Geometrically derived efficiency of slow immiscible displacement in porous media

Berg, Carl Fredrik; Slotte, Per Arne; Khanamiri, Hamid Hosseinzade

doi:10.1103/physreve.102.033113

Cited by 11 publications

(7 citation statements)

References 39 publications

(67 reference statements)

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“…The dynamics of slow displacement in porous media has been observed to occur in an intermittent manner by so called Haines jumps [59,[62][63][64][65][66][67][68][69][70][71][72]. The invasion percolation model [55][56][57] describes well the structure of slow displacement in porous media [22], but it does not describe the dynamics realistically because the invasion is limited to one pore at a time.…”

Section: Introductionmentioning

confidence: 99%

Burst Dynamics, Upscaling and Dissipation of Slow Drainage in Porous Media

et al. 2021

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We present a theoretical and experimental investigation of drainage in porous media. The study is limited to stabilized fluid fronts at moderate injection rates, but it takes into account capillary, viscous, and gravitational forces. In the theoretical framework presented, the work applied on the system, the energy dissipation, the final saturation and the width of the stabilized fluid front can all be calculated if we know the dimensionless fluctuation number, the wetting properties, the surface tension between the fluids, the fractal dimensions of the invading structure and its boundary, and the exponent describing the divergence of the correlation length in percolation. Furthermore, our theoretical description explains how the Haines jumps’ local activity and dissipation relate to dissipation on larger scales.

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Section: Introductionmentioning

confidence: 99%

Burst Dynamics, Upscaling and Dissipation of Slow Drainage in Porous Media

et al. 2021

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“…(with contact angle θ ≈ 0 • for a water-wet system and radius r = d/2) for a water-wet system as p c = 0.017 bar for pore bodies and p c = 0.04 bar for pore throats, which are also typical values for the pressure fluctuations in the steady-state experiment in Figures 2-5 (the maximum fluctuations can be a factor 3-4 larger but for most f w the range is very similar) (Berg C. F. et al, 2020). This suggests that the pressure fluctuations are likely caused by events on the capillary energy scale, which are typically pore scale events.…”

Section: Energy Scale Of Fluctuationsmentioning

confidence: 55%

“…Pore scale experiments (DiCarlo et al, 2003;Moebius and Or, 2012;Berg et al, 2013Berg et al, , 2014Armstrong et al, 2014a;Reynolds et al, 2017;Lin Q. et al, 2018;Lin et al, 2019a) and numerical simulations (Lenormand et al, 1983;Raeini et al, 2014;Armstrong et al, 2015;Guédon et al, 2017;Alpak et al, 2019;Berg C. F. et al, 2020;Winkler et al, 2020) also exhibit fluctuations in pressure and saturation (Ramstad and Hansen, 2006;Pak et al, 2015), which are caused by pore scale displacement events, such as Haines jumps and coalescence (Rücker et al, 2015b), where the non-wetting phase replaces the wetting phase and snap-off and pistonlike displacement (Lenormand et al, 1983;Dixit et al, 1998), where the wetting phase replaces the non-wetting phase. These events lead to interruption and rearrangement of the connected pathways the respective phases flow through (Tuller and Or, 2001) and are described by a rigorous theoretical framework of pore-scale thermodynamics (Morrow, 1970).…”

