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oa Detection of CO2 Plume with Ocean-generated P Waves Recorded on Borehole DAS
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 4th EAGE Workshop on Fiber Optic Sensing for Energy Applications, Aug 2024, Volume 2024, p.1 - 3
Abstract
Active time-lapse seismic is an important tool for monitoring CO2 storage. However, it is expensive and cannot be repeated often. On the other hand, passive seismic methods can utilise ambient noise for monitoring purposes. At CO2CRC Otway International Test Centre (Victoria, Australia), located about 4 km from the shoreline, we collected a very long continuous recording of passive seismic data. Ambient seismic noise was recorded daily using distributed acoustic fibre optic sensors in the ∼1600 m deep injector well for more than 1.5 years before and after injection of CO2. While the 2–20 Hz ambient noise frequency band predominantly consists of not sensitive to CO2 S wave energy, the interferometry can help to focus P wave energy. The correlation of the 1-hour record of the 280-m deep channel with the rest of the receivers produces a virtual shot gather with sufficient P wave energy. Further weighted stacking of 1-hour records improves the signal-to-noise ratio. Data analysis shows an increase in P wave amplitudes after the injection caused by the decrease in the rock’s stiffness in the reservoir due to the presence of CO2. This effect could be utilised for CO2 monitoring along the well.
