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Relationships among air‐water interfacial area, capillary pressure, and water saturation for a sandy porous medium
Author(s) -
Brusseau Mark L.,
Peng Sheng,
Schnaar Gregory,
CostanzaRobinson Molly S.
Publication year - 2006
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2005wr004058
Subject(s) - capillary action , capillary pressure , saturation (graph theory) , tracer , porous medium , materials science , wetting , porosity , capillary number , surface tension , hydrology (agriculture) , mineralogy , composite material , chemistry , geotechnical engineering , geology , thermodynamics , nuclear physics , physics , mathematics , combinatorics
The relationships among air‐water interfacial area, capillary pressure, and water saturation were investigated for a sandy, natural porous medium. Air‐water interfacial areas as a function of water saturation were measured using two methods, gas phase partitioning tracer tests and synchrotron X‐ray microtomography. The tracer test method provides a measure of effective total (capillary and film) interfacial area, whereas microtomography can be used to determine both capillary‐associated and total areas (the latter is the focus of this study). Air‐water interfacial areas determined with both methods increased continuously with decreasing water saturation. The areas measured with the tracer test method were significantly larger than those obtained from microtomography. The maximum values measured with the tracer test method approached the N 2 /BET‐measured specific solid surface area, whereas the maximum values measured by microtomography approached the smooth‐sphere‐calculated specific solid surface area. The interfacial area‐saturation data were combined with capillary pressure‐saturation data obtained from water drainage experiments to examine the relationship between total air‐water interfacial area and capillary pressure. Air‐water interfacial area was observed to increase monotonically with increasing capillary pressure and then to plateau at values that correspond to areas associated with residual water saturation. These results are consistent with previously reported theoretically and computationally based analyses of functional relationships between total nonwetting‐wetting interfacial area and capillary pressure.