Introduction

SHEMAT (Simulator for HEat and MAss Transport) is an easy-to-use, general purpose reactive transport simulation code for a wide variety of thermal and hydrogeological problems in two and three dimensions. Specifically, SHEMAT solves coupled problems involving fluid flow, heat transfer, species transport, and chemical water-rock interaction in fluid-saturated porous media. It can handle a wide range of time scales. Therefore, it is useful to address both technical and geological processes. In particular, it offers special and attractive features for modeling steady-state and transient processes in hydro-geothermal reservoirs. This makes it well suited to predict the long-term behavior of heat mining installations in hot aquifers with highly saline brines. SHEMAT in its present form evolved from a fully coupled flow and heat transport model (Clauser 1988) which had been developed from the isothermal USGS 3-D groundwater model of Trescott and Larson (Trescott 1975; Trescott and Larson 1977). Transport of dissolved species, geochemical reactions between the solid and fluid phases, extended coupling between the individual processes (most notably between porosity and permeability), and a convenient user interface (developed from Processing Modflow (Chiang and Kinzelbach 2001)) were added during several research projects funded by the German Science Foundation (DFG) under grant CL 121/7 and the German Federal Ministries for Education, Science, Research, and Technology (BMBF) under grant 032 69 95A-D and for Economics and Technology (BMWi) under grant 0327095 (Bartels et al. 2002, Kühn et al. 2002a).