Maren Brehme

ETH Zurich

Perspectives on the sustainable exploration and operation of geothermal systems

Geothermal energy is a key contributor to the successful energy transition worldwide as part of mitigating climate change. In order to utilize this resource, a massive extension of geothermal energy use is needed. Given these ambitious expansion plans, there is an urgent need for geothermal expert understanding of geothermal systems.

The Energi Simulation Group for Geothermal Exploration and Operation will focus on three Strategic Research Areas: 1) Geothermal Systems Understanding, 2) Effective Utilization of Systems, and 3) System Response to Utilization. The specific research topics focus on various aspects along the whole chain of geothermal energy production from understanding, through utilization towards monitoring of long-term utilization. At these different development stages questions arise, including ‘Where to drill the next well?’, ‘How to utilize a geothermal system in the most effective manner?’ or ‘What is the safest way to utilize geothermal systems?’ The approach to tackle these research areas include field work, laboratory measurements, and numerical simulations and will make use of geological, geophysical, hydrogeochemical, and hydrogeological methods. Real-scale and real-time data will be obtained in geothermal fields from wells, the power plant infrastructure, hot springs, or surface outcrops. Rock and fluid samples are thoroughly tested on their composition, their behavior towards fluid flow, and mechanical properties in the worldwide unique ‘Geosystem REActive Transport (GREAT) Visualization Lab.’ All data are eventually used to calibrate advanced numerical simulators (the codes) and associated numerical models (from static to dynamic), both developed or modified in-house and external ones, simulating all relevant processes and their coupling i.e., thermal, hydraulic, (rock) mechanical, and chemical reactions, so-called THMC simulations. Here fluid flow is often multiphase and multicomponent and phase transitions (e.g. mineral precipitation, gas exsolution from a liquid, etc.) occur frequently, as geothermal system utilization disturbs the thermodynamic and chemical equilibria that often have established themselves over millions of years.