Damage and sealing of clay rocks detected by measurements of gas permeability

Zhang, Chunliang; Rothfuchs, T.

doi:10.1016/j.pce.2008.10.013

Cited by 64 publications

(23 citation statements)

References 9 publications

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“…Given the fact that clay rock is generally viewed as soft rock, it seems logical to use Eq (2-28) for fractures in clay rock. This is supported by a number of laboratory measurements that show linear relationships between the log of measured fracture permeability and stress (e.g., Blumling et al, 2007;Zhang and Rothfuchs, 2008;Popp et al, 2008). However, data reported by Jobmann et al (2010) seem to indicate that permeability relationships are better represented by a curve similar to that with 0 > r b…”

Section: Fracture Aperture and Permeabilitymentioning

confidence: 76%

Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

Liu¹

2010

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Section: Fracture Aperture and Permeabilitymentioning

confidence: 76%

Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

Liu¹

2010

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“…5 for fractures in clay rock. This is supported by a number of laboratory measurements that show linear relationships between the log of measured fracture permeability and stress (e.g., Blumling et al 2007;Zhang and Rothfuchs 2008;Popp et al 2008).…”

Section: Constitutive Relationshipsmentioning

confidence: 64%

Constitutive Relationships for Elastic Deformation of Clay Rock: Data Analysis

2011

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Geological repositories have been considered a feasible option worldwide for storing high-level nuclear waste. Clay rock is one of the rock types under consideration for such purposes, because of its favorable features to prevent radionuclide transport from the repository. Coupled hydromechanical processes have an important impact on the performance of a clay repository, and establishing constitutive relationships for modeling such processes are essential. In this study, we propose several constitutive relationships for elastic deformation in indurated clay rocks based on three recently developed concepts. First, when applying Hooke's law in clay rocks, true strain (rock volume change divided by the current rock volume), rather than engineering strain (rock volume change divided by unstressed rock volume), should be used, except when the degree of deformation is very small. In the latter case, the two strains will be practically identical. Second, because of its inherent heterogeneity, clay rock can be divided into two parts, a hard part and a soft part, with the hard part subject to a relatively small degree of deformation compared with the soft part. Third, for swelling rock like clay, effective stress needs to be generalized to include an additional term resulting from the swelling process. To evaluate our theoretical development, we analyze uniaxial test data for core samples of Opalinus clay and laboratory measurements of single fractures within macro-cracked Callovo-Oxfordian argillite samples subject to both confinement and water reduced swelling. The results from this evaluation indicate that our constitutive relationships can adequately represent the data and explain the related observations.

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“…In general, at the laboratory scale, the initial conditions are a fully water-saturated medium subjected to a gas pressure of given amplitude, until gas passage is detected by varying means. However, no consensus exists as the exact phenomena involved in the gas migration (or breakthrough) through water-saturated clayrocks [3,20,22,[24][25][26][27][28][29]. Rather, several mechanisms are considered.…”

Section: Gas Migration Mechanismsmentioning

confidence: 99%

“…This mechanism requires gas pressures of sufficient magnitude to counterbalance the local compressive stress state (reproducing the in situ loading), and to reach the material tensile strength. It is favored in the case of claystones, which possess very low tensile strength [29].…”

Section: Gas Migration Mechanismsmentioning

confidence: 99%

Gas Breakthrough Pressure (GBP) through Claystones: Correlation with FIB/SEM Imaging of the Pore Volume

Song

Davy

Tománek

2016

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-This contribution uses six claystone samples imaged by FIB/SEM (Focused Ion Beam/ Scanning Electron Microscopy), within micrometric volumes located in the clay matrix; their 3D connected pore network is identified down to 17-22 nm pore size. All samples are gently dried to minimize damage, and several are impregnated with Poly(Methyl MethAcrylate) (PMMA) resin to avoid further damage during FIB/SEM observations. Three pore volumes out of six are connected between two parallel end surfaces through crack-like pores; two are not connected between any two parallel end surfaces; only one sample has a connected pore network distinct from cracks. By assuming varied pathways for gas to migrate by capillarity through the connected pore volumes (either by taking the shortest path, or through the largest path, or through the most frequent pore size, or by simulating the ingress of a non wetting fluid), we determine the Gas Breakthrough Pressure (GBP) through the initially fully liquid saturated claystone, from these micrometric volumes. The scale change (from the micrometric to the macroscopic scale) is assumed possible without changing the GBP value, and clay/water interactions are not accounted for. By comparison with GBP values measured in the laboratory on centimetric-sized claystone samples, it is concluded that breakthrough occurs most probably by capillary digitation; micro-cracks are the most probable pathways for gas, so that gas does not progress in a homogeneous manner through the claystone, as standard macroscopic finite element models would represent it. For intact claystone, predictions based on the capillary ingress of a non wetting fluid provide a GBP value ranging between 7-14 MPa.Résumé -Corrélations entre Pression de Percée de Gaz (PPG) et imagerie FIB/MEB de roches argileuses (argilites) -Six échantillons de roches argileuses (argilites) sont observés au FIF/MEB (Faisceau d'Ions Focalisé couplé à un Microscope Électronique à Balayage) au sein de volumes micrométriques situés dans la matrice argileuse (seule partie poreuse du matériau). Les échantillons sont séchés de façon à minimiser leur endommagement, et imprégnés ou non de résine polyméthacrylate de méthyle (PMMA) pour les maintenir lors des observations. Le réseau poreux connecté en 3D de ces échantillons est mesuré jusqu'à des tailles de pores de 17-22 nm de diamètre. Trois réseaux poreux sur six sont connectés par des pores de morphologie identique à des fissures ; deux réseaux poreux ne sont pas connectés entre deux faces paralléles de l'échantillon ; un seul réseau poreux (sur six) est connecté par des pores qui ne correspondent pas à des fissures. En supposant différents modes de transport capillaire (via le chemin le plus court, via le chemin le plus large, via la taille de pore la plus fréquente, ou en simulant l'intrusion de fluide non mouillant) à l'échelle de ces réseaux poreux micrométriques, nous déterminons la Pression de Percée de Gaz (PPG) au travers DOI: 10.2516 This is an Open Access article distributed under the terms...

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Damage and sealing of clay rocks detected by measurements of gas permeability

Cited by 64 publications

References 9 publications

Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

Modeling Coupled Processes in Clay Formations for Radioactive Waste Disposal

Constitutive Relationships for Elastic Deformation of Clay Rock: Data Analysis

Gas Breakthrough Pressure (GBP) through Claystones: Correlation with FIB/SEM Imaging of the Pore Volume

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