A time-lapse seismic inversion method based on wavefield reconstruction inversion for the dynamic monitoring model data of geologic CO₂ sequestration

In the monitoring of geologic CO₂ sequestration, time-lapse seismic data can capture the CO₂ injection-induced subtle changes in CO₂ saturation and associated reservoir physical properties, which are crucial for evaluating the storage safety and effectiveness. Although conventional full-waveform inversion can exploit full-waveform information in time-lapse seismic data, it is highly nonlinear and strongly dependent on the initial model and low-frequency components, rendering it prone to cycle skipping. Hence, this study incorporated wavefield reconstruction inversion (WRI) into time-lapse seismic inversion, combined with parallel and double-difference inversion strategies, to establish an inversion process for monitoring geologic CO₂ sequestration. Model test results show that the WRI, based on the parallel inversion strategy, effectively suppressed artifacts while also recovering the geometric morphologies of velocity-change zones. The double-difference inversion strategy further enhanced inversion stability. The WRI, based on the double-difference strategy, accurately captured velocity perturbations in both strong and weak velocity-change zones, yielding significantly reduced artifacts and outperforming conventional methods in both boundary clarity and amplitude recovery. Overall, this inversion method improves the inversion accuracy of the target area while also enhancing the identifiability of reservoir changes, serving as a robust and reliable technical approach for 4D seismic monitoring of geologic CO₂ sequestration.