Seismic characterization and monitoring of a deep CO2 storage reservoir with 3D VSP using direct shear waves

We developed a processing workflow to extract SV-SV and SV-P seismic modes from 3D VSP data acquired over a CO2 storage reservoir at Decatur, Illinois and tested these modes for seismic imaging and monitoring of the reservoir. In addition, we inspected an SH-SH mode that appeared interpretable in our data. We observed that direct-S images were consistent with traditional VSP direct-P images and calibration synthetic seismograms. A joint analysis of all available seismic modes allowed a constrained interpretation of faults within the reservoir. Direct-S waves appeared to not be advantageous for CO2 plume growth monitoring in the Decatur project. The SV-P mode demonstrated low sensitivity to CO2 concentration. The time-lapse difference for the SV-SV mode was uninterpretable due to the low signal-to-noise ratio of that mode.