HR: 0800h
AN: GC51B-1057    [Abstracts]
TI: Evaluation of Seismic Properties and Their Dependence on CO$_2$ Phases in a Porous Sandstone; Insights From Laboratory Injection Experiments
AU: * Kamei, R
EM: kamei@earth.kumst.kyoto-u.ac.jp
AF: Dept. of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University, Yoshida-hon-cho, Sakyo-ku, Kyoto, 606-8501 Japan
AU: Minami, Y
EM: minami@earth.kumst.kyoto-u.ac.jp
AF: Dept. of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University, Yoshida-hon-cho, Sakyo-ku, Kyoto, 606-8501 Japan
AU: Xue, Z
EM: xue@rite.or.jp
AF: Research Institute of Innovative Technology for the Earth, 9-2 Kizugawadai, Kuzu-cho, Soraku-gun, Kyoto, 619-0255 Japan
AU: Matsuoka, T
EM: matsuoka@earth.kumst.kyoto-u.ac.jp
AF: Dept. of Civil and Earth Resources Engineering, Graduate School of Engineering, Kyoto University, Yoshida-hon-cho, Sakyo-ku, Kyoto, 606-8501 Japan
AB: Carbon dioxide (CO$_2$) sequestration in geological formations would be the most straightforward strategy to manage CO$_2$ derived from fossil fuels. For practical sequestration, we need to develop monitoring methods of the underground CO$_2$. Thus, it is essential to understand physical properties of the strata and their dependence on CO$_2$ phases of liquid, gas and supercritical. Since seismic monitoring has been a useful technique, seismic wave responses have priority to be examined. In this study, seismic velocity of a porous sandstone is measured during injection of three different CO$_2$ phases using a tomography method and the results are compared with numerical simulations. The cylindrical rock samples were water-saturated then injected CO$_2$ normal to the bedding plane. Both P- and S- seismic waveforms were acquired using an array of piezoelectric transducers, which were glued to the side-wall of the samples. As the injection proceeds, two basic features can be observed in the waveform; a delay in the arrival time and a strong amplitude attenuation. The magnitude of the delay depends on the phase of the injected CO$_2$. These features suggest that CO$_2$ injection reduces the seismic velocities and increases the elastic viscosity of the sandstone. The observed data can be compared well with synthetic waveforms and this approach makes it possible to analyze the detail effects of injection on the seismic waveforms. In order to visualize the velocity change due to the injection, travel time tomography has also been carried out to the specimen with transducer arrays. The area of the injected CO$_2$ showed a lower value of P- or S- wave velocity and the progressive development of the injecting pathways was examined. These results demonstrate that the 4D seismic method should be a key technology and the phase of subsurface CO$_2$ can also be identified by this technique.
DE: 8180 Tomography
DE: 0910 Data processing
DE: 0935 Seismic methods (3025)
SC: Global Climate Change [GC]
MN: 2004 AGU Fall Meeting