Investigating Anisotropic Characteristics at the Sleipner CCS Field from Seismic and CSEM Data

For a successful carbon capture and storage (CCS) project, it is crucial to understand the physical properties of the geological layers, which is essential for accurate CO₂ plume monitoring. This study investigates anisotropic characteristics at the Sleipner CO₂ storage site in Norway, utilizing seismic and controlled-source electromagnetic (CSEM) data. First, we employ 2D acoustic anisotropic full-waveform inversion (FWI) on the baseline (1994) and monitoring (2008) seismic datasets to assess significant anisotropic properties within the sandstone storage layer, characterized by interbedded thin mudstone layers. Compared to isotropic FWI results, anisotropic FWI results enhance the detection of P-wave velocity reduction caused by the CO₂ plume, with the inverted anisotropic parameter serving as an additional indicator for the location of the CO₂ plume. Subsequently, we apply 2.5D CSEM inversion to the dataset from 2008, revealing substantial electrical anisotropy indicated by the vertical and horizontal resistivities ratio correlating with CO₂ injection effects. Through this study, we suggest the necessity of considering anisotropy in interpreting seismic data and CSEM data for more accurate monitoring of CO₂ storage sites.