The stress field at depth is a relevant parameter for the design of subsurface constructions and ... more The stress field at depth is a relevant parameter for the design of subsurface constructions and reservoir management. Yet the distortion of the regional stress field due to local-scale features such as sedimentary and tectonic structures or topography is often poorly constrained. We conduct a stress sensitivity analysis using 3-D numerical geomechanical modelling with an elasto-plastic material law to explore the impact of such site-specific features on the stress field in a sedimentary sequence of the Swiss Alpine foreland. The model's dimensions are 14 × 14 × 3 km 3 and it contains 10 units with different mechanical properties, intersected by two regional fault zones. An initial stress state is established involving a semi-empirical relationship between the ratio of horizontal to vertical stress and the overconsolidation ratio of argillaceous sediments. The model results indicate that local topography can affect the stress field significantly to depths greater than the relief contrasts at the surface, especially in conjunction with horizontal tectonic loading. The complexity and frictional properties of faults are also relevant. The greatest variability of the stress field arises across the different sedimentary units. Stress magnitudes and stress anisotropy are much larger in stiffer formations such as massive limestones than in softer argillaceous formations. The stiffer formations essentially carry the load of the far-field forces and are therefore more sensitive to changes of the boundary conditions. This general characteristic of stress distribution in the stiff and soft formations is broadly maintained also with progressive loading towards the plastic limit. The stress field in argillaceous sediments within a stack of formations with strongly contrasting mechanical properties like in the Alpine foreland appears to be relatively insensitive to changes in the tectonic boundary conditions and is largely controlled by the maximum stiffness contrast with respect to the load-bearing formations.
Three parameters control the development of secondary sub-seismic fractures: Material properties,... more Three parameters control the development of secondary sub-seismic fractures: Material properties, the fault displacement and its morphology. We demonstrate how restoring seismic faults with three dimensional geometrical kinematic modelling can generate information about the intensity and orientation of the fractures around the fault.
Core samples from the Opalinus Clay, an indurated clay formation of Jurassic age, were subjected ... more Core samples from the Opalinus Clay, an indurated clay formation of Jurassic age, were subjected to comprehensive microstructural investigations: transmission electron microscopy, focused ion beam nanotomography, and X-ray computed tomography. Digital representations of the microstructure were derived from the tomographic images by segmentation and 3D reconstruction of the geomaterial on a grid of regular voxel elements with a typical edge length of as little as 10 nm and a maximum size on the order of 1000 3 voxels. Pertinent geotechnical properties were derived on the microscopic scale using state-of-the-art image-processing procedures. The results were compared with results from geotechnical laboratory characterization methods such as mercury intrusion porosimetry, nitrogen adsorption/desorption measurements, grain-size analysis, X-ray diffraction, and triaxial testing. Good agreement was achieved between microscopic and macroscopic characterization methods. The macroscopic (poro-elastic) deformation behavior of the Opalinus Clay was also reproduced reasonably well by geomechanical modeling on the microscopic scale. The cross-anisotropic stiffness of the rock mass is thus caused partly by preferred orientation of pore structures along bedding. In addition, new insight was gained with regard to the role of small mesopores (2-10 nm), essentially controlling the macroscopic deformation behavior of indurated clays.
In the development of deep geological repositories (DGRs), performance assessment modeling is use... more In the development of deep geological repositories (DGRs), performance assessment modeling is used to evaluate the integrity and performance of the engineered and geological barriers for thousands or millions of years of evolution of the disposal system. To evaluate the suitability of a site for a DGR, geoscientific data from dedicated site investigation programs are integrated into site-specific assessments. This paper presents the development and implementation of a modeling workflow aimed at comparing three potential siting areas for a DGR in Switzerland from the viewpoint of long-term safety and technical feasibility. The workflow follows the guidelines of the national regulator addressing safety relevant criteria such as the barrier efficiency of the host rock and its mechanical and chemical integrity in response to repository-induced influences and the long-term stability of the repository site over geological scales. In the regulatory requirements, the role of parametric, con...
Physics And Chemistry Of The Earth, Parts A/b/c, 2008
ABSTRACT In studies related to deep geological disposal of radioactive waste, it is current pract... more ABSTRACT In studies related to deep geological disposal of radioactive waste, it is current practice to transfer external information (e.g. from other sites, from underground rock laboratories or from natural analogues) to safety cases for specific projects. Transferable information most commonly includes parameters, investigation techniques, process understanding, conceptual models and high-level conclusions on system behaviour. Prior to transfer, the basis of transferability needs to be established. In argillaceous rocks, the most relevant common feature is the microstructure of the rocks, essentially determined by the properties of clay–minerals. Examples are shown from the Swiss and French programmes how transfer of information was handled and justified. These examples illustrate how transferability depends on the stage of development of a repository safety case and highlight the need for adequate system understanding at all sites involved to support the transfer.
