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Indexed by:Journal Papers

Date of Publication:2015-12-01

Journal:JOURNAL OF APPLIED GEOPHYSICS

Included Journals:SCIE、EI、Scopus

Volume:123

Page Number:50-62

ISSN No.:0926-9851

Key Words:Berea sandstone; Oil saturation; Saturation exponent; X-ray CT; Complex electrical impedance

Abstract:Complex electrical impedance measurements were performed on a brine-saturated Berea sandstone core while oil and CO2 were injected at different pressures and temperatures. The saturations of brine, oil, and CO2 in the core were simultaneously estimated using an X-ray computed tomography scanner. The formation factor of this Berea core and the resistivity indexes versus the brine saturations were calculated using Archie's law. The experimental results found different flow patterns of oil under different pressures and temperatures. Fingers were observed for the first experiment at 10 MPa and 40 degrees C. The fingers were restrained as the viscosity ratio of oil and water changed in the second (10 MPa and 25 degrees C) and third (5 MPa and 25 degrees C) experiments. The resistivity index showed an exponential increase with a decrease in brine saturation. The saturation exponent varied from 1.4 to 4.0 at different pressure and temperature conditions. During the oil injection procedure, the electrical impedance increased with oil saturation and was significantly affected by different oil distributions; therefore, the impedance varied whether the finger was remarkable or not, even if the oil saturation remained constant. During the CO2 injection steps, the impedance showed almost no change with CO2 saturation because the brine in the pores became immobile after the oil injection. (C) 2015 Elsevier B.V. All rights reserved.