Measurement of electrical impedance and P-wave velocity of a low permeable sandstone core during the displacement of saturated brine by CO2 injection

Evaluating and monitoring the CO2 behavior in the reservoir, understanding the mechanism of CO2 flow and distribution in the water-CO2 mixture state is essential. In this study, measurement of the complex electrical impedance (Z) and P-wave velocity (V-p) is conducted during the CO2 injection into the rock core under the reservoir condition. Specimen is low permeable sandstone and injection rate is ultra-low (in the low capillarity number (C-n) area) to high. In addition to measuring Z and V-p, differential pressure on the both sides of the specimen and CO2 saturation (S-CO2) of the entire specimen are measured. The change of Z and Vp are observed according to the change of differential pressure and S-CO2. After the injection test, SCO2 in cross-section of the specimen is estimated using Archie's law and Gassmann's equation (Patchy saturation model) to the experimental results. (C) 2017 The Authors. Published by Elsevier Ltd.