Seismic wave propagation in geothermal hot rocks: a review of simulation analysis and results based on Burgers models

High-enthalpy geothermal systems are investigated for the exploitation of geothermal energy resources. Such systems are often associated with active volcanic centres, in particular nearby the brittle-ductile transition (BDT) where partial melting occurs and supercritical fluids can exist. The seismic characterization of high-enthalpy geothermal areas is important to: better understand and determine the geological context of the geothermal resource, better define the conceptual model, plan and steer drilling thus reducing the drilling risk, provide knowledge about underground reservoirs and useful information to characterize and monitor the geothermal systems. We review recent research on numerical methods for the simulation of seismic full waveform propagation in poro-viscoelastic geothermal hot rocks including the effect of temperature, the presence of saturating fluids also in supercritical conditions and presence of melted materials. The algorithms, simulating propagation of the full waveform in a crust characterized by brittle and ductile behaviours, are based on the Burgers mechanical model, Arrhenius equation and include the Gassmann equation for porous media. Examples show the capability of the simulators to seismically retrieve temperature-induced and phase-material changes. These studies are the basis for the application of the method with data from real cases of superhot geothermal sites including supercritical fluids and melting conditions.