The accumulation of CO2 in the atmosphere is considered to be the main reason for the global warming effect. The emissions can be reduced substantially by capturing and storing the CO2. The CO2SINK project was Europe’s first onshore project for the geological storage and monitoring of CO2. This project started operation near the town of Ketzin, Germany in the North East German basin in April 2004 and has continued as the CO2MAN project since April 2010. The main focus of the project was to develop the basis for Carbon Capture and Storage techniques by injecting CO2 and monitoring of CO2 in a saline aquifer in order to develop confidence for future geological storage of CO2 in Europe. In September 2004, a pilot seismic survey was performed in order to determine the necessary parameters for the conduction of a later 3D baseline seismic survey[i].  The pilot survey was performed along two perpendicular profiles near to the CO2 injection site. Pseudo 3D and 2D reflection seismic data were acquired. The results from 2D processing of the data contributed to planning of the 3D baseline survey. In this study the pseudo 3D data from the pilot seismic reflection survey is used to perform 3D processing for the first time. A significant part of the study is the correlation of results with the 3D baseline seismic survey and borehole data. All significant horizons, possible faults and traces of remnant gas were identified. Correlation with the 3D baseline, integration with the borehole data and time/depth contour maps showed good agreement with the 3D baseline survey and well log data. Low fold data, acquisition geometry, time shifts and source generated noise produces severe distortion in the data. Due to these limitations it was difficult to obtain good quality images. Careful processing that involved static corrections and more accurate velocity analysis were the key steps for successful imaging. These results were combined with bore-hole information for an integrated interpretation.

The accumulation of carbon dioxide gas (CO2) in the atmosphere is considered be the main cause of global warming effects. These emissions can be reduced substantially by capturing and storing the CO2. The CO2SINK project started in April 2004 in the northeast German Basin (NEGB) at the town of Ketzin near Berlin, Germany. Uppsala University is one of the main participants in the seismic part of the CO2SINK project. Full waveform sonic data were acquired in the Ktzi-201 injection well at the Ketzin CO2 storage site. The mode of logging was monopole logging. The target was the Stuttgart Formation, a saline sandstone aquifer at the depth of 500-700m. A total of 1210 shots were conducted and data were recorded on 13 channels. Receiver spacing was 6 inches (15.24 cm). The focus of the CO2SINK project was to develop the basis for the CCS technique by injecting CO2 into a saline aquifer and monitoring of the injected CO2 in the aquifer as a pilot study for future geological storage of CO2 in Europe. The objective of this study is to calculate P-wave & S-wave velocities from full waveform sonic data recorded in Ktzi-201 injection well. In hard formations, shear wave velocities can be determined directly from full waveform sonic data recorded in monopole logging. However, in slow formations like Stuttgart Formation as in the Ketzin CO2SINK project, shear wave arrivals are absent in full waveform sonic data recorded in monopole logging. In this case, shear wave velocities can be determined from Stoneley wave velocities provided that one knows the P-wave velocity in the borehole fluid. P-wave velocities were calculated by picking the P-wave arrivals on full waveform sonic data. Due to the absence of shear wave arrivals, the shear wave velocities were estimated from the larger amplitude Stoneley waves. The estimated S-wave velocities from Stoneley waves were less than the fluid wave velocity in the borehole, confirming the mode of logging was monopole and the formation is a slow formation. The reliability of shear wave velocities estimated from Stoneley waves also depends on five other parameters such as formation permeability, borehole fluid property, tool diameter, borehole radius etc.