Plenary Sessions

Plenary Session

Panel discussion


Subject : Past, current and future development in coupled processes in fractured rock – Nuclear waste disposal research as the main driver for research and development on coupled processes in fractured rocks over the past 40 years



Jonny Rutqvist


Gilles Armand


Jens Birkholzer


Diego Mas Ivars


Haeryong Jung


Chin-Fu Tsang

(Uppsala University & LBNL)


Ju Wang

(Beijing Research Institute of Uranium Geology)

Hideaki Yasuhara

(Ehime University)




Plenary session for emerging scientists

Chang Kyung Won (Sandia National Labs)Profile
Kyung Won (K-Won) aims to understand the multiphysical coupling process in geological porous media, including fluid/heat flow, solute transport, and mechanical deformation. He started his academic career with engineering minds, a B.Sc. in geotechnical engineering and a M.S. in petroleum engineering, and then achieved a ph.D. in geological sciences. His multidisciplinary background will allow him be a smart bridge between geo-engineers and geo-scientists.


Title: Multiphysics-based assessment of geological hazards associated with subsurface energy activities Abstract

Recent surge of geological hazards, e.g., felt earthquakes, leakage of contaminants from storage formations, has been suspected (or considered) to be related with the steady growth of underground industrial activities including hydrocarbon/renewable energy exploration or underground construction of energy/waste storage. Significant research and governance efforts on mitigation and formation characterization are carried out to reduce socio-economic losses caused by geological hazards. However, traditional methods based on ground-based physical sensing have often failed to identify the presence of hidden/unknown features in depth that is almost detected only after catastrophic events as well as to understand the underlying physical mechanisms causing unexpected events (e.g., 2017 Mw5.5 Pohang earthquake). My research aims to advance physical understanding of multiphysical processes to assess the potential of geological hazards in the complex geological configuration prior to the subsurface energy activities by integrating fully coupled forward models with statistical and/or machine-learning techniques. Consequently, multiphysics-based characterization of underground features be a practical tool for the evaluation of geomechanical stability of underground structures or surface facilities built in/on the subsurface system.


Mengsu Hu (LBNL)Profile
Mengsu Hu is a Research Scientist at the Lawrence Berkeley National Laboratory (LBNL). She received a BEng in Civil Engineering in 2010 and a PhD in Geotechnical Engineering in 2016. Her research interests covers numerical modeling of coupled thermal-hydro-mechanical-chemical (THMC) processes in the energy geosciences, including: (1) modern computational methods development (such as extended finite volume method, numerical manifold method); (2) numerical modeling of microscale mechanical-chemical processes such as carbonate compaction, pressure solution, fracture alteration and fracture healing; (3) multi-scale, long-term analysis of THM processes in energy-geosciences applications such as nuclear waste disposal. More recently, she became interested in exploring ‘smart’ use of machine learning for energy geosciences applications. Mengsu has published ten papers in peer-reviewed journals as a lead author. Her PhD thesis won the No.1 Ranked PhD Thesis Award by the Chinese Society for Rock Mechanics and Engineering. She was the one of the six winners of 2019 Early Career LDRD awards at the Lawrence Berkeley National Laboratory.


Title: Modeling Coupled Processes in Fractured Media at Multiple Scales Abstract

Fractures at different scales have different geometric and physical features. Based on their distinct geometric features, we categorize fractures into three different scales: dominant, discrete fracture, and discontinuum asperity scales. In this talk, we present numerical models and results for coupled processes at each of these scales. For each scale we use different geometric representations of fractures and apply different governing equations and constitutive relationships. Our approaches are able to handle the computational challenges with accurate representation of intersections and shearing of fractures at the discrete fracture scale, and rigorously treat contacts along rough fracture surfaces at the discontinuum asperity scale. We present analyses involving nonlinear coupling in dominant fractures; closure/opening and shearing subjected to fluid injection and loading at the discrete fracture scale; and fracture alteration induced by loading, chemical reaction and pressure solution at the microscale. These examples demonstrate the capabilities for advancing fundamental understanding and optimizing energy recovery and storage in fractured media.


Takuya Ishibashi (AIST)Profile
Takuya Ishibashi is the senior researcher at Fukushima Renewable Energy institute, AIST (FREA). He was received the Ph.D. degree from Tohoku University in 2014 (top graduated). After completion of his degree, he joined Geothermal Energy Team, FREA. He worked in the Pennsylvania State University as a visiting scholar from 2014-2016. His research interests are in the areas of experimental rock mechanics and numerical simulations within single fracture/Discrete Fracture Network, with the application to subsurface energy extraction (Enhanced Geothermal Systems/deep geothermal energy).


