The impact of pore structure and surface roughness on capillary trapping for 2‐D and 3‐D porous media: Comparison with percolation theory

Geistlinger, Helmut; Ataei-Dadavi, Iman; Mohammadian, Sadjad; Vogel, Hans‐Jörg

doi:10.1002/2015wr017852

Cited by 63 publications

(77 citation statements)

References 56 publications

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“…[21c,86] In drainage, the wetting defending phase is mainly trapped by the bypass mechanism; in imbibition, however, the nonwetting defending phase can be trapped by either bypass or snap‐off, or a combination of both mechanisms, depending on the local topology of the pore structure, the surface roughness, and the Ca. [21a,c,87] In general, surface roughness could enhance the snap‐off trapping; bypass is more likely to be dominant at smaller Ca. [21c,88] Notably, using confocal microscopy on 3D index‐matching micromodels one can directly visualize and characterize the full 3D structure of the trapped ganglia, as shown in Figure c.…”

Section: Experiments and Resultsmentioning

confidence: 99%

Microfluidic Model Porous Media: Fabrication and Applications

Anbari

Chien

Datta

et al. 2018

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Complex fluid flow in porous media is ubiquitous in many natural and industrial processes. Direct visualization of the fluid structure and flow dynamics is critical for understanding and eventually manipulating these processes. However, the opacity of realistic porous media makes such visualization very challenging. Micromodels, microfluidic model porous media systems, have been developed to address this challenge. They provide a transparent interconnected porous network that enables the optical visualization of the complex fluid flow occurring inside at the pore scale. In this Review, the materials and fabrication methods to make micromodels, the main research activities that are conducted with micromodels and their applications in petroleum, geologic, and environmental engineering, as well as in the food and wood industries, are discussed. The potential applications of micromodels in other areas are also discussed and the key issues that should be addressed in the near future are proposed.

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Section: Experiments and Resultsmentioning

confidence: 99%

Microfluidic Model Porous Media: Fabrication and Applications

Anbari

Chien

Datta

et al. 2018

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172

158

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“…It is the dependence of the new N ca on pore geometry as described in the bracketed term in equation that shifts the separate CDC's in Figure to converge to Figure . The large values of G (Table ) explain the reason why the value of N ca needed to mobilize the nonwetting phase in micromodels using the conventional definition is much less than that in rock (Buchgraber et al, ; Geistlinger et al, ). The conventional definition is misleading, when using micromodel results to interpret displacements in porous rock.…”

Section: Discussion and Future Workmentioning

confidence: 99%

“…Thus, one is especially likely to misinterpret mobilization in micromodels, based on the value of N ca defined in equation . For instance, capillary numbers around 10 −5 as defined by equation correspond to considerable mobilization in micromodels, for example, S nw of about 10–15% (Buchgraber et al, ; Geistlinger et al, ). This greatly overestimates mobilization implied by similar capillary numbers in geological porous media.…”

Section: Introductionmentioning

confidence: 99%

New Capillary Number Definition for Micromodels: The Impact of Pore Microstructure

Tang

Smit

Vincent-Bonnieu

et al. 2019

Water Resources Research

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A new capillary number (N ca ) definition is proposed for 2-D etched micromodels. We derive the new definition from a force balance on a nonwetting ganglion trapped by capillarity. It incorporates the impact of pore microstructure on mobilization. The geometrical factors introduced can be estimated directly from image analysis of the pore network etched in the micromodel, without conducting flow experiments. The improved fit of the new N ca to published data supports its validity. The new definition yields a consistent trend in the capillary-desaturation curve. The conventional N ca definitions proposed for porous rock give a large scatter in the capillary-desaturation curve for data in micromodels. This is due to the different type of flow in micromodels, as 2-D networks, relative to 3-D geological porous media. In particular, permeability is dominated by channel depth in micromodels with shallow depth of etching, and generally, there is no simultaneous multiphase flow under capillary-dominated conditions. Applying the conventional definitions to results in micromodels may lead to misleading conclusions for fluid transport in geological formations.Plain Language Summary Mobilization or trapping of fluids in porous media, fundamentally, is a result of a force competition. Numerous studies investigate mobilization efficiency using the capillary number (N ca ), which represents a ratio of driving force for mobilization, that is, pressure or hydrostatic effects of gravity, to capillary resistance. The conventional N ca definitions were initially proposed for 3-D porous media, yet many experimental studies use these definitions for 2-D networks. Experimental observations and theoretical analysis show that flow in a 2-D pore network, for example, a microfluidic device, is very different from that in 3-D porous rock. We here propose a new definition of N ca to describe the efficiency of one phase displaced by another in a microfluidic device. The new definition is derived from a force balance on a trapped ganglion. The validity of the new definition is experimentally tested using data from micromodels in the literature. The new N ca definition, as an indicator for mobilization, may be applied to microfluidic studies of a variety of processes across the fields of groundwater, energy, and climate: removal of Nonaqueous Phase Liquid contaminants from aquifers and soils; enhanced recovery of oil in reservoirs; or trapping efficiency of CO 2 in Carbon Capture, Utilization, and Storage.

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“…It should be noted that the capillary numbers for WW and IW are outside the range of applicability for percolation theory (Ca < 10 −6 ) (Geistlinger et al, ). As a result, quantitative predictions from percolation theory (e.g., power‐law predictions of residual ganglia size) are not applicable to this study.…”

Section: Resultsmentioning

confidence: 99%

Wettability Effects on Primary Drainage Mechanisms and NAPL Distribution: A Pore‐Scale Study

Molnar

Gerhard

Willson

et al. 2020

Water Resources Research

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The pore-scale processes governing water drainage behavior in porous media have implications for geoscience multiphase scenarios including carbon capture and storage, contaminant site remediation, oil recovery, and vadose zone processes. However, few studies report directly observed pore-scale water drainage phenomena in 3-D soils. This knowledge gap limits our ability to verify assumptions underlying existing models and develop optimal solutions. This paper utilizes synchrotron X-ray microtomography to present an experimental pore-scale examination of nonaqueous phase liquid (NAPL)/water distribution along a primary drainage front as dense NAPL was injected upward into water wetting (WW) and intermediate wetting (IW) sand-packed columns. Pore-network structures were extracted from imaged data sets and mapped onto segmented NAPL/water data sets which allowed quantitative examinations of wettability impacts on (a) the extent to which NAPL fills individual pore bodies and (b) relationships between pore size and the phase occupying the pore, with both considered as a function of distance (and capillary pressure) relative to the NAPL front. These results revealed that several hypotheses treating IW sand similarly to WW sands are simplistic. IW systems exhibited a sequence of pore filling that deviated from traditional capillary pressure-based model predictions: NAPL invades smaller pores, while larger, adjacent pores are bypassed leaving multipore residual water ganglia. NAPL pore saturations were close to 1 and did not change with capillary pressure in IW systems. Overall, the results illustrate how a relatively small change in operative contact angle alters NAPL distribution during water drainage, with important implications for geoscience multiphase flow scenarios.

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The impact of pore structure and surface roughness on capillary trapping for 2‐D and 3‐D porous media: Comparison with percolation theory

Cited by 63 publications

References 56 publications

Microfluidic Model Porous Media: Fabrication and Applications

Microfluidic Model Porous Media: Fabrication and Applications

New Capillary Number Definition for Micromodels: The Impact of Pore Microstructure

Wettability Effects on Primary Drainage Mechanisms and NAPL Distribution: A Pore‐Scale Study

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