Multi-component multiphase lattice Boltzmann modeling of water purging during supercritical carbon dioxide extraction from geothermal reservoir pores

Carbon dioxide becomes supercritical and purges subcritical liquid water in the rock channels as extracted from geothermal reservoir pores. A pseudopotential multi-component multiphase lattice Boltzmann method is presented to simulate the dynamic behavior of the water droplets under the purge of the supercritical carbon dioxide. The model is verified by thermodynamic consistency, surface tension independence regulation, the coexistence of the two components at different viscosities, and surface contact angle distribution laws. The results show that the stronger the hydrophobicity of the wall with uniform adhesion, the faster the motion of the droplet, and when the wall adhesion is not uniform, the stronger the hydrophobicity of the upstream, the faster the purge. When there are two droplets, the volume of the first one rapidly becomes larger because of the absorption of moisture and encounters enhanced shear force to obtain greater velocity. The second droplet receives the shear force weakened by the first, so its growth rate and movement do not change significantly and will gradually be caught up, leading to the coalescence of the two droplets. As the droplets move and grow, the obstruction to flow increases and the pressure drop will increase.