| Title | Micromechanics of Fluid-Induced Fault Reactivation From 4D X-Ray Microtomography |
|---|---|
| Authors | Birhanmeskel Woldemichael, Alexis Cartwright–Taylor, Elli-Maria Charalampidou, Nathaniel Forbes |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | Most deep geothermal energy systems involve extracting hot fluids and reinjecting cooler fluids into the subsurface. This process alters subsurface stresses through hydro-mechanical and thermal effects and can induce seismicity. For example, projects in Pohang, South Korea, and Cerro Prieto, Mexico, have produced seismic events of magnitude 5.5 and 5.0, respectively. Such events have raised concerns about the commercial viability of deep geothermal projects, particularly regarding economic and geological risks, as well as social acceptance related to hydraulic stimulation and fluid extraction. Safe stimulation strategies require effective planning and operational management to minimise the risk of induced seismicity, in an ideal case including monitoring of fluid flow, seismic events and ground deformation. Currently, induced seismicity is regulated using a ‘traffic light’ system based on the maximum magnitude of recorded seismic events. However, management of induced seismicity requires more advanced systems, such as varying the injection protocol continuously instead of waiting for the thresholds to be exceeded when it may be too late. To better manage induced seismic risk, it is crucial to understand small-scale processes like strain and damage evolution during fault reactivation, and spatial-temporal dynamics which inform models predicting catastrophic events. We present results from fluid injection experiments that combine in-situ fast synchrotron x-ray microtomography with micro-seismic monitoring and control. We show how micro-seismicity and rock microstructure evolve during fluid-induced fault reactivation. Preliminary results show that dilation dominates. We quantify the fault-normal volumetric strain evolution – a key parameter that determines whether rupture continues to runaway failure. |