Deep geological disposal aims to contain and isolate radioactive waste from the biosphere. Reposi... more Deep geological disposal aims to contain and isolate radioactive waste from the biosphere. Repository systems are made of multiple barriers working together, typically comprising the natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system. Due to their excellent properties for the confinement of contaminants, including low permeability, high sorption capacity, and swelling/self-sealing capacity, clayey materials are considered as engineered and/or natural barriers in most repository designs under development in Europe. During the lifetime of the repository, clay barriers will be exposed to perturbations, among which those are resulting from gas and heat production within the system. It is important to verify that these perturbations will not be detrimental to the good functioning of these barriers. In this paper, it is shown how the two EURAD R&D work packages, GAS and HITEC use a combination of experimental and modelling...
Oil & Gas Science and Technology - Revue de l'IFP, 2006
-Essais d'injection de gaz dans les argiles à Opalinus du laboratoire souterrain du Mont Terri (S... more -Essais d'injection de gaz dans les argiles à Opalinus du laboratoire souterrain du Mont Terri (Suisse) : données et interprétation-La migration de gaz dans les roches argileuses est un sujet d'intérêt dans le cadre de différents types d'exploitation du sous-sol : que ce soit par exemple dans le domaine du stockage de gaz naturel, de la séquestration du CO 2 , comme éponte imperméable d'un aquifère, ou dans le domaine du stockage de déchets. Une analyse quantitative de la migration de gaz dans ces milieux à très faible perméabilité nécessite l'estimation des propriétés physiques de l'écoulement. Au laboratoire souterrain du Mont Terri (Suisse), dans les argiles à Opalinus, une roche sédimentaire jurassique, une série de tests hydrauliques et d'injection de gaz a été conduite en forages d'expérimentation. Leur but était en particulier de déterminer les propriétés de transfert des gaz dans cette roche. Cet article présente les résultats d'une campagne de tests (sollicitations de type essai hydraulique classique et test d'injection de gaz et récupération de pression de longue durée), conduite dans la roche « intacte », c'est-à-dire non perturbée mécaniquement par le creusement des galeries. Il présente une interprétation détaillée des tests reposant sur l'ajustement des données expérimentales au moyen d'un logiciel de simulation numérique biphasique (eau/gaz) de l'écoulement en milieu poreux (TOUGH2/iTOUGH2). Par analyse séquentielle, il a été possible d'obtenir un set de paramètres hydrauliques mono-et diphasiques cohérent sur l'ensemble de l'expérimentation. L'utilisation d'informations additionnelles et indépendantes sur les caractéristiques pétrophysiques de la roche (porosité et pression capillaire) a permis de mieux contraindre le problème inverse à l'étude. Bien qu'il soit difficile sur la base des différents modèles et ajustements réalisés, d'obtenir une solution unique en terme de courbe de pression capillaire et de perméabilité relative, les résultats indiquent qu'une paramétrisation classique de type Van Genuchten-Mualem serait valide. Enfin, des simulations prospectives sont présentées qui montrent que l'amélioration de la performance des essais en termes de détermination des paramètres biphasiques nécessiterait une augmentation notable de la durée de l'essai (> 1 an).
Physics and Chemistry of the Earth, Parts A/B/C, 2004
This paper addresses the achievements in understanding the hydrogeological conditions in the low ... more This paper addresses the achievements in understanding the hydrogeological conditions in the low permeability claystone formation of the Opalinus Clay at the Mont Terri Rock Laboratory. The synthesis work consisted of (i) an assessment of clay-specific artifacts which may affect the interpretation of hydraulic tests, (ii) a survey of hydraulic rock properties such as hydraulic conductivity and storage coefficient, and
The 3D in situ stress state is an important field variable to assess the reactivation potential o... more The 3D in situ stress state is an important field variable to assess the reactivation potential of tectonic faults and to predict the future structural evolution over geological time spans. Furthermore, it is a critical parameter for a wide range of underground engineering activities addressing questions with respect to stability aspects as well as productivity for georeservoirs [Fuchs and Müller, 2001; Moeck and Backers, 2011]. Stability refers e.g. for safe drill path, long-term stability of nuclear waste disposal sites or CO 2 sequestration in the underground. For the depletion of georeservoirs, re-injection of waste water and hydraulic fracturing to enhance permeability, the in situ stress is critical as it determines how much stress changes the reservoir can sustain before e.g. sealing faults are reactivated or cap rock integrity is affected. Knowledge of the in situ stress state is also required in order to forecast the effectiveness of hydraulic fracturing performed to enhance the permeability and thus productivity. However, data of the in situ stress are in general very sparse and incomplete as only a subset of the six components of the 3D stress tensor is available. E.g. the World Stress Map (WSM) Project compiles globally the contemporary orientation of maximum horizontal stress S H , but it has only 21,750 data records in the upper 40 km [Heidbach et al., 2010]. A compilation of stress magnitude data is in progress, but the global dataset has so far only ~1200 data records [Zang et al., 2012]. In order to determine all components of the 3D stress tensor spatially continuous, a geomechanical-numerical model has to be set up and calibrated against the stress information.
