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October 2015 - November 2016
Publications
Publications (313)
In a high‐pressure injection fault activation experiment conducted at the Mont Terri underground research laboratory in Switzerland, the transmissivity of the Opalinus Clay fault significantly increased due to opening and shearing. The fluid injection, spanning a few hours, generated a 10 m radius fault activation patch. Subsequent pressure pulse t...
The potential for activating faults associated with geologic carbon sequestration is an issue of concern both related to induced seismicity and CO2 leakage. Faults are usually simplified (e.g., single, planar and homogeneous) in numerical simulations for the sake of computational efficiency. However, such simplifications might significantly impact...
The long-lived radiotoxicity of the high-level radioactive waste generated by nuclear power plants requires safe isolation from the biosphere for many hundreds of thousands of years. An international consensus has emerged that such isolation can best be provided by disposal in mined geologic repositories, a strategy that today is pursued by most co...
Shearing of fractures and faults is important because it can result in permeability change or even induce seismicity—both are keys for efficient and safe energy recovery and storage in Earth systems. Quantitative analysis of shearing of intersecting fractures and faults is challenging because it can involve dynamic frictional contacts that are comp...
We conducted a time‐lapse seismic experiment utilizing automated active seismic source and sensor arrays to monitor a reactivated fault within the Opalinus clay formation at the Mont Terri Rock Laboratory (Switzerland), an analog caprock for geologic carbon storage. A series of six brine injections were conducted into the so‐called Main Fault to re...
Large-scale thermal energy storage is essential for the successful implementation of smart district cooling systems that use significant amounts of renewable energy. Ice storage tanks have been deployed for decades to reduce the on-peak electrical demand and to shift energy use to off-peak hours. Most of these systems, however, are designed for dai...
Bentonite buffer in a geological repository will be simultaneously heated from decaying radioactive waste and hydrated from the surrounding host rock, triggering complex and coupled THMC (thermal–hydrological–mechanical–chemical) processes. Understanding the THMC behavior of bentonite-based engineered barrier system (EBS) is key to the evaluation a...
Pressurization of natural faults as a result of repository-induced effects can lead to their reactivation and permeability generation in case such features are present near disposal tunnels. Potential driving forces for such pressurization are the temperature increase caused by heat-producing high-level radioactive waste and the generation of hydro...
More than a decade ago, the United States disposal program discontinued all research activities focused on the unsaturated fractured tuff formation at Yucca Mountain as the geologic disposal site for spent fuel and high-level radioactive waste. A new research and development (R&D) program was initiated to provide a sound technical basis for alterna...
Fault slip induced by fluid perturbation in shale formations may only lead to as sparse seismicity. However, fault slip may strongly impact the integrity of shale formations that serve as caprocks for geological reservoirs holding buoyant fluids such as CO2, natural gas, or hydrogen. A better understanding of the fluid reactivation processes of fau...
The behavior of heated bentonite buffer is critical for the security and long-term performance of a geological
repository for high-level radioactive waste (HLW). While laboratory column experiments have been conducted to
investigate compacted bentonite and coupled THMC (thermal-hydro-mechanical and chemical) processes for a
moderate temperature ran...
The DECOVALEX Project is an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. DECOVALEX stands for “DEvelopment of COupled Models and VALidation against EXperiments”. The creation of this international initiative, now running for almo...
This presentation gives on overview of the complex thermo-hydro-mechanical-chemical (THMC) processes occurring during the disposal of heat-producing high-level radioactive waste in geologic repositories. A specific focus is on the role of compacted bentonite, which is commonly used as an engineered backfill material for emplacement tunnels because...
Observations on tens-of-meter scale experiments of fault activation by fluid injection conducted in shales allow exploring how aseismic and seismic events may jeopardize the integrity of a sealing caprock overlying a CO2 sequestration reservoir. We contrast the behavior of shale faults with another set of experiments conducted in carbonates. Signif...
The present work investigates mechanisms of permeability impairment as a result of low-salinity fluid injection into brine-saturated porous media containing dispersible clays. We present a computational fluid dynamics model at the pore-scale to simulate detachment, migration and straining of fine particles in porous media. The model uses an immerse...
Migration of clay fines can be a concern when less saline fluids are injected into brine‐saturated sandstone formations containing clays. If the salinity near fluid injection wells decreases below a critical value, the clay fines near the injection may detach, start migrating, and finally clog the pores at some distance further away. This effect ca...
The coupled Thermo-Hydro-Mechanical (THM) behavior of the Callovo-Oxfordian claystone (COx) is of great importance for the design and safety calculations of the high-level radioactive waste disposal project in this potential host rock in France. The heat emitted by the waste causes a pore pressure increase within the surrounding rock essentially du...
The ability to predict multiphase fluid transport in nanoporous rocks such as shales is critical for many geoscience applications, for example unconventional hydrocarbon production, geologic carbon sequestration, and nuclear waste disposal. When the pore sizes approach nanoscales, the impact of the molecular interaction forces between fluids and so...
Experimental studies show that compacted bentonite used as a backfill material for nuclear waste repository experiences strong coupling between chemical and mechanical processes. In this paper, we use a dual-structure expansive soil model, referred to as the Barcelona Expansive Model (BExM), to predict the behavior of bentonite buffer in subsurface...
This paper is devoted to the study of the Thermo-Hydro-Mechanical (THM) responses of a porous rock with low permeability under thermal loading in the context of deep geological disposal of radioactive waste. To this aim, numerical simulations of a benchmark exercise of a hypothetical high-level radioactive waste (HLW) repository were performed. Thi...
Reservoir integrity stewardship accompanying carbon capture and sequestration considers reservoir fluid extraction and re-injection as a risk-mitigating method against reservoir overpressuring that could lead to caprock damage and ensuing CO2 leakage. Crosswell electromagnetics offers a technically viable monitoring method with the spatial volume c...
A coupled multiphase fluid flow and discrete fracturing model is applied to simulate bench-scale gas migration experiments on compacted bentonite. The numerical modeling is based on the linking of the multiphase fluid flow simulator TOUGH2 with a Rigid-Body-Spring Network model, which enables a discrete (lattice) representation of elasticity and in...
We present results from an international model comparison study involving a series of controlled fault activation experiments in Opalinus Clay at the Mont Terri Laboratory, Switzerland. The fault activation experiments were conducted in situ by water injection at variable pressure from boreholes targeting different parts of the Main Fault crossing...
We present coupled Thermo–Hydro–Mechanical (THM) modeling of geologic nuclear waste disposal in argillaceous claystone, focusing on thermally-induced pressure changes and the potential for such pressure changes to induce hydro-fracturing. To investigate this possibility, we first conduct a three-dimensional repository scale model, with host rock pr...
Executive summary of the results from the DECOVALEX-2019 project
We apply thermoporoelasticity and a sequentially coupling technique for modeling thermally-driven coupled Thermo-Hydro-Mechanical (THM) processes in tight claystone. A THM benchmark case with a corresponding analytic solution for thermoporoelasticity under a constant heat loading verifies the model. Thereafter, two in situ heating experiments are s...
Hydrofracturing stress measurements in fractured and anisotropic shales are notoriously difficult, because opening of existing geological features tends to prevent the creation of a pure hydraulic fracture perpendicular to the least compressive principal stress. Here we show how adding 3-D borehole-displacement measurements while conducting the hyd...
This paper presents modeling of mechanical anisotropy in argillaceous rocks using an irregular lattice modeling approach, namely the rigid-body-spring network. To represent the mechanical anisotropy, new schemes are implemented in the modeling framework. The directionality of elastic deformation is resolved by modifying the element formulation with...
We observed rupture growth caused by controlled fluid injections at 340‐m depth within a fault zone in the low‐permeability Opalinus Clay in the Mont Terri Underground Research Laboratory (Switzerland). The rupture mechanisms were evaluated using measurements of the three‐component borehole wall displacements and fluid pressure in two sections of t...
In most conceptual models of dissolution trapping of CO2, it is assumed that mixing of dissolved supercritical CO2 and formation brine occurs through density-driven convection. In our previous modeling study, we showed that the presence of continuous low-permeability shale layers in the formations causes convective shutdown through disruption of fi...
The hydration of a bentonite barrier in the early stage of a geologic nuclear waste repository with a bentonite buffer is a critical issue for its long-term performance and safety because bentonite might be permanently altered and subsequently affect the function of bentonite barrier. Large scale in situ testing integrated with modeling analysis is...
This paper provides an overview of an international research collaboration for advancing the understanding and modeling of coupled thermo-hydro-mechanical-chemical (THMC) processes in geological systems. The creation of the international DECOVALEX Project, now running for over 25 years, was initially motivated by the recognition that prediction of...
Industrial-scale injection of CO2 into the subsurface increases the fluid pressure in the reservoir, which if not properly controlled can potentially lead to geomechanical damage (i.e., fracturing of the caprock or reactivation of faults) and subsequent CO2 leakage. Brine extraction is one approach for managing formation pressure, effective stress,...
Geologic carbon sequestration (GCS) is the process of injecting CO2 into deep subsurface rock formations such as into depleted oil and gas reservoirs or deep saline aquifers for long‐term storage. Over the last decade, a number of field, laboratory, and modeling studies have been undertaken to assess the feasibility and safety of CO2 geologic stora...
Fluid injections into the deep subsurface can, at times, generate earthquakes, but often, they only produce aseismic deformations. Here we analyze the influence of fault hydromechanical properties on the growth of injection-induced aseismic slip. Using hydromechanical modeling, we show how permeability enhancement in addition to the background stre...
This paper presents numerical modeling of coupled thermal, hydraulic and mechanical processes in rock salt and crushed salt considering halite solubility constraints. The TOUGH-FLAC simulator is used, with a recently enhanced Equation-Of-State module that includes the thermodynamic properties of aqueous fluids of variable salinity. Laboratory and f...
Understanding the main mechanisms affecting long-term migration and redistribution of injected CO2 in geological carbon storage is needed for developing predictive models to assess environmental risks and designing monitoring schemes. Preparation of a postinjection site care plan is required for CO2 injection wells, including monitoring of pressure...
We studied the relation between rupture and changes in permeability within a fault zone intersecting the Opalinus Clay formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). A series of water injection experiments was performed in a borehole straddle interval set within the damage zone of the main fault. A three-c...
For the deep geological disposal of high-level radioactive waste in argillaceous rocks, the heat production of the waste is an important driver for thermal–hydraulic-mechanical (THM)-coupled processes. These THM processes influence the properties and conditions of the near field that in many repository designs contains bentonite as a clay buffer. O...
The effects of land use and land cover (LULC) change on environmental systems across the land surface's “critical zone” are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an integrated hydrologic model, overland flow generation is quantified for both present day and forest...
Geologic repositories for radioactive waste are designed as multi-barrier disposal systems that perform a number of functions including the long-term isolation and containment of waste from the human environment, and the attenuation of radionuclides released to the subsurface. The rock laboratory at Mont Terri (canton Jura, Switzerland) in the Opal...
The Special Issue “Water and Solute Transport in Vadose Zone” in the journal Water is dedicated to the memory of Dr. Gudmundur “Bo” Bodvarsson, the former director of the Earth Sciences Division of Lawrence Berkeley National Laboratory (http://eesa.lbl.gov/profiles/gudmundur-bo-sbodvarsson/).[...]
There are two types of analytical solutions of temperature/concentration in and heat/mass transfer through boundaries of regularly shaped 1-D, 2-D, and 3-D blocks. These infinite-series solutions with either error functions or exponentials exhibit highly irregular but complementary convergence at different dimensionless times, td. In this paper, ap...
Carbon capture and storage (CCS) in geological formations is considered as a promising option that could limit CO2 emissions from human activities into the atmosphere. However, there is a risk that pressure buildup inside the storage formation can induce slip along preexisting faults and create seismic event felt by the population. To prevent this...
Subsurface manipulations such as those expected from the disposal of heat-emanating radioactive waste in deep repositories can induce strongly coupled Thermal (T), hydrological (H), mechanical (M) and chemical (C) processes. Adequate coupled THMC models are highly desirable or even indispensable for performance assessment of such repositories, for...
The Callovo-Oxfordian claystone (COx) is considered as a potential geological formation to host an industrial radioactive waste repository in France. A deep understanding of the thermo-hydro-mechanical (THM) behaviour of the COx is a key issue for the design of the repository and the safety calculations of the project. From this perspective, an imp...
We studied the elastic properties of a fault zone intersecting the Opalinus Clay formation at 300 m depth in the Mont Terri Underground Research Laboratory (Switzerland). Four controlled water injection experiments were performed in borehole straddle intervals set at successive locations across the fault zone. A three-component displacement sensor,...
For dissolution trapping, the spatial variability of the geologic properties of naturally complex storage formations can significantly impact flow patterns and storage mechanisms of dissolved CO2. The significance of diffusive mixing that occurs in low permeability layers embedded between relatively higher permeability materials was highlighted by...
A probabilistic methodology to generate “risk maps” for determining the spatial extent and associated probability of groundwater leakage risk at Geologic Carbon Storage (GCS) sites was recently developed and is tested for well permeability distribution sensitivity here. Although the risk map methodology is general and may be used to assess leakage...
We conducted fluid injection tests in four packed-off borehole intervals across the Mont Terri clay-rich fault zone which is an analogue to a minor fault that would hardly be detectable from surface seismic surveys during the initial design of a sequestration site. While pressurizing the intervals at maximum injection pressures of 5 to 6.3 MPa, we...
Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in...
This paper presents coupled hydro-mechanical modeling of hydraulic fracturing processes in complex fractured media using a discrete fracture network (DFN) approach. The individual physical processes in the fracture propagation are represented by separate program modules: the TOUGH2 code for multiphase flow and mass transport based on the finite vol...
The impact of geologic heterogeneity on capillary trapping of supercritical CO2 (scCO2) has been recognized and appraised through laboratory experimentation and modeling. However, how different injection strategies can be optimized to improve capillary trapping has not received adequate attention. We present a study based on stochastic analysis to...
The risks to potable aquifers due to brine leakage through plugged and abandoned (P&A) wells is highly uncertain and a potentially significant contributor to the risk profile in Geologic Carbon Storage (GCS). This uncertainty stems from the unknown location of wells and the large variance of P&A wellbore permeability, making the spatial assessment...
Geologic repositories for radioactive waste are designed as multi-barrier disposal systems that perform a number of functions including the long-term isolation and containment of waste from the human environment, and the attenuation of radionuclides released to the subsurface. The rock laboratory at Mont Terri (canton Jura, Switzerland) in the Opal...
Analytical solutions with infinite exponential series are available to calculate the rate of diffusive transfer between low-permeability blocks and high-permeability zones in the subsurface. Truncation of these series is often employed by neglecting the early-time regime. In this paper, we present unified-form approximate solutions in which the ear...
This study involves the development of the auxiliary stress approach for producing elastically-homogeneous lattice models of damage in geomaterials. The lattice models are based on random, three-dimensional assemblages of rigid-body-spring elements. Unlike conventional lattice or particle models, the elastic constants of a material (e.g., Young’s m...
The role of capillary forces during buoyant migration of CO2 is critical towards plume immobilization within the post-injection phase of a geological carbon sequestration operation. However, the inherent heterogeneity of the subsurface makes it very challenging to evaluate the effects of capillary forces on the storage capacity of these formations...
Incorporating hysteresis into models is important to accurately capture the two phase flow behavior when porous media systems undergo cycles of drainage and imbibition such as in the cases of injection and post-injection redistribution of CO2 during geological CO2 storage (GCS). In the traditional model of two-phase flow, existing constitutive mode...
Process understanding and parameter identification using numerical methods based on experimental findings are key aspects of the international cooperative project DECOVALEX (DEvelopment of COupled models and their VALidation against Experiments http://www.decovalex.org). Comparing the long-term predictions from numerical models against experimental...
Supplementary figures showing porosity distributions, photographic sequences, and temporal evolution of plume dimensions.
Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at Åre, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet...
The role of capillary forces during buoyant migration of CO2 is critical towards plume immobilization during post-injection of geological carbon sequestration. However, the inherent heterogeneity of most candidate reservoirs makes it very challenging to evaluate the effects of capillary forces on the storage capacity of these formations and to asse...
The TOUGH-FLAC simulator for coupled thermal-hydraulic-mechanical processes modeling has been extended to the finite strain framework. In the approach selected, this extension has required modifications to the flow simulator (TOUGH2) and to the coupling scheme between the geomechanics and the flow sub-problems. In TOUGH2, the mass and energy balanc...
One of the risks that CO2 geological sequestration imposes on the environment is the impact of potential CO2/brine leakage on shallow groundwater. The reliability of reactive transport models predicting the response of groundwater to CO2 leakage depends on a thorough understanding of the relevant chemical processes and key parameters affecting diss...
Carbon capture and storage (CCS) in geologic formations has been recognized as a promising option for reducing carbon dioxide (CO2) emissions from large stationary sources. However, the pressure buildup inside the storage formation can potentially induce slip along preexisting faults, which could lead to felt seismic ground motion and also provide...
The Thermal Simulation for Drift Emplacement heater test is modeled using two simulators for coupled thermal-hydraulic-mechanical processes. Results from the two simulators are in very good agreement. The comparison between measurements and numerical results is also very satisfactory, regarding temperature, drift closure and rock deformation. Conce...
Benchmarking has been recognized as an efficient tool for model validation as well as scientific collaboration. Several workshop series have been established to foster the benchmarking idea: setting up test cases with increasing complexity for method development and code comparison. In addition to representing model complexity, one of the key effor...
Numerical modeling is essential to support natural resource management and environmental policy-making. In the context of CO2 geological sequestration, these models are indispensible parts of risk assessment tools. However, because of increasing complexity, modern numerical models require a great computational effort, which in some cases may be inf...
Understanding fault reactivation is critical in geologic wastewater disposal, hydraulic fracturing, and CO 2 sequestration because it may result in enhanced fault permeability, potentially inducing fluid leakage from the injection zone through overlying caprock and eventually triggering shallow seismic events. Here we show preliminary results from...
Expansive soils are suitable as backfill and buffer materials in engineered barrier systems to isolate heat-generating nuclear waste in deep geological formations. The canisters containing nuclear waste would be placed in tunnels excavated at a depth of several hundred meters. The expansive soil should provide enough swelling capacity to support th...
Rock salt is a potential medium for the underground disposal of nuclear waste because it has several assets, in particular its ability to creep and heal fractures and its water and gas tightness in the undisturbed state. In this research, we focus on disposal of heat-generating nuclear waste (such as spent fuel) and we consider a generic salt repos...
Several numerical studies have demonstrated that the heterogeneous nature of typical sedimentary formations can favorably dampen the accumulation of mobile CO2 phase underneath the caprock. Core flooding experiments have also shown that contrasts in capillary entry pressure can lead to buildup of nonwetting fluid phase (NWP) at interfaces between f...
Large-scale pressure increases resulting from carbon dioxide (CO2) injection in the subsurface can potentially impact caprock integrity, induce reactivation of critically stressed faults, and drive CO2 or brine through conductive features into shallow groundwater. Pressure management involving the extraction of native fluids from storage formations...
Lattice models provide discontinuous approximations of the displacement field over the computational domain, which facilitates the modeling of fracture and other discontinuous phenomena. By discretizing the domain with two-node elements, however, ordinary lattice models cannot simulate the Poisson effect in a local (intra-element) sense, which is p...
One of the most important design variables for a geological nuclear waste repository is the temperature limit up to which the engineered barrier system (EBS) and the natural geologic environment can be exposed. Up to now, almost all design concepts that involve bentonite-backfilled emplacement tunnels have chosen a maximum allowable temperature of...