Section: Introductionmentioning

confidence: 99%

The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media

et al. 2021

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Core flooding experiments to determine multiphase flow in properties of rock such as relative permeability can show significant fluctuations in terms of pressure, saturation, and electrical conductivity. That is typically not considered in the Darcy scale interpretation but treated as noise. However, in recent years, flow regimes that exhibit spatio-temporal variations in pore scale occupancy related to fluid phase pressure changes have been identified. They are associated with topological changes in the fluid configurations caused by pore-scale instabilities such as snap-off. The common understanding of Darcy-scale flow regimes is that pore-scale phenomena and their signature should have averaged out at the scale of representative elementary volumes (REV) and above. In this work, it is demonstrated that pressure fluctuations observed in centimeter-scale experiments commonly considered Darcy-scale at fractional flow conditions, where wetting and non-wetting phases are co-injected into porous rock at small (<10−6) capillary numbers are ultimately caused by pore-scale processes, but there is also a Darcy-scale fractional flow theory aspect. We compare fluctuations in fractional flow experiments conducted on samples of few centimeters size with respective experiments and in-situ micro-CT imaging at pore-scale resolution using synchrotron-based X-ray computed micro-tomography. On that basis we can establish a systematic causality from pore to Darcy scale. At the pore scale, dynamic imaging allows to directly observe the associated breakup and coalescence processes of non-wetting phase clusters, which follow “trajectories” in a “phase diagram” defined by fractional flow and capillary number and can be used to categorize flow regimes. Connected pathway flow would be represented by a fixed point, whereas processes such as ganglion dynamics follow trajectories but are still overall capillary-dominated. That suggests that the origin of the pressure fluctuations observed in centimeter-sized fractional flow experiments are capillary effects. The energy scale of the pressure fluctuations corresponds to 105-106 times the thermal energy scale. This means the fluctuations are non-thermal. At the centimeter scale, there are non-monotonic and even oscillatory solutions permissible by the fractional flow theory, which allow the fluctuations to be visible and—depending on exact conditions—significant at centimeter scale, within the viscous limit of classical (Darcy scale) fractional flow theory. That also means that the phenomenon involves both capillary aspects from the pore or cluster scale and viscous aspects of fractional flow and occurs right at the transition, where the physical description concept changes from pore to Darcy scale.

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“…An analytical expression for u w in unsaturated hydrophobic soil can be derived by quantifying the change of free surface energy due to external work. The pressure of non-wetting water phase (P w ) during infiltration results in an increase in the soil water content (Δθ w ) and thereby changes the interfacial energies (E IE ) between soil-air-water phases (Berg et al, 2020), which can be expressed as:…”

Section: Effective Stress Of Unsaturated Soil With Varied Wettabilitymentioning

confidence: 99%

Effects of Bed Hydrophobicity on Post‐Fire Debris Flow Entrainment and Momentum Growth

Zheng

Liu

et al. 2022

JGR Earth Surface

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Forest wildfires leave vast areas with burned topsoil that is water repellent, susceptible to erosion by surface runoff and a potential source of debris flow. To mitigate post‐fire debris flow hazards, debris resisting barriers are usually constructed in the flow path. However, the fundamental interaction mechanisms of debris flow on a water repellent bed and the momentum exchange process that governs the destructive potential of debris flows have yet to be elucidated. This study investigates the influence of bed sediment hydrophobicity on entrainment by debris flows and the impact force on a downstream barrier using a series of physical flume tests. Bed sediment with increasing contact angles (50°–130°) were used to model bed hydrophobicity from wettable to hydrophobic conditions, and volumetric water content (0%–30%) to simulate the natural unsaturated condition after rainfall in fire‐burned hillslopes. Compared to a wettable bed, a hydrophobic bed exhibits a failure pattern with slab‐by‐slab entrainment and en masse failure with a sixfold increase in the average erosion depth. A new dimensionless number is proposed to quantify the effects of contact angle on soil erosion. The flow momentum increases up to 21% after entrainment of hydrophobic bed compared to non‐erodible bed. The peak impact force on the downstream barrier can increase up to 80% for hydrophobic bed as a consequence of momentum gains after entrainment. The hydrodynamic coefficient for estimating impact force reveals the inadequacy of current design criteria of debris resisting barriers for fire‐prone vegetated hillslopes, suggesting further investigations are needed.

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Geometrically derived efficiency of slow immiscible displacement in porous media

Cited by 11 publications

References 39 publications

Burst Dynamics, Upscaling and Dissipation of Slow Drainage in Porous Media

Burst Dynamics, Upscaling and Dissipation of Slow Drainage in Porous Media

The Origin of Non-thermal Fluctuations in Multiphase Flow in Porous Media

Effects of Bed Hydrophobicity on Post‐Fire Debris Flow Entrainment and Momentum Growth

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