Formulation of electro-chemico-osmotic processes in soils

Çorapçıoğlu, M. Yavuz

doi:10.1007/bf00136350

Cited by 21 publications

(13 citation statements)

References 23 publications

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“…The coefficient L EE is commonly referred to as electric conductivity in Ohm's law, whereas L EP and L CP are the streaming current and ultrafiltration parameters, which reflect electric current and total ion flux driven by hydraulic gradients (see e.g. [16,69]). …”

Section: Onsager's Reciprocity Relationsmentioning

confidence: 99%

A dual-porosity model for ionic solute transport in expansive clays

Murad

Moyne

2007

Comput Geosci

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A microstructure model of dual-porosity type is proposed to describe contaminant transport in fullysaturated swelling clays. The swelling medium is characterized by three separate-length scales (nano, micro, and macro) and two levels of porosity (nano-and micropores). At the nanoscale, the medium is composed of charged clay particles saturated by a binary monovalent aqueous electrolyte solution. At the intermediate (micro) scale, the two-phase homogenized system is represented by swollen clay clusters (or aggregates) with the nanoscale electrohydrodynamics, local charge distribution, and disjoining pressure effects incorporated in the averaged constitutive laws of the electro-chemo-mechanical coefficients and the swelling pressure, which appear in Onsager's reciprocity relations and in a modified form of Terzaghi's effective principle, respectively. The microscopic coupling between aggregates and a bulk solution lying in the micropores is ruled by a slip boundary condition on the tangential velocity of the fluid, which captures the effects of the thin electrical double layers surrounding each clay cluster. At the macroscale, the system of clay clusters is homogenized with the bulk fluid. The resultant macroscopic picture is governed by a dual-porosity model wherein macroscopic flow and ion transport take place in the bulk solution and the clay clusters act as sources/sinks of mass of water and solutes to the bulk fluid. The homogenization procedure yields a threescale model of the swelling medium by providing new nano and micro closure problems, which are solved numerically to construct constitutive laws for the effective electro-chemo-hydro-mechanical coefficients. Considering local instantaneous equilibrium between the clay aggregates and micropores, a quasisteady version of the dual-porosity model is proposed. When combined with the three-scale portrait of the swelling medium, the quasisteady model allows us to build-up numerically the constitutive law of the equilibrium adsorption isotherm, which governs the instantaneous immobilization of the solutes in the clay clusters. Moreover, the constitutive behavior of the retardation coefficient is also constructed by exploring its representation in terms of the local profile of the electrical double layer potential of the electrolyte solution, which satisfies the Poisson-Boltzmann problem at the nanoscale.

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Section: Onsager's Reciprocity Relationsmentioning

confidence: 99%

A dual-porosity model for ionic solute transport in expansive clays

Murad

Moyne

2007

Comput Geosci

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“…It is reasonable to assume that any electrical charge buildup is instantly neutralized, ie, the electrostatic condition holds for both porous media

\partial ρ_{e}^{I} true/ \partial t = \partial ρ_{e}^{II} true/ \partial t = 0

…”

Section: Dual‐poro‐chemo‐electro‐elastic Governing Equationsmentioning

confidence: 99%

“…In addition, the electrically charged clay in shale can cause shrinking or swelling when exposed to aqueous solutions because of the exchange of water and ions with the circulation fluids. These flows are driven by gradients of hydraulic, chemical, and electrical potentials . The theory of poro‐chemo‐electro‐elasticity should be used.…”

Section: Introductionmentioning

confidence: 99%

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Responses of chemically active and naturally fractured shale under time‐dependent mechanical loading and ionic solution exposure

Liu

Hoang

Abousleiman

2017

Num Anal Meth Geomechanics

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SummaryIn this paper, the analytical dual-porosity dual-permeability poromechanics solution for saturated cylinders is extended to account for electrokinetic effects and material transverse isotropy, which simulate the responses of chemically active naturally fractured shale under time-dependent mechanical loading and ionic solution exposure.The solution addresses the stresses, fracture pore pressure, matrix pore pressure, fluid fluxes, ion concentration evolution, and displacements due to the applied stress, pore pressure, and solute concentration difference between the sample and the circulation fluid. The presented solution will not only help validate numerical simulations but also assist in calibrating and interpreting laboratory results on dual-porosity dual-permeability shale. It is recommended that the analytical solutions of radial and axial displacements be used to match the corresponding laboratory-recorded data to determine shale dual permeability and chemo-electrical parameters including membrane coefficient, ions diffusion coefficients, and electro-osmotic permeability.KEYWORDS chemically active, dual-poro-chemo-electro-elasticity, electro-osmotic permeability, natural fractures, shale | INTRODUCTIONThe recent boom in oil and gas production from shale reservoirs around the world has produced a tectonic shift in the global energy landscape. However, despite the promising potentials, there are still many challenges in understanding, analyzing, and predicting the behaviors of these unconventional reservoirs during drilling, stimulation, and production. Some of these challenges come from the complex geomechanics properties of shale. Most shales have higher degree of mechanical anisotropy than conventional reservoir rocks. In addition, shale displays swelling and shrinking behaviors when exposed to aqueous drilling and stimulation fluids because of the electrochemical interaction between its clay content and the solutions. Furthermore, many shales are naturally fractured, as illustrated in Figure 1, resulting in complex pore pressure distribution and evolution in the dual-porosity dual-permeability system. It is noted that shales with dual-porosity system that might result from different scales of pore structures 1 can be also modeled using the current approach.This study aims to investigate the behavior of dual-porosity dual-permeability shale rocks under laboratory conditions. The original dual-porosity dual-permeability concept for fractured/fissured rocks was proposed by Barenblatt et al. 2 The 2 overlapping continua, primary porosity and secondary porosity, possess their own fluid pressure fields. Warren and Root 3 proposed an idealized dual-porosity model, assuming that the secondary porosity consists of an orthogonal system of uniform fractures and that fluid can communicate between primary and secondary porosities, but not among the primary porosity elements. Later on,

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“…Since precipitation of chemical species locally reduces the ionic strength of the pore water, the electrical conductivity of the soil is also reduced. Many of these aspects have been satisfactorily taken into account by theoretical and numerical models [1,2] when reproducing the remediation of pure clays. In this case, the acidic front moves faster than the basic one, so that precipitation and electrical potential drop are usually confined in the soil portion closer to the cathode.…”

Section: Introductionmentioning

confidence: 99%

Influence of calcite on the electrokinetic treatment of a natural clay

et al. 2009

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After presenting a geochemical model for the interaction between calcite and varying environmental conditions, the paper discusses the experimental results of long duration electrokinetic tests, run on a natural clayey soil in unbuffered conditions. Local measurements of electrical potential, temperature and water flow were performed during the tests, while pH and fluid conductivity were measured locally once the tests had been dismantled. Sharp change of pH and reduction of the soil electrical conductivity, that in pure clays usually occur in the proximity of the cathode, were observed in the region close to the anode. As well, the soil in the anode area systematically tended to develop fractures, that mostly persisted until the end of the experiments. The features observed, that are not adequately taken into account by existing models, are interpreted in the light of the proposed calcite-water interaction. The onset of fractures, soil desaturation and electrical conductivity drop seem to be justified as a consequence of severe CO 2 pressures arising in the anode area. Calcite dissolution and precipitation is held responsible for the changes of void ratio along the samples. List of symbols[i] Chemical activity of specie i [mol dm -3 ] c i Concentration of the i-th chemical specie in the water phase [mol dm -3 ] D i Diffusion coefficient of the i-th chemical specie in free water [m 2 s -1 ] e Void ratio [-] K 1 , K 2 Equilibrium constant for carbonic acid dissociation K calcite Equilibrium constant for calcite dissociation K H Equilibrium constant for CO 2 dissolution in water K w Equilibrium constant for water autoionization m Porosity exponent in Archie's formula [-] M c Mass of calcite [kg] M i Mass of the inert minerals [kg] n Porosity [-] p Saturation exponent in Archie's formula [-] p CO2 Pressure of carbon dioxide [atm] S r Water saturation [-] u i Ionic mobility of the i-th chemical specie in free water [m 2 V -1 s -1 ] V s Volume of the solid phase [dm 3 ] V v Volume of voids [dm 3 ] V w Volume of the water phase [dm 3 ] z i Charge of the i-th specie q i Density of the inert minerals [kg dm -3 ] q c Density of calcite [kg dm -3 ] r w Pore water electrical conductivity [S m -1 ] r s Soil electrical conductivity [S m -1 ] S s Specific surface [m 2 g -1 ] w L Liquid limit [%]

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Formulation of electro-chemico-osmotic processes in soils

Cited by 21 publications

References 23 publications

A dual-porosity model for ionic solute transport in expansive clays

A dual-porosity model for ionic solute transport in expansive clays

Responses of chemically active and naturally fractured shale under time‐dependent mechanical loading and ionic solution exposure

Influence of calcite on the electrokinetic treatment of a natural clay

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