Geological Society, London, Special Publications, 2014
This paper describes a large-scale experiment on gas transport and hydromechanical processes arou... more This paper describes a large-scale experiment on gas transport and hydromechanical processes around underground structures as part of a long-term geoscientific research programme at the Mont Terri Underground Rock Laboratory in the Jura Mountains of Switzerland. A horizontal microtunnel with a diameter of 1 m and a length of 13 m was drilled in an overconsolidated claystone formation. After installing monitoring instruments in the open tunnel, the end of the tunnel was backfilled with sand (test section) and a large hydraulic packer was emplaced in the seal section. The packer was inflated and subsequently the test interval was saturated with a synthetic pore-water. Following saturation an extended programme of hydraulic testing was performed over a two year period. A series of gas injection tests was then performed over a period of approximately 1.5 years. Following this first series of gas injections, a long post-gas hydraulic test has been initiated. The paper presents data and i...
13th ISRM International Congress of Rock Mechanics, May 10, 2015
ABSTRACT Numerous research studies have shown that clay rock formations exhibit favourable charac... more ABSTRACT Numerous research studies have shown that clay rock formations exhibit favourable characteristics for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. The goal of this paper is to present new rock mechanics insights into the phenomena involved in the EDZ formation and evolution processes in Opalinus Clay, a clay shale currently being assessed as a potential host rock for an underground repository in Northern Switzerland. More specifically, discontinuum-based computer simulations, using a hybrid finite-discrete element method (FDEM) approach, were applied to two case studies considering circular excavations in an anisotropic Opalinus Clay formation. In the first case study, numerical modelling was applied to the HG-A experiment, a long-term in-situ test carried out at the Mont Terri underground rock laboratory to investigate the hydro-mechanical response of a backfilled and sealed microtunnel. A mechanistic analysis of the fracturing processes involved in the EDZ formation was carried out. In the second case study, the long-term effect of the bentonite backfill swelling on the EDZ around an emplacement was numerically analyzed. Overall, the simulation results highlight short-term distinctive rock failure kinematics due to the bedded rock structure, as well as a long-term reduction of the excavation-induced fracture porosity in response to mechanical loading. KEYWORDS
2nd EAGE International Conference on Fault and Top Seals - From Pore to Basin Scale 2009, Sep 21, 2009
The transfer of Argon and Helium gas through a sample of Opalinus Clay, a low permeability indura... more The transfer of Argon and Helium gas through a sample of Opalinus Clay, a low permeability indurated formation, was investigated by means of injection tests in the laboratory. The experimental data were carefully analysed by means of numerical simulations, including two-phase viscous-capillary flow and diffusional transport.
Geological Society, London, Special Publications, 2018
Stratigraphic sequences in boreholes are commonly estimated by interpreting combinations of well ... more Stratigraphic sequences in boreholes are commonly estimated by interpreting combinations of well logs. The interpretation is generally tedious and is made some time after log completion, which often leads to a loss of valuable first-hand information gathered on-site. This may lead to delayed or potentially poor on-site decisions. To make things worse, the standard interpretation of well logs is, at least to a certain degree, subjective and based on the manipulation of data, which may be difficult to trace in the long term. Small changes in lithology are often disregarded and alternating thin layers presenting different lithologies are often combined in one single (notably thicker) stratigraphic unit. Therefore an automatic parameter-based and thus traceable and objective quick look at the lithology immediately after log completion represents both a valuable tool to help with on-site decisions and a solid, mathematically based starting point for further physically based interpretatio...
