A numerical investigation into the environmental impact of underground coal gasification technology based on a coupled thermal-hydro-chemical model

This study aims to improve the understanding of potential environmental impact underground coal gasification (UCG) process based on a numerical investigation gaseous and dissolved chemicals’ transport in strata surrounding UCG reactor. A coupled thermal-hydro-chemical (THC) model framework COMPASS code is employed further developed for this purpose. The compared against analytical solutions verification applied former trial (Hoe Creek programme) validation then investigate three different geological materials (sandstone, coal, shale) two steps: gas propagation during solute decommissioning stage. results indicate that limited near-cavity area with low permeability high air entry value such as shale, which mainly attributed dry zone generated by temperature, while larger plume observed poor water retention characteristics, sandstone. Besides, retarded some extent due reducing effect pressure diffusion. chemicals via diffusion areas, i.e. 2 m, studied after 10 years. Based improved various migration materials, selecting target seam surrounded layers permeability, losses from reactor operation stage can be minimized negative ash leaching avoided. work also provides insight suggestions into importance investigating adsorption capacities media evaluate their performance natural cleaning system.