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

Wednesday, 17 December 2014
Youzuo Lin and Lianjie Huang, Los Alamos National Laboratory, Los Alamos, NM, United States
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.