Publication Date:
2013-09-10
Description:
In order to monitor injected carbon dioxide (CO 2 ), simultaneous measurements of seismic velocity and electrical resistivity are employed during the drainage (CO 2 injection) and imbibition (water injection) processes of a Berea sandstone. Supercritical CO 2 (10 MPa at 40 ºC) was injected into a water-saturated Berea sandstone in the drainage stage and monitored via simultaneous measurements. After the injection of supercritical CO 2 , fresh distilled water was injected into the CO 2 -injected sandstone during the imbibition stage. Electrical resistivity and P -wave velocity measurements acquired during the drainage and imbibition stages were employed to evaluate CO 2 saturations ( S CO 2 ) based on the resistivity index and the Gassmann fluid-substitution equations, respectively. Comparing estimated values for S CO 2 saturation against those from volume-derived S CO 2 , based on analysis on injected and drained fluid volumes in the drainage process, we conclude that Gassmann–Brie and resistivity index are suitable for the evaluation based on P -wave velocity and electrical resistivity, respectively. R t -based estimation properly tracks the variation in S CO 2 even when S CO 2 is large (〉0.15), while V p -based estimation is sensitive to the variation in S CO 2 when S CO 2 is small (〈0.1). Employing the Gassmann–Brie and resistivity index, estimation of variation in S CO 2 based on the simultaneous measurements provides the upper and lower bounds of S CO 2 even when S CO 2 is large (〉0.1), while properly estimating S CO 2 when S CO 2 is small (〈0.1). Monitoring the CO 2 imbibition process confirms residual CO 2 saturation within the sample.
Print ISSN:
0956-540X
Electronic ISSN:
1365-246X
Topics:
Geosciences
Published by
Oxford University Press
on behalf of
The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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