CCS Technologies for low carbon society

[1601-04-03] Continuous and accurate monitoring system for injected CO2

○Takeshi Tsuji¹, Tatsunori Ikeda¹, Yuichiro Nagata¹ (1. Kyushu University)

Chairman: Tetsuya Suekane (Tokyo Institute of Technology)

Keywords:CO2 geological storage, Monitoring, Seismic method

We have developed a monitoring method for injected CO₂ using a continuous and controlled seismic source. The continuous source system was originally developed for earthquake or volcano monitoring. We optimized the system for monitoring of injected CO2. To apply this system for injected CO₂ monitoring, we used higher frequency range as a source signal. We improved temporal resolution and accuracy of the monitoring by using surface-waves. Our monitoring system could be cost-effective with high temporal resolution, compared to conventional monitoring. Our field experiments show that hourly-variation of surface-wave velocity could be monitored with better than 1 % accuracy. This temporal stability allows the possibility to detect changes in seismic velocities associated with CO₂ leakage through the fault zone. Recently we have applied this monitoring technique in the ongoing CCS project, and we clearly found seasonal variation of seismic velocities in shallow sediments due to freezing effects of saturated water.