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

Autor: Iman Ataei-Dadavi, Hans-Jörg Vogel, Sadjad Mohammadian, Helmut Geistlinger
Rok vydání: 2015
Předmět:
Zdroj: Water Resources Research. 51:9094-9111
ISSN: 1944-7973
0043-1397
Popis: We study the impact of pore structure and surface roughness on capillary trapping of nonwetting gas phase during imbibition with water for capillary numbers between 10−7 and 5 × 10−5, within glass beads, natural sands, glass beads monolayers, and 2-D micromodels. The materials exhibit different roughness of the pore-solid interface. We found that glass beads and natural sands, which exhibit nearly the same grain size distribution, pore size distribution, and connectivity, showed a significant difference of the trapped gas phase of about 15%. This difference can be explained by the microstructure of the pore-solid interface. Based on the visualization of the trapping dynamics within glass beads monolayers and 2-D micromodels, we could show that bypass trapping controls the trapping process in glass beads monolayers, while snap-off trapping controls the trapping process in 2-D micromodels. We conclude that these different trapping processes are the reason for the different trapping efficiency, when comparing glass beads packs with natural sand packs. Moreover, for small capillary numbers of 10−6, we found that the cluster size distribution of trapped gas clusters of all 2-D and 3-D porous media can be described by a universal power law behavior predicted from percolation theory. This cannot be expected a priori for 2-D porous media, because bicontinuity of the two bulk phases is violated. Obviously, bicontinuity holds for the thin-film water phase and the bulk gas phase. The snap-off trapping process leads to ordinary bond percolation in front of the advancing bulk water phase and is the reason for the observed universal power law behavior in 2-D micromodels with rough surfaces.
Databáze: OpenAIRE
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