Particle Image Velocimetry (PIV) experimental equipment for reactive flow visualization in fractured porous media - M. Ahkami
Mission Statement
The Geothermal Energy & Geofluids group is endowed by the Werner Siemens Foundation and investigates reactive fluid (water, CO2, CxHy, N2) and (geothermal) energy (heat, pressure) transfer in the Earth’s crust employing computer simulations, laboratory experiments and field analyses to gain fundamental insights and to address a wide range of societal goals and concerns. ➞ Read More
GEG News
Geothermal energy has great potential, but drilling is expensive. That is why intensive research is being conducted into affordable drilling technologies. One such method is Directional Steel Shot Drilling (DSSD). A research team at ETH Zurich, together with international partners, has investigated this still-developing technology and assessed its potential for Switzerland. Special report: https://pubdb.bfe.admin.ch/en/publication/download/12285
18.08.2025
NEW Open Position
06.05.2024
Doctoral Examination Mohamed Ezzat
On May 6, 2024, Mohamed Ezzat has successfully defended his PhD thesis, entitled: “Numerical and Experimental Investigation of the Plasma-Pulse Geo-Drilling Technology“.
January 2024
Rock Mechanics Bulletin Excellent Paper 2022-2023 Award
A GEG paper receives the Rock Mechanics Bulletin Excellent Paper 2022-2023 Award. The paper is:
Li, Z., X. Ma, X.-Z. Kong, M.O. Saar, and D. Vogler, Permeability evolution during pressure-controlled shear slip in saw-cut and natural granite fractures, Rock Mechanics Bulletin, 2023. https://doi.org/10.1016/j.rockmb.2022.100027 [Download] [View Abstract]Fluid injection into rock masses is involved during various subsurface engineering applications. However, elevated fluid pressure, induced by injection, can trigger shear slip(s) of pre-existing natural fractures, resulting in changes of the rock mass permeability and thus injectivity. However, the mechanism of slip-induced permeability variation, particularly when subjected to multiple slips, is still not fully understood. In this study, we performed laboratory experiments to investigate the fracture permeability evolution induced by shear slip in both saw-cut and natural fractures with rough surfaces. Our experiments show that compared to saw-cut fractures, natural fractures show much small effective stress when the slips induced by triggering fluid pressures, likely due to the much rougher surface of the natural fractures. For natural fractures, we observed that a critical shear displacement value in the relationship between permeability and accumulative shear displacement: the permeability of natural fractures initially increases, followed by a permeability decrease after the accumulative shear displacement reaches a critical shear displacement value. For the saw-cut fractures, there is no consistent change in the measured permeability versus the accumulative shear displacement, but the first slip event often induces the largest shear displacement and associated permeability changes. The produced gouge material suggests that rock surface damage occurs during multiple slips, although, unfortunately, our experiments did not allow quantitatively continuous monitoring of fracture surface property changes. Thus, we attribute the slip-induced permeability evolution to the interplay between permeability reductions, due to damages of fracture asperities, and permeability enhancements, caused by shear dilation, depending on the scale of the shear displacement.
10.03.2023
Doctoral Examination Batmagnai Erdenechimeg
On March 3, 2023, Batmagnai Erdenechimeg has successfully defended his PhD thesis, entitled: “Magnetotelluric exploration of intermediate temperature geothermal systems and mineral resources in central Mongolia”.
December 2022, RWTH Aachen
Dr. Paromita Deb has been given the Dr. Karl-Heinrich Heitfeld Award for the best doctoral thesis in the Division of Earth Sciences and Geography.
Read more – link to RWTH Aachen
Dr. Paromita Deb has been given the Dr. Karl-Heinrich Heitfeld Award for the best doctoral thesis in the Division of Earth Sciences and Geography.
Read more – link to RWTH Aachen
On October 28, 2022, Isamu Naets has successfully defended his PhD thesis, entitled: “A pore scale investigation of fluid flow heterogeneity and solute transport in rough-walled fractures”.
The biggest geothermal event in Europe has ended. More than 1300 participants attended EGC2022. The next EGC2025 will be held in Zurich, from 6 to 10 October 2025, organized by Geothermie Schweiz and co-organized by ETH Zurich.
On September 16th, 2022, Po-Wei Huang has successfully defended his PhD thesis, entitled: “Reactive transport modeling at the pore scale and upscaling to the Darcy scale”.
Videos
CO2-Plume Geothermal (CPG) power plants combine geologic CO2 storage with geothermal energy extraction.
© Shannon Gilley
© Shannon Gilley
Inexhaustible resource of clean, renewable Geothermal Energy.
© ETH Zurich
© ETH Zurich
By 2050, geothermal energy can cover 25% of Switzerland’s heating needs in a CO2-neutral way.
© Daniel Stegmann
© Daniel Stegmann
Grimsel rock laboratory, safer drilling methods.
© 3sat nano
© 3sat nano
GEG Events
NEXT EVENT
07.05.2026 11:00-11:10 (local time)
From atomic defects to microcracks: Tracing damage with EPRNikita Bondarenko (contributed talk)
EGU26 General Assembly, Vienna, Austria
Newest GEG Papers
Refereed journal papers accepted the last 6 months
Underlined names are links to current or past GEG members
Plume-scale confinement controls the porous-to-free convection transition
Schwendener, D., J. Noir, J. Latt, C. Coreixas, and X.-Z. Kong, PNAS, (in press). [View Abstract]Convection in porous materials governs heat transport across scales ranging from planetary subsurface systems to engineered cooling devices. While
the onset of buoyancy-driven flow is well described by linear stability theory within a porous-continuum representation, the subsequent transition
from viscous, matrix-dominated convection toward inertia-influenced and ultimately bulk fluid-like plume convection has lacked a unified description.
Here we develop a confinement-based scaling framework that connects these flow states through a common scale-ratio perspective and quantitatively bridges classical porous convection with laterally confined Rayleigh–Bénard systems. Because random porous and fractured media do not admit an obvious static scale-ratio, we recover an effective confinement measure from the onset condition. This links permeability-based systems to the classical confinement framework and defines a characteristic pore length for natural convection. Comparing this pore length with the thermal boundary-layer thickness yields a dynamic criterion for the emergence of unconfined behaviour. Embedding experimental and numerical porous-convection datasets into a unified phase diagram of buoyant forcing
and static confinement reveals a systematic progression from viscous, drag-dominated heat transport to inertia-corrected flow and ultimately to plume-driven convection whose statistics approach those of unconfined fluids. The resulting framework delineates the limits of porous-continuum validity, clarifies when inertial corrections become relevant, and highlights the dynamical analogy between strongly confined porous flows and thin-gap Hele–Shaw configurations. By linking heat-transport scaling to static and dynamic length scales, the phase diagram provides a practical diagnostic for selecting appropriate governing equations across geophysical and engineered porous systems. (Paper accepted 2026-05-06) Geothermal energy potential and development in China
Jiang, L., Y. Li, S. Wang, K. Zhang, M. Sheng, X.-Z. Kong, J. Sheng, W. Liu, A. Hassanpouryouzband, A. Scheirer, and S. Farouq Ali, Sustainable Development of Renewable Energy, 2, pp. 415-440, 2026. https://doi.org/10.1016/B978-0-443-33600-3.00004-2 [Download] (Paper accepted 2026-04-03) The role of deep closed-loop advanced geothermal systems in the future net-zero Swiss power system
Van Liedekerke, A., M. Hefny, B. Gjorgiev, J. Garrison, J. Savelsberg, M.O. Saar, and G. Sansavini, Applied Energy, 2026. https://doi.org/10.1016/j.apenergy.2026.127761 [Download] [View Abstract]Deep closed-loop Advanced Geothermal Systems (AGS) are a carbon-free electricity generation technology that can support the transition to net-zero power systems by 2050. Unlike conventional geothermal power plants, AGS do not require permeable geologic formations and are thus largely geology-independent, providing distributed, flexible, and dispatchable electricity. Although their resource potential and technological characterization are widely researched, investment costs remain uncertain, and their integration into national power systems has hardly been studied. This paper analyzes the integration of AGS in the 2050 net-zero Swiss power system, focusing on their techno-economic aspects and their contribution to power system security. The generation potential of AGS is computed and aggregated at each transmission grid node, and the conditions under which AGS become an economically competitive generation technology from a cost-minimization perspective are investigated. The interactions of AGS with other generation and storage technologies, as well as with overall system operations, are assessed. Finally, the grid nodes at which AGS are optimally deployed are identified, and AGS’ impact on power system reliability is investigated. The results suggest that AGS become economically competitive in Switzerland at overnight investment costs below 21 ’
, 500 EUR/kWe when renewable generation subsidies are in place, and below 15,000 EUR/kWe when they are not. The deployment of AGS reduces the need for gas-fired power plants, battery storage, PV, and wind, and AGS installations can concentrate in areas of high demand, high demand-to-generation ratio, or frequent network congestions. Owing to their distributed and flexible nature, AGS also have the potential to enhance system reliability. (Paper accepted 2026-03-22) Natural Convection in Porous Media: The Role of Porosity and Conductivity Ratios in the Transition from Laminar to Inertial Convection
Schwendener, D., J. Noir, J. Latt, C. Coreixas, and X.-Z. Kong, Journal of Fluid Mechanics, 2025. https://doi.org/10.1017/jfm.2025.11014 [Download] [View Abstract]We study natural convection in porous media using a lattice Boltzmann method that recovers incompressible Navier--Stokes--Fourier dynamics. The porous structure consists of a staggered two-dimensional cylinder array with half-cylinders at the walls, forming a Darcy continuum at the domain scale. Hydrodynamic reference simulations reveal distinct flow regimes: laminar (Darcy), steady-inertial (Forchheimer), and vortex-shedding. We then analyse the effects of porosity and solid-to-fluid conductivity ratio ($k_s/k_f$) on natural convection. At low porosity ($\varphi = 33\%$), convection is highly sensitive to thermal coupling, particularly for insulating solids, whereas conductive matrices buffer this effect through lateral diffusion. Increasing porosity ($\varphi = 43\%$) smooths the transition as solid and fluid phases become more balanced. Across the explored range, two inertial regimes emerge governed by plume-scale confinement. The transition from Darcy to inertia-driven convection begins once the dynamics resemble the Forchheimer regime of the reference simulations. Based on our data, the system is governed by the confinement parameter $\Lambda$, which relates the plume-neck width, equivalent to the thermal boundary-layer thickness, to the pore scale: for $\Lambda \gtrsim 1$, the dynamics follow Forchheimer scaling, while for $\Lambda < 1/2$ they shift toward Rayleigh--Bénard behaviour. Comparison with experimental data shows the same trend: the nominal $Ra^*/Pr_p \approx 1$ criterion holds for $\Lambda > 10$, but weaker confinement causes earlier departure. Finally, we revise benchmark Nusselt numbers for a cavity with square obstacles, showing that the reference by \citet{merrikh2005natural} misrepresents trends due to improper normalisation. (Paper accepted 2025-11-19)