Documents disponibles écrits par cet auteur

Development of anisotropic permeability during coalbed methane production / Yu Wu in Journal of natural gas science and engineering, Vol. 2 N° 4 (Septembre 2010) 

Public ISBD [article]  in Journal of natural gas science and engineering > Vol. 2 N° 4 (Septembre 2010) . - pp. 197–210 Titre : Development of anisotropic permeability during coalbed methane production Type de document : texte imprimé Auteurs : Yu Wu, Auteur ; Jishan Liu, Auteur ; Elsworth, Derek, Auteur Année de publication : 2012 Article en page(s) : pp. 197–210 Note générale : Génie Chimique Langues : Anglais (eng) Mots-clés : CBM  Dual  poroelasticity  Directional  permeability  Numerical  modelling Résumé : Although coal–gas interactions have been comprehensively investigated, prior studies have focused on one or more component processes of effective stress in driving only isotropic changes in coal permeability. In our previous work (Wu et al., 2009) a general porosity and permeability model was developed to represent the behavior of both the primary medium (coal matrix) and the secondary medium (fractures) under conditions of variable stress. In this study the permeability model is extended to define the evolution of gas sorption-induced permeability anisotropy under the full spectrum of mechanical conditions spanning prescribed in situ stresses through constrained displacement. These models are implemented into a fully coupled model of coal deformation, gas flow and transport in the matrix system, and gas flow and transport in the fracture system. The model separately accommodates compressible gas flow and transport in the coal matrix and fracture systems and rigorously accommodates the role of mechanical deformations for a dual-porosity continuum. Since mechanical interactions and the role of sorption-induced strains are rigorously accommodated, these micro-mechanical models are capable of following the evolution of porosity and permeability in both the coal matrix and the fracture network. This model represents important non-linear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the transport system. The permeability model for fractures is verified against the analytical solution for a constant volume reservoir and applied to successfully match a suite of field data from the San Juan Basin. The fully coupled model for coal deformation and gas flow has been applied to quantify the impacts of fracture spacing and in situ ground stresses on coal properties and active processes: those involving shrinkage, swelling and direct changes in effective stress. Model results demonstrate the complex interactions of fracture–matrix induced by CBM production. ISSN : 1875-5100 En ligne : http://www.sciencedirect.com/science/article/pii/S1875510010000508 [article] Development of anisotropic permeability during coalbed methane production [texte imprimé] / Yu Wu, Auteur ; Jishan Liu, Auteur ; Elsworth, Derek, Auteur . - 2012 . - pp. 197–210. Génie Chimique Langues : Anglais (eng) in Journal of natural gas science and engineering > Vol. 2 N° 4 (Septembre 2010) . - pp. 197–210 Mots-clés : CBM  Dual  poroelasticity  Directional  permeability  Numerical  modelling Résumé : Although coal–gas interactions have been comprehensively investigated, prior studies have focused on one or more component processes of effective stress in driving only isotropic changes in coal permeability. In our previous work (Wu et al., 2009) a general porosity and permeability model was developed to represent the behavior of both the primary medium (coal matrix) and the secondary medium (fractures) under conditions of variable stress. In this study the permeability model is extended to define the evolution of gas sorption-induced permeability anisotropy under the full spectrum of mechanical conditions spanning prescribed in situ stresses through constrained displacement. These models are implemented into a fully coupled model of coal deformation, gas flow and transport in the matrix system, and gas flow and transport in the fracture system. The model separately accommodates compressible gas flow and transport in the coal matrix and fracture systems and rigorously accommodates the role of mechanical deformations for a dual-porosity continuum. Since mechanical interactions and the role of sorption-induced strains are rigorously accommodated, these micro-mechanical models are capable of following the evolution of porosity and permeability in both the coal matrix and the fracture network. This model represents important non-linear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the transport system. The permeability model for fractures is verified against the analytical solution for a constant volume reservoir and applied to successfully match a suite of field data from the San Juan Basin. The fully coupled model for coal deformation and gas flow has been applied to quantify the impacts of fracture spacing and in situ ground stresses on coal properties and active processes: those involving shrinkage, swelling and direct changes in effective stress. Model results demonstrate the complex interactions of fracture–matrix induced by CBM production. ISSN : 1875-5100 En ligne : http://www.sciencedirect.com/science/article/pii/S1875510010000508

