HR: 16:00h
AN: H44A-01 INVITED    [Abstracts]
TI: Experimental Evidence That Electric Permittivity is a Measure of Interfacial Area in Unconsolidated Sand
AU: * Slob, E
EM: e.c.slob@tudelft.nl
AF: Department of Geotechnology, Stevinweg 1, Delft, 2628CN, Netherlands
AU: Plug, W
EM: willemjan@horizon-ep.com
AF: Horizon Energy Partners BV, Prinses Margrietplantsoen 81, Den Haag, 2595 BR, Netherlands
AU: Bruining, H
EM: j.bruining@tudelft.nl
AF: Department of Geotechnology, Stevinweg 1, Delft, 2628CN, Netherlands
AB: An experimental tool is presented with which the capillary pressure and the electric permittivity of a porous medium can be measured simultaneously. The equipment is designed to conduct measurements for the unconsolidated sand-distilled water-gas system for pressures up to 20 bar and constant temperature conditions. The bulk phase pressures of the gas and the water are measured at the top and bottom of the sample holder. Also the pressure difference between these points is measured, which is taken as the capillary pressure. The sample holder is a parallel plate capacitor with stainless steel plates, which also serves as support for the sample. The measured total impedance is directly related to the effective value of the complex dielectric constant of the sample. Using this tool, the relation between capillary pressure and electric behavior has been investigated by measuring them simultaneously as function of the water saturation. The excess electric coefficient is postulated to be a measure for the interfacial area. Consequently, our set-up measures simultaneously the capillary pressure and the interfacial area. Drainage and imbibition experiments have been conducted for sand-distilled water-gas systems. The main capillary cycles and the scanning curves show hysteresis with the drainage curves showing higher values than the imbibition curves. The 100 kHz permittivity data also show hysteresis between drainage and imbibition. Furthermore non-monotonic behavior is observed, which is analogous to the interfacial characteristics obtained from network and micro-pore models. The permittivity behavior is attributed to polarization of the gas-water and water-solid interfaces. The permittivity hysteresis is provoked by the different phase distributions and geometries. Our results show that the capillary pressure is a unique function of the permittivity and water saturation, and therefore this work provides further evidence that the permittivity is a measure for the interfacial area.
DE: 1828 Groundwater hydraulics
DE: 1829 Groundwater hydrology
DE: 1846 Model calibration (3333)
DE: 1894 Instruments and techniques: modeling
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting