Baseline VSP processing for the Violet Grove CO₂ Injection Site

Marcia L. Couëslan, Donald C. Lawton, Michael J. Jones

Injection of CO₂ for enhanced recovery and sequestration purposes is increasing in Western Canada and around the world. Injected CO₂ must be monitored to in order to track its progress through the reservoir and to ensure that the CO₂ is not leaking out of the reservoir. The Violet Grove project uses time-lapse multicomponent surface and borehole seismic surveys to monitor injected CO₂. The baseline P- and PS-wave VSP data has been processed through to migration using a velocity model that was inverted for anisotropy. The VSP data images reflectors for a radius of about 200 m around the observation well. Both the P- and PS-wave images clearly tie the P-wave surface seismic while displaying improved vertical and lateral resolution over the surface seismic. The tie between the PS-wave surface seismic and PS-wave VSP image is less certain due to the poor quality of the PS-wave surface seismic.

The first monitor survey will be acquired in January 2006 and will be processed with the same parameters as those of the baseline survey. It is expected that the injected CO₂ will cause a decrease in P-wave velocities resulting in increased travel time and increases in reservoir amplitudes on the P-wave images.