Study of the cavity development during the ``El Tremedal`` underground coal gasification trial at great depth

During the underground coal gasification experiments at Alcorisa, a series of tracer tests using helium as injected material were effected. These tests illustrated the hydrodynamics of the flow profile inside the underground reactor during the main operating periods. The models developed to simulate the flow conditions are based on the material exchange between flowing fluid and a dead zone. The dead zone is represented by a homogeneous porous zone exchanging material with the flowing fluid by diffusion. The reactor volume calculated from the tracer results increases with the cumulative quantity of oxygen injected.