Modelling of localised gas preferential pathways in claystone

Gérard, Pierre; Harrington, J.F.; Charlier, Robert; Collin, Frèdèric

doi:10.1016/j.ijrmms.2014.01.009

Cited by 59 publications

(25 citation statements)

References 26 publications

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“…In modelling the data from test COx-1, Gerard et al (2014) introduced a hydromechanical coupling and a hypothetical pre-existing fracture. By allowing fracture permeability and capillary entry pressure to vary with fluid pressure, Gerard et al (2014) obtained a greatly improved fit to the data, highlighting the importance of the coupling between flow and mechanics.…”

Section: Modelling Gas Behaviourmentioning

confidence: 99%

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Gas transport properties through intact and fractured Callovo-Oxfordian mudstones

Harrington

Cuss

Talandier

2017

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A series of controlled water and gas experiments was undertaken on samples of Callovo-Oxfordian (COx) mudstone using a synthetic fluid and helium gas. Data from this study demonstrate that the advective movement of gas through COx is accompanied by dilation of the original fabric (i.e. the formation of pressure-induced microfissures) at gas pressures significantly below that of the minimum principal stress. Flow occurs through a local network of unstable pathways, the properties of which vary temporally and spatially within the mudstone. The coupling of variables results in the development of significant time-dependent effects affecting many aspects of COx behaviour, from the gas breakthrough time to the control of deformation processes. Variations in gas entry, breakthrough and steady-state pressures may result from the arbitrary nature of the flow pathways and/or microstructural heterogeneity. Under these conditions, the data suggest that gas flow is along pressure-induced preferential pathways, where permeability is a dependent variable related to the number, width and aperture distributions of these features. This has important implications for modelling gas migration through low permeability, clay-rich materials.

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Section: Modelling Gas Behaviourmentioning

confidence: 99%

“…By allowing fracture permeability and capillary entry pressure to vary with fluid pressure, Gerard et al (2014) obtained a greatly improved fit to the data, highlighting the importance of the coupling between flow and mechanics. Fig.…”

Section: Modelling Gas Behaviourmentioning

confidence: 99%

Gas transport properties through intact and fractured Callovo-Oxfordian mudstones

Harrington

Cuss

Talandier

2017

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“…Gas migrates by progressive tensile failure and micro-cracking of the solid skeleton, and by dilating the width of gas pathways to increase its passage [25,26,30]. 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.…”

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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“…Work by Romero et al (2012) on laboratory scale measurments lead to the development of a void ratio dependent permeability expression (Senger et al, 2014). An alternative approach proposed by Gerard et al (2014) used an embedded pre-existing fracture in a continuum finite element model. A hydromechanical coupling between the fracture aperture, permeability and the retention properties along the fracture was included.…”

Section: Dilatancymentioning

confidence: 99%