DASパッシブ記録を用いた浅部モニタリングの検討

抄録

In this paper, we focused on distributed acoustic sensing（DAS）surface wave records excited by ambient noise（e.g. ocean waves and human activities）to study the possibility of shallow monitoring for carbon capture and storage（CCS）projects. First, we estimated the change in phase velocity based on some assumed leakage cases by modeling. In addition, we modeled the surface wave records for different lengths of receiver lines to study the monitoring depth sensitivity qualitatively. Using the field DAS passive records, we studied the stability of the phase velocity estimation during periods without events such as CCS injection. We also compared the difference between the phase velocity estimation methods and the difference between DAS records or geophone records. Through the modeling and the field data analysis, we found that we could estimate the phase velocity stably enough. It might suggest the possibility of leakage detection by surface waves. However, we should note that the phase velocity change in modeling depends on our assumptions, such as porosity or CO₂ saturation. Moreover, it might be desirable to discuss the stability of phase velocity estimation using a longer period of data（e.g. 1 year）.