The stress field at depth is a relevant parameter for the design of subsurface constructions and ... more The stress field at depth is a relevant parameter for the design of subsurface constructions and reservoir management. Yet the distortion of the regional stress field due to local-scale features such as sedimentary and tectonic structures or topography is often poorly constrained. We conduct a stress sensitivity analysis using 3-D numerical geomechanical modelling with an elasto-plastic material law to explore the impact of such site-specific features on the stress field in a sedimentary sequence of the Swiss Alpine foreland. The model's dimensions are 14 × 14 × 3 km 3 and it contains 10 units with different mechanical properties, intersected by two regional fault zones. An initial stress state is established involving a semi-empirical relationship between the ratio of horizontal to vertical stress and the overconsolidation ratio of argillaceous sediments. The model results indicate that local topography can affect the stress field significantly to depths greater than the relief contrasts at the surface, especially in conjunction with horizontal tectonic loading. The complexity and frictional properties of faults are also relevant. The greatest variability of the stress field arises across the different sedimentary units. Stress magnitudes and stress anisotropy are much larger in stiffer formations such as massive limestones than in softer argillaceous formations. The stiffer formations essentially carry the load of the far-field forces and are therefore more sensitive to changes of the boundary conditions. This general characteristic of stress distribution in the stiff and soft formations is broadly maintained also with progressive loading towards the plastic limit. The stress field in argillaceous sediments within a stack of formations with strongly contrasting mechanical properties like in the Alpine foreland appears to be relatively insensitive to changes in the tectonic boundary conditions and is largely controlled by the maximum stiffness contrast with respect to the load-bearing formations.
Three parameters control the development of secondary sub-seismic fractures: Material properties,... more Three parameters control the development of secondary sub-seismic fractures: Material properties, the fault displacement and its morphology. We demonstrate how restoring seismic faults with three dimensional geometrical kinematic modelling can generate information about the intensity and orientation of the fractures around the fault.
Core samples from the Opalinus Clay, an indurated clay formation of Jurassic age, were subjected ... more Core samples from the Opalinus Clay, an indurated clay formation of Jurassic age, were subjected to comprehensive microstructural investigations: transmission electron microscopy, focused ion beam nanotomography, and X-ray computed tomography. Digital representations of the microstructure were derived from the tomographic images by segmentation and 3D reconstruction of the geomaterial on a grid of regular voxel elements with a typical edge length of as little as 10 nm and a maximum size on the order of 1000 3 voxels. Pertinent geotechnical properties were derived on the microscopic scale using state-of-the-art image-processing procedures. The results were compared with results from geotechnical laboratory characterization methods such as mercury intrusion porosimetry, nitrogen adsorption/desorption measurements, grain-size analysis, X-ray diffraction, and triaxial testing. Good agreement was achieved between microscopic and macroscopic characterization methods. The macroscopic (poro-elastic) deformation behavior of the Opalinus Clay was also reproduced reasonably well by geomechanical modeling on the microscopic scale. The cross-anisotropic stiffness of the rock mass is thus caused partly by preferred orientation of pore structures along bedding. In addition, new insight was gained with regard to the role of small mesopores (2-10 nm), essentially controlling the macroscopic deformation behavior of indurated clays.
In the development of deep geological repositories (DGRs), performance assessment modeling is use... more In the development of deep geological repositories (DGRs), performance assessment modeling is used to evaluate the integrity and performance of the engineered and geological barriers for thousands or millions of years of evolution of the disposal system. To evaluate the suitability of a site for a DGR, geoscientific data from dedicated site investigation programs are integrated into site-specific assessments. This paper presents the development and implementation of a modeling workflow aimed at comparing three potential siting areas for a DGR in Switzerland from the viewpoint of long-term safety and technical feasibility. The workflow follows the guidelines of the national regulator addressing safety relevant criteria such as the barrier efficiency of the host rock and its mechanical and chemical integrity in response to repository-induced influences and the long-term stability of the repository site over geological scales. In the regulatory requirements, the role of parametric, con...
Physics And Chemistry Of The Earth, Parts A/b/c, 2008
ABSTRACT In studies related to deep geological disposal of radioactive waste, it is current pract... more ABSTRACT In studies related to deep geological disposal of radioactive waste, it is current practice to transfer external information (e.g. from other sites, from underground rock laboratories or from natural analogues) to safety cases for specific projects. Transferable information most commonly includes parameters, investigation techniques, process understanding, conceptual models and high-level conclusions on system behaviour. Prior to transfer, the basis of transferability needs to be established. In argillaceous rocks, the most relevant common feature is the microstructure of the rocks, essentially determined by the properties of clay–minerals. Examples are shown from the Swiss and French programmes how transfer of information was handled and justified. These examples illustrate how transferability depends on the stage of development of a repository safety case and highlight the need for adequate system understanding at all sites involved to support the transfer.
Deep geological disposal aims to contain and isolate radioactive waste from the biosphere. Reposi... more Deep geological disposal aims to contain and isolate radioactive waste from the biosphere. Repository systems are made of multiple barriers working together, typically comprising the natural geological barrier provided by the repository host rock and its surroundings and an engineered barrier system. Due to their excellent properties for the confinement of contaminants, including low permeability, high sorption capacity, and swelling/self-sealing capacity, clayey materials are considered as engineered and/or natural barriers in most repository designs under development in Europe. During the lifetime of the repository, clay barriers will be exposed to perturbations, among which those are resulting from gas and heat production within the system. It is important to verify that these perturbations will not be detrimental to the good functioning of these barriers. In this paper, it is shown how the two EURAD R&D work packages, GAS and HITEC use a combination of experimental and modelling...
Oil & Gas Science and Technology - Revue de l'IFP, 2006
-Essais d'injection de gaz dans les argiles à Opalinus du laboratoire souterrain du Mont Terri (S... more -Essais d'injection de gaz dans les argiles à Opalinus du laboratoire souterrain du Mont Terri (Suisse) : données et interprétation-La migration de gaz dans les roches argileuses est un sujet d'intérêt dans le cadre de différents types d'exploitation du sous-sol : que ce soit par exemple dans le domaine du stockage de gaz naturel, de la séquestration du CO 2 , comme éponte imperméable d'un aquifère, ou dans le domaine du stockage de déchets. Une analyse quantitative de la migration de gaz dans ces milieux à très faible perméabilité nécessite l'estimation des propriétés physiques de l'écoulement. Au laboratoire souterrain du Mont Terri (Suisse), dans les argiles à Opalinus, une roche sédimentaire jurassique, une série de tests hydrauliques et d'injection de gaz a été conduite en forages d'expérimentation. Leur but était en particulier de déterminer les propriétés de transfert des gaz dans cette roche. Cet article présente les résultats d'une campagne de tests (sollicitations de type essai hydraulique classique et test d'injection de gaz et récupération de pression de longue durée), conduite dans la roche « intacte », c'est-à-dire non perturbée mécaniquement par le creusement des galeries. Il présente une interprétation détaillée des tests reposant sur l'ajustement des données expérimentales au moyen d'un logiciel de simulation numérique biphasique (eau/gaz) de l'écoulement en milieu poreux (TOUGH2/iTOUGH2). Par analyse séquentielle, il a été possible d'obtenir un set de paramètres hydrauliques mono-et diphasiques cohérent sur l'ensemble de l'expérimentation. L'utilisation d'informations additionnelles et indépendantes sur les caractéristiques pétrophysiques de la roche (porosité et pression capillaire) a permis de mieux contraindre le problème inverse à l'étude. Bien qu'il soit difficile sur la base des différents modèles et ajustements réalisés, d'obtenir une solution unique en terme de courbe de pression capillaire et de perméabilité relative, les résultats indiquent qu'une paramétrisation classique de type Van Genuchten-Mualem serait valide. Enfin, des simulations prospectives sont présentées qui montrent que l'amélioration de la performance des essais en termes de détermination des paramètres biphasiques nécessiterait une augmentation notable de la durée de l'essai (> 1 an).
Physics and Chemistry of the Earth, Parts A/B/C, 2004
This paper addresses the achievements in understanding the hydrogeological conditions in the low ... more This paper addresses the achievements in understanding the hydrogeological conditions in the low permeability claystone formation of the Opalinus Clay at the Mont Terri Rock Laboratory. The synthesis work consisted of (i) an assessment of clay-specific artifacts which may affect the interpretation of hydraulic tests, (ii) a survey of hydraulic rock properties such as hydraulic conductivity and storage coefficient, and
The 3D in situ stress state is an important field variable to assess the reactivation potential o... more The 3D in situ stress state is an important field variable to assess the reactivation potential of tectonic faults and to predict the future structural evolution over geological time spans. Furthermore, it is a critical parameter for a wide range of underground engineering activities addressing questions with respect to stability aspects as well as productivity for georeservoirs [Fuchs and Müller, 2001; Moeck and Backers, 2011]. Stability refers e.g. for safe drill path, long-term stability of nuclear waste disposal sites or CO 2 sequestration in the underground. For the depletion of georeservoirs, re-injection of waste water and hydraulic fracturing to enhance permeability, the in situ stress is critical as it determines how much stress changes the reservoir can sustain before e.g. sealing faults are reactivated or cap rock integrity is affected. Knowledge of the in situ stress state is also required in order to forecast the effectiveness of hydraulic fracturing performed to enhance the permeability and thus productivity. However, data of the in situ stress are in general very sparse and incomplete as only a subset of the six components of the 3D stress tensor is available. E.g. the World Stress Map (WSM) Project compiles globally the contemporary orientation of maximum horizontal stress S H , but it has only 21,750 data records in the upper 40 km [Heidbach et al., 2010]. A compilation of stress magnitude data is in progress, but the global dataset has so far only ~1200 data records [Zang et al., 2012]. In order to determine all components of the 3D stress tensor spatially continuous, a geomechanical-numerical model has to be set up and calibrated against the stress information.
