channel were simulated.It shows that the existence of particles will cause certain disturbance to the temperature field,and the temperature variation is no longer uniform,and the heat transfer is enhanced to some extent at the position of particles.The influence of particles on the temperature distribution gradually decreases with the time starts from the initial state,goes through the unstable process and finally reaches the steady state. |
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