Critical Role of the Immobile Zone in Non-Fickian Two-Phase Transport: A New Paradigm

Karadimitriou, Nikolaos; Niasar, Vahid; Babaei, Masoud; Shore, Craig A.

doi:10.1021/acs.est.5b05947

Cited by 81 publications

(111 citation statements)

References 51 publications

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“…In contrary to the column-scale experiments 17, 20, 21 , high-resolution real-time (optical and X-ray) imaging has lately allowed us to quantify directly the pore-scale mixing and transport in porous media 22–24 even under two fluid phase conditions 25, 26 . From the hydro-dynamic point of view, the existence of two fluid phases in a porous medium will create some hydrodynamically stagnant zones in each fluid with very weak (close to zero) velocity fields, which will make the local transport regime to be diffusive.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…25 Karadimitriou et al . 25 who directly quantified the stagnant zones and showed that the diffusive mass exchange rate between the mobile and the immobile region in the MIM model is time and flow-rate dependent. Also, although the MIM model could fit the experimental data very well, there was no consistency between the fitted parameters and parameters estimated directly from the experiments.…”

Section: Introductionmentioning

confidence: 99%

“…This study is a follow-up study of Karadimitriou et al . 25 in which for the first time using direct image analysis, the impact of flow rate on transport properties under the same saturation topology is studied.…”

Section: Introductionmentioning

confidence: 99%

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Hydro-dynamic Solute Transport under Two-Phase Flow Conditions

Karadimitriou

Niasar

Godinez-Brizuela

2017

Sci Rep

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There are abundant examples of natural, engineering and industrial applications, in which “solute transport” and “mixing” in porous media occur under multiphase flow conditions. Current state-of-the-art understanding and modelling of such processes are established based on flawed and non-representative models. Moreover, there is no direct experimental result to show the true hydrodynamics of transport and mixing under multiphase flow conditions while the saturation topology is being kept constant for a number of flow rates. With the use of a custom-made microscope, and under well-controlled flow boundary conditions, we visualized directly the transport of a tracer in a Reservoir-on-Chip (RoC) micromodel filled with two immiscible fluids. This study provides novel insights into the saturation-dependency of transport and mixing in porous media. To our knowledge, this is the first reported pore-scale experiment in which the saturation topology, relative permeability, and tortuosity were kept constant and transport was studied under different dynamic conditions in a wide range of saturation. The critical role of two-phase hydrodynamic properties on non-Fickian transport and saturation-dependency of dispersion are discussed, which highlight the major flaws in parametrization of existing models.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydro-dynamic Solute Transport under Two-Phase Flow Conditions

Karadimitriou

Niasar

Godinez-Brizuela

2017

Sci Rep

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“…1,2 In recent years, the additional oil extracted by tuning the composition of the injected water has revived the interest in a more detailed understanding of the nature of the interactions between the rock and the fluids residing in the pore. 3−18 …”

Section: Introductionmentioning

confidence: 99%

Cation Exchange in the Presence of Oil in Porous Media

Farajzadeh

Guo

Winden

et al. 2017

ACS Earth Space Chem.

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Cation exchange is an interfacial process during which cations on a clay surface are replaced by other cations. This study investigates the effect of oil type and composition on cation exchange on rock surfaces, relevant for a variety of oil-recovery processes. We perform experiments in which brine with a different composition than that of the in situ brine is injected into cores with and without remaining oil saturation. The cation-exchange capacity (CEC) of the rocks was calculated using PHREEQC software (coupled to a multipurpose transport simulator) with the ionic composition of the effluent histories as input parameters. We observe that in the presence of crude oil, ion exchange is a kinetically controlled process and its rate depends on residence time of the oil in the pore, the temperature, and kinetic rate of adsorption of the polar groups on the rock surface. The cation-exchange process occurs in two stages during two phase flow in porous media. Initially, the charged sites of the internal surface of the clays establish a new equilibrium by exchanging cations with the aqueous phase. At later stages, the components of the aqueous and oleic phases compete for the charged sites on the external surface or edges of the clays. When there is sufficient time for crude oil to interact with the rock (i.e., when the core is aged with crude oil), a fraction of the charged sites are neutralized by the charged components stemming from crude oil. Moreover, the positively charged calcite and dolomite surfaces (at the prevailing pH environment of our experiments) are covered with the negatively charged components of the crude oil and therefore less mineral dissolution takes place when oil is present in porous media.

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Impact of saturation on dispersion and mixing in porous media: Photobleaching pulse injection experiments and shear‐enhanced mixing model

Jiménez‐Martínez

Borgne

Tabuteau

et al. 2017

Water Resources Research

126

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The dynamics of solute dispersion and mixing in unsaturated flows is analyzed from photobleaching experiments in two‐dimensional porous micromodels. This technique allows producing pulse line (delta‐Dirac) injections of a conservative tracer by bleaching a finite volume of fluorescent without disturbing the flow field. The temporal evolution of the concentration field and the spatial distribution of the air and water phases can be monitored at pore scale. We study the dispersion and mixing of a line of tracer under different water saturations. While dispersion in saturated porous media follows an approximately Fickian scaling, a shift to ballistic scaling is observed as soon as saturation is lowered. Hence, at the time scale of observation, dispersion in our unsaturated flows is dominated by the ballistic separation of tracer blobs within the water phase, between trapped clusters and preferential flow paths. While diffusion plays a minor role in the longitudinal dispersion during the time scale of the experiments, its interplay with fluid deformation is apparent in the dynamics of mixing. The scalar dissipation rates show an initial stretching regime, during which mixing is enhanced by fluid deformation, followed by a dissipation regime, during which diffusion overcomes compression induced by stretching. The transition between these two regimes occurs at the mixing time, when concentration gradients are maximum. We propose a predictive analytical model, based on shear‐enhanced diffusion, that captures the dynamics of mixing from basic unsaturated porous media parameters, suggesting that this type of model may be a useful framework at larger scales.

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Critical Role of the Immobile Zone in Non-Fickian Two-Phase Transport: A New Paradigm

Cited by 81 publications

References 51 publications

Hydro-dynamic Solute Transport under Two-Phase Flow Conditions

Hydro-dynamic Solute Transport under Two-Phase Flow Conditions

Cation Exchange in the Presence of Oil in Porous Media

Impact of saturation on dispersion and mixing in porous media: Photobleaching pulse injection experiments and shear‐enhanced mixing model

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