Study On Characteristics Of Two-Phase Flow In Porous Media With Lattice Boltzmann Method

In the process of oil and gas development,especially in the tertiary oil recovery,such as water drive and gas drive,the viscous fingering phenomenon always happens.And the occurrence of this phenomenon will decrease the recovery efficiency.Hence,the study on the immiscible two–phase displacement process in porous media is very necessary.The characteristics of the lattice Boltzmann method is simply boundary treatment and natural parallelism.And the Shan-Chen LB model which is for the multiphase flow can capture the two-phase interface automatically and control the strength of the fluid–solid adhesion directly.Based on the above reasons,in this paper,the Shan-Chen model is used to simulate the the immiscible two-phase displacement process in a porous media in pore scale.The main contents are as follows:(1)Based on the D2Q9 model,the flow in a lid driven cavity and the flow around a circular cylinder are simulated with different boundary schemes,and the results were compared with the benchmarks.The random porous media under different porosity is reconstructed using the quartet structure generation set(QSGS)method,and the flow in this reconstructed porous media is simulated.Dynamic behaviors of the steady droplet and two-phase square cavity flow are simulated with Shan-Chen model.The results above mentioned agree with the available literatures.So the feasibility and validity of the lattice Boltzmann method is validated in multiphase flow in porous media.(2)Based on the single pore model,the immiscible two-phase displacement process in single channel is simulated with the Shan-Chen model.The results show that the Shan-Chen model can be used to simulate the two-phase displacement process well.The immiscible two-phase displacement process in porous media reconstructed by QSGS method is studied.The results indicate that among the range in this research,with the increase of the viscosity ratio,the interaction force and the decrease of the porosity,the fingering phenomenon becomes more obvious,which leads to a great quantity of displaced fluid residues in the porous media zone,and the volume fraction of the displaced phase increases,which reduces the displacement efficiency.The pore structure has little influence on the displacement efficiency,and the regular structure makes the efficiency improved slightly.Under the action of gravity,the interface front has a tendency of moving along the direction of gravity,and the phenomenon of fluid channeling appears,which makes the fingering phenomenon obvious,and the volume fraction of the displaced phase is great than that without gravity,which reduces the displacement efficiency.(3)According to the contact angle formula,the relationship between the fluid-solid interaction force and the contact angle is given.On the basis of this relationship,wettability fluid and non-wettability fluid are displaced respectively without gravity.It indicates that the wettability displacement fluid can improve the displacement efficiency.In this way,the effects of the contact angle on the displacement process are studied.It indicates that for wettability displacement fluid,when the wettability is neutrally and slightly water wet,the displacement efficiency is maximal.