SEGJ Technical Conference

Spatial and temporal variation of surface-wave phase velocity in the Aquistore CO2 storage site using a single seismic ACROSS

Abstract We studied spatial and temporal variations of the shallow subsurface at the Aquistore CO2 storage site from surface-wave analysis. To improve temporal resolution and source repeatability in the monitoring, we used seismic ACROSS. We applied spatial windows for surface-wave analysis to improve spatial resolution of phase velocity estimation. Lateral variations of the estimated phase velocities were mostly consistent with the shallow geological conditions. As a result of monitoring, we identified seasonal variation of phase velocities, possibly related to the freezing of water in shallow sediments or change in higher mode energy. This result suggests that monitoring results of deep CO2 injection reservoirs using seismic reflection would be affected by the seasonal variation of the shallow subsurface. In warmer seasons, our monitoring approach indicated high temporal stability, which may be used to identify the spatial distribution of CO2 leakage.