Numerical Evaluation and Interpretation of Measured ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Numerical Evaluation and Interpretation of Measured Effective Dielectric Permittivities during Two Phase Flow in a Porous Medium
Author:Willem-Jan Plug <w.j.plug@citg.tudelft.nl> (Delft University of Technology)
Johannes Bruining <j.bruining@citg.tudelft.nl> (Delft University of Technology)
Evert Slob <e.c.slob@citg.tudelft.nl> (Delft University of Technology)
Ainhoa Gorriti <a.g.gorritiacitg.tudelft.nl> (Delft University of Technology)
Presenter:Willem-Jan Plug <w.j.plug@citg.tudelft.nl> (Delft University of Technology)
Date: 2006-06-18     Track: General Sessions     Session: General
DOI:10.4122/1.1000000607

An experimental procedure is presented where the capillary pressure and the dielectric properties of a porous medium can be measured simultaneously. Our objective is to determine a consistent relationship between capillary pressure versus water saturation and its effect on the effective frequency dependent dielectric permittivity. Applications are found in in-situ subsurface measurements like Ground Penetrating Radar, borehole measurements and logging tools. We have built an experimental set up that can measure capillary pressure under various pressures and temperature conditions. The sample holder is a parallel plate capacitor with stainless steel plates, which also serve as support for the sample. The plates are kept separated by a plastic ring, with an inner diameter of 89 mm that also contains the sample. At the top of the sample holder we measure the oil/gas pressure and at the outlet the water pressure and this pressure difference is defined as the up-scaled capillary pressure. Capillary pressure experiments have already been conducted on sand stone samples where drainage processes were investigated using CO2 and N2. The second part of the experimental procedure is measuring the dielectric permittivity. A precision component analyzer measures the impedance of the capacitor as a function of frequency. The total impedance is directly related to the effective value of the permittivity of the mixture of grains, water and oil/gas present in the capacitor. Preliminary experiments suggest that the best results would be obtained in the frequency range of 0.1 – 3.0 MHz. To evaluate and interpret the measured effective permittivity of the different constituents in the mixture and the influence on their distribution, we make use of mixing laws and numerical models based on Finite Elements and Finite Difference. We will present the results of this study between laboratory measurements and numerical evaluation and interpretation in the resulting paper.