Title: Static/Dynamic Characteristics of Permeability Structure within the Fractured Rocks Abstract

Permeability structure within fractured rock is of critically importance to assess potential and sustainability of subsurface energy resources. As a natural rock fracture consists of two opposing faces with rough surface geometry, heterogeneous void/pore space structure and resulting preferential paths are formed within rock fractures. Considering this characteristic, permeability structures within natural fractured rocks is likely to be more complex than what we have estimated by DFNs consisted of parallel plate fractures. To answer this hypothesis, I explore static permeability structures and associated fluid flows within DFNs where individual fractures are characterized by their scale-dependent heterogeneous void structures and discuss how preferential flow paths influence on hydraulic performances of fractured rocks. Moreover, returning to the basic, I would like to discuss dynamic change in fracture permeability caused by hydraulic shearing, i.e., whether “shear dilation mechanism” improves hydraulic performance under conditions targeted for EGS/deep geothermal developments, via novel laboratory experiments.


Peter K Kang (U. of Minnesota)Profile
I am a geoscientist whose research focuses on the physics of flow and reactive transport in porous and fractured media. My research group combines theory, high-performance numerical simulation, and visual laboratory experiments to understand how the coupling between multiple processes such as biogeochemical, thermal, and mechanical processes controls fluid flow and reactive transport in porous and fractured media ( I joined the Department of Earth and Environmental Science at the University of Minnesota as an Assistant Professor and a Gibson Chair of Hydrogeology in August 2018. I was a researcher at Korea Institute of Science and Technology (KIST) from 2015-2018, and was a postdoctoral associate in the Earth Resources Laboratory (ERL) at MIT before joining KIST. I received my MSc (2010) and PhD (2014) in Civil & Environmental Engineering at MIT, and obtained BSc of Civil, Urban & Geosystem engineering at Seoul National University in South Korea with summa cum laude in 2008.


Title: Predicting Fluid Flow and Reactive Transport in Fracture Media Across Scales (tentative) Abstract

Fluid flow and reactive transport in porous and fractured media control many subsurface processes and engineered systems. However, predicting flow and transport in porous media systems is challenging due to the multi-scale heterogeneity that is ubiquitous in subsurface systems. I will start my lecture by presenting various research projects that I have conducted to improve the predictability of fluid flow and mass transport in porous and fractured media. The examples span multiple scales: pore- to fracture- to field-scale (Figure). In addition to the multi-scale heterogeneity, a wide range of flow conditions, from laminar to turbulent flows, exert additional challenges. For example, vortex flows in fractures may exert dominant control over solute transport and reaction. While the existence of vortices in fracture flows is well known, the effects of vortices on transport and reaction remains poorly understood. My research group recently investigated the effects of vortices on transport and reaction in fracture flows. Our results point to a heretofore unrecognized link between vortex flows and reactive transport in fractured media.


Yusuke Mukuhira (Tohoku U.)Profile
Yusuke Mukuhira is now an Assistant Professor at the Institute of fluid science (ifs), Tohoku University, Japan. He received Ph.D. in March 2013 at Tohoku University. Then he extended his interest in geomechanics as JSPS postdoc at ifs, Tohoku University. Then, we worked as a JSPS Overseas Research Fellow in Earth Resource lab., MIT, before the current position. Most of his work focused on the investigation of the physical process of large induced seismicity. He integrated microseismic information with other geophysical information from borehole logging. With this original approach, he has discovered many of the physical processes related to large induced seismicity and behavior of the fluid flow. Recently, he is working for the development of the methodology for microseismicity analysis such as detection of low SNR seismicity and estimation of focal mechanisms, and the laboratory experiment to investigate the control factor of induced seismicity magnitude.


Title: The physics of induced seismicity discovered by geomechanics and microseismic analysis Abstract

Reservoir scale injection-induced seismicity is controlled by geomechanical parameters such as state of stress of the existing fracture and pore pressure. Microseismicity provides us the location of the shear failure. We also use it as an indicator of pore pressure migration. We want to go beyond the dots; so more than just microseismic information. In this talk, I will be presenting how we can maximize the information from microseismicity by combining the in-situ stress information. Our research fields offer a unique opportunity to deepen our knowledge of induced seismicity, seismology, fluid flow, and fracture characterization since we can study various geophysical data. I will share several of our challenges to investigate the behavior of pore pressure migration in the reservoir and its influence on injection-induced seismicity.


Jung-Wook Park (KIGAM)Profile
Jung-Wook Park is currently a senior researcher in the Korea Institute of Geoscience and Mineral Resources (KIGAM). She received PhD on rock mechanics and engineering at Seoul National University in 2011. Her main research interest is numerical modeling of coupled thermal-hydrological-mechanical (THM) processes in rock mass and fractures, with applications in rock engineering. She has been involved in the international DECOVALEX project (DECOVAEX-2019 and DECOVAEX-2023) since 2016. She published 22 papers in peer-reviewed journals as a lead author. More recently, her research focuses on thermally-induced failure process in brittle rock (TM) and geomechanical stability in CO2 sequestration (THM).


Title: Continuum and discontinuum approaches for modeling thermal, hydrological and mechanical processes in rock Abstract

With the rapid progress of computer technology, many attempts have been made to demonstrate the thermal (T), hydrological (H) and mechanical (M) processes in rock using numerical models, such as the finite element method, finite difference method, boundary element method and discrete element method. The choice of the modeling approach is dependent upon the scale of interest, conditions of rock mass and discontinuities, required properties of the associated model and purpose of the analysis. We have simulated various rock mechanics and engineering problems using continuum and discontiuum approaches. In this presentation, we briefly introduce the respective modeling approaches and results. The studies cover the grain-based distinct element modeling of failure processes in brittle rock and joint at the microscale (M and TM), feasibility and stability analyses for rock cavern energy storage system and geological CO2 sequestration (T and THM), and modeling of fluid injection-induced fault reactivation at Mont Terri Rock Laboratory, Switzerland (HM).


Fengshou (Frank) Zhang (Tongji U.)Profile
Fengshou Zhang is a professor in the Department of Geotechnical Engineering at Tongji University, Shanghai, China. He obtained his PhD from the Georgia Institute of Technology in 2012, after that he worked in Itasca Consulting Group for a few years as a geomechanics engineer providing consulting services to the oil and gas industries in USA. His research focuses on multi-scale and multi-physics coupling process in the deep earth engineering, with applications to unconventional hydraulic fracturing, transport in fractures, fault stability, sanding and so on. He is a ARMA Future Leader Class of 2015 and Early Career Keynote Speaker in 2018. He is also a member of ISRM commission of Petroleum Geomechanics and commission of Coupled Thermal-Hydro-Mechanical-Chemical Processes in Fractured Rock. He published 80+ journal and conference papers and currently serves an associate editor of SPE Journal.


Title: Modeling Hydraulic Fracturing Complexity in Naturally Fractured Rock Masses: Challenge and Opportunity Abstract

Naturally fractured reservoir rock in-situ is one of the most complex geomaterials. Uncertainties such as material inhomogeneity and discontinuities at various length scales make the propagation of hydraulic fracture in such a medium “enigmatic”. Advanced numerical modeling provides a powerful tool to analyze the complex fracturing process, assess the extent of various uncertainties and provide advice to practical fracturing designs. This talk will first give a comprehensive review of some recent advances on multi-scale numerical modeling of hydraulic fracturing in naturally fractured rock masses, with the topics covering near wellbore fracture initiation, hydraulic fracture/natural fracture interaction, complex fracturing and microseismic geomechanics, refracturing and in-fill well fracturing, injection induced seismicity and fault activation and so on. Then the challenge of applying numerical modeling to the interpretation of field observations of hydraulic fracturing will be discussed.


Zhihong Zhao (Tsinghua U.)Profile
Zhihong Zhao is currently an associate professor in the Department of Civil Engineering at Tsinghua University, China. He obtained PhD on rock mechanics at Royal Institute Technology (KTH), Sweden, in 2011. He serves as editorial board members for Rock Mechanics and Rock Engineering, Computers and Geotechnics, and Geosystem Engineering, and commission members of ISRM Commission on Coupled Thermal-Hydro-Mechanical-Chemical Processes in Fractured Rock and ISRM Commission on Radioactive Waste Disposal. His main research interest is coupled thermal-hydrological-mechanical- chemical (THMC) processes in fractured rocks, with principal applications in deep underground engineering such as enhanced geothermal systems, underground nuclear waste repositories, as well as subsea tunnels. He has published about 50 peer-reviewed journal articles and 1 book chapter, which have been cited by over 800 times according to Google Scholar.


Title: Coupled stress/damage-flow-heat/solute transport processes in rock fractures Abstract

An understanding of the mechanical, flow, and heat and solute transport behaviors in single rock fractures is fundamental for accurately predicting the coupled THMC processes in fractured rock masses. On the one hand, the induced deformation and damage can significantly affect the permeability and transport properties of fractures through altering fracture apertures or producing gouges; on the other hand, groundwater, temperature, and other environmental factors may also cause degradation of fractures due to microcracking, lubrication, and chemical reactions. Two themes including effects of stress and temperature on fracture permeability and transport properties, and effects of temperature and water-rock interactions on fracture shear properties are focused in this presentation. The implication and potential application of the advanced understanding of coupled THMC processes in rock fractures for geo-energy engineering are discussed.
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