Mathematical modelling of geothermal reservoirs

High enthalpy geothermal reservoirs consists essentially of three components, namely, a strong underground heat source, the presence of a
water reservoir, and a highly permeable porous medium or fractured rocks. As a physical system, such a complex liquid-solid interaction
can be modelled, once some basic assumptions on the physics, such as thermodynamic equilibrium, are made.
We show the process leading to the mathematical modelling of a geothermal reservoir, focussing in particular on the mass, momentum and energy
balance equations, on the coupling between balance equations and thermodynamics. Some further insights on the main aspects of the
thermodynamics of the geothermal fluids will also be given.
Finally, we show how boundary conditions turn out to be crucial on such systems, when applied to simplified 1 and 2D models.