Numerical imaging of sedimentary Basin with velocity change: A case study of CO2 monitoring in the Gunsan Basin, South Korea

Numerical seismic investigations are essential for replicating subsurface conditions with high fidelity. They provide a foundational basis for characterizing reservoir properties, optimizing hydrocarbon exploration, and evaluating the integrity of geological CO 2 storage sites. This study assesses the feasibility of using reverse time migration (RTM) to monitor CO 2 storage in the Gunsan Basin, South Korea, by varying input velocity models based on the seismic field survey data. CO 2 injection induces velocity changes in the storage formation, altering the seismic response. The CO 2 plume geometry becomes distinguishable only when these velocity variations exceed a specific threshold. Since the quantitative velocity change appears continuously, the threshold cannot be determined by a single number, but considering the background velocity of the Gunsan Basin seismic data, it is predicted that a velocity reduction exceeding 150 m/s is required for monitoring. To effectively differentiate CO 2 -related anomalies from background geological structures, horizontal plume extent exceeding 500 m is preferred, while variations in vertical extent are expected to show comparatively high detectability on seismic imaging. These findings suggest that time-lapse seismic imaging using RTM is a viable technique for monitoring CO 2 storage in the Gunsan Basin, provided the injection meets the identified spatial thresholds.