Evolution of the pore-pressure field around a moving conical penetrometer of finite size / Fitzgerald, Michael in Journal of engineering mechanics, Vol. 136 N° 3 (Mars 2010) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 136 N° 3 (Mars 2010) . - pp. 263-272 Titre : Evolution of the pore-pressure field around a moving conical penetrometer of finite size Type de document : texte imprimé Auteurs : Fitzgerald, Michael, Auteur ; Elsworth, Derek, Auteur Article en page(s) : pp. 263-272 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Cone  penetration  tests  Soil  permeability  Hydraulic  conductivity  Groundwater  Pore  pressure. Résumé : A solution is developed for the evolution of buildup, steady, and postarrest dissipative pore-fluid pressure fields that develop around a finite-radius conical penetrometer advanced in a saturated linearly elastic porous medium. The analog with cone penetrometer testing is direct and is used to enable continuous distributions of permeability and diffusivity to be determined with depth. This analysis reveals the direct dependence of penetration rate on the induced fluid pressure field magnitudes, and predicts that a penetration rate threshold limit exists with respect to pore-pressure generation. This represents the essence of a partially drained system. The developed pore-pressure field is determined to be a function of the dissipation rate of the material, the penetration rate, and the storage effects of the advecting medium. Analysis of the pore-pressure field under start-up conditions reveals that the time required to reach steady state is strongly influenced by the penetration rate and the pressure-dissipation properties of the material. Analysis of the developed stable pressure fields illustrates the inversely proportional relationship that exists between penetration rate and pore-pressure magnitudes at the cone surface; representing the influence of storage in the medium on stable pore-pressure magnitudes. Stable pressure fields below the penetration threshold limit, UD<=10−1, form a spherical response around the cone tip transitioning to an elongated radial response for penetration rates above this limit. Postarrest analysis indicates that the prearrest penetration rate strongly influences the dissipation rate and pattern of dissipation. The developed analysis can be correlated with CPTu-recovered data to independently evaluate permeability magnitudes during steady penetration. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Evolution of the pore-pressure field around a moving conical penetrometer of finite size [texte imprimé] / Fitzgerald, Michael, Auteur ; Elsworth, Derek, Auteur . - pp. 263-272. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 136 N° 3 (Mars 2010) . - pp. 263-272 Mots-clés : Cone  penetration  tests  Soil  permeability  Hydraulic  conductivity  Groundwater  Pore  pressure. Résumé : A solution is developed for the evolution of buildup, steady, and postarrest dissipative pore-fluid pressure fields that develop around a finite-radius conical penetrometer advanced in a saturated linearly elastic porous medium. The analog with cone penetrometer testing is direct and is used to enable continuous distributions of permeability and diffusivity to be determined with depth. This analysis reveals the direct dependence of penetration rate on the induced fluid pressure field magnitudes, and predicts that a penetration rate threshold limit exists with respect to pore-pressure generation. This represents the essence of a partially drained system. The developed pore-pressure field is determined to be a function of the dissipation rate of the material, the penetration rate, and the storage effects of the advecting medium. Analysis of the pore-pressure field under start-up conditions reveals that the time required to reach steady state is strongly influenced by the penetration rate and the pressure-dissipation properties of the material. Analysis of the developed stable pressure fields illustrates the inversely proportional relationship that exists between penetration rate and pore-pressure magnitudes at the cone surface; representing the influence of storage in the medium on stable pore-pressure magnitudes. Stable pressure fields below the penetration threshold limit, UD<=10−1, form a spherical response around the cone tip transitioning to an elongated radial response for penetration rates above this limit. Postarrest analysis indicates that the prearrest penetration rate strongly influences the dissipation rate and pattern of dissipation. The developed analysis can be correlated with CPTu-recovered data to independently evaluate permeability magnitudes during steady penetration. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Hydraulic conductivity measurement from on-the-fly uCPT sounding and from VisCPT / Lee, Dae Sung in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°12 (Décembre 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°12 (Décembre 2008) . - pp. 1720–1729 Titre : Hydraulic conductivity measurement from on-the-fly uCPT sounding and from VisCPT Type de document : texte imprimé Auteurs : Lee, Dae Sung, Auteur ; Elsworth, Derek, Auteur ; Roman Hryciw, Auteur Année de publication : 2009 Article en page(s) : pp. 1720–1729 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil  permeability  Hydraulic  conductivity  Cone  penetration  tests  Saturated  soils  Measurement Résumé : Detailed profiles of hydraulic conductivity are recovered from the deployment of direct-push permeameters at the Geohydrologic Experimental and Monitoring Site, Kansas. Measurements with thin tapered tips, and with standard cone penetration test (uCPT) tips, show only minor differences, suggesting that tip-local disturbance effects are small, and that routine uCPT measurements are therefore representative of pristine conditions. Permeameter measurements are correlated against closely deployed uCPT measurements, estimates of hydraulic conductivity from uCPT sounding correlations, and from grain size correlations derived from both vision CPT (VisCPT) and from cone metrics. On-the-fly evaluations of hydraulic conductivity require that the tip-local pressure field is both steady and partially drained. Continuous penetration is shown to yield pore pressures sufficiently close to steady to enable conductivities to be directly determined. Cone metrics of cone resistance, sleeve friction, and pore pressure ratio are shown to be sufficient to discriminate between partially drained and undrained behavior, and therefore to define the permissible regime where conductivities may be determined from uCPT sounding data. Estimates of hydraulic conductivities from uCPT sounding data are shown to correlate with independently measured magnitudes of hydraulic conductivity recovered using the permeameter tests. However, most of hydraulic conductivities from the permeameter tests ( 4.5cm length screen) are underpredicted, suggesting that storage effects, the inability to reach a steady state, or the effects of dilation may influence the response. Profiles of hydraulic conductivities evaluated from the on-the-fly method also correlate well with the permeameter measurements. Predictions from soil classification and from VisCPT methods are also capable of estimating conductivities, with soil classifications giving the closest correlations of these two for this particular suite of data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A12%281 [...] [article] Hydraulic conductivity measurement from on-the-fly uCPT sounding and from VisCPT [texte imprimé] / Lee, Dae Sung, Auteur ; Elsworth, Derek, Auteur ; Roman Hryciw, Auteur . - 2009 . - pp. 1720–1729. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°12 (Décembre 2008) . - pp. 1720–1729 Mots-clés : Soil  permeability  Hydraulic  conductivity  Cone  penetration  tests  Saturated  soils  Measurement Résumé : Detailed profiles of hydraulic conductivity are recovered from the deployment of direct-push permeameters at the Geohydrologic Experimental and Monitoring Site, Kansas. Measurements with thin tapered tips, and with standard cone penetration test (uCPT) tips, show only minor differences, suggesting that tip-local disturbance effects are small, and that routine uCPT measurements are therefore representative of pristine conditions. Permeameter measurements are correlated against closely deployed uCPT measurements, estimates of hydraulic conductivity from uCPT sounding correlations, and from grain size correlations derived from both vision CPT (VisCPT) and from cone metrics. On-the-fly evaluations of hydraulic conductivity require that the tip-local pressure field is both steady and partially drained. Continuous penetration is shown to yield pore pressures sufficiently close to steady to enable conductivities to be directly determined. Cone metrics of cone resistance, sleeve friction, and pore pressure ratio are shown to be sufficient to discriminate between partially drained and undrained behavior, and therefore to define the permissible regime where conductivities may be determined from uCPT sounding data. Estimates of hydraulic conductivities from uCPT sounding data are shown to correlate with independently measured magnitudes of hydraulic conductivity recovered using the permeameter tests. However, most of hydraulic conductivities from the permeameter tests ( 4.5cm length screen) are underpredicted, suggesting that storage effects, the inability to reach a steady state, or the effects of dilation may influence the response. Profiles of hydraulic conductivities evaluated from the on-the-fly method also correlate well with the permeameter measurements. Predictions from soil classification and from VisCPT methods are also capable of estimating conductivities, with soil classifications giving the closest correlations of these two for this particular suite of data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A12%281 [...]

Indentation of a Free-Falling Sharp Penetrometer into a Poroelastic Seabed / Lee, Dae Sung in Journal of engineering mechanics, Vol. 130 N°2 (Fevrier 2004)

Public ISBD [article]  in Journal of engineering mechanics > Vol. 130 N°2 (Fevrier 2004) . - 170-179 p. Titre : Indentation of a Free-Falling Sharp Penetrometer into a Poroelastic Seabed Titre original : Impression d'un Pénétromètre Pointu en Chute Libre dans un Fond Marin Poro-Elastique Type de document : texte imprimé Auteurs : Lee, Dae Sung, Auteur ; Kaliakin, Victor N, Editeur scientifique ; Elsworth, Derek, Auteur Article en page(s) : 170-179 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Permeability  Pore  pressure  Penetrometers  Poro-elasticity  Marine  clays  Perméabilité  Pression  de  pore  Pénétromètres  Poro-élasticité  Argiles  marins Index. décimale : 621.34 Résumé : A solution is developed for the buildup, steady, and postarrest dissipative pore fluid pressure fields that develop around a conical penetrometer that self-embeds from free-fall into the seabed. Arrest from free-fall considers deceleration under undrained conditions in a purely cohesive soil, with constant shear strength with depth. The resulting decelerating velocity field is controlled by soil strength, bearing capacity factors, and inertial components. At low impact velocities the embedment process is controlled by soil strength, and at high velocities by inertia. With the deceleration defined, the solution for a point normal dislocation migrating in a poroelastic medium is extended to incorporate the influence of a tapered tip. Dynamic steady pressures, PD, develop relative to the penetrating tip geometry with their distribution conditioned by the nondimensional penetration rate, UD, incorporating impacting penetration rate, consolidation coefficient, and penetrometer radius, and the nondimensional strength, ND, additionally incorporating undrained shear strength of the sediment. Pore pressures may develop to a steady peak magnitude at the penetrometer tip, and drop as PD = 1/xD with distance xD behind the tip and along the shaft. Induced pore pressures are singular in the zone of tip taper for the assumed zero radius of the penetrometer, negating the direct evaluation of permeability magnitudes from pressures recorded on the cone face. However, peak induced pressure magnitudes may be correlated with sediment permeabilities, postarrest dissipation rates may be correlated with consolidation coefficients, and depths of penetration may be correlated with shear strengths. The magnitudes of fluid pressures evaluated on the shaft may be correlated with sharp penetrometer data (reported by Urgeles et al. in 2000) to independently evaluate magnitudes of strength and transport parameters. Une solution est développée pour les champs dispersifs d'habillage, réguliers, et postarrest de pore du liquide de pression qui se développent autour d'un pénétromètre conique que l'art de l'auto-portrait enfonce de la chute libre dans le fond de la mer. L'arrestation de la chute libre considère la décélération undrained dessous des conditions dans un sol purement cohérent, avec la résistance au cisaillement constante avec la profondeur. Le champ de ralentissement résultant de vitesse est commandé par force de sol, facteurs de portance, et composants à inertie. À de basses vitesses d'impact le processus d'embedment est commandé par force de sol, et aux vitesses élevées par l'inertie. La décélération étant défini, la solution pour une dislocation normale de point émigrant dans un milieu poroelastic est prolongée pour incorporer l'influence d'un bout conique. Les pressions régulières dynamiques, palladium, se développent relativement à la géométrie pénétrante de bout avec leur distribution conditionnée par le taux de pénétration de nondimensional, l'UD, le taux de pénétration effectuant d'incorporation, le coefficient de consolidation, et le rayon de pénétromètre, et la force de nondimensional, ND, incorporant en plus undrained la résistance au cisaillement du sédiment. Les pressions de pore peuvent se développer à une grandeur maximale régulière au bout de pénétromètre, et se laissent tomber en tant que palladium = 1/xD avec le xD de distance derrière le bout et le long de l'axe. Les pressions induites de pore sont singulières dans la zone du cône de bout pour le rayon zéro assumé du pénétromètre, niant l'évaluation directe des grandeurs de perméabilité des pressions enregistrées sur le visage de cône. Cependant, des grandeurs induites maximales de pression peuvent être corrélées avec des permeabilities de sédiment, les taux de dissipation postarrest peuvent être corrélés avec des coefficients de consolidation, et des profondeurs de la pénétration peuvent être corrélées avec des résistances au cisaillement. Les importances de pressions du liquide évaluées sur l'axe peuvent être corrélées avec des données pointues de pénétromètre (rapportées par Urgeles et autres en 2000) pour évaluer indépendamment des importances de force et pour transporter des paramètres. [article] Indentation of a Free-Falling Sharp Penetrometer into a Poroelastic Seabed = Impression d'un Pénétromètre Pointu en Chute Libre dans un Fond Marin Poro-Elastique [texte imprimé] / Lee, Dae Sung, Auteur ; Kaliakin, Victor N, Editeur scientifique ; Elsworth, Derek, Auteur . - 170-179 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 130 N°2 (Fevrier 2004) . - 170-179 p. Mots-clés : Permeability  Pore  pressure  Penetrometers  Poro-elasticity  Marine  clays  Perméabilité  Pression  de  pore  Pénétromètres  Poro-élasticité  Argiles  marins Index. décimale : 621.34 Résumé : A solution is developed for the buildup, steady, and postarrest dissipative pore fluid pressure fields that develop around a conical penetrometer that self-embeds from free-fall into the seabed. Arrest from free-fall considers deceleration under undrained conditions in a purely cohesive soil, with constant shear strength with depth. The resulting decelerating velocity field is controlled by soil strength, bearing capacity factors, and inertial components. At low impact velocities the embedment process is controlled by soil strength, and at high velocities by inertia. With the deceleration defined, the solution for a point normal dislocation migrating in a poroelastic medium is extended to incorporate the influence of a tapered tip. Dynamic steady pressures, PD, develop relative to the penetrating tip geometry with their distribution conditioned by the nondimensional penetration rate, UD, incorporating impacting penetration rate, consolidation coefficient, and penetrometer radius, and the nondimensional strength, ND, additionally incorporating undrained shear strength of the sediment. Pore pressures may develop to a steady peak magnitude at the penetrometer tip, and drop as PD = 1/xD with distance xD behind the tip and along the shaft. Induced pore pressures are singular in the zone of tip taper for the assumed zero radius of the penetrometer, negating the direct evaluation of permeability magnitudes from pressures recorded on the cone face. However, peak induced pressure magnitudes may be correlated with sediment permeabilities, postarrest dissipation rates may be correlated with consolidation coefficients, and depths of penetration may be correlated with shear strengths. The magnitudes of fluid pressures evaluated on the shaft may be correlated with sharp penetrometer data (reported by Urgeles et al. in 2000) to independently evaluate magnitudes of strength and transport parameters. Une solution est développée pour les champs dispersifs d'habillage, réguliers, et postarrest de pore du liquide de pression qui se développent autour d'un pénétromètre conique que l'art de l'auto-portrait enfonce de la chute libre dans le fond de la mer. L'arrestation de la chute libre considère la décélération undrained dessous des conditions dans un sol purement cohérent, avec la résistance au cisaillement constante avec la profondeur. Le champ de ralentissement résultant de vitesse est commandé par force de sol, facteurs de portance, et composants à inertie. À de basses vitesses d'impact le processus d'embedment est commandé par force de sol, et aux vitesses élevées par l'inertie. La décélération étant défini, la solution pour une dislocation normale de point émigrant dans un milieu poroelastic est prolongée pour incorporer l'influence d'un bout conique. Les pressions régulières dynamiques, palladium, se développent relativement à la géométrie pénétrante de bout avec leur distribution conditionnée par le taux de pénétration de nondimensional, l'UD, le taux de pénétration effectuant d'incorporation, le coefficient de consolidation, et le rayon de pénétromètre, et la force de nondimensional, ND, incorporant en plus undrained la résistance au cisaillement du sédiment. Les pressions de pore peuvent se développer à une grandeur maximale régulière au bout de pénétromètre, et se laissent tomber en tant que palladium = 1/xD avec le xD de distance derrière le bout et le long de l'axe. Les pressions induites de pore sont singulières dans la zone du cône de bout pour le rayon zéro assumé du pénétromètre, niant l'évaluation directe des grandeurs de perméabilité des pressions enregistrées sur le visage de cône. Cependant, des grandeurs induites maximales de pression peuvent être corrélées avec des permeabilities de sédiment, les taux de dissipation postarrest peuvent être corrélés avec des coefficients de consolidation, et des profondeurs de la pénétration peuvent être corrélées avec des résistances au cisaillement. Les importances de pressions du liquide évaluées sur l'axe peuvent être corrélées avec des données pointues de pénétromètre (rapportées par Urgeles et autres en 2000) pour évaluer indépendamment des importances de force et pour transporter des paramètres.