Rapid-repeat time-lapse vertical seismic profile imaging of CO2 injection

ABSTRACT In a carbon capture and storage (CCS) project, monitoring CO2 during the injection period is crucial for ensuring the safety and effectiveness of the injection process. The real-time observation of CO2 behavior allows for adjustments to the injection parameters to enhance performance and enables the refinement of the reservoir simulation models to predict plume migration accurately. Achieving this with seismic surveys requires significantly shorter intervals between the surveys compared with the conventional monthly or yearly timescales. This study aims to identify an effective seismic monitoring method, encompassing acquisition design and an imaging technique, for capturing the short-term, dynamic subsurface changes resulting from CO2 injection. We present images generated through elastic full-waveform inversion applied to rapidly repeated time-lapse vertical seismic profile (VSP) field data. The data are acquired using a fixed source shooting across an injection plume at approximately 15 min intervals over several days. These images, created from a combination of sparse geophone data and densely distributed acoustic sensing (DAS) data, provide clear snapshots of transient subsurface changes near the injection well. The results are further validated using a synthetic inversion experiment, demonstrating that the combined geophone and DAS-VSP approach offers a cost-effective and informative monitoring solution for CCS projects.