Studying CO<inf>2</inf> storage with ambient-noise seismic interferometry: A combined numerical feasibility study and field-data example for Ketzin, Germany

Seismic interferometry applied to ambient-noise measurements allows the retrieval of the seismic response between pairs of receivers. We studied ambient-noise seismic interferometry (ANSI) to retrieve time-lapse reflection responses from a reservoir during CO<inf>2</inf> geologic sequestration, using the case of the experimental site of Ketzin, Germany. We applied ANSI to numerically modeled data to retrieve base and repeat reflection responses characterizing the impedances occurring at the reservoir both with and without the injection of CO<inf>2</inf>. The modeled data represented global transmission responses from band-limited noise sources randomly triggered in space and time. We found that strong constraints on the spatial distribution of the passive sources were not required to retrieve the time-lapse signal as long as sufficient source-location repeatability was observed between the base and the repeat passive survey. To illustrate the potential of the technique, ANSI was applied to three days of passive field data recorded in 2012 at Ketzin. Comparison with the modeled results illustrated the potential to retrieve key reflection events using ANSI on field data from Ketzin. This study supports the idea that the geologic setting and characteristics of ambient noise at Ketzin may be opportune to monitor CO<inf>2</inf> sequestration. © 2014 Society of Exploration Geophysicists