Fault Zone Characterization and Monitoring of CO2 Storage using Full Waveform Inversion

Abstract

CO2 storage in geological formations is essential to limit global warming and reduce the effects of climate change. In order to store CO2 safely and prevent leakage, proper sealing mechanisms are required. Faults are complex zones of damaged material and play an important role in managing fluid migration. In particular, they can act as sealing barriers or migration pathways. Therefore, storage of CO2 near fault zones requires accurate and careful seismic monitoring. Seismic monitoring can be done using imaging or full waveform inversion (FWI). The latter should in principle be more accurate but is more computationally expensive. In this study, imaging and full waveform inversion, using the ray-Born approximation for the forward modeling, are used to study characterization of fault zones and CO2 saturation in and near faults. For this purpose, various fault zone models with and without CO2 are created. The results show that full waveform inversion is superior to imaging for determination of fault zone structure. Furthermore, the full waveform inversion also estimates the velocity changes due to CO2 saturation more accurately than imaging. These synthetic results suggests that full waveform inversion should be used on real data, rather than imaging, when estimating fault zone structure and the effects of CO2 storage.