Geophysical monitoring at the Ketzin pilot site for CO2 storage : New insights into the plume evolution

Abstract To date, 3D time-lapse seismic monitoring at the Ketzin CO 2 storage pilot site comprised a baseline survey conducted in 2005 and two repeat surveys conducted in 2009 and 2012. At the time of the first repeat survey (22–25 kt of CO 2 ), the CO 2 plume was found to be concentrated around the injection well with a maximum lateral extent of approximately 300–400 m and a thickness of 5–20 m. Data from the 2012 survey (61 kt of CO 2 ), show further growth and migration of the amplitude anomaly interpreted to be induced by the CO 2 injection. The anomaly is similar in shape to that obtained from the 2009 survey, but significantly stronger and larger by ∼150 m in the N–S direction and by ∼200 m in the E–W direction. In agreement with the 2009 survey, the new data show a westward propagation of the plume, a trend governed by the complex structure of the reservoir. No evidence of systematic changes in the seismic signature within the overburden is observed. A quantitative assessment of the plume reveals a 15% discrepancy with the injected amount, which could be attributed to the ongoing dissolution processes. However, the estimated quantity also contains significant uncertainty.