Robust body-wave retrieval from ambient-noise seismic interferometry using crosscoherence applied to model and field examples of CO2 sequestrationHaitao Cao

We applied seismic interferometry using cross-correlation and cross-coherence to numerically modelled ambient noise to base and repeat surveys for the retrieval of body-wave reflections in order to characterize changes of a reservoir resulting from CO2 sequestration. In order to simulate realistic scenarios, we added random noise trace-by-trace to the recorded ambient noise that was used as a “signal”. We considered two random-noise scenarios; (i) random noise was added to the data where each receiver has a unique and random “signal”-to-noise ratio (ii) random noise increasing in amplitude across the array. Under all of these scenarios, we found that the cross-coherence approach retrieved body-waves more effectively and provided better images than the cross-correlation approach. We also applied both cross-correlation and cross-coherence to 28.7 hours of recorded field data acquired at a CO2 storage site at Ketzin, Germany, and found that cross-coherence provided better retrieval of body-wave reflections from this data set. We conclude that cross-coherence interferometry can be a useful tool for time-lapse monitoring studies and for ambient-noise data contaminated by additional random noise