THERMODYNAMICS RELATED PROCESSES DURING THE MIGRATION OF ACID GASES AND METHANE IN DEEP SEDIMENTARY FORMATIONS

TMGAS, an EOS module of TOUGH2 V.2.0, was used to simulate the migration of CO2, H2S and CH4 in a deep sedimentary formation. The scope is the improvement of the description of non-condensable gas (NCG) migration within modelling studies of sedimentary basins evolution. Different scenarios have been simulated with NCG migration taking place in a large sedimentary formation discretized with a full 3D Voronoi approach by using specifically improved versions of the pre- and postprocessing tools developed for TOUGH2 by the University of Bologna. Simulated reference scenarios are related to the migration of CO2, H2S, and CH4 injected at constant rate for 1 Myr in a fresh water aquifer. Additional scenarios are simulated with NCG migration taking place in the same formation but saturated with brine. The effects of Pressure-Temperature-Composition (PTX) conditions on thermodynamic equilibria, phase composition, and phase thermophysical properties and, consequently, on the migration features of different NCGs are described and discussed.