The Processes, going on in the underground, are regarding geothermal problems highly complex. Production of geothermal fluid and injection of the cooled down fluid change not only the temperature of the surrounding rock but also a variety of other parameters. The pressure decrease at the production well and the pressure increase at the injection well change the stress in the underground, additionally thermal stress changes can be determined. Accompanied are the changes in temperature and pressure with chemical interactions of solved minerals to the reservoir rock and the surface power plant system.

To understand the effects of the high-grade coupled processes and the impact on the geothermal reservoir numerical modelling are of prime importance. The chemical and physical processes are described by differential equations which set up a whole system of equations. These system can be solved by mathematical methods like the finite difference method or the finite element method. Numerical modelling can thus been used to analyze the upcoming processes with changed underground parameters and data.

Depending on the aim of the study different modelling tools are applied. These are OpenGeoSys for the reservoir modelling, Abaqus for mechanical issues, TOUGHREACT, PhreeqC and Elmer for geochemical problems and SOFI3D for the propagation of seismic waves.