Recent research led by Gabriel G. Meyer from the Laboratory of Experimental Rock Mechanics at the Ecole Polytechnique Fédérale de Lausanne has unveiled new insights into the permeability of rocks in supercritical geothermal reservoirs, a development that could significantly enhance the viability of geothermal energy as a renewable resource. Published in Nature Communications, this study highlights how the behavior of rocks under extreme conditions can influence energy production.
Supercritical geothermal systems, which operate at temperatures of 400°C or higher, have the potential to produce up to ten times more power than traditional geothermal plants. However, these systems are often located in regions where the geological conditions make it challenging to create the necessary fractures for fluid circulation. This research addresses a critical gap in understanding how permeability changes within the brittle-to-ductile transition zone of the Earth’s crust, a region where rocks transition from being rigid to more pliable.
Meyer and his team employed advanced techniques, including a gas-based triaxial apparatus and high-resolution synchrotron imaging, to study rock samples under supercritical conditions. Their findings reveal that strain partitioning plays a crucial role in determining rock permeability. In the brittle regime, strain tends to localize on existing faults, but this does not necessarily increase the overall permeability of the rock. Conversely, in the semi-ductile regime, the distribution of strain can significantly enhance permeability by more than tenfold, both within deformation bands and throughout the bulk of the rock.
This revelation challenges the prevailing notion that the brittle-ductile transition acts as a barrier for fluid movement in the crust. Meyer states, “This study challenges the belief that the brittle-ductile transition (BDT) marks a cutoff for fluid circulation in the crust, demonstrating that permeability can develop in deforming semi-ductile rocks.” This understanding opens up new opportunities for harnessing geothermal energy in areas previously thought unsuitable for such projects.
The commercial implications are substantial. Companies in the geothermal sector may now explore previously overlooked regions for potential energy extraction, significantly expanding the geographical scope of geothermal projects. Additionally, this research could lead to innovations in drilling techniques and reservoir management, ultimately reducing costs and increasing the efficiency of geothermal energy production.
As the global energy landscape increasingly shifts towards sustainable sources, the insights gained from this research could play a pivotal role in advancing geothermal energy technology. By overcoming geological challenges, the potential for supercritical geothermal reservoirs to contribute to clean energy goals becomes more attainable, marking a significant step forward in the transition to renewable energy.
