Gas phase trapping and subsequent redistribution in dual-porosity porous media with continuous and discontinuous domains

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F68407700%3A21110%2F16%3A00305791" target="_blank" >RIV/68407700:21110/16:00305791 - isvavai.cz</a>

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Gas phase trapping and subsequent redistribution in dual-porosity porous media with continuous and discontinuous domains

Popis výsledku v původním jazyce

Gas, as a nonwetting phase, is trapped in the porous media at water contents close to the saturation. Trapped gas phase resides in pores in form of bubbles, blobs or clusters forming residual gas saturation. In heterogeneous media, relatively rapid change in the trapped gas distribution can be observed soon after the gas is initially trapped during infiltration. The mass transfer was recently quantified by means of neutron tomography for the case of dual porosity sample under steady state flow. However the underlying mechanism of the gas mass transfer is still not clear. Redistribution of trapped gas was quantitatively studied by 3D neutron imaging in series of experiments conducted on samples composed of fine porous ceramic and coarse sand. The redistribution of water was studied under no-flow and steady state flow conditions. Two different inner geometries of the samples were developed. In the first case the low permeability regions (ceramics) were disconnected, while in the second structure, the fine porosity material was continuous from the top to the bottom of the sample. Air pressure in the sample was monitored in two points. The rate of the redistribution was significantly higher in the case of steady state flow condition in comparison to no-flow conditions. Residual air accumulated preferentially on the interfaces between coarse and fine sands. The transfer from fine to large pores lead to reduced hydraulic conductivity of the sample. Based on the robust experience of visualization of the flow within heterogeneous samples, it seems that due to the huge local (microscopic) pressure gradients between contrasting pore radii the portion of faster flowing water becomes attracted into small pores of high capillary pressure. The process depends on the initial distribution of entrapped air which has to be considered as random in dependence on the history and circumstances of wetting/drying.

Název v anglickém jazyce

Gas phase trapping and subsequent redistribution in dual-porosity porous media with continuous and discontinuous domains

Popis výsledku anglicky

Gas, as a nonwetting phase, is trapped in the porous media at water contents close to the saturation. Trapped gas phase resides in pores in form of bubbles, blobs or clusters forming residual gas saturation. In heterogeneous media, relatively rapid change in the trapped gas distribution can be observed soon after the gas is initially trapped during infiltration. The mass transfer was recently quantified by means of neutron tomography for the case of dual porosity sample under steady state flow. However the underlying mechanism of the gas mass transfer is still not clear. Redistribution of trapped gas was quantitatively studied by 3D neutron imaging in series of experiments conducted on samples composed of fine porous ceramic and coarse sand. The redistribution of water was studied under no-flow and steady state flow conditions. Two different inner geometries of the samples were developed. In the first case the low permeability regions (ceramics) were disconnected, while in the second structure, the fine porosity material was continuous from the top to the bottom of the sample. Air pressure in the sample was monitored in two points. The rate of the redistribution was significantly higher in the case of steady state flow condition in comparison to no-flow conditions. Residual air accumulated preferentially on the interfaces between coarse and fine sands. The transfer from fine to large pores lead to reduced hydraulic conductivity of the sample. Based on the robust experience of visualization of the flow within heterogeneous samples, it seems that due to the huge local (microscopic) pressure gradients between contrasting pore radii the portion of faster flowing water becomes attracted into small pores of high capillary pressure. The process depends on the initial distribution of entrapped air which has to be considered as random in dependence on the history and circumstances of wetting/drying.

Druh

O - Ostatní výsledky

CEP obor

DF - Pedologie

OECD FORD obor

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Projekt

<a href="/cs/project/GA14-03691S" target="_blank" >GA14-03691S: Izotermické a neizotermické proudění vody a transport látek v pórovitém prostředí v blízkosti nasycení</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2016

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů