Simultaneous measurement of hysteresis in capillary pressure and electric permittivity for multiphase flow through porous media

We present a tool that simultaneously measures the complex permittivity and the capillary pressure characteristics for multiphase flow. The sample holder is a parallel plate capacitor. A precision component analyzer is used to measure the impedance amplitude and phase angle as a function of frequency (1 kHz to 3 MHz). The complex impedance of the (partially) saturated sample is directly related to the effective complex permittivity. We have conducted main drainage and main imbibition cycles for unconsolidated sand-water-gas (CO2/N2) systems at 8-bar pressure and at temperatures between 27°C and 28°C. Hysteresis in capillary pressure and electric permittivity, as a result of phase distribution, is found between drainage and imbibition for f=3 MHz and becomes more pronounced at higher water saturations. Good agreement of the measured electric permittivity with the complex refractive index model indicates that induced polarization is not observed for 3 MHz and the water saturation is reasonably predicted. The experiments have been performed to study the capillary pressure behavior during CO2 sequestration