Direct gas injection into saturated glass beads: Transition from incoherent to coherent gas flow pattern

Geistlinger, Helmut; Krauss, Gunnar; Lazik, Detlef; Luckner, L.

doi:10.1029/2005wr004451

Cited by 71 publications

(110 citation statements)

References 21 publications

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“…In both cases, gas escapes from a saturated granular matrix-seafloor sediments for pockmarks or dense particle suspension for mud volcanoes. Extensive modeling for gas injection in a saturated, rigid porous medium has been performed in the last 20 years, both with and without the presence of heterogeneities in the system (see for instance [2,[30][31][32][33][34][35], a tentative phase diagram by Geistlinger et al [36], and references within). When the medium is deformable, however, complex patterns may arise from the interaction between the fluid flow and the grains motion [37,38].…”

Section: Introductionmentioning

confidence: 99%

Flow and fracture in water-saturated, unconstrained granular beds

et al. 2015

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The injection of gas in a liquid-saturated granular bed gives rise to a wide variety of invasion patterns. Many studies have focused on constrained porous media, in which the grains are fixed in the bed and only the interstitial fluid flows when the gas invades the system. With a free upper boundary, however, the grains can be entrained by the ascending gas or fluid motion, and the competition between the upward motion of grains and sedimentation leads to new patterns. We propose a brief review of the experimental investigation of the dynamics of air rising through a water-saturated, unconstrained granular bed, in both two and three dimensions. After describing the invasion pattern at short and long time, a tentative regime-diagram is proposed. We report original results showing a dependence of the fluidized zone shape, at long times, on the injection flow rate and grain size. A method based on image analysis makes it possible to detect not only the fluidized zone profile in the stationary regime, but also to follow the transient dynamics of its formation. Finally, we describe the degassing dynamics inside the fluidized zone, in the stationary regime. Depending on the experimental conditions, regular bubbling, continuous degassing, intermittent regime or even spontaneous flow-to-fracture transition are observed.

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Section: Introductionmentioning

confidence: 99%

Flow and fracture in water-saturated, unconstrained granular beds

et al. 2015

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“…The coordination number of glass beads (i.e., the average number of contacts to neighboring glass beads) within a random packing of the bulk sediment is about Z = 8.5 (Geistlinger et al 2006) while this number is reduced at the flow cell wall to about Z = 6. Busch et al (1993) classified the relative pore-throat aperture ξ k,min = d k,min /d k where d k,min is the diameter of a sphere touching the glass beads inside a pore throat.…”

Section: Comparison Of Gravimetric and Optical Methodsmentioning

confidence: 99%

“…Out of special interest for understanding of large-scale phase displacement are quantitative analyses of the local (porescale) gas-phase dynamics. Depending on the structural properties of the porous matrix and the applied gas flow, the following typical gas flow patterns may occur: From fine to coarse sand a transition from dense capillary networks, channelized flow, slug or macro-cluster flow, and finally bubbly flow is observed (Geistlinger et al 2006). Such descriptions of flow patterns mainly reflect their geometrical characteristics without a direct link to the underlying pore-scale processes.…”

Section: Introductionmentioning

confidence: 96%

Multi-scale Optical Analyses of Dynamic Gas Saturation During Air Sparging into Glass Beads

et al. 2007

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A multi-scale optical imaging technique was developed allowing for the 2D observation of two phase flow in porous media at two different scales simultaneously: Using two coupled cameras, a 2D flow cell (0.5×0.5 m 2 ) is recorded entirely at the bench scale and at the pore scale with a spatial resolution of 0.5 and 0.01 mm, respectively. The technique is applied to study channelized gas flow in saturated glass beads. We analyze the phase distribution at the pore scale and derive a pixel-based method for the measurement of saturation at the larger scale. This method assumes linearity between the mean reflected light intensity and the local gas saturation if averaging is performed over representative areas (REV). The REV depends on the irregularity of the local pore structure and has a lower limit at the correlation length of the porous medium (somewhat above the size of the glass beads) and an upper limit which correlates with the width of gas channels. These limits could be quantified through optical analysis. The optical approach to estimate phase saturations was validated by gravimetric analysis where a characteristic ratio between the optically observed flow cell wall and the saturation within the bulk material was identified, which corresponds to the expectation based on geometrical considerations of the glass bead packing. Considering a transient flow experiment the optical method is demonstrated to be able to quantify the temporal evolution of the residual and the convective gas phase. We conclude that the new technique provides a valuable tool to improve our quantitative understanding of multiphase phenomena across different scales.

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“…We have discussed such stochastic gas-water pattern for gas injection into saturated homogeneous sediments (see Geistlinger et al, 2006). Since both BMT and gas transport through the unsaturated zone are dependent on the stochastic nature of the connected network of gas-filled macropores, the gas-emission pattern should exhibit a high spatial and temporal variability.…”

Section: Oxygen Measurementsmentioning

confidence: 99%

Spatial and temporal variability of dissolved nitrous oxide in near‐surface groundwater and bubble‐mediated mass transfer to the unsaturated zone

Geistlinger

Jia

Eisermann

et al. 2010

Z. Pflanzenernähr. Bodenk.

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Understanding spatial and temporal variability of dissolved nitrous oxide (N 2 O) is essential to process understanding of N 2 O emissions from near-surface groundwater to the unsaturated zone and to the atmosphere. We propose a conceptual model of bubble-mediated mass transfer within the exchange zone defined by the range of groundwater fluctuations. Based on this model, we discuss our experimental data collected over a period of 2 years from of a small-scale test site (6.5 m × 2.5 m × 5 m, 20 observation wells), where we measured the dissolved gases N 2 O and O 2 at five different depths ( 0.1, 0.5, 0.8, 1.5, and 2.5 m below groundwater level). We show by visualization of the spatially interpolated data and by descriptive statistics that the N 2 O concentration of near-surface groundwater exhibits a significant anticorrelation to O 2 concentration, a spatial coefficient of variation up to 260%, and a spatial-correlation range at the meter-scale. The temporal variation of the spatially averaged data is correlated to the temporal variation of the averaged groundwater level. The implications of high spatial and temporal variability on gradient-based flux models like the steady state-flat interface model usually used in literature are discussed. Our main conclusion is that both the steady-state assumption and the flat-interface model are far from being realistic, because of (1) the highly transient behavior of the exchange zone and (2) the oversimplification of the gas-water interface that underestimates mass transfer by order of magnitudes compared to bubble-mediated mass transfer.

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Direct gas injection into saturated glass beads: Transition from incoherent to coherent gas flow pattern

Cited by 71 publications

References 21 publications

Flow and fracture in water-saturated, unconstrained granular beds

Flow and fracture in water-saturated, unconstrained granular beds

Multi-scale Optical Analyses of Dynamic Gas Saturation During Air Sparging into Glass Beads

Spatial and temporal variability of dissolved nitrous oxide in near‐surface groundwater and bubble‐mediated mass transfer to the unsaturated zone

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