Pore-scale study on miscible thermal displacing process in porous media using lattice Boltzmann method

A pore-scale investigation for a miscible thermal displacing process in porous media is performed in the present work using the lattice Boltzmann method. Particularly, the effects of viscous expansion coefficient βT and Lewis number Le on the displacing patterns and the residual rate σ are investigated. The numerical results show that the thermal displacement in porous media can be divided into four modes, i.e., one dominant displacement, conical displacement, local ramified displacement, and compact displacement. The prediction of the displacing modes for different values of βT and Le is summarized. Quantities analysis for characterizing thermal displacement indicates that σ in all simulation cases increases with βT, but the evolution trends of the residual rate for different Le are different. When β T > 0, the residual rate σ decreases with the increasing Le, while for the cases with β T < 0, the opposite is true. Furthermore, we found that σ changes obviously in the range of Le = 1-10, indicating that the thermal displacement mode can be easily changed by adjusting the thermal conductivity of the fluid to achieve different Lewis numbers of the system, thereby improving the displacement efficiency and displacement rate.