A 3D Seismic Traveltime Tomography Study of the Shallow Subsurface at the CO2SINK Project Site, Ketzin, Germany

摘要

3D seismic traveltime tomography is tested at the CO2SINK project site, a small scale storage and monitoring project of CO2 injection into a saline aquifer formation near the town of Ketzin, Germany. The main purpose of this study is to obtain additional information on the inhomogeneous near-surface layers above 150 ms where the 3D reflection seismic image is poor. First arrival traveltimes from a subset of the 3D reflection data were used for this study. We use a 3D traveltime tomography technique based on a combination of solving for 3D velocity structure and static corrections in the inversion process. The resulting velocity model shows low velocities of 800-1000 m/s in the cover of the study area. A velocity contrast of approximately 1600 m/s and 2000 m/s at 60-80 m depth represents the boundary between Quaternary deposits and Tertiary sections. Correlation of the tomographic images with a similarity attribute slice at 150 ms (about 150 m depth) indicates that east-west running fault zones observed in the reflection data may extend into the Tertiary sections. This is shallower than what can be mapped from the reflection seismic images.