Geological Society, London, Special Publications, 2014
This paper describes a large-scale experiment on gas transport and hydromechanical processes arou... more This paper describes a large-scale experiment on gas transport and hydromechanical processes around underground structures as part of a long-term geoscientific research programme at the Mont Terri Underground Rock Laboratory in the Jura Mountains of Switzerland. A horizontal microtunnel with a diameter of 1 m and a length of 13 m was drilled in an overconsolidated claystone formation. After installing monitoring instruments in the open tunnel, the end of the tunnel was backfilled with sand (test section) and a large hydraulic packer was emplaced in the seal section. The packer was inflated and subsequently the test interval was saturated with a synthetic pore-water. Following saturation an extended programme of hydraulic testing was performed over a two year period. A series of gas injection tests was then performed over a period of approximately 1.5 years. Following this first series of gas injections, a long post-gas hydraulic test has been initiated. The paper presents data and i...
13th ISRM International Congress of Rock Mechanics, May 10, 2015
ABSTRACT Numerous research studies have shown that clay rock formations exhibit favourable charac... more ABSTRACT Numerous research studies have shown that clay rock formations exhibit favourable characteristics for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. The goal of this paper is to present new rock mechanics insights into the phenomena involved in the EDZ formation and evolution processes in Opalinus Clay, a clay shale currently being assessed as a potential host rock for an underground repository in Northern Switzerland. More specifically, discontinuum-based computer simulations, using a hybrid finite-discrete element method (FDEM) approach, were applied to two case studies considering circular excavations in an anisotropic Opalinus Clay formation. In the first case study, numerical modelling was applied to the HG-A experiment, a long-term in-situ test carried out at the Mont Terri underground rock laboratory to investigate the hydro-mechanical response of a backfilled and sealed microtunnel. A mechanistic analysis of the fracturing processes involved in the EDZ formation was carried out. In the second case study, the long-term effect of the bentonite backfill swelling on the EDZ around an emplacement was numerically analyzed. Overall, the simulation results highlight short-term distinctive rock failure kinematics due to the bedded rock structure, as well as a long-term reduction of the excavation-induced fracture porosity in response to mechanical loading. KEYWORDS
2nd EAGE International Conference on Fault and Top Seals - From Pore to Basin Scale 2009, Sep 21, 2009
The transfer of Argon and Helium gas through a sample of Opalinus Clay, a low permeability indura... more The transfer of Argon and Helium gas through a sample of Opalinus Clay, a low permeability indurated formation, was investigated by means of injection tests in the laboratory. The experimental data were carefully analysed by means of numerical simulations, including two-phase viscous-capillary flow and diffusional transport.
Geological Society, London, Special Publications, 2018
Stratigraphic sequences in boreholes are commonly estimated by interpreting combinations of well ... more Stratigraphic sequences in boreholes are commonly estimated by interpreting combinations of well logs. The interpretation is generally tedious and is made some time after log completion, which often leads to a loss of valuable first-hand information gathered on-site. This may lead to delayed or potentially poor on-site decisions. To make things worse, the standard interpretation of well logs is, at least to a certain degree, subjective and based on the manipulation of data, which may be difficult to trace in the long term. Small changes in lithology are often disregarded and alternating thin layers presenting different lithologies are often combined in one single (notably thicker) stratigraphic unit. Therefore an automatic parameter-based and thus traceable and objective quick look at the lithology immediately after log completion represents both a valuable tool to help with on-site decisions and a solid, mathematically based starting point for further physically based interpretatio...
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Papers by Paul Marschall