Pore-scale modeling of gravity-driven superheated vapor flooding process in porous media using the lattice Boltzmann method

In this work, a hybrid method combining interparticle-potential multiphase LBM, finite difference method and characteristic-line wetting scheme, is developed for pore-scale simulation of superheated vapor displacing liquid, driven by gravity, in a porous geometry. The influence of injected vapor superheat, surface wettability and gravity on two-phase displacement and heat transfer processes is investigated. Results show that in thermal displacement, the vapor-liquid interface is unstable and trapped liquid blobs gradually evaporate into vapor. At low vapor superheat degrees, the displacement efficiency, as compared to isothermal displacement, is significantly improved, but it reduces as the vapor superheat degree rises due to the shift of displacement patterns. At all contact angles considered, the displacement always exhibits viscous fingering, although vapor flowpaths become wider with increasing surface wettability. The final vapor saturation is insensitive to surface wettability, but reducing contact angle leads to a less even temperature distribution inside vapor and a decrease in final average vapor temperature. In addition, increasing gravity is found to reduce vapor front temperature, but it almost has no effect on final average vapor temperature because the final average vapor temperature does not only depend on specific interfacial length but also on fingering number and inlet flow rate.