Double-Difference Waveform Inversion with a Modified Total-Variation Regularization Scheme: Application to Time-Lapse Walkaway VSP Data

Abstract:

Quantifying reservoir changes is crucial for safe and long-term geologic carbon storage. We develop a new double-difference waveform inversion method with a modified total-variation regularization scheme to jointly invert time-lapse seismic data for geophysical properties changes in reservoirs/target monitoring regions. Our new method avoids the non-differentiability of the total-variation regularization scheme, and improves the robustness of waveform inversion. We use time-lapse seismic data for joint inversion to reduce inversion artifacts outside target monitoring regions. Two walkaway vertical seismic profiling (VSP) datasets were acquired at the SACROC enhanced-oil-recovery (EOR) field in Texas in 2008 and 2009 for monitoring CO2 injection and migration. We apply our new double-difference waveform inversion method to the SACROC time-lapse VSP datasets. Our joint inversion result reveals a region with seismic-wave velocities lower than the other regions in the reservoir. This velocity decrease is caused by CO2 injection and migration.