Delayed Induced Seismicity in a THM Framework: Upscaling Application to Deep Geothermal Fractured Reservoirs

14/10/2024

Doctoral Candidate: Khashayar Khezri

Supervisor: Emad Jahangir, Dominique Bruel & Murad Abuaisha

Host institution: Mines Paris – PSL

Output type: literature review and summary research topic

Research questions:

  1. How can we develop a robust coupled Thermo-Hydro-Mechanical (THM) model to effectively study delayed induced seismicity in enhanced geothermal systems?
  2. How does temperature evolution in the reservoir interact with stress distribution and pore pressure within the rock matrix and fractures?
  3. In what ways do the combined effects of pressure and temperature diffusivity across different fracture networks contribute to the  occurrence of delayed induced seismicity?
  4. What strategies can be implemented to minimize the risk of delayed induced seismicity in geothermal systems?

Brief Summary of Research:

Geothermal energy stored in deep hot dry rocks (HDR) has significant potential for electricity and heat generation through enhanced geothermal systems (EGS). The World Geothermal Congress 2020 (WGC2020) reported an increase in direct geothermal energy utilization, now spanning 88 countries, up from 82 in 2015. By 2050, geothermal technology could help eliminate over 1 billion tons of CO2, supplying 3% of global electricity and 5% of heat demand.

Traditionally, generating large amounts of electricity from geothermal resources involves extracting fluids from large  hydrothermal reservoirs, which can be depleted over time. EGS addresses this limitation by creating artificial reservoirs from non-fractured, low-permeability HDR. This involves drilling wells, creating fractures for fluid circulation, and using heated fluid for electricity generation, thereby expanding geothermal energy use globally.

Injecting fluids at high pressures alters mechanical stresses, potentially triggering earthquakes along pre-existing faults or new created fractures (induced seismicity). Additionally, temperature changes cause rock deformation and stress variations, influencing fluid movement and heat transfer in a dynamic feedback system known as Thermo-Hydro-Mechanical (THM) coupling. A thorough understanding of THM coupling and fracture networks is crucial for optimizing EGS design.

A significant unresolved issue is post-injection or delayed induced seismicity, referring to seismic events that occur after fluid injection, often with a time lag. These events are typically more severe than those during injection and hard to control, highlighting knowledge gaps in this research field. Delayed seismicity arises from various mechanisms, but the impact of thermal stresses from injecting cold water into hot dry rock remains unclear. The interaction between conduction through the rock and convection through fractures complicates this, making thermal effects highly dependent on the fracture network.

This research project aims to improve understanding of pressure and temperature diffusivity in HDR and their interactions with existing stress fields in fractured rock. Robust THM models will be developed to analyze temperature and pressure diffusivity across varying initial stress states and realistic fracture network. The ultimate  goal is to understand how these factors influence the number and magnitude of delayed seismic events, enabling more accurate predictions and better control of induced seismicity for the safe and efficient exploitation of deep geothermal resources.

Key References:

Buijze, L., van Bijsterveldt, L., Cremer, H., Paap, B., Veldkamp, H., Wassing, B. B., … & Jaarsma, B. (2019). Review of induced seismicity in geothermal systems worldwide and implications for geothermal systems in the Netherlands. Netherlands Journal of Geosciences, 98, e13.

De Barros, L., Cappa, F., Guglielmi, Y., Duboeuf, L., & Grasso, J. (2019). Energy of injection-induced seismicity predicted from in-situ experiments. Scientific reports, 9(1), 4999.

De Simone, S., Carrera, J., & Vilarrasa, V. (2017). Superposition approach to understand triggering mechanisms of post-injection induced seismicity. Geothermics, 70, 85-97.

De Simone, S., Vilarrasa, V., Carrera, J., Alcolea, A., & Meier, P. (2013). Thermal coupling may control mechanical stability of geothermal reservoirs during cold water injection. Physics and Chemistry of the Earth, Parts A/B/C, 64, 117-126.

Gan, Q., & Lei, Q. (2020). Induced fault reactivation by thermal perturbation in enhanced geothermal systems. Geothermics, 86, 101814.

Jeanne, P., Rutqvist, J., Dobson, P. F., Walters, M., Hartline, C., & Garcia, J. (2014). The impacts of mechanical stress transfers caused by hydromechanical and thermal processes on fault stability during hydraulic stimulation in a deep geothermal reservoir. International Journal of Rock Mechanics and Mining Sciences, 72, 149-163.

Kim, K. I., Yoo, H., Park, S., Yim, J., Xie, L., Min, K. B., & Rutqvist, J. (2022). Induced and triggered seismicity by immediate stress transfer and delayed fluid migration in a fractured geothermal reservoir at Pohang, South Korea. International Journal of Rock Mechanics and Mining Sciences, 153, 105098.

Lei, Q., Doonechaly, N. G., & Tsang, C. F. (2021). Modelling fluid injection-induced fracture activation, damage growth, seismicity occurrence and connectivity change in naturally fractured rocks. International Journal of Rock Mechanics and Mining Sciences, 138, 104598.

Ma, Y., Xia, K., Lei, Q., Zhang, C., Elsworth, D., Gan, Q., & Yuan, (2024). Roles of heat and stress transfer in triggering fault instability in conjugate faulted reservoirs. International Journal of Rock Mechanics and Mining Sciences, 180, 105819.

Olasolo, P., Juárez, M. C., Morales, M. P., & Liarte, I. A. (2016). Enhanced geothermal systems (EGS): A review. Renewable and  Sustainable Energy Reviews, 56, 133-144.

Soltani, M., Kashkooli, F. M., Souri, M., Rafiei, B., Jabarifar, M., Gharali, K., & Nathwani, J. S. (2021). Environmental, economic, and social impacts of geothermal energy systems. Renewable and Sustainable Energy Reviews, 140, 110750.

Sun, Z., Jiang, C., Wang, X., Lei, Q., & Jourde, H. (2020). Joint influence of in-situ stress and fracture network geometry on heat transfer in fractured geothermal reservoirs. International Journal of Heat and Mass Transfer, 149, 119216.