The first post‐injection seismic monitor survey at the Ketzin pilot CO₂storage site: results from time‐lapse analysis

Abstract

ABSTRACT The injection of CO 2 at the Ketzin pilot CO 2 storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO 2 was injected into a saline aquifer. A third repeat three‐dimensional seismic survey, serving as the first post‐injection survey, was acquired in 2015, aiming to investigate the recent movement of the injected CO 2 . Consistent with the previous two time‐lapse surveys, a predominantly west–northwest migration of the gaseous CO 2 plume in the up‐dip direction within the reservoir is inferred in this first post‐injection survey. No systematic anomalies are detected through the reservoir overburden. The extent of the CO 2 plume west of the injection site is almost identical to that found in the 2012 second repeat survey (after injection of 61 kt); however, there is a significant decrease in its size east of the injection site. Assessment of the CO 2 plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO 2 dissolution, and CO 2 migration into thin layers, in addition to the effects of ambient noise. Four‐dimensional seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO 2 after the second repeat survey and the CO 2 migrating into thin layers and being dissolved was reached by the time of the first post‐injection survey. In view of the significant uncertainties in CO 2 mass estimation, both patchy and non‐patchy saturation models for the Ketzin site were taken into consideration.