Modeling the Hydrothermal Generation of Coals and Coal-Seam Gas

A two-dimensional computer program (HYDROMAT) for modeling the maturation of coal in sedimentary basins affected by hydrothermal circulation has been constructed. The program considers the effect of fluid flow on the thermal regime through time. The program contains: 1) a geodynamic module to simulate compaction, erosion, deposition, and tectonic uplift and subsidence of the sediments, 2) a fluid flow and thermal module to solve the coupled fluid flow and heat transfer equations, and 3) a chemical kinetic module to simulate the maturation of organic matter. The effect of magmatic intrusions during the evolution of a basin is considered. Coordinates fixed to the strata (Lagrangian coordinates) are used to follow the evolution of the coal generating units. The kinetic module uses the distribution of activation energies for parallel Arrhenius-type first order rate expressions to calculate the extent of chemical transformations over the thermal history of the basin. The program has been used to assess the effect of advective and/or convective fluid circulation on the generation of hydrocarbons. Our initial results suggest that for basins affected by high heat flow and fluid circulation, HYDROMAT can reproduce better the maturation of organic matter than conventional conductive models.