Coupled hydro-thermal analysis of underground coal gasification reactor cool down for subsequent CO2 storage

The present study investigates the time dependency of a UCG (Underground Coal Gasification) reactor cool down process by comparing natural cool down with forced cooling driven by water flushing. The convective heat transport out of the UCG reactor was calculated using an analytical approach coupled to a numerical heat flow model of the geology surrounding the UCG reactor. Our results show that forced cooling by water flushing at flow velocities of 1 m/s can decrease the required time to retain initial in-situ temperature conditions by a factor of more than 300.