Pore-scale micro-computed-tomography imaging: Nonwetting-phase cluster-size distribution during drainage and imbibition

Georgiadis, Apostolos; Berg, Steffen; Makurat, A.; Maitland, Geoffrey C.; Ott, Holger

doi:10.1103/physreve.88.033002

Cited by 96 publications

(87 citation statements)

References 36 publications

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“…Based on the dry scan and fully brine‐saturated image shown in Figure 4a1 and 4a2, some subresolution pores exist in Bentheimer: this has also been observed even in bead packs (Georgiadis et al, 2013). As Figure 4b shows, the grey regions, indicated by the yellow boxes, are dark in the differential image (Figure 4a) which confirms that oil does not enter these regions.…”

Section: Resultsmentioning

confidence: 87%

X‐ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method

Gao

Lin

Bijeljic

et al. 2017

Water Resources Research

100

112

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We imaged the steady state flow of brine and decane in Bentheimer sandstone. We devised an experimental method based on differential imaging to examine how flow rate impacts impact the pore‐scale distribution of fluids during coinjection. This allows us to elucidate flow regimes (connected, or breakup of the nonwetting phase pathways) for a range of fractional flows at two capillary numbers, Ca, namely 3.0 × 10−7 and 7.5 × 10−6. At the lower Ca, for a fixed fractional flow, the two phases appear to flow in connected unchanging subnetworks of the pore space, consistent with conventional theory. At the higher Ca, we observed that a significant fraction of the pore space contained sometimes oil and sometimes brine during the 1 h scan: this intermittent occupancy, which was interpreted as regions of the pore space that contained both fluid phases for some time, is necessary to explain the flow and dynamic connectivity of the oil phase; pathways of always oil‐filled portions of the void space did not span the core. This phase was segmented from the differential image between the 30 wt % KI brine image and the scans taken at each fractional flow. Using the grey scale histogram distribution of the raw images, the oil proportion in the intermittent phase was calculated. The pressure drops at each fractional flow at low and high flow rates were measured by high‐precision differential pressure sensors. The relative permeabilities and fractional flow obtained by our experiment at the mm‐scale compare well with data from the literature on cm‐scale samples.

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Section: Resultsmentioning

confidence: 87%

X‐ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method

Gao

Lin

Bijeljic

et al. 2017

Water Resources Research

100

112

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“…In this definition, the nonwetting phase would become mobilized by the viscous shear forces imposed on it by the wetting phase flow field, acting on the interface over the same length scale as the capillary forces. However, for desaturation, mobilization of the trapped nonwetting ganglia, which can extend over many pores ranging up to and potentially greater than millimeters [Georgiadis et al, 2013], occurs because of the viscous shear over the whole cluster interface, which is equivalent to the viscous pressure drop created by the flow field of the wetting phase, and capillary forces act over the length scale of a pore throat which is typically on the order of a few micrometers. In other words, the definition of Ca micro assumes that viscous and capillary forces act over the same length scale and omits the configuration of the trapped nonwetting phase topology.…”

Section: Introductionmentioning

confidence: 99%

Critical capillary number: Desaturation studied with fast X‐ray computed microtomography

Armstrong

Georgiadis

Ott

et al. 2014

Geophysical Research Letters

152

105

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[1] For subsurface flow, the correct definition for the balance of viscous and capillary forces, the so-called capillary number (Ca), which predicts the mobilization of nonwetting phase, has been a long-standing controversy. The most common microscopic definition results in nonwetting phase mobilization at Ca~10 À5, which is counterintuitive. Rather, mobilization should occur at Ca ≥ 1. As demonstrated herein, by using fast synchrotronbased X-ray computed microtomography and averaging of thereby accessible pore-scale parameters to macroscale values, a macroscale Ca definition is validated and shown to correctly describe mobilization at Ca~1. The presented methodology provides a connection between desaturation and pore-scale fluid topology and gives insight into when and how Ca changes with system size. The broader implication implies that it makes a difference whether desaturation is driven by an increase in flow rate or viscosity or decrease in interfacial tension since Ca incorporates nonwetting phase cluster length, which is process-dependent.

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“…All types of flow have been observed experimentally in model porous media Payatakes, 1995, 1999;Tsakiroglou et al, 2007;Tallakstad et al, 2009;Krummel et al, 2013;Armstrong et al, 2016) as well as in real porous media (Van de Merwe and Nicol, 2009;Georgiadis et al, 2013;Oughanem et al, 2015;Rücker et al, 2015).…”

Section: The Concept Of Decomposition Into Prototype Flows (Deprof)mentioning

confidence: 80%

“…Apart from laboratory studies, virtual studies, implementing dynamic pore network simulations Payatakes, 1996 andAlGharbi and Blunt, 2005;Nguyen et al, 2006), or lattice Boltzmann methods (Pan et al, 2004;Ghassemi and Pak, 2011;Ramstad et al, 2012;Armstrong et al, 2016), have also addressed disconnected-oil flow modes. With recent advances in imaging technology, these flows are observed in real porous media as well (Georgiadis et al, 2013;Oughanem et al, 2015;Rücker et al, 2015). The observed flow structures show a significant and À presumably À systematic mutation ranging from practically no oil-flow, to large and small oil ganglion dynamics, to drop traffic and connected pathway flow mixtures, depending À primary À on the flow conditions and À secondary À on the physicochemical, size and network configuration of the oil-water-p.m. system Payatakes, 1995 and1999;Krummel et al, 2013;Armstrong et al, 2016).…”

Section: Introductionmentioning

confidence: 96%

Oil Fragmentation, Interfacial Surface Transport and Flow Structure Maps for Two-Phase Flow in Model Pore Networks. Predictions Based on Extensive, DeProF Model Simulations

Valavanides

2018

Oil & Gas Science and Technology - Rev. IFP Energies nouvel

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-In general, macroscopic two-phase flows in porous media form mixtures of connectedand disconnected-oil flows. The latter are classified as oil ganglion dynamics and drop traffic flow, depending on the characteristic size of the constituent fluidic elements of the non-wetting phase, namely, ganglia and droplets. These flow modes have been systematically observed during flow within model pore networks as well as real porous media. Depending on the flow conditions and on the physicochemical, size and network configuration of the system (fluids and porous medium), these flow modes occupy different volume fractions of the pore network. Extensive simulations implementing the DeProF mechanistic model for steady-state, one-dimensional, immiscible twophase flow in typical 3D model pore networks have been carried out to derive maps describing the dependence of the flow structure on capillary number, Ca, and flow rate ratio, r. The model is based on the concept of decomposition into prototype flows. Implementation of the DeProF algorithm, predicts key bulk and interfacial physical quantities, fully describing the interstitial flow structure: ganglion size and ganglion velocity distributions, fractions of mobilized/stranded oil, specific surface area of oil/water interfaces, velocity and volume fractions of mobilized and stranded interfaces, oil fragmentation, etc. The simulations span 5 orders of magnitude in Ca and r. Systems with various viscosity ratios and intermediate wettability have been examined. Flow of the nonwetting phase in disconnected form is significant and in certain cases of flow conditions the dominant flow mode. Systematic flow structure mutations with changing flow conditions have been identified. Some of them surface-up on the macroscopic scale and can be measured e.g. the reduced pressure gradient. Other remain in latency within the interstitial flow structure e.g. the volume fractions of À or fractional flows of oil through À connected-disconnected flows. Deeper within the disconnected-oil flow, the mutations between ganglion dynamics and drop traffic flow prevail. Mutations shift and/or become pronounced with viscosity disparity. They are more evident over variables describing the interstitial transport properties of process than variables describing volume fractions. This characteristic behavior is attributed to the interstitial balance between capillarity and bulk viscosity. Mean mobilization probability of i-class ganglia S 2.3 IFP Energies nouvelles International Conference Rencontres Scientifiques d'IFP Energies nouvellesNumber density of i-class ganglia S (15)Number of pore unit cells occupied by each i-class ganglion P

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Pore-scale micro-computed-tomography imaging: Nonwetting-phase cluster-size distribution during drainage and imbibition

Cited by 96 publications

References 36 publications

X‐ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method

X‐ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method

Critical capillary number: Desaturation studied with fast X‐ray computed microtomography

Oil Fragmentation, Interfacial Surface Transport and Flow Structure Maps for Two-Phase Flow in Model Pore Networks. Predictions Based on Extensive, DeProF Model